TECTONICS, VOL. 12, NO. 2, PAGES 441-459, APRIL 1993

PREBREAKUP GEOLOGY OF THE GULF OF

MEXICO-CARIBBEAN: ITS RELATION TO

TRIASSIC AND JURASSIC RI•T SYSTEMS

OF THE REGION

Peter Bartok

British Petroletun Research, England

Abstract. A review of the prebreakup geology of west central Pangea, comprising northern South America, the Gulf of Mexico, and West Africa, combined with a study of the Mesozoic riff trends of the region confirms a relation between the rift systems and the underlying older grain of deformation. The prebreakup analysis focuses attention on the Precambrian, early Paleozoic, and late Paleozoic tectonic events affecting the region and asstunes a Pindell fit. Two late Precambrian orogenic belts are observed in west central Pangea. Along the northern South American margin and Yucatan a palco northeast trending Pan-African aged fold belt is documented. A second system is observed along West Africa extending from the High Atlas to the Mauritanides and Rockelides. Similar aged orogenies in the Appalachians are compared. During the late Paleozoic, renewed orogenic activity, associated with the Gondwana-Laurentia suture, affected large segments of west central Panget. The general trend of the system is northeast-southwest and essentially parallels the Guayana craton and West African and eastern North American cratons. Mesozoic rifling closely followed either the Precambrian trends or the late Paleozoic orogenic belt. The Triassic component focused along the western portions of the Gulf of Mexico continuing into eastern Mexico and western South America. The Jurassic rift trend

followed along the separation between Yucatan and northern South America. At Lake Maracaibo the Jurassic rift system eventually overlaps the Triassic riffs. The Jurassic rift resulted in the "Hispanic Corridor" that permitted Tethyan and Pacific marine faunas to mix at a time when the Gulf of Mexico underwent continental sedimentation.

INTRODUCTION

The late Paleozoic paleoreconstruction of Pangea, published by Ross and Scotese [1988], Pindell and Dewey [1982], and Pindell [1985] and adjusted to accommodate the work of Dunbar and Sawyer [1987], provides a starting point for developing the sequence of Mesozoic rifting in "west central" Pangea: Gulf of Mexico and Caribbean region (Figure 1). Two problems are the frame for the discussion in this paper: (1) definition of the causes for the rift traces observed in the region and (2) evaluation of the timing and trend of the tectonic features associated with Mesozoic rifting in the focus area. It is necessary therefore to consider both the late Precambrian and mid-Paleozoic geologic setting for the terranes discussed in the present study as well as the region's late Paleozoic history. Special emphasis is placed on northern South America. Intuitive reasoning suggests that if

Copyright 1993 by the American Geophysical Union.

Paper number 92TC01002. 0278-7407/93/92TC-01002510.00

an inherent zone of weakness is present in an area undergoing thermal expansion, rifting will either follow or closely parallel the trace of the zone of weakness. The present study will demonstrate that in west central Pangea there is a persistent relationship between the ancestral tectonic history of the region and the Mesozoic rifling events. For a review of the post-Jurassic tectonic development of the region the reader is directed to the Caribbean review papers by Burke [1988] and Pindell and Barrett [1990]. A recently published correlation chart for the Caribbean province [Maurasse, 1990] may assist readers not familiar with the region's nomenclature.

Three major orogenic events are documented in the prebreakup of west central Pangea: a late Precambrian, an early to middle Paleozoic [Scotese, 1984; Scotese and McKerrow, 1990] (Figure 2), and a late Paleozoic orogeny associated with the Pangea suture (Figure 3). For descriptive purposes the geology of the Precambrian to early Paleozoic of west central Pangea is subdivided into geographic segments, namely, northern South America, Yucatan, West Africa, and Florida.

Mesozoic riffing in west central Pangea is well documented along the seaboard portion of the North American late Paleozoic Alleghanian/Ouachita fold belts lI•tcher et al., 1989]. The western coast of Africa and portions of north- western South America have undergone contemporaneous rifting [Anderson and Schmidt, 1983] (Figure 4). Jurassic rifting generally parallels the onshore Triassic trend and steps out along its present-day seaward side. Few direct control points [Bartok et al., 1985] and several indirect inferences support the southern extension of the Jurassic graben trend, lying between Yucatan and South America [Ross and Scotese, 1988] (Figure 5). Ross and Scotese [1988] suggested that a continuous rift event prevailed in the Gulf of Mexico and Caribbean region from the Triassic to the Jurassic. However, the present study proposes a more episodic rifting system.

The Triassic rift system extends from the Newfoundland and Canadian Atlantic offshore through the Newark graben system, the Carolinas and Georgia [Sheridan, 1989; Manspeizer et al., 1989] (Figure 6). In central Georgia, the trend either widens or splays with the northern branch trending along the Ouachita Mountain front [Vernon, 1970; Walper, 1980]. The southern branch extends along the Suwannee depression of northern Florida and northwestern Yucatan [Salvador, 1987] (Figure 4). The Triassic rift system continues south into eastern Mexico and northwestern South America. Although the nomenclature differs in the various areas, the basic lithologic descriptions of the sequences are quite similar. The Mexican equivalent to the Eagle Mills Formation is the La Boca Formation (lower member of the Huizachal Group [Lopez Ramos, 1983]. In southern Mexico, Yucatan, and northern South America there is some evidence for Triassic sedimentation, but it is much less clearly defined. The Payande rift series of both red bed and marine strata [Burgl, 1963] and the La Ge Group (Tinacoa and Macoita formations [Benedetto and Odreman, 1977], respectively, exemplify these systems in Colombia and Venezuela.

Jurassic rifting was originally inferred from the biotic exchange of Tethyan and Pacific faunas observed in the eastern Pacific region, from western Canada to Peru. Tethyan faunas first lived in the Pacific during the Pliensbachian, at the earliest [Westermann, 1980; Smith, 1983] (Figure 7). This occurred at a time of non marine

442 Bartok: Prebreakup of Gulf of Mexico-Caribbean and Rifting

I NORTH AMERICA[

/ AR / LAURENTI ",4 /

WES T AFRICA

WEST CENTRAL PANGEA

MARACAIBO,•

I ' ! [ I [ ! 200 400 600 800

KM

Fig. 1. General location of the west central Pangea area of study. For Lauentia, abbreviations are T, Texas; L, Louisiana; AR, Arkansas; M, Mississippi; A, Alabama; G, Georgia; F, Florida; SC, South Carolina; SF, South Florida Block; FSB, Florida Straits Block (Bahamas). For South America, abbreviations are YUC, Maya Block (Yucatan); P1L Pinar del Rio (western Cuba); V, Venezuela; G, Guyana; S, Surinam; FG, French Guyana; C, Colombia. For West Africa, abbreviations are SM, Southern Morocco; M, Mauritania; S, Senegal; GB, Gabon; G, Ghana; and SL, Sierra Leone.

deposition in the Gulf of Mexico rill system. In addition, extensive Jurassic graben systems are documented in northwestern Venezuela [Banok et al., 1981; Maze, 1984]. Floral assemblages [Gonzalez de Juana et al., 1981] and marine fauna [Banok et al., 1985] provide the basis for establishing their age. The main trace of the dominantly Jurassic rifting has a paleo northeast-southwest trend and lies between the central Florida-Yucatan Block and the South American Block (Figure 5).

THE PRECAMBRIAN TO EARLY PALEOZOIC

Northern South America

The presem-day physiography of a Coastal Cordillera and a Tertiary foreland basin overprims the complex pre-Mesozoic geology of the northern margin of South America. The belt is bound to the south by the Guayana Shield and imerrupted in the west by several spurs of the Andean range. This

section focuses on the Precambrian to Paleozoic sequences of the region. The Precambrian Shield is followed northward by an accreted late Precambrian terrane that was subsequently affected by Palaeozoic orogenic activity.

The Precambrian Shield in Venezuela has been subdivided into three provinces (Figure 8) lMartin, 1972; Gonzalez de Juana et al., 1981; Case et al., 1984]. The Pastora province ranges in age from 3000 to 2000 Ma, time equivalem to the Superior province of the Canadian Shield. The Cuchivero province of Venezuela and the Amazonas of Brazil ranges in age from 2000 to 1400 Ma. The Rotalma province, containing thick red sandstones, overlies the older units (Figure 8). Its age is at least Grenvillian. Locally, radiometric age dates from 1600 to 1800 Ma have been reported from diabase sills intruding the red beds lMartin, 1972].

Of interest is the description of the north central Cuban Precambrian complex dated at q- 900 Ma [Renne et al., 1989; Lewis and Draper, 1990]. Some paleo-reconstructions place

Bartok: Prebreakup of Gulf of Mexico-Caribbean and Rifting 443

EIC/I•ALE rHY8 OCEAN

v v EARLY PALAEOZOIC DEFORMED BELT8

Fig. 2. Global reconstruction during the early Paleozoic indicating the location of the Caledonian fold belts (adapted from Scotese [1984] and Scotese and McKerrow [1990].

central Cuba to the northeast of Venezuela (Figure 8) [Anderson and Schmidt, 1983; Ross and Scotese, 1988]. Therefore the Cuban Precambrian should be related to the

similar aged units in the adjacent terranes. Similar aged rocks are present in the Roraima region and are associated with the orogenesis known as the Orinoquean (1300-850 Ma) [Martin, 1972]. The currently used reconstruction suggests a relationship between central Cuba and the Roraima Province of Venezuela.

External to the provinces described above are a series of orogenic belts that range in age from 680 to 500/via. They are commonly grouped as time equivalent to the Pan African orogenies observed in West Africa and the Avalonian orogeny of eastern United States [Hatcher, 1989b]. Several whole rock and mineral specific radiometric ages in central Venezuela yield ages that conform to the late Precambrian event described above [Irving, 1975; F• Codecido et al, 1984] (Figure 8). They represent part of a buried complex orogenic system trending essentially east-west to northeast that appears to have accreted onto the Ouayana Shield. The outcropping Avispa massff was affected by this orogeny (660 Ma, Rb/Sr) as was the Santander massif (680 Ma [Irving, 1975]). Its central core is readily detectable as a regional magnetic high [Cabrera, 1985] (Figure 9). Martin [1978] referred to this orogenic event as the Meridian Phase. Fragments may extend north of the anomaly and include features such as the Tinaco Complex (642 Ma [Martin, 1978] and Sebastopol Complex (425 Ma, whole rock Rb/Sr). The

COAHUILA PLATFORM

SIERRA MADRE

CUCHUMATANES

lUSAI

OUACHITA

YUCATAN (MAYA BLOCK)

MISSISSIPPI

[VENEZUELA I

CORDILLERA

PERIJA••

EL BAUL

L. MARACAIBO

0 20o 400

KM

Fig. 3. Late Palaeozoic fold belt across west central Pangea. Horizontal shading shows the trend of the well-documented Appalachian/Ouachita Central Cordillera trend. The vertical shading represents the expected trace of the late Palaeozoic orogenies along the southern margin of the Gondwana suture.

