Asociación Paleontológica Argentina. Publicación Especial 7 ISSN 0328-347X VII International Syrnposium on Mesozoic Terrestrial Ecosystems: 7-14. Buenos Aires, 30-6-2001

Paleoecology and environments of the Cretaceous sedimentary basins of Patagonia (southern Argentina)

Renato R. ANDREIS1

Abstract. The evolution of the continental and marine Cretaceous basins of Patagonia and adjacent areas (Chilean marine strip, basins developed around the Malvinas Islands, and the austral extremity of South America) is here considered, taking into account their origin, lithofacies, sequences, fossiliferous content, and paleodimatic changes. An attempt to separate three stages of evolution, with transitionallimits, has been made: 1) Early rift-syn-rift (Mid [urassic-Barremian): 2) Thermal sink (sag stage), and increased con- tinental sedimentation (Aptian-early Maastrichtian), and 3) The late Cretaceous transgression (late Maastrichtian-Paleocene). The first stage, during the late Triassic-Late Jurassic tectonism, produced ex- tensional faults of regional extent with EW orientation, related to the opening of the southern Atlantic Ocean. Also a marginal basin (Magallanes or Austral basin) was sketched between the active magmatic are and the stable platform with a NNW coast controlled by the Deseado Massif (Valanginian-Aptian). After the Initial Mirano events (Early Barremian) a westward regression occurs. In the San Jorge basin a pro- gressive migration of the lacustrine depocenters to the East, and en the western and southern margins of the Magallanes basin the deposition of deeper slope and pelagic facies, related to ophiolithic magmatism occurred. Between the Initial and Middle Mirano movements (base of the Aptian) another magma tic cy- de started on the western magma tic are, throwing ashes into the San Jorge basin. Simultaneously, erosion of the faulted margins of this basin caused the progradation of fan deltas into the lacustrine sediments (Matasiete Fm.) and in NW Patagonia the sea invaded the Neuquén basin, with the deposition of deep ma- rine anoxic shales, limestones, and submarine fans (Tithonian-Berriasian). This anoxic character is also common in the Malvinas, Magallanes and even the African basins. During the second stage, the Malvinas, North Malvinas and Magallanes basins indude retrogradational and aggradational successions deposited in littoral to extensive distal platforms. In the Magallanes basin a progressive regression occurs by the rise of the Proto-Cordillera and the eustatic lowering of the sea leve], while its deeper parts were filled by submarine fan deposits. The marine sedimentation continued up to the Coniacian, but coincident regres- sions occurs by the deforming intrusion of the Andean Batholith during the Main Mirano movements (Albian-Cenomanian). The late Turonian-Coniacian movements (85 My) define the end of this intrussive event. The Main Mirano movements separated the Neuquen basin from the Pacific Ocean and favoured the deposition of red fluvial dastics, evaporites and marine limestones of the Neuquen Group and of three fining-upwards fluvial cydes (Río Limay, Río Neuquen and Rio Colorado, as well (Cenornanian-early Campanian). In the San Jorge basin, the volcanic activity of the arc and subsidence processes (sag phase) allowed the deposition of thick volcanidastic successions of the Chubut Group (Castillo, Bajo Barreal and Laguna Palacios Fms.), and the Cañadón Asfalto and Los Adobes depocenter were incorporated to the new enlarged basin. The third stage shows a widespread marine transgression related to subsidence ac- celerated by the Huantraquican tectonism (83 My) and due with the continued separation of the South American and African plates (Late Campanian - Late Maastrichtian-Paleocene). The sea entered into the Colorado, Valdes and Rawson basins, and partially covered the North Patagonian platform, with the de- position of lagoonal, open bays to deep marine sediments related to Allen, Jagüe, Los Alamitos, La Colonia, Huantraico, Paso del Sapo and Lefipan Fms. Later, during the Paleocene, a southward gradual regression occurs. The sea water was warm and oxygenated, allowing the development of pelagic foraminifers, diatoms and carbonate nannofossils, but the presence of a siliceous microfauna indicats an increasing influence of polar currents.

