The Siquisique ophiolites, Northern Lara State, Venezuela: A discussion on their Middle Jurassic ammonites and tectonic implications

P. E. BARTOK Sohio Petroleum Company International, Exploration Department, 5151 San Felipe, Houston, Texas 77210 O. RENZ Naturhistorisches Museum, Augustinergasse 2, Basel CH-4001, Switzerland G.E.G. WESTERMANN McMaster University, Hamilton, Ontario, Canada L8S 4M1

ABSTRACT by O. Renz and G. Coronel (1959, unpub. data) basalts. The age would, therefore, confirm a pre- that indicated a Late Jurassic age and, more Callovian marine incursion into a proto-Carib- Ammonites from the pillow basalt associa- recently, by Stephan (1980) that suggested an bean rift. tions of the Siquisique ophiolites located in Early Cretaceous (Barremian) age for this west-central Venezuela indicate a minimum general area. REGIONAL GEOLOGY Bajocian to early Bathonian age for em- The new ammonite collection discussed in placement of the complex. The ammonites this paper indicates an age at least as old as Discussions on the geologic setting of the Si- have been identified as IStephanoceras Bajocian for the initial formation of the Siqui- quisique ophiolites have been, and continue to (Skirroceras) cf. macrum (Quenstedt), lEmi- sique ophiolites. The fossils appear to lie in al- be, controversial. Siquisique's veritable isolation leia ex gr. multiformis (Gottsche) et quen- tered shaley sediments enveloped by pillow from contemporaneous rock units, its complex stedti Westermann, and IParkinsonia sp. This association of cosmopolitan Pacific and Tethyan elements aids in the location of the western end of the Middle Jurassic seaway set between the Tethys and the Pacific Oceans (Hispanic Corridor). The apparent age of the ammonites indicates that some of the Siquisique sediments, pillow basalts, and serpentines are the oceanic remnants of an arrested early phase of rifting between North and South America.

INTRODUCTION

Establishing the age and structural setting of the Siquisique ophiolite complex, cropping out in west-central Venezuela, has been an elusive quest. New ammonite collections from this se- quence provide evidence for its minimum age and thus yield information pertaining to the early rifting of North and South America. The Siquisique complex lies within a region affected by Mesozoic through Tertiary deformation. Its samples were studied by Schilling and Niggli (in Shell International, 1965) and classified as an ophiolite assemblage. Early investigators, including O. Renz, in the Barqulsimeto - Flysch Basin Merida Andes-Plunging below with large debris flows con- Barquislmeto- Flysch Basin 1940s and 1950s, had postulated a Cretaceous taining Jurassic and Cretaceoua age for the strata associated with the Siquisique components Siquisique Ophiolites ophiolites because they were lithologically sim- Coastal Range Moderate to high ilar to some of the Cretaceous sediments of the Pre-Paleocene Metamorphlam V.O. Villa de Cura Volcanics Merida Andes located to the southwest (Fig. 1). Later, some ammonites were found in this area Figure 1. General location map of the Siquisique ophiolites, west-central Venezuela.

Geological Society of America Bulletin, v. 96, p. 1050-1055, 5 figs., August 1985.