444 Bartok: Prebreakup of Gulf of Mexico-Caribbean and Rifting

/ /

• +• . / SUWANNEE .•;•-;n .,•,.- EAGLE ',LLS• .,• SABIN UPLIFT/' /DEPRESSION •ET•'.CE • /.'., • ½• •.-.•+.- • .• •

LOS NOel

/:: / " .......... ' I

TI*•O•:•• • -ANG•NA-•ALD'LL I I • I I o 200

KM

Fig. 4. Trend of the Triassic synrift sequences in west central Pangca. Solid line south of the Angelina Caldwell and Wiggins highs corresponds to the Gulf Coast from Texas to Florida.

TRIASSIC RIFT MAY HAVE

BEEN REACTIVATED

YUCATAN

HISPANIC IR

LOCATION ESPINO SIQUISIQUE GRABEN

GIRON O•ITE LA QUINTA •M o 200 400 / '"'" ANTECAL I I I I I GRABEN KM

Fig. 5. Distribution of the major Mid-Jurassic rift trace in west central Pangea. Stippled line within the dark shaded area corresponds to the Gulf Coast from Texas to Florida.

former is comprised of basic lavas and amphibolite facies metamorphics. The latter is a granitic gneiss. Both were incorporated into the Mesozoic Coastal Cordillera of north central Venezuela [Gonzalez de Juana, 1981] (Figure 9). Note that in Cuba there is no known evidence for similar aged orogenic activity IRenne et al., 1989].

Cambrian rifting followed in proximity to the late Precambrian orogenic events affecting northern South America [Martin, 1972]. One example of this event is the rift and post rift sequences that correspond to the Guejar Group of the Colombian Llanos IForero Suarez, 1990]. Another is the Hato Viejo and Carrizal formations of eastern Venezuela IFeo

Bartok: Prebreakup of Gulf of Mexico-Caribbean and Rifting 445

.•0 ø

CANADA M •x

\

j 3• ø

• TRIASSIC RIFTS ALONG THE APPALACHIAN CHAIN

M A f 30 ø

Fig. 6. General distribution of major terranes and tectonic features along eastern United States referred to in the text. BMA is Bnmswick Magnetic Anomaly; ECMA is East Coast Magnetic Anomaly. Major Triassic grabens are indicated [Manspeizer, 1981].

Codecido et al., 1984]. Similar aged rifling is also reported along the Appalachian system of eastern United States. There, the rifting is associated with the opening of the Iapetus Ocean (back-arc spreading) and the opening of the Theic (Paleotethys) Ocean [Hatcher, 1989a] (Figure 2). A back-arc

spreading model may account for the South American counterpart.

In Venezuela, there is evidence that the rift system lies between the late Precambrian orogenic belt and the shield (Figure 7). Two Cambrian rift segments are documemed, the Espino and the Apure-Mantecal grabens (Figure 9). Cross section AA' (Figure 10), based on seismic data, shows the character of the deposits in the Espino graben. The age of the Carrizal Formation (red shales), the oldest dated sediments, has been established by the presence of an association of acrytarchs as Late Cambrian to Ordovician [Feo-Codecido et al., 1984]. The underlying units have yet to be dated. At El Baul (Figure 9), the fossiliferous lower Palaeozoic metasediments of the Caparo Formation correlate to similar units outcropping in the southern Merida Andes [Gonzalez de Juana et al., 1981]. The latter contains Ordovician marine sediments [Hughes, 1980] which are most likely associated with the Mantecal graben. Ulloa et al. [1982] and Hughes [1980] reported similar aged sediments in several wells drilled in the Colombian Llanos and in outcrops on the Macarena Mountains of central Colombia (Figure 8). McCollough [1990] provided a schematic cross section of the Mantecal Graben system, suggesting more intense pre-Cretaceous deformation in the Mantecal area than that observed in the

Espino Graben. The Coastal Cordillera system buries the northern extension of the Espino Graben. A description of the tectonic system active in northern South America during the early Paleozoic is analogous to the pre-Acadian development of the Appalachian trend described by Hatcher [1989a]. It is noteworthy that in the Appalachian trend, Triassic rifting reactivated several of the Cambrian rifts described above [Dewey, 1988].

Early to middle Paleozoic (Caledonian equivalent) orogenic events are reported throughout the northern Andes [Irving, 1975; Gonzalez de Juana et al., 1981; Forero Suarez, 1990]. Burial and overprinting obscure the precise location of the system. Whether they parallel the Precambrian orogenic belt is yet unclear. However, they are present at least from the Santanrer massif of Colombia [Irving, 1975] to the Merida Andes of Venezuela (Gonzalez de Juana et al., 1981] (Figure 8). The event is not considered major and is partly inferred in Venezuela. Prehnite/pumpellyite facies metamorphics

BOREAL

TET HYA N

/ Fig. 7. Early Bajocian Pacific ammonite associations [Westermann, 1980].

446 Bartok: Prebreakup of Gulf of Mexico-Caribbean and Ritting

80 o

10 o_

0o_

\

1400

1250

MERIDA ANDES

60 ø

c. cus•. _..• ISm- SANTA MARTA MASSIF •']- SANTANDER MASSIF

MTS

COLOMBIA

MACARENA

--X 205

VENEZUELA

( ..• [

1690. 2250 4

/

PASTORA

' • BRAZIL

AREA AFFECTED BY CAMBRIAN RIFTING LATE PRECAMBRIAN FOLD BELT RORAIMA 6OO-1400 Ma CUCHIVERO 1400-2000 Ma PASTORA 2000-3000 Ma

1725 t / 1955 1790 ..• X 1770 • X I X2• • 20e4) • \ X

G UAYANA • / GUIAN)

o 200 400 I I I I I

KM

Fig. 8. Northern South America Precambrian to early Palaeozoic outcrop and subcrop distribution.

X IRVING (1975)

o FEO CODECIDO AND OTHERS (1984) /• RENEE AND OTHERS (1989) ß HUGHES (1980) ß ULLOA, PEREZ, AND BALDIS (1982)

GUAJIRA PARAGUANA

!

// 364 ! / ICOTEA FAULT

10• MERIDA / ANDES

/

/ 595

. SANTANDER 1133

I I•)c / AVISPA '/ ß 400 •o • )MASSIF e 660

•. e/ •. 433 - •.-./680 •

APURE MANTECAL GRABEN

73 • 71 ø i I

265

EL AMAPARO

GUARUMEN GRABEN

SEBASTOPOL 425 ESPINO •C•

GRABEN

30,000

ß 270 EL BAUL

(+) 347

ß .

,ooO MAGNETIC BASEMENT BASED ON CABRERA (1985)

RA• AGES

FEO CODECIDO AND OTHERS (1984) 0 50 100 150 I . I

%% GONZALEZ DE JUANA AND OTHERS (1981) KM I •. 69 ø-- -...., 67 ø 65 ø 63 ø 61 ø

I •/ I I I I

Fig. 9. Structural map of depth to basement on aeromagnetic data [Cabrcra, 1985] and age dates from Gonzalez de Juana ct al. [1981] and Fco Codccido ct al. [1984].

associated with the early to middle Paleozoic orogenies have been observed in the Perija Range and Merida Andes [Martin, 1978]. Both the Eastern Cordillera of Colombia and the Merida Andes yield several radiometric age dates ranging from 460 to 390 Ma. Scotese and McKerrow [1990] suggested that this early Paleozoic orogeny focused along the

westernmost portion of Gondwana and was related to active margin deformation.

The basic system of a Proterozoic eraton, a late Precambrian accretion wedge, Cambrian riffing, and subsequent orogenesis, described above, is not ubiquitous over the northern portion of South America. Along its

Bartok: Prebreakup of Gulf of Mexico-Caribbean and Rifting 447

A

CAMPO RUIZ ALTAMIRA HIGH

i I

STA. R I TA - 1X

CHAGUARAMAS

BASAL SS,

ROBLECITO

TIGRE

.•- m m

SEA LEVEL .... • ....

m

ß o ß

GUAYANA SHIELD

CARRIZAL

5000'

M ETAMORP HIC S

' PANAFRICAN AGE'

PHASE + + + •,. G

Fig. 10. Espino Graben, eastern Venezuela (interpretation ofD. Kiser as shown by Fiorillo [1982]).

10,000'

northwestern corner, several elements complicate the tectonic system outlined above. On the one hand, Grenvillian aged units are found on the Santa Marta Block [Tschanz et al., 1974], the Guajim Peninsula and in the Merida Andes (Figure 8 [Case et al., 1990], outboard of the Precambrian orogenic system that rims the Guayana Shield. To the east of Santa Marta, in the Perija Range, Devonian strata of the Rio Cachiri Group [Bowen, 1972] are well documented by their macrofaunal assemblages [Benedetto, 1982; Sanchez and Benedetto, 1983]. Devonian deposits are described in other areas of western Colombia [Burgl, 1963; Forero Suarez, 1990] but are not known to exist in any areas of Venezuela east of the Perija Range [Gonzalez de Juana et al., 1981]. Furthermore, the Devonian faunas of the Perijas have a strong Appalachian affinity and may represent portions of the North America Laurentia Block [Benedetto, 1982]. The Grenvillian ages observed in the central Merida Andes (Avispa massif) are possibly fragments of the Guayana Shield incorporated into the late Precambrian fold belt. Sediments with Laurentia

affinities juxtaposed against a Gondwana suite of sediments and metasediments require the presence of a major suture located somewhat east of the Perija Range and west of the Merida Andes (Figures 8 and 9). The central Lake Maracaibo fault system [Bartok et al., 1981] may represent such a plate boundary (Figure 9).

The Maya Block (Yucatan, Guatemala. Belize, Western Cuba, and Paraguana)

The Maya Block, as described by Anderson and Schmidt [1983], is expanded to include not only the Yucatan

Peninsula, Belize, and the bulk of Guatemala but also western Cuba (Pinar del Rio Province) and the Paraguana Peninsula of Venezuela. The Precambrian Chiapas massff region of southern Mexico is considered to be the westernmost portion of the Maya Block.

The Maya Block is defined by small cratonic centers located in north central Guatemala and Yucatan and the Chiapas massif. The orogenic belts present on the Block include the Maya mountains of Belize, the Cuchumatanes Range to the south, and the Chiapas massif; it may include the highly deformed Chuacus Range. The oldest rocks on the Maya Block are located on the Chiapas Massfl. There, radiometric age dates of 1760 Ma have been reported [Lopez Ramos, 1983]. Zircon ages on several granites of southern Guatemala have reported ages of 1075 and 345 Ma [Donnelly et al., 1990]. The older dates may represent inherited ages with emplacement during the middle Paleozoic [Donnelly et al., 1990]. To the north, the limit is the edge of the Campeche Platform (Figure 11). The northeastern offshore portions of the platform have been drilled by several Deep Sea Drilling Project (DSDP) holes. The radiometric ages of their basement rock mineral assemblages, based on 40At/39At methods, clearly suggest a Pan African aged association, 500 to 547 Ma [Dallmeyer, 1984]. Once again, in the Chiapas region several age dates related to the late Precambrian have been reported [Lopez Ramos, 1983]. On Yucatan proper, evidence to suggest an early Paleozoic orogenic event is scarce. The Yucatan-1 well (Figure 11) penetrated a rhyolite with a whole rock age of 410 Ma [Lopez Ramos, 1983]. In south central Guatemala, the highly contorted metamorphic rocks of the Chuacus Formation are

448 Bartok: Prebrealmp of Gulf of Mexico-Caribbean and Rifting

23øN + + +

•21øN + +

/ YUCATAN • WELL

-19øN +• + [--., ,•,•_['".-_•

.... •.' ,,._ - 17ON , ß

'• PUS ,

-_•

/

63Ma.•/ 538_ 540/' 0 ,,.t'•/

iER--536 cl",•

(1

+

LATE PRECAMBRIAN EARLY PALEOZOIC ACTIVE MARGIN OVERPRINTED BY LATE PALEOZOIC FOLDING

POLOCHIC MOTAGUA F.Z.