Key words. Argentina. Patagonia. Cretaceous. Sedimentary basins. 5tratigraphy. Paleoevironrnents. Paleoecology. Introduction Gondwana. Rifting began in the Triassic and contin- ued to the Late Jurassic. Spreading and subsidence The history of the Cretaceous sedimentary basins culminated in the earliest Cretaceous with the open- of Patagonia is related to the initial break-up of ing of the South Atlantic Ocean. The related basins, developed on the eastem side of Patagonia and on 'Museo Paleontológico "Egidio Feruglio", Trelew, Argentina. the marine platform, are represented by the E-mail: [email protected] Colorado and San Jorge Basins, and other smaller ©Asociación Paleontológica Argentina 0328-347X¡01$00.00+50 8 RR Andreis basins (Valdes, Rawson, San Julián and Argentine, and are related to the opening of the Southem Urien et al., 1981;Yrigoyen, 1989a, Figueiredo et al., Atlantic Ocean, with the formation of the Africa- 1996; Marinelli and Franzin, 1996; Marinelli et al., South America passive margin, which was followed 1996;Baldi and Nevistic, 1996;Ramos, 1996;Spalletti by the northward continental separation during the et al., 1999a) (figure 1).Northeast of Patagonia, in the Early Cretaceous (130-120 My). This process pro- Buenos Aires Province, another basin was formed duced also the separation of the Colorado and during de Cretaceous (Urien et al., 1981;Juan et al., Rawson Basins from a deeper basin, the Argentine 1996; Fryklund et al., 1996). Along the permanent Basin (figure 1). The concomittant separation of .subduction zone of the Pacific Ocean floor under the Antarctica from South America and the related glob- South American Plate, Late Jurassic to Early al eustatic sea level rise produced a large transgres- Cretaceous ensialic marine back-arc troughs in cen- sive process that continued until the Hauterivian- tral Chile and west-central and southem Argentina Aptian interval. The marginal Magallanes Basin was were initiated. At the same time, an active Andean formed in southem Patagonia and adjacent Chilean volcanic are on eroded Jurassic and granitic/meta- areas by expansion of the back-arc (Riccardi and morphic basement developed. The evolved marine Rolleri, 1980;De Giusto et al., 1980;Nullo et al., 1981; and littoral successions are now exposed along the Arbe, 1989; Aguirre-Urreta, 1990; Urien and Principal Cordillera of Argentina and Chile and the Zambrano, 1996). It includes mixed transgressive Coastal Cordillera of Chile (Zambrano, 1987; Urien successions that onlap the eastem margin, with bio- and Zambrano, 1996;Spalletti et al., 1999a).The main turbated and glauconite-bearing sandy littoral facies marine basins, developed on the westem and south- (lower Springhill Formation), as well as a distal plat- westem side of Argentina, are the Neuquén and the form containing black shales and bioturbated tuffs Austral or Magallanes Basins (Urien et al., 1981;Arbe, (Río Mayer Formation) (Riccardi and Rolleri, 1980; 1989; Robbiano et al., 1996; Spalletti et al., 1999a). Arbe, 1989;Aguirre-Urreta, 1990).In the westem and Other minor basins are located around the Malvinas southem margins of the basin, along the insular vol- Islands (Urien et al., 1981;Yrigoyen, 1989b;Biddle et canic arc, there was deposition of deeper slope (sub- al., 1996; Ross et al., 1996; Galeazzi, 1996) (figure 1). marine fans and related debris flows and turbidites) They were subjected to successive marine cycles dur- and pelagic facies, including chert and basaltic flows ing the Cretaceous, but due to their tectonic instabil- (ophiolithic magmatism). This deep sedimentation ity, a great variety of other sedimentary environ- was recognised in the Rocas Verdes and Yaghan ments such as littoral, lagoonal and fluvial, occurred Basins (Biddle et al., 1986;Urien and Zambrano, 1996) during their evolution. (figure 1). The associated pyroclastic sediments were During the Late Jurassic-Late Cretaceous interval deposited during the intense are volcanism related to the continental region south of 43° LS, had a humid the opening of the basin, while on the continent a and temperate to warm paleoclimate. North of 43°LS hilly relief was covered by conifers and gym- the climate was warm and arid to semi-arid, with a nosperms, and a thick vegetation of pterydophytes well defined dry season. This paleoclimatic zonation grew along river margins, in a humid and temperate persisted, with minor variations, until the paleoclimate. Campanian. Due to the progressive expansion of the Along the north-central Patagonian coast and the Maastrichtian sea over the adjacent flat continental nearby platform, extensional faulting produced a se- areas of northem Patagonia, favourable conditions ries of hemigrabens with EW (Colorado, San Jorge, may have existed for a maritime climate with rains Valdes and Rawson Basins), or E-NE orientation (San distributed over the whole year, resulting in a tem- Julián Basin). All these basins were initially filled by perate to subtropical paleoclimate (Riccardi, 1988). alluvial fans and related fluvial systems ending with the installation of shallow lake in the Late Jurassic. The early rift and syn-rift phases The rift phase ended with the opening of the Southem Atlantic Ocean during Barremian times (Mid jurassic-Barremian) (Urien et al., 1981;Ramos, 1996).The San Jorge Basin During the Late Triassic-Late Jurassic interval, appears as an elongated depression limited by a tectonic movements produced extensional faults of number of extended, but not integrated, grabens and regional extent with preferential EW, NW-SE or semi-grabens. These structures were later intercon- NNW-SSE orientation. These produced the San nected by differential subsidence that produced the Jorge, Colorado, Malvinas, North Malvinas, East progressive enlargement of the depositional area and Malvinas, and other smaller basins (Valdes,Rawson, the inception of a lacustrine environment during the San Julián) (Urien et al., 1981; Yrigoyen, 1989a; late-rift phase. A similar evolution occurred in the Marinelli and Franzin, 1996;Ramos, 1996;Spalletti et San Julián and North Malvinas Basins (Figueiredo et al., 1999a).These movements represent the rift phase, al., 1996;Ross et al., 1996).At the same time, north of A.P.A.PublicaciónEspecial7,2001 Cretaceus sedimentary basins of Patagonia 9

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Figure 1. Cretaceous Patagonian and South Atlantic Basins. A, Tandil High; B, Río Negro High; C, Eastem Patagonia High: D, Deseado- Malvinas Arch; E, Río Chíco-Dungeness Arch; NPM, North Patagonian Massif; DM, Deseado Massif; 1, Salado Basin; 2, Neuquén Basin; 3, Colorado Basin; 4, Cañadón Asfalto Basin; 5, Valdes Basin; 6, Rawson Basin; 7, Argentina Basin; 8, San Jorge Basin; 9, El Tranquilo Basin; 10, Austral or Magallanes Basin; 11, San Julián Basin; 12, North Malvinas Basin; 13, Malvinas Basin; 14, East Malvinas Basin; 15, Yaghan Basin; A, Magmatic Are.

