Ballast Brook and Beaufort Formations (late Tertiary) on Northern Banks Island, Arctic Canada

Pergamon Qt,aernary lnternatiomd, Vol, 22/23, pp, 141 171. 1994.

Copyright © 19t;4 INOUA/Hscvicr Science Ltd. Printed in Great Brilain. All rights reserved.

111411 (~182/~;4 $26.1)1~

BALLAST BROOK AND BEAUFORT FORMATIONS (LATE TERTIARY) ON NORTHERN BANKS ISLAND, ARCTIC CANADA¶

J . G . Fy le s* , L . V . Hi l ls+, J . V . M a t t h e w s , Jr *, R. B a r e n d r e g t $ , J. B a k e r § , E. I rv ing§ a n d H. Je t td* *Geological Survey of Canada, 601 Booth St., Ottawa, Ontario, K1A OES, Canada

+University of Calgary, 2500 University Drive, N.W., Calgary, Alberta, T2N IN4, Canada "-::University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, TIK 3M4, Canada

§Geological Survey ~[' Canada, 9860 W. Saanich Road, Sidney, British Columbia, VSL 4B2, Canada

Excellent exposures of late Tertiary terrestrial sediments occur in the Ballast Brook region of northwestern Banks Island (Canadian Arctic Archipelago). These sediments contain abundant concentrations of organic detritus as well as autochthonous peats which can Ire traced for some kilometres. All of these deposits were previously assigned to the Beaufort Formation. In this paper, the deposits tk)rmerly grouped as the Beaufort Formation are subdivided into two formations: the newly named Ballast Brook Formation and the Beaufort Formation.

The Ballast Brook Formation is characterized by alluvial sand, sill-clay and peat with compressed, altered wood. Paleobotanical evidence indicates an early to mid-Miocene age, with mid-Miocene being the most probable. This formation is believed to overlie the Eureka Sound Group and is in erosional contact with the overlying Beaufort Formation. Plant macrofossils from the Ballast Brook Formation include a number of taxa now found in northern hardwood and southern boreal forests, while the prominent peat which characterizes the tkmnation contains a number of taxa that now grow or could bc expected to grow in a cypress swamp type of environment. For example the conifer Glvptostrohu~ is well represented in the peal.

The Beaufort Formation at Ballast Brook consists of altcrnating sands and gravels, and silt m the lower part. It is characterized by an abundance of unaltered wood and other phmt materials. Palcobotanical evidence indicates an early Pliocene to early late Pliocene age (i.e. approx. 5-3 Ma). Like the Ballast Brook Formation, the Beaufl)rl Formation contains an abundance of |k)ssils of conifers, but in contrast with the Ballast Brook Formation nearly all of them belong to Pinaceac, a group well represented in the present boreal forest. The Beaufort Formation also contains insect fossils, which are very rare in the Ballast Brook Formation. Together, the insect and plant macrofossils suggest an environment similar to, but richer in species (some extinct; others now found only in Asia) than present boreal forest and taiga.

The Ballast Brook Formation flora resembles the flora from Mary Sachs gravel (formerly Beaufort Formation) on southwestern Banks Island and the ttora from the West River beds on the Northwest Territories mainhmd. It also is similar to a 4~Ar/3~Ar dated mid-Miocene flora from east-central Alaska and to the Mamontova Gora (mid-Miocene) flora from Russia.

INTRODUCTION

Wood and other plant remains , in a remarkable state of preservat ion, were discovered in sands on nor thwes te rn Banks Island (Fig. 1, 74°N, 123°W) by explorers in the mid-19th century (Heer , 1868). Abou t a century later, these wood-bear ing sands were assigned to the Beaufor t Format ion (Thors te insson and Tozer , 1962) based on general similarity to the 'type" Beaufor t Format ion in the Mould Bay area of Prince Patrick Island (Tozer , 1956). Subsequent invest igat ion of these Beaufor t sands in the Ballast Brook area on nor thwes te rn Banks Island revealed the presence of distinct ' upper ' and ' lower ' units differing in the degree of al terat ion of plant material (Craig and Fyles, 1965; Hills, 1969), and the assemblage of conta ined plant fossils (Hills, 1975: Matthews, 1987). In a recent review of the Beaufor t Forma t ion as seen from its type area on Prince Patrick Island, Fyles (1990) suggested that only the upper part of the succession exposed at Ballast Brook proper ly belongs in the Beaufor t Format ion (see also Hills and Ogilvie, 1970) and that the lower unit should be set apart under a different format ional

¶Geological Survey of Canada (ontr ibut ion 12393.

name. Agains t this background (and drawing on field invest igat ions at Ballast Brook in 1990) the present paper assigns the name Ballast Brook Format ion to the lower part of the succession, and restricts the Beaufort Format ion to the upper part , and provides new paleontological data for both formations.

METHODS

Field Studies This paper is one product of a 2 wcek re -examina t ion

and re-sampling of Neogene strata (Fig. 2, 3, 4) in the vicinity of Ballast Brook in July 1990 by Fyles, Hills, Matthews and Barendregt . In July 1991, Fyles and Matthews were able to supp lemen t these invest igat ions on a 1 day tour with visitors from Russia.

Fylcs and Hills are largely responsible for docu- ment ing the strat igraphy of the Ballast Brook Forma- t ion type section and the Beaufor t Format ion supple- menta ry section. In addi t ion they have examined numerous other sections in the vicinity in order to de te rmine the regional extent of features observed in the Ballast Brook Format ion .

141

142 J.G. Fvles eta/.

MarmOntova ' z ~

~-~ c n u k o ' t k a ? O

Berin~gg S e ? f ~ ~ " X A l a s k a

Arctic Ocean

Meighen Is.

\ Prince Patrick Is.

Sea"~ Banks is.

Porcupine "- L;anyon

~-~ I WestR. ~. /

~ C ~ ;~' Lost ~ - v , Chicken. ]

/ \.,, \..'(. C a n a d a ",

G r e e n l a //

(

Ballast .. ~ M uuskoxR. Biook ~sal~kn s ~ 72.5 N

Duckh (Mary Sachs gravel) ,

100 km 120°W

FIG. 1. Map showing the Ballast Brook area and other Arctic sites mentioned in the text.

Paleontology Except for wood samples from the Ballast Brook

Formation, which were identified by Jette, Matthews is responsible for the collection and study of plant macrofossils and the parts of the paper dealing with paleobotany and fossil insects. Pollen samples discussed below were studied in part by T. Ager, U.S. Geological Survey and in part by M. Frappier, University of Ottawa. Both used modifications of well known, standard palynological extraction techniques.

Plant macrofossils, comprised mostly of fruits and seeds, conifer leaves and conifer cones, were isolated from sieved fractions, with the smallest mesh opening being 0.45 mm. Time did not allow detailed examination of all fractions, particularly the fine-grained ones. The majority of fossils discussed here were recovered either by examination of the residues that floated on water during initial sample preparation or those remaining on the 1 mm sieve. Identification of the fossils was accomplished by use of various reference collections, comparison with residues from present day cypress swamps in southeastern North America and comparison with illustrations in several monographic treatments of Late Tertiary floras in Europe and Asia.

Paleomagnetic Data Barendregt collected 284 oriented specimens for

paleomagnetic analysis from the type section of the Ballast Brook Formation and the reference section of the Beaufort Formation. Polycarbonyl cylinders of 2.1 cm diameter and 1.8 cm length (6.84 cc volume) were inserted into sections which had been cleaned with shovel and knife. The samples were processed in the laboratory supervised by Irving. Baker did the laboratory work on these samples, and Irving

joined Barendregt in the written discussion of the paleomagnetic results.

The natural remnant magnetizations were measured and were found to have intensities in the orders 10 -3 and 10 4 A/m, well within the range of the spinner magnetometers used. However the internal precisions were generally very low; the specimen precisions (k~,l), as defined by Irving et al. (1985), range typically from 1 (essentially random) to 25. For the instrumentation used, k~,, is typically 102 or 103 for good magnetic field recorders. Pilot specimens were demagnetized in alternating magnetic fields (AF) up to 100 mT. Generally the k~,, decreased as the intensities fell and only rarely were crude end-points attained. The materials clearly are very poor recorders of the paleofield. However, because of the potential stratigraphic importance of the units sampled, and because of the considerable effort and cost of making collections from this remote area, the work was continued to exhaust all possibilities. Therefore all specimens were demagnetized in AFs of 5, 10 and 15 mT and re-measured after each treatment. The records were inspected and specimens whose directions varied erratically, that is by amounts more than 20 ° during demagnetization, were rejected (138 or 49% of the collection). The remaining data obtained after demagnetization at 10 mT were then compiled and specimens with inclinations less than 30 ° were rejected (42 specimens, 29%); this was done because such low inclinations cannot be accepted as indications of polarity in such high latitudes.

The low field magnetic susceptibility was also measured. The magnetic susceptibility is the ratio of the magnetic moment per unit volume to the strength of the applied field. In sediments such as these, the magnetic susceptibility is a measure of magnetite

Late Tcrtiarv Formations in Arctic Canada 143

FIG, 2. (a) Airphoto showing location of Ballast Brook Formation type section (Fig.5) and other sites ment ioned in the text and shown in Figs 6 and 7. (b) Oblique view of type section (#3 in 2a) of the Ballast Brook Formation and the Beaufort Formation supplementary reference section. Tents on skyline (upper arrow) indicate scale. Arrow in upper-middle part of photograph indicates approximate location of site shown in Fig. 2c. Upper arrow in lower right part of photo indicates the location of the rip-up peat block indicated by arrow in Fig. 2d. Lowest arrow in Fig. 2b marks the part of the type section shown in Fig. 2d and c. (c) Ballast Brook Formation and Beaufort Formation at site 3 (type section for Ballast Brook Formation). Unit 4 is the prominent peat seen in Fig. 2b. Arrow indicates approximate position of macrofossil sample 5 (Table 3). (d) Ballast Brook type section and site of measurcd section from fan at the base of the exposure to the top of the dark peat bed (upper arrow). Middle arrow indicates peat block shown in Fig. 3d. Lower arrow marks location of section shown in Fig. 2e. Note geologists for scale. (e) Unit I of the Ballast Brook Formation showing typical alternating clays and thin sands characteristic of this unit. Macrofossil sample I in Table 3 comes from line plant detritus at the

level of the top of the shovcl handle.

1 4 4 .I. ( i. I :v lcs ~'I o/ .

.g FIG. 3. (a) Scction at site 5 (Figs 2a and 6) where thc pcat (arrow) of Unit 4 of the Ballast Brook Formation is intermittent. Thickness of section ahove peat (Beaufort Formation) is approx. 40 m. (b) Large stump in growth position at top of petit of Unit 4 (Ballast Brook Formation). Scale bar = 50 cm. (c) Contacl (arrow and dotted line) of Beanlk~rt Formation and Ballast Brook Formation at site 4 (Figs 2a and 6L At this site woody debris of the Beaufort Formation rests on the compact peat of Unit 4 of the Ballast Brook Formation. Icc axe shown in photo is 80 cm in length. (d) Large hlock of autochthonous peat in Unit 2 of the Ballast Brook Formation at the type section (middle arrow in Fig. 2d). Divisions on ice axe handle: lit cm. The petit of this block is similar (note llattened wood) to petit of Unit 4. (e) ( 'lose-up of part of Unit 4 peat (Ballast Brook Formation), showing the flattened wood fragments and compact character, lhe latlcr which causcs the peat Io stand as a vertical face. Divisions on ice axe handle: l(i cm. (f) Typical planar cross stratification of L!nil 2 of the l{allasl Brook Formation. Trowcl handlc length: I5 cm. (g) Sand with intcrbeds of silty chly in Unit 3 of Ballast Brook

Fornlation, approxinlatcly 2 3 m below base of petit of Unit 4. Scale bar: 50 cm.

[,ate +lertiar~ l ,ormations in Arctic ('an'ad:t 1+15

FIG. 4. Beaufort Formation in the Ballast Brook region. (a) Beaufort strata over the dark peaty unit at the top of the Ballast Brook Formation on the NE wall of the valley of Ballast Brook, downstream (left) from the type section. The pale silty lower beds (arrows), Unit A of the Beaufort Formation, thicken from right to left. (b) Quartzite boulder in Beaufort Formation and surrounded by detrital orga~i.cs, which were studied for macrofossils (sample 7, Table 3). Divisions marked on ice axe handle are 10 cm in length. (c) Upper parl of Beaufort Formation (Unit B) at site 3 (Fig. 2a), showing (arrows) lenses of detrital wood and other organic debris. Note for scale, person on sky line (upper left). (d) Largest in situ log observed in the Beaufort Formation; Unit B, near site 3 (Fig. 2a). Note ice axe for scale. (c) Close up of detrital wood from one of the lenses shown in 4c: arrow points to the base of s tump of a small tree

(approx. 4 cm diameter) with over 120 (annual?) growth rings. Candy wrapper for scale = approx. 15 cm.

present. Magnetite will have been deposited initially as a dctrital mineral. Subsequently, during diagenesis, it can be removed, especially in sediments buried under acidic or reducing conditions. In the present instance, in sediments that contain much carbonaceous material, the magnetic susceptibility is likely to be a measure of the degree of diagcnesis.

LATE TERTIARY DEPOSITS, NW BANKS ISLAND

Late Tertiary sediments are well exposed in many places along the steep walls of river valleys on northwestern Banks Island (Figs 1 to 4). Viewed generally, these exposures consist of fiat lying, unlithi- fled sand, silt, clay and gravel and contain abundant

wood and other plant material. The strata are fluvial and include deposits of both meandering and braided rivers, as well as fine silts, clays and organic sediments believed to have accumulated in floodplain swamps and lakes.

The upper part of the succession is characterized by abundance of remarkably unaltered, uncompressed wood including water-worn sticks and fragments, small detrital trees with branches and roots and even some bark, and bedding-plane mats of line plant material (including twigs with cones). In contrast, plant materials in the lower part of the exposed late Tertiary succession are dark brown, altered and compressed: wood lying parallel to bedding-planes is flattened. In this lower unit, detrital wood in sand is much less abundant than in the upper beds but a distinctive prominent bed of compressed woody peat some 3 m thick is traceable

146 J . G . Fyles et al.

for several kilometres in river bank exposures. Hills (1969) recognized that the two units are separated by an unconformity and differ in mineralogy.

Earlier papers have shown that the late Tertiary sediments on NW Banks Island lie unconformably on various bedrock units, including particularly the Eureka Sound Group of Maastrichtian to Eocene age (Miall, 1979). Vincent (1983) has mapped glacial and non-glacial Quaternary deposits that are superimposed on the late Tertiary sediments. Unfortunately, at the sites discussed in this paper, the base of the late Tertiary succession is not exposed and the top is eroded and covered by thin nondescript fluvial and colluvial deposits.

BALLAST BROOK FORMATION

and some tributary valleys as shown in the airphoto in Fig. 2a. The type section (Fig. 2c) is on the NE wall of the valley of Ballast Brook at a prominent gully 15.5 km upstream from the river mouth at site 3 in Fig. 2a (74 ° 19.6'N; 123 ° 15'W). The exposed section, about 40 m thick, extends from the lowest (clayey) strata (Fig. 2d) exposed at the mouth of the gully to the top of dark brown clay about a metre above the prominent peat bed (Fig. 2b).

The peat (Fig. 2b and c) is the most prominent feature of the formation, being visible from a long distance (Fig. 4a), but at some sites it is intermittent or has been removed by erosion (Figs 3a and 4a).

The bottom of the formation is covered and the top surface is erosional. The authors are not aware of any exposed section of the formation revealing strata extending below or above this stratotype.

