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Sedimentary Geology and Sequence Stratigraphy in Continental to Shallow-Marine Deposits |
1 Centro de Investigaciones Geológicas, University of La Plata-CONICET, La Plata B1900TAC, Argentina
2 Department of Earth Sciences, University of Ottawa, 140 Louis Pasteur St, Canada K1N 6N5 Ottawa, Ontarioeschwarz{at}uottawa.ca
3 STRAT Group, Department of Earth Sciences, University of Liverpool, Liverpool L69 3GP, UK
4 Centre of Integrated Petroleum Research, University of Bergen, Allegaten 41, N-5007 Bergen, Norway
The Valanginian-aged Mulichinco Formation was deposited in the Neuquén Basin (west-central Argentina) during and immediately after a major fall in sea level, partially triggered by a tectonic inversion pulse. The formation represents a lowstand wedge where excellent outcrops, together with refined biostratigraphic coverage, have permitted the detailed examination of contemporaneous non-marine and marine deposits. Fourteen facies associations were identified in the Mulichinco Formation. They represent accumulation in a variety of environments ranging from gravelly fluvial braidplains to outer-shelf marine settings. Distribution of depositional environments, together with the identification of key surfaces and stratal patterns, has resulted in the identification of early and late lowstand, transgressive and highstand systems tracts. Accordingly, the Mulichinco lowstand wedge comprises one third-order sequence that lasted about 2 Ma and represents a lowstand sequence set. The character of shoreline sedimentation was highly variable along strike within the Mulichinco depositional area and alluvial deposits were not developed within incised valleys. Tectonically derived topography, basin physiography and fault-controlled subsidence are interpreted to have been the main controls on the evolution of the Mulichinco lowstand wedge. The results of this study have important implications for understanding both the history of Neuquén Basin and illustrating the previously undocumented architectural complexity that may exist within lowstand wedges.
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G. D. Veiga, J. A. Howell, and A. Stromback Anatomy of a mixed marine-non-marine lowstand wedge in a ramp setting. The Record of a Barremian-Aptian complex relative sea-level fall in the central Neuquen Basin, Argentina Geological Society, London, Special Publications, 2005; 252: 139 - 162. [Abstract] [PDF] |
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