PALEOXIGENACIÓN Y PALEOPRODUCTIVIDAD EN EL GOLFO DE PANAMÁ DURANTE EL HOLOCENO TARDÍO
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Universidad Industrial de Santander
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Las condiciones paleoceanográficas del golfo de Panamá para los últimos 4.000 años fueron inferidas a partir del estudio micropaleontológico del núcleo de aguas profundas KNR176-2-MC4 (7.27°N, 78.24°W; 2.121 m.b.n.m.). La relación entre los foraminíferos bentónicos con hábitos infaunales y epifaunales muestra un incremento gradual de las formas infaunales y variaciones en la diversidad hacia el presente, lo que se interpreta como un reflejo de: (1) el detrimento de la oxigenación de los sedimentos de fondo hacia el presente y, (2) mayores efectos tafonómicos que alteran la composición original. Taxa indicadoras de condiciones de moderada oxigenación como Uvigerina proboscidea y Oridorsalis umbonatus fueron encontradas hacia la base del núcleo, mientras que hacia el tope condiciones de mayor productividad superficial y menor oxigenación son inferidas por la presencia común de Globobulimina affinis y U. proboscidea. Otros indicadores de productividad como Epistominella spp. y Uvigerina peregrina son muy comunes hacia la parte media del núcleo. La comparación del registro micropaleontológico del núcleo MC4 con registros paleoclimáticos del istmo de Panamá (Lago Woodhouse y estalagmita de Chilibrillo) muestra que una mayor recurrencia de eventos tipo El Niño a partir de 5.000 años AP, vendría acompañada de una mayor recurrencia y/o duración de fenómenos de surgencia en el golfo de Panamá. Sin embargo, el registro de susceptibilidad magnética del núcleo MC4 no muestra variaciones significativas que puedan ser comparadas con una disminución en el régimen de precipitación.
Paleocenographic conditions in the Panama Bight for the past 4000 years were inferred by using the micropaleontological record from the deep sea core KNR176-2-MC4 (7.27°N, 78.24°W; water depth 2121 m). The epifauna-infauna relationship of deep-sea benthic foraminifera and their diversity gradually increase up-core, which is interpreted as a result of: (1) a decrease in the dissolved oxygen content towards the recent and, (2) higher taphonomic effects which modify the original composition of the microfauna. Indicative taxa of moderate oxygen conditions, such as Uvigerina proboscidea and Oridorsalis umbonatus were found at the base of the core. In contrast, lower oxygenation and higher productivity conditions are inferred by the common presence of Globobulimina affinis and Uvigerina proboscidea. Additional paleoproductivity indicators such as Epistominella spp. and Uvigerina peregrina were more common in the middle part of the core. The comparison of the MC4 core micropaleontological record with several paleoclimatic records from the Panama isthmus (the Woodhouse Lake, and the Chilibrillo stalagmite) illustrates that a higher recurrence of El Niño events since 5000 years BP, could be related to a higher frequency and intensity of upwelling processes in the Panama Gulf. However, the magnetic susceptibility of the MC4 core presents variations which cannot be related with to a reduction in local rainfall.
Paleocenographic conditions in the Panama Bight for the past 4000 years were inferred by using the micropaleontological record from the deep sea core KNR176-2-MC4 (7.27°N, 78.24°W; water depth 2121 m). The epifauna-infauna relationship of deep-sea benthic foraminifera and their diversity gradually increase up-core, which is interpreted as a result of: (1) a decrease in the dissolved oxygen content towards the recent and, (2) higher taphonomic effects which modify the original composition of the microfauna. Indicative taxa of moderate oxygen conditions, such as Uvigerina proboscidea and Oridorsalis umbonatus were found at the base of the core. In contrast, lower oxygenation and higher productivity conditions are inferred by the common presence of Globobulimina affinis and Uvigerina proboscidea. Additional paleoproductivity indicators such as Epistominella spp. and Uvigerina peregrina were more common in the middle part of the core. The comparison of the MC4 core micropaleontological record with several paleoclimatic records from the Panama isthmus (the Woodhouse Lake, and the Chilibrillo stalagmite) illustrates that a higher recurrence of El Niño events since 5000 years BP, could be related to a higher frequency and intensity of upwelling processes in the Panama Gulf. However, the magnetic susceptibility of the MC4 core presents variations which cannot be related with to a reduction in local rainfall.
Keywords
deep sea benthic foraminifera, Panama basin, late Holocene, paleoceanography, aguas profundas, cuenca de Panamá, foraminíferos bentónicos, Holoceno tardío, paleoceanografía