Das marine Eozän in Zentralchile - Stratigraphie, Fazies, Paläogeographie und Fauna einer vernachlässigten Zeitscheibe
Final Report Abstract
Here we revise the stratigraphy, chronostratigraphy, sedimentology, petrography, ichnology and micropaleontology of marine sediments of Paleogene age on the Arauco peninsula and Mocha Island in central Chile. The sequence is regionally known as the Lebu Group and is conformed by the Curanilahue, Bocalebu, Trihueco, and Millongue formations. The sequence of these units corresponds to a complex alternation of prograding and retrograding siliciclastic shoreline and deltaic cycles, controlled by subsidence and uplifting of tectonic blocks. The base of the Lebu Group is characterized by an angular disconformity with Paleozoic basement, or an erosional disconformity with the top of the Quiriquina Formation with a maximum depositional age of 64 Ma, thus suggesting that the top of this Maastrichtian unit may have reached the Paleogene. A zircon age from the base of the Curanilahue Formation, above the disconformity, resulted in a maximum depositional age of 57 Ma, thus indicating a hiatus of 7 Ma across the Cretaceous-Paleogene boundary. Zircon ages corresponding to the base and middle part of the Millongue Formation, indicate maximum depositional ages of 50-52 Ma. These radiometric data correspond to planktonic foraminiferal ages from the middle and upper Millongue and Bocalebu formations that indicate Zones E10-E11 of the Lutetian-Bartonian transition (Middle Eocene). Retrogradational parasequences within the Bocalebu and Millongue Formations display typical signatures of storm-wave influence, showing alternances between fair-weather and storm events. Frequent sedimentary structures in storm-beds include hummocky-cross and trough-cross stratification, erosional truncations, horizontal or parallel lamination, and low ichnodiversity. Soft-sediment deformation structures result from synsedimentary palaeoseismic events. Fair-weather suites present the archetypal Cruziana Ichnofacies (Asterosoma, Rosselia, Planolites, Chondrites, Palaeophycus, Thalassinoides, Teichichnus, Rhizocorallium). The uppermost part of the sequence is composed by shelf and turbiditic deposits, exhibiting a low to moderate ichnodiversity (Zoophycos, Chondrites, Phycosiphon, Lophoctenium, Phycodes and Scolicia), and illustrating the Zoophycos Ichnofacies. Members of the nautilids Aturia, Hercoglossa, Cimomia and Eutrephoceras were detected in the Lebu Group. Cimomia and Eutrephoceras are generally rare, while Aturia is more abundant and displays sexual dimorphism. A mass occurrence of Hercoglossa was detected in a single m-thick unit of the Millongue formation that is stratigraphically close to the MECO event (Maximum Eocene Climate Optimum).
Publications
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2012. Change from tide-dominated to wave-influenced shoreface systems in the transition Trihueco-Millongue Formation (Middle Eocene), Arauco Basin, Chile Central: An effect of paleoseismic-eustatic events. Of Land and Sea: Processes and Products. GV and SEDIMENT. Hamburg, Germany
Patricio Zambrano
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2012. Nautiloideos Paleogenos de Chile Central. XIII Congreso Geologico Chileno. Universidad de Antofagasta, Chile
Patricio Zambrano y Sven N. Nielsen
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2012. Sedimentología e icnología de eventos transgresivos durante el Paleógeno de Chile Central (Península de Arauco). Antecedentes para la aplicación de estratigrafía secuencial en parasecuencias. XIII Congreso Geológico Chileno. Universidad de Antofagasta, Chile
Patricio Zambrano, Alfonso Encinas and Sven Nielsen
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2014. Ichnological signatures of prograding and retrograding parasequence sets: an example from the Paleogene of the Arauco basin, south-central Chile. 23rd Latin 2merican Colloquium. Heidelberg, Germany
Patricio Zambrano, Luis Buatois, Alfonso Encinas, Sven Nielsen and Wolfgang Stinnesbeck
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2014. Interacción depredador-presa inferida por asociación de trazas de bioturbación (Piscichnus-Ophiomorpha) del Eoceno de Punta Lavapie (Península de Arauco, 37°s, chile). IV Simposio Paleontológico Chileno, Valdivia, Chile
Fernando Muñiz, Patricio Zambrano, Alfonso Encinas and Masakazu Nara
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2014. Sedimentology and Ichnology of a Paleogene wave-dominated delta in Mocha Island, Central Chile. XIV Reunion Argentina de Sedimentologia. Puerto Madryn, Argentina
Patricio Zambrano, Alfonso Encinas, Luis Buatois, Ignacio Arenillas, Wolfgang Stinnesbeck and Sven Nielsen
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2014. Sedimentology, age and provenance of Paleogene delta systems from Central Chile. XIV Reunion Argentina de Sedimentologia. Puerto Madryn, Argentina
Patricio Zambrano, Alfonso Encinas, Luis Buatois, Ignacio Arenillas, Wolfgang Stinnesbeck and Sven Nielsen
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2014. Taxonomy and Taphonomy of nautiloids from Paleogene of Central Chile. 4th International Palaeontological Congress, Mendoza, Argentina
Patricio Zambrano, Sven Nielsen and Wolfgang Stinnesbeck
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2014. Taxonomía y relaciones tafonómicas en los Nautiloideos Paleógenos de Sudamérica. IV Simposio Paleontológico Chileno, Valdivia, Chile
Patricio Zambrano, Sven Nielsen and Wolfgang Stinnesbeck
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2014. Traces fossils of the Glossifungites, Skolithos, Cruziana and Zoophycos ichnofacies in Paleogene parasequences from the Arauco basin, Chile central. Ichnotaxonomy 2014, Smolenice, Bratislava
Patricio Zambrano, Luis A. Buatois, Francisco J. Rodríguez-Tovar, Alfonso Encinas, Sven N. Nielsen, and Wolfgang Stinnesbeck