1050

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geology, and lack of geophysical exploration have inhibited an understanding of its age and mode of emplacement. The Siquisique complex is surrounded by upper Tertiary sequences to the north. These overlie Mesozoic units that have been poorly explored but that appear to be a more basinal equivalent of the sediments present in the Mara- caibo Basin (Bartok and others, 1981). A Paleocene-Eocene flysch sequence containing Jurassic and mainly Cretaceous olistostromes crops out south of the study area. Two opposing views have been generally considered as pre- ferred hypotheses for emplacement of the Siqui- sique complex: (1) long-distance translation of an obducted slab of Mesozoic oceanic crust over the South American craton (Stephan, 1980) and (2) parautochthonous to autochthonous forma- tion of the Siquisique complex. The latter view is preferred by the present authors. The possibility of a westward extension of the Villa de Cura island-arc complex to include the Siquisique area (Fig. 1) (Sebastian Bell, 1983, personal commun.) appears improbable because of the Villa de Cura's geochemical affinity with, and similar age to, the Netherlands Antilles island-arc complex (Beets and others, 1984). Furthermore, the Bocono megashear (Figs. 1 and 2), having a 200-km dextral displacement (Schubert, 1984), would have placed the Siqui- sociated with northern South America terranes tamaria and Schubert, 1974). The samples dis- sique unit in a more southerly position at the have been dated. Examples of these igneous/ cussed in this report are among the oldest time of emplacement (Maze, 1984). In fact, by metamorphic units are the Sebastopol Complex sedimentary or metasedimentary sequences invoking the same offset and extending the area (±425 Ma), located in the central Coastal Range documented in the region. influenced by the Bocono fault as far north as near Caracas (Gonzales de Juana and others, Marine Jurassic early rift sequences are well the Netherlands Antilles trend, the reconstruc- 1980), and the El Amparo granite (±265 Ma) represented in the Gulf of Mexico area (Imlay, tion would juxtapose the Villa de Cura and the cropping out on the Paraguana Peninsula (San- 1943) but poorly documented in northern South Netherlands Antilles trends (Fig. 2). The possibility that the Siquisique region con- stitutes a principal suture between the Caribbean and South American plates was disputed in some parts by Bonini (1984). He contended that recently gathered aeromagnetic data indicates the existence of such a suture lying along an east-west trend located near the city of Coro (Fig. 1). This does not preclude the possibility of an earlier aborted rift, allowing for ultramafic assemblages to be introduced into a marine setting. There is ample evidence for rifting in northern South America as early as the Triassic (Bene- detto and Odreman, 1977; Salvador and Green 1980). Extensive red-bed deposition has been reported throughout the Caribbean Basin (Maze, 1984), and Jurassic marine incursions have also been observed (Renz, 1956, 1960; Geyer, 1976; Schmidt-Effing, 1981). It is within this rift framework that the Siquisique ophiolites were emplaced. Both igneous/metamorphic sequences and Figure 3. Early Middle Jurassic reconstruction of Pangea (Bernoulli, 1981; Westermann, fossil-bearing sediments and metasediments as- 1984), with approximate location of Hispanic Corridor.

