Late Oligocene Larger Foraminifera From Nosara (Nicoya Península, Costa Rica) and Indward (Carriacou, Lesser Antilles), Calibrated by 87sr/ 86sr Isotope Stratigraphy

Baumgartner-Mora, Claudia; Baumgartner, Peter O.; Tschudin, Pascal

dc.creator	Baumgartner-Mora, Claudia
dc.creator	Baumgartner, Peter O.
dc.creator	Tschudin, Pascal
dc.date	2007-03-24
dc.date.accessioned	2016-05-03T14:25:35Z
dc.date.available	2016-05-03T14:25:35Z
dc.identifier	http://revistas.ucr.ac.cr/index.php/geologica/article/view/4215
dc.identifier	10.15517/rgac.v0i38.4215
dc.identifier.uri	https://hdl.handle.net/10669/22633
dc.description	The Late Oligocene first occurrence of Miogypsina gunteri Cole and Miogypsina tani Drooger is verified in the light of larger foraminiferal assemblages from Nosara (Nicoya Peninsula, Costa Rica) and Windward (Carriacou, Grenada, Lesser Antilles). At Windward, they co-occur with planktonic foraminifera and nannofossils studied by earlier workers. 87Sr/86Sr isotope ratios were measured in calcite of larger foraminifera at both sites to determine independent absolute ages of the two outcrops. Late Oligocene shallow water formations unconformably overlie Paleocene-Eocene distal turbidites and siliceous shales in the outcrops in Costa Rica. The shallow-water lithostratigraphy includes near shore volcanic sandstones that alternate with sandy bioclastic limestones. The latter have yielded rich assemblages of larger foraminifera that have been studied in oriented sections, SEM for split material and polished rock thin sections for transmitted light and cathodoluminescence (CL) observation. The association of larger foraminifera includes Heterostegina antillea Cushman, Miogypsina tani Drooger, Miogypsina gunteri Cole, Miogypsina c.f (Miolepidocyclina) panamensis (Cushman), Miogypsina sp., Lepidocyclina (nephrolepidina) vaughani Cushman, Lepidocyclina yurnagurensis Cushman, Lepidocyclina undosa Cushman. At Windward, scattered outcrops of the Belvedere Formation expose mass flow deposits rich in larger foraminifera associated with an early late Oligocene (NP24) planktonic foraminifa assemblage. Planktonic foraminifera and nannofossils recovered in rocks slightly downsection indicate an upper Middle Oligocene age. Larger foraminifera species collected just north of Windward include Lepidocyclina undosa Cushman and Miogypsina gunteri Cole. The 87Sr/86Sr ratio was measured in 11 specimens of megalosphaeric Lepidocyclina spp., mechanically extracted from 2 rock samples collected at Punta Peladas (Costa Rica) Ratios range from 0.709088 to 0.708196, which correspond to a model age of 27.4 to 24.94 Ma. Very similar ratios, ranging from 0.708150 to 0.708167 were obtained from Windward Village (Carriacou). All measured 87Sr/86Sr ratios fall within a Chattian (Late Oligocene) age. Nannofossils, planktonic foraminifera and identical 87Sr/86Sr ratios from Punta Peladas and Windward clearly indicate a Chattian (Upper Oligocene) first occurrence of Miogypsina gunteri and Miogypsina tani and confirm this age range for the other larger foraminifera cited above. The first occurrence of Miogypsina gunteri in the lower Aquitanian and Miogypsina tani in the upper Aquitanian as proposed by European workers cannot be confirmed.	en-US
dc.description	.	es-ES
dc.format	application/pdf
dc.language	eng
dc.publisher	Universidad de Costa Rica	es-ES
dc.relation	Revista Geológica de América Central;
dc.rights	Copyright (c) 2014 Revista Geológica de América Central	es-ES
dc.source	Revista Geológica de América Central; Revista Geológica de América Central : Número 38	en-US
dc.source	Revista Geológica de América Central; Revista Geológica de América Central : Número 38	es-ES
dc.source	2215-261X
dc.source	0256-7024
dc.title	Late Oligocene Larger Foraminifera From Nosara (Nicoya Península, Costa Rica) and Indward (Carriacou, Lesser Antilles), Calibrated by 87sr/ 86sr Isotope Stratigraphy	en-US
dc.title	Late Oligocene Larger Foraminifera From Nosara (Nicoya Península, Costa Rica) and Indward (Carriacou, Lesser Antilles), Calibrated by 87sr/ 86sr Isotope Stratigraphy	es-ES
dc.type	artículo original
dc.coverage	CRC	en-US

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