A.P.A. Publicación Especial 7, 2001 10 R.R.Andreis the San Jorge Basin, thick, continental, alluvial fan silicielastic and carbonate ramp facies (Picún-Leufú and fluvial sediments were deposited (the Los and Loma Montosa Formations, Armella et al., 1999), Adobes depocenter, Andreis and Dalla Salda, 1973; and littoral and red continental (conglomerates, Nullo, 1983). Whereas in the Cañadón Asfalto Basin, sandstones, fangolitas) successions (Bajada Colorada lacustrine sediments with prograding deltas were de- Formation). Later, in the early Valanginian-early posited (figure 1). Also during the Late Jurassic a Aptian oscillations of the sea level, associated with transgression from the west entered in the San Jorge diastrophic movements, produced the deposition of depression and formed a great gulf. This also cov- calcareous and shaly marine platform sediments ered an area located SW of the former basin (Río (grainstones and packstones), interbedded with mar- Mayo Basin/Tres Lagunas Formation), covering an ginal, distal, low sinuosity fluvial systems, eolian, area located SW of the San Jorge Basin (Barcat et al., and muddy lagoonal sediments (Mulichinco, Agrio, 1989). This basin was separated by a doubtful EW La Amarga and Huitrín Formations) (Riccardi, 1988; high, the Río Mayo High (Lesta et al., 1980; Scasso, Legarreta and Gulisano, 1989; Schwarz, 1999). 1989). Pteridophytes, conifers and benettitales flourished in The compressive Araucanian (Kimmeridgian) di- the marginal realm, while in the continental area astrophic phase produced a general continental rise small crocodiles and a low diversity of dinosaurs in central western Argentina and central-northern lived (Bonaparte and Gasparini, 1978; Riccardi, 1988; Chile, renewed by the compressive Mirano Initial Bonaparte, 1995). Also, on the western margin of the movements (late Hauterivian), that represent the first basin, carbonate slope facies and foetid limestone- uplift of the Cordillera Principal. Therefore, in the shale slope/basinal facies appear interbedded with Río Mayo Basin (Katterfeld/ Apeleg Formations) a lacustrine/fan delta progradation sediments. westward marine regression occured. In the San Jorge Basin a progressive migration of the successive Thermal sinking (sag) and increased shallow lacustrine depocenters to the East (until the continental sedimentation during the Aptian Albian) is recognised (Scasso, 1989; Barcat et al., up to early Maastrichtian 1989). Highly fossiliferous green-bluish to black shales, some sandstones (offshore bars) and oolitic During the thermal sag phase, the Malvinas limestones (Aguada Bandera Formation, D-129, and Plateau, North Malvinas and Magallanes Basins in- related formations) characterize the axial lacustrine elude retrogradational and aggradational succes- sedimentation (similar to the San Julián Basin) (Lesta sions deposited in littoral to extensive distal plat- et al., 1980; Barcat et al., 1989). Related to the Initial forms (Urien and Zambrano, 1996; Biddle et al., 1996; and Middle Mirano movements, a magma tic cyele Ross et al., 1996). Frequent transgressive-regressive started in the volcanic are (intermediate tuffs and ig- cyeles occured from the Cenomanian to Santonian, nimbrites, rhyolite lavas/ Payaniyeu Formation, related to the definitive separation of the Malvinas Ramos, 1981), frequently threw ash into the lacus- Plateau from South America, and may have pro- trine basin and covered the adjacent areas. However, duced eastward prograding elinoforms (Malvinas the erosion of both faulted margins of the San Jorge and Magallanes Basins). In the Colorado Basin lacus- Basin, allied to successive ash falls, caused prograda- trine deposition expanded gradually over both basin tion of fan deltas fed by braided fluvial systems margins, producing frequent onlapping (Colorado (Matasiete Formation) (Barcat et al., 1989; Baldi and Formation), but during the Barremian-Albian inter- Nevistic, 1996). mittent marine transgressions invaded the eastern In northwestern Patagonia, during the rifting part of the basin, followed by the final transgression process (that continued until the end of the (Albian-Cenomanian). The resulted in the progres- Neocomian), the sea invaded the Neuquén Basin sive substitution of marginal sandy deposits by from W and NW, depositing deep marine dark shales pelitic continental slope and pelagic deposits in the with arnmonites, micritic limestones and submarine southern part of the basin (Juan et al., 1996; Fryklund fans (and related turbidites) in the west-central part et al., 1996). of the basin during the Tithonian-Berriasian (Vaca In the Magallanes Basin the thermal sag phase (early Muerta Formation) (Riccardi, 1988; Legarreta and Valanginian to Barremian), produced the deposition of Gulisano, 1989). This persistent flooding and its transgressive sequences, mainly estuarine glauconitic anoxic character (Spalletti et al., 1999b) is common to crossbedded sands (upper Springhill Formation) that other basins (Malvinas, Magallanes, and even the onlap the passive eastem margin of the basin (Arbe, correlated African basins, Kress et al., 1996). Due to 1989). Probably, at this time, the Magallanes and San these environmental conditions, the marine micro- Jorge Basins were connected along the Chilean part of fauna shows a general low diversity. 'Iransgressive- the Cordillera. A rapid regression occurred in both mar- regressive sequences were deposited, with marginal gíns of the basin during the Barremian (Arbe, 1989), due

