Holocene foraminifera from the outer zone of the Bahía Blanca Estuary, Argentina (South America)

Abstract

In this study, Holocene paleoenvironmental changes were interpreted based on benthic foraminifers from a core (39°20′S-61°27′W) extracted from the Argentine Continental Shelf close to the Bahia Blanca Estuary, in the south of Buenos Aires Province. Foraminiferal fauna was determined, and found to include 44 species of 22 genera. From micropaleontological and sedimentological analysis, paleoenvironmental changes during the middle-late Holocene were recognized. Two stages were determined: from 8319–8045 to 7836-7623 Cal. yrs BP, the sediments reflected a shallow environment with estuarine conditions and low energy, enabling determination of a coastal depositional environment. As from ca. 7836–7623 up to ca. 651-557 Cal. yrs BP, the sediments indicated a passage towards to a shallow shelf environment with great marine influence, displaying a high degree of energy and oxygenation, which may have been related to a rise in sea level ca. 7836 -7623 Cal. yrs BP. The detailed study of the benthic foraminiferal fauna presented herein and the sedimentological and chronological analysis performed on the continental shelf next to the Bahía Blanca Estuary provide further proof of the relative location of the mean sea level during the middle Holocene transgressive hemicycle in Argentina.