-15øN

93øW i

CHUACUS k•• + ß-'•.. LATE PALEOZOIC ,-' ' '*- FOLD BELT

..... • LATE PALEOZOIC / PENETRATIONS

(BISHOP, 1980)

91 øW 89øW 87øW 85øW i I I I

Fig. 11. Major trends on the Yucatan Peninsula.

estimated to be as old as Precambrian or as young as early Paleozoic [Anderson and Schmidt, 1983] and range from greenschist to amphibolite grade lKesler, 1971].

Overlying the Chuacus Formation are a series of Permo- Carboniferous low-grade metamorphics of the less tectonically disturbed Tacfit and Santa Rosa groups (Macal Series) and Mesozoic to Tertiary sediments lKesler et al., 1971; Bishop, 1980]. The Macal Series contains phyllites, conglomerates, limestones, and marbles. In central Guatemala, the Matanzas stock, dated at 275 Ma [Weyl, 1980], penetrates the Chuacus Formation [Anderson and Schmidt, 1983] and thus provides an upper age limit to the unit. Kesler et al. [1971 ] describe the directional traces of fold axes within the Cuchumatanes. The first is essentially east west, and the second is rotated 35 ø to 55 ø, to almost north south. Regardless of their exact age, both formed prior to the deposition of the late Paleozoic Santa Rosa Group. Could they represent two phases of the early Paleozoic folding or are any of them related to the late Precambrian to Cambrian events recorded by the DSDP wells north of the Yucatan Peninsula?

Lewis and Draper [1990] suggested that the sialic basement complex of Pinar del Rio of western Cuba was likely juxtaposed against the present day northeastern Yucatan Block. Its age is not well established.

The Paraguana Peninsula of northern Venezuela (Figure 9) has a very similar rock assemblage to the one described in the Maya Block. High-grade metamorphic rocks, amphibolite schists, and gneisses of the Miralejos Formation [Feo- Codecido et al., 1974] are intruded by the Amparo Granite (265 Ma, U/Pb [Feo-Codecido et al., 1974]). Associated with these rocks are low-grade metamorphic phyllites, red sandstones, and conglomerates. It is suggested here that both rock suites may be closely related to their Yucatan counterparts (Chuacus Formation and Macal Series) and therefore pose the same dilemma regarding the time of metamorphism. Other metamorphic suites in Paraguana, slates and phyllites (Pueblo Nuevo Formation), are also observed and contain Oxfordian to Kimmeridgian ammonites [MacDonald, 1968]. The similarities of the higher-grade metamorphic units found on Paraguana and the Maya region and comparable ages of intrusives suggest that if they were proximal, there would be no significant conflicting geology.

West Africa

Several recent publications [Lecorche et al., 1983; Dallmeyer and Lecorche, 1989; Dallmeyer, 1989, Lecorche et al., 1989] have focused attention on the prerift geology of West Africa. A brief summary is provided in order to

Bartok: Prebreakup of Gulf of Mexico-Caribbean and Rifting 449

complete the tectonic framework of west central Pangea. The geology of this region can be subdivided into two provinces: a complex orogenic belt and a zone unaffected by major orogenies (Figure 12). The undeformed region, comprises the Leo and Reguibat massifs. Along the western portions of each of these eratons, radiometric age determinations yield values > 2000 Ma (Pastora equivalent). The Bullard fit places the the Pastora province in close proximity to the Leo massif. The remainder of the eratons have ages from 2000 to 1500 Ma (Cuchivero and Amazonas equivalent). The sedimentary portions of the region have been subdivided into supergroups [Lecorche et

.al., 1983] (Figure 12). Supergroup 1 series are Precambrian red beds similar to the Roraima Series of Venezuela.

Supergroup 2 is composed of red beds of the Tichilit el Beida and Majera groups consisting of sandstones and some limestones, ranging in age from Cambrian to Ordovician. The descriptions are compatible with the contemporaneous rift deposits in northern Venezuela, and a relationship was first postulated by Benedetto and Puig [1982]. However, the nature of deposition of the African units has as yet not been defined. They extend from the Anti-Atlas, southern Morocco, [Destombes etal., 1985] to Senegal. Supergroup 3 consists of the Dikel Group and corresponds to glacial deposits overlain

by shallow marine series, dated Late Ordovician to Silurian. Supergroup 4, restricted to the Bove Basin and Mauritania, comprises Early Silurian to Devonian sediments.

The orogenic belt has a definite Pan African root [Dallmeyer and Lecorche, 1989]. Because many components of supergroups 1, 2, 3, and 4 are found incorporated in the fold belts, there has been extensive remobilization in the region as late as the late Paleozoic. If early Paleozoic orogenies are present in the region, their impact appears to have been negligible. Early Paleozoic deformation is suggested by Lecorche etal., [1983] and is reputed to extend north-south from the High Atlas Mountains (Morocco) to the Mauritanide-Rockelides (Senegal; Figure 12). Dallmeyer and Lecorche [1989] suggested that the Pan African component of the fold belt is clearly retained as the dominant orogenic phase in the Rockelides. This is evidenced by the Coyah granite, dated by Dallmeyer [1987] at 586 Ma (Pan African; Figure 12). The Mauritanide fold belt, although it has a Pan African root, is strongly affected by the late Paleozoic orogeny.

Florida

Florida can readily be divided into two distinct geologic provinces [Mueller and Porch, 1983, p. 172] "The age of the

SHIELD FOLD BELT

SUPERGROUP

PRECAMBRIAN RED BEDS

CAMBRO-ORDOVICIAN

RED SANDSTONES/ SHALES

BOVE BASIN

COYAH GRANITE

+

+ + +

+ + + + + + + + + + +

+

+ + + +

+ + ..+ +

+ + +\+

* TRI•ELIDES ,,. +

LATE ORDOVICIAN SILURIAN

SILURIAN/DEVONIAN

.j'

LEO UPLIFT

)

'3

L. /

:

i 0 i 1•00 2•00 300ML ,

o •o =oo ,oo ,oo •K,. 15 ø 10 ø I I

5 ø 0 o I i

Fig. 12. West Africa Precambrian and early Palaeozoic outcrop and subcrop distribution [Lecorche et al., 1989].

450 Bartok: Prebrealmp of Gulf of Mexico-Caribbean and Rifting

northern province is minimally early Palaeozoic while the southern province developed during the early Mesozoic. The provinces probably were the result of different tectonic conditions that involved a convergent ocean plate boundary in the north and a hot-spot influence episode of intra-continental rifting in the south" (Figure 13). The same authors carded out radiometric age determinations (40Ar/39Ar) in

PENSACOLA HIGH

[] LATE PRECAMBRIAN "' !x.•xyf,•:.•:.pl•.il :•.GRANITE -

SRI)OVICIAN IO LURA- IAN (OR OLDER)/......x

I•) • EQUIV. PROVINCE ' "•",• I •. •:•)•1•1-•'•=' I PAN AFRICAN

KM

0 80 1 •0 240 ß

i i i i ,,

Fig. 13. Florida Precambrian and carly Paleozoic subcrop distribution. References for age dates are Opplin [1951] and

both regions. The ages in the northern province ranged from 530 Ma in St. Lucie County to as young as 348 Ma in Flagler County (Figure 13). These ages represent minimum cooling ages. The two zones flank the Osceola granite dated at 528 Ma [Dallmeyer, 1987]. It is noteworthy that detrital samples, obtained from the basal units of the Sohio GNV 707-1 well

(Figure 4), yielded an age date of 576 Ma (BP internal report, 1985). The composition of the northern rock suites is calc- alkaline andesitic. The felsic rhyolites extend west to the Pensacola High [Arden, 1974]. Its possible continuation along the northern collision front (Ouachita Trend) was discussed by Burgess [1976]. Dallmeyer et al. [19871>] have studied the Osceola granite of Florida and the Coyah granite of the Rockelides and concluded that they are closely related. The southern, St. Lucie rock suites, are amphibolite schists and gneisses. Wells drilled on the Tampa Arch penetrated granites and granodiorite [Pindell, 1985] that appear to be pre-Ordovician in age [D. Martin, BP internal reports, 1985].

A third microplate, associated with the Florida region, has been described in the literature and named the Florida Straits

Block [Pindell, 1985]. The block underlies the present-day Bahamas. Its basement structure and geologic development are not well documented but may be similar to the South Florida Block.

Armed with the description of the terranes that make up the Florida region, and reviewing the gravity and mgnetic signatures in the northeast Gulf of Mexico (Figure 14 and 15; compiled from multiple contractor surveys) as well as the extensive onshore drilling, the suggestion is made that the prominent northeast-southwest trending grain on the gravity

88 87• 86 ø 84 ø PENSACOLA

30 ø

29

• AREA OF FIG. 17 AND GNV-707-1 WELL

0 MILES 70

' C.I.- 12mg • ' 850 840 83 ø 82 ø 81 ø

Fig. 14. Isostatically corrected Bougucr gravity anmnaly map of the northeast Gulf of Mexico, highs (H) and lows (L).

Bartok: Prebrealmp of Gulf of Mexico-Caribbean and Rifting 451

84 ø

PENSACOLA

83 ø 82' 81 ø

30 ø

$.FLORIDA

O AREA OF FIG. 17 AND GNV-707-1 WELL

0 MILES 70 * C.1.=120 gamma• t •

85 ø 84 ø 8,3 ø i

Fig. 15. Reduced to pole total field magnetic intensity map of the northeast Gulf of Mexico, highs (H) [Gough, 1967; Klitgord, 1984; King, 1959].

and magnetic maps, the Tampa Arch, is the result of the pre- Ordovician or Pan African aged basement. It is likely that the strong magnetic anomalies observed along the northern flank of the arch (Figure 15) correspond to the Ordovician felsic units. They may be related to the rhyolites observed in the Yucatan-1 well. However, the current state of knowledge does not permit unequivocal linkage of the two blocks by means of gravity and magnetic lineaments. The effects of Mesozoic rifting on the potential fields could yield similar results.

The area to the north of the Ordovician rhyolites, designated zone 2 and 3 on Figure 13, comprises sandstones and shales that range in age from Cambrian to Devonian. They are comparable to the West Africa's supergroups 2 and 3 and apparently have not been severely deformed by either the early or late Paleozoic orogenies. In the offshore Blake Plateau, the U.S. Geological Survey Cost well G-1 penetrated presumably Devonian metasedimentary sequences dated at 346-374 Ma [Dallmeyer, 1989]. Their relationship to the other metamorphic sequences described above is unclear. The possibility exists that sequences observed in north Florida and West Africa correspond to Cambrian rift and post rift sequences. Their paleotrends do not confiiet with the restored position of the Espino Graben system of Venezuela.