The name Ballast Brook Formation is here applied to the lower unit of the late Tertiary sediments, consisting of fiat lying sandy and silty-clayey strata and the prominent bed of compressed peat. This formation is exposed along both walls of the valley of Ballast Brook

Stratigraphic Succession The sequence and character of five units making up

the type section are indicated in Table 1 and Fig. 5. As is evident from the right column of Table 1, the sediments making up the Ballast Brook Formation

TABLE I. Ballast Brook Formation, type section

Total Dcposititmal Unit thickness Material Description environment

5 1.0 m Clay Clay ix massive, brown, apparently organic Lacustrine-distal crevasse splay rich; no macroscopic plant nlatlcr

S H A R P C O N T A ( ' T

4 3.0 m Peat Peat is dark brown, altered, compressed: Back swamp distal crevasse splay consists of plant manor mixcd with sand deposits and silt; contains wood, twigs, needles, leaves, cones. Stumps in growth position mainly in upper part but locally at basc and mid-portiuns. Locally intcrbcdded lenses of sill and clay

3 3.5 m Sand, silt

2 24.7 m Sand

1 6.2 m Clay, sand

G R A D A T I O N A L TO S H A R P ( ' O N T A ( ' T

Alternating beds of sand and silt: silt as beds 0.1-0.3 m thick increasing in number and thickness upward; sand beds avcragc 0.3 m thick, medium-grained, ripple-laminated; top of Unit, I m brown clay with isolated fiat, frequently rounded wood fragments in uppermost few cm

G R A D A T I O N A L CONTAC'F

Coarse to nrcdium-graincd sand to granulc sand; trough cross-bedded throughout; includes pebbly beds, altered wood and ripped-up blocks of compressed peat; rare thin silt beds in lower 6 and upper 9 m

G R A D A T I O N A L C O N T A C T

Coarsening upward sequence: dark grey clay beds 0.2 m thick at base to 0.(12 m at top: sand fine-to-medium grained, mainly ripple-laminated but small planar cross beds at top. minor phmt matcrial

Principally proximal splay deposits grading to lacustrine then to autoehthonous peat of overlying unit

Meandering stream based on sedimentary structures and ripped-up blocks of intraformational peat, indicating destruction of ovcrbank deposits

Crevasse splay into back swamp area

Late Tcrtiary Formations in Arctic Canada 147

12- -

6:5 m b!eakt

?:.'.5"..':'.'.: :." • J

I , ; - ' : " [ . " : ' ; : . : : ' . ~.i!.):.~i...:: ".: .! I w w

, F-V: : :~-i '.

I w w

I - ~ I

~ : : ~

o_i,

: ; I Z :

.=

. , :

" ) . - , @ : .

i

.<, i/~! ',

~-:& : ) : / i ~

6.5mbreal

Beaufort Fm.

u ' }

, ,¢

c

'w w

J

c J

~ p l a n a r . ~ t r o u g h . , ~ 1 sand x-stratified .... I x-stratitiea silt/clay sand ~ sand

~ ripple-laminated B autochthonous ~ Organ c ' sano peat ~ silt an(] c ay

, , ~ blockof wood and 5 macrofossil sample autochthonous w w organicdetritus peat

FIG. 5. Stratigraphic column of the Ballast Brook Formation at the type section. Site numbers/ let ters (bold italics) correspond to

macrofossil samples listed in Table 2.

accumulated on the valley floor of a meandering river system, in channel, overbank, backswamp, and floodplain-pond environments.

Units 1-3 (Fig. 5) comprise a conformable succession of sandy to clayey sediments that are fine at the base (Unit l), coarse in the middle (Unit 2), and fine again in the upper part (Unit 3). Sand is light grey and quartz-rich. Hills (1970) reported that the sand is composed of 70% quartz, 25% chert, and 5% others (shale chips predominantly). Trough cross-bedding and planar cross-bedding are common in Unit 2 (Fig. 3f,

Table 1). Isolated pieces of water-worn, altered wood are distributed through Units 1-3 but substantial quantities of plant material occur only in the sand unit, where altered detrital wood and rip-up blocks of compressed peat are concentrated in sandy, pebbly cross-beds. The peat blocks (in Unit 2) are remarkably similar (both physically and paleontologically) to some of the peat in Unit 4 about 20 m higher in the section. These blocks are considered to be intraformational, although their source-bed has not been seen in place. Unit 3 of the Ballast Brook Formation changes upward from sandy channel sediments to silty and clayey overbank muds (Fig. 3g). Immediately beneath the peat (Unit 4), these muds are dark brown and clay-rich and have the appearance of gleisol.

The peat bed comprising Unit 4 occurs along the walls of Ballast Brook valley and tributary valleys over a distance of at least 15 km. This major accumulation of plant material, together with the immediately underlying dark clay at the top of Unit 3 and the overlying thin organic clay comprising Unit 5, represent a substantial interval of flood-plain pond sedimentation in the fluvial system. The peat is about 3 m thick at the type section (Fig. 2b) and elsewhere, except where the upper part has been removed by erosion subsequent to deposition of the overlying dark clay (Figs 3a, 3c and 7). The peat bed consists of dense, dark brown plant materials mixed with a variable amount of clay- to sand-sized mineral matter. At the type section, two silt/clay beds occur within the peat section. Charcoal is a common constituent; amber is present although not abundant. The peat is compressed by vertical loading. Plant remains include wood, twigs, stems, roots, needles, leaves, cones and finer materials. Wood is dark brown and brittle, and logs and branches lying horizontally are flattened (Figs 3c and c). In contrast, numerous flat wood flakes in the lower part of the peat bed appear to have been split off large diameter trunks prior to burial in the peat. Stumps in growth position and up to a metre in diameter occur in the upper part of the peat within 200 m of the type section. Elsewhere, stumps occur at various levels within the peat bed. Particularly large stumps in growth position (up to 2 m in diameter) are exposed in the stripped upper surface of the peat at a site 10 (Fig. 2a) on the southwest wall of Ballast Brook valley opposite to the type locality. The base of Unit 4 top of Unit 3 is placed at the boundary between clay or silt and peat. In some places the lowest part is fine, and the dark colour of the uppermost clay/silt and the local presence of flat wood flakes in this material suggest transitional boundary conditions. In other places, however, the base of the peat is abrupt.

Unit 5 at the type section consists of about a metre of brown (organic) clay/sih truncated at the top by the erosion surface marking the contact of the Ballast Brook Formation with the overlying Beaufort Formation (Fig. 2c). This clay seems to be in grada- tional contact with the underlying peat, but does not contain visible plant remains.

148 J . G . Fylcs ut al.

Post-Depositional Tilting and Erosion Hills (1969) noted that the individual stratigraphic

units here assigned to the Ballast Brook Formation decrease in elevation from east to west and northwest along Ballast Brook, as illustrated in his Fig. 1. To further demonstrate this slight inclination, the altitude of the peat bed (Unit 4) has been recorded by altimeter at a number of sites spaced over a distance of several kilometres along Ballast Brook. These data show that the peat bed has a westward dip of approximately 6 m per km. This inclination exceeds the down-valley gradient of the present braid-plain of Ballast Brook itself (approximately 4 m per km), and substantially exceeds the original low gradient of the swampy, lake-strewn meander plain on which the peat bed is inferred to have originated.

Post-depositional uplift and erosion have created a substantial unconformity (Hills, 1969) which forms the boundary between the altered, compressed and slightly

tilted Ballast Brook Formation and the horizontal, unaltered sediments of the Beaufort Formation. Thus, within a distance of a few kilometres SE along the NE wall of Ballast Brook valley from the type section, the basal contact of the Beaufort Formation cuts progressively down through Units 5 to 3 of the Ballast Brook Formation and into Unit 2. On the other hand, over a considerable area in the vicinity of the type section, the eroded top contact of the Ballast Brook Formation lies within a stratigraphic interval of only 5 or 6 m, ranging from the upper clay (Unit 5) down through the thick peat (Unit 4, Figs 3a, 3c and 6). This relationship appears to indicate that the dense peat and associated compact clays served as a resistant base for erosion by the rivers that deposited the overlying Beaufort Formation. Further, the contrast between fresh, unaltered, uncompressed wood and other plant material in the Beaufort beds, and the flattened wood and altered plant material characteristic of the Ballast

E LL

0

m

E U_ ,,,t'

0 0

rn

t,n

N o r t h s i d e of B a l l a s t B r o o k 7 km

6 5

4

I' J / .

/

/ ,

/

w 12 1 2 ¸W_ W tu

lOre I WW

3

?W

j f - - J

1

i:iii I I

sand (Beaufort Fm

autochthonous peat

trough x strati,ied sand

Type section ] i silt/clay I

W Wood or detrital organic debris

Blocks of autochthdnous peat

FIG. E3. Correlation of measured sections of the Ballast Brook Formation in the vicinity of the type section. Scc Fig. 2a for site locations.

Late Ter t i a ry Forma t ions in Arct ic Canada 149

site 9 (Kuc and Hills, 1971)

75

~ .W'WI~ W '.1

W W W W W I 5,,

o ; ° 0 0 ° 4 IJ_ , ~ <:3

W W W W W |

o ~.,o ,::1

Bal last 0 Brook F m

sam p. 1 7

s a m p . 1 6

JVM 3-73

JVM 2-73

JVM 1-73

site 8 Bft.

IJ_

£ el3

w w : w I " ~ C~

I

~ 0 ~ ' o

% gravel & ', . cross-stratified mossy pond ~2 i sand i ! sand deposits

i silty clay I I highly organic silt silty sand and/or autoch, peat and silt

~: 7:114 woody zones in sand rip-up blocks of j . . . . . . I sand w w w and gravel and/or ~ autochthonous

detrital peat peat

[:I(L 7. S l ra t ig raph ic sec t ions expos ing the Ballast Brook Format ion and Beaufor t Format ion : site 8 (Fig. 2a) on t r ibu tary nor th ot l},pc sect ion and site g (Fig. 2a) on the nor thwes t side of Ballast

Brook .

Brook Formation (Fig. 3c), points to compression of the Ballast Brook materials by a considerable load of overlying sediment that w'as removed by erosion prior to deposition of the Beaufort Formation. If the age of the Ballast Brook Formation is no younger than middle Miocene, and the overlying Beaufort Formation no older than early Pliocene (see below and Matthews, in preparation), then the unconformity between the Ballast Brook Formation and the Beaufort Formation at Ballast Brook spans at least the late Miocene, and thus represents a minimum of 5 Ma.

The sands of the Ballast Brook Formation arc dominated by well rounded quartz grains which commonly exhibit one or two stages of overgrowth. This would suggest that they had previously undergone at least three cycles of sedimentation. Paleocurrent indicators such as trough cross-stratification indicate sources to the cast. Reworked palynomorphs including both terrestrial and marine taxa indicate that the primary source was late Cretaceous to early Tertiary in age. Combining these three lines of evidence, the Eureka Sound Group which underlies the Ballast Brook Formation and crops out to the east (Thorsteinsson and Tozcr, 1962) was probably the source for much of the formation. Chert, which is also present could have been derived from the same source but may have been derived from Proterozoic sediments on Victoria Island.

Magnetism Generally, Ballast Brook sediments provide no

record of the paleofietd, although sequentially arranged specimens in Units 1 and 5 havc steeply inclined downward directions, indicating that they have normal polarity. Viewed overall, it is not possible to erect a magnetostratigraphy of the formation.

Magnetic susceptibilities of 189 specimens from the Ballast Brook Formation have been measured. A histogram is given in Fig. 8. Thc mean (log) is 5.17 × l(I 5c.g.s.

Paleontology Paleontological information then available for the

strata now included in the Ballast Brook Formation on NW Banks Island was summarized by Hills et al. (1974) and Hills (1975) as follows: 'The lower 40 m has yielded a rich palynoflora dominated by such deciduous genera as Alnus, Bettda. Cao'a, ('ot3'lus, Jttglans and Tilia. Pollen of Picea, Pinlts spp. and Zs'uga dominate . . . conifer pollen with Osmunda and moss spores . . . present in relatively low quantities. Pinus paleodensiflora is the only macrofossil recovered from this interval. The overlying lignite "has yielded Pinus itelmenorum, paleodenstflora and abundant seeds of Menyanthes sp.' (Hills, 1975). Thc subsequent palcobotanical work by Matthews reported in this paper and in Matthcws and Ovcnden (1990) deals mainly with plant macrofossils. This paper also includes

1 0 0 •

75~

o~- 5 0 -

o 25i

E g

~ too 2:1 E c 75

B e a u f o r t F o r m a t i o n

i

n=102

OJ , ~ - 4 8 - 4 ' 4 - 4 0

B a l l a s t B r o o k F o r m a t i o n

I n=189

5 0 ,

2 7

~2 21 . -

> ,

~5 : 14 ~a.

j 8

t _ 4 ~ "

E

c_

c~_ E

40 ~

38 "6

28 E c

2 5 ~

-4 8 - 4 . 4 4 0

I o g l o S u s c e p t i b i l i t y ( S l y . )

18

FIG. 8. C o m p a r i s o n of the magne t i c suscept ib i l i ty of s ed imen t s of tile Bal las t Brook Format ion and the Beaufor t Format ion . The mean (log) for the Beaufor t Fo rma t ion is 1.(} x l(I 4 c.g.s. (1.3 × 10 4 7.7 × I{I 5) and for the Ballast Brook Format ion is 5,2 × IO ~ c.g.s. (8.3 x 10 5-3.2 × ll) "). The l imits g ivcn in bracke ts are s t andard devia t ions . The tv, o popu la t ion means are

s igni l icunt ly di f ferent at the p = {).(11 level.

15() ,I. G. Fyles et al.

brief mention of the results of new palynological work on a very few samples by T. Ager (U.S .G.S . ) and M. Frappier (GSC contract).

Palynology As noted above, the original paleontological char-

acterization of the strata here assigned to the Ballast Brook Formation was based on pollen data (Hills, 1975). The limited newer pollen data set out in Table 2, and discussed below, generally confirm the presence of hardwood pollen in organic samples from Units 2, 3 and 4 (studicd by T. Ager) and a single clay-silt sample from Unit 5 (studied by M. Frappier). Also included in the same table are pollen data (studied by M. Frappier) for eight silt samples (in vertical sequence) from the supplementary reference section of the Beaufort Formation immediately overlying sample

139 from Unit 5 of the Ballast Brook Formation. The lowest of these Beaufort samples (sample 159) is less than a metre above the Unit 5 sample and many of its hardwood constituents are clearly derived from the underlying Ballast Brook Formation. Further evidence of more limited reworking is evident in some of the higher samples. Sample 224 (13 m above the unconformity) is, however, typical of the Beaufort Formation in localities on other islands where the equivalents of the Ballast Brook Formation are not known (e.g. Fyles, 1990, Table 1).

The pollen sample from the clay of Unit 5 has the highest percentage and greatest diversity of hardwood types in samples from the Ballast Brook Formation. The two most abundant taxa are Juglandaccae (most likely Juglans) at 2.5% and Carva at 5.5~{,. The percentage of hardwoods and to some extent their

T A B L t ] 2. Pol len spec t ra from the Bal las t Brook Format ion and the Beaufor t Fo rma t ion

Ballast Brook Formation Beaulbrt Formation

Unit 2 Unit 3 Unit 4 Unit 5 159 171 181 20(~ 215 224 229 252 9(>12 91 3 see be low 139 0 . 3 m 2 m 8 m I I m 12m 1 3 m 1 8 m 2 8 m

x_Pinaccac :~ t'i< ea Pimt.s :1 h ie.~ 7 ~uga t v p . : l.ar/.~ t3p.