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America. The oldest Mesozoic marine rift se- the Macuira Group (Renz, 1960; MacDonald, orogenic phase referred to as the Caribbean oro- quences recorded in the region (Fig. 3) are the 1968). The Rancho Grande Formation is over- gen and connected with the influx of extensive Sinemurian to Pliensbachian sediments located lain by paralic sequences of the Cocinas Group debris flows into the Barquisimeto-Guarico in the Huayacocotla Basin, Mexico (Schmidt- (Geyer, 1977), the upper unit of which contains Flysch Basins (Renz, 1982, p. 66), and (3) the Effing, 1981), and at Morrocoyal, along the Kimmeridgean ammonite suites (Renz, 1956, Andean orogeny (late Miocene-Pliocene) which northern limits of the Colombian Central Cor- 1960, p. 322). Strongly deformed normal ma- resulted in the dominant folding observed in the dillera (Geyer, 1976). Other Jurassic marine se- rine Cretaceous sediments overlie both series. Falcon Basin. quences from either the parautochthonous or These sediments are, in turn, partially covered The similarities of the sedimentary sequences allochthonous Caribbean province are now by Tertiary paralic to marine sequences (Lock- among the Guajira, Paraguana, and Siquisique documented in the Cuban Pinar del Rio prov- wood, 1966). areas, combined with their general temporal af- ince (Wiezbowski, 1976), the Colombian Gua- The basement complex of the Paraguana Pe- finity, suggest that they may represent co-genetic jira (Renz, 1956, 1960), the Paraguana Penin- ninsula is made up of the Permian El Amparo isolated terranes. The structural relationships of sula (MacDonald, 1968), and the Siquisique granite which intrudes phyllite-grade metamor- the three cannot be established, nor can their region (present report). Ammonite assemblages phics. These are overlain by an arkose com- original position be determined. The one com- in the first three suggest an Oxfordian to Titho- posed of granite wash; its sand grains contain mon element among them is that they are all nian age for their marine component. Geyer conspicuous blue quartz commonly found in the located north of, or on, the Oca and the Falcon (1977) inferred that the associated units underly- Guayana Shield granites, as well as in granites Basin fault systems (Fig. 1), as well as west of ing the fossiliferous sequences in the Guajira located north of the Cuiza fault in the Guajira the Bocono fault. may be as old as Middle Jurassic. This latter age (Renz, 1960). This unit is followed by the slaty is now documented for the Siquisique area. shales of the Pueblo Nuevo Formation that in- AGE OF THE SIQUISIQUE Local relief and proximity to marine conditions clude Late Jurassic ammonites (MacDonald, OPHIOLITES (BY WESTERMANN) appear to control the timing for the first marine 1968). Lower Miocene to Pliocene sediments occurrences in each region. Observations on the provide the present partial cover over the region Surface exposures of shales enveloped by pil- regional geology tend to disprove long-distance (Hunter and Bartok, 1976). low basalts at Petacas Creek, Algodones area migration of an obducted slab. Aside from the The Siquisique area may best be described as (Fig. 3), have yielded scarce ammonite frag- small Siquisique outcrop, there is no informa- a basement uplift containing ophiolite assem- ments, strongly indicating a Bajocian to possibly tion on rocks of comparable age to suggest such blages, metamorphic basement cropping out east early Bathonian (Middle Jurassic) age (Fig. 5). a transporting mechanism. Establishing the pre- of Petacas (Fig. 4), as well as several sedimen- There is one fragment each of (BT 26) ISteph- cise origin and mode of emplacement remains as tary sequences. The igneous rocks at Siquisique anoceras (Skirroceras) cf. macrum (Quenstedt) elusive and ambiguous as in many other ophio- are prehnitized olivine gabbros, basaltic and an- and (BT 26a) lEmileia ex gr. multiformis litic regions (Bernoulli and Lemoine, 1980). desitic extrusive rocks, spilites, and tuffs (Shell (Gottsche) et quenstedti Westermann. The age is International, 1965). probable early Bajocian, Sauzei Standard Zone COMPARISON AMONG THE The sedimentary component of the ophiolite (177 Ma; Westermann, 1984). GUAJIRA, PARAGUANA, AND suite includes conglomerates, shales (within pil- Although each of the very incomplete speci- SIQUISIQUE TERRANES low basalts), cherts, and carbonates. The con- mens cannot be specifically identified with cer- Three separate terranes located along north- glomerates consist of strongly cemented, tainty, together they are almost certainly repre- ern South America are briefly reviewed and rounded quartz pebbles. They apparently rep- sentative of the circum-global ammonite asso- compared. They are the Guajira and Paraguana resent the basal conglomerate of the Mesozoic ciation of the Sauzei Standard Zone. Both are Peninsulas, as well as the Siquisique region sequence and would suggest continental condi- similar to species found in the Jura Mountains (Fig. 1). The purpose for such a comparison is tions. The sedimentary sequences provided the of central Europe, as well as in the Andes of to highlight their similarities and discuss their fossils dated as lowermost Cretaceous by Ste- Peru, Chile, and Argentina (Westermann and differences. An understanding of these elements phan (1980). The cherts have been sampled and Riccardi, 1979; Westermann and others, 1980). may serve to resolve the discussion on their con- analyzed by the U.S. Geological Survey; how- Stephanoceras (Skirroceras) macrum (Quen- troversial origin. ever, no diagnostic Radiolaria have yet been stedt, 1883-1888) is known from both the west- The stratigraphy of the three areas can be identified. ern Tethyan region and the southeastern Pacific subdivided into three elements common to all: The major stratigraphic differences between margin; Emileia (Emileia) multiformis (1) a high-grade metamorphic complex of pre- the three areas discussed are found at Siquisique (Gottsche, 1878) is an Andean species with Mesozoic age that has been dated on the Guajira where an extensive outcrop of the Paleocene to close affinity to the central European E.(E.) and Paraguana Peninsulas by the radiometric Eocene Barquisimeto flysch sequence is ob- quenstedti (Westermann, 1964). The possibility dating of their intrusive components (Irving, served (Gonzales de Juana and others, 1980), that these are latest Jurassic berriasellids or Cre- 1975; Santamaria and Schubert, 1974), (2) a and on the Paraguana Peninsula, where an out- taceous forms has been excluded by both A. C. Mesozoic series that is lightly metamorphosed cropping ultramafic intrusive complex, Cerro Riccardi (1982, personal commun.) and J. but highly structured, and (3) unmetamor- Santa Ana, has been dated as Upper Cretaceous Wiedmann (1982, personal commun.). phosed and almost flat-lying middle to upper (Santamaria and Schubert, 1974). Two more fragmentary ammonites may be Tertiary sediments. Three major orogenic events that overprint compared with Parkirtsortia (BT 38a; Fig. 5, Along the southern portion of the Guajira Pe- each other are documented along the Southern 3a-3c). Their age would correspond to the Ba- ninsula (Fig. 1), typical Maracaibo Basin Juras- Caribbean. They are the following: (1) a sub- jocian/Bathonian boundary, (Parkinsoni-Zig- sic red beds (La Quinta Formation) grade Hercynian orogeny that resulted in eclogite and zag Standard Zones, 173 Ma; Westermann, northward into the Jurassic Rancho Grande red blueschist-grade metamorphism (Maresch, 1984). The small whorl fragments are damaged beds. Both are overlying gneisses and schists of 1979), (2) an early Tertiary (Paleocene-Eocene) and differ from known parkinsoniids in the poor

