Contourites and paleo-gateways: An integrative ichnological and sedimentological approach

Abstract

Closing and opening of ocean paleo-gateways strongly influenced the tectono-stratigraphic and sedimentary evolution of basins, affecting global ocean circulation, climate, sedimentary processes, and living biota. Particularly, closing and opening of ocean paleo-gateways determine significant changes in ocean dynamic affecting deepwater circulation, and then deepsea sedimentary facies and benthic community. Changes in bottom-current dynamic and their effects (e.g., erosion, nondeposition and variable rate of deposition) can cause changes in substrate features that might exert a major effect on the benthic habitat. To improve knowledge of paleo-gateways, involved oceanographic processes, and variations in the depositional systems, detailed analysis of the Contourite Depositional Systems and associated sediments controlled by deep-water circulation processes reveals of major interest. In this context an integrative ichnological and sedimentological approach is proved as a useful strategy.This study focuses in the application of an integrative sedimentological (i.e., primary sedimentary structures, grain size analysis, microfacies, etc.) and ichnological approach to improve characterization of contourites and differentiation from other deep-sea facies associated to paleo-gateways. Examples from middle Miocene contourite deposits in Cyprus associated to the Indian Gateway, the late Miocene contourites Morocco related to the Rifian Corridor and from the Pliocene and Quaternