Insights into the distribution of shallow-marine to estuarine early miocene oysters from southwestern patagonia: Sedimentologic and stable isotope constraints

The lower Miocene Estancia 25 de Mayo Formation consists of shallowmarine to estuarine deposits that bear numerous oyster shell beds distributed throughout the succession. Facies analysis reveals that oysters grew in the nearshore paleoenvironments of both the lower Quién Sabe and the upper Bandurri...

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Autores principales: Cuitiño, J.I., Santos, R.V., Scasso, R.A.
Formato: JOUR
Materias:
carbon
carbonate
colonization
environmental stress
facies analysis
isotopic composition
microstructure
mollusc
oxygen
shell
stable isotope
succession
Brazil
Estancia
Patagonia
Sergipe
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_08831351_v28_n9_p583_Cuitino
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id todo:paper_08831351_v28_n9_p583_Cuitino
record_format dspace
spelling todo:paper_08831351_v28_n9_p583_Cuitino2023-10-03T15:40:29Z Insights into the distribution of shallow-marine to estuarine early miocene oysters from southwestern patagonia: Sedimentologic and stable isotope constraints Cuitiño, J.I. Santos, R.V. Scasso, R.A. carbon carbonate colonization environmental stress facies analysis isotopic composition microstructure mollusc oxygen shell stable isotope succession Brazil Estancia Patagonia Sergipe The lower Miocene Estancia 25 de Mayo Formation consists of shallowmarine to estuarine deposits that bear numerous oyster shell beds distributed throughout the succession. Facies analysis reveals that oysters grew in the nearshore paleoenvironments of both the lower Quién Sabe and the upper Bandurrias members. Two oyster species were identified: Crassostrea(?) hatcheri, distributed in the lower two thirds of the column, and Crassostrea orbignyi, distributed in the upper third of the column within the transition from marine to the fluvial deposits of the overlying Santa Cruz Formation. Petrographic, cathodoluminiscence, and carbon and oxygen stable isotope analyses of individual growth increments were performed on carbonate from all the oyster beds, together with consecutive time-series analyses for one specimen of each species. The isotopic composition of the shell seems to be associated with the microstructure of the growth increments. Selective diagenetic alteration affected chalky growth increments; whereas translucent (foliated and prismatic) growth increments are well preserved and can be used to infer paleoenvironmental conditions. Isotopic data indicate that C.(?) hatcheri lived in normal marine waters with a range of paleotemperatures from 10.6 to 20.5 °C. Monospecific beds of this oyster are related to opportunistic and quick colonization of the sea bottom. More negative δ13C and δ18O values in C. orbignyi shells likely reflect decreased paleosalinities, and the resultant environmental stress controlled the development of these low-diversity oyster accumulations. The separate stratigraphic distribution of each species was therefore determined by the paleoenvironmental conditions. © 2013, SEPM (Society for Sedimentary Geology). Fil:Cuitiño, J.I. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Scasso, R.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_08831351_v28_n9_p583_Cuitino
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic carbon
carbonate
colonization
environmental stress
facies analysis
isotopic composition
microstructure
mollusc
oxygen
shell
stable isotope
succession
Brazil
Estancia
Patagonia
Sergipe
spellingShingle carbon
carbonate
colonization
environmental stress
facies analysis
isotopic composition
microstructure
mollusc
oxygen
shell
stable isotope
succession
Brazil
Estancia
Patagonia
Sergipe
Cuitiño, J.I.
Santos, R.V.
Scasso, R.A.
Insights into the distribution of shallow-marine to estuarine early miocene oysters from southwestern patagonia: Sedimentologic and stable isotope constraints
topic_facet carbon
carbonate
colonization
environmental stress
facies analysis
isotopic composition
microstructure
mollusc
oxygen
shell
stable isotope
succession
Brazil
Estancia
Patagonia
Sergipe
description The lower Miocene Estancia 25 de Mayo Formation consists of shallowmarine to estuarine deposits that bear numerous oyster shell beds distributed throughout the succession. Facies analysis reveals that oysters grew in the nearshore paleoenvironments of both the lower Quién Sabe and the upper Bandurrias members. Two oyster species were identified: Crassostrea(?) hatcheri, distributed in the lower two thirds of the column, and Crassostrea orbignyi, distributed in the upper third of the column within the transition from marine to the fluvial deposits of the overlying Santa Cruz Formation. Petrographic, cathodoluminiscence, and carbon and oxygen stable isotope analyses of individual growth increments were performed on carbonate from all the oyster beds, together with consecutive time-series analyses for one specimen of each species. The isotopic composition of the shell seems to be associated with the microstructure of the growth increments. Selective diagenetic alteration affected chalky growth increments; whereas translucent (foliated and prismatic) growth increments are well preserved and can be used to infer paleoenvironmental conditions. Isotopic data indicate that C.(?) hatcheri lived in normal marine waters with a range of paleotemperatures from 10.6 to 20.5 °C. Monospecific beds of this oyster are related to opportunistic and quick colonization of the sea bottom. More negative δ13C and δ18O values in C. orbignyi shells likely reflect decreased paleosalinities, and the resultant environmental stress controlled the development of these low-diversity oyster accumulations. The separate stratigraphic distribution of each species was therefore determined by the paleoenvironmental conditions. © 2013, SEPM (Society for Sedimentary Geology).
format JOUR
author Cuitiño, J.I.
Santos, R.V.
Scasso, R.A.
author_facet Cuitiño, J.I.
Santos, R.V.
Scasso, R.A.
author_sort Cuitiño, J.I.
title Insights into the distribution of shallow-marine to estuarine early miocene oysters from southwestern patagonia: Sedimentologic and stable isotope constraints
title_short Insights into the distribution of shallow-marine to estuarine early miocene oysters from southwestern patagonia: Sedimentologic and stable isotope constraints
title_full Insights into the distribution of shallow-marine to estuarine early miocene oysters from southwestern patagonia: Sedimentologic and stable isotope constraints
title_fullStr Insights into the distribution of shallow-marine to estuarine early miocene oysters from southwestern patagonia: Sedimentologic and stable isotope constraints
title_full_unstemmed Insights into the distribution of shallow-marine to estuarine early miocene oysters from southwestern patagonia: Sedimentologic and stable isotope constraints
title_sort insights into the distribution of shallow-marine to estuarine early miocene oysters from southwestern patagonia: sedimentologic and stable isotope constraints
url http://hdl.handle.net/20.500.12110/paper_08831351_v28_n9_p583_Cuitino
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