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LEGEND Formation contacts INDEX M AP Mu Undifferentiated J QUATERNARY (cherts, limestones) Fault contact

Qol Alluvium Basal conglomerates of Inferred fault Meg the Mesozoic sequence Unconformity IGNEOUS ROCKS TERTIARY S Ammonite location Oligocene - Miocene Tomic Igbe Mafic Extrusives Cerro Castillo Fm.

Mafic Intrusivos Tpem Paleocene - Eocene Igbi Matatere Flysch (gabbros) Coordinates: Maracaibo 0.-0

Figure 4. Detailed geologic map of the Algodones portion of the Siquisique ophiolites, (Lara State, Venezuela), indicating location of samples discussed in the text.

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Guajira region (Renz, 1956, 1960) reinforce a Late Jurassic age for the early Caribbean. The pillow basalt and the ultramafic association of the ophiolite shed evidence on the nature of the seaway. The most likely hypothesis is an early rift between North and South America similar to the one proposed for the Huayacocotla Basin, Mexico (Schmidt-Effing, 1981). The Late Jurassic and Early Cretaceous Ca- ribbean opening provided the mechanism for plate consumption along an island-arc complex that progressively migrated southward (Beets, 1975). Resulting obduction may explain the Coastal Range province east of the Bocono fault. The area to the west appears to have undergone less compression and more intensive wrench faulting.