Northwest Florida and Alabama contain several interesting elements that have been under study by W. Thomas and R. D. Dallmeyer (personal communication, 1989). Both authors suggested that there is an abrupt termination of the Appalachian mid-Paleozoic orogenic belt, which nearly conforms to its present terminus. The southern limit of the Appalachian fold belt is closely associated with the

Brunswick Magnetic Anomaly (BMA; Figure 15). Of the main features observed south of the BMA and not previously described two are noted in this discussion: the Wiggins uplift and Pensacola ridge (Figure 15). Preliminary results of W. Thomas and R. B. Dallmeyer suggested that these units may represent Pan African orogenic belts that had undergone some late Paleozoic orogenic overprinting (Figure 15). The nature of the Pensacola rocks appears to be similar to those of central Florida. Felsic low-grade metaigneous suites are observed [Dallmeyer, 1989].

DISCUSSION OF TIlE PRECAMBRIAN TO EARLY PALEOZOIC IN THE AREA OF STUDY

The purpose of reviewing the geologic framework of the Precambrian to early Paleozoic of the region is to evaluate its effect on the subsequent deformation of what would eventually become "west central" Pangea. For this reason the discussion of the trends is noted on a reconstruction of the

late Paleozoic. Only the late Precambrian and early Paleozoic systems discussed in the text are indicated (Figure 16). The reconstruction follows the model Mopted in Figure 1. Several key observations can be mme. First, the West African Pan African fold belt has a distinct north-south strike extending from the early Mauritanides to the Rockelides. In a paleo south direction to the Rockelides lie a series of Early Cambrian fold belts, the Estrondo Hills [Schobbenhaus et al., 1984], and the northern extension of the late Precambrian Paraguai-Araguaia fold belt. They separate the Amazonas Province of Brazil from the Ceara Platform basement

complex that underlies the Maranon Basin of northeastern

452 Bartok: Prebreakup of Gulf of Mexico-Caribbean and Rifting

ORDOVICIAN RHYOLITE

YUCATAN- 1

./ /

' G , V ,,, --?,. , ', FG /

"-..'" i ,,/ • [ • /

I c•' -- ..'-' t \ -" x t •, \ /I

• ' "ß '/ AMAZONAS • // PROVINCE

s

MARANON BASIN

I • I 0 200

' ! ' I ' I 400 6OO 8OO

Fig. 16. Distribution of the Pan African aged systems reviewed in the text. See Figure 1 for abbreviations.

Brazil (Figure 16). The core of the fold belt comprises Protemzoic low-grade metamorphic rock suites overlain by coarse to fine grained sediments. Their age has been assigned to the Cambrian [Schobbenhaus et al., 1984]. Therefore it is suggested that the Pan African fold belt of West Africa extends through Senegal and Sierra Leone and continues into northeastern Brazil. A second observation

arises from the discussions of l he previous sections. Where do the Yucatan, Florida, and northern South America's Precambrian trends fit into the most accepted model for the reconstruction of Gondwana?

The northern South America late Precambrian/lowermost

Paleozoic fold belt has a distinct paleo east-northeast direction that does not conflict with that of the Tampa Arch trend of Florida. The similarity in age of deformation of the Tampa Arch (late Precambrian and early Paleozoic) and of the northern Maya Block suggests a relationship. The implication is that the east-west system represents a separate Precambrian event or phase to that observed in West Africa. One possible explanation is that it represents accretion along the northwest margin of Gondwana because the Rockelide trend is likely to have originated from continem-continem collision (C. Scotese, personal communication, 1990).

The Cambro-Ordovician sedimems of West Africa are

observed to lie between the Pan African fold belts and the

cratons. This concept also applies to northern South America, but in Florida and Yucatan the fragmentation appears to be complex and not fully resolved. Cambm- Ordovician sediments [Dallmeyer, 1989] are observed both inboard and outboard of the Florida "Pan African" system, i.e. between Saint Lucie and the Wiggins/Pensacola highs. In fact, they may simply lie on a collapsed portion of the Pan African aged fold belt. The models applied to the Cambrian rifts, located near the Brevard zone of the Appalachians [Hatcher, 1989a] (Figure 6) may be adapted to rift systems of Florida, West Africa, and northern South America. The dominant grain of the late Precambrian to early Paleozoic tectonism of west central Pangea is east-northeast.

THE LATE PALEOZOIC FOLD BELT:

WEST CENTRAL PANGEA

Contrary to the segmentation into subregions used for the Precambrian to early Paleozoic, the discussion of the late Paleozoic is described in the context of the reconstructed

Pangea. There is strong evidence for Alleghanian aged

Bartok: Prebreakup of Gulf of Mexico-Caribbean and Rifting 453

orogenies not only along the Appalachians/Ouachita/Marathons [Pindell, 1985] but also along the Coahuila Platform, Sierra Madre Oriental of Mexico [Csema, 1960; Lopez Ramos; 1983, Handschy et al., 1988]. They extend south to the Chuacus Ranges, Maya

Mountains, Central Cordillera of Colombia, and western Venezuela. Their relationships are the focus of this section.

The literature on the Alleghanian (Hercynian aged) orogeny in both the Appalachian and Ouachita trends is exhaustive and does not require repeating [Williams and Hatcher, 1983; Fallin, 1985; Hatcher et al., 1989]. The connection between the Appalachian range and the Ouachitas, across the Mississippi Embayment, has been a subject of some debate. Several lines of evidence point to the conclusion of some continuity: (1) the regional gravity map (Plate 1 from Hinze and Hood [1988]) clearly showed a change in direction to west northwest of the underlying basement complex at the southern extremity of the Appalachians and (2) Thomas ß [1989a] considered the transition between the two to have a strike-slip component, and hence in the past the systems were directly joined and more rectilinear. The same condition applies to several other sectors of the belt. In northern Mexico, the Ouachita/Marathon trend has been extended south into the Coahuila Block [Lopez Ramos, 1983]. The southern continuation appears interrupted by the Sonora/Monterrey megashears and may be displaced significantly east [Pindell and Barrett, 1990]. Permo- Carboniferous disturbed belts have been observed

underpinning the Laramide orogeny of the presem Sierra Madre Oriental [Lopez Ramos, 1983]. Intrusives in the Maya Mountains and the Cuchumatanes/Chuacus Ranges (210-340 Ma [Weyl, 1980]) are consistent with the late Paleozoic deformation (Figure 11).

The South American component of the late Paleozoic fold belt is very well documented in the Colombian Cemral Cordillera and in the presently exposed Santander massif of the Eastern Cordillera [Irving, 1975]. It extends south through Ecuador and coastal Peru [Ziell, 1979]. By combining the previous discussion of the central Colombian Devonian with the information on Colombia's late Paleozoic

deformation there is a strong suggestion for coincidence with the Alleghanian orogenic system. The Chuacus range, Guatemala, may represent the continuity of the system in Central America.

In northern Venezuela, the metamorphism of the Carboniferous system observed in the Andes [Gonzalez de Juana et al., 1981; Case et al., 1990], the intrusives on Paraguana (El Amparo granite [Feo Codecido et al., 1974], and at the El Baul complex [Kiser and Bass, 1985] (Figure 9) support the presence of the late Paleozoic orogenic event affecting Venezuela [Martin Bellizzia, 1961]. The Sabaneta and Palmarito formations, outcropping along the Merida Andes are the shelf equivalents of the deepwater pellitic Mucuchachi Formation (V. Pumpin, personal communication, 1979) [Gonzalez de Juana et al., 1981]. The Mucuchachi Formation was metamorphosed during the late Paleozoic orogeny. At E1 Baul, the.late Paleozoic metasediments of the Barbasco Group and associated granitic plutons (270 i 10 Ma, K/At [Gonzalez de Juana et al., 1981] appear to conform to the metamorphism of the Mucuchachi Formation observed along the eastern Maracaibo Basin. There is no evidence to carry the orogeny farther east beyond the El Baul complex. The combination of trends from

western Venezuela, Chuacus, and Maya Mountains represents the continuation of the late Paleozoic orogenic trend.

In western Africa, the late Paleozoic fold belts are very well documented in Morocco and Algeria where the Anti-Arias Mountains continue into the Mauritanides. Both belts include

deformed Devonian sediments [Destorobes et al., 1985]. Dallmeyer and Lecorche [1989] analyzed the late Paleozoic system along the southern Mauritanides. They described the fold belt as directed north-south to the Bove Basin (Figure 12), where it bends sharply to the west.

In summary, it can be stated that the late Paleozoic orogenic belts are well documented along the western margin of the Laurentia/Gondwana suture. They are the Appalachians, Ouachitas, Serrania Oriental (Mexico), and the Central and Eastern Cordillera of Colombia. The late Paleozoic

deformation along the southeastern margin of the suture is more poorly constrained. In northwest Africa the late Paleozoic orogeny is documented from the Anti-Atlas to the Mauritanides. Neugebauer [1989] suggested that the system extends along central Florida and is projected westward. There is no evidence in the geology of central Florida or in the Pinar del Rio area of western Cuba to support this argument. However, the weakly metamorphosed Permo- Carboniferous of the Maya Mountain of Belize may be the continuation of this system. The Maya Quintana Roo arch discussed by Buffier [1989] is coincident with a significant magnetic anomaly and may form part of this deformation. The relationship between the arch and magnetic anomaly is as yet unclear but is thought to be either the effect of overprinting Mesozoic rifting or related to the original Paleozoic orogenic activity. In Venezuela, the late Paleozoic orogeny is documented only in western Venezuela and Paraguana and follows the present Andean trend. It is proposed that the two systems, Appalachian/Ouachita and northern South America, complement each other and bound the Pangea Suture (Gondwana/Laurentia).

THE PANGEA SUTURE: A DISCUSSION

Among the most significant recent advances in the understanding of this topic are the series of papers by Nelson et al. [1985] and McBride and Nelson [1988] dealing with the Consortium for Continental Reflection Profiling (COCORP) lines shot across northern Florida. However, a detailed review of the recent literature on the geology of the southern Appalachian province provides imeresting insights on the tectonics active during the late Palaeozoic. The discussion follows the work of Williams and Hatcher [1983], Tauvers and Muehlberger [1988], Fawet and Williams [1988], and Dallmeyer and Lecorche [ 1989] and open questions on the studies by the group led by McBride and Nelson[1988].

Immediately prior to the Devonian Acadian orogeny, the Avalonia metamorphic terrane was in close proximity to North America [Woodcock et al., 1988]. Avalonia contains several Appalachian provinces that show affinity to Laurentia assemblages [Buffier, 1989]. East of this trend, the terrane includes the Charleston and Brunswick belts [Higgins and Zietz, 1983] and an extra-Avalon terrane (Figure 6). All three are dominantly of a Gondwana association. Zircon ages in the sandstones of the Brunswick belt yield ages of 1800 Ma [Opdyke et al., 1987] and therefore are significantly older than the Grenvillian basement associated with the

Appalachian foreland [Williams and Hatcher, 1983]. This

454 Bartok: Prebrealmp of Gulf of Mexico-Caribbean and Rifting

extra-Avalon terrane (Figure 6) consists of Eocambrian unmetamorphosed felsic plutonic and volcanic rocks. It is overlain by unreformed early Paleozoic platform sediments comprising greywackes and shales and dated as Cambro- Ordovician [Tauvers and Muehlberger, 1988; Higgins et al., 1989]. Because all of these suspect terranes have African affinities, have undergone similar orogenic histories, postdate the Avalonia-Piedmont suture [Favret and Williams, 1988; Hatcher, 1989b], and have a similar gravity and magnetic signature [I-Iinze and Braile, 1988], they have been grouped as the extra-Avalon terrane. Estimated age for juxtaposition is Alleghanian, Hercynian [Favret and Williams, 1988; Dallmeyer and Lecorche, 1989]. The western limits of this region are marked by a series of provinces defined by their magnetic signature [Rankin et al., 1989]. The eastern limit extends at least to the East Coast Magnetic Anomaly (ECMA; Figure 6).