+I'("l:i: Betula

( orv/u.~ Sali Misc. hardwtw*ds

II).6 lU.5 15.3 21.4 43.8 36.2 40.2 47.1 45.4 37.3 3S.4 ~1.2 54.8 + ~ + - 1 . 2 24.0 17.5 12.0 15.5 21).4 2().2 2,";.4 14.3 22.2

10,0 It).2 15.3 9.9 9.2 11.9 17.7 18.8 15.6 ,~.N 7.9 32.1 18.0 1.5 + 1.2 1.2 - 1.1 ~ f 1.2

1~+ 2.9 43.4 4.6 4.4 2.S 1.4 t).5 3.3 +

31.1 t~.(~ 6.2-37.1 16.4 3.4 7.7 4.1 3.5 5.9 3.2 5.4 9.1 243) 21.3 4.7-21.1 6.1 25.4 12.2 17.6 20.8 25.1 25.0 15.1 13.4 12.1 21.() 13.6-23.6 9.b; 17.7 21.8 15.5 16.6 14.1 15.5 12.3 11.6

+ + + I.(~ + 2.2 2.3 1.7 1.7 1.1 1.1 1.9 1.2 1.2-8.4 + 1.3 1.9 1.8 1.9 1.9 I 3) + + 1.5 2.4 0 + 9.6 5.() 4.9 + -- +" - +

Pt, U/Z PI, U/Z Pt. C/C, Q.JgC T,C, O.Jg ( ' /0, Ix c/o Ix ,Ig ( 7 ( (7(" Jg ( 7 0 , Jg, Q C , U / Z ,Ig ( '

Ix Ix U /Z . Ix U/Z , Ix Ix M vri~'a + ~- + -2.5 + + + 1.2 ~ 2. l) ~ 1.8 + l:'ricah's t~,p. Ill. t) 9 .2-13.4 2.6 2.9 1.9 1.(~ 2. I l l7 1.5 3.0 1.7 ( i r a m i n c a c k 11,-4.7 + - + + ( ' y p c r a c c a c ~ + 1.2 + + + + + + + + + [ ) l ~ a . ~ ~ +

( ' o m p o s i t a c + Misc. herbs§ + 1.4 + + + - + r + +

(16) (2) (4) (3) (2) (2) (3) (3) Pollcn Sum 338 333 170-325 1140 3713 1347 1121 817 643 620 1252 ~36

S p h a g n u m 6.7 10.0 0-2 .7 3.5 4.4 2.1 8.2 11.9 13.1 13.8 11.3 12.2

.... l 'olal pe r cen t age includes un iden t i t i ed bisaccatc types. ; - lncludcs l~w4ga and 71~uga~7~ollenites type. :i:lnchidcs "l'a_rodium, Juni,~erlts, Thttja, Metasequoia, G137~tostrohu.s. § N u m b e r in pa ren thes i s ind ica tes the number ot taxa ( includes aqua t ic herbs). 4 - pc r ccn t age values less than 1.

Samples : Samples arc a r r anged from lowest in sect ion (left) to highcst , except for Unit 4 which includes pe rccn tagcs o l three samples col lec ted a long same s t ra t ig raph ic hor izon at d i f ferent sites. Percentages shown in first three columns are modi l i cd from counts performed hv T. A g c r (L;.S. Geo log ica l Survey; per.s, c o m m u n . , Dec. 1992). R e m a i n d c r are from samples studied by M. Frapp ie r (Univers i ty ~,1 O t t awa) on cont rac t to the GSC.

9(!-12: 91 3: Llni! 4:

139: 159-229: 252:

l~rom large block of felted peat in sands of Uni t 2 (see macrofoss i ls , sample 12, Table 3). De t r i t a l organic hor izon within Unit 3 a p p r o x i m a t e l y 5.75 m bclow the peat of Unit 4 (see sample 5, Tab le 3). Range of va lues from three samples taken at various local i t ies at base of peat of Uni l 4. ( )nc of them comes fl-om the type sect ion (see sample P, Tab le 3). ('lay of Unit 5, II.5 m below contact with Beaulk)rt Formation. Unit A of the Beaufort Formation (metres above base of Format ion) . I_lnit B of the Beaufort Formation (me t res above base of Forma t ion ) .

H a M w o o d abbrev ia t ions : O = Q u e r e u s . I x=l l ex , P t = P t e r o e a r y a , ( ' = ( ' a r v a . U / Z = U l m u s , ' Z e l k o v a . (7( '=( 'a . s tam, a/('a.slamq)sis" ( ' / 0 = C'a~7)intts/O.wo,a, l g = luelat s, J g = J u g l a n d a c e a c , T = Tilia.

Late Tertiary Formations in Arctic Canada 151

5 1 _

15 ~ : ".'71:.:..".;5"

8~ 20 ::< T.T.:? 32

<

.-- 30 c ~ 0

o , ,

sand KL'~./( x-stratideo x-strathied siltlclay ~ sand sand & sand

magnetic polarity & d l~ sample number ~ wood lenses unconformity I l w l 3 group

(seeTable 6)

F I G . ~). S u p p l e m e n t a r y R e f e r e n c e Sec t i on o f t h e B e a u f o r t F o r m a t i o n at the t y p e s e c t i o n fo r t he Ba l l as t B r o o k F o r m a t i o n . N u m b e r s associated with paleomagnetic polarities are for 'sample groups"

listed in Table 6.

diversity is much lower in the two samples that come from the peat of Unit 4 and the large clasts of similar peat in Unit 2. Both peats are dominated by macrofossils of Metasequoia and Glyptostrobus, which explains the high content of TCT pollen types. Because the peats are autochthonous, their pollen spectra potentially represent a more local, conifer- dominated environment than samples from Units 3 and 5. This may be the explanation for the relatively low percentages of hardwood pollen in the peats.

Plant macrofossils Seeds of Menyanthes mentioned by Hills (1975) come

from a small sample that he and Matthews collected in 1972. A later re-study of this sample by Matthews (Matthews and Ovenden, 1990) showed that instead of Menyanthes most of the seeds represent two extinct (?) forms of Epipremnum, one indistinguishable from E. crassurn, which is now known from a number of

Tertiary sites in Europe and North America (Matthews, in preparation) and a smaller form which possibly represents E. Ornatum. Menyanthes seeds are actually quite rare in the peat (Unit 4). Other macrofossils isolated in the re-study of the 1972 sample include leaves of Larix. Metasequoia and Glyptostrobus, and seeds similar to those of the extinct betulaceous genus, Tubela as well as Decodon and Nymphoides (Matthews and Ovenden, 1990). Samples of the peat and other units collected in 199(I and 1991 have considerably enlarged this known flora of the Ballast Brook Formation. Table 3 presents a list of plants from several levels at the type section (site 3. Fig. 2a) and two nearby sites (8 and 10, Fig. 2a).

Figures 10-13 show SEM micrographs of selected plant fossils from the Ballast Brook Formation. As indicated earlier, the florules from this formation include a greater number of unidentified fossils than is typical of Pliocene floras. Because some of these 'unknowns' may eventually prove valuable for refining our age estimate for the Ballast Brook Formation, they are illustrated in those figures.

Sample 1 in Table 3 comes from Unit 1 (Figs 2e and 5), Its florule is similar in composition to those from other parts of the section, except that it was the only one with seeds of Phyllanthus (Euphorbiaceae) (Fig. 12e). This is only the second fossil record of this genus from the Tertiary of Arctic Canada. The other comes from Mary Sachs gravel at Duck Hawk Bluffs on southern Banks Island (Fig. 1), but it is clearly not the same species as the one from Ballast Brook (e.g. compare Fig. 12e with Figs. 3-7 of Matthews and Ovenden, 1990). Phyllanthus seeds occur in Miocene floras from Russia and Europe. The genus presently has a tropical and subtropical distribution, with the most northern growing forms occurring well south of the Canadian border (Webster, 1970).

Sample 12 (Table 3) is from a re-transported mat of peat in Unit 2. Its florule, though low in diversity, contains many of the same taxa noted from the peat of Unit 4, e.g. Glyptostrobus, Epipremnum crassurn and the Tubela type. Though Metasequoia has not been found in this particular sample, field examination of similar peat blocks from Unit 2 showed they contained Metasequoia leaves and fronds. On the basis of the fossil content alone, these peat blocks appear to represent transported fragments of a pcat similar to that of Unit 4, though clearly they are not from the same peat that makes up Unit 4 because they occur several metres lower in the section.

Sample 5 (Table 3), from a detrital organic horizon in Unit 2, 5.75 m below the lower boundary of the peat of Unit 4 at the type section, has yielded one of the richest florules from the formation. It clearly is similar to the florule from Sample 16 at site 8 (Figs 2a and 7), and on this basis the sediments from which Sample 16 comes are assigned to the Ballast Brook Formation rather than the Beaufort Formation. An outstanding feature of both these florules is their diversity of conifers, including two types of two-needle pine, two types of

152 .I G. Fyles et ul.

TABLE 3. Plant macrofossils from the Ballast Brook and Beaufort Formations:'

Main Ballast Brook Sect. (Site 3)

Ballst Brk. Fm. Beaufort Fm.

l 12 5 P 3 4a 7 73

Site 8

B.grk. B r i m Fro. Fro.

](1 17 9 14

lO Site 9

Beaufor t [:ornlatioll

21 A B

Bryophy ta P te r idophy ta

Salv in iaccae Azolla sp. Sah,im~ sp. ?

Se lagine l laceac Selaginella selaginoides

(1..)Link. S p e r m a t o p h y t a

P inaceac Ahie.~ sp Larix sp + 1.. cf. L. groenlandii

Benn. Pmus (Pinus) undiff. + P. imh'odensillora

Dorof." * P. densi/Iora-resinosa

lypc P. contorta-hank.~iam,

type Pmus (Strobus) undiff. P. itelmem)rum Vassk.** P. subscct. (Tembrae P. subscct. Euslrobi + Pimts 3-needle type Picea sp. + Tsuga sp. l',seudotsuga sp. ?

T a x o d i a c e a e Gh'ptoxtrobus' sp. + Meta.sequoia sp. + faxodium sp

Cuprc s saceae Thuja sp. + .hmiperus sp.

Coni fera les undct. + Spargan iaccac

S /mrgan ium sp. P o t a l n o g e t o n a c e a e

Polamogeton .filffbrmis Pers.

I~otamogeton hupleuroides type

Polamogeton sp. N a i a d a c e a c

Na/a~" sp. Scheuchze r i aeeae

7)'ig/ochin of. T. maritimum L.

A l i s m a t a c c a e Alisma-Sagittaria type l)a/Ha.volzilttH type

G r a m i n c a c (;h'ceria sp.

C y p e r a c c a c Chulmm sp. ( 'are.v spp. + Scirlms sp. '? Scirlm.~ ~alidus type l)ttlichium sp. t-.leocharis sp. R/tvncllospora sp.

A r a c c a c Kpiprenutztm cras,~um

Reid & Reid l: . orllatttl~,l Reid &

Chand . A ran'ires

+ ÷

÷ + + + ÷

÷

+ + ÷

÷ ÷ ÷ + + + ÷ ÷ ÷ + ÷ ÷

+

+ + ÷ + +

÷ + +

+

÷

,)

+

+ + ÷ +

+ + +

?

÷

+ ÷ +

+ +

,) , )

+ +

÷ + +

+ +

÷ ÷

÷ +

+ + + +

÷

+ --

+ +

÷ + 4-

÷ t

÷ + +

+

+

+ +

+ +


1 12 5 TABLE 3. Continued

P 3 4a 7 73 16 17 9 14 21 A B C

A. globosa E. & M Reid (Bcnn,)

Aracispermum sp. ? Z i n g i b e r a c e a

Spirematospermum wetzleri (Heer)

C h a n d l e r S a u r u r a c e a e

Saururus sp. + S a l i c a c e a c

Sally sp. + Polmho s 0.

M v r i c a c c a e Mvrica {(;ale)

eogale t ype + Mvrica sp. + ('omptonia sp. ? + ('. of. ( . peregrina B & B, Small

J u g l a n d a c c a e (}enus? +

B e t u l a e e a e Ahm,~ sp. + ,-tlnus (Alnobetula) sp. + ? ,4. crislm Ait. Ahtu,s incana t ype + Betula sp. Belula apoda t ype + Bemla popultblia type Betula a r b o r e a l type Tuhehl type + + +

M(~raceac Morus sp.

P o l y g o n a e e a c f'olygonutn sp. Rttmex sp.

C h c n o p o d i a c e a e G e n u s ? Chenol?odium sp.

C a r ~ o p h y l l a c e a e G e n u s ?

N y m p h a e c c a e Nuphar sp. Nymphaea sp.

R a n u n c u l a c e a e Ra~lt#tCltllts sceleratus k. R. hyperboreus Rottb. R. lapponicus L. '? Ranttnclthls spp,

M a g n o l i a c e a e Liriodendron sp, +

C a p p a r i d a c c a e ('leome sp Polani,sia of. P. sibirica

Nikit. + D r o s e r a c e a e

Aldrovamla sp. + + S a x i f r a g a c e a e

Mitella sp. + H a m a m e l i d a c e a e ? + R o s a e e a c

Physocarpus sp. Potenlilla sp. + P~m'ntilla palustris t'. norvegica L. P?IlIllt~ sp. Rttbus sp. + R. idaeus L.

E u p h o r b i a c e a e Phyllanthus sp. +

R h a m n a c e a e of. Paliurus +

V e r b e n i a c e a e Verbena sp.

H y p e r i c a c c a e ttypericum sp.

V i o l a c c a c V;ola sp.

+ + + +

+ + + +

+ ? ? +

+ +

+

+ + +

cf. + +

+ +

of. +

÷ ÷

+

+

cf.

+

+

+

+

÷

+

+

+ +

+ + +

cf.

+

+

+

of.

+

+

+

÷

+

+

+

÷ ÷

+

+

+ ÷

cf, of.

+

154

1 12 5

J. G. Fylcs et al.

T A B L E 3. Continued P 3 4a 7 73 16 17 9 14 21 A B C

Lythraceae Decodon gihbosus type +

1). ,~lobosu,~ type + +

Microdil,,tera parva C h a n d l e r

Mb:'rodil~lera:Mneme type + +

Mclastomaceae Nigrella sp. +

t t ippuridaccac t t ippuris sp.

Araliaccac +

A r,lia sp. +

('ornaccac (cv'm~.,i canaden,',i,'; type +

( . vtolm~/~,ra type Ericaceac

A n dromeda poli/olia L. + ("hamaedal~tme sp.

l:pi,q, aea sp. '~

Zemdmt sp. +

Oleaccae G e n u s ?

Gentianaceae :~h'nvanthe,~ triloliata L. + + MenVaHlhe,~ (<2 i t ln l ) + Nvmld~oide.'; sp. '?

SolHn[ICCaC I'h v,sali.s sp

[,abiatau L vcolmV sp. l"emrium sp. +

(':lprifoliaccac Dierl ' i l la sp. + Sambucus sp. + +

Weige/a sp. +

Vitmrmmz ( 'ompositae

l~iden~ sp. l~iden,~ cernua type

+ + + + -+. + ; + + + +

+

+ +

+ + + + + +

+ ? ?

of. -+. of. 9 + +

+ + + + + + +

+

+

+

+ + + + + + +

+ + + + +

+ + + +

+

+ + + +

?

+ +

"All fossils were identified by JVM except for those marked with **, which were identificd by LVH. I - Ballast Brook Formation; Site 3-type section: MRA 7-17-91-1: fine dctrital organics in clay and silt of Unit 1 at type section. 12 Ballast Brook Formation: Site 3-type section; MRA 6-26-90 12: rebcddcd mat of pcat in the sands of Unit 2, approximately

1[ m above the base of the section at type section. 5 : 13allast Brook Formation; Site 3-type section; MRA 6 26-90-5; MRA 7 17-91-2; MRA 7 17-tH-3: Organic debris within sands

of Unit 2 approximately 5.75 m below the main peat of Unit 4 at the type section. I ' - 13allast Brook Formation; Site 3-type section; pooled fl~ssils from main peat (Unit 4) at sections near the type section (Site 3,

fig. 2a) (updated from Matthews and Ovendcn, 1990). 3 Beaufort Formation: Site 1; MRA 6-25 90-3; organic debris within the Beaufort Fro. at Ballast Brook, approximately 22.5 m

above the top of the peat of Unit 4 of the Ballast Brook Formation at a site (section 2 in Fig. 6) approximately I km from lhc Beaufort Formation reference section.

4a I~eaufint Formation: Site 1; VH 9(b-O4a: autochthonous peat associated with oxidized and cemented horizon at a site (section 2 in Fig. 6) approximately 4{1 m above the top of the peat of Unit 4 of the Ballast Brook Formation.