CONCLUSIONS

1. The Siquisique ophiolites, particularly those in the Algodones area, are obducted oceanic material found in juxtaposition with SCALE both Upper Jurassic-Lower Cretaceous and Paleocene-middle Eocene sediments and meta- sediments. Figure 5. Ammonite from the Siquisique ophiolite. 1 = BT 26: IStephanoceras (Skirroceras) 2. The ophiolite complex was likely formed cf. macrum (Quenstedt). 2a and 2b = BT 26a: lEmileia ex gr. multiformis (Gottsche) and in an arrested rift setting. quenstedti Westermann; a = lateral view, b = ventral view. 3a-3c = BT 38a: '¡Parkinsonia sp.; a 3. The proposed Bajocian to early Bathonian = lateral view; b = ventral view; c = mould of inner whorl (BT 38b) of same?, ventral view. (Middle Jurassic) age, determined from the scarce ammonite fauna, suggests that the pillow basalts studied may be related to the early rifting between North and South America. development of the primaries, particularly on Smith's (1983) Hispanic Corridor, connecting 4. The Stephanoceras-Emileia assemblage is the inner whorls. G. Dietl (1982, personal the eastern Pacific Ocean with western Tethys the first-known early Bajocian biogeographic commun.) confirmed the generic identification, during the Early to Middle Jurassic (Hille- link between west-Tethyan, along the northern commenting that this is probably a new species brandt, 1981; Westermann, 1984) at a time Andes, and Andean (east-Pacific) occurrences of with affinity to late European Parkinsonia s.l. when the Gulf of Mexico was either still closed specific faunal elements that define the Hispanic Because the genus Parkinsonia and other Par- or hypersaiine (Imlay, 1980). Corridor (proto-Atlantic seaway). The presence kinsoniidae are unknown in the circum-Pacific of Parkinsonia, if confirmed, would suggest area, the presence of Parkinsonia in Venezuela, THE MIDDLE JURASSIC that marine connections persisted between the if confirmed, would indicate that the marine SIQUISIQUE OPHIOLITES: Tethyan Ocean and the present-day South passage in which the Siquisique sediments were THEIR SETTING IN THE Caribbean deformed belt during latest Bajocian- deposited had a connection with both the Tethys CARIBBEAN REGION earliest Bathonian times. Sea and the Pacific Ocean at a time when the endemic eastern Pacific faunas, that is, the East A Middle Jurassic age for the Siquisique ACKNOWLEDGMENTS Pacific Realm, suggest isolation from the Tethys ophiolite assemblage and a clearly marine set- Sea (Westermann, 1981). ting as established by its faunal assemblage, We appreciate the assistance given by The probably typical ammonite assemblage combined with the cosmopolitan nature of the Maraven Corporation and the cooperation of of the Sauzei Zone in Venezuela is an important ammonites, are evidence for a seaway not the Ministry of Mines and Hydrocarbons of biogeographic link between the northernmost younger than Middle Jurassic located between Venezuela. Special thanks go to James Case for Andean occurrence in Peru (Westermann and North and South America. This "corridor" must his review of the text and discussions of the others, 1980) and northwest Africa/Spain Te- have been short lived because there is strong paper, as well as to the outside readers, Sebastian thys. The northern Andes area of Venezuela evidence suggesting a Callovian age for the Bell and James Helwig. The ammonites were would thus have been part of the enigmatic origin of the Caribbean (Anderson and Schmidt, photographed by W. Suter at the Museum of western end of the proto-Atlantic seaway, 1983). Kimmeridgean ammonites found in the Natural History in Basel, Switzerland.

