Cambios paleoambientales en el Cuaternario de la plataforma marina de las Guayanas detectados por medio del foraminífero Ammonia tepida

Abstract

The specimens of the Ammonia tepida foraminifera, found in 4 cores extracted from the Guianas continental shelf, have been studied. This species indicates the presence of waters of Amazonian origin in this shelf. The analysis of its distribu- tion, together with Carbon-14 dating, has allowed us to identify four units that characterize oceanographic changes recorded throughout the Quaternary. Unit 4, dated between 42,350 and 37,377 years cal BP, represents a coastal environment with strong dynamics and free of the Amazonian influence in the current 47 m isobath. Unit 3 (26,071-13,302 years cal BP) shows the existence of an old coastline, without Amazonian influence, where the outer shelf is currently located. Unit 2 (9720-1086 years cal BP) indicates shallow, low oxygen and evaporitic environments, especially in cores obtained at small depths. Unit 1 indicates the most recent sedimentation (1086 years cal BP- Present). Ammonia tepida is very abundant in areas less than 20 m deep, where mud banks originate from the suspended load of Amazonian origin.