Structural Overprinting in the Northwestern Skeena Fold Belt(NTS 104B, H), Northwestern British Columbia1

by W. Loogman2, J-F. Gagnon2, J.W.F. Waldron3 and C.A. Evenchick3

KEYWORDS: Skeena Fold Belt, folds, faults, over print -ing

INTRODUCTION

The Skeena Fold Belt, as de fined by Evenchick(1991a), is lo cated in north west ern Brit ish Co lum bia, in the Stikine Terrane of the Intermontane Belt of the Ca na dianCor dil lera (Fig 1). The dis tri bu tion of the Skeena Fold Beltroughly mir rors the lo ca tion of the Me so zoic Bow ser Ba -sin, and the fold belt is pre dom i nantly de vel oped in theMid dle Ju ras sic – Early Cre ta ceous Bow ser Lake Group ofthe Bow ser Ba sin. The Early Ju ras sic Hazelton Group andthe Late Cre ta ceous Sustut Group are also af fected by fold -ing and thrust fault ing. Two re gional fold trends are pres entwithin the Skeena Fold Belt: north west-trending folds aredom i nant in the east ern two-thirds of the fold belt, andnorth east-trending folds are pres ent in the west ern third(Fig 1). Lo cally, these fold trends are found out side theirdom i nant do mains and over print each other (Evenchick,1991a; Evenchick, 2001). It is the aim of this study to eval -u ate over printed struc tures and their tim ing re la tion ships.Field work was con ducted in 2006 as a fol low-up to field -work car ried out in the sum mer of 2005 and re ported on byWaldron et al. (2006). This work ac com pa nies that re ported by Gagnon et al. (2007).

In an ef fort to aid in hy dro car bon ex plo ra tion withinthe Bow ser Ba sin, re cent stud ies of its pe tro leum po ten tialby the Geo log i cal Sur vey of Can ada and BC Min is try ofEn ergy, Mines and Pe tro leum Re sources (Osadetz et al.,2003; Evenchick et al., 2003) have fo cused on up dat ing thether mal ma tu rity mod els of Bustin and Mof fat (1989),which pre dicted un fa vour ably high heat flow to much ofthe Bow ser Ba sin, and on de vel op ing mod els for as sess ingthe ef fec tive ness of pe tro leum sys tems. In ad di tion to con -ven tional pe tro leum, there is po ten tial for coalbed meth aneand con ven tional coal. Min eral po ten tial ex ists in vol ca nicrocks on the flanks of the ba sin (Fig 1), as shown by thehigh-grade stratiform volcanogenic mas sive sul phide(VMS) Au-Ag de pos its at Eskay Creek (Roth et al., 1999).

Un der stand ing the struc tural his tory of the region willcontribute to exploration and evaluation of these resources.

REGIONAL STRATIGRAPHICFRAMEWORK

The mapped re gions of the Skeena Fold Belt ex poserocks of the Mid dle Ju ras sic – Early Cre ta ceous Bow serLake Group, in clud ing the Ritchie-Alger, Eaglenest andSkelhorne lithofacies as sem blages, de scribed in Evenchick and Thorkelson (2005). The lack of re gion ally cor re la tivebound aries in the Bow ser Lake Group makes the use of for -mal for ma tion/group des ig na tions dif fi cult. Syn chro nousde po si tion of shal low and deep ma rine fa cies oc curred; theBow ser Lake Group re flects an over all progradationaldepositional history.

The Ritchie-Alger as sem blage com prises sand stone,siltstone and shale, with rare chert-rich con glom er ate.Sheet-like in ter vals of fine to me dium-grained sand stone,sep a rated by shale in ter vals that are metres thick, have been in ter preted to re late to sub ma rine fan de po si t ion(Evenchick and Thorkelson, 2005). Ev i dence of turbiditeac cu mu la tion within the sub ma rine fan com plexes in cludes nor mal grad ing, groove casts, dewatering struc tures andBouma cy cles. The Ritchie-Alger as sem blage is es ti matedto reach thick nesses of 1800 m in the west ern third of theBow ser Basin (Evenchick and Thorkelson, 2005).