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REFERENCES CITED Hillebrandt, A. V., 1981, Kontinentalverschiebung und die paleozoogeo- Society of America Bulletin, v. 85, p. 1085-1098. graphischen Beziehungen des südamerikanischen Uas: Geologisches Schmidt-Effing, R., 1981, The Huayacocotla aulacogen in Mexico (Lower Anderson, F. H., and Schmidt, V. A., 1983, The evolution of Middle America Rundschau, v. 70, p. 570-581. Jurassic) and origin of the Gulf of Mexico, in Pilger, R. H., ed., The and the Gulf of Mexico Caribbean Sea region during Mesozoic time: Hunter, V., and Bartok, P., 1976, The age and correlation of the Tertiary origin of the Gulf of Mexico and the early opening of the central North Geological Society of America Bulletin, v. 94, p. 941-966. sediments of the Paraguana Peninsula, Venezuela, in Caribbean Geolog- Atlantic Ocean: Baton Rouge, Louisiana, Louisiana State University, Bartok, P. E., Reijers, T.J.A., and Juhasz, I., 1981, Lower Cretaceous Cogollo ical Conference, 7th, Guadeloupe, Proceedings, p. 497-504. p. 79-86. Group, Maracaibo Basin, Venezuela: Sedimentology, diagenesis, and Imlay, R., 1943, Jurassic formations of the Gulf region: American Association Schubert, C., 1984, Basin formation along the Bocono-Moron-El Pilar fault petrophysics: American Association of Petroleum Geologists Bulletin, of Petroleum Geologists Bulletin, v. 27, p. 1407-1533. system, Venezuela: Journal of Geophysical Research, v. 89, v. 65, p. 1110-1134. 1980, Jurassic paleobiogeography of the conterminous United States in p. 5711-5718. Beets, D. J., 197S, Superimposed island arcs along the southern margin of the its continental setting: U.S. Geological Survey Professional Paper 1062, Shell International, 1965, Igneous rocks of the Siquisique region, State of Lara: Caribbean, in Borradaile, G. J., Ritsema, A. R., Rondeel, H. F., and 134 p. Associacion Venezolana de Geologia Mineria y Petroleo Bulletin, v. 8, Simon, O. J., eds., Progress in geodynamics: Amsterdam, North Hol- Irving, E. M., 1975, Structural evolution of the northernmost Andes, Colombia: p. 286-306. land Publishing Co., p. 218-233. U.S. Geological Survey Professional Paper 846, 47 p. Smith, P. L., 1983, The Pliensbachian ammonite Dayiceras dayceroides and Beets, D. J., Maresch, W. V., Klaver, G. Th., Mottana, A., Bocchio, R., Beunk, Lockwood, J. P., 1966, Geology of the Serranía de Jarara area, Guajira Penin- Early Jurassic paleogeography: Canadian Journal of Earth Science, F. F., and Monen, H. P., 1984, Magmaiic series and high pressure sula, Colombia [Ph.D. thesis]: Princeton, New Jersey, Princeton Univer- v. 20, p. 86-91. metamorphism as constraints on the tectonic history of the southern sity, 237 p. Stephan, J. F., 1980, Un jalon de la suture Jurassique Superior-Eocretace dans Caribbean, in Bonini, W. E., Hargraves, R. B., and Shagam, R., eds., MacDonald, W. D., 1968, Estratigrafía, estructura y metamorfismo de las rocas la chaine Caraibe occidental: Les ophiolites dissociees de Siquisique, Geological Society of America Memoir 162, p. 95-130. del Jurásico Superior, Peninsula de Paraguana, Venezuela: Ministerio Venezuela, in Annual Earth Science Meeting, 8th, Marseille, France, Benedetto, G., and Odreman, O., 1977, Nuevas evidencias paleontológicas en de Minas e Hidrocarburos, Dirección de Geologia, Boletín Geologico 9, Proceedings, (pre-print). la Formacion La Quinta, su edad y correlación con las unidades p. 441-458. Westermann, G.E.G., 1964, Monographie der Otoitidae (Ammonoidea): Bei- aflorantes en la Sierra de Perija y Cordillera Oriental de Colombia: Maresch, W. V., 1979, Piave tectonic origin