Stratigraphic/sedimentological studies in the Upper Cretaceous of ...
Stratigraphic/sedimentological studies in the Upper Cretaceous of southwestern Patagonia
C.E. MACELLARI
Earth Sciences and Resources Institute University of South Carolina Columbia, South Carolina 29208
Several National Science Foundation sponsored expeditions conducted during the last few years on Seymour Island (Antarctic Peninsula) have greatly increased our knowledge of the Late Cretaceous sediments exposed in this area of the world (cf. Zinsmeister 1982; Huber 1984; Macellari 1984). From these studies, it became evident that refinements were necessary in our knowledge of the stratigraphy, sedimentology, and macropaleontology of Late Cretaceous beds outcropping in southwestern Patagonia (Argentina and Chile). An expedition to undertake these studies was mounted in January 1986. Five detailed sections were measured in the Lago Argentino! Rio Turbio area (figure), which correlate with three sections measured in a previous expedition (Macellari 1985). These sections encompass a late Campanian to Paleocene sequence. Unfortunately, the sparsity of the macrofauna hinders the precise dating of thick intervals of the measured sections. This has also hampered the recognition of the Cretaceous/Tertiary boundary, except to the south (Rio Turbio) where the section is mostly marine and more fossiliferous. Field observations confirm earlier conclusions (i.e., Feruglio 1949; Cecioni 1957; Nullo, Prosperio, and Blasco de Nullo 1981; Arbe and Hechem 1984; among others) that facies became progressively more continental from south to north. Maximum progradation of continental facies was observed in latest Maastrichtian/earliest Paleocene beds. This event was followed by a widespreas transgression in the latest Maastrichtian or earliest Paleocene.
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A strong volcanic input is seen in the Paleocene beds, similar to that observed in Antarctica (Macellari 1984). Petrographic data suggest that the dominant sediment source was the Ancestral Andes to the west. Field observations south of Lago Argentino, however, demonstrate a lateral passage from shallow marine-deltaic sediments in the west to braided river deposits in the east. This indicates that during the least part of the Late Cretaceous an eastern source of sediments was present in addition to the Andean source. An effort is currently underway to identify the petrographic signature of these two sources and their differing contributions to the basin through time. The field party was composed of Marcelo Manassero (University of South Carolina), Claudio Barrio (Universidad Nacional de La Plata), and me. This ongoing research is supported by National Science Foundation grant EAR 84-18145.
References Arbe, H.A., andJ.J. Hechem. 1984. Stratigraphy and facies of continental, litoral and marine Upper Cretaceous deposits from Lago Argentino, Santa Cruz Province. Actas 9 Congreso Geologico Argentino, SC de Bariloche, 7, 124-158. (In Spanish) Cecioni, C. 1957. Age and stratigraphy of the Cerro Guido flora, Department of Ultima Esperanza, Magellanes Province, Chile. Boletino Societá Geologica Italiana, 76, 3-16. (In Italian) Feruglio, E. 1949. Geological description of Patagonia. Dirección General Yacimientos Pet roliferos Fiscales, Buenos Aires, Argentina, Tomos I-I!!. (In Spanish) Huber, B.T. 1984. Late Cretaceous foraminiferal biostratigraphy, paleoecology, and paleobiogeography of the James Ross Island region, Antarctic Peninsula.
(Unpublished Masters thesis, Ohio State University, Columbus.) Macellari, C.E. 1984. Late Cretaceous stratigraphy, sedimentology, and macropaleontology of Seymour Island, Antarctic Peninsula. (Unpublished Doctoral dissertation, Ohio State University, Columbus.) Macellari, E.C. 1985. Paleobiogeography and age of the Maorites-Gunnarites (Ammonoidea) fauna from the Upper Cretaceous of Antarctica and Patagonia. Ameghiniana, 21 (2-4), 223-242. (In Spanish) Nullo, F., C. Proserpio, and G. Blasco de Nullo. 1981. The Cretaceous in the Austral Basin between San Martin Lake and Rio Turbio. In Cuencas sedimentarias del Jurdsico y Cretdcico de America del Sur. Comite Sudamericano del Jurasico y Cretácico, 1, 181-220. (In Spanish) Zinmeister, W.J. 1982. First U.S. expedition to the James Ross Island area, Antarctic Peninsula. Antarctic Journal of the U.S., 17(5), 63-64.
