Micropaleontological Dating - Red Ciencia Cuba · 2018-11-17 · Micropaleontological Dating of the Collision Between the North American Plate and the Greater Antilles Arc in Western

RESEARCH REPORTS 133

Micropaleontological Dating of the

Collision Between the North American

Plate and the Greater Antilles

Arc in Western Cuba

TIMOTHY J. BRALOWER

Department of Geology, University of North Carolina, Chapel Hill, NC 27599-3315

MANUEL A. ITURRALDE-VINENT

Museo Nacional de Historia Natural, Obispo #61, CH 10100, La Habana, Cuba

PALAIOS, 1997, V. 12, p. 133-150

The timing of collision between the Cretaceous Greater An- tilles volcanic arc and the Jurassic-Cretaceous North Amer- ican passive margin is poorly constrained. Previous age estimates range from Late Cretaceous to late Eocene. This wide range results from uncertainty of tectonic reconstruc- tions, lateral migration of tectonic activity and paucity of accurate age information. We present nannofossil and foraminiferal biostratigraphic data from outcrops and sections in western Cuba, synthesized with previous age information, and propose a latest Paleocene to early Eocene age (nannofossil Zones NP9 to NP13; 50-56 m.a.) for terminal collision in western Cuba. This age estimate is obtained from the biostratigraphy of pre- and syn-collisional sedimentary rocks in the Guaniguanico tectonic unit, part of the original North American Plate, and syn- and post-collisional sedimentary rocks in the Bahia Honda and Los Pa- lacios tectonic units, which were part of the GreaterAntilles Arc. Our data indicate that the collision took place over 20 m.y. after the extinction of the arc, and, therefore, that these events were unrelated. Most outcrops studied have a limited stratigraphic extent, preventing the delineation of complete zonal units. However, we show that sub-zonal biostratigraphic resolution can be obtained using the presence and absence of numerous non-zonal markers.

INTRODUCTION

Unraveling the geological history of intensely folded and deformed rocks of active margin settings represents a significant problem. A large part of this problem arises

from difficulty in dating individual units that have com- monly been subjected to significant temperatures and pressures so that most aragonitic, calcitic, and organic- walled fossil material has been heavily altered or entirely destroyed. Yet these active margin areas hold some of the most fascinating geological answers, and even the crudest age control can often shed light on the tectonic evolution of large regions.

The tectonic evolution of the Caribbean-Gulf of Mexico region is a subject of considerable uncertainty and contro- versy. The boundaries of the Caribbean and the North American (hereafter referred to as NOAM) plates have changed significantly in the last 100 million years (e.g., Pindell and Barrett, 1990; Sawyer et al., 1991). Cuba is now part of NOAM, but most of this island has been derived from elsewhere. This island records in its complex geology several tectonic units that have different origins; these include the southern paleomargin of the Bahama platform, tectonic terranes derived from the Yucatan bor- derland, Cretaceous and Paleogene island arc complexes, Mesozoic ophiolites, and Late Tertiary neoautochthonous units (Iturralde-Vinent, 1994a, b). The Cuban segment of the Greater Antilles Cretaceous Arc (hereafter referred to as GAKA) existed from Early Cretaceous (Aptian?) to Late Cretaceous (mid Campanian) time, and collided with NOAM in the Paleogene. The collisional process between GAKA and NOAM not only led to the construction of the major Cuban foldbelt, but also to foreland basins on NOAM and piggyback basins on GAKA (Iturralde-Vinent 1994a).

This study concerns Paleogene sections in three basins in westernmost Cuba and their record of the collisional events (Fig. 1). Because these basins, along with their

Copyright ? 1997, SEPM (Society for Sedimentary Geology)

RESEARCH REPORTS 133

0883-1351/97/0012-0133/$3.00

BRALOWER & ITURRALDE-VINENT

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FIGURE 1-Simplified tectonic map and schematic cross section of northwestern Caribbean region, showing major tectonic features discussed in text (Modified from Rosencrantz, 1990, and Pushcharovsky et al., 1989).

134

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DATING NORTH AMERICAN-GREA TER ANTILLES COLLISION

basement, are structurally separated from one another, we refer to them as tectonic units, or simply as units. The Guaniguanico unit was formed on the original NOAM, and the Los Palacios and Bahia Honda units were formed on the extinct GAKA. The Los Palacios unit is separated from the Guaniguanico unit by the Pinar Fault, which shows largely strike-slip motion. The Bahia Honda unit has been thrust from the south-southeast over the Guani- guanico unit (Hatten, 1957; Pszczolkowski, 1994). A fourth basin, the La Coloma-Sabana Grande Basin, was also formed on GAKA, but it is not part of this study because it is currently submarine.

The Guaniguanico unit shows a fold-thrust style of deformation, in which several thin-skinned thrust sheets were emplaced north- and northwestward, partially over autochthonous Mesozoic-Cenozoic Gulf of Mexico deposits. The pile of thrust sheets was later folded into an anticline whose hinge plunges northeastward and is cut by the Pi- nar fault along its southern limb (Fig. 1). The Guaniguan- ico sedimentary rocks tend to be intensely deformed and partially metamorphosed (Rigassi-Stider, 1963; Pardo, 1975). Those of the Los Palacios and Bahia Honda units tend to be unmetamorphosed and broadly folded, in other words, much less intensely deformed. This difference in structural style is due to the position of the basins at the time of collision. The Guaniguanico foreland basin lay at the collisional front, whereas the Los Palacios and Bahia Honda piggyback basins evolved above the allochthon.

Establishing the timing of collision is one of the critical facets of reconstructing the tectonic history of western Cuba. Although clearly this collision happened at different times for different terranes, little precise age information is available. Post-collisional, Paleogene sedimentary rocks in Cuba have received a great amount of attention from microfossil biostratigraphers, particularly in the Havana area, where sections serve as types for several microfossil zones (e.g., Martini, 1971), and where numerous planktonic foraminiferal and nannofossil species have been originally described (e.g., Bronnimann and Stradner, 1960). Pre- and syn-collisional sediments, however, are more difficult targets for biostratigraphic study because of their more lithified and sometimes deformed nature. Age control of these units is based on planktonic foraminiferal biostratigraphy of isolated outcrops and core samples (e.g., Piotrowski, 1987; Fernandez et al., 1992). Almost no calcareous nannofossil biostratigraphy has been carried out on the Paleogene of western Cuba, and there has been little in the way of stratigraphic synthesis.

In this investigation, we identify the sedimentary events related to the collision of both the foreland and piggyback basins, and identify and date pre-, syn- and post- collisional deposits using stratigraphic and micropaleon- tologic tools.

STRATIGRAPHY OF THE TECTONIC UNITS INVESTIGATED

The tectonic units that we investigated originated in different places and, hence, have separate stratigraphies

- SOUTHEAST E

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------ Direction of tectonic Iransport

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____ O

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61

FIGURE 2-Stratigraphic chart for the Uppermost Cretaceous-Eocene tectonic units and belts discussed in text. Foraminiferal zones are from Berggren and Miller (1988) as revised by Berggren et al. (1995). Ages are from Berggren et al. (1995). The stratigraphic units are of forma- tional level unless indicated. The sections are organized from SE to NW according to their restored positions before thrusting.

(Fig. 2). The stratigraphy and tectonic relationships of the Bahia Honda tectonic unit have been discussed by Hatten (1957), Furrazola et al. (1964), Pszczolkowski and Albear (1982), and Pushcharovski et al. (1989). The Paleogene section of the Bahia Honda unit is underlain by deformed ophiolites, Cretaceous (Albian-mid Campanian) calc-alka- line volcanics, pyroclastic and epiclastic deposits, and upper Campanian-Maastrichtian sedimentary rocks. The Paleogene section has been divided into the Vibora Group (well-stratified conglomerate, sandstone, siltstone and claystone, usually with slumped and olistostromic inter- vals), the Capdevila Formation (well-bedded sandstone, claystone and siltstone, with minor intercalations of conglomerate), the Universidad Formation (hemipelagic marl, radiolarian marl and marly limestone, with rare in- tervals of siltstone toward the base), and the Punta Brava Formation (hemipelagic marl and marly limestone; Push- charovski et al., 1989). The boundary between the Vibora Group and the Cretaceous volcanic sequence is either an angular unconformity or a fault; the Vibora Group and the Capdevila and Universidad Formations are conformable,

135

o a) oC c f\ CN m

z

-1 cr

-1

rr

Ll

136 BRALOWER & ITURRALDE-VINENT

FIGURE 3-Generalized geologic map of western Cuba (modified from Pushcharovski et al., 1989), showing distribution of uppermost Cre- taceous and Paleogene stratigraphic units. Sampled sites, deep well locations and pertinent geographical information are included.

but the Punta Brava Formation unconformably overlies these older units (Fig. 2; Bronnimann and Rigassi, 1963; Pszczolk6wski and Albear, 1982; Albear and Iturralde-Vi- nent, 1985). Clastic rocks of the Vibora and Capdevila yield abundant debris derived from the erosion of the extinct volcanic arc (Pszczolkowski and Albear, 1982; Cobiel- la and Hernandez, 1990).