7:- Beaufort Formation; Northwest of site 1; MRA 7-17-91-7; detrital organics associated with large houldcr in the uppermost part of the Beaufort t:ormation (see Fig. 4b).

73 Bcaufi~rt Formation: Site 9; JVM 74 73; organic debris approximately I0 m below lop of section at approxinmte location of the supplementary reference section.

10 Ballast Brook Formatian; Site 8; F G 9(! 16a: mat of detrital organics within fine sands approximately 17 m below the Icvcl of highly organic sediments of sample 17.

17 Ballast Brook Formation; Site g; FG 90-17a: organic silt with wood; Organic horizon thought to bc the equivalent of the peat ;rod associated sediments of Unit 4 at the type section.

9 Beaufort Formation; Site 8; MRA 6-29-90-9: detrital organics; approximately Ill m above the organic silts of sample 17 and contacl with Ballast Brook Formation.

14 Beaufort Formation; Site 8; F G 90-14a; dctrital organic bed; approximately 29 m above the level ol sample 17 and contact with Ballast Brook Formation.

2 1 - Ballast Brook Formation: FG 90 -2hu peal correlative with peat of Unit 4 at a site (Site I0. Fig. 2a) across Ballast Brook valley ( 1.5 kin) from the Ballast Brook Formation type section.

A Bcaufort Formation; Site 9 (Figs 2a and 7): JVM 73-1, approximately I0 m above peat of U n i t 4 (BMlasl Brook Formation) and 02 in below peaty deposits studied by Kuc and Hills (1971).

B - t3canfort Formation: Site 9 (Figs 2a and 7); JVM 73-2, approximately 23 m above pcat of Unit 4 ([}allasl Brook Formation) and 51 in below peaty deposits studied by Kuc and Hills (1971}.

(7: Beaul\~rt Formation; Site 9 (Figs 2a and 7); JVM 73-3, approximately 31 m above peat of Unit 4 (Ballast Brook Formation) and 41 in below peaty deposits studied by Kuc and Hills (1971).


FIG. 10. SEM micrographs of plant macrofossils from the Ballast Brook Formation. Scale bar = 0.5 mm. (a) Decodon gibbosus type (Lythraceae), seed; GSC-108832; Photo #41852; sample 5, Table 3; ventral view showing the relatively broad seed compared to Decodon globosus type (Matthews and Ovenden, 1990, Fig. 4-8). (b) Decodon gibbosus type (Lythraceae), seed; GSC-108833; Photo #43105; sample 5, Table 3: cross-section, ventral side and germination valve to left; shows embryo cavity with large zone of spongy tissue (right) containing raphe. (c) Polanisia cf. P. sibirica Nikitin (Capparidaceae), seed; GSC-108834; Photo #41917; sample 5, Table 3. (d) Pseudotsuga sp. (Pinaceae), cross-section of a needle GSC-108835; Photo #41905; sample 5, Table 3; note the dorsal sulcus; large resin canals in contact with the epidermis and the presence of only a single vascular bundle, a combination of characters that is unique to Pseudotsuga (Durrell, 1916). (e) Microdiptera/Mneme type (Lythraceae), cross-section of seed, germination valve (ventral) at top; GSC-108836; Photo #419(/7; sample 5, Table 3; note that the lateral lobes have two prominent furrows on the dorsal side, making this form different from that found in the Mary Sachs gravel at Duck Hawk Bluffs (Matthews, in preparation) and suggesting that the seed is more similar to Mneme type than to Microdiptera type. Other characters, e.g. the number of rows of pits on the germination

valve (not evident in micrograph) are of type seen in Microdiptera.

f ive-needle pine, Pseudotsuga (Fig. 10d), Taxodium, Metasequoia and Glyptostrobus. Tempera t e hardwoods

such as Liriodendron and Morus also cont r ibute to the ~ancient' character of the sediments at both sites. Both Liriodendron and Morus have also been found in the Mary Sachs gravel at Duck Hawk Bluffs on southern Banks Island (Fig. 1 and Mat thews, in preparation). Like the Mary Sachs gravel flora, samples 5 and 16 also conta in two types of Decodon, Dulichium, Microdiptera/Mneme, Diervilla, and cf. Paliurus. One taxon in samples 1 and 5, not found at Duck Hawk Bluffs but never theless present in the West River flora

(Fig. 1) and a dated Mid-Miocene flora from the upper Porcupine River (Alaska) is Aldrovanda (Fig. 12b) (Mat thews and O v e n d e n , 1990).

Seeds here referred to Microdiptera/Mneme type occur at Ballast Brook and Duck Hawk Bluffs. They are rare in the Beaufor t Forma t ion and occur only in contexts where rebedding is probable . Tiffney (1981) and Friis (1985) discuss the problems of applying a name to these lythraceous seeds. A cross-section of one of the seeds is shown in Fig. 10e. The presence of p r omi ne n t furrows on the dorsal side and the sculpture on the ge rmina t ion valve, shows that it

156 J .G. Fyles et al.

FIG. 11. SEM micrographs of plant macrofossils from the Ballast Brook Formation. Scale bar = 0.5 mm. (a) Juniperus sp. (Cupressaceae), leaf fragment: GSC-108837; Photo #43153; sample 5, Table 3. (b) Genus? Oleaceae?, fruit?; GSC-108838; Photo #41665; Sample 16, Table 3, site 8 (Figs 2a and 7). Similar to specimen identified as 'Oleaceae, genus undet.' in Fig. ll) of M~idler (1939). (c) Unknown, fruit (?), (Juglandaceae?); GSC-108839; Photo #43102; Sample 5, Table 3. note y-shaped seam (arrow). (d) Tubela type (Betulaceae); nutlet?; GSC 108840: Photo #43082; Sample P, Table 3 (near type section): note the absence of well developed wings. Arrow indicates base of style. (el Epigaea? (Ericaceae), seed; GSC-108841; Photo #43076; sample 5, Table 3; enlarged views show detail of wall and surface, upper right (Photo #43077): Close up of the surface, showing the pitted (punctures) on the bottom of the luma as well as on

the sides of the walls. Lower right (Photo #43129): Close up of wall section. Note that the wall (arrow) is unitegmic.

shares charac te r s of both Microdiptera and Mneme, hence the des igna t ion 'Microdiptera/Mneme type ' . A single fossil f rom the Beaufor t F o r m a t i o n , p r o b a b l y r e b e d d e d f rom o lde r depos i t s (see be low) , is very s imilar to the species Microdiptera parva Chand le r . The Bal las t B r o o k F o r m a t i o n fossils may also r ep re sen t this var iab le species , but until more de ta i l ed s tudies are car r ied out we opt for the more conserva t ive 'Microdiptera/Mneme' des igna t ion . A l t h o u g h some of the species that fit into this b r o a d ca tegory have been found in E u r o p e a n and As ian floras as young as the Pl iocene (Tiffney, 1981), such fossils are def ini te ly not

typical of Pl iocene floras from the Nor th A m e r i c a n

Arc t i c (Mat thews , in preparation). A single megaspo re of Azolla (Fig. 12a) was found

in the res idues f rom sample 5. W e canno t rule out the poss ibi l i ty that this fossil is r e b e d d e d f rom sed iments o lde r than the Bal las t B r o o k Fo rma t ion . On the o the r hand , s imi lar forms have been r e p o r t e d f rom the Miocene in S iber ia (D oro fe e v , 1963). Because the m i n i m u m sieve size used for process ing samples is larger than Azolla megaspo re size, the find in sample 5 is def ini te ly for tu i tous .

Two types of Decodon seeds occur in late Te r t i a ry


F1G. 12. SEM micrographs of plant macrofossils from the Ballast Brook Formation at Ballast Brook. Scale bar = 0.5 ram. (a) Azolla sp. (Salviniaceae), megaspore; GSC-108842; Photo #41658; Sample 5, Table 3. (b) Aldrovanda sp. (Droseraceae), seed; GSC-108843; Photo #43098; sample 5, Table 3; micropylar end at bottom. Note the presence of slightly pointed chalaza and a suggestion of the longitudinal ridge that marks the raphe. Right hand image (Photo #43099) shows the characteristic pattern of the shiny black epidermal surface. (c) Pinus densiflora/resinosa type. (Pinaceae), oblique cross-section of a needle; GSC-108844; Photo #41641; sample 5, Table 3. At least one of the resin canals is in contact with the epidermis, hence "external' (Harlow, 193l) while others are 'medial'. The various characters displayed in this cross-section (semi-circular shape, round endodermal region, large resin canals of which some are external, the close proximity of the vascular bundles) are found in both the modern species Pinus resinosa and P. densiflora (Harlow, 193l). (d) Unknown (Hamamelidaceae?), fragment of seed; GSC-108845; Photo #43086; sample 5, Table 3. Arrow marks boundary between smooth and roughened surface that is typical of the seeds of some genera of Hamamelidaceae. (el Phyllanthus sp. (Euphorbiaceae),

seed; GSC-1(18846: Photo #41957; sample l, Table 3.

deposits in the Arctic. Decodon globosus type is present in both Miocene (?) and Pliocene deposits. The D.

gibbosus type (Fig. 10a and b) seems to be restricted to older sites, the only other record being from 40Ar/~')Ar dated mid-Miocene deposits on the Porcupine River in Alaska (Matthews, in preparation; Fouch et al., this volume) . The D. gibbosus type has never been found in the Beaufor t Format ion .

Paral lel ing the presence of a variety of hardwood t~ollen types in some parts of the Ballast Brook

Format ion , is the presence of a few hardwood macro-

fossils, such as the seeds of the tulip tree, Liriodendron. At the present t ime in Canada Liriodendron only grows in the Niagara Forest Region along the nor th shore of Lake Onta r io (Rowe, 1972). Many of its hardwood associates are ones whose pollen occurs at low frequencies in the Ballast Brook Format ion . Liriodendron is one of several hardwood genera that current ly have single species in east Asia and eas tern North Amer ica . Parks and Wende l (199(I) suggest that

158 J .G. Fyles et al.

FIG. 13. SEM micrographs of plant macrofossils from the Ballast Brook Formation (except d, from Beaufort Formation). Scale bar = 0.5 mm. (a) Epipremnum crassum Reid and Reid (Araceae), seed; GSC-108847; Photo #41841; sample P, Table 3 (near type section). Shows the presence of the black, scabrous covering found only on the best preserved seeds. (b) Epipremnum of. E. ornatum Reid and Chandler (Araceae), seed; GSC-108848; Photo #43094; sample 16, Table 3; site 8, Fig. 7; arrows indicate pits (position of former raphide sacs) which are characteristic of this species. (c) Glyptostrobus sp. (Taxodiaceae), leaf fragment of the cupressaceous form; GSC-108849; Photo #41925; sample P, Table 3 (near type section). (d) Spirematospermum wetzleri (Heer) Chandler (Zingiberaceae), seed (external and internal views of the same seed); GSC-108850; Photo #41675 (external) and #41718 (internal); sample 3, Beaufort Formation, Table 3. Inset (Photo #41663) shows magnified view of the characteristic surface sculpture of the seeds of this species. (e)

Zenobia sp. (Ericaceae), seed; GSC-108851; Photo #41904; sample 5, Tablc 3.

these two species have been i so la ted for 10-15 Ma. Because no physical ba r r i e r s e p a r a t e d As ia and Nor th A m e r i c a dur ing the Miocene , when tul ip t rees were growing on Banks Is land , they p r o b a b l y occur red across the Ber ing Land Br idge into east As ia : i .e. they had an Hola rc t i c d i s t r ibu t ion .

The pea t of Uni t 4 is one of the most obvious fea tures of the Bal las t B r o o k F o r m a t i o n . H o w e v e r , its pea ty cha rac te r and high degree of compress ion m a k e s it more difficult to i sola te p lant macrofoss i l s f rom this unit than f rom the de t r i t a l organics of Uni t 3, for

example . This means that the t axonomic divers i ty of Uni t 4 (Tab le 3) is u n d e r - r e p r e s e n t e d and cer ta in ly not r ep resen ta t ive of the t rue divers i ty of the p lants which grew in the pa luda l e n v i r o n m e n t that even tua l ly gave rise to the pea t .

Mats of the delicate deciduous shoots of Glyptostrobus,

a few including cones , occur sporad ica l ly at the base of Uni t 4. On ly small G l y p t o s t r o b u s leaf f ragments , like those shown in Fig. 13c, occur in the s ieved samples . The occur rence of s imilar leaf f r agments in the organic silt of sample 17 at site 8 poin ts to co r re la t ion of that


site with the Ballast Brook Formation rather than the Beaufort Formation.

Clusters of Epipremnum crassum seeds occur at the base of Unit 4 at some localities. The seeds are generally excellently preserved, with most of them possessing the scaly testa that is rarely seen on fossils that have been transported and deposited in alluvium. The clusters probably mark the actual growing site of this extinct plant, and, if so, indicate that E. crassum was a member of the same paludal community in which Glyptostrobus once grew. A smaller form of Epipremnum seed also occurs in Unit 4. For the time being we cannot refer this form to any of the other named species of Epipremnum, but it is about the same size as Epipremnum ornatum (Fig. 13b), a single seed of which was found in the silts of sample 16 from the Ballast Brook Formation at site 8 (Fig. 7). The scaly testa found on Unit 4 specimens may obscure the pits (position of former raphide sacs) which are characteristic of E. ornatum and which can be seen in the illustration of E. ornatum (Fig. 13b).

The fossils referring to Tubela (Fig. 1 ld) from Unit 4 are puzzling. They are similar to illustrations of Tubela in Friis (1985) and Takhtajan (1982). As with some of the specimens shown in Takhtajan, fossils like the one in Fig. 1 ld possess a sheath which completely encloses an alder-like nut. Some of the nuts arc very similar to the ones previously referred (Matthews, 1987) to Alnus tertiaria type, based on their similarity to A.

tertiaria Dorofeev, from the Oligocene of western Siberia (Dorofeev, 1963). At Ballast Brook, Tubela- type fossils occur only in the Ballast Brook Formation and almost only in the peat of Unit 4. This probably means that the plant, whatever its affinities, grew at poorly drained sites.

An autochthonous deposit like Unit 4 is likely to exhibit considerable lateral variation in floral content. This is illustrated by the rare occurrence of concentrations of E. crassurn seeds mentioned above. One sample from the base of the peat at the type section was dominated by Larix needles, though it also contained the typical Ballast Brook Formation cohorts: Glyptostrobus, Metasequoia, Epipremnum crassum, Tubela type etc. Some of the five-needle pine leaves from this particular site have external resin canals, proving that the Eustrobi type white pines (Critchfield, 1986) were growing locally. Some levels within the peat are dominated by two- or five-needle pine fascicles. Some of the complete fascicles have leaves that are more than 10 cm in length.

The two-needle leaf fragments may be from the same trees that yielded cones identified as P. paleodensiflora by Hills (1975). The five-needle fragments may be from P. itelmenorum, cones of which Hills (1975) also reported from the peat of Unit 4. Note that Hills (1975) also lists cones of P. paleodensiflora from the Ballast Brook Formation below the peat of Unit 4. In Table 3 we show that some samples from this part of the

T A B L E 4. Identified wood from the Ballast Brook Formation

Sample # Unit Identity* Comment

M R A 7-1-91>2 4 Picea sp. Type section: base of Unit 4

M R A 7 2 90 1 4 I'inus strobus grp. Type section: wood fragments within the peat of Unit 4

MRA 6 2(~91) 3 4 I'intts strobus grp. Type section; s tump in growth position at the top of Unit 4

M RA ('>29 90 -2 (# I ) 2 Pinus strohus grp. Type section; approximately 10-12 m above base of exposure

MRA 6-29-91>2(#3) 2 Pinus strohus grp. Type section: approximately 10-12 m above base of exposure

M RA 6-29-90-2(#4) 2 Pinu,s strobus grp. Type section; approximately 10 12 m above base of exposurc

MRA 6-29-90-2(#5) 2 Pinus strohus grp. Type section; approximately 10-12 m above base of exposure

MRA 7 3-91>4 4 Picea sp. Gully just west of type section: upright s tump approx. 15 cm in diameter, in peat, 120 cm above base of Unit 4.