ANTARCTIC JOURNAL
CORRELATION OF MEASURED SECTIONS IN SOUTHWEST PATAGONIA iI1
LLI LL
C.E. MACELLARI
Earth Sciences and Resources Institute University of South Carolina Columbia, South Carolina 29208
Several National Science Foundation sponsored expeditions conducted during the last few years on Seymour Island (Antarctic Peninsula) have greatly increased our knowledge of the Late Cretaceous sediments exposed in this area of the world (cf. Zinsmeister 1982; Huber 1984; Macellari 1984). From these studies, it became evident that refinements were necessary in our knowledge of the stratigraphy, sedimentology, and macropaleontology of Late Cretaceous beds outcropping in southwestern Patagonia (Argentina and Chile). An expedition to undertake these studies was mounted in January 1986. Five detailed sections were measured in the Lago Argentino! Rio Turbio area (figure), which correlate with three sections measured in a previous expedition (Macellari 1985). These sections encompass a late Campanian to Paleocene sequence. Unfortunately, the sparsity of the macrofauna hinders the precise dating of thick intervals of the measured sections. This has also hampered the recognition of the Cretaceous/Tertiary boundary, except to the south (Rio Turbio) where the section is mostly marine and more fossiliferous. Field observations confirm earlier conclusions (i.e., Feruglio 1949; Cecioni 1957; Nullo, Prosperio, and Blasco de Nullo 1981; Arbe and Hechem 1984; among others) that facies became progressively more continental from south to north. Maximum progradation of continental facies was observed in latest Maastrichtian/earliest Paleocene beds. This event was followed by a widespreas transgression in the latest Maastrichtian or earliest Paleocene.
78
A strong volcanic input is seen in the Paleocene beds, similar to that observed in Antarctica (Macellari 1984). Petrographic data suggest that the dominant sediment source was the Ancestral Andes to the west. Field observations south of Lago Argentino, however, demonstrate a lateral passage from shallow marine-deltaic sediments in the west to braided river deposits in the east. This indicates that during the least part of the Late Cretaceous an eastern source of sediments was present in addition to the Andean source. An effort is currently underway to identify the petrographic signature of these two sources and their differing contributions to the basin through time. The field party was composed of Marcelo Manassero (University of South Carolina), Claudio Barrio (Universidad Nacional de La Plata), and me. This ongoing research is supported by National Science Foundation grant EAR 84-18145.
References Arbe, H.A., andJ.J. Hechem. 1984. Stratigraphy and facies of continental, litoral and marine Upper Cretaceous deposits from Lago Argentino, Santa Cruz Province. Actas 9 Congreso Geologico Argentino, SC de Bariloche, 7, 124-158. (In Spanish) Cecioni, C. 1957. Age and stratigraphy of the Cerro Guido flora, Department of Ultima Esperanza, Magellanes Province, Chile. Boletino Societá Geologica Italiana, 76, 3-16. (In Italian) Feruglio, E. 1949. Geological description of Patagonia. Dirección General Yacimientos Pet roliferos Fiscales, Buenos Aires, Argentina, Tomos I-I!!. (In Spanish) Huber, B.T. 1984. Late Cretaceous foraminiferal biostratigraphy, paleoecology, and paleobiogeography of the James Ross Island region, Antarctic Peninsula.
(Unpublished Masters thesis, Ohio State University, Columbus.) Macellari, C.E. 1984. Late Cretaceous stratigraphy, sedimentology, and macropaleontology of Seymour Island, Antarctic Peninsula. (Unpublished Doctoral dissertation, Ohio State University, Columbus.) Macellari, E.C. 1985. Paleobiogeography and age of the Maorites-Gunnarites (Ammonoidea) fauna from the Upper Cretaceous of Antarctica and Patagonia. Ameghiniana, 21 (2-4), 223-242. (In Spanish) Nullo, F., C. Proserpio, and G. Blasco de Nullo. 1981. The Cretaceous in the Austral Basin between San Martin Lake and Rio Turbio. In Cuencas sedimentarias del Jurdsico y Cretdcico de America del Sur. Comite Sudamericano del Jurasico y Cretácico, 1, 181-220. (In Spanish) Zinmeister, W.J. 1982. First U.S. expedition to the James Ross Island area, Antarctic Peninsula. Antarctic Journal of the U.S., 17(5), 63-64.
ANTARCTIC JOURNAL
CORRELATION OF MEASURED SECTIONS IN SOUTHWEST PATAGONIA iI1
LLI LL