The stratigraphy of the Los Palacios tectonic unit (Figs. 1-3; Pushcharovski et al., 1989) has been described by Furrazola et al. (1964), Garcia-Sanchez (1978), Piotrowski (1987), and Garcia et al. (1989). This unit is not well exposed, and much of the stratigraphy is known from petroleum exploration wells. In syntheses of the geology of Cuba, the unit is shown to be underlain by Cretaceous volcanic arc rocks (e.g., Furrazola et al., 1964), yet unequivo- cal volcanic arc rocks have not been recovered (Garcia et al., 1989; Iturralde-Vinent, 1994a, b).

Upper Cretaceous and Paleogene rocks of the Los Pala- cios unit crop out along a narrow belt parallel to the Pinar fault. The Paleogene succession in the Los Palacios unit is represented by the Vibora Group, and the Capdevila, Universidad, and Loma Candela Formations (Fig. 2; Pio- trowski, 1987; Garcia et al., 1989). These rocks are slightly to moderately deformed, with deformation intensifying

near the Pinar fault (Fig. 1). The clastic component is derived from the erosion of GAKA, and includes several types of siliceous plutonic and volcanic arc rocks (Echev- arria et al., 1988). The lithology and age of the Vibora Group and the Capdevila and Universidad Formations in this unit are comparable with those in the Bahia Honda unit (Piotrowski, 1987; Alvarez Sanchez, 1989; Garcia et al., 1989).

The stratigraphy of the Guaniguanico tectonic unit has been described in detail by Hatten (1957), Herrera (1961), Pardo (1975), and Pszczolkowski (1978, 1987, 1994). The Paleogene deposits have been subdivided into three belts-Northern Rosario, Southern Rosario and Los Or- ganos (Figs. 1-3), following Pszczolk6wski (1994). Paleo- gene sedimentary rocks in Guaniguanico are related to the evolution of a foreland basin. These deposits can be separated into three main lithological units (Fig. 2)-La Guira sharpstone (breccias and conglomerates), Anc6n Forma- tion (pelagic limestone), and Manacas Formation. Follow- ing Pszczolk6wski (1978, 1994), the Manacas Formation is subdivided into the underlying Pica Pica member (siliciclastic rocks) and the overlying Vieja Member (olistostrome).


METHODS

The current investigation is based on field observations and the examination of over 600 samples collected at 50 locations in western Cuba between July and September, 1992. We carried out a very detailed sampling at all locations because of an anticipated paucity of fossiliferous samples. This strategy worked well in several locations where only one or two samples are fossiliferous. Litholo- gies collected include limestone, marlstone, shale and chalk. Smear slides were prepared using the technique described by Monechi and Thierstein (1985) for hard lithologies. Thick slides were made because of the rarity of nannofossils in many samples. All slides were observed in a transmitted light microscope at magnifications of 600 x and 1000x. Relative abundances were assigned to each occurrence based on the number of specimens observed per field of view according to the following scheme: an occurrence was described as abundant if more than 10 specimens were observed in each field; common if one to ten specimens were observed in each field; few if one to nine specimens were observed in ten fields of view; and rare if less than one specimen was observed in ten fields of view. The nannofossil taxonomy applied in this investigation (Table 1) is discussed and illustrated in Bralower and Mutterlose (1995). Minor differences with the previous scheme include the following: 1) we separate Sphenolithus moriformis and S. primus; and 2) we use a stricter definition of S. anarrhopus, following concepts summarized in Aubry (1989). We use an informal name, S. "preanarrhopus," for forms with a poorly developed spine, which were included in S. anarrhopus in Bralower and Mutterlose (1995).

Traditional Paleogene nannofossil biostratigraphy is based upon a series of zonal and subzonal units. Zonations were established mostly in low- and mid-latitude land sections, including Cuba (e.g., Martini, 1971), and DSDP sites (e.g., Bukry, 1973, 1975; Okada and Bukry, 1980), several of which lie in the Caribbean. These zonations are largely based upon diagnostic taxa that can be observed in sequences that were deposited in a variety of different paleo- geographic locations and contain nannofossils represent- ing a range of different preservational states. Durations of original zonal units vary between 1 and 3 m.y. Numerous non-zonal events, or biohorizons, have been used to provide additional biostratigraphic information (e.g., see com- pilation of Perch-Nielsen, 1985). These markers are particularly useful in the absence of zonal taxa. The large number of Paleogene Deep Sea Drilling Project (DSDP)/ Ocean Drilling Program (ODP) sequences recovered since original zonations were proposed provide a great amount of new biostratigraphic information, especially concerning other potentially useful biohorizons. These data have recently been synthesized by Bralower and Mutterlose (1995), who have compiled some 140 potentially useful nannofossil events in a mid-Paleocene to upper Eocene section from ODP Site 865 in the central Pacific. The order of some 75 of these events has been compared with other sites showing remarkable similarities. This scheme has

TABLE 1-Calcareous nannofossil taxa identified.

Birkelundia staurion (Bramlette and Sullivan, 1961) Perch- Nielsen, 1971

Braarudosphaera bigelowii (Gran and Braarud, 1935) De- flandre, 1954

Bramletteius serraculoides Gartner, 1969 Calcidiscus protoannulus (Gartner, 1971) Loeblich and

Tappan, 1978 Campylosphaera dela (Bramlette and Sullivan, 1961) Hay

and Mohler, 1967 Campylosphaera eodela Bukry and Percival, 1971 Chiasmolithus bidens (Bramlette and Sullivan, 1961) Hay

and Mohler, 1967 Chiasmolithus californicus (Sullivan, 1964) Hay and Moh-

ler, 1967 Chiasmolithus consuetus Bramlette and Sullivan, 1961 Hay

and Mohler, 1967 Chiasmolithus danicus (Brotzen, 1959) Hay and Mohler, 1967 Chiasmolithus eograndis Perch-Nielsen, 1971 Chiasmolithus gigas (Bramlette and Sullivan, 1961) Ra-

domski, 1968 Chiasmolithus grandis (Bramlette and Riedel, 1954) Ra-

domski, 1968 Chiasmolithus nitidus Perch-Nielsen, 1971 Chiasmolithus solitus Bramlette and Sullivan, 1961 Chiastozygus ultimus Perch-Nielsen, 1981 Coccolithus crassus Bramlette and Sullivan, 1961 Coccolithus pelagicus (Wallich, 1877) Schiller, 1930 Coronocyclus niticens (Kamptner, 1963) Bramlette and Wil-

coxon, 1967 Cruciplacolithus asymmetricus, van Heck and Prins, 1987 Cruciplacolithus cribellum Bramlette and Sullivan, 1961 Cruciplacolithus primus Perch-Nielsen, 1977 Cruciplacolithus tenuis (Stradner, 1961) Hay and Mohler in

Hay et al., 1967 Cruciplacolithus vanheckii Perch-Nielsen, 1984 Cruciplacolithus sp. Cyclagelosphaera alta Perch-Nielsen, 1979 Cyclicargolithus spp. Discoaster barbadiensis Tan, 1927 Discoaster bifax Bukry, 1971 Discoaster binodosus Martini, 1958 Discoaster boulangeri Lezaud (1968) Discoaster deflandrei Bramlette and Riedel, 1954 Discoaster diastypus Bramlette and Sullivan, 1961 Discoaster elegans Bramlette and Sullivan, 1961 Discoaster falcatus Bramlette and Sullivan, 1961 Discoaster gemmifer Stradner, 1961 Discoaster germanicus Martini, 1958 Discoaster kuepperi Stradner, 1959 Discoaster lodoensis Bramlette and Riedel, 1954 Discoaster mohleri Bukry and Percival, 1971 Discoaster multiradiatus Bramlette and Riedel, 1954 Discoaster nobilis Martini, 1961 Discoaster saipanensis Bramlette and Riedel, 1954 Discoaster salisburgensis Stradner, 1961 Discoaster sublodoensis Bramlette and Sullivan, 1961 Discoaster tanii Bramlette and Riedel, 1954 Ellipsolithus distichus (Bramlette and Sullivan, 1961) Sul-

livan, 1964

137


TABLE 1-Continued.