McBride and Nelson [1988] have indicated that the onshore Brunswick Magnetic Anomaly (BMA) and its offshore equivalent, the East Coast Magnetic Anomaly (ECMA), represents the eastern and southern limits of Laurenfla. However, based on the above discussion, there is a strong suggestion that the Avalon-extra-Avalon suture, located near the fall line of the Appalachian foothills, is more representative of the Laurenfia-Gondwana suture (Figure 6).

As discussed earlier, W. Thomas and R. D. Dallmeyer (personal communication, 1989) suggested that the Wiggins and Pensacola highs (Figs. 4 and 6) corresponded to Gondwana and not Laurentia. Therefore the Gondwana

suture is likely to be located north of the Wiggins and Pensacola arches and in close proximity to the Ouachita trend (Figure 3). Thomas [1989b] had labelled the eastern portion of the suture as Suwannee-Wiggins. The stunmary paper by Burgess [1976] suggested that the Ouachitas resulted from the possible collision of Gondwana and Laurenfla. The continuation of the Ouachita Marathon chain south imo the

Sierra Madre Oriental of'Mexico and the Chuacus Range results in the necessity for proposing a Gondwana-Laurentia suture lying northwest of the restored position of Yucatan. Because the Santa Marta-Perija region appears to have a closer affinity to both the Appalachians and the Central Cordillera fold belt of Colombia, it is proposed that the suture lies east of this trend. The descriptions of Yucatan and Florida are incompatible with the latter two provinces but conform more closely to the geologic description given for the northern margin of Gondwana. Following the earlier discussion of northern South America, the suture is therefore likely to pass through Lake Maracaibo, Venezuela (Figure 3). The eastern flank of the fault system is dominated by a light to moderately metamorphosed possibly Carboniferous pellitic schist of the Mucuchachi Formation [Gonzalez de Juana et al., 1981]. To the west lie a series of horsts and grabens (related to Mesozoic rifting) that contain unmetamorphosed sediments of the Carboniferous Carlo del Nomeste, Carlo Indio and Rio Palmar formations [Gonzalez de Juana et al., 1981]. The horsts tend to be granific and aged at circa 364 Ma [Feo-Codecido et al., 1984]. Burgl [1973] suggested the close affinity between the Floresta massif of the Eastern Cordillera of Colombia and the Perija Range.

At the very least it can be said that if the southeastern segment of the Maya Block had been attached to South America that neither the age dates of the Chiapas massif nor the deformation recorded in the Chuacus Formation seriously

conflicts with the tectonic development described for northern South America.

THE MESOZOIC RIFT SYSTEM

The primary objective of this study is to demonstrate the relationship between the Mesozoic rift systems active in west central Pangea and the preexisting tectonic trends. Thus far the report has dealt with the prebreakup geology of the region. The presem section will focus attention on the Mesozoic rift systems. It is interesting to note there are two fundamentally different rifting events within the study area. The Triassic event has a trace that follows from the western

North Atlantic, extends along the rim of the Gulf of Mexico, and continues along the northwestern side of South America in Colombia, Ecuador, and Peru [Jaillard et al., 1990]. In West Africa, the Triassic grabens are also documented in Morocco and Western Sahara [Manspeizer, 1981]. The Jurassic trend principally affects a segment of the North Atlantic that in general lies seaward of the Triassic rffi trend of the East Coast of the United States and northwest Africa.

As a result, the continuation of the trend into west central Pangea follows a trace that continues along south Florida, the present-day eastern margin of Yucatan, and northern Venezuela. There was only minor reactivation of the Gulf of Mexico rift system during the Jurassic. The Triassic Eagle Mills is unconformably overlain by Callovian sediments. The early Paleozoic grabens that developed along northern South America undenvem reactivation in the Jurassic. Sym'ift red beds (Figure 9) filled the Espino and Apure/Mantecal grabens. In western Venezuela the Jurassic Rift essentially overlaps the Triassic system. There has been some discussion in the literature as to the possibility of a continuous rifting evem extending from the Triassic through to the Late Jurassic [Ross and Scotese, 1988]. However, the present study suggests an episodic rift system. This is demonstrated by the unconformable relationship between the Triassic and Jurassic sequences of the Gulf of Mexico as well as differences in the areal distribution of the two rift systems.

THE TRIASSIC RIFT SYSTEM

The literature on the Triassic rift system in the Mississippi Salt Basin and East Texas Basin is voluminous [Scott et al., 1961; Vernon, 1970; Walper, 1980]. Within the Suwannee basin of northern Florida (Figure 4), Triassic sequences have been penetrated by several wells. The southwestern extension of the graben trend has been postulated by several authors [e.g., Buffier and Sawyer, 1985] but not confirmed. Where the U.S. East Coast and Gulf Coast Triassic rift systems are well documented, their relationships to previous zones of weakness seem clear. Triassic rifling along eastern North America follows along or is in close proximity to the Brevard Zone (Precambrian suture) and along the Avalon/extra- Avalon late Paleozoic suture [Manspeizer et al., 1989]. The South Georgia rift basin lies in close proximity to the Brunswick Magnetic Anomaly (the Suwannee-Wiggins Suture) and extends west and into the Mississippi Salt basin. A branch of the South Georgia Graben extends south along the Suwannee depression of central Florida. It continues into the northeastern sector of the Gulf of Mexico. In general, the trend conforms to the proposed trace of the Gondwana- Laurenfia suture.

Bartok: Prebreakup of Gulf of Mexico-Caribbean and Rifting 455

To better understand the distribution of • systems, the study focuses on the Suwannee ri•. Of significance is the Sohio Gainsville 707-1 well (GNV-707-1), drilled in 1985 (Figure 4). More than 300 m of Triassic red beds were penetrated in the well and dated by pollen as Ladinian to Carnian. Underlying the sediments are a series of volcanics and volcanoclastics that grade upward to red bed sequences. Their age is at least Mid-Triassic (224 Ma; BP internal report, 1985) and would therefore conform to the ages of the Triassic volcanic complexes along the Newark graben of the U.S. East Coast. The gravity (Figure 13) and the magnetic anomaly maps, reduced to pole (Figure 14) of the Florida area (synthesized by G. Flanagan, BP internal report, 1989), provide interesting information not only on the prerift sequences but also on the • system itself.

The northeast-southwest grain described previously for the central Florida basement complex also applies to western Florida both onshore and offshore. A seismic line that was

recently shot, over the GNV 707-1 well provides a glimpse of the distribution and seismic character of the Triassic graben system (Figure 17). The extent of the graben system conforms to the pattern defined by Bufflet [1989]. Note the coincidence between the strong gravity low and Suwannee graben.

There is irrefutable evidence for the presence of massive Triassic Eagle Mills red beds along the southern margin of the Ouachita fold belt [Scott et al., 1961; Vernon, 1970; Walper, 1980]. For the most part, the units are underlain by the Atokan (Late Carboniferous) strata and overlain by Louann salt that is at least Oxfordian but more likely Callovian in age. Pollen age determinations support a late Middle Triassic age for the Eagle Mills [May and Traverse, 19861.

SW

In a general sense, both the East Texas/Mississippi and the Suwannee and northwest Mexico ri• trends [Salvador, 1987] conform to the model of rifting in close proximity to an older orogenic belt. The two are essentially parallel features and conform to the outline of the northern Gondwana early Paleozoic and late Precambrian trends as well as the Ouachita

late Paleozoic orogeny. The area lying between the two rift trends (Figure 4) may correspond to the early Paleozoic orogenic system proposed by Burgess [1976].

Southward, the Eagle Mills is the time equivalent of the La Boca red beds formation, lower member of the Huizachal Group of Mexico, and is well defined in outcrops at Los Novillos Canyon near Ciudad Victoria, Mexico (Figure 4). Elsewhere, the unit has been confused with the overlying Late Jurassic La Joya red beds (upper Huizachal Group). Therefore the precise distribution of the Triassic system in Mexico is difficult to establish. The general trend of the Triassic rifting is suggested by Walper [1980] and conforms to Figure 4. The distribution of the La Boca grabens parallel the Alleghanian aged orogeny of eastern Mexico.

On the Maya Block, Yucatan region, the red beds observed are limited to the La Joya equivalent. The units are known as the Todos Santos Formation and may be as young as Neocomian [Richards, 1963; Lopez Ramos, 1983]. Similar units are also reported in the Chortis Block (Honduras). The Todos Santos is overlain by salt and anhydrite that are at least Early Cretaceous [Bishop, 1980]. Progressing southward, in a paleogeographic sense (Figure 4), the next system of red beds is observed in Colombia and Venezuela. The dominant

red bed sequences in these countries are the Giron and its time equivalent, the La Quinta formations [Schubert, 1986] (Figure 5). Both range in age from Jurassic to lowermost Cretaceous on the basis of their floral associations [Gonzalez

NE

SOHIO

GVE 707-1 ..........

Fig. 17. NE-SW seismic line crossing the well location for the Sohio GNV 707-1 well.

456 Bartok: Prebreakup of Gulf of Mexico-Caribbean and Rifting

de Juana et al., 1981]. The interesting aspect of the La Quinta is that it unconformably overlies the La Ge Group. Once again, this relationship suggests the possibility of a significant hiatus between the two. The older unit also contains significant red beds and has a strong association with volcanic sequences. The age of the Tinacoa Formation (La Ge Group) may range down to the Triassic. Near the contact with the overlying La Quinta, the Tinacoa has been dated on the basis of its floral assemblage of Ptiloph¾11um sp., Otozamites sp., and Cyzicus (Euesteria) sp. [Benedetto and Odreman, 1977] as lowermost Jurassic. In central Colombia, east of the late Paleozoic fold belt of the Central Cordillera, Burgl [1963] described the Triassic Payantic Formation as a system of red beds with occasional marine incursions, up to 600 m thick, overlying dacites and rhyolites [Cediel et al., 1981]. The Payantic limestones had been dated as Carnian based on crinoids (Pentacrinus sp.) and the pelecypod M¾ophoria jaworskii [Burgl, 1963]. The upper Payantic contains ammonites, such as Nevadites and Anolcites, as well as the pelecypod Pseudomontis ochofica, all of which are guide fossils for the Norian. The Payantic Formation is overlain by the Rhaetic to Liassic Giron Formation in Colombia. The South American Triassic rift system is, once again, closely related to the proposed trace of the Laurentia- Gondwana suture.