The Skelhorne lithofacies as sem blage com prises morethan 1000 m of siltstone, sand stone and con glom er ate(Evenchick and Thorkelson, 2005). Com mon me dium tothick-bed ded coars en ing-up ward cy cles, ma rine and plantfos sils, wave-gen er ated rip ples and bioturbation are in ter -preted to re cord a mod er ate-en ergy deltaic depositional en -vi ron ment (Evenchick and Thorkelson, 2005). TheSkelhorne as sem blage is most com mon in the west-cen tralpart of the Bowser Basin.

The Eaglenest lithofacies as sem blage com prises ahigh per cent age (up to 80%) of rusty- weath er ing con glom -er ate and sand stone, with mi nor siltstone and shale, andreaches thick nesses of 1000 m (Evenchick and Thorkelson, 2005). Con glom er ate clasts are well-rounded and well-sorted peb bles com posed pre dom i nantly of chert. Plant fos -sils, in clud ing sub stan tial si lici fied trees, are abun dant,whereas ma rine fos sils are rare. The abun dance of con -glom er ate, coars en ing-up ward cy cles and tree fos sils allsug gest a high-en ergy deltaic depositional en vi ron ment(Evenchick and Thorkelson, 2005).

EXISTING STRUCTURAL FRAMEWORK

The Skeena Fold Belt over lies the Stikine Terrane ofthe Intermontane Belt (Evenchick, 1991a). The Skeena

Geo log i cal Field work 2006, Pa per 2007-1 325

1 Geoscience BC con tri bu tion GBC0222 Department of Earth Sciences, University of Alberta,

Edmonton, AB T6G 2E33 Geological Survey of Canada, 605 Robson Street, Vancouver,

BC V6B 5J3

This publication is also available, free of charge, as colourdigital files in Adobe Acrobat® PDF format from the BCMinistry of Energy, Mines and Petroleum Resources website athttp://www.em.gov.bc.ca/Mining/Geolsurv/Publications/catalog/cat_fldwk.htm

Fold Belt was formed be tween the Albian and early Ter tiary (Evenchick, 1991a; Evenchick and Thorkelson, 2005). The fold belt has been in ter preted as a fold-and-thrust beltrooted in the Coast Moun tains (Evenchick, 1991b).Evenchick (2001) sug gested that oblique north west-south -east short en ing oc curred first, af fect ing the west ern Bow ser Ba sin, and was fol lowed by a long pe riod of north east-south west short en ing that gen er ated north west-trendingfolds, par al lel to the sur face strike of the Ca na dian Cor dil -lera. On the ba sis of work con ducted in the Groundhogcoal field, Mof fat and Bustin (1993) pro posed three pe ri odsof short en ing: ini tial north east-south west short en ing, thennorth west-south east short en ing and lastly north east-south -west short en ing. Bone (2002) ex am ined a basinal fold-in -ter fer ence pat tern iden ti fied by Evenchick (1991a), formed by in ter sec tion of two sim i lar-scale syn clines, con firm ingthe pres ence of type I fold in ter fer ence (Ramsay, 1967); in -ter fer ence of this type can produce domes favourable topetroleum accumulation.

2006 FIELD MAPPING

Dur ing the 2006 field sea son, six ar eas were mapped at1:25 000 scale from he li cop ter-po si tioned fly camps(Fig 1). Re sults from three of these ar eas are re ported onhere. The Iskut ridge area was se lected due to its prox im ityto the Eskay Creek area, an area known to have mul ti plegen er a tions of folds (Read et al., 1989; Lewis, 1992;Waldron et al., 2006). The Cartmel Lake area was se lectedas an area dom i nated by north west-trending folds with pos -

si ble over print ing of north east-trending folds, rec og nizedby Evenchick and Green (2004). The Sweeny Creek areawas cho sen for its con ver gence of fold trends, as shown byEvenchick (2004).