of the Caribbean mountain system hefte zum Geologisches Jahrbuch, v. 15,400 p. Venezuelan Geological Congress, Sth, Caracas, Proceedings, v. 1, of northern South America: Discussion and proposal: Geological So- 1984, Gauging the duration of stage: A new approach for the Jurassic: p. 87-106. ciety of America Bulletin, v. 90, p. 669-682. Episodes, v. 7, no. 2, p. 26-28. Bernoulli, D., 1981, Ancient continental margins of the Tethyan Ocean, in Maze, W. B., 1984, La Quinta Formation in the Sierra de Perija, northwestern Westermann, G.E.G., and Riccardi, R. C., 1979, Middle Jurassic ammonoid Geology of passive continental margins: American Association of Petro- Venezuela: Geology and tectonic environment of red beds and volcanic fauna and biochronology of the Argentine-Chilean Andes. Part II, Bajo- leum Geologists Education Course Note Series 19, Section 5, p. 1-36. rocks, in Bonini, W. E., Hargraves, R. B., and Shagam, R., eds., Geolog- cian Stephanocerataceae: Palaeontographica, v. 164, p. 85-188. Bernoulli, D., and Lemoine, M., 1980, Birth and early evolution of the Tethys: ical Society of America Memoir L62, p. 95-130. Westermann, G.E.G., Riccardi, A. C., Palacios, O., and Rangel, C., 1980, An overall view, in Aubouin, J., Debelmas, J., and Latreille, M., eds., Quenstedt, F. A., 1883-88, Die Ammoniten des Schwabischen Jura: Stuttgart, Jurasico Medio en el Peru: Instituto de Geologia Mineria y Metalurgia Geology of the Alpine chains born of the Tethys: Bureau de Recherches 3 volumes, atlas, 1,140 p. Bulletin, v. 9D, 47 p. Géologique et Minières Memoir IIS, p. 168-179. Renz, O., 1956, Cretaceous in western Venezuela and the Guajira (Colombia), Wiezbowski, A., 1976, Oxfordian Ammonites of the Pinar del Rio Province Bonini, W. E., 1984, Magnetic provinces of Western Venezuela: Geological in International Geological Congress, 20th, Mexico City (preprint), (western Cuba); their revision and stratigraphic significance: Acta Geo- Society of America Memoir 162, p. 161-173. 20 p. logica Polonica, v. 26, no. 2, p. 137-260. Geyer, O. F., 1976, La fauna de amonites del perfil típico de la Formacion 1960, Geologia de la parte sureste de la peninsula de la Guajira (Repúb- Morrocoy al, in Colombian Geological Congress, 1st, Bogota, 1969, lica de Colombia). Memoria III Congresso Geologico Venezoleno. - Proceedings, p. 111-134. Tomo 1, Boletín de Geologia Publicación especial 3, p. 317-346. 1977, El Jurásico de Las Peninsulas de la Guajira (Colombia) y de 1982, The Cretaceous Ammonites of Venezuela: Maraven Corporation, Paraguana (Venezuela), in Caribbean Geological Conference, 8th, ed., Basel, Birkhauser Verlag, 132 p. Curacao, Abstracts, p. 57-58. Salvador, A„ and Green, A., 1980, Opening of the Caribbean Tethys (origin Gonzalez de Juana, C., Arozena, J.M.I., and Picard, X., 1980, Geología de and development of the Caribbean and the Gulf of Mexico), in Au- Venezuela y de sus cuencas petrolíferas: Caracas, Venezuela, Fonirvves, bouin, J., Debelmas, J., and Latreille, M., eds., Geology of the Alpine v. 1, 407 p. chains born of the Tethys: Bureau de Recherches Géologiques et Mi- Gottsche, C., 1878, Uber jurassische Versteinerungen aus der Argentinischen nière Memoir No. 115, Paris, p. 224-229. MANUSCRIPT RECEIVED BY THE SOCIETY APRIL 4, 1983 Cordillera: Palaeontographica, Supplement 3, Lieferung 2, Abteilung 3, Santamaria, F., and Schubert, C, 1974, Geochemistry and geochronology of REVISED MANUSCRIPT RECEIVED JANUARY 2, 1985 50 p. the southern Caribbean northern Venezuela plate boundary: Geological MANUSCRIPT ACCEPTED FEBRUARY 11, 1985

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