Ellipsolithus lajollaensis Bukry and Percival, 1971 Ellipsolithus macellus (Bramlette and Sullivan, 1961) Sul-

livan, 1964 Ericsonia cava (Hay and Mohler, 1967) Perch-Nielsen, 1969 Ericsonia formosa (Kamptner, 1963) Haq, 1971 Ericsonia subpertusa Hay and Mohler, 1967 Fasciculithus involutus Bramlette and Sullivan, 1961 Fasciculithus magnicordis Romein, 1979 Fasciculithus pileatus Bukry, 1973 Fasciculithus stonehengei Haq and Aubry, 1981 Fasciculithus tympaniformis Hay and Mohler in Hay et al.,

1967 Fasciculithus ulii Perch-Nielsen, 1971 Heliocosphaera heezenii Bukry, 1971 Helicosphaera lophota Bramlette and Sullivan, 1961 Helicosphaera seminulum Bramlette and Sullivan, 1961 Lophodolithus mochloporus Deflandre in Deflandre and

Fert, 1954 Lophodolithus nascens Bramlette and Sullivan, 1961 Markalius inversus (Deflandre in Deflandre and Fert, 1954)

Bramlette and Martini, 1964 Micrantholithus spp. Nannotetrina fulgens (Stradner, 1960) Achuthan and Strad-

ner, 1969 Nannotetrina sp. Neochiastozygus chiastus (Bramlette and Sullivan, 1961)

Perch-Nielsen, 1971 Neochiastozygus distentus (Bramlette and Sullivan, 1961)

Perch-Nielsen, 1971 Neochiastozygus eosaepes Neochiastozygus junctus (Bramlette and Sullivan, 1961)

Perch-Nielsen, 1971 Neochiastozygus modestus Perch-Nielsen, 1971 Neochiastozygus perfectus Perch-Nielsen, 1971 Neococcolithes dubius (Deflandre, 1954) Black, 1967 Neococcolithes protenus (Bramlette and Sullivan, 1961)

Black, 1967 Neocrepidolithus bukryi Perch-Nielsen, 1981 Neocrepidolithus sp. Placozygus sigmoides (Bramlette and Sullivan, 1961) Rom-

ein, 1979 Pontosphaera spp. Prinsius bisulcus (Stradner, 1963) Hay and Mohler, 1967 Prinsius dimorphosus (Perch-Nielsen, 1969) Perch-Nielsen,

1977 Prinsius martinii (Perch-Nielsen, 1969) Haq, 1971 Reticulofenestra dictyoda (Deflandre in Deflandre and Fert,

1954) Stradner in Stradner and Edwards, 1968 Reticulofenestra hillae Bukry and Percival, 1971 Reticulofenestra umbilicus (Levin, 1965) Martini and Ritz-

kowski, 1968 Rhabdosphaera spp. Sphenolithus anarrhopus Bukry and Bramlette, 1969 Sphenolithus conspicuus Martini, 1976 Sphenolithus editus Perch-Nielsen in Perch-Nielsen et al.,

1978 Sphenolithus furcatolithoides Locker, 1967 Sphenolithus moriformis (Bronnimann and Stradner, 1960)

Bramlette and Wilcoxon, 1967

TABLE 1-Continued.

Sphenolithus orphanknollensis Perch-Nielsen, 1971 Sphenolithus primus Perch-Nielsen, 1971 Sphenolithus radians Deflandre in Grass6, 1952 Sphenolithus spiniger Bukry, 1971 Thoracosphaera operculata Bramlette and Martini, 1964 Toweius callosus Perch-Nielsen, 1971 Toweius eminens (Bramlette and Sullivan, 1961) Perch-

Nielsen, 1971 Toweius gammation (Bramlette and Sullivan, 1961) Rom-

ein, 1979 Toweius pertusus (Sullivan, 1965) Romein, 1979 Tribrachiatus contortus (Stradner, 1963) Bukry, 1972 Tribrachiatus orthostylus Shamrai, 1963 Triquetrorhabdulus inversus (Bukry and Bramlette, 1969)

Wise in Wise and Constans, 1976 Zygodiscus adamas Bramlette and Sullivan, 1961 Zygodiscus bramlettei Perch-Nielsen, 1981 Zygrhablithus bijugatus (Deflandre in Deflandre and Fert,

1954) Deflandre, 1959

proven to be useful in the current study in two ways. First, we have been able to assign relative positions (i.e., lower, middle, upper) within zones in locations with a limited stratigraphic range, where first and last occurrences cannot be determined. Second, we have been able to detect the presence of mixing by reworking of nannofossil assemblages of closely similar ages.

In using the biostratigraphy of Site 865 in this way, we do not propose that this site become a reference section for the Paleogene. However, there are few other tropical sites in which the order of secondary markers has been established in as much detail. We point out disparities between Site 865 and other sections wherever relevant. Several of the formations studied, particularly the Anc6n and Man- acas, are characterized by extremely impoverished nannofossil assemblages. In these units, age estimates are often based on the presence and absence of one or two of the most resistant markers. We feel this is reliable given the ranges and resistance of these taxa.

In locations where biostratigraphic control could not be obtained using calcareous nannofossils, thin sections or washed samples were prepared for observations of planktonic and benthic foraminifera. These groups were investigated by Gena Fernandez (CIDP-Cuba), Richard Flue- geman (Ball State University), Edward Robinson (Univer- sity of West Indies), and William Sliter (USGS). Absolute ages of units were obtained using the time scales of Berg- gren et al. (1995) for the Paleogene and Gradstein et al. (1994) for the Cretaceous.

PALEOGENE BIOSTRATIGRAPHY OF THE BASINS

We present summary biostratigraphic diagrams (Figs. 4, 5) and range charts for 20 locations that cover a considerable stratigraphic range (Figs. 6-9). In general, the Ba-

138


NANNOZONE

GUANIGUANICO BAHIA HONDA PLANK. LOS PALCIOS FORAM MARTIN BUKRY BIOHORIZON AGE

(71) (73,75)

1-2 1-12 1 Tribrachiatus bramlettei

P5

:2EI sI~ ~ NP9 CP8

Discoastermultiradiatus Fasciculithus involutus LU

CP7 Prinsius spp. 1 Neocrepidolithus bukryi

NP7/8 ' Discoaster nobilis

P4

CP6

, Discoaster mohleri

NP6 CP5 - Chiasmolithus danicus

Fasciculithus pileatus

, Hellollthus klelnpellil

1-35 _____ NP5 CP4

1-16 -58 1-148 Z 11

l"16 _| ''I4,8 P3 IF. tympaniformis ^

gj | ~1-4 3,4 ~4 |E '? PS. "preanharropus" L

I < | . I t -- --- _ Fasciculithus pileatus, F. magnicordis uj

n| P2 NP4 CP3 J Sphenolithus primus

, Elllpsolithus macellus

NP3 CP2 - Prinsius martinii i

P1 I Chiasmollthus danicus

NP2 b CP1

I- 14 _____ ? Cruciplacollthus tenuis

oI| NP1 a a Cruciplacolithusprimus

i Cretaceous species CRET

FIGURE 4-Summary of the biostratigraphy of Paleocene sequences investigated from Guaniguanico, Los Palacios, and Bahia Honda units. On right is tabulated the scheme of biohorizons and their correlation with zones of Martini (1971), Bukry (1973, 1975), and Okada and Bukry (1980) established at ODP Site 865 (Bralower and Mutter- lose, 1995). Foraminiferal zones are after Berggren and Miller (1988) as modified by Berggren et al. (1995). At left is shown the biostratigraphic extent of the locations studied based on the presence and absence of markers (see text and Figs. 6, 7, 9 for details).

ZONE ZONE BAHIA HONDA- ZONE ZONE LOSPBAHIALAIO MARTINI BUKRY BIOHORIZON AGE LOS PALACIOS (7375) (71) (73,75)

NP16 1-49B 1-50 i a

Ia I s s i1 2

CP14 a

-_ Nannotetrina fulgens

'Reticulo. umbilicus -\ Chiasmolithus gigas

- Cruciplacolithus cribellum

- Chiasmolithus gigas

- Discoaster sublodoensis

' Rhabdosphaera Inflata

-J Rhabdosphaera Inflata Nannototrlna fulgens Discoaster lodoensis

1 Reticulofenestra dictyoda Coccolithus crassus

- Chiasmolithus grandis D. sublodoonsis, Cyclicargolithus sp

Trlbrachlatus orthostylus, Helicosphaera lophota, Nannotetrina

sp.

-- Campylosphaera eodela

J C. crassus, H. seminulum

_ Cruciplacolithus cribellum Ellipsolithus macellus

-- Sphenolithus anharropus - Discoaster multiradiatus

Discoaster lodoensis Ericsonia formosa

-Tribrachlatus contortus

- Tribrachiatus bramlettei -i Tribrachiatus orthostylus

-- Tribrachiatus contortus

-- Prinsius bisulcus

w LU

0 0 g s

LU z LU OL O LL

cU

c

b

NP15 3P13

a

b

;P12

-49A I-

1-48

II JS

1-30

-15 1-14A

I I I 0

1-28 '

g

a NP14

NP13

CP1 1

NP12

CP10

NP11 b

NP10 CP9

FIGURE 5-Summary of the biostratigraphy of Eocene sequences investigated from the Los Palacios and Bahia Honda units. On right is tabulated the scheme of biohorizons and their correlation with zones of Martini (1971), Bukry (1973, 1975), and Okada and Bukry (1980) established at ODP Site 865 (Bralower and Mutterlose, 1995). Fora- miniferal zones are after Berggren and Miller (1988) as modified by Berggren et al. (1995). At left is shown the biostratigraphic extent of the locations studied based on the presence and absence of markers (see text and Figs. 6-8 for details).