Iskut Ridge

A small ridge, east of the Iskut River and north ofPalmiere Creek at the west ern mar gin of the Bow ser Ba sin,is herein re ferred to as ‘Iskut ridge’ (Fig 1). All rock unitsob served in this area are as signed to the Ritchie-Algerlithofacies as sem blage (Evenchick et al., 2004). Struc turein the Iskut ridge area is dom i nated by north and north-north east-trending folds trace able through out much of themap area (Fig 2). North-trending folds are rounded andopen to tight. Mappable de flec tions in north-trending ax ialtraces oc cur near south east-trending mi nor folds. Mi norfolds are open to tight, and com monly plunge steeply(~60º) southeast.

Equal-area pro jec tions of poles to bed ding (Fig 3a)show a dif fuse gir dle dis tri bu tion with an eigenvector 1plung ing steeply to ward the south east. These data sug gestsmall-scale fold ing about a south east-plung ing axis, in con -trast to map-scale re la tion ships that in di cate north-trending folds as the dom i nant struc ture. Cleav age is ubiq ui touswithin fine units of the turbidite suc ces sion and spo radic incoarser sand stone. Pen cil lineations are wide spread, de -fined by in ter sec tion of steep bed ding and steep cleav age.Cleav age data shown in Fig ure 3b lie in two clus ters: adom i nant steeply dip ping cleav age that strikes north west,

326 Geoscience BC, Re port 2007-1

LIM

IT OF CORDILLERAN D

EF

OR

MAT

ION

FO

RE

LAN

D B

ELT

FO

RE

LAN

D B

ELTIN

TERM

ON

TANE BELT

INTER

MO

NTAN

E BELTO

MIN

EC

A B

ELT

INTER

MO

NTAN

E BELT

CO

AS

T BE

LT

CO

AS

T BE

LT

INS

ULA

R B

ELT

FO

RE

LAN

D B

ELT

60°N

49°N

120°

WA

LBE

RTA

BR

ITIS

H C

OLU

MB

IA

BOWSERBASIN

CO

AS

T BE

LT

Oweegee domeOweegee dome

EskayCreekEskayCreek

Axial trace of fold

Oweegee dome

EskayCreek

CRETACEOUS

Sustut Group

MIDDLE JURASSIC TO MID-CRETACEOUS

Bowser Lake Group

EARLY MIDDLE JURASSIC AND OLDER

Upper Hazelton Group clastic rocks

Hazelton Group volcanic rocks

Mapping area

PALEOZOIC

57N

o56No128W

kilometres

500130W 128W

CartmelLakeCartmelLakeCartmelLake

IskutRidgeIskutRidgeIskutRidge

SweenyCreekSweenyCreekSweenyCreek

N

Fig ure 1. Sim pli fied re gional ge ol ogy of the north west ern Skeena Fold Belt (com piled from Evenchick, 1991a; Bone, 2002; Evenchick andThorkelson, 2005; Waldron et al., 2006), show ing fold ax ial traces and study ar eas re ferred to in the text; in set shows lo ca tion of fig urewithin the Ca na dian Cor dil lera.

and a lesser steep cleav age that strikes north east. In out -crop, cleav age ap pears to be a spaced pres sure-so lu tionfab ric. Slaty cleav age char ac ter ized by pen e tra tive min eralalign ment is rare. Ori ented sam ples were col lected and willbe used for fu ture petrographic anal y ses of cleav age. Be -cause of the scar city of min eral align ment, over printedcleav age does not dis play crenulation. The clus ters of

cleav age poles in Fig ure 3b are at trib uted to su per po si tionof two ep i sodes of short en ing. There is no gir dle dis tri bu -tion, such as might be ex pected if an ear lier cleav age werere folded by later short en ing. This is likely be cause ex ten -sion di rec tions dur ing both de for ma tion ep i sodes werenearly par al lel and ap prox i mately ver ti cal. Mapped de flec -tions of north-south ax ial traces by south east-trending folds (Fig 2) in di cate that the north to north-north east-strik ingfolds formed first and were sub se quently over printed byrel a tively mi nor south east-trending folds. This is con sis -tent with overall folding of bedding about a southeast-plunging axis (Fig 3a), suggesting that minor folds are partof a larger structure.