MRA 0-28-90-3(#6) 4 I'icea sp.

M R A 6-28-9() 3(#3) 4 Sequoia/Memsequoia

MRA 6-28-9(>3(# 11 ) 4 Sequoia/Metasequoia

Base of Unit 4: approximately I km northwest of site 1 (Fig. 2a)

Base of Unit 4; approximately 1 km northwest of site 1 (Fig. 2a)

Base of Unit 4; approximately 1 k m northwest of site I (Fig. 2a)

*ldentilied by H.J.

160 J .G. Fyles el al.

exposure contained needle fragments of a two-needle form similar to P. resinosa and P. densiflora (Fig. 12c). These leaf fragments may come from the same tree species as the P. paleodensiflora cones.

Sample 21 (Fig. 2a; Table 3; locality 10) comes from the peat unit (Unit 4) on the SW side of Ballast Brook valley opposite the type section. It contains an assemblage of fossils similar to that at the type section, except that the dominant pine is a three-needle species. Needles of this kind were not seen at the type section. Site 10 is also characterized by numerous strongly tapered stumps up to 2 m in diameter at the level of the roots.

Fossil wood Previously published wood identifications from Ballast

Brook (Roy and Hills, 1972) all come from the Beaufort Formation as defined here, so they have no bearing on the Ballast Brook flora. Wood samples (identified by H.J.) from a number of levels within the Ballast Brook Formation are listed in Table 4. Note the presence of taxodiaceous wood, a type not reported from the Beaufort Formation (Roy and Hills, 1972). Wood fragments or stumps that are not compressed have relatively thick growth rings, another distinction from Beaufort Formation wood (see below).

Other fossils Very few insect fragments were seen in sediments of

the Ballast Brook Formation. The only recognizable fragments seen thus far represent one or more unknown genera of small weevils (Curculionidae). Despite an intensive search, no vertebrate fossils were discoverd in the Ballast Brook Formation.

Age and Correlation Thc best available evidence for dating the Ballast

Brook Formation is its macroflora. It contains plants in common with the 40Ar/39Ar dated 15.2 Ma flora from the Ramparts site on the Porcupine River in Alaska (Kunk et al., this volume; White and Ager, this volume) and is also quite similar to the macroflora from the Mary Sachs gravel (formerly known as Beaufort Formation) on southern Banks Island (Fig. 1) and to the flora from the West River beds on the northern Canadian mainland (Fig. 1).

The Ballast Brook Formation macroflora is clearly differem from and more ancient than the flora of the Pliocene Beaufort Formation. This is best seen in Table 5, which compares the North American Arctic and Greenland occurrences of selected plant taxa. The table shows that the Ballast Brook Formation and similar deposits on southern Banks Island and the northern mainland lack taxa normally associated with taiga or tundra environments. The Beaufort Formation floras and the late Pliocene Kap K0benhavn flora lack many of the temperate herbs, shrubs and trees seen in the Ballast Brook flora. Like mid-Miocene floras from Asia, nearly 60% of the taxa in the Ballast Brook flora are not now found in northern regions

and 10% are extinct (Matthews, in preparation). For the Beaufort Formation at Ballast Brook 31% are non- native and 6'/0 extinct (Matthews, in preparation). Such distinctions suggest that a considerable amount of time elapsed between deposition of the two formations, a conclusion also suggested by the angular unconformity between them.

A few of the plants from the Ballast Brook Formation allow a more precise estimate of its minimum age. The most important of these are Metasequoia and Taxodium. In east Asia, Metasequoia last appears in the upper Miocene; Taxodium no later than mid- Miocene (Nikitin, 1979a), while in the Alaskan Cook Inlet area, the youngest records of Metasequoia date to about 10 Ma (Wolfe and Tanai, 1980; J .A. Wolfe, pers. commun., 1992).

Estimation of a maximum age for the Ballast Brook Formation involves determining the First Appearance Datum (FAD) for a number of its constituent taxa. But this is a difficult task because not all authors cite the same FAD, they mention the FAD for only a specific region, or the FAD is based on unfounded and different estimates of the age of critical floras. Table 5 represents an at tempt to derive the FAD of a number of key plants from the Ballast Brook Formation. It shows that the earliest record of many of the taxa in Europe and Asia is late Oligocene. The starred entries (Metasequoia, Diervilla, Glyptostrobus, Taxodium, Larix, Pseudotsuga, 7kuga and Picea) are taxa found in Eocene deposits on Axel Heiberg Island in the Canadian Arctic Archipelago (Basinger, 1991; LePage and Basinger, 1991; Obst et al., 1991), hence are of little value for defining the maximum age estimate for the Ballast Brook Formation. Only a few of the taxa have a Miocene FAD. The most that can be concluded from inspection of Table 5 is that the Ballast Brook Formation is definitely younger than the Late Oligocene.

In the absence of an independent means of dating the deposits, the next best approach would be to compare the Ballast Brook flora with the floras from other dated sites. One such site, the Upper Ramparts of the Porcupine River, has a 4°Ar/-~Ar age of 15.2 Ma (Fouch et al., this volume). Its macroflora is somewhat similar to the Ballast Brook flora, but this may not imply age equivalence because the sites have a wide latitudinal separation. For example, it is conceivable that a late Oligocene flora at 70°N would resemble a mid-Miocene flora at 60°N. On the other hand, 15.2 Ma approximately coincides with the climate opt imum of the Neogene (Wolfe and Poore, 1982), and the Ballast Brook flora, Mary Sachs and West River floras as well as the Upper Ramparts Canyon flora from somewhat further south (White and Ager, this w)lume) all represent remarkably warm high latitude cl imates--exact ly what would be expected during the Neogene optimum.

Many of the plant taxa from the Ballast Brook Formation, Mary Sachs gravel and West River beds also occur in well studied floras from Asia, such


TABLE 5. Comparison of macrofl)ssil floras from Canadian Arctic and N. Greenland-',-

FADS

mid-Miocene?

N.W.T. S. N. Banks Island Prince mainland Banks Ballast Brook Patrick

Island region Island

Ptiocenc

Meighen Island§

N, Greenland

West Mary Ballast Bfort. Bfl)rt. Bfort. R. Sachs Brook Fro. Fm. Fm.a

beds gravel Fm.

Bfort. Fm.b

K.K. Fm.

Taxa apparently restricted to the Miocene in | Arctic N. Amcrica

I Actinidia LEo;, + + Phyllanthus Olg b + + Metasequoia :~ + + + ( + ) Liriodendron K ~' + + Diervilla ~' + + Pinus (3-needle) * ? + + Pseudotsuga " + Aldrovanda LEo:, + + Taxodium * + + Glyptostrohus ~: + + Decodon sect. gibbosus LEo ~ + Z~uga * + + + ( + ) Polanisia Olg b + + Microdiptera/Mneme M Eo c + + + ( + ) ( + )

Weigela Olg" ? + + + + t typericum Olg ~, + + + + + Sambucus Eo" + + + + + of. Paliuru.s ?LMio~ + + + + Ch'ome Olg b + + + Aralia Olg;' + + + + + Verbena UPlio I + + + Decodon sect. globosus OIg ~ + + + + Betula apoda type OIg d + + + + + Abies Eo? h + + + + + Epipremnum crassurn Olg" + + ( + ) + Comptonia K" + + + + + Pinus 5-needle + + + + + Chenopodium Mio k + + + ]rjluj a :~ + + + +

Myrica eogale type Mio k + + + +

Taxa apparently restricted to the Pliocenc in Arctic N. America

Temperate Herbs, Shrubs and Trees

+ + + + + +

Records in () arc probably rebedded from older beds. +Based on data presented in Matthews (in preparation) and Bennike (1990) and authorities cited under FAD column. §Bfort. Fm. a=Beaufor t Formation sediments below marine (muddy) beds (Fyles et al., 1991) on Meighen Is.; Bfort. Fm. b=combined

fossils from a number of florulcs from the Beaufort Formation overlying marine (muddy) beds on Meighen lshmd. IIK.K. F m . = K a p Kobenhavn Formation, northern Greenland (Bennike, 1990). +FAD=First appearance datum. *indicates taxa known from the Paleogenc Geodetic Hills site on Axel Hcibcrg Ishmd (Basinger,

1991).

Abbreviations: L E o = L a t e Eocene: MEo=Midd le Eocene; Eo=Eocene : Olg=Oligocene: K=Cretaceous: Mio=Miocene: LMio=Late Miocene; MMio=Midd le Mioccne.

Authorit ies: a=Fri is , 1985: b=Dorofeev , 1963: c=Tiffney, 1981; d=Dorofeev , 1969; e=Fri is , 1979: f=Lancucka-Srodoniowa, 1966; g=Mat thews , in preparation: h=Lamot te , 1952; i=Mai , 1964; j=Mai and Walther, 1988; k=Baranova et al., 1976: l=Kirchheimer , 1957.

Potentilla OIg k + + + + + + + + Rumex Mio ~ + + + + + + Gramineac + + + + + + P&'ea * + + + + + + + + Menvanthes OIg b + + + + + + + + Lari.~ * + + + + + + + +

Physocarpus Olgi + + +

Taiga/Tundra Herbs, Shrubs and Trees Bemla dwarf shrub type + + + + + Oxyria + + + + Dcvas + + + + Empetrum MMioc + + + +

162 J.G. Fyles et al.

as Mamontova Gora and several sites in Chukotka (Matthews, in preparation), suggesting similarity in age. The Mamontova Gora flora as well as some other Russian floras are commonly referred to the middle Miocene, but to our knowledge no radiometric dates exist to support such a conclusion. The age assessment of these sites is based largely on the composition of the floras, just as is the case for the Ballast Brook Formation. Furthermore, there is disagreement on the age of some of the key Russian sites. Zubakov and Borzenkova (1990) depart from conventional practice and place the Mamontova Gora flora in the second major warm interval of the Miocene (13 Ma or latest Seldovian/earliest Homerian (Wolfe, 1981), rather than the first at approximately 16 Ma (middle Seldovian).

In light of all the arguments and facts presented above, the best estimate for the age of the Ballast Brook Formation is middle Miocene, as originally suggested by Hills (1975); though it could be as old as early Miocene, even late Oligocene. White and Ager (this volume) believe that the presence of Juglans macrofossils in the Mary Sachs gravel means that unit is correlative with a discrete middle Miocene zone in offshore deposits in the Beaufort-Mackenzie Basin. Juglans macrofossils have not been found in the Ballast Brook Formation, but those of Liriodendron, or tulip tree, have, and in North America tulip tree grows in about the same type of climate as Juglans. Both taxa occur in the Mary Sachs gravel (Matthews, in preparation). For purposes of correlation, we consider Liriodendron as a proxy for Juglans; consequently the presence of Liriodendron macrofossils at Ballast Brook also suggests correlation with the middle Miocene in the Beaufort-Mackenzie Basin.

Paleoecologic and Tectonic Implications We have already noted that presence of macrofossils

of Liriodendron must imply a relatively warm climate, even if the fossils represent an extinct species with somewhat different climatic tolerances than its modern counterparts. A similar argument could be made on the basis of some of the other taxa, such as Phyllanthus and Saururus, both genera that now barely extend as far north as southern Canada.

According to the Ballast Brook flora, the conifer Glyptostrobus grew at swampy sites in the Canadian Arctic as late as the Neogene. As is the case for Metasequoia, the single extant species of Glyptostrobus is restricted to China (van Gelderen and van Hoey Smith, 1986). Both were widely distributed in the late Tertiary (Wolfe, 1977; Czeczott, 1959; Nikitin, 1979b), extending far into the Arctic regions (Basinger, 1991). The Ballast Brook flora records the latest occurrences of Glyptostrobus and Metasequoia discovered so far in the Canadian Arctic.

Glyptostrobus represents an example of the danger of relying on the present habitat requirements of the species within the genus as representative of its past autecology. In the Miocene of Europe, Glyptostrobus appears to have been, as it was at Ballast Brook, a

member of a peat swamp community, whereas starting in the Pliocene and continuing to the present it is more characteristic of stream-side plant communities (Boulter et al., 1993). The high latitudinal location of the peat swamp at Ballast Brook may explain the absence of certain plants found commonly in such deposits (coal seams) in the European Miocene as well as the greater diversity of Pinaceae in the Unit 4 peat.

In addition to a diversity of conifers (e.g. Taxodium, two-, three- and five-needle pines, larch and possibly Metasequoia), the wetland and riparian communities in the Ballast Brook area were habitat for herbs and forbes such as Epipremnum crassum, Decodon, Potamogeton, Sparganium, Hypericum, Saururus. All of these taxa now grow in and around Taxodium swamps in southeastern U.S.A.; however, we caution against a one-to-one comparison. As indicated above, the Banks Island peat swamps and adjacent habitats supported Picea and Larix that are now absent or rare in the cypress swamps of the southeastern U.S.A., and one conifer--Pseudotsuga--which is presently found in only in western North America. Pollen spectra from the Ballast Brook Formation also contain a greater amount of non-TCT conifer pollen than mid-Miocene sites further south (T. Ager, pers. commun. 1992): probably also a latitudinal effect. Thus, when macrofossils and microfossils from Unit 4 are studied in detail they show that the similarity between the Banks Island mid-Miocene peat swamp and those occurring further south is superficial. The Banks Island flora actually has no exact contemporary analogs.

As indicated above and in Fig. 4a, Unit 4 peat can be traced along much of the bluff bordering Ballast Brook. The peat currently has a westward dip greater than the relatively steep gradient of modern Ballast Brook. This is evidence in itself for post-depositional tilting because even under a much warmer climate, the swamps responsible for the peat could n.ot have formed in a fluvial regime like that of the present, much less one with a steeper regional gradient. Instead the peat implies sluggish, low gradient streams and extensive back swamp areas.

BEAUFORT FORMATION, NORTHERN BANKS ISLAND

The name Beaufort Formation has been used for three decades on northern Banks Island for sandy, unlithified wood-bearing strata of late Tertiary age. Formal use of the name Ballast Brook Formation in this report, for sediments earlier described as 'lower Beaufort ' (Hills, 1969; Fyles, 1990), necessitates some further identification of those late Tertiary sediments that are still included in the Beaufort Formation. These 'upper Beaufort ' beds on NW Banks Island are described in earlier papers (references cited by Fyles, 1990) as being strongly similar in terms of lithostratigraphy and paleontology to the Beaufort


Formation in its type area on Prince Patrick Island. In the Ballast Brook area the Beaufort Formation is up to 80 m thick and consists of fluvial sand and gravel, in places interbedded with silt, containing much unaltered, uncompressed wood.

Supplementary Reference Section Silty and clayey strata are particularly prominent in

the lower part of the Beaufort Formation on the part of the NE wall of Ballast Brook directly above the type section of the Ballast Brook Formation (and along the exposed face NW of that site). These strata form a distinct basal light colored zone, thickening downstream as seen in distant views of the bluffs on the NE side of Ballast Brook (Fig. 4a). To record the occurrence of this lithological variant of the Beaufort Formation in juxtaposition to the Ballast Brook Formation (Fig. 2c), the succession of Beaufort strata above the type section of the Ballast Brook Formation is here designated as a supplementary reference section of the Beaufort Formation. It should be noted that the lower, silty part of this Beaufort section is Unit E of Hills (1969) which he originally grouped with the underlying strata (i.e. Ballast Brook Formation of the present report).

As illustrated in Fig. 9, this supplementary reference section of the Beaufort Formation is 36 m thick. It rests unconformably on the dark brown clay that forms Unit 5 of the Ballast Brook Formation (Fig. 2c), though at some sites the contact is with Units 4, 3 or 2 of the Ballast Brook Formation. As noted earlier, the unconformity undoubtedly represents substantial erosion and a long interval of time. The angular relationship between the inclined Ballast Brook strata and the horizontal Beaufort strata records an additional (substantial) interval of time between deposition of the two formations.