A.P.A. Publicación Especial 7, 2001 Cretaceus sedimentary basins of Patagonia 11 to the Initial Mirano movements (115My). This was in the Chubut Group (Bonaparte and Gasparini, caused by the rise of the Froto-Cordillera and eustatic 1978; Bonaparte, 1995). In the westem side of the lowering of the sea level.Eastward or westward flowing basin (Chile), where the Coya Machali and Las fluvial systems, prograding deltas, and littoral sedi- Chilcas Formation were deposited, marine deposits ments produced the continentalization of the marine (Turonian-Coniacian interval) are still included. basin (Río Belgrano and Piedra Clavada Formations). In westem Patagonia, the Río Mayo Basin was de- However, during the early Aptian, due to the Middle finitively closed (Spalletti et al., 1999a). However, in Mirano movements (110My), the first foreland deep the San Jorge Basin, the intermittent volcanic activity marine basin was created by a deep sea "entering" from of the volcanic are during the Late Cretaceous and the Paleo-Pacific Ocean (Arbe, 1989; Spalletti et al., subsidence processes related to sag tectonism, caused 1999a).This basin was filled with submarine fan tur- the deposition of the thick volcanoclastic successions bidites and debris flows, while in the NW area lime- of the Chubut Group (Castillo, Bajo Barreal and stones, tuffs and marginal fan-deltas grading to plat- Laguna Palacios Formations; Chebli et al., 1976;Lesta form and continental sediments, were deposited (Río et al., 1980;Riccardi, 1988;Barcat et al., 1989).Also, the Tarde,Kachaike,and Cardiel Formations).Later,several Cañadón Asfalto and the Los Adobes depocenters transgressive-regressive events characterise the late were incorporated to the new enlarged basin (Upper Albian-earlyMaastrichtian sedimentation with repeated Los Adobes and Cerro Barcino Formations; deposition of platform to slope deposits, and associated Musacchio, 1995,Manassero et al., 1998).Similar tuffs fluvial, deltaic and littoral facies (Mata Amarilla, Pari- and tuffaceous sediments were also recognized south Aike, El Alamo, and related formations). Despite the of the San Jorge Basin in the El Tranquilo Basin (fig- constant oscillations of the sea level, the marine sedi- ure 1), and are represented by the late Barremian-ear- mentation was not interrupted, but coincident regres- ly Albian Baqueró Group, that includes abundant sions were recognised in relation to the deforming in- gymnosperms (Benettitales, Conifers, Cycads), fewer trusion of the Andean Batholithduring the Main Mirano fems, and palynomorphs (Archangelsky, 1967; diastrophic phase (Albian-Cenomanian, 95 My). Baldoni, 1981;Caranza, 1988). Previously,the Andean volcanic are developed entirely The rapid fill of the ancient lacustrine environ- as a positive volcanic land separating southem South ment (Mina del Carmen, El Trebol and related forma- America from the PacificOcean (Spallettiet al., 1999a). tions) by several cycles of prograding fan deltas fed The intense volcanic activity was represented by an- by fluvial systems and related turbiditic lobes, contin- desitic, dacitic and basaltic lava flows, ignimbrites and ued, but once again became a large and isolated con- tuffs (Coyhaique and La Cautiva Formations),followed tinental depocenter. These successions are composed by basaltic flows and related fluvial deposits containing of primary massive tuffs and reworked volcaniclas- trunks, stems and leaves (Cerro Tres Picos Prieto tics (Sciutto, 1981; Meconi, 1989). The coarse cross- Formation) (Franchiand Page, 1980;Barcatet al., 1989). bedded channel sediments may contain fragments of In the Neuquén Basin (Legarreta and Gulisano, silicified tree trunks and dinosaur bones (sauropods), 1989), the Aptian-Albian marine regressive phase al- whereas shallow lakes with brackish water, marginal lowed the establishment of an extended and restrict- swamps and poorly developed paleosols are associat- ed marginal alluvial plain characterised by fluvial- ed with the extended alluvial plains. Tuffaceous sedi- eolian deposits interbedded with evaporitic facies ments are, to a