Equal-area plots of bed ding-cleav age in ter sec tionlineations in Fig ure 3c show a scat tered clus ter cen tred on anorth west-trending axis. The scat ter is at trib uted to the rel -a tive scar city of north east-strik ing cleav age in com par i sonto north west-strik ing cleavage.

Faults are rel a tively rare in this area com pared with therest of the west ern Skeena Fold Belt. Brit tle struc tures ob -served in clude en échelon veins at a num ber of lo ca tions.There are a num ber of ‘S’ and ‘Z’ asym met ric veins in ter -preted to re cord sinistral and dextral move ment, re spec -tively. In some cases, both asym me tries can be ob served ata sin gle lo cal ity (Fig 4, 5). The pres ence of en échelon veins sug gests a com po nent of brit tle strain, pos si bly re lated tothe nearby For rest Kerr fault (Read et al., 1989) and faultsin ter preted by Lo gan et al. (2000).

Cartmel Lake

An area ex pos ing rocks of the Eaglenest as sem blageap prox i mately 3 km south west of Cartmel Lake was se -lected for study of pre vi ously rec og nized over printed folds(Evenchick and Green, 2004). The to pog ra phy is dom i -nated by cliff-form ing con glom er ate beds in which a near-ver ti cal rough cleav age dom i nates the exposed surfaces.

The struc ture at Cartmel Lake is dom i nated by threema jor folds that trend south east (Fig 6). At map scale, agently dip ping sur face in the north ern sec tion of the maparea trun cates bed ding at a low an gle and is in ter preted as adécollement. A fault in the south ern sec tion of the map areatrun cates bed ding in a sim i lar fash ion and is in ter preted as acon tin u a tion of the same décollement (Fig 6). Bed ding cut -offs in di cate that this de tach ment climbs upsection to thesouth east. As so ci ated out crop-scale folds face and vergesouth east. A north east-trending map-scale fold at the south -ern ex trem ity of the area is pre sumed to be re lated to thesame de for ma tion that pro duced the south east-verg ing de -tach ment. Map-scale south east-trending folds can betraced through the de tach ment without offset, implying that it must have been folded.

Nu mer ous steep north west-strik ing faults, trace ableover less than a kilo metre, off set cliff-form ing con glom er -ate in a dextral sense, with off sets rang ing from metres totens of metres (Fig 6). Slickenline lineations in di catedextral strike-slip mo tion. Rare sinistral faults of sim i larsize and scale, but trace able over just a few metres, are pres -ent. These faults off set the mapped trace of the low-an gledécollement by sim i lar amounts. The sinistral faults may be con ju gate to dextral faults, as sug gested by their clock wiseori en ta tion rel a tive to the dextral faults and sim i lar off set ofstrata. The ori en ta tions of the con ju gate faults sug gest anap prox i mate north-south shortening direction.

Geo log i cal Field work 2006, Pa per 2007-1 327

406000406000406000

406000406000406000

66229911000000

6291000

66229911000000

6291000

66229922000000

6292000

66229922000000

6292000

6293000

66229933000000

6293000

6293000

1360

1440

142

0

1460

1480

138

0

150

01520

1540

1560

15801600

16201640

160

0

1500

1520

1440

1520

1520

6464

7676

8686

6060

4444

6767

5858

6666

6464

6969

6767

7171

6464

6161

8686

7474

7878

8989

7373

5959

6262

5757

7979

70707575

8080

89892626

6464

7474

7878

8686

7474

7777

2424

7676

8181

3636

8585

8383

6868

7373

7777

8686

8787

6969

6868

7676

5656

7272

7575

7171

6464

7676

2626

6464

6969

7575

8181

7777

1313

6565

3636

64

76

86

60

44

67

58

66

64

69

71

64

61

86

74

78

89

73

59

62

57

79

70

80

8926

64

74

78

86

74

77

24

76

81

36

85

83

68

73

77

86

87

69

68

76

56

72

75

71

64

76

26

64

69

75

81

77

13

65

36

67

75

86

85

78

Legend

Cleavage

Bedding

Syncline

Anticline

Vertical beds

Contour elevations in metres.