NP9 CP8

Fasciculithus sp. --lTribrachlatus bramlette L. PAL

139

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FIGURE 6-Calcareous nannofossil biostratigraphy of Los Palacios-Bahia Honda sites. VIB refers to Vibora Group, CV to Capdevila Formation, PB to Punta Brava Formation. Nannofossil abundances are noted with symbols: R-rare, F-few, C-common, A-abundant. See text for explanation of abundances.

hia Honda sites are more nannofossiliferous than those of the Guaniguanico and Los Palacios units.

Bahia Honda Tectonic Unit

In Bahia Honda, our investigations concentrated on dating the Vibora Group, the Capdevila, the Universidad, and the Punta Brava Formations (Figs. 2 and 3), and un- derstanding the relationships between the Guaniguanico and Bahia Honda units.

In order to verify the relationships between the Bahia Honda and the Guaniguanico Paleogene rocks, we measured and sampled a section near Las Terrazas, at sites 1-43/44, where Bahia Honda sediments rest directly on the deformed Guaniguanico unit (Figs. 1 and 3). In these combined locations we found (amongst other lithologies): blocks and slivers of deformed Polier Formation (a Lower Cretaceous Rosario Unit) mixed with deformed sandstone of the Vibora Group (at 1-44); and deformed sandstone belonging to the Vibora Group, which include blocks of foliated serpentinite, chert, and red tuff similar to those of GAKA; and isolated small blocks of the Polier Formation (at 1-43).

Samples from the Vibora Group at site 1-44 contain a sparse nannoflora that includes Sphenolithus primus but no Fasciculithus (Fig. 6), suggesting correlation to the upper part of Zone NP4 (e.g., Romein, 1979; Perch-Nielsen, 1985), which correlates to the uppermost part of the lower

Paleocene or the lowermost part of the upper Paleocene (Fig. 4). A Cretaceous assemblage has been mixed into sediments at this location. Samples from 1-43 contain a similar assemblage indicating a comparable age.

Observations at these sites are indicative of a structural contact between the Bahia Honda sedimentary rocks and the Guaniguanico unit. We consider that the contact is tectonic because: (1) Vibora Group sedimentary rocks (nannofossil Zone NP4 or older) cannot onlap the underlying Guaniguanico unit (Zones NP4-NP13; Fig. 2) because they are the same age or older; (2) sedimentary rocks are more deformed than the Vibora-Capdevila deposits elsewhere in the Bahia Honda basin; and (3) slivers of allochthonous foliated serpentinite and blocks of Guaniguanico deposits are intercalated in the section, as in other locations along this same contact (see Pushcharovski et al., 1989). This kind of tectonic contact, probably a subhorizontal thrust plane, has been documented elsewhere in this area (Albear et al., 1985).

The Vibora Group and the Capdevila and Universidad Formations are exposed at La Pastora (1-14), about 1 km east of 1-43/I-44, where Paleogene clastic sedimentary rocks were reported by Pszczolkowski and Albear (1982; Figs. 3, 7). The lowermost Paleocene is represented by about 20-25 m of well-bedded, medium- to coarse-grained sandstone and siltstone that belong to the Vibora Group. This unit contains a lowermost Paleocene (Zone NP1) nannofossil assemblage, including Cruciplacolithus primus,

140

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FIGURE 7-Calcareous nannofossil biostratigraphy of Location 1-14. CV refers to Capdevila Formation, UN to Universidad Formation. Nan- nofossil abundances are noted with symbols: R-rare, F-few, C-common, ?-questionable occurrence. See text for explanation of abundances.

small Biscutum sp., Chiastozygus ultimus, and Placozygus sigmoides, but no C. tenuis (Figs. 4, 7). A substantial Up- per Cretaceous assemblage has been reworked into these samples. Overlying this unit, probably in tectonic contact, are 30 m of folded and slumped, medium-to coarse-grained sandstone mixed with calcarenite blocks in a matrix of sandy claystone and sandstone, also belonging to the Vi- bora Group. Samples from the matrix (I-14BBB and I-14CCC) possess an abundant and diverse nannofossil assemblage that is assigned to the upper part of Zone NP4 (upper Paleocene; Figs. 4, 7). This assemblage includes Chiasmolithus danicus, Cruciplacolithus primus, C. ed- wardsii, Ellipsolithus macellus, Sphenolithus primus, and Fasciculithus pileatus. A noticeable Upper Cretaceous nannofossil component has also been reworked into this assemblage. A calcarenite block from this slumped section (sample I-14E) contains a mixed Upper Cretaceous-Paleo- cene foraminiferal assemblage including Pseudorbitoides sp. (cf. P. israelkyi), Vaughanina? sp., Sulcoperculina sp., Rotaliid aff. Storrsella sp., Miscellanea (cf. M. sp. 2 of Lep- pig), and Morozovella (sp. aff. M. angulata/acuta group; E. Robinson, pers. comm., 1994).

The transition between the lower Eocene Capdevila and Universidad Formations unconformably overlies the deformed deposits at 1-14. This transition is represented by 15 m of well-stratified marlstone and marly limestone intercalated with sandstone, sandy claystone, siltstone and a few beds of conglomerate. Nannofossil assemblages from Samples I-14ZZ to I-14AA are assigned to lower Eocene

Zone NP12 (Figs. 5, 7). This is indicated by the co-occurrence of Discoaster lodoensis and Tribrachiatus orthostylus in most samples. Occurrence of Coccolithus crassus, Cru- ciplacolithus cribellum, Helicosphaera lophota, and H. seminulum throughout this interval suggests a correlation to the upper part of Zone NP12 (Figs. 5, 7). Two samples in the lower part of the sequence (I-14RR and I-14SS) possess very rare specimens of Discoaster sublodoensis, which ranges from NP14 to NP15. The origin of these specimens is unknown. The base of the Universidad Formation consists of marlstone and marly limestone. The absence of T orthostylus in Sample I-14DD at the top of this section suggests correlation to Zone NP13. A lower Paleocene assemblage including Prinsius dimorphosus and P martinii has been reworked into numerous samples. Samples I-14G, H and I from the transitional Capdevila-Universidad section yield planktonic foraminiferal assemblages belonging to the lower Eocene Morozovella formosa Zone (P7 of Berg- gren and Miller (1988) which is equivalent to nannofossil Zone NP12), while sample J collected near the top of the exposed Universidad Formation contains Planorotalites palmerae (Table 2). This taxon is restricted to lower Eo- cene P. palmerae Zone (P9 of Berggren and Miller (1988) equivalent to nannofossil Zones NP13-14).

Site 1-14 also provides evidence on the nature of the contact between the Bahia Honda and Guaniguanico units. At 1-14, the absence of nannofossil Zones NP2-3 at the base of the deformed interval of Zone NP4 age, and of the Zones NP5-11 at the top, is probably due to the occurrence

141


TABLE 2-Planktonic microfossils of the Capdevila and Universidad Formations in Site 1-14 of Bahia Honda basin.

Capdevila- Univer- Universidad sidad

Microfossils transition Fm.

Acarinina aspensis I J Acarinina pentacamerata G J Acarinina pseudotopilensis H J Globigerina lozanoi I J Morozovella aequa H Morozovella aragonensis G (cf), H J Morozovella formosa G, H Morozovella subbotinae H Pseudohastigerina micra J Pseudohastigerina wilcoxensis G, H Planorotalites palmerae J Planorotalites pseudoscitula J Planorotalites sp. H Lithochytris archaea I Lamptonium chaunothorax I Teocotyle alpha J Teocotyle auctor I Teocotyle ficus I Teocotyle nigrinae I

Samples identified by Gena Fernandez (CIDP, Cupet Cuba).

of subhorizontal thrust planes. Basal sedimentary rocks are unusually deformed and correlate to Zone NP1, older than Paleogene deposits in the Guaniguanico unit (Zones NP4-13).

The Capdevila Formation crops out at site 1-42, located between sites 1-43-44 and 1-14 (Fig. 3). This location also lies in a strongly faulted zone near the contact with the Guaniguanico unit. The section exposes interbedded sandstone, marlstone, and claystone with a few beds of calcarenite. The section is assigned to the upper part of lower Eocene Zone NP10 based on the presence of Tribrachiatus contortus and T orthostylus, and absence of T bramlettei (Fig. 5). This age is consistent with the rest of the assemblage (Fig. 6). Stratigraphically significant absences include Sphenolithus radians and Ericsonia formosa. Most samples observed contain a pervasive reworked lower Pa- leocene assemblage including Prinsius bisulcus, P. dimorphosus, and P. martinii. A sample (I-42X) from one calcarenite bed separated by faults from the previous section was found to yield foraminifera, includingAcarinina (cf.A. bullbrooki) mixed with Ranikotalia catenula, Discocyclina sp., Hexagonocyclina inflata, Miscellanea sp. 1? of Leppig, and Amphistegina? sp. (E. Robinson, pers. comm., 1994). This assemblage also indicates an early Eocene age with reworked Paleocene components.