large extent, replaced by zeolites (anal- (anhydrite-halite). These deposits were followed by cime, heulandite-clinoptilolite) caused by phreatic ac- evaporites and stromatolites, and marine carbonates, tivity on extended plains or the presence of shallow of the Rayoso Group and Colimapu Formation (in alkaline ponds or lakes. This suggests a semi-arid cli- Chile), characterising hypersaline conditions. The in- mate with seasonal variations (Teruggi and Rossetto, tersenonian movements (Mirano Main phase) invert- 1963;Meconi, 1989).The development of paleosols is ed the regional dip, thus definitively separating the increased in the Laguna Palacios Formation, which basin from the Pacific area. This positive character includes axial roots, prismatic structures, plants was maintained up to the Latest Cretaceous smashed by ash fall, nests of insects, phytoliths (that (Maastrichtian), and the red clastics of the Neuquén suggest colonization by herbaceous vegetation) and Group were deposited in the Cenomanian-early the pollen of angiosperms (Sciutto, 1981;Sciutto and Campanian. This Group includes three finíng-up- Martínez, 1996;González, 1999). wards cycles fluvial named Río Limay, Río Neuquén, Río Colorado Formations (Legarreta and Gulisano, The Late Cretaceous transgression 1989). These units may contain charophytes, ostra- (Maastrich tian- Paleocene) cods, opalised trunks and large sauropod remains (Riccardi, 1988; Bonaparte, 1995). Most vertebrates From the late Campanian up to the late (dinosaurs) are similar to those found farther south Maastrichtian-Paleocene a persistent and wide- A.P.A. Publicación Especial 7, 2001 12 RR Andreis spread marine transgression related to subsídence cally covered locally the Loncoche and Iagüel (late sag stage, Spalletti et al., 1999a), and accelerated Formations with glauconitic (Salamanca Formation) by tectonism (Huantraiquican movements, 83 My), or calcareous sandstones (Roca Formation). partially covered the North-Patagonian Platform. During the early Maastrichtian-Paleocene, the The Senonian continental successions, the Jurassic Magallanes Basin shows a general regressive phase, volcanic/volcaniclastic substrate (Marifil Forma- the deepest are a of the basin located in southem con- tion), and also the early Maastrichtian brackish tinental Argentina (Riccardi, 1988; Robbiano et al., basins were replaced by marine deposits. This trans- 1996). Glauconitic sandstones, shaly sediments and gressive was contemporaneous with the continued micritic mounds were deposited, and only on its separation of the South American and African Plates. northwestem margin a progradational molassic suc- The sea entered from the Atlantic Ocean along the cession (deltaic?) was formed (Calafate and La Leona Colorado Basin (and the Salado Basin as well), and Subcycles of the Lago Argentino Depositional Cycle; probably connected the Atlantic with the Pacific Arbe, 1989). In the Malvinas Basin, the Late Basins, creating new oceanic areas in which the ap- Cretaceous transgressive interval is represented by pearance of new current systems had a great influ- distal neritic to batial shaly sediments and related ence on the dispersion of the marine faunas (Riccardi, slope turbidites (Galeazzi, 1996; Biddle et al., 1996). 1988). In the Colorado, Salado, Valdes and Rawson The sea water was warm and oxygenated, as shown Basins shallow marine facies were deposited (Tavella by the presence of pelagic foraminifera, diatomites and Wright, 1996; Fryklund et al., 1996; Marinelli and and calcareous nannofossils (Galeazzi, 1996), but the Franzin, 1996). This extensive transgression is repre- presence of a siliceous microfauna near the top of the sented around the North Patagonian Massif and the sequence (??) indica tes a progressive cooling of the NW part of Patagonia (Neuquén Basin) by lagoonal sea waters, probably related to the increasing influ- (sometimes restricted), open bays to deep marine ence of polar currents. sediments. This includes the Allen and Jagüe Formations (Malargüe Group; Legarreta and References Gulisano, 1989) and the Los Alamitos, El Cain, La Colonia and related units, as well (Lesta et al., 1980). Aguirre-Urreta, M.B. 1990. Paleogeography and biostratigraphy In some units (Coli-Toro, Los Alamitos and Allen of the Austral Basin in Argentina and Chile: An appeal for Formations), the sandy sediments contain trunks, sound systematics. Episodes 13: 247-255. Andreis, RR and Dalla Salda, 1.H. 1973. Paleocorrientes en el mammal teeth, and reptile remains. Some bentonites Cretácico Inferior de las manifestaciones uraníferas Pichiñan may also occur (Allen Formation; Andreis et al., 1974; and Los Adobes (Sierra Pichiñanes, provincia de Chubut). Vallés, 1987; Impiccini, 1999). Some shallow marine Revista de la Asociación Argentina de