The Beaufort section consists of gravel, sand, silt (including clayey silt), and accumulations of detrital plant material. The section is arbitrarily divided into a lower silt-sand unit (Unit A) and an upper gravel-sand unit (Unit B) with prominent lenses of wood (see below): silty beds make up about one- third of Unit A but are rare in Unit B. Throughout both units, sand is medium to coarse grained, well sorted, and quartz-rich. According to Hills (1970) the sand is 50% quartz, 35-40% chert, and 10-15% other materials--predominantly shale. Much of the sand and gravel displays large-scale trough-type cross- bedding although some sand beds have tabular cross- stratification. Ripple-bedded and planar laminated sands are less common. Gravel is a conspicuous component and ranges from beds dominated by pebbles and cobbles to sand containing isolated pebbles. Clasts are up to 12 cm in diameter, sub-round to round, and consist mainly of quartzite, chert, sandstone and fine resistant sedimentary rock types. Igneous and metamorphic rock types are absent. Figure 4b illustrates the unusual occurrence of a quartzite boulder (see below).

The material described as silt is dark blue-grey

when wet, pale grey when dry, and consists of silt- and clay-size material. These silt beds are generally massive but some display indistinct horizontal stratification or alternating thin layers of sand and silt. Silt beds and groups of silt beds (Fig. 9) commonly are laterally continuous over several metres.

The basal strata of the Beaufort Formation at the supplementary reference section characteristically consist of horizontal or cross-bedded sand or gravel and, at nearby sites, enclose isolated cobbles or boulders or pieces of unaltered, uncompressed wood-- thus differing markedly from the immediately underlying dense clay and peat of the Ballast Brook Formation. In a few places, however, water transported fragments of compressed peat or wood derived from Unit 4 of the Ballast Brook Formation have been recognized in basal beds of the Beaufort Formation.

Unaltered and uncompressed wood and other plant materials are present throughout the Beaufort Forma- tion at Ballast Brook. They are particularly abundant in the gravel-sand unit where wood lenses and plant detritus mats constitute distinct sedimentological facies similar to those described by Devaney (1991) on Prince Patrick Island. Individual trees up to 50 cm in diameter (Fig. 4d), logs and broken or water-worn pieces of wood lie parallel to bedding planes in sand and gravel, and less commonly in silt. Wood lenses are particularly prominent in trough-cross-bedded sand and sandy gravel (Fig. 4c). Spruce cones are common, particularly in wood lenses. Although all the plant materials in the Beaufort beds at the supplementary reference section are water-transported, some components appear to have grown nearby. For instance, some trees still have limbs and roots intact, some bear remnants of bark, or have 'pockets' of growth soil still attached to bark between roots. Autochthonous plant remains have not been recorded in the Beaufort Formation at the reference section, but occur elsewhere as noted in the following discussion.

The Beaufort Formation in the Region At other sites in the vicinity of Ballast Brook

visited in 1990, the Beaufort Formation (sensu stricto) consists mainly of cross-bedded fluvial gravel and sand, locally accompanied by beds of silt, and containing much unaltered and uncompressed wood, much of it exhibiting evidence of very slow growth (Matthews, in preparation) as well as other plant fossils characteristic of coniferous forest vegetation.

Another exposure of the Beaufort Formation, at site 9 (Fig. 2a) on the SW side of Ballast Brook, has received detailed study (Kuc and Hills, 1971). The section in Fig. 7, differs from the stratigraphy presented in Kuc and Hills (1971) in two significant ways: (1) the 'lower' Beaufort unit recognized by Kuc and Hills is here assigned to the Ballast Brook Formation, and (2) the cross-stratified sand shown capping a highly organic silt and autochthonous peat is shown as part of the Beaufort Formation or the upper unit of Kuc and Hills, rather than as the upper part of the lower

164 J . G . Fylcs et al.

unit. The cross-stratified sand and overlying silty-clay, which extend to just below the 25 m level, are probably equivalent to Unit A of the Beaufort Formation at the Supplementary Reference Section (Fig. 9).

A few hundred metres up-valley (SE) from the supplementary reference section, the lower, silty, Unit A of the Beaufort Formation is replaced by dominantly sandy and gravelly strata with prominent and abundant wood. Figure 3c at section 4 (Fig. 2a) shows gravel containing uncompressed wood at the base of the Beaufort section, directly overlying the eroded upper surface of the peat bed (Unit 4) at the top of the Ballast Brook Formation.

Down valley from the supplementary reference section, near section 1 in Fig. 2a, a quartzite boulder occurs in the upper part of the Beaufort section (Fig. 4b). This boulder is nearly half a metre in diameter and is enclosed in fine sand mixed with fine plant remains. Similar quartzite boulders have been recorded on or below the eroded face of the Beaufort Formation, but this is the only in situ occurrence.

Source and Depositional Environments" Channel orientation, cross stratification and miner-

alogy imply that this formation was derived from the cast. Abundant multicolored quartzite and chert clasts, suggest that the Proterozoic units on Victoria Island and the Upper Devonian strata on eastern Banks Island (Thorsteinsson and Tozer, 1962) were the source of much of this unit.

Two fluvial depositional environments can be recognized within the Beaufort Formation on NW Banks Island: sandy-braided and gravelly-braided. The sandy-braided deposits are dominated by cross stratified to ripple laminated medium to coarse grained sand with local pebble lenses at the base of channel scours. The gravelly-braided deposits are characterized by abundant cut and fill structures, channels ranging from 2-3 m in depth and from 5-20 m in width. Gravels may be clast supported or matrix supported. Wood lenses are common within this facies. Logs and elongated wood fragments show a strong preferred orientation of the long axis perpendicular to or parallel to the paleocurrent direction as indicated by trough cross- stratification and orientation within channels. The wood material was thus transported as bed load in final stages prior to deposition. Similar sedimentological conclusions were reached for the Beaufort Formation on Prince Patrick Island by Devaney (1991) except that the sandy-braided deposits dominate at that locale.

Magnetism One hundred and forty-six paleomagnetism samples

were collected from eight of the finer grained beds in the Beaufort Formation at the supplementary reference section (see Fig. 9 for location of sample clusters). When compiled stratigraphically, the polarity of six out of eight of the units sampled in the Beaufort Formation could be defined with an acceptable degree of confidence (Table 6); i.e. units in which a sequence

T A B L E 6. Magnetic polarity of samples from the Beaufort Formation at the supplementary reference section:'

Number/Sample polarity Sample Unit group n Normal-;- Reversed+ polarity

21~ 111 0 4 R 19 13 5 II N 18 8 4 II N 17 7 0 ~1 16 23 0 (I I5 9 3 (I N 14 I0 II 9 R 13 9 ~1 4 R

::The position (height) of each numbered sample-group is shown on Fig. 9.

i ' -To ta l number of samples used in polarity dcsignatinn (remaining samples provide incoherent magnetization or yielded inclinations which remained consistently less than 3(I degrees).

n - N u m b e r of samples collected.

of three or more samplcs have the same polarity. Samples from the remaining sampled units (16 and 17, Table 6) exhibited neither normal nor reversed polarity. On the basis of the consistent data, there appears to be a change from reversed polarity at the base, to normal polarity in the middle, and reversed polarity towards the top, thus implying existence of at least two reversals (Fig. 9).

Magnetic susceptibility measured on 102 specimens yielded the histogram of Fig. 8 and a mean (log) of 1.0 × 1(I 4 c.g.s, units. The values for the Beaufort Formation arc about half an order of magnitude greater than in the Ballast Brook Formation. This difference is statistically highly significant, and indicates that the Ballast Brook Formation has much less magnetite than the Beaufort Formation. The magnetite content of the Ballast Brook Formation was either initially very low or has since been removed during diagenesis and with it all record of the paleofield.

Paleontology

Palynology Table 2 presents pollen data from a few samples in

the lower part of the Beaufort Formation at Ballast Brook. All of the samples come from silty zones originally collected for magnetic analyses.

Although further study is required, there are several differences between the spectra in the Ballast Brook and Beaufort Formations that may have biostratigraphic and/or paleoenvironmental significance. Miscel- laneous hardwood types are rarer and Corylus has slightly higher frequencies in the Beaufort Formation than the Ballast Brook Formation. Drya~ and Compositae occur only in the Beaufort Formation (Table 2). Except for the uppermost sample in the Ballast Brook Formation, Picea appears to be more common in the Beaufort Formation. Tsuga is in general more abundant in the Beaufort Formation, with an unusually high frequency in the basal sample. Although no macrofossils of Tsuga were found in Beaufort sediments at Ballast Brook,

Late Tcrtiary Formations in Arclic Canada 165

a few Tsuga needles occur in Beaufort sediments on Prince Patrick Island (Matthews et al., 1990). We believe that this fact and the high pollen frequencies at Ballast Brook mean that Tsuga was growing on northern Banks Island during deposition of at least the lower part (Unit A) of the Beaufort Formation.

A scan of Table 2 reveals a number of similarities in spectra from the Ballast Brook and Beaufort Formations. These may be deceiving. For example, we know from macrofossils that most of the TCT-type pollen from the Ballast Brook Formation represents Glyptostrobus, Metasequoia, Thuja and Taxodium, while TCT in the Beaufort Formation is most likely entirely from Thuja. Similarly, though percentages of Betula and Alnus arc comparable in both formations, macrofossils indicate that different species are involved in each case.

Plant macrq/bssils The abundant, well preserved and varied plant

materials and associated insect fossils in the Beaufort Formation at Ballast Brook supplement similar records from other Beaufort sites on the Arctic Islands in documenting the environment and climate of this region at the end of the Tertiary. The Ballast Brook area that is the subject of this report was the locus of early paleontological investigations by Hills and associates. For instance, locality 9 (Fig. 2a) is the type locality, based on cones, for Picea banksii, (Hills and Ogilvie. 197(I). Thus, Hills (1975), referring to the strata assigned in the present report to the Beaufort Formation, reports that the "upper 36 m is dominated throughout bv Picea banks& but cones of Pinus itehnenorurn, Pinus cf. funebris, and Larix cf. omoloica are also present'. Well preserved mosses were also identified from one horizon at the exposure (Kuc and Hills, 1971) (Fig, 7). The following notes on plant macrofossfls and insect fossils provide supplementary information arising from study by JVM of samples collected in 1971 at site 9 and in 1990 and 1991 at various sites near the Ballast Brook Formation type section and the Beaufort Formation supplementary reference section.

The lowest macrofossil sample from the Beaufort Formation in the vicinity of the reference section (sample 3, Table 3) comes from approximately 22 m above the contact with the Ballast Brook Formation. The florule from this sample contains several unusual taxa, such as Betula apoda-type and two types of Bidens (bur-marigold). The latter genus is a member of the family Compositae, and even though the Compositae existed during the Miocene, neither the Ballast Brook Formation nor any of the other presumed middle Miocene deposits in Arctic/Subarctic North America have yielded macrofossils of Compositae (see Tables 2 and 3). Rare Compositae pollen occurs in a sample approximately 11 m lower in the Beaufort Formation than sample 3 (Table 2).

The most unusual plant macrofossil from sample 3 is a single seed of Spirernato,spermum wetzeleri (Fig. 13d),

an extinct genus and species thought to belong to the ginger family (Zingiberaceae). The only other record of this genus from North America is from the Paleocene (Manchester and Kress, 1933). S. wetzeleri is common in the Miocene of Europe where it is usually associated with Glyptostrobus in coal and lignites that originated as peat swamps (Boulter et al., 1993). It persisted as a relict in the Rhine Basin until the early Pliocene (Zagwijn, 199(/). If this distinctive plant grew as far north as Banks Island during deposition of the Beaufort Formation, then it almost certainly means that parts of the Beaufort Formation are no younger than early Pliocenc.

On the other hand, seeds of S. wetzeleri are very indurate and buoyant, making them ideal candidates for redeposition from older units. The most obvious source, based on European occurrences, would be the peat of Unit 4 of the Ballast Brook Formation, but none were found there. This may be a sampling error, because as indicated earlier, fossil recovery from the peat was hampered by its compact character. For the present, all that can be said is that discovery of S. wetzeleri in the Canadian high Arctic from deposits as young as the Ncogene is a surprise. It will be interesting to see if Spirematospernlum is eventually identified from Paleogene terrestrial deposits, such as those at Geodetic Hills on Axel Heiberg Island (Basinger, 1991).

Seeds of Cleome also occur in Sample 3 as in most samples from the Beaufort Formation, especially those from Site 9 (Table 3, samples 9 and 14). Today Cleome grows as far north as central Alberta and one species is found in the Canadian Rocky Mountains (Iltis, 1957). A few Cleome seeds have been found in the Mary Sachs gravel Matthcws, in preparation), but Cleome has not been recorded from the Ballast Brook Formation.

One of the samples from Site 9 (Fig. 2a) contained a single seed of the Microdiptera/Mneme type. It is identical to forms identified from the Brandon Lignite as Microdiptera parva, a species which ranges in age (in Europe and Asia) from Oligocene to Miocene (Tiffney, 1981). It is also similar to some of the seeds seen in the Mary Sachs gravel and Ballast Brook Formation. The fossil is probably rebedded from the Ballast Brook Formation. as we suspect for Spirematospermum wetzeleri. Such obvious examples of rebedded fossils warn that there may be other fossils in the Beaufort florules that are not so readily identified as spurious.

While most of the organic deposits of the Beaufort Formation at Ballast Brook and elsewhcrc arc alloch- thonous (Matthews et al., 199(I), two autochthonous deposits have been found in the Ballast Brook area. One of these is the mossy sand studied by Kuc and Hills (1971) from locality 9 (Figs 2a and 7). Another is a partly cemented restricted layer of peat near the top of the Beaufort Formation at locality 2 (Fig. 2a). It is represented by the florule of sample 4a in Table 3. This peat differs in several ways from the peat of Unit 4 in the Ballast Brook Formation: (I) it is less compact

166 ,I. G. Fyles et al.

and the wood in it is not compressed; (2) mosses are abundant; and (3) the five-needle pine fascicles found on the bedding planes have much shorter needles than those found in Unit 4. Furthermore they represent one of the subsection Cembrae-type pines that have medial resin canals, whereas in the Ballast Brook Formation most of the Strobus-type pine needles have 'external resin canals', the norm for pines in subsection Eustrobi.

Among the fossils in the 4a florule are well preserved shoots and cones of Larix. The cones have moderately long bracts and are superficially similar to the cones described as Larix groenlandii Benn, from the 2-2.5 Ma Kap KObenhavn Formation on northern Greenland (Bennikc, 1990). Similar larch cones occur in the 3 Ma Lost Chicken site in Alaska (Matthews et al., in preparation). Most, if not all of the Larix needles and wood found in the Beaufort Formation on northern Banks Island probably represent this extinct (?) species. This may also be true of cones that Hills (1975) referred to l,arix cf. ornoloica.

Both Shorn (this volume) and Miller and Ping (this volume) discuss studies of fossil larch cones from Neogene age deposits in the North American Arctic, but until such time as the cones mentioned here are studied by these experts, there will continue to be uncertainty about their identity and relationship to other species. Nevertheless, it is reasonably clear, as Bennike (1990) has shown, that the moderately long-bracted Larix cones from the upper part of the Beaufort Formation at Ballast Brook and other late Tertiary sites in northwestern North America do not represent any of the current North American species.

The large quartzite clast shown in Fig. 4b overlies and is draped by beds of organic detritus. These yield a typical Beaufort type florule (sample 7, Table 3), including even such taxa as Cleome and bracts similar to those of the modern gray birch (B. populifolia). One anomaly is that Physalis, a taxon not previously found in the Beaufort Formation, is also present. Although Physalis has not, however, been recorded from the Ballast Brook Formation, it does occur in Miocene deposits such as Mary Sachs gravel and the West River beds (Matthews and Ovenden, 1990; Matthews, in preparation) and thus might be rebedded. The presence of Physalis might mean either that the Beaufort Formation on northern Banks Island is slightly older than at sites further north (assuming a late Tertiary cooling trend), as it almost certainly is if the Spirematospermum fossil belongs with the Beaufort Formation, or that Physalis simply reflects a slightly warmer climate than contemporaneous sites further to the north.