MID-JURaSSIC HISPANIC CORRIDOR

The great biotic exchange between the Tethys and Pacific oceans is believed to have taken place during the Bajocian/Bathonian [Westermann, 1980; Smith, 1983]. Liassic ammonites maintained a distinct provinciality of eastern, western, and boreal Pacific assemblages (Figure 7). Mixing of east Pacific and Tethyan associations had been observed in Peru in both sponges and ammonite assemblages [Westermann, 1980] and in western Canada in ammonites [Smith, 1983]. Of particular significance were the anunonite specimens observed in the allochthonous Siquisique region of northwestern Venezuela, where they have been dated as Bajocian/Bathonian [Bartok et al., 1985]. The faunal assemblage is found in close association with pillow basalts which represent the early phase of oceanic crust development in the region. The age determination for Siquisique was based on the presence of Emileia multiformis and Stephanoceras quiroceras. However, of greater significance is the presence of Parkinsonia sp. Though the specimen is poorly preserved and additional sampling is suggested, several investigators concurred with the classification [Banok et al., 1985]. The assemblage present at Siquisique indicated mixture of Tethyan and Pacific faunas and therefore traced the "Hispanic Corridor" (Smith, 1983) through the region lying between the Yucatan Peninsula and the South American continent (Figure 5).

The K-At radiometric ages and alkalic composition analyses of South Florida Block samples (at Hardee County, 192 Ma; Highland County, 183 Ma; Collier County, 189 Ma) support a mid-Jurassic volcanic event related to a continental rifting [Mueller and Porch, 1983]. The northern Florida early Paleozoic volcanics are calc-alkalinic whereas the southern

(Jurassic) are transitional between alkalic and tholeiitic types [Mueller and Porch, 1983]. The regional trends in this area are compatible with the rifting affecting northern South America.

Unfortunately, the literature on the Middle Jurassic of Cuba, Venezuela, and Colombia is not extensive. In western Cuba, the San Cayetano Formation is unequivocally Oxfordian in its upper members [Wierzbowski, 1976], but its lower members may be as old as Bajocian [Ryabukhin et al., 1983]. An additional aspect of the lower clastic member is the dominance of south to north directional features

suggesting a southern provenance [Meyerhoff and Hatten, 1974; Ryabukhin et al., 1983] that possibly could be the Guayana Shield. Pindell [1985] and Lewis and Draper [1990] suggested that the Yucatan Block may have been the provenance for the sediments of the San Cayetano clastics. The opposing views do not by themselves deter a palcoreconstruction placing Pinar del Rio in close proximity to northern South America and northern Yucatan.

Pelecypods found in the lower San Cayetano appear to confirm a Middle Jurassic age [Anderson and Schmidt, 1983] and the presence of marine conditions. When the San Cayetano data are combined with the Siquisique ammonite assemblage and with those located in the Morrocoyal outcrop at the northern extremity of the Central Cordillera of Colombia [Geyer, 1976], an image begins to unfold as to the trace of the Jurassic separation between Yucatan and South America. The tectonic setting that gave rise to the sedimentation at Pinar del Rio has not been documented. Nor

has the underlying basement been described in detail. Given the previous discussions it is suspected that the structural setting for the Pinar del Rio sequences will either conform to the late Paleozoic orogenic event or be associated with the late Precambrian system.

South of the Coastal Range of northern Venezuela lies the Guammen Graben (Figure 9). The age of the oldest sediments in the graben has not been established. However, its position and trend [Kiser and Bass, 1985] would be coincident with that suggested for the Jurassic rift event of northern South America and previously labelled as the Hispanic Corridor.

The precise position of the South Florida Block and its relationship to the Jurassic rift system is not clearly defined in the literature. However, the magnetic map (Figure 15) for the Florida region suggests that if strike-slip faults are present on the Florida Platform the relationships proposed by Pindell [1985] and summarized in Figure 1 are not unreasonable.

Potential Jurassic rffi sequences are observed along the northern edge of the Coastal Range of Venezuela and the Guammen Graben (Figure 9) IKiser and Bass, 1985], and mid-Jurassic marine faunas are observed in allochthonous

blocks at Siquisique and along the northern portion of the Central Cordillera of Colombia [Geyer, 1976]. It is proposed that this rift trace follows the trend of the late Paleozoic

orogeny and the late Precambrian orogenic belt affecting northern South America. Some reactivation of the Cambrian

grabens located south of the Jurassic Guammen rift mentioned above is also documented. These include the

Espino Graben (Figure 10) and Mantecal Graben [McCullough, 1990]. In western Venezuela and eastern Colombia, the Jurassic grabens, containing the Giron and La Quinta red beds and Late Jurassic/Early Cretaceous salt deposits near Bogota, closely follow the proposed zone of the Pangea suture resulting in a bend from an east-west trend to a northeast-southwest trend. Several northeast trending grabens are reported within the Maracaibo Basin [Bartok et al., 1981; Maze, 1984]. They include the Machiques, Central

Bartok: Prebreakup of Gulf of Mexico-Caribbean and Rifting 457

Lake, Uribante, and San Lazaro grabens. In all cases they comprise continental red beds that are at least Late Jurassic to Early Cretaceous in age [Gonzalez de Juana et al., 1981]. The Guajira Peninsula, located north of the Maracaibo Basin, poses interesting problems. On the one hand, Middle Jurassic marine conditions are well documented [Renz, 1960]; on the other hand, the lack of knowledge on its Jurassic location prevents its faunal assemblage from providing valuable information on the Jurassic rift trend.

CONCLUSIONS

An extensive synthesis has been made of the prebreakup geology of west central Pangea. A comparison of the trace of the Mesozoic rift system and the prebreakup orogenic belts serves to corroborate the hypothesis for a potential direct relationship between a preexisting fold belt and subsequent riring. Although the basic tenets of this relationship are established in the literature the significance to this study lies in its application to the area of "west central Pangea." Because the prebreakup geology is poorly understood and the rift systems have not been fully integrated, two objectives have been achieved by the present study. First, a synthesis of the prebreakup deformation of "west central Pangea," namely, northern South America, Yucatan, proto Gulf of Mexico, Florida, and West Africa, has been demonstrated to provide the template for the Mesozoic rift trends. Second, by reviewing the geology of the known rift systems, additional information can be discerned on the fundamental trends of

prebreakup orogenies. The late Precambrian and early Paleozoic orogenies as well

as the Pangea suture are the dominant controlling elements

affecting early Paleozoic, Triassic, and Jurassic rift systems. Triassic rifting is observed both seaward and paralleling the trends of the Alleghanian/Ouachita orogenies of eastern and southern North America and parallel to the early Paleozoic trends of Florida and northern Yucatan. The rift system continues south along the Sierra Madre Oriental of Mexico and the area east of the Central Cordillera of Colombia. The

trace corresponds to the proposed Gondwana/Laurentia suture. The Triassic rifts range in age from Ladinian to Caman.

Jurassic rifting in west central Pangea tends to parallel the late Precambrian orogenic belt of northwestern Gondwana, between the Maya Block and northern South America. Along its western continuation the rift system changes direction and parallels the late Paleozoic orogenic belt. Its age is at least Bajocian/Bathonian. The Jurassic rift provided communication between the Tethyan and Pacific realms.

An understanding of the basement framework in west central Pangea has assisted in proposing a model for the development of the rift systems in west central Pangea. If an inherent zone of weakness exists in a zone undergoing thermal expansion, rifting will either follow or closely parallel the trace of the zone.

Acknowledgments. A synthesis of this nature is not possible without the constructive dialogue with many colleagues. Their assistance is appreciated. I wish particularly to thank James Case, Dick Bufflet, Norm Rosen, Chris Scotese, and Dave Roberts for their review of the material. The support and permission to publish granted by BP International is also appreciated.

REFERENCES

Anderson, T. H., and V. • Schmidt, The evolution of Middle America and the Gulf of

Mexico - Caribbean Sea region during Mesozoic time: Geol. S0c. Am., Bull., 94, p. 941-966, 1983.

Arden, D. D., Jr., Geology of the Suwannee Basin Interpreted from Geophysical Profiles, Trans., Gulf Coast Assoc. Geol. Soc., 24, 223-230, 1974.

Barnett, R. S., Basement structure of Florida and its tectonic implications, Trans., Gulf Coast Assoc. Geol. Soc.. 23, 122-142, 1975.

Bartok, P. E., T. J. • Reijers, and I. Juhasz, Lower Cretaceous Cogollo Group, Maracaibo Basin, Venezuela: Sedimentology, diagenesis and petrophysics, •A,P.G. Bull.. 65, 1110- 1134, 1981.

Bartok, P. E., O. Renz, and G. E.G. Westermmm, The Siquisique ophiolites, northern Lara State, Venezuela: A discussion on their Middle Jurassic ammonites and tectonic

implications, Geol. Soc. Am. Bull., 96, 1050- 1055, 1985.

Benedetto, J. L., Las unidades tecto-estratigraticas paleozoicas del norte de Sud-america, Apalacbes del sur y noroeste de Africa: comparacion y discusion, Lat. Am. Geol. Congr., 5th, 1, p. 469-488, Argentina, 1982.

Benedetto, J. L. and O. R. Odreman, Nuevas evidencias paleontlogicas en la Formacion La Quinta, su edad y correlacion con las unidades atlorantes en la Sierra de Perija, y Cordillera Oriental de Colombia, Venezuelan Geol. Cong., 5th, edited by ,• Espejo: Min. Energia y Minas and Sociedad Venezolana de

Geologos, Caracas, Venezuela, 1, p. 87-106, 1977.

Benedetto, J. L. and E. R. Puig, La secuencia sedimentaria Precambrico-Palaeozoica

Inferior pericratonica de extremo notre de Sudamerica y sus relaciones con las cuencas del Notre de Africa, Lat. Am. Geol. Congr., 5th, 2, p. 411-425, Argentina, 1982.

Bishop, W. F., Petroleum geology of northern Central America, J. Pet. Geol., 3_, p. 3-59.

Bowen, J. M., Estratigratia del Precretaceo en la parte notre de la Sierra de Perija, Venezuelan Geol. Cong., 4th, 2, p. 729-761, Caracas, Venezuela, 1972.

Buffer, R. T., Early evolution of the Gulf of Mexico Basin, in An Introduction to Central GuffCoast Geology, (pre-print), New Orleans Geolological Society, New Orleans, La., 1989.

Buffier, R. T., and D. S. Sawyer, Distribution of crust and early history of the Gulf of Mexico Basin, Trans. Gulf Coast Assoc. Geol. Soc. 35,333-344, 1985.

Burgess, W., Geologic evolution of the Mid- Continent and Gulf Coast areas - a plate tectonic view, Trans. Gulf Coast Assoc. Geol. Soc., 26, 132-143, 1976.

Burgl, H., Geologic history of Colombia: Translated from Spanish by N. R. Rowlinson, Rev. Acad. Colok Cienc. Exactas Fis. Nat.

11, 81 pp., 1963. Burgl, H., Precambrian to middle Cretaceous

stratigraphy of Colombia, translated from N. R. Rowlinson, 214 pp., privately published by N. R. Rowlinson, Bogota, Colombia, 1973.

Burke, K., Tectonic evolution of the Caribbean, Annu. Rev. Earth Planet. Sci. 16, 201- 230,1988.

Cabrera, E., El Palaeozoico en los Llanos Venezolanos, in Reunion a nivel de expertos, 25 pp., ARPEL, Quito, Ecuador, 1985.