Scale200 m

N

Axial trace

Fig ure 2. Struc ture of the Iskut Ridge area, show ing bed ding ori en -ta tions and mapped ax ial traces.

Spaced cleav age is well de vel oped in con glom er ate ofthe Cartmel Lake area, with some out crops show ing threedis tinct cleav age sets. The high per cent age (75–90%) ofcoarse-grained rock types within the Eaglenest lithofaciesas sem blage may ac count for the com mon oc cur rence ofcleav age within con glom er ate; li thol ogy is rel a tively ho -mo ge neous and there fore strain is not par ti tioned to finergrained rock types. The cleav age dis tri bu tion is un usualcom pared to other Bow ser Lake Group as sem blages thathave a bulk fine-grained com po si tion and only rarely de -velop cleav age in coarse rock types. Cleaved con glom er ateshows smooth weath er ing sur faces in stead of the ‘bumpy’weath er ing pat tern of peb ble con glom er ate else where in

the ba sin, as cleav age planes cut through peb bles. De spitede for ma tion of peb bles, sig nif i cant po ros ity is ob served tohave been re tained be tween the clasts. Equal-area plots ofcleav age poles in Fig ure 7b show a widely scat tered dis tri -bu tion, con sis tent with mul ti ple phases of de for ma tion.Equal-area plots of bed ding poles in Fig ure 7a show a dif -fuse gir dle nor mal to an east-south east-trending, shal lowlyplung ing eigenvector 1, con sis tent with mapping showingfolding of the low-angle detachment by northwest-trending folds.

Sweeny Creek

The area around the head wa ters of Sweeny Creek wasmapped, ex pand ing map ping of the Tumeka Creek studyarea re ported in Waldron et al. (2006). Rock units in thisarea be long to the Skelhorne as sem blage of the Bow serLake Group (Evenchick, 2004). Prior map ping in theSweeny Creek area re vealed north-north east and north-north west-trending folds con verg ing with out in ter sec tion,

328 Geoscience BC, Re port 2007-1

N

N = 73

2

1

N

N = 140

N

N = 68

CBA

E1

Fig ure 3. Lower-hemi sphere equal-area pro jec tion of struc tural data col lected in the Iskut ridge area: A) poles to bed ding; E1, eigenvector1; dashed line shows prin ci pal E1 gir dle plane; B) poles to cleav age, dot ted lines out line in ter preted dis tri bu tions of cleav age clus ters 1and 2; C) bed ding-cleav age in ter sec tion lineations.

Fig ure 4. Z-asym met ric en échelon quartz veins, in di cat ing dextraland re verse sense of shear; ar rows in di cate in ter preted sense ofshear; view to wards the west-north west.

Fig ure 5. S-asym met ric en échelon quartz veins, in di cat ingsinistral and re verse sense of shear; ar rows in di cate in ter pretedsense of shear; view to wards the west-south west.

within an area dom i nated by north west-trending folds(Evenchick, 2004). Folds mapped in the Sweeny Creekarea have vari able ori en ta tions, plung ing be tween north-north west and north-north east. Fig ure 8 shows ax ial tracesthat con verge with each other but do not cross cut. The mappat tern sug gests that these folds are of the same gen er a tion

and are part of a larger sys tem of con i cal folds. Map re la -tion ships also show that all north to north east folds ap pearto in crease in plunge to ward the north east. All bed ding inthe north ern part of the study area dips to the north east; re -gion ally, the struc tures in this area are part of the south westlimb of a gen tle north west-trending syncline, with a wave -