Mineralogía, Petrología y units have been reported in the Cañadón Asfalto Sedimentología 4: 33-48. Andreis, RR, Iñiguez Rodríguez, A.M., Lluch, n. and Sabio, D.A. Basin, where pelites containing a rich Maastrichtian 1974. Estudio sedimentológico de las formaciones del fauna (Eubaculites, oysters, calcareous nannofossils, Cretácico Superior del area del Lago Pellegrini (provincia de ostracods) were deposited (Huantraico, Paso del Río Negro, República Argentina). Revista de la Asociación Sapo and Lefipan Formations; Lesta et al., 1980; Geológica Argentina 29: 85-104. Arbe, H.A. 1989. Estratigrafía, discontinuidades y evolución sed- Barcat et al., 1989). The related marginal deposits are imentaría del Cretácico en la Cuenca Austral, provincia de also characterised by sandy fluvial-deltaic succes- Santa Cruz. In: G. Chebli and 1. Spalletti (eds.), Cuencas sions and/or pelitic and pyroclastic sediments that Sedimentarias Argentinas; Universidad Nacional de Tucumán, contain palms, cycads, conifers, and angiosperms. Instituto Superior de Correlación Geológica, Serie Correlación Geológica 6: 419-442. Elsewhere, the shallow marine sediments contain Archangelsky, S. 1967. Estudio de la Formación Baqueró, plant fragments, turtle, snake, and crocodilian re- Cretácico Inferior de Santa Cruz, Argentina. Revista del Museo mains, fish teeth, freshwater mollusks, and microfos- de La Plata (Nueva Serie), 5, Paleontologia 32: 63-171. sils, whereas the sandy channel river and littoral fa- Armella, c., Cabaleri, N.G. and Leanza, H.A. 1999. Paleoambientes de la Formación Picún Leufú (límite cies may contain hadrosaur and sauropod remains, Jurásico/Cretácico) en su localidad tipo, Cuenca Neuquina, mammal teeth, and sauropod eggs and eggshells Argentina. 5° Simpósio sobre o Cretáceo do Brasil y 1° Simpósio so- (Allen and Los Alamitos Formations; Bonaparte, bre el Cretácico de América del Sur (Serra Negra, Sr, Brasil), 1995; Magalháes-Ribeiro, 1997). Hadrosaurs Boletim: 357-358. Baldi, J.E. and Nevistic, VA. 1996. Cuenca Costa Afuera del Golfo colonised the extensive littoral ecosystems (central de San Jorge. In: VA. Ramos and M.A.Turic (eds.), Relatorio 13° Patagonia) where fems and some arborescent plants Congreso Geológico Argentino y 3° Congreso de Exploración de grew on poorly developed soils, while the ti- Hidrocarburos (Buenos Aires), Geología y Recursos Naturales de la tanosaurid sauropod communities lived on higher Platajorma Continental Argentina 10:171-192. Baldoni, A. 1981. Tafofloras jurásicas y eocretácicas de América grounds nearby, where a number of nests have been del Sur. In: W. Volkheimer and E.A. Musacchio (eds.), Cuencas found (Allen Formation; Bonaparte, 1995). The grad- Sedimentarias del [urásico y Cretácico de América del Sur 2: 359- ual southwards regression during the Paleocene, 10- 391.

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Barcat, e, Cortiñas, re, Nevistic, VA and Zucchi, H.E. 1989. cuencial de la Cuenca Neuquina (Triásico Superior-Terciario Cuenca Golfo San Jorge. In: G. Chebli and 1. Spalletti (eds.), inferior). In: G. Chebli and 1. Spalletti (eds.), Cuencas Cuencas Sedimentarias Argentinas; Universidad Nacional de Sedimentarias Argentinas; Universidad Nacional de Tucumán, Tucurnán, Instituto Superior de Correlación Geológica, Serie Instituto Superior de Correlación Geológica, Serie Correlación Correlación Geológica 6: 319-345. Geológica 6: 221-243. Biddle, K.T., Snavely III, P.D. and Uliana, M.A 1996. Platea u de Lesta, P., Ferello, R and Chebli, G. 1980. Chubut extraandino. In: las Malvinas. In: VA Ramos and M.A Turic (eds.), Relatorio J.eM. Turner (ed.), Geología Regional Argentina 2: 601-654, 13' Congreso Geológico Argentino y 3' Congreso de Exploración de Academia Nacional de Ciencias, Córdoba. Hidrocarburos (Buenos Aires), Geología y Recursos Naturales de la Magalháes-Ribeíro, eM. 1997. [Descripio de caracteres morfológicos Plataforma Continental Argentina 13: 225-252. e estudo composicional de cascas de ovos de dinossauros da Formacáo Bonaparte, J.F. 1995. Dinosaurios de América del Sur. Museo Allen (Cretáceo Superior), do Bajo de Santa Rosa, provincia de Río Argentino de Ciencias Naturales "B. Rivadavia", Buenos Negro (Argentina). Dissertacáo de Mestrado, Instituto de Aires, 174 pp. Ceociéncias, Universidade Federal de Rio de [aneiro, Brasil, Bonaparte, J.E and Gasparini, Z. de 1978. Los saurópodos de los 222 pp. Unnpublished]. Grupos Neuquén y Chubut y sus relaciones cronológícas. 7' Manassero, M., Zalba, P.E., Andreis, RR and Morosi, M. 1998. Congreso Geológico Argentino (Neuquén), Actas 2: 393-406. Ambientes volcanoclásticos de la Formación Cerro Barcino Caranza, H.E 1988. [Estudio estratigráfico y paleoambiental de la (Grupo Chubut, Cretácico Superior), entre Los Altares y Las Formación Baqueró (Cretácico Inferior), en el sector norte del Plumas, Chubut, Argentina. 