Two nannofossiliferous samples collected from claystone interbedded with sandstone from the Capdevila at site 1-48 are assigned to lower Eocene Zone NP12 (Figs. 5,

6). This is indicated by the co-occurrence of Discoaster lodoensis, D. multiradiatus, and Tribrachiatus orthostylus.

The transition between the Capdevila and Universidad Formations is well exposed at site 1-15, located a few hun- dred meters to the east of site 1-14 (Fig. 3). This section includes well-bedded marlstone and marly limestone, with a few slumped interbeds of sandstone and sandy marlstone at the base of the section. All samples contain Discoaster lodoensis. Most samples from the bottom half of the section also contain Tribrachiatus orthostylus (Fig. 8) and are assigned to lower Eocene Zone NP12 (Fig. 5). Above sample I-15M, absence of T orthostylus and D. sublodoensis indicates correlation to Zone NP13. Samples in this section contain a similar set of minor markers to samples in Zones NP12 and NP13 at Site 865 (Fig. 8). As in Location 1-14, the combination of Coccolithus crassus, Cruciplacolithus cribellum, Helicosphaera lophota, and H. seminulum in samples I-15BB to M indicates a correlation to the upper part of lower Eocene Zone NP12 (Fig. 8). This is also sug- gested by a single specimen of Nannotetrina sp. in sample I-15BB. Mixed into samples from this sequence are rare specimens of Prinsius bisulcus, P dimorphosus, and P martinii, which indicate minor reworking of a lower Paleo- cene assemblage into the lower Eocene.

The succession of major makers and age of the Capdev- ila Formation observed in this study is similar to that reported by Bronnimann and Stradner (1960) and Bronni- mann and Rigassi (1963) from studies of outcrops in the Havana area. These authors placed the base of this lower Eocene formation in the interval between the first occurrences of Tribrachiatus orthostylus and Discoaster lodoensis. The upper limit of this formation was correlated to within the range of D. lodoensis. The investigations of Br6nnimann and Stradner (1960) and Bronnimann and Rigassi (1963) were carried out prior to the definition of currently applied nannofossil zones (e.g., Martini, 1971), but their ranges incorporate Zones NP10 to NP12. Sam- ples of the Universidad Formation in and surrounding Ha- vana correlate with the Acarinina pentacamerata and Glo- borotalia aragonensis Zones (P8-P9 of Berggren and Mil- ler [1988] equivalent to nannofossil Zones NP12 to NP14). Sanchez Arango et al. (1985) also carried out extensive investigations of planktonic foraminifera in surface and core samples from the Capdevila Formation in the Bahia Hon- da basin, near Bahia Honda and Cabanias, and around the Martin Mesa window (Fig. 3; Table 3). They concluded that the Capdevila Formation correlates with the Globor- otalia rex and G. formosa Zones (P6-P7 of Berggren and Miller [1988] equivalent to nannofossil Zones NP10 to NP12). These results agree with our calcareous nannofossil biostratigraphy of this formation.

Relationships between the Vibora group and Capdevila- Universidad transitional beds with the Punta Brava For- mation can be clearly observed at site 1-49 (Fig. 3). The Vi- bora equivalents consist of strongly weathered sandstone, siltstone, and claystone barren of nannofossils. The overlying Capdevila-Universidad transition consists of interbedded limestone (partially brecciated) and sandstone, with some calcarenite at the base of the unit. Samples

142


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TABLE 3-Planktonic foraminifera reported1 from se- lected samples of the Capdevila Formation, Bahia Hon- da basin (probably some sections of the Vibora group are included).

Samples Foraminifera 4b 4g 6 7 9 12 23 24

Acarinina intermedia X Acarinina pentacamerata X Acarinina pseudotopilensis X X Globigerina collactea X cf Globigerina lozanoi X Globigerina senni X Globigerina soldadoensis X X Globorotalia aequa X X Globorotalia aragonensis X X X X Globorotalia aspensis X cf X Globorotalia broedermanni X X Globorotalia conicotruncata cf Globorotalia convexa X X Globorotalia formosa X X X Globorotalia marginodentata X X X Globorotalia rex X X X Globorotalia quetra X Globorotalia simulatilis X Pseudohastigerina micra X

1 Sanchez Arango et al. (1985).

from this unit contain a rich nannoflora including Discoas- ter lodoensis and Tribrachiatus orthostylus, and are assigned to lower Eocene Zone NP12. The combination of Coccolithus crassus, Cruciplacolithus cribellum, Helicos- phaera lophota, and H. seminulum indicates a correlation to the upper part of this zone (Figs. 5, 6). The upper part of the section at 1-49 consists of marly limestone and marlstone belonging to the Punta Brava Formation (Bronni- mann and Rigassi, 1963), and represents a younger interval than found in previous sites. Samples from these sediments contain Nannotetrina fulgens, Reticulofenestra umbilicus, and a variety of other markers (Figs. 5, 6) suggesting correlation to the lower part of middle Eocene Zone NP16. Samples close to the base of this section possess very sparse nannofloras. A minor change in dip is observed between the Capdevila and the Punta Brava For- mations; this represents an angular unconformity, described within this area by Bronnimann and Rigassi (1963) and Pszczolk6wski and Flores (1986), which includes nannofossil Zones NP14 and NP15.

The unconformity between the Capdevila and Punta Brava Formations is also exposed at site 1-50 in a small quarry northeast of site 1-49 (Fig. 3). Nannofossil biostratigraphy of samples collected at this location indicate correlation to middle Eocene nannofossil Zone NP16, the same age as site 1-49 (Figs. 5, 6). These data indicate that in the Bahia Honda basin, middle Eocene units unconformably overlie Vibora-Capdevila-Universidad deposits.

In summary, the Bahia Honda Paleogene section includes clastic sedimentary rocks of the Vibora Group of Paleocene age (nannofossil Zones NP1-NP4), clastic rocks

143

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of the Capdevila Formation of early Eocene age (nannofossil Zones NP10-12), and hemipelagic limestone and marlstone of the Universidad Formation of early Eocene age (nannofossil Zones NP12-13). The absence of Zones NP5- 9 may not be due to erosion or non-deposition, but rather to insufficient sampling or poor exposure, because these ages are represented in the Havana-Matanzas area (Bron- nimann and Rigassi, 1963; Albear and Iturralde-Vinent, 1985; Sanchez Arango et al., 1985). The top of the Univer- sidad Formation has not been observed because it is eroded throughout the field area, but elsewhere this unit extends up into Zone NP14. The transition between clastic and hemipelagic deposition took place within the late part of early Eocene Zone NP12. The age of the hemipelagic Punta Brava Formation (Zone NP16) at Locations 1-49 and 1-50 is clearly younger than the other lithologic units investigated (Figs. 2, 5).

Los Palacios Tectonic Unit

We measured and sampled several sections (Fig. 3) in the Los Palacios unit in order to date the different formations and to verify the correlations with the Bahia Honda sedimentary rocks. However, no Paleocene nannofossiliferous samples were recovered from any locality in this area.

The entire Paleocene sequence is reported in the Las Mangas well (Fig. 3), including greywacke, calcareous sandstone, sandy limestone, and marlstone yielding planktonic microfossils (Garcia et al., 1989). Other wells (Fig. 3) have penetrated about 100 m of upper Paleocene marly limestone, siltstone, and conglomerate, lithological- ly similar to the Vibora Group, lying unconformably on Cretaceous rocks (Fernandez et al., 1988). The lower Pa- leocene is missing in these wells.

Well-bedded, fine- to coarse-grained sandstone interbedded with thick layers of poorly-sorted conglomerate of the Vibora Group, presumably of Paleocene age, crop out at sites 1-25 and 1-26 (Fig. 3), but we did not find any nannofossiliferous samples. A limestone clast from the former section contains a poorly-preserved Upper Cretaceous (probably Maastrichtian) planktonic foraminiferal assemblage (W. Sliter, pers. comm., 1994). An outcrop of 800 meters of "wildflysch" and olistostromes, located between sites 1-25 and 1-26 (Fig. 3), was described by Alvarez San- chez (1989). A Paleocene planktonic foraminiferal assemblage with Globorotalia (cf. G. compressa) Morozovella (cf. M. angulata), and Subbotina pseudobulloides was reported from this locality (Alvarez Sanchez, 1989).

Claystone samples of the Capdevila Formation from site 1-30 contain a nannofossil assemblage with Tribrachiatus orthostylus, but without T. contortus and Discoaster lodoensis (Figs. 5, 6), indicating an early Eocene (Zone NP11) age, which is confirmed by the presence of numerous minor markers. Sediments contain a noticeable reworked lower Paleocene assemblage including Prinsius bisulcus, P. dimorphosus, and P martinii.

