The Mio-Pliocene Pisco Formation (Ica Desert, Peru) is known for its vast outcrops, which preserve one of the richest concentrations of fossil marine vertebrates on Earth. During the last thirty years, punctual studies carried out on several exceptionally well preserved individual specimens highlighted the extraordinary diversity of vertebrates that populated the area: cetaceans, pinnipeds, turtles, sea birds, and fishes are just a few examples. Through our successive fieldwork campaigns, for the first time a detailed taphonomic and stratigraphic study of the fossil assemblages from localities of the oldest strata (middlelate Miocene) of the Pisco Fm. was undertaken. Stratigraphy was used to correctly assign specimens to well-defined strata and, consequently, to evaluate the temporal variation in the composition and concentration of the fossils along the investigated stratigraphical sequence. GPS data were collected for all the fossil vertebrates and a preliminary systematic determination was carried out in the field for all the specimens, while the most interesting and well-preserved ones were taken in laboratory for preparation and detailed study. Taphonomic observations were also carried out: orientation of the skeletons, skeletal completeness, bone articulation, associated invertebrates, associated shark teeth, and evidence of bioerosion. Sediment samples enclosing the fossils were collected along the continuous vertical diatomaceous mudstone sequences and were examined through different analyses (grain size analyses, micropalaeontological analyses, major and minor elements analyses, etc.) to understand the condition of burial and to obtain a more precise dating of the fossiliferous layers, using calcareous nannoplankton (where present), diatoms, silicoflagellates, radiolarians, and dinoflagellates as biostratigraphic markers. Some of these microfossils were also used to measure as proxies to infer on paleo-depth and water paleo-temperature. Samples for radiometric Argon-Argon dating were collected in discrete tephra-beds identified in some of the investigated sequences. All the information obtained through stratigraphical and taphonomic analyses will be used and integrated to better understand the context, both physical and ecological, in which these exceptional fossil assemblages were deposited and preserved.

TAPHONOMY AND STRATIGRAPHICAL DISTRIBUTION OF MIOCENE MARINE VERTEBRATES FROM THE PISCO FORMATION (PERU)

DI CELMA, Claudio Nicola;
2014-01-01

Abstract

The Mio-Pliocene Pisco Formation (Ica Desert, Peru) is known for its vast outcrops, which preserve one of the richest concentrations of fossil marine vertebrates on Earth. During the last thirty years, punctual studies carried out on several exceptionally well preserved individual specimens highlighted the extraordinary diversity of vertebrates that populated the area: cetaceans, pinnipeds, turtles, sea birds, and fishes are just a few examples. Through our successive fieldwork campaigns, for the first time a detailed taphonomic and stratigraphic study of the fossil assemblages from localities of the oldest strata (middlelate Miocene) of the Pisco Fm. was undertaken. Stratigraphy was used to correctly assign specimens to well-defined strata and, consequently, to evaluate the temporal variation in the composition and concentration of the fossils along the investigated stratigraphical sequence. GPS data were collected for all the fossil vertebrates and a preliminary systematic determination was carried out in the field for all the specimens, while the most interesting and well-preserved ones were taken in laboratory for preparation and detailed study. Taphonomic observations were also carried out: orientation of the skeletons, skeletal completeness, bone articulation, associated invertebrates, associated shark teeth, and evidence of bioerosion. Sediment samples enclosing the fossils were collected along the continuous vertical diatomaceous mudstone sequences and were examined through different analyses (grain size analyses, micropalaeontological analyses, major and minor elements analyses, etc.) to understand the condition of burial and to obtain a more precise dating of the fossiliferous layers, using calcareous nannoplankton (where present), diatoms, silicoflagellates, radiolarians, and dinoflagellates as biostratigraphic markers. Some of these microfossils were also used to measure as proxies to infer on paleo-depth and water paleo-temperature. Samples for radiometric Argon-Argon dating were collected in discrete tephra-beds identified in some of the investigated sequences. All the information obtained through stratigraphical and taphonomic analyses will be used and integrated to better understand the context, both physical and ecological, in which these exceptional fossil assemblages were deposited and preserved.
2014
9788888793474
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11581/367192
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