Geo log i cal Field work 2006, Pa per 2007-1 329

920

1940

1960

1900

1880

1980

1860

1840

2000

2020

2040

1820

1800

1780

176017

40

1720

1700

1680

1640

1620

1660

160

0

158

0

1560

2080

1540

2060

1520

2100

2120

150

0

2140

1480

2160

2180

2200

1620

200

0

2020

202

0

2000

18001980

1680

2000

1880

1840

170

0

1800

2100

1660

2080

1960

1580

1820

1900

1860

1900

1740

1840

160

0

170

0

2080

1820

1980

1760

2020

1780

2060

1960

1800

2100

2040

2160

1880

1980

206

0

1940

1740

1840

182

0

1660

1760

1780

1860

1760

1720

1960

1840

1740

1900

1980

1740

2120

2060

1680

1780

2140

1760

1920

1920

1940

1720

1920

15602000

2060

208

0

2000

2080

1540

1940

2040

1720

1960

1860

1880

1800

1700

204

0

182

0

1560

1920

1980

1840

2020

1800

1800

164

0

1860

1840

178

0

2000

2040

1880

1680

206

0

474000

475000

6398000

6396000

71

75

62

80

85

82

8

12

77

17

19

24

22

3216

21

47

29

19

23

1922

2233

51

22

40

31

34

19

2010

18

33

55

36

61

34

41

2735

28

40

31

5526

7071

35

43

31

48

42

26 6756

17 1924 26

29

80

24

48

36

25

11

45

Bedding-form linesObserved

Inferred

Inferred decollement

Late steep fault

Antiform

Synform

Eaglenest Assemblage

Jurassic-Cretaceous Bowser Lake Group

Red and rust-weathered conglomerate and subordinate sandstone

Mainly grey sandstone, siltstone, with coal and fossil plant remains

Form lines mark thick conglomerate beds

1 km

N

2180

Contour elevations in metres

Fig ure 6. Struc ture of the Cartmel Lake area; note dis tri bu tion of early décollement and later folds.

330 Geoscience BC, Re port 2007-1

N

N = 76

N

N = 103

A B

E1

Fig ure 7. Lower-hemi sphere equal-area pro jec tion of struc tural data col lected in the CartmelLake area: A) poles to bed ding; E1, eigenvector 1; dashed line shows prin ci pal E1 gir dleplane; B) poles to cleav age.

Fig ure 8. Struc ture of the Sweeny Creek area, show ing ori en ta tions of struc tures and ax ial traces.

length on ap prox i mately the 5 km scale, ob served to thenorth of Sweeny Creek. The syncline is in ter preted to haveincreased the plunge of north-trending folds.

DISCUSSION

All three ar eas mapped show over print ing of struc -tures. At Iskut ridge, a ma jor north to north-north east-trending fold is re folded by smaller, south east-trendingstruc tures. The Cartmel Lake area is char ac ter ized by over -print ing of north west-trending folds on an ear lier de tach -ment; folds as so ci ated with the ear lier de tach ment shownorth east trends. The Cartmel Lake area may re cord the im -por tance of de tach ments in the de for ma tion his tory of thearea, as sug gested by Evenchick (1991b). Over print ing isless clearly dis played at Sweeny Creek, but pro gres sivedown-plunge steep en ing of north east-trending folds is con -sis tent with refolding by folds with north west trends. Thus,struc tures in all three ar eas are con sis tent with early, gen er -ally north west-south east short en ing, followed bynortheast-southwest shortening.

The de vel op ment of type I dome-and-ba sin in ter fer -ence pat terns is de pend ent upon over print ing of folds at ahigh an gle. Large domes pro spec tive for pe tro leum ac cu -mu la tion re sult from in-phase in ter fer ence of anticlines ofsim i lar am pli tude. Where struc tures of dif fer ent wave -lengths or am pli tudes in ter fere, the re sult ing pat terns aremore com plex. Fold am pli tudes, wave lengths and in ter sec -tion an gles are vari able in the Skeena Fold Belt. At Iskutridge, the early north to north-north east folds are map scale, and folds with south east trends are rel a tively mi nor struc -tures. If pres ent in the subsurface, such a struc tural pat terncould serve as an ar ray of small pe tro leum traps, as south -east-trending folds could trap pe tro leum lo cated in earlyfolds. At Sweeny Creek, there is a north west-trending kilo -metre-scale syncline and the north-trending folds havewave lengths on the hun dred metre scale. Down-plungesteep en ing of early folds by a north west-trending fold ofthis type could drive subsurface pe tro leum mi gra tion to thesouth, form ing a broad pool with sev eral pock ets withinearly folds. The Cartmel Lake area in cludes mul ti ple sets of spaced pres sure-so lu tion cleav age within con glom er atethat dis solves peb bles but does not oblit er ate po ros ity in the ma trix. At Cartmel Lake, early folds are likely as so ci atedwith décollements. Lo cat ing such structures in thesubsurface would provide insights on the location ofpotential petroleum traps.