Case, J. E., T. L. Holcombe, and R. G. Martin, Map of geologic provinces in the Caribbean region, in The Caribbean-South American Plate Boundary and Regional Plate Tectonics, edited by W. E. Bonini, R. Hargraves, and R. Shagam, Mere. Geol. Soc. Am., 162, 1-30, 1984.

Case, J. E., R. Shagam, and R. F. Giegengack, Geology of the northern Andes; An overview, in The Caribbean Region• The Geology of North America, Vol. H, edited by G. Dengo and J.E. Case, pp. 177-200, Geological Society America, Boulder Colo., 1990.

Cediel, F., J. Mojica, and C. Macia, Las formaciones Luisa, Payande, Saldana, sus columnas estratigraticas car•sticas, Geol. Norandina no. 3, 11-19, Bogota, Colombia, 1981.

Cserna, Z. de, Orogenesis in time and space in Mexico, Geol. Rundsch 50, 595-604, 1960.

Dallmeyer, R. D., 40Ar/39Ar ages ofa pre- Mesozoic crystalline basement penetrated at holes 537 and 538A of the Deep Sea Drilling Project Leg 77, southern Gulf of Mexico: tectonic implications, in Initial rep. Deep Sea Drill. Proi., 76, 496-504, 1984.

40 39 Dallmeyer, R .D., At/ Ar age of detrital

muscovite within Lower Ordovician sandstone

458 Bartok: Prebreakup of Gulf of Mexico-Caribbean and Rifting

in the coastal plain basement of Florida: Implications for west African terrane linkages, Geolo•v, • 998-1001, 1987.

Dallmeyer, R. D., Contrasting accreted terranes in the southern Appalachian orogen, basement beneath the Allantic and Gulf Coastal plaim, and West African orogens, Precambrian Res. 42, 387-409, 1989.

Dallmeyer, R. D., and J.P. Lecorche, 40Ar/39Ar polyorogenic mineral age record within the central Mauritanide orogen, West Africa, Geol. Soc. Am., Bull., 101.55-70, 1989.

Dallmeyer, R. D., M. Caen-Vachette, and M. Villeneuve, Emplacement age of post-tectonic granite in southern Guinea (West Africa) and the peninsular Florida subsurface: Implications for the origins of southern Appalachian exotic terranes: Geol. Soc. Am., Bull., 99, 87-93, 1987.

Destombes, J., C. H. Hollard, and S. Willefert, Lower Palaeozoic rocks of Morocco, in Lower Palaeozoic Rocks of Northcentral and

Westcentral Africa edited by C. H. Holland, pp. 91-336, John Wiley, New York, 1985.

Dewey, J. F., Extemional collapse oforogens, Tectonics, 7_, 1123-1140, 1988.

Donnelly, T. W., G. S. Home, R. C. Finch, and E. Lopez Ramos, North Central America; The Maya and Chortis Blocks, in The C•u4bbean Region, The Geology of North America Vol. H, edited by G. Dengo and J.E. Case, pp. 37- 76, Geological Society America, Boulder Colo., 1990.

Dunbar, J. A., and D. S. Sawyer, Implications of continental crust extension for plate reconstruction: an example from the Gulf of Mexico, Tectonics, 6_, 739-756, 1987.

Fallin, J. A. (Ed.), The Ouachita System: Oil and Gas Developments Along the Overthrust Trend• Pet. Frontiers Ser., Vol. 2, 98 pp. Petroleum Information Corp., Denver, Colo., 1985.

Fawet, P. D., and R. T. Williams, Basement beneath the Blue Ridge and Inner Piedmont in northeastern Georgia and the Carolinas: A preserved Late Proterozoic, rifled continental margin, Geol. Soc. Am. Bull., 100. 1999- 2007, 1988.

Feo-Codecido, G., C. Martin, and P. Bartok, Excursion Geologica a la Peninsula de Paraguana: 23 pp., Asoc. Venezolana de Geologia, Mineria y Petroleo, Caracas, Venezuela, 1974.

Feo-Codecido, G., F. D. Smith, N. Aboud, and E. DiGiacomo, Basement and Palaeozoic rocks of the Venezuelan Llanos bashas, in The Caribbean-South American Plate Boundary and Regional Plate Tectonics, edited by W. E. Bonini, R. Hatgraves, and IL Shagam, Mem. Geol. Soc. Am. 162, 175-188, 1984.

Fiorillo, G., Exploracion y evaluation de la Faja Petrolifera del Orinoco, in Symposium, Exploracion Petrolera en las Cuencas Subandinas de Venezuela. Colombia. Ecuador y Peru, 45 pp., Asociacion Colombiana de Geologia y. Geofisica de Petroleo, Bogota, Colombia, 1982.

Forero Suarez, A., The basement of the Eastern Cordillera, Colombia: An allocthonous terrain in northwestern South America, J. S. Am. Earth Sci.. 3_, 141-151, 1990.

Geyer, O. F., La fauna de amonites del peril tipitc de la Formacion Morrocoyal, in 1st Colombian Geological Congress, 1969, Proceedings, 111-134, Bogota, Colombia, 1976.

Gonzalez de Juana, G., J. M. Iturralbe de Arozena, and X. Picard, Geologia de Venezuela y de sus cuencas petroliferas, 1031 pp, Foninves, Caracas, 1981.

Gough, D. I., Magnetic anomalies and crustal structure inthe eastern GuffofMexico, Am. Assoc. Pet. Geol. Bull., 51, 200-211, 1967.

Handschy, J. W., O. R. Keller and K. J. Smith, The Ouachita system in northern Mexico, Tectonics, 6_, 323-330, 1988.

Hatcher, R. D., Tectonic synthesis of the Appalachian orogen, in The Appalchian- Ouachita Orogen in the United States,Geology of North America F-2, pp. 511-536 edited by R. D. Hatcher, W. Thomas, and G. W. Vide, Geological Society of America, Boulder, Colo., 1989a.

Hatcher, R. D., Appalachians introduction, in Thee Appalchian-Ouachita Orogen in the United States,Geology of North America,. F-2, pp. 1- 6, edited by R. D. Hatcher, W. Thomas, and G. W. Viele, Geological Society of America, Boulder, Colo., 1989b

Hatcher et al., Allegtmnian orogen, inTh•e Appalchian-Ouachita Orogen in the United States,Geology of North America F-2, pp. 233-318, edited by R. D. Hatcher, W. Thomas, and G. W. Vide, Geological Society of America, Boulder, Colo., 1989

Higgins, M. W., and I. Zietz, Geologic interpretation of geophysical maps of the pre- Cretaceous "basement" beneath the Coastal

Plain of Southeastern United States, in Contibutions to the Tectonics and Geophysics of Mountain Chaim• edited by R. D. Hatcher, H. Williams, and I. Zietz, Mere. Geol. Soc. Am., 158. 125-130, 1983.

Hinze, W. J., and L. W. Braile, Geophysical aspects of the craton: U.S. Sedimentary Cover - North American Craton, in Sedimentary Cover- North America The Geology of North America, D-2, edited by L. L. Sloss, pp. 5-24, Geological Society America, Boulder, Colo., 1988.

Hinze, W. J. and P. J. Hood, The magnetic anomaly map of North America; a new tool for regional geologic mapping, in Th__e Geology of North America: An Overview The Geology of North America vol. A, pp. 29-38, edited by • W. Bally and A. R. Palmer, Geological Society of America, Boulder, Col., 1988.

Hughes, C. P., A Brief Review of the Ordovician Faunas of Northern South America: Latin

American Paleontological Congress, 1• Buenos Aires, Argentina, 1, 11-22, 1980.

Irving, E. M., Structural evolution of the northernmost Andes, Colombia, U.S. Geol. Surv. Prof. Pap. 846, 47 pp, 1975.

Jaillard, E., P. 8oler, G. Carlier, and T. Mourier, The evolution of the northern and central

Andes during early to middle Mesozoic times: a Tethyan model, J. Geol. Soc. London 147, pp. 1009-1022, 1975.

Kesler, S. E., Nature of ancestral orogenic zone in nuclear Central America, Am. Assoc. Pet. Geol. Bull. • 2116-2129, 1971.

Kesler, S. E., H. Bateson, W. L. Josey, G. H. Cramer, and W. A. Simmons, Me•oscopic structural homogeneity of Maya Series and Macal Series, Mountain Pine Ridge, British Honduras, Am. A•oc. Pet. Geol. Bull.. 25, 97-123, 1971.

King, E. R., Regional magnetic map of Florida, Am.. Assoc. Pet. Geol. Bull.. 43, 2844-2854, 1959.

Kiser, G. D. and I. Bass, 1985, La Reorientacion del arco de el Baul y su importancia economica, Venezuelan Geol. Congr., 6th, 8, 5122-5135, Ministerio de Minas e Hidrocarburos, Caracas, Venezuela, 1985.

Klitgord, K. D., A Jurassic tramform plate boundary, J. Geophys. Res., • 7753-7772, 1984.

Lecorche, J.P., J. Roussel, J. Sougy, and Z. Guetat, An interpretation of the Mauritides orogenic belt (West Africa) in the light of geophysical data, in Contibutions to the Tectonics and Geophysics of Mountain Chains, edited by R. D. Hatcher, H. Williams,

and I. Zietz, Mere. Geol. Soc. Am. 158, 131- 148, 1983.

Lecorche, J.P., R. D. Dallmeyer and M. Villeneuve, Definition oftectono-stratigraphic terranes in the Mauritanide, Bass•u4de, and Rockelide orogens, West Africa, in Terranes in the Circum-Allantic Palaeozoic Orogens• edited by R. D. Dallmeyer, Spec. Pac. Geol. Soc. Am., 230, 131-144, 1989.

Lewis, J. F. and G. Draper, Geology and tectonic evolution of the northern Caribbean margin, in Geology of the northern Andes; An overview, in The Caribbean Region, The Geology of North America vol. H, edited by G. Dengo and J.E. Case, pp. 77-140, Geological Society America, Boulder Colo., 1990.

Lopez Ramos, E., Geologia de Mexico, vol. 3, 453 pp., Tesis Resendiz, Mexico, 1983.

MacDonald, W. D., Estratigrafia, estructura y metamorfismo de las rocas del Jurasico

Sueprior, Peninsula de Paraguana, Venezuela, Bol. Geol. 9, pp. 441-458, Ministerio de Minas e Hidrocarburos Venezuela, Caracas, 1983.

Mampeizer, W., Early Mesozoic bashas of the central Allantic passive margin, in Geology of Passive Margins: History, Structure and Sedimentologic Record (With Special Emphasis on the Atlantic Margin), edited by A. W. Bally et al., section 4, 60 pp., American Association of Petroleum Geologists, Tulsa, Oklahoma, 1981.

Mampeizer, W., et al., Post Palaeozoic activity, in The Geology of North America" vol. F-2, The Appalchian-Ouachita Orogen in the United States edited by R. D. Hatcher, W. Thomas, and G. W. Viele, Geolov. ical Society of America Boulder, Colo., pp. 319-374, 1989.

Martin, C., Paleotectonica del Escudo de Guayana, in IX Inter-Guayanas Geological Conference, Spec. Publ. 6_, pp. 261-305, Ministerio de Minas e Hidrocarburos Ciudad Guayana, Venezuela, 1972.