A slightly younger horizon of the Capdevila Formation was found at site 1-28 (Fig. 3). This locality contains inter-

TABLE 4-Microfossils of the Universidad Formation in the Los Palacios basin.

Fm. Microfossils Universidad

Globigerina aspensis 1 Globigerina colomi 1 Globigerina inaequispira 1 Globigerina lozanoi 1 Globigerina mackannai 2 Morozovella aragonensis 1, 2 Morozovella cf. M. aequa 2 Morozovella cf. M. crassata densa 2 Planorotalites palmerae 1 Globanomalina micra 1 Anomalina aragonensis 1 Tritaxia eucarinata 1 Eoconuloides wellsi 2 Discocylina cf. D. cubensis 2 Discoaster barbadiensis 1 Discoaster binodosus 1 Discoaster crassus 1 Discoaster cruciformis 1 Discoaster elegans 1 Discoaster geometricus 1 Discoaster lenticulatus 1 Discoaster lodoensis 1 Discoaster quinarius 1 Discoasteroides kuepperi 1 Masthasterites tribrachiatus 1

1. Loc. 12 of Furrazola-Bermudez & Kreisel (1992), 2. Piotrowski (1987).

bedded sandstone, siltstone, and claystone. A lower Eo- cene Zone NP12 assignment is indicated by the co-occurrence of Discoaster lodoensis, Tribrachiatus orthostylus, and various secondary markers (Fig. 6). The rarity ofD. lodoensis, the presence of Campylosphaera eodela and Ellip- solithus macellus, and the absence of Cruciplacolithus cribellum (in all but one sample), Helicosphaera lophota and H. seminulum indicate that this section belongs to the lower part of Zone NP12 (Figs. 5, 6). A single specimen of Tri- brachiatus contortus in sample 11 is probably reworked. As in other locations, there is a reworked lower Paleocene nannofossil component (Fig. 6).

We were unable to sample sections of the Universidad Formation in the Los Palacios basin, but the unit was described by Piotrowski (1987) as thin-bedded marlstone and marly limestone, with some intercalations of fine- grained calcarenite. According to Piotrowski (1987), these rocks yield upper lower Eocene to lower middle Eocene planktonic foraminifera (Table 4). Furrazola-Bermuidez and Kreisel (1972) reported an assemblage ofnannofossils and planktonic foraminifera of early Eocene age (Acarini- na pentacamerata [P9] Zone Berggren and Miller [1988], equivalent to Zones NP13-14, Table 4) from a section at Rio Hondo (Fig. 3).

144


The Loma Candela Formation unconformably overlies the Universidad Formations in wells and outcrops (Pio- trowski, 1987; Fernandez et al., 1988). The Loma Candela is composed of conglomerate interbedded with shallow- water skeletal and biostromal limestone. The conglomerate contains abundant pebbles of Guaniguanico limestone and GAKA igneous rocks. Thus, the Loma Candela is in- terpreted as post orogenic, laid down when the Guani- guanico unit was already deformed and uplifted (Pio- trowski, 1978). We collected samples for age determina- tion from site 1-53 (Fig. 3). The limestone contains the following lower middle Eocene benthic foraminifera- Amphistegina parvula, A. sp. aff. A. praegrimsdalei, Pa- leonummulites floridensis, Nummulites striatoreticulatus, Stenocyclina (cf. S. advena) Eofabiania grahami, Fabiania cassis, Caudriella ospinae, Eulinderina guayabalensis, Cushmania americana, Polylepidina chiapasensis?, Pro- porocyclina sp., Eorupertia sp., Halkyardia? sp., Rotalia sp. A, Lepidocyclina (s.l.) sp. (E. Robinson, pers. comm., 1994).

In summary, dating Paleogene sedimentary rocks in the Los Palacios unit is more difficult than in the Bahia Hon- da, but correlation can be established. Vibora Group equivalents are present and are thought to include the whole Paleocene, though locally the lower Paleocene can be absent (Fernandez et al., 1988). The Capdevila (nannofossil Zones NP11-12) and Universidad (foraminifera equivalent to Zones NP13-14) Formations appear to have similar lower Eocene age ranges as in the Bahia Honda unit and the Havana-Matanzas area. The Loma Candela Formation of middle Eocene age is correlatable with the Punta Brava Formation in the Bahia Honda unit. Because the lithologies and facies of the Paleogene deposits in the Los Palacios and Bahia Honda units are correlatable, these basins appear to be genetically related, as observed in the Havana-Matanzas area where they merge (Fig. 1).

Guaniguanico Tectonic Unit

We sampled Paleogene sedimentary rocks at 29 sites in the Guaniguanico unit, including sections in the Los Or- ganos, and both the Northern and Southern Rosario belts (Figs. 3-5). Results of nannofossil biostratigraphic investigation indicate early to late Paleocene ages (Figs. 4 and 9). The ages and stratigraphic relationships of the Paleo- gene sections in the Guaniguanico unit are summarized in Figure 2. The La Guira member is found only in some locations of the Los Organos belt, while the Anc6n limestone is thickest in the Los Organos, becomes thinner in Southern Rosario, and pinches out in the Northern Rosa- rio belt. In contrast, the Manacas olistostrome thins in the opposite direction (Fig. 2).

One of the oldest Paleogene sections in the Los Organos is exposed at site 1-58 near Pino Sola (Figs. 3, 4, 9). This section contains three lithological units, from base to top: about 70 m of La Giira sharpstone (composed of sub- rounded to subangular pebbles and blocks of Mesozoic limestone and chert cemented by sparry calcite); about 20 m of Anc6n limestone (red, thinly bedded micritic lime-

AA R R F S R R R RR P R R R K R F

D R R

S R R RRRR

C R

KEY

UMESTONE _ SHALE

FIGURE 9-Calcareous nannofossil biostratigraphy of Guaniguanico unit. Zones are those of Martini (1971). MC refers to Manacas For- mation, AN to Ancon Formation. Nannofossil abundances are noted with symbols: R-rare, F-few, ?-questionable occurrence. See text for explanation of abundances.

stone with two 20-cm-thick lenses of calcareous breccia); and about 5 m of Manacas Formation (poorly exposed siliciclastics). Samples from the La Guira member are barren of nannofossils. Samples from the Anc6n limestone are poorly nannofossiliferous, yet age determinations are constrained by the presence and absence of a few resistant marker species (Fig. 9). Samples I-58A and 58B, located toward the top of the Anc6n, contain Fasciculithus tympaniformis and Sphenolithus primus; additionally, sample I-58B contains F. pileatus. These samples belong to the lower part of upper Paleocene Zone NP5 of Martini (1971). Sample I-58C, from 7 meters above the base of the section, contains a similar assemblage with no F tympaniformis. The absence of the latter species indicates that this sample belongs to the upper part of Zone NP4, which correlates to the uppermost part of the lower Paleocene or lowermost part of the upper Paleocene. In this section the stratigraphic position of the La Giira member below the Anc6n Formation suggests an early Paleocene (early Zone NP4 or earlier) age (Fig. 2). Eastward at site 1-54 (Fig. 3), the La Giira Sharpstone is directly overlain by the lower part of the Manacas Formation. Samples from both units

145

I I


are barren of nannofossils, although limestone fragments in La Guira samples I-54A and B contain Early Creta- ceous (lower Valanginian?) calpionellids (W. Sliter, pers. comm., 1994).

An excellent example of the Los Organos Paleogene deposits is exposed at site 1-22, near the village of Moncada. The La Guira member is represented by a 2-m-thick layer of thin-bedded, fine-grained calcarenite. The Ancon For- mation consists of about 18 m of well-bedded, light reddish-violet-green micritic, slaty to sublithographic limestone with interbedded calcarenite. The overlying Pica Pica Member siliciclastics are represented by 15 m of thin- bedded claystone and fine- to medium-grained arkosic and lithoclastic sandstone. The section is capped by more than 30 m of olistostrome, belonging to the Vieja Member, con- taining large blocks embedded in a strongly-deformed sandy-claystone matrix. The blocks, which consist of limestone, chert, basalt, diabase, gabbro and serpentinite, are up to four meters in diameter, coarsening towards the top of the outcrop. The Anc6n Formation is barren of nannofossils but contains planktonic foraminifera. The last occurrence of Morozovella velascoensis occurs in the middle part of the Anc6n, but M. aequa has been observed throughout the section, indicating correlation to the upper part of Zone P5 and the lower part of Subzone P6a of Berg- gren et al. (1995; G. Fernandez and R. Fluegeman, pers. comm., 1995). These zones correlate to the uppermost Pa- leocene and lowermost Eocene and to nannofossil Zones NP9 and NP10. Limestone blocks from the Vieja Member possess a well-developed foliation, are barren of nannofossils, but contain a mixture of Late Cretaceous planktonic foraminifera and large keeled morozovellids indicative of late Paleocene age (W. Sliter, pers. comm., 1994).