ACKNOWLEDGMENTS

The au thors thank Geoscience BC for con tin u ing tosup port this re search. Ad di tional field costs were sup ported by Nat u ral Sci ences and En gi neer ing Re search Coun cil ofCan ada (NSERC) Dis cov ery Grant A8508 to J. Waldron.H. Tomes and C. Bloomberg pro vided ex cel lent as sis tancein the field. He li cop ter sup port was pro vided by Quan tum,Prism and Pa cific West ern He li cop ters. Re search atCartmel Lake was made pos si ble through a re search per mitfrom the Spatsizi Pla teau Wil der ness Pro vin cial Park.Sabina Sil ver Cor po ra tion and the Eskay Creek mine werevery hos pi ta ble in al low ing us to visit their sites. Help ful re -view by Philippe Erdmer and Rob Stevens improved themanuscript.

REFERENCES

Bone, K.E. (2002): Rel a tive tim ing and sig nif i cance of fold ing inthe west ern Skeena Fold Belt, north west ern Bow ser Ba sin,Brit ish Co lum bia: in ter pre ta tion of struc tural and seis micre flec tion data; un pub lished MSc the sis, Uni ver sity of Brit -ish Co lum bia, Vancouver, BC, 171 pages.

Bustin, R.M. and Mof fat, I.W. (1989): Semianthracite, an thra citeand meta-an thra cite in the cen tral Ca na dian Cor dil lera: their ge ol ogy, char ac ter is tics and coalification his tory; in Coal:Clas si fi ca tion, Coalification, Min er al ogy, Trace-el e mentChem is try, and Oil and Gas Po ten tial, Ly ons P.C. andAlpern, B., Ed i tors, In ter na tional Jour nal of Coal Ge ol ogy,vol ume 13, pages 303–326.

Evenchick, C.A. (1991a): Ge om e try, evo lu tion, and tec tonicframe work of the Skeena Fold Belt, north cen tral Brit ish Co -lum bia; Tec ton ics, vol ume 10, pages 527–546.

Evenchick, C.A. (1991b): Struc tural re la tion ships of the SkeenaFold Belt west of the Bow ser Ba sin, north west Brit ish Co -lum bia; Ca na dian Jour nal of Earth Sci ences, vol ume 28,pages 973–983.

Evenchick, C.A. (2001): North east-trending folds in the west ernSkeena Fold Belt, north ern Ca na dian Cor dil lera: a re cord ofEarly Cre ta ceous sinistral plate con ver gence; Jour nal ofStruc tural Ge ol ogy, vol ume 23, pages 1123–1140.

Evenchick, C.A. (2004): Ge ol ogy, Sweeny Creek, Brit ish Co lum -bia; Geo log i cal Sur vey of Can ada, Map 2037A, scale1:50 000.

Evenchick, C.A., Ferri, F., Mus tard, P.S., McMechan, M.,Osadetz, K., Stasiuk, L., Wil son, N.S.F., Enkin, R.J.,Hadlari, T. and McNicoll, V.J. (2003): Re cent re sults and ac -tiv i ties of the In te grated Pe tro leum Re source Po ten tial andGeoscience Stud ies of the Bow ser and Sustut Bas ins Pro ject, Brit ish Co lum bia; Geo log i cal Sur vey of Can ada, Cur rentRe search 2003-A13, 11 pages.

Evenchick, C.A. and Green, G.M. (2004): Ge ol ogy, EaglenestCreek, Brit ish Co lum bia; Geo log i cal Sur vey of Can ada,Map 2029A, scale 1:50 000.