7' Reunión Argentina de Anfiteatro de Ticá, Depto. Magallanes, provincia de Santa Cruz. Sedimentologia (Salta), Actas: 268-279. Trabajo Final de Licenciatura, Facultad de Ciencias Exactas y Marinelli, RV and Franzín, H.J. 1996. Cuencas de Rawson y Naturales, Universidad Nacional de Buenos Aires, Argentina, Peninsula Valdés. In: VA Ramos and M.A Turic (eds.), 74 pp. Unnpublished]. Relatorio 13' Congreso Geológico Argentino y 3' Congreso de Chebli, G.A, Nakayama, e, Sciutto, J.e and Serraiotto, A.A Exploración de Hidrocarburos (Buenos Aires), Geología y Recursos 1976. Estratigrafía del Grupo Chubut en la región central dé la Naturales de la Plataforma Continental Argentina 9: 159-170. provincia homónima. 6' Congreso Geológico Argentino (Bahía Marinelli, RV, Rebay, G.A. and Franzin, H.J. 1996. Cuencas del Blanca 1975), Actas 1: 375-392. Talud Continental. In: VA Ramos and M.A Turic (eds.), De Giusto, J.M., Di Persia, eA and Pezzi, E. 1980. Nesocretón del Relatorio 13' Congreso Geológico Argentino y 3' Congreso de Deseado. In: J.eM. Turner (ed.), Geología Regional Argentina 2: Exploración de Hidrocarburos (Buenos Aires), Geología y Recursos 1389-1430, Academia Nacional de Ciencias, Córdoba. Naturales de la Plataforma Continental Argentina 18: 343-358. Figueiredo, AM.E, Miranda, AP., Ferreira, RE and Zalan, P.V Meconi, G.R 1989. [Estratigrajía y paleoambientes del Grupo Chubut 1996. Cuenca de San Julián. In: VA. Ramos and M.A. Turic en el Codo del Río Senguerr (provincia de Chubui). Trabajo Final (eds.), Relatorio 13' Congreso Geológico Argentino y 3' Congreso de Licenciatura, Facultad de Ciencias Exactas y Naturales, de Exploración de Hidrocarburos (Buenos Aires), Geología y Universidad Nacional de Buenos Aires, Argentina, 91 pp. Recursos Naturales de la Plataforma Continental Argentina 11: Unnpublished]. 193- 212. Musacchio, E.A. 1995. Estratigrafía y micropaleontología del Franchi, M.R and Page, RF.N. 1980. Los basaltos cretácicos y la [urásico y el Cretácico en la comarca del valle medio del río evolución magmática del Chubut occidental. Revista de la Chubut, Argentina. 6' Congreso Argentino de Paleontologia y Asociación Geológica Argentina 35: 208-229. Bioestmtigrafia (Trelew, 1994), Actas: 179-187. Pryklund, B., Marshall, A and Stevens, J. 1996. Cuenca del Nullo, E 1983. Descripción geológica de la Hoja 45c, Pampa de Colorado. In: VA. Ramos and M.A Turic (eds.), Relatorio 13' Agnia, provincia del Chubut. Servicio Geológico Nacional, Congreso Geológico Argentino y 3' Congreso de Exploración de Boletín 158, 78 p. Buenos Aires. Hidrocarburos (Buenos Aires), Geología y Recursos Naturales de la Nullo, E, Proserpio, e and Nullo, G.B. 1981. Estratigrafía del Plataforma Continental Argentina 8: 135-158. Cretácico Superior en el Cerro Indice y alrededores, provincia Galeazzi, JS. 1996. Cuenca de Malvinas. In: VA Ramos and M.A. de Santa Cruz. 8' Congreso Geológico Argentino (San Luis), Actas Turic (eds.), Relatorio 13' Congreso Geológico Argentino y 3' 3: 373-387. Congreso de Exploración de Hidrocarburos (Buenos Aires), Ramos, V.A. 1981. Descripción geológica de la Hoja 47a-b, Lago Geología y Recursos Naturales de la Plataforma Continental Fontana, provincia del Chubut. Servicio Geológico Nacional, Argentina 15: 273-310. Boletín 183,80 p. Buenos Aires. González, M.G. 1999. Los paleosuelos de la Formación Laguna Ramos, VA. 1996. Evolución tectónica de la Plataforma Palacios (Cretácico Superior) de Patagonia y la Formación Continental. In: VA. Ramos and M.A Turic (eds.), Relatorio 13' Asencio (Cretácico Superior-Terciario inferior) de Uruguay. 5' Congreso Geológico Argentino y 3' Congreso de Exploración de Simposio sobre o Cretáceo do Brasil y L" Simpósio sobre el Cretácico Hidrocarburos (Buenos Aires), Geología y Recursos Naturales de la de América del Sur (Serra Negra, SP, Brasil), Boletim: 65-70. Plataforma Continental Argentina 21: 385-404. Impiccini, A 1999. Correlación entre capas de bentonita de edad Riccardi, A.e 1988. The Cretaceous System of Southem South Cretácico Superior y su vinculación con las áreas volcánicas de America. Geological Societv of America, Memoir 168, 161 p. origen, en el norte de la Patagonia, Argentina. 5' Simpósio sobre Riccardi, A.e and Rolleri, E.O. 1980. Cordillera Patagónica o Cretáceo do Brasil y T' Simpósio sobre el Cretácico de América del Austral. In: J.eM. Turner (ed.), Geología Regional Argentina 2: Sur (Serra Negra, SP, Brasil), Boletim: 225-230. 