At site 1-23 in the Los Organos belt, Anc6n limestones are virtually barren of nannofossils. Sphenolithus primus is noted in several samples (Fig. 9). The occurrence of this species in a sample near the base of the Ancon indicates that this formation here does not range below the upper part of nannofossil Zone NP4 (lowermost upper Paleocene) as in site 1-58 (e.g., Perch-Nielsen, 1985).

Location 1-35 is also in the Los Organos belt (Fig. 3). This section spans the transition between the upper part of the Anc6n limestones and the Manacas Formation. Samples taken in the latter unit are barren of nannofossils. Most of the thirteen samples taken in the Anc6n are sparsely nannofossiliferous (Fig. 9) with assemblages characterized by pervasive overgrowth and etching. The occurrence of early species ofFasciculithus (F pileatus and F ulii) and Fasciculithus tympaniformis in samples from the base (I-35C) and near the top (I-35H) of the section indicates a correlation with the lowermost part of upper Pa- leocene Zone NP5 of Martini (1971; Fig. 4; e.g., Romein, 1979; Perch-Nielsen, 1985). Consistent with this age de- termination are very primitive forms of the species Sphen- olithus primus (few elements) and S. "preanarrhopus" (short spine). Planktonic foraminiferal assemblages in the Anc6n from Section 1-35 include Planorotalites pseudomenardii (G. Fernandez and R. Fluegeman, pers. comm., 1995), the range of which defines upper Paleocene Zone

P4. This long-ranging zone is equivalent to nannofossil Zones NP5 to NP9; however, nannofossil biostratigraphy indicates that the Anc6n Formation at 1-35 lies in the lower part of Zone P4.

In the southern part of the Rosario belts, the Anc6n For- mation is not widespread but is found as blocks in the overlying Manacas olistostrome. One such sample of An- c6n, I-16EE from site 1-16 (Fig. 3), contains Sphenolithus primus, Fasciculithus magnicordis, and F. pileatus, indicating the upper part of Zone NP4, which correlates to the lowermost part of the upper Paleocene (Fig. 4). A sample from a separate block of Ancon contains small early late Paleocene planktonic foraminifera species, lacking the larger late Paleocene keeled morozovellids (W. Sliter, pers. comm., 1994). However, size sorting is observed in this sample. This indicates that the smaller foraminifera may have been winnowed out of the true later Paleocene assemblage and the real age may be somewhat younger.

The Pica Pica member of the Manacas Formation is the siliciclastic unit that overlies and possibly partially correlates with the Anc6n Formation. It was sampled in many localities (Fig. 3). These rocks are largely barren of fossils, but some samples from the Rosario belts were nannofossiliferous. Unfortunately, none of these samples yield a diagnostic assemblage so that little age information could be obtained.

Two fossiliferous samples were recovered (out of 27 taken) from both members of the Manacas Formation exposed at site 1-45 of the Southern Rosario belt (Figs. 3, 9). These samples contain sparse Upper Cretaceous and Pa- leogene nannofossils including Sphenolithus primus. The latter marker ranges from the early part of the late Paleo- cene (upper part of Zone NP4) to early Eocene (Zone NP11; e.g., Aubry, 1989).

One sample of possible matrix from the Manacas olistostrome in the Southern Rosario was recovered from site 1-16. This sample (I-16M, Fig. 9) contains an assemblage of Sphenolithus primus, S. "preanarrhopus" (short spine), and Chiasmolithus danicus. Combined with the absence of Fasciculithus, this assemblage indicates a correlation to the upper part of Zone NP4 of Martini (1971) which correlates to the uppermost part of the lower Paleocene or the lowermost part of the upper Paleocene. As the age of one Anc6n limestone block (contains early species of Fascicu- lithus, indicating uppermost part of Zone NP4) embedded in the olistostrome is younger than the age of the matrix (does not contain Fasciculithus, indicating a lower position within Zone NP4), the nannofossils are probably reworked in the matrix, and the olistostrome is younger than NP4 in this locality.

Both members of the Manacas Formation are also exposed at site 1-46 of the Northern Rosario belt (Fig. 3), but the Ancon Formation is absent. The only nannofossiliferous sample contains a mixed Lower and Upper Cretaceous assemblage (Fig. 9). The only Paleogene species to occur in this sample is Sphenolithus primus, indicating a similar age range (NP4-NP11) to locality 1-45.

Another section that exposes both members of the Man- acas Formation is site I-2 located in the Northern Rosario

146


belt (Fig. 3). Fossiliferous samples are dominated by rare, but moderately well preserved Upper Cretaceous nannofossils (Fig. 9). The Paleogene assemblage is extremely sparse, limited to 1 or 2 specimens in each sample. The most common taxa are Ericsonia subpertusa and Sphen- olithus primus. Age diagnostic species observed are one specimen each of Fasciculithus tympaniformis (zonal range NP5 to NP9) and Neocrepidolithus bukryi in sample I-2S from the matrix of the olistostrome. The latter species ranges from Zone NP8 to NP9 (Perch-Nielsen, 1985). Our data therefore suggest a late Paleocene (Zone NP8 to NP9) age range for the olistostrome (Fig. 4).

We collected samples from a light green-reddish-gray biomicritic limestone block embedded in the Manacas olistostrome from site 1-12, in the Southern Rosario belt (Fig. 3). This lithology is similar to intercalations in the lower Manacas Formation reported by Pszczolk6wski (1994), but can also be a block incorporated from the Anc6n limestones. Sample I-12B (Fig. 9) contains a sparse assemblage with Fasciculithus involutus. The range of this species varies according to the taxonomic concepts utilized. Narrowly defined, it is restricted to Zone NP9 (Romein, 1979); however, if broader taxonomic concepts are applied, the range of this taxon is slightly wider (e.g., Bralower and Mutterlose, 1995). We tentatively assign a late Paleocene (NP9) age to this sample (Figs. 4, 9). Unidentified Paleo- gene globigerinids have been observed in a thin section of the limestone from this outcrop (G. Fernandez, pers. comm., 1994).

Rare limestone fragments from blocks collected in the Vieja member (Manacas Formation) at locations I-2 (sample I-2YY) and 1-16 (sample I-16A) contain a dissolved and poorly-preserved planktonic foraminiferal assemblage. The predominance of small, unkeeled forms suggest a late Paleocene (Subzone P3b-Zone P4) age prior to the occurrence of large keeled morozovellids in the latest Paleocene (W. Sliter, pers. comm., 1994). This is consistent with ages obtained from nannofossil biostratigraphy of blocks in the olistostrome. These limestone blocks may have been derived from the Anc6n Formation, incorporated into the olistostrome during overthrusting.

Hatten (1957) assigned the Manacas Formation to the upper Paleocene based on the presence of questionable occurrences of Morozovella velascoensis. Pszczolk6wski (1978, 1987) carried out investigations of locations in the Los Organos belt. He reported specimens of Morozovella ex. gr. M. velascoensis in the Pica Pica member of the Man- acas Formation, but no age determinations were made due to taxonomic uncertainty. Subsequent studies re- vealed an upper Paleocene to lowermost Eocene planktonic foraminiferal assemblage (Table 5) from the Pica Pica member of the Manacas Formation in the Rosario belts (Pszczolk6wski, 1994). Nannofossil biostratigraphy suggests that the Manacas was deposited in the late Paleo- cene, in Zones NP8 and NP9. This is indicated by single occurrences of Neocrepidolithus bukryi and Fasciculithus tympaniformis in one location and Fasciculithus involutus in another. However, Fernandez et al. (1992) reported Planorotalites palmerae, associated with morozovellids

TABLE 5-Planktonic foraminifera of the Ancon and Manacas Formation1.

Lower Mana-

cas Fm.

South- Ancon Fm. ern Los Organos/

Microfossils Rosario Rosario

Acarinina cf A. soldadoensis? X Acarinina broedermanni ex. gr. ex. gr. ex. gr. Morozovella acuta? cf cf Morozovella aequa X cf cf Morozovella crassata/spinulosa cf Morozovella ex. gr. M. velascoen-

sis-acuta X X X Morozovella pseudobulloides ex. gr. cf cf Morozovella wilcoxensis ex. gr. ex. gr. Planorotalites pseudomenardii cf X X Globigerina chascannona X Morozovella subbotinae ex. gr. "Globorotalia" perclara ex. gr. Planorotalites pseudoscitula/con-

vexa cf Planorotalites compressa X Pseudohastigerina wilcoxensis cf Acarinina soldadoensis cf Chiloguembelina sp. X "Globigerina" triloculinoides ex. gr.

1 Planktonic forams identified by A. de la Torre and A. Pszczol- kowski.

and acarininids in matrix samples from the Manacas For- mation olistostrome, cored in several exploratory wells in the Martin Mesa window of the Northern Rosario belts (Fig. 1), suggesting a late early Eocene age (Zone P9 of Berggren and Miller, 1988).