Evenchick, C.A., Mus tard, P.S., Woodsworth, G.J. and Ferri, F.(2004): Com pi la tion of ge ol ogy of Bow ser and Sustut bas ins draped on shaded re lief map, north-cen tral Brit ish Co lum -bia; Geo log i cal Sur vey of Can ada, Open File 4638, scale1:500 000.

Evenchick, C.A. and Thorkelson, D.J. (2005): Ge ol ogy of theSpatsizi River map area, north-cen tral Brit ish Co lum bia;Geo log i cal Sur vey of Can ada, Bul le tin 577, 276 pages.

Gagnon, J-F., Loogman, W., Waldron, J.W.F., Cordey, F. andEvenchick, C.A. (2007): Strati graphic re cord of ini ti a tion ofsed i men ta tion in the Bow ser Ba sin, north west ern Brit ishCo lum bia; BC Min is try of En ergy, Mines and Pe tro leum Re -sources , Geo log i cal Field work, Pa per 2007-1 andGeoscience BC, Re port 2007-1, pages 275–284.

Lewis, P.D. (1992): Struc tural ge ol ogy of the Prout Pla teau re gion,Iskut River map area, Brit ish Co lum bia (104B/9); in Geo -log i cal Field work 1991, BC Min is try of En ergy, Mines andPe tro leum Re sources, Pa per 1992-1, pages 521–527.

Lo gan, J.M., Drobe, J.R. and McClelland, W.C. (2000): Ge ol ogyof the For rest Kerr – Mess Creek Area, north west ern Brit ishCo lum bia, NTS 104B/10, 15, 104G/2, 7W; BC Min is try ofEn ergy, Mines and Pe tro leum Re sources, Bul le tin 104, 164pages.

Mof fat, I.W. and Bustin, R.M. (1993): Deformational his tory ofthe Groundhog coal field, north east ern Bow ser Ba sin, Brit -ish Co lum bia; styles, su per po si tion and tec tonic im pli ca -tions; Bul le tin of Ca na dian Pe tro leum Ge ol ogy, vol ume 41,pages 1–16.

Osadetz, K.G., Evenchick, C.A., Ferri, F., Stasiuk, L.D. and Wil -son, N.S.F. (2003): In di ca tions for ef fec tive pe tro leum sys -tems in Bow ser and Sustut Bas ins, north-cen tral Brit ish

Geo log i cal Field work 2006, Pa per 2007-1 331

Co lum bia; in Geo log i cal Field work 2002, BC Min is try ofEn ergy, Mines and Pe tro leum Re sources, Pa per 2003-1,pages 257–264.

Ramsay, J.G. (1967): Fold ing and Frac tur ing of Rocks; McGraw-Hill, New York, 567 pages.

Read, P.B., Brown, R.L., Psutka, J.F., Moore, J.M., Journeay, M.,Lane, L.S., Or chard, J.J. (1989): Ge ol ogy, More and For restKerr creeks (parts of 104B/10, 15, 16, and 104G/1, 2); Geo -log i cal Sur vey of Can ada, Open File 2094, scale 1:50 000.

Roth, T., Thomp son, J.F.H. and Barrett, T.J. (1999): The pre ciousmetal-rich Eskay Creek de posit, north west ern Brit ish Co -

lum bia; Chap ter 15 in Vol ca nic-As so ci ated Mas sive Sul fideDe pos its: Pro cesses and Ex am ples in Mod ern and An cientSet tings, Barrie, C.T. and Hannington, M.D., Ed i tors, Re -views in Eco nomic Ge ol ogy, vol ume 8, pages 357–373.

Waldron, J.W.F., Gagnon, J-F., Loogman, W. and Evenchick, C.A.(2006): Ini ti a tion and de for ma tion of the Ju ras sic Cre ta -ceous Bow ser Ba sin: im pli ca tions for hy dro car bon ex plo ra -tion in north-cen tral BC; in Geo log i cal Field work 2005, BCMin is try of En ergy, Mines and Pe tro leum Re sources, Pa per2006-1 and Geoscience BC, Re port 2006-1, pages 347–360.

332 Geoscience BC, Re port 2007-1