1173-1306,Academia Nacional de Ciencias, Córdoba. Juan, Re, Jager, J. de, Rusell, J. and Gebhard, I. 1996. Flanco norte Robbiano, J.A, Arbe, H. and Gangui, A 1996. Cuenca Austral de la Cuenca del Colorado. In: VA Ramos and M.A. Turic Marina. In: VA. Ramos and M.A Turic (eds.), Relatorio 13' (eds.), Relatorio 13' Congreso Geológico Argentino y 3' Congreso Congreso Geológico Argentino y 3' Congreso de Exploración de de Exploración de Hidrocarburos (Buenos Aires), Geología y Hidrocarburos (Buenos Aires), Geología y Recursos Naturales de la Recursos Naturales de la Plataforma Continental Argentina 7: 117- Plataforma Continental Argentina 17: 323-342. 134. Ross, J.G., Pinchin, L Griffin, D.G., Dinkelrnan, M.G., Turic, M.A Kress, P.R, Franzin, H.J. and Marinelli, RV 1996. Cuenca de and Nevistic, VA 1996. Cuenca de Malvinas. In: VA Ramos Malvinas Oriental. In: VA Ramos and M.A Turic (eds.), and M.A Turic (eds.), Relatorio 13' Congreso Geológico Reln/orio 13° Congreso Geológico Argentino y 3' Congreso de Argentino y 3' Congreso de Exploración de Hidrocarburos (Buenos Exploración de Hidrocarburos (Buenos Aires), Geología y Recursos Aires), Geología y Recursos Naturales de la Plataforma Continental Naturales de la Plataforma Continental Argentina 16: 311-321. Argentina 14: 253-272. Legarreta, 1. and Gulisano, eA 1989. Análisis estratigráfico se- Scasso, RA 1989. La cuenca sedimentaria del Jurásico Superior y

A.PA Publicación Especial 7, 2001 14 RR Andreis

Cretácico Inferior de la región sud occidental del Chubut. In: Urien, CM. and Zambrano, J.J. 1996.E tructura de 11\ Plataforma G. Chebli and 1. Spalletti (eds.), Cuencas Sedimentarias Continental. In: v.A. Ramos and M.A. Turic (eds.), Re/atorio 130 Argentinas; Universidad Nacional de Tucumán, Instituto Congreso Geológico Argentino y 30 Congreso de Exploración de Superior de Correlación Geológica, Serie Correlación Hidrocarburos (Buenos Aires), Geología y Recursos Naturales de la Geológica 6: 395-418. Plataforma Continental Argentina 3: 29-66. Sciutto, J.C 1981. Geología del Codo del río Senguerr, Chubut, Urien, C.M., Zambrano, J.J. and Martins, 1.R. 1981. The basins of Argentina. 80 Congreso Geológico Argentino (San Luis), Actas 3: southeastern South America (Southern Brazil, Uruguay and 203-219. Eastern Argentina), incJuding south Atlantic paleogeographic Sciutto, J.C and Martínez, R. 1996. El Grupo Chubut en el anticli- evolution. In: W. Volkheimer and E.A. Musacchio (eds.), nal Sierra Nevada, Chubut, Argentina. 130 Congreso Geológico Cuencas Sedimentarias del Jurásico y Cretácico de América del Sur Argentino y 30 Congreso de Exploración de Hidrocarburos (Buenos 1: 45-125. Aires), Actas: 65-75. Vallés, J.M. 1987. Posición estratigráfica y distribución de los hor- Schwarz, E. 1999. Modelo deposicional de una plataforma mixta izontes de bentonita en Río Negro, Neuquén y La Pampa. 100 silicocJástica-carbonática afectada por olas y mareas. Un ejem- Congreso Geológico Argentino (Tucumán), Actas 2: 33. plo del Valanginiano del norte de la provincia de Neuquén, Yrigoyen, M.R. 1989a. Cuencas de Rawson y Peninsula Valdes. In: Cuenca Neuquina, Argentina. 50 Simpósio sobre o Cretáceo do G. Chebli and 1. Spalletti (eds.), Cuencas Sedimentarias Brasil y 1" Simpósio sobre el Cretácico de América del Sur (Serra Argentinas; Universidad Nacional de Tucumán, Instituto Negra, SP, Brasil), Boleiim: 175-180. Superior de Correlación Geológica, Serie Correlación Spalletti, L., Franzese, J.R., MacDonald, D. and Pérez, LG. 1999a. Geológica 6: 467-476. Paleogeographic evolution of southern South Arnerica during Yrigoyen, M.R. 1989b. Cuenca de Malvinas. In: G. Chebli and 1. the Cretaceous. 50 Simpósio sobre o Cretáceo do Brasil y 1" Spalletti (eds.), Cuencas Sedimentarias Argentinas; Universidad Simpósio sobre el Cretácico de América del Sur (Serra Negra, SP, Nacional de Tucumán, Instituto Superior de Correlación Brasil), Boletim: 87-95. Geológica, Serie Correlación Geológica 6: 481-492. Spalletti, L., Veiga, G., Gasparini, Z., Schwarz, E., Fernández, M. Zambrano, J.J. 1987. Las cuencas sedirnentarias de América del and Matheos, S. 1999b. La rampa marina de la transición Sur durante el Jurásico y Cretácico. Su relación con la activi- [urásico-Cretácico en la Cuenca Neuquina (Argentina): facies dad tectónica y magmática. In: W. Volkheimer (ed.), anóxicas, procesos deposicionales y herpetofauna. 50 Simpósio Bioestratigrafía de los sistemas regionales del Jurásico y Cretácico de sobre o Cretáceo do Brasil y 1o Simpósio sobre el Cretácico de América del Sur Buenos Aires, 1: 1-48. América del Sur (Serra Negra, SP, Brasil), Boletim: 345-348. Tavella, G.E and Wright, CG. 1996. Cuenca del Salado. In: V.A. Ramos and M.A. Turic (eds.), Relatorio 130 Congreso Geológico Argentino y 30 Congreso de Exploración de Hidrocarburos (Mendoza), Geología y Recursos Naturales de la Plataforma Continental Argentina 6: 95-116. Teruggi, M.E. and Rossetto, A. 1963. Petrología del Chubutiano del Codo del río Senguerr. Boletín de Informaciones Petroleras (YPF) 354: 18-35. Buenos Aires. Accepted: November 9"', 2000.

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