In summary, the La Guira Sharpstone appears to be of early Paleocene age (older than NP4). The Anc6n Forma- tion may be missing in Northern Sierra del Rosario, is of late Paleocene-earliest Eocene (NP5-NP10) age in the Si- erra de Los Organos, and early late Paleocene (uppermost Zone NP4) in the Southern Sierra del Rosario. The narrow age range of the latter belt is probably due to the limited number of outcrops investigated. A wide range of ages are derived from calcareous nannofossil and planktonic foraminiferal biostratigraphy of matrix and blocks of the Man- acas Formation. Ages obtained from samples of blocks range from early late Paleocene (nannofossil Zone NP4) to late Paleocene (Zone NP9). Some blocks are exotic, derived from limestone of the Anc6n Formation, but others may be disrupted horizons and may have the same age as the matrix. Planktonic foraminiferal biostratigraphy of the outcrops investigated here indicates a late Paleocene age for the Manacas Formation; however, the biostratigraphy of other workers indicates that the age of the matrix extends

147


into the late early Eocene (Planorotalites palmerae Zone (Zone P9 of Berggren and Miller [1988], which is equivalent to Zones NP13-14; Fernandez et al., 1992)). Combi- nation of ages from the youngest blocks and the matrix suggest that the Manacas Formation correlates to the interval from late Paleocene Zone NP9 to early Eocene Zone NP13 (Fig. 2).

DISCUSSION

In order to constrain the timing of collision between the Greater Antilles Volcanic Arc (GAKA) and the continental margin of the North American Plate (NOAM) in westernmost Cuba, we combine sedimentary and tectonic observations with biostratigraphic data.

Sedimentary rocks in the Guaniguanico unit range from Jurassic to lower Eocene. Several disconformities that may be related to submarine erosional events have been identified in these sections (Pszczolk6wski 1978, 1994). The Moreno Formation of late Campanian age includes the first fine-grained debris derived from GAKA to reach the NOAM margin (Pszczolk6wski, 1978,1994), indicating the uplift of the recently extinct volcanic arc and its prox- imity to NOAM. The Anc6n Formation limestones were deposited in a pelagic setting and are pre-collisional. This unit appears to have a considerable age span, from latest early Paleocene (upper part of Zone NP4) to earliest Eo- cene (Zone NP10) based on combined nannofossil and planktonic foraminiferal stratigraphy (Fig. 2). The lack of arc material in the Anc6n indicates that, by the late Paleo- cene, GAKA had been largely eroded. The overlying Man- acas Formation (Zone NP9 to NP13) is thought to be syn- orogenic, constraining the collisional event to the latest Paleocene to early Eocene interval. Evidence for this includes the input of large amounts of allochthonous debris from GAKA in the whole unit, especially the common occurrence of large blocks and whole tectonic sheets within the Vieja Olistostrome, and the sheared and slightly metamorphosed nature of the formation. The end of thrusting in the Guaniguanico unit cannot be determined because the oldest sedimentary cover on top of the allochthon is Oligocene, far younger than the end of this event (Push- charovsky, 1989).

In the Bahia Honda and Los Palacios basins, three un- conformities have been recorded in the post-volcanic section: a Campanian-lower Maastrichtian angular unconformity that coincides with the extinction and uplift of the Cretaceous volcanic arc; disconformities between the uppermost Maastrichtian and lower Paleocene; and within the mid middle Eocene (Albear and Iturralde-Vinent, 1985; Pszczolk6wski and Flores, 1986). Thus, the large- scale folds and faults in the Paleogene sections of the piggyback basins that coincide with strike-slip and vertical movement are mostly post-collisional, late middle Eocene or younger in age. However, it is well known that the Ba- hia Honda and Los Palacios units were thrust over NOAM (Figs. 1 and 3; Hatten, 1958; Pszczolk6wski 1978, 1994; Iturralde-Vinent 1994a, b). This means that the detach- ment surface of the allochthonous units was originally lo-

cated below the bottom of the basins (see cross section in Fig. 1), so that only minor deformation (synsedimentary slumping in the Vibora Group and the Capdevila Forma- tion) occurred during tectonic transport. This deformation occurred sometime within the Paleocene to early Eocene (Zones NP1 to NP12), the age span of these clastic units. Termination of deposition of clastic units may reflect the end of tectonic transport of the basins. This event, recorded by the Capdevila-Universidad transition, is early Eo- cene (Zones NP12-13) in age. Therefore, the Universidad Formation (NP12-14), which yields little fine-grained de- tritus, may be considered as post-collisional. The age of the end of the collision determined in this way overlaps with the youngest age determined for the Manacas Formation in the Guaniguanico unit (Zone P9, which is equivalent to nannofossil Zones NP13-14; Berggren et al., 1995).

In synthesis, the age of the collision between NOAM and the extinct volcanic arc (GAKA) has been established as latest Paleocene (NP9) to early Eocene (NP13). Evi- dence for convergence is recorded since the late Campani- an (77-79 m.a.), but the actual collision took place over 20 m.y. later. This implies that the collision took place long after the termination of volcanic activity in GAKA (Itur- ralde-Vinent, 1994a, b). This stratigraphic information indicates that the extinction of the arc and the collisional process were unrelated, in contrast to the conclusions of Pindell and Barrett (1991) and Pindell (1992).

The biostratigraphic results also provide a direct test of the detailed sequence ofPaleogene nannofossil events proposed by Bralower and Mutterlose (1995) from ODP Site 865 in the equatorial Pacific (Figs. 4, 5). We have applied this scheme to date sections with limited stratigraphic extent with subzonal resolution. The relative order of events in the early Eocene Capdevila and Universidad Forma- tions shows that the Site 865 scheme works well in Cuba. The relative order of three events does appear to differ in Cuba, however, including the first occurrences of Chias- molithus grandis, Reticulofenestra dictyoda, and Cyclage- losphaera sp., all of which lie within Zone NP12 in Cuba but in Zone NP14 in Site 865. These disparities may be a result of a poorly preserved interval within Zone NP12 and a condensed Zone NP13 at Site 865. In other sites, the first occurrences of these three taxa are often below Zone NP14 (see discussion in Bralower and Mutterlose, 1995).

Many of the samples analyzed contain a noticeable reworked component, often of superior preservation to the component presumed to be in situ. This ranges from dom- inantly Cretaceous in age in the Manacas Formation to early Paleocene in the Capdevila Formation and overlying units. In several samples this component completely dom- inates the assemblage, whereas in others it accounts for a minute portion. The case for reworking is clear on stratigraphic grounds for the Manacas Formation, much of the Vibora Group, and the upper part of the Capdevila For- mation, but less obvious in the lower part of the Capdevila. The observation that the nannofossils in particular units are almost entirely reworked represents an interesting sedimentological problem. We propose that by the time that reworking occurred, these older specimens had been

148


overgrown to such an extent that they survived the rede- positional process, and that the absence of in situ nannofossils in these horizons is a result of dissolution of these more fragile specimens during transport and/or deformation.

CONCLUSIONS

Sedimentary rocks deposited or accreted in active margin settings are difficult targets for biostratigraphic investigation. We have shown that nannofossil and foraminiferal biostratigraphy of pre-, syn- and post-collisional units in western Cuba can be used to constrain the timing of deformation and collision. The Guaniguanico unit, the continental margin of the North American plate, collided with terranes previously belonging to the westernmost segment of the Cretaceous Greater Antilles Volcanic Arc (Ba- hia Honda and Los Palacios units) in latest Paleocene to early Eocene time correlating to nannofossil Zones NP9 to NP13. This collision took place a minimum of 20 m.y. after the extinction of the arc. This can be constrained both by impoverished nannofloras and planktonic foraminiferal assemblages in the syn-collisional Manacas Formation and by the bounding ages of pre- and post-collisional An- c6n and Universidad Formations, respectively. The data obtained here also illustrate the applicability of subzonal schemes ofbiohorizons developed for deep-sea sites to dating sections with limited stratigraphic extent on land.

ACKNOWLEDGMENTS

We gratefully acknowledge Paul Mann (Institute for Geophysics, UT at Austin) for supporting this investigation and for guidance at every stage. We thank Paul Mann and Mark Gordon (Rice University) for field assistance, and Joel Bond and Sarah Mock (UNC-CH) for preparing smear slides. We are grateful to Gena Fernandez (Cupet, Cuba), William Sliter (USGS), Richard Fluegeman (Ball State University), and Edward Robinson (University of West Indies) for foraminiferal identification in some key samples. Marie-Pierre Aubry, Jim Dolan, Mark Gordon, Paul Mann, John Rogers, Eric Rosencrantz, and Kevin Stewart reviewed earlier drafts of this manuscript and made helpful suggestions. This research was supported by the Grant NSF-EAR-9205873 to Paul Mann; travel funds to Bralower by the Institute for Geophysics, University of Texas at Austin; and travel funds to M. Iturralde-Vinent by the Institute of Latin American Studies of the Univer- sity of Texas at Austin.

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