As is evident from the foregoing, the strata enclosing the boulder are palentologically characteristic of the Beaufort Formation and carry no suggestion of glacial conditions. The surface of the boulder is smooth and water worn, and bears no striae or other surface markings pointing to glacial transportation. The boulder is inferred to have been dropped into the enclosing

fine, fluvial, plant-bearing sediments from floating river ice.

Sample 73 (Table 3) from a locality near the reference section may be stratigraphically higher than sample 4a. Unlike all other Beaufort Formation florules in the vicinity, it contains only rare pine fossils. The dominant conifer is Picea and many of the other plant macrofossils (e.g. Potentilla norvegica type and Ranunculus sceleratus) are seldom seen in other Beaufort Formation florules. A preliminary study of fossils from the highest detrital organic horizon at the supplementary reference section also reveals an impoverished florule compared to those from lower in the sequence.

As indicated earlier, wood from the Beaufort Forma- tion is not flattened like wood from the Ballast Brook Formation. Most Beaufort Formation wood also displays evidence of extremely slow growth. Two small stumps from the Beaufort Formation, neither of them more than 5 cm in diameter (Fig. 4e), represent trees that appear to have been approximately 100 years old when they died. Even the largest stumps from the Beaufort Formation (Fig. 4d) possess very narrow annual rings. Growth-ring thickness on cross-sections of 18 stumps from the woody horizons in Unit B (Fig. 4c) range from 0.3-1.4 mm (mean 0.66 mm) (Matthews, in preparation), which is similar to growth rates of fossil wood from the Beaufort Formation on Meighen Island (Matthews et al., in preparation). These rates are also similar to values obtained from slow growing conifers at modern tree line (Kay, 1978). Though comparable studies of ring widths in Ballast Brook Formation have not been carried out, our casual observations suggest that trees contemporaneous with the Ballast Brook Formation grew much faster and under much warmer climate conditions than was the case during deposition of the Beaufort Formation.

Insects and other arthropods The Beaufort Formation differs from the Ballast

Brook Formation in another way: it has yielded a variety of insect fossils, most of them from beetles (Coleoptera). All of the fossils listed in Table 7 come from site 9 (Fig. 2a) because it was only there that samples of sufficiently large w)lume to yield insects were collected.

Most of the insect taxa in Table 7 were listed elsewhere by Matthews (1977), though in that publication fossils from all three samples were pooled. Table 7 shows the faunal composition of each of the individual samples (Fig. 7). Most of the fossils come from one sample collected from the Beaufort Formation approximately 30 m above the contact with the Ballast Brook Formation.

Fossils referred to Asaphidion cf. yukonense probably represent an extinct species closely related to the nominal extant species. Fragments of another species intermediate between A. yukonense and the Ballast Brook form occur at the 3 Ma Lost Chicken Mine in Alaska (Matthews et al., in preparation). Lost

Late Tertiary Formations in Arctic Canada

T A B L E 7. Insects and Other Arthropods Beaufort Formation, Ballast Brook site 9*

167

Beaufort FM. Site 9

Sample J V M - 1-73 2-73 3-73 Sample J V M - 1-73

Beaufort FM. Site 9

2-73 3-73

B R Y O Z O A Stenus sp. Cristatella mucedo L. + Tachinus sp.

A R T H R O P O D A Micropeplidae INSECTA Micropeplus hoogendorni Matth. C O L E O P T E R A Micropeplus hopkinsi Matth.

Trachypachidae Micropeplus sculptus Lec. Trachypaehus sp. + Micropeplus sp.

Carabidae Silphidae Asaphidion alaskanum Wick. + Silpha sp. Asaphidion cf. yukonense Wick. + Leiodidae Bembidion ( Plataphodes) sp. + Agathidium sp. Bemhidion balli-foveum type + Scydmaenidae Bembidion levettei Csy. + Genus'? Bembidion nitidum Kirby Byrrhidae Carabus spp. + Genus? Chlaenius sp. + Cucujidae Diacheila sp. A + + cf. Leptophloeus sp. Dvschirius cf. D. laevifasciatus Horn + Latbridiidae Dyschirius tridentatus group + Genus? Dvschirius sp. + Curculionidae Elaphrus cf. E. clairvillei Kby. + Apion sp. Elaphrus lapponicus Gyll. ? Cleoninae Elaphrus sp. + Hylobius sp. Notiophilus cf. N. aeneus Hbst. + type B Pterostichus ( L yperopherus ) sp. + Genus? costate Pterostichus (Cryobius) spp. '~ Scolytidae Tachvta cf. T. angulata Casey + Carphoborus sp. Trechus sp. + Genus?

Gyrinidae D I P T E R A Gyrinus sp. + Xylopbagidae

Staphylinidae Xylophagus sp. Euaesthetus sp. + Family? Gymmnusa sp. +

+ +

+ + + +

+

+

+

+

+

+

c.f. +

1-73 Beaufort Formation, Site 9; See Figs 2a and 7. Detrital organic debris from base of cross-bedded sand and silty-sand. 2-73 Beaufort Formation, Site 9; See Figs 2a and 7. Detrital organics. 3-73 Beaufort Formation, Site 9; See Figs 2a and 7. Detritarl peaty zone.

Chicken species differs in a number of character states than the one from the Beaufort Formation at Ballast Brook. Although there are various ways to explain such differences, one is that all three species are members of the same lineage, and that the Beaufort Formation species is the most primitive of the three. If true, this would imply that the lower part of the Beaufort Formation at site 9 (Figs 2a and 7) is older than 3 Ma.

Age Fyles (1990) recommended assignment of the upper

unit (sensu Hills, 1969) at Ballast Brook to the Beaufort Formation because of the similarity of the strata and enclosed plant fossils to those characteristic of the Beaufort Formation in its type area on Prince Patrick Island. The same logic favors the conclusion that the Beaufort Formation on Meighen Island is approximately the same age as Beaufort deposits at Prince Patrick Island and on northern Banks Island. Though such similarities are not evidence of exact age equivalency, they are probably valid in a general sense, and if so they suggest Beaufort deposits on northern Banks Island are no younger than about 3 Ma (early late Pliocene) because that is the age of a marine facies of the Beaufort Formation on Meighen Island (Fyles et al., 1991; Matthews et al., in preparation). However , it should be noted that a few of the insect and plant

fossils from the Beaufort beds at Ballast Brook could be interpreted to signify an early Pliocene minimum age.

Estimation of the maximum age of the Beaufort beds at Ballast Brook depends on the validity of two assumptions: (1) that floras of approximately the same age and from sites at the same latitude should be similar, especially in arctic regions, and (2) that the composit ion of the Beaufort Formation floras is well enough known at most sites to allow arguments based on negative evidence, such as the absence of certain plant taxa. The Beaufort flora at Ballast Brook lacks several important plant taxa that are present at both Alaskan and Russian Mio/Pliocene sites. This suggests to us that Beaufort floras, including the ones from the exposure at Ballast Brook, are younger than late Miocene.

Taking into account all biostratigraphic and paleomagnetic evidence, we conclude that the Beaufort Formation at Ballast Brook could represent an extended interval of time ranging from no older than earliest Pliocene (about 5 Ma) to no younger than early late Pliocene (about 3 Ma).

Paleoenvironments Environmental implications of plant and insect

fossils in the Beaufort Formation (sensu stricto) at Ballast Brook have been discussed in several previous publications (Hills and Ogilvie, 1970; Kuc and Hills,

168 J.G. Fyles et al.

1971; Hills, 1975; Matthews, 1977; Matthews, 1987; Matthews et al., 1990). In general, the plant fossils in the Beaufort beds at Ballast Brook, like those in the ' type' Beaufort on Prince Patrick Island, are indicative of coniferous forest (Fyles, 1990)--a coniferous forest more similar to those presently growing in subarctic regions than the coniferous forest which existed during deposition of the Ballast Brook Formation. Many of the other plant taxa as well as a majority of the insects represent forms that occur within the boreal forest region today, though some live not much north of the southern border of that zone.

The slow growth exhibited by wood from Unit B at the supplementary reference section may mean that the forests on NW Banks Island during accumulation of the Beaufort Formation were growing under marginal climatic conditions. On Meighen Island (Fig. 1), several lines of evidence suggest that the slow growth of trees during deposition of the Beaufort Formation was due to the proximity of tree line. Although slow tree growth during deposition of Unit B at Ballast Brook might perhaps be due to climatic conditions, Ballast Brook is considerably south of Meighen Island and there are no other indicators of tree line environments in the fossil assemblages from the Beaufort Formation at Ballast Brook.

SUMMARY AND DISCUSSION

This paper formally separates the Neogene sediments exposed on NW Banks Island into two formations of markedly different character and age. The lower formation, here named the Ballast Brook Formation, consists of sandy, meandering river sediments and of peat and clay deposited in flood-plain swamps and lakes. Since their deposition, these sediments have been slightly tilted and the contained plant materials compressed. The upper formation, typical of the Beaufort Formation at other localities, consists of braided-river sand and gravel, and some silt, containing unaltered, uncompressed wood and other plant materials. A major unconformity separates the two formations.

The probable age of the Ballast Brook Formation, based on paleobotanical comparison with the Mary Sachs gravel flora at Duck Hawk Bluffs on SW Banks Island, and with radiometrically dated sites in east central Alaska, well-studied floras of the Cook Inlet region (Alaska) and macrofloras from Russia, is early to middle Miocene. In addition to the Duck Hawk Bluffs site, paleontologically similar strata in the surrounding region are known in the vicinity of Horton River on the mainland to the south (e.g. West River beds: Matthews, in preparation) and in the subsurface of the Beaufort-Mackenzie Basin (White and Ager, this volume). Other occurrences of the Ballast Brook Formation are undoubtedly present on Banks Island, but as yet have not been clearly recognized or distinguished from the much more widely exposed Beaufort Formation (Vincent, 1990) and, in

the northwest part of the island, from sandy units in the Eureka Sound Group (Miall, 1979). One candidate site, visited by Fyles in 1960 and Fyles and Hills in 1990, occurs in the headwaters region of Muskox River (Fig. 1).

Fluvial gravels and sands in the Duck Hawk Bluffs section on SW Banks. Island, assigned to the Beaufort Formation in earlier publications (Hills et al., 1974; Matthews et al., 1986), are now assigned to the Mary Sachs gravel (informal name, Fyles, 1990), which, as indicated above, is thought to be correlative with the Ballast Brook Formation. In one discussion of those deposits, two Beaufort Units (Tb I and Tb2) were recognized and suggested to be probable equivalents of the two 'Beaufort ' units then recognized at Ballast Brook (Matthews et al., 1986). From this, it might be concluded that the Duck Hawk Bluffs section contains deposits equivalent to both the Ballast Brook Formation and Beaufort Formation at Ballast Brook. However, it has since been shown (Matthews, 1989; Matthews, in preparation) that this is not correct and that the presumed upper Beaufort unit at Duck Hawk Bluffs (Tb2) possesses a suite of fossils similar to that in Tb E, the differences being due to the finer sediments in Tb,.

Comparisons with other sites including Meighen Island and Prince Patrick Island suggest that the age of the Beaufort Formation at Ballast Brook is late Early to early Late Pliocene--in the range 5-3 Ma (e.g. Clamgulchian in terms of Cook Inlet stages, Wolfe, 1981). This estimate could be tested by further study of Beaufort-type deposits in the region, but despite the widespread occurrence of the wood-bearing Beaufort (?) strata on Banks Island (Vincent, 1990), paleobotanical investigations have so far been carried out only in the Ballast Brook area.

Magnetism

Sediments of both the Ballast Brook and Beaufort Formations have provided poor records of the paleofield. The Ballast Brook Formation has yielded no record of reversals. However, samples from the Beaufort Formation have yielded evidence of at least two reversals--still insufficient for comparison with the polarity time scale. Magnetic susceptibilities of the two formations differ by a factor of five, the Ballast Brook being the less magnetic. This difference could signify lower initial content of magnetite in the Ballast Brook Formation (supported by difference in mineral character of sands characteristic of the two units). It is more likely, however, that magnetite initially contained in the sediment making up the Ballast Brook Formation became dissociated under the warm, swampy organic and acidic environment of deposition of the formation (involving alternations of oxic and anoxic conditions), and that further depletion occurred during the subsequent long period of burial of these sediments. The Beaufort Formation, although equally organic, has presumably lost substantially less magnetite by the same process, because of its

Late Tcrtiary Formations in Arctic Canada 169

cool environment of deposition and shorter period of burial.

Floristic Comparisons The Ballast Brook exposures provide a unique

opportunity to compare floras of two different-age'd late Tert iary floras at a single Arctic site, without having to make allowance for latitudinal or regional variables. Furthermore, the light regime at the site at the time of the two floras was about the same as at present (Hicken and Irving, 1977.

The two fossil floras are about equally rich in plant taxa: a minimum of 65 species in 34 families in the Ballast Brook Formation; 66 species in 32 families in the Beaufort Formation, but this similarity in numerical richness conceals important floristic differences. For example, Taxodiaceae, Saururaceae, Moraceae, Mag- noliaccae, Droseraccae, Saxifragaceae, Rhamnaceae , Melastomaceae among others listed for the Ballast Brook Formation in Table 3 do not occur in the Beaufort Formation at Ballast Brook. Where they do occur in the Beaufort Formation at other sites, the fossils probably have been rebedded from older units. The distribution of most of these families is presently fitr south of the boreal and subarctic zone. In contrast nearly all of the families from the Beaufort Formation have species that presently occur in northern Canada.

Several families present in the Beaufort Formation at Ballast Brook arc absent from the Ballast Brook flora: Schcuzeriaccae, Gramineae , Zingibcraceac, Polygon- aceae, Chenopodiaceae, Caryophyllaceae, Nymphaceae, Verbeniaceae, Violaceac and Compositac. Some of these do occur in the flora from the Mary Sachs gravel and from the West River beds (Matthews, in preparation), so their absence from the Ballast Brook flora at Ballast Brook may represent nothing more than a sampling bias. Caryophyllaceae, Vcrbeniaceae and Composi tae have not yet been recorded by macrofossils at any of the three Miocene sites, and preliminary analyses show that these same families are also missing from the pollen floras (T. Agcr, pers. comrnun., 1992 and Table 2). In contrast, Compositae and Caryophyllaceac arc represented in many samples from the Beaufort Formation (see Tables 2, 3 and 5).

Differences at the generic level are equally revealing. Glyptostrobus, Metasequoia, Phyllanthus, Nigrella, Tttbela, Morus, Liriodendron and Aldrovanda occur as macrofossils in the Ballast Brook Formation but not in the Beaufort Formation. Although pollen samples from the Bcaufort Formation at Ballast Brook contain significant percentages of rebedded Glyptostrobus pollen and other taxodiaceous types (M. Frappicr, unpublished report to the GSC, 1993), no known Beaufort Formation flora from any site in the Arctic has yielded macrofossils of either Glyptostrobus or T~xodium and the rare cone fragments of Metasequoia are undoubtedly rebeddcd.

The Ballast Brook Formation also contains taxodiaceous wood (Table 4) which as yet has not been recorded from the Beaufort Formation. The entire

family, Taxodiaceae probably became extinct on northern Banks Island (and the Canadian Arctic) before the early Pliocene.

Several genera, such as Cleorne, Bidens, Triglochin and Physocarpus occur in the Beaufort Formation but not the Ballast Brook Formation. In addition, one of the pollen samples from the Beaufort Formation contains Dryas, another taxon missing from the Ballast Brook Formation (M. Frappier, unpublished report to the GSC, 1993). Some of these taxa have yet to be recognized in any Miocene deposit in Arctic Canada (Table 5).

ACKNOWLEDGEMENTS

Alice Telka (GSC) contributed signiticantly in the photography of the macrofossils illustrated here. In addition the Photomcchanical Unit of the Geological Survey worked closely with Manhcws in preparation of the halftones of fossils and sections.