Martin, C., Tectonic map of northern South America, Ministero de Minas e Hidrocarburos de Venezuela, Caracas, 1978.

Martin Bellizzia, C., Geologia del Macizo de El Baul, Eshado Cojedes: in Venezuelan Geol. Congr., 2nd• vol. 4, pp. 1453-1530, Ministerio de Minas e Hidrocarburos de Venezuela, Caracas, 1961.

Maurrasse, F. J. M. R., Stratigraphic correlation for the circum-Caribbean region, inGeology of the northern Andes; An overview, in Th__e Caribbean Region, The Geology of North America, Vol. H, edited by G. Dengo and J.E. Case, Plates 4, 5a, 5b, Geological Society America, Boulder Colo., 1990.

May, C., and A. Traverse, Palynostratigraphy of the subsurface Eagle Mills Formation (Triassic) from a well in east-central Texas, USA, Palynology, I_.Q,0 225-234,1986.

Maze, W. B., Jurassic La Quinta Formation in the Sierra de Perija, northwestern Venezuela: Geology and tectonic environment of red beds and volcanic rocks, in The Caribbean-South American Plate Boundary and Regional Plate Tectonics, edited by W. E. Bonini, R. Hatgraves, and R. Shagam, Mere. Geol. Soc. Am., 162, 263-282, 1984.

McBride, J. H. and K. D. Nelson, Integration of COCORP deep reflection and magnetic anomaly analysis in the southeastern United States: Implications for the origin of the Brunswick and East Coast magnetic anomalies, Geol. Soc. Am. Bull 100, 436- 445, 1988.

McCollGuSh, C. N., Cano Limon Field, Llanos Basin, Colombia, in Treatise of Petroleum Geoloev. vol. ?: Structural Traps II, edited by E. A, Beaumont and N.H. Foster, pp. 65-94,

Banok: Prebreakup of Gulf of Mexico-Caribbean and Rifling 459

American Association of Petroleum

Geologists, Tulsa, Oklahoma, 1990. Meyerhoff, A- A- and C. W. Hatten, Bahamas

Salient of North America in The Geology of Continental Margins, edited by C. A. Burke and C. L. Drake, pp. 429-446, Springer- Verlag. New York, 1974.

Mueller, P. A., and $. W. Porch, Tectonic implications of Palaeozoic and Mesozoic igneous rocks in the subsurface of peninsular Florida, Trans. Gulf Coast Assoc. Geol. Soc., 33, 169-173, 1983.

Nelson, K. D, $. A. Amow, J. H. McBride, J. H. Willemin, J. Huang. L. 7.heng. J. E. Oliver, L. D. Brown, and S. Kaufman, New COCORP profiling in the southeastern United States. Part h Late Palaeozoic suture and Mesozoic

fir basins, Geology, 13,714-718, 1985. Neugebauer, J., The Iapetus model: a plate

tectonic concept for the Vailscan belt of Europe, Tectonophysics, 169, 229-256, 1989.

Opdyke, N. D., D. S. Jones, B. J. MacFaden, D. L. Smith, P. A. Mueller, and R. D. Shuster, Florida as an exotic terrain palcomagnetic and geochronologic investigation of Lower Palaeozoic rocks from the subsurface of

Florida, Geolo•v, 15,900-903, 1987. Opplin, P. L., Preliminary report on buried pre-

Mesozoic rocks in Florida and adjacent states, U.S. Geol. Surv. Circ., 91, 28 pp., 1951.

Pindell, J. L., Alleghenian reconstruction and subsequent evolution of the Gulf of Mexico, Bahamas and proto-Caribbean, Tectonics, 1-39, 1985.

Pindell, J. L. and S. F. Barrett, Geological evolution of the Caribbean region; A plate- teetectonic perspective, inGeology of the northern Andes; An overview, in The Caribbean Region, The Geology of North America, Vol. H, edited by G. Dengo and J.E. Case, pp. 405-432, Geological Society America, Boulder Colo., 1990.

Pindell, J. L., and J. F. Dewey, Triassic reconstruction of western Pangea and the evolution of the Gulf of Mexico/Caribbean

region, Tectonics, L 179-211, 1982. Rankin et al., Pre-orogenic terranes, in The

Geology of North America' vol. F-2, The Appalachian-Ouachita Orogen in the United States, edited by R. D. Hatcher, W. Thomas, and G. Viele, pp. 7-100, Geological Society America, Boulder, Colo., 1989.

Renne, P. R., J. M. MaRinson, C. W. Hatten, M. Somin, T. C. Osoott, G. Millan, and E. Linards, 40Ar/39Ar and U-Pb evidence Late Proterozoic (Grenville-age) continental crust in north-central Cuba and regional tectonic implications, Precambrian Res, 42, 325-341, 1989.

Renz, O., Geologia de la parte sureste de la Peninsula de la Guajira: Venezuelan Geol. Congr., 3rd, vol. 1, pp. 317-347, Min. Minas Hidrocarburos Venezuela, Caracas, 1960.

Richards, H. G., Stratigraphy of Earliest Mesozoic Sediments in Southeastern Mexico and

Western Guatemala, Am. Assoc. Pet. Geol. Bull., 47. 1861-1870, 1963.

Ross, M.I., and C. R. Scotesc, A hierarchical tectonic model of the Gulf of Mexico and

Caribbean region, Tectonophysics, 155. 139- 168, 1988.

Ryabukhin, A. G., V. D. Chekhovieh, L. P. Zonenshay, and V. Y. F. Khain, Evolution of the Mexican-Caribbean region (experiment in analysis in light of plate tectonics), Geotectonics, 17, 498-512, 1983.

Salvador, A., Late Triassic-Jurassic palcogeography and origin of the Guff of Mexico, Am. Assoc. Pet. Geol. Bull. 71.419- 451, 1987.

Sanchez, T. M., and J. L. Benedetto, Paleoeeologia, eomunidades bentonieas y sucesion paleoambiental en el Grupo Cachiri, Devonieo, Sierra de Perija, Venezuela, Ameghiniana, Argent. Paleontol. Soc.. 20, 163-198, 1983.

Schlager, W., et al. Deep Sea Drilling Project, Leg 77, southeastern GuffofMexieo, Geol. Soe. Am. Bull., 95,226-236, 1984.

Sehobbenhaus, C., D. de Almeida Campos, G. R. Derze, and H. E. Asmus, Geologia do Brasil, 501 pp, Ministerio MMas Energia do Brasil, Brasilia, 1984.

Schubert, C., Stratigraphy of the Jurassic La Quinta Formation, Merida Andes, Venezuela: Type section, .Z. Dtseh. geol. Ges., 137, 391- 411, 1986.

Seotese, C. R., An introduction to this volume: Palaeozoic palcomagnetism and the assembly of Pangea, in Plate Reconstruction From Palaeozoic Palcomagnetism, Geodyn. Sen, vol 12, edited by R. Van der Voo, C. R. Scotese, and N. Bonhommet, 1-10 pp, AGU, Washington D.C., 1984.

Scotese, C. R. and M. S. McKerrow, Revised world maps and introduction, in Palaeozoic Palaeogeography and BiGgeography, edited by W. S. MeKerrow, and C. R. Seotese, Mem. Geol. Soc. London 12 1-21, 1990.

Scott, K. R, W. E. Hayes and R. P. Fietz, Geology of the Eagle Mills Formation, Trans., Gulf Coast Assoc. Geol. Soc. 11, 1-14, 1961.

Sheridan, R. E., The Atlantic Passive Margin, in The Geology of North America: An Overview, The Geology of of North America, vol. A, P_l/. gl-96,_edited by A. W. Bally and A. R. Palmer, Geological Society of America, Boulder, Colo., 1989.

Smith, D. L., Review of the tectonic history of the Florida basement, Tectonophysics, 88. 1-22, 1982.

Smith, P. L., The Pliensbachian ammonite Dayiceras dayeeroides and Early Jurassic palcogeography, Can. J. Earth Sci., 20, 86-91, 1983.

Tauvers, P. R., and W. R. Muehlberger, Is the Brunswick Magnetic Anomaly really the Alleghanian suture?, Tectonics, 6_, 331-342, 1988.

Thomas, W., The Black Warrior Basin, in Sedimentary Cover- North America The Geolo•,v of North America vol. D-2, edited by L. L. Sloss, pp. 471-492, Geological Society of America, Boulder, Colo., 1999a..

Thomas, W., The Appalachian-Ouachita orogen beneath the Gulf Coastal Plain between

outcrops in the Appalachian and Ouachita Mountains, in The Appalachian-Ouachita Orogen in the United States The Geology of North America, vol. F-2, edited by R. D. Hatcher, W. Thomas, and G. W. Viele, pp. 537-554, Geological Society of America, Boulder, Colo., 1989b.

Tschanz, C. M., R. F. Marvin, J. Cruz, H. H. Mehnert, and J. T. Cebula, Geologic evolution of the Sierra Neobada del Santa

Marta, northeastern Colombia, Geol. Soc. Am. Bull. 85,273-284, 1974.

Ulloa, M. C., E. H. Perez, and B. Baldis, 1982, Unidades litoestratigraficas del Ordovicico de las Llanos Orientales de Colombia: Lat. Am.

Geol. Congr, Sth, Buenos Aires, Arg., L 109- 120, 1982.

Vernon, R., Possible future petroleum potential of Pre-Jurassie Western Gulf Basin, in Future Petroleum Provinces of the United States -

Their Geology and Potential, edited by I. H. Cram, Am. Assoc. Pet. Geol. Mem. 15,954- 979, 1970.

Walper, J. L., Tectonic evolution of the Gulf of Mexico, in The Origin of the Gulf of Mexico and the Early Opening of the Central North Atlantic, edited by R. H. Pilger, pp. 87-98, Louisiana State University Press, Baton Rouge, 1980.

Westermann, G. E.G., Ammonite biGchronology and biGgeography of the circum-Pacific Middle Jurassic, in The Ammonoidea Systematios Association edited by M. R. House and J. R. Senior, Pp. 459-498, Academic, San Diego, Calif., 1980.

Weyl, R., Geology of Central America, Beitrage zur Regionalem Geologic der Erde, 371 pp., Gebruder Borntraeger, Berlin, 1980.

Wierzbowski, A., Oxfordian ammonites of the Pinar del Rio province (western Cuba); their revision and stratigraphic significance, Acta Geol. Pol., 26, 13%260, 1976.

Williams, H. and R. D. Hatcher, Jr., Appalachian suspect terranes, in Contibutions to the Tectonics and Geophysics of Mountain Chains, edited by R. D. Hatcher, H. Williams, and I. Zietz, Mem. Geol. Soc. Am., 158, 33- 53, 1983.

Woodcock, N.H., M. A. Await, T. E. Johnson, A. H. Mackie and R. D. A. Smith, Acadian tectonics of Wales during Avalonia/Laurentia convergence, Tectonics, • 483-496, 1988.

Ziell, W., The Andes - a geological review, Beitrage zur Regionalen Geologic der Erde, 260 pp., Gebruder Borntraeger, Berlin, 1979.

P. E. Bartok, BP Research, Chertsey Road, Sunbury-on- Thames, Middlesex, England, TW16 7LN.

(Received January 16, 1990; revised January 16, 1992; accepted April 24, 1992.)