We have benetiled from field discussions and other critiques by several colleagues, among them, J.-S. Vincent, D. Hodgson and by comments made by Russian colleagues A. Velichko, Y. Musatov and A. Sher during a brief visit to the site in 1991. None of the tield work reported here could have occurred without the generous support of the Polar Continental Shelf Project and its staff. Field support in 19911 and 1991 was organized by J.-S. Vincent. Some of Hills' research was supported through a grant from Natural Sciences anti Engineering Research Council of Canada,

REFERENCES

Baranova, Y.P., ll'jinskaja, I.A., Nikitin, V.P., Pneva, G.P., Fradkina, A.F. and Schvareva, N.Y. (1976). The Miocene of the Mamontova Gora (Stratigraphy and Paleoflora) (in Russian), 284 pp. "'NAUKA". Moscow.

Basinger, J.F. (1991). The fossil forests of the Buchanan Lake Formation (Early Tertiary), Axel Hciberg Island, Canadian Arctic Archipelago: Preliminary floristics and paleoclimate. In: Christie, R.L. and McMillan, N.J. (eds), Tertiary Fossil Forests of the Geodetic Hills, Axel Heiberg Island. Arctic Archipelago, pp. 39 65. Geological Survey of Canada, Bulletin 403.

Bennike, O. (199t)). The Kap KObenhaven Formation: stratigraphy and palaeobotany of a Plio-Pleistocene sequence in Peary Land, North Greenland. Meddelelser om GrOnhmd. 23, 85 pp.

Boulter, M., Hubbard, R.N.L.B. and Kvacek, Z. (1993). A comparison of intuitive and objective interpretations of Miocene plant assemblages from north Bohemia. Palaeogeography, Palaeoclimatology, Palaeoecology, 101, 81-96.

Craig, B.G. and Fyles, J.G. (1965). Quaternary of Arctic Canada. Anthropogene Period in Arctic" and Subarctic (in Russian with English abstract), 143, 5-33.

Critchfield, W.B. (1986). Hybridization and classification of the white pines (Pinus section Strobus). Taxon. 35, 647-656.

Czcczott, H. (1959). Flora Kopalna Turowa Kolo Bogatyni (The fossil flora of Turow near Bogatynia). t'race Museum Ziemi, 3, 128 pp.

Devaney, J.R. (1991). Clastic sedimcntology of the Bcaufort Formation, Prince Patrick Island, Canadian Arctic Islands: Late Tertiary sandy braided river deposits with woody detritus beds. Arctic, 44 (3), 206-216.

Dorofeev, P.I. (1963). Tertiary Floras of Western Siberia (in Russian), 345 pp. U.S.S.R. Academy of Sciences, Komarov Botanical Institute, Leningrad.

Dorofcev, P.l. (1969). The Miocene flora ~)f the Mammoth- Mountain on the AIdan River (in Russian), 123 pp. "'NAUKA", Leningrad.

Durrell, L.W. (1916). Notes on some North American confiers based on leaf characters, Proceedings" of the Iowa Academy of Science, 23, 519-583.

Fouch, T.D. Carter, L.D., Kunk, M.J., Smith, C.A.S. and White, J. (1994). Miocene and Plioccne lacustrine and fluvial sequences, upper Ramparts and Canyon Village, Porcupine River, east-central Alaska. Quaternary International, 22/23, 11 29.

170 J .G . Fyles et al.

Friis, E.M. (1979). The Damgaard flora: a new Middle Miocene flora from Denmark. Bulletin of the Geological Society of Denmark, 27, 11%142.

Friis, E.M. (1985). Angiosperm fruits and seeds from the Middle Miocene of Jutland (Denmark). Det Kongelige Danske Videnskaberne Selskab Biologiske Skrifter, 24, 165 pp.

Fyles, J.G. (1990). Beaufort Formation (Late Tertiary) as seen from Prince Patrick Island, Arctic Canada, Arctic, 43, 393-4113.

Fyles, J.G., Marincovich, L., Jr, Matthews, J.V., Jr and Barendregt, R. (19911. Unique mollusc find in the Beaufort Formation (Pliocene) Meighen Island, Arctic Canada. Current Research, Part B, Geological Survey of Canada, Paper 91-1B, 105-I 11.

Gelderen, D.M. van and Hoey Smith, J.R.P. van 11986). Conifers', 375 pp. Timber Press, Inc., Portland, Oregon.

Harlow, W.M. (1931). The identification of the pines of the United States, native and introduced, by needle structure. Bulletin of the New York State College of Forestry at Syracuse University Tech. Publication, 32, 1-21.

Heer, O. (1868). Die Fossile Flora der Polarliinder, 192 pp. Druck und Verlag von Ztirich.

Hicken, A. and Irving, E. (19771. Tectonic rotation in western Canada. Nature, 268, 219-221/.

Hills, L.V. (1969). Beaufort Formation, northwestern Banks Island, District of Franklin. Report of Activities, Geological Survey of Canada, Paper 69-1A, 204-207.

Hills, L.V. 11970). Stratigraphy of Beaufort Formation along western margin of Canadian Arctic Islands. Bulletin of American Association of Petroleum Geologists, 54, 2486.

Hills, L.V. (1975). Late Tertiary floras Arctic Canada: An interpretation. Proceedings of Circumpolar Conference on Northern Ecology, 1(65)-1171). National Research Council of Canada.

Hills. L.V., Klovan, J.E. and Sweet, A.R. (1974). Juglans eocinerea n. sp., Beaufort Formation (Tertiary) southwestern Banks Island, Arctic Canada. Canadian Journal of Botany, 52, 65-90.

Hills, L.V. and Ogilvie, R.T. (t9701. Picea banksi n. sp., Beaufort Formation (Tertiary), northwestern Banks Island, Arctic Canada. (anadian Journal of Botany, 48, 457-464.

lltis, H.H. (1957). Studies in the Capparidaceae Ill. Evolution and phylogeny of the western North American Cleomoideae. Annals ~2[ the Missouri Botanical Garden, 44, 77-119.

Irving, E., Woodsworth, G.J., Wynne, F,J. and Morrison, A. (1985). Paleomagnetic evidence for displacement from the south of the Coast Plutonic Complex, British Columbia. Canadian Journal of Earth Sciences, 22, 584-598.

Kay, P.A. (1978). Dendroecology in Canada's forest-tundra transition zone. Arctic and Alpine Research, 10, 133-138.

Kirchheimer, F. (1957). Die Laubgewiichse der Braunkohlenzeit, 783 pp. Veb Wilhelm Knapp Verlag, Halle (Saale), Germany.

Kuc, M. and Hills, L.V. (1971). Fossil mosses, Beaufort Formation (Tertiary), northwestern Banks Island, western Canada Arctic. Canadian ,h)urnal of Botany, 49, 1089-1094.

Kunk, M.J., Rieck, H., Fouch, T.D. and Carter, L.D. (1994). 4~Ar/3~Ar age constraints on Neogene sedimentary beds, upper Ramparts, Howling Dog Canyon and Canyon Village sites, Porcupine River,east-central Alaska. Quaternary International, 22/23, 31-42.

Lamotte, R.S. (1952). Catalogue of the Cenozoic Plants of North America Through 1950. Geological Society of America. Memoir, 51,381 pp.

Lancucka-Srodoniowa, M. (1966). Tortonian flora from the "Gdow Bay" in the south of Poland. ACTA Paleobotanica, 7, 135 pp.

LePage, B.A. and Basinger, J.F. (1991). Early Tertiary Larix from the Buchanan Lake Formation, Canadian Arctic Archipelago, and a consideration of the phytogeography of the genus. In: Christie, R.L. and McMillan, N.J. (eds), Tertiary Fossil Forests 0/" the Geodetic Hills, Axel Heiberg Island, Arctic Archipelago, pp. 67-82. Geological Survey of Canada, Bulletin 403.

Mfidler, K. (1939). Die PliozSne Flora von Frankfurt am Main. Abhandlungen der Senckenbergischen Naturfors'chenden Ges'ellschaft, 466, 202 pp.

Mai, D.H. (1964). Die Mastixioideen-Floren im Tertidr der Oberlausitz, 192 pp. Akademie-Verlag, Berlin.

Mai, D.H. and Walther, H. 11988). Die pliozfinen Foren wm Thtiringen, Deutsche Demokratische Republik. Quartdr- paliiontologie, 7, 55-297.

Manchester, S.R. and Kress, W.J. (1993). Fossil Bananas (Musaceae): Ensete oregonense sp. nov. from the Eocene of western North America and its Phytogeographic Significance. American Journal of Botany, 80, 1264-1272.

Matthews, J.V., Jr (1977). Tertiary Coleoptera fossils from the North American Arctic. The Coleopterists Bulletin, 31,297-308.

Matthews, J.V., Jr (1987). Plant macrofossils from the Neogene Beaufort Formation on Banks and Meighen Islands, District of Franklin. Current Research, Part A, Geological Survey of Canada, Paper 87-1A, 73-87.

Matthews, J.V., Jr (1989). New information on the flora and age of the Beaufort Formation, Arctic Archipelago, and related Tertiary deposits in Alaska. Current Research, Geological Survey of Canada Paper 89-1D, 105-111.

Matthews, J.V., Jr (in preparation). Late Cenozoic Plant and Insect Macrofossils from Alaska and Arctic/Sub Arctic Canada: New data, International comparisons, new correlations. Quaternary International.

Matthews, J.V., Jr, Mott, R.J. and Vincent, J.-S. (1986). Preglacial and interglacial environments of Banks Island: pollen and macrofossils from Duck Hawk Bluffs and related sites. G~ographie physique et Quaternaire, 40, 279-298.

Matthews, J.V., Jr and Ovenden, L.E. (1990). Late Tertiary plant macrofossils from localities in Arctic/Subarctic North America (Alaska, Yukon and Northwest Territories): a review of the data. Arctic, 43, 364-392.

Matthews. J.V., Jr, Ovenden, L.E. and Fyles, J.G. (1990). Plant and insect fossils from the Late Tertiary Beaufort Formation on Prince Patrick Island, N.W.T. ln: Harington, C.R. (ed.), Canada's Missing Dimension: Science and History in the Canadian Arctic Islands', Vol. 1, pp. 1115-139. Canadian Museum of Nature, Ottawa.

Matthews, J.V., Jr, Drouk, A., Westgate, J.A. and Ovenden, L.E. (in preparation). Fossils of plants and arthropods from the upper pit of the Lost Chicken Gold Mine (east central Alaska): A late Pliocene window on the environment of East Beringia. Quaternary International.

Matthews, J.V., Jr, Fyles, J.G., Barendregt, R., Marincovich, L., Brouwers, E., MacNeil, D., Irving, T., Behan-Pelltier, V. Biostratigraphy the Beaufort Formation on Meighen Island, N.W.T.: implications for climate and environment surrounding the Arctic Ocean about 3 My B.P. Quaternary International (in preparation).

Miall, A.D. (1979). Mesozoic and Tertiary geology of Banks Island, Arctic Canada. Geological Survey qf" Canada, Memoir. 387, 235 pp,

Miller, C.N. and Ping, L. (1994). Structurally Preserved Larch and Spruce Cones from the Pliocene of Alaska. Quaterna O, International, 22/23, 207-214.

Nikitin, V.P. (1979a). Paleocarpological data for stratigraphy of Neogene in Kava-Tauri depression (northern part of Okhotsk coast) (in Russian). In: Shilo, N.A. and Baranova, J.A. (eds). Continental Tertiary deposits of North-East Asia, pp. 130-149. NAUKA, Siberian Branch, Novosibirsk.

Nikitim V.P. (1979b). Neogenc floras of North-East USSR (material of paleocarpological investigations) (in Russian). hi: Shilo, N.A. and Baranova, J.A. (eds.), Continental Tertiary Deposits" of North-East Asia, pp. 1311-149. NAUKA, Siberian Branch, Novosibirsk.

Obst, J.R., McMillian, N.J., Blanchette. R.A., Christensen, D.J., Faix, O., Ham J.S., Kuster, T.A., Landucci, I.L., Newman, R.H., Pettersen, R.C., Schwandt, V.H. and Wesolowski, M.F. (1991). Characterization of Canadian Arctic fossil woods, hi: Christie, R.L. and McMillan, N.J. (eds), Tertiary Fossil Forests of the Geodetic Hills', Axel Heiberg Island, Arctic Archipelago, pp. 123-144. Geological Survey of Canada, Bulletin 403.

Parks, C.R. and Wendel, J.F. (19911). Molecular divergence between Asian and North American species of Liriodendron (Magnoliaceae) with implications for interpretation of fossil floras. American Journal of Botany, 77, 1243-1256.

Rowe, J.S. (1972). Forest Regions of Canada, 171 pp. Publication 13111/of Canadian Forestry Service, Ottawa.

Roy, S.K. and Hills, L.V. (1972). Fossil woods from the Beaufort Formation (Tertiary) northwestern Banks Island, Arctic Canada. Canadian Journal of Botany, 50, 2637-2648.

Shorn, H.E. (1994). A preliminary discussion of fossil larches (Larix Pinaceae) from the Arctic. Quaternary International, 22/23, 173-183.

Takhtajan, A. (ed.) (1982). Fossil Flowering Plants" of the USSR, vol. 2 Ulmaceae-Betulaceae (in Russian), 261 pp. NAUKA, Leningrad.

Thorsteinsson, R. and Tozer, E.T. (1962). Banks, Victoria and Steffanson Islands. Arctic Archipelago. Geological Survey o1" Canada, Memoir, 330, 85 pp.

Late Tertiary Formations in Arctic Canad~l 171

Tiffney, B.H. (1981). Fruits and seeds of the Brandon lignite. V1. Microdiptera (Lythraceae). Journal of the Arnold Arboretum, 62, 487-516.

Tozer, E.T. (1956). Geological reconnaissance of Prince Patrick Island, Eglinton and western Melville Islands, Arctic Archipelago, Northwest Territories. Geological Survey of Canada Paper 55-5, 1-32.

Vincent, J.-S. (1983). La G6ologie du Quaternaire et la G6omorphologie de Lqle Banks, Arctique Canadien. Geological Survey of Canada. Memoir, 405, 118 pp.

Vincent, J.-S. (1990). Late Tertiary and Early Pleistocene deposits and history of Banks Island, southwestern Canadian Arctic Archipelago. Arctic, 43, 339-363.

Webster, G.L. (1970). A revision of Phyllanthus (Euphorbiaceae) in the Contintental United States. Brittonia, 22, 44-76.

White, J. and Ager, T. (1994). Palynology, paleoclimatology and correlation of Middle Miocene beds from Porcupine River (Locality 9(I-1), Alaska. Quaternary bzternational, 22/23, 43-77.

Wolfe, J.A. (1977). Paleogene floras from the Gulf of Alaska

region. United States Geological Survey Pr~['essional Paper 997, 108 pp.

Wolfe, J.A. (1981). A chronologic framework for Cenozoic megafossil floras of northwestern North America and its relation to marine geochronology. Geological Society c~f America, Special Paper 184, 39-47.

Wolfe, J.A. and Tanai, T. (1980). The Miocenc Seldovia Point Flora from the Kenai Group, Alaska. U.S. Geological Survey Professional Paper ! 105, 52 pp.

Wolfe, J.A. and Poore, R.Z. (1982). Tertiary marine and nonmarine climatic trends. Climate in Earth History. Studies in Geophysics pp. I54-158. National Academy Press, Washington, D.C.

Zagwijn, W.H. (1990). Subtropical relicts n the Pliocenc flora of Brunnsum (The Netherlands). Geologic en Mijnbouw, 69, 219-225.

Zubakov, V.A. and Borzenkova, 1.1. (1990). Global Paleoclimate of the late Cenozoic. Developments in Palaeontology and Stratigraphy, 12, 456 pp. Elsevier, Amsterdam.

Documents

Ballast Brook and Beaufort Formations (late Tertiary) on Northern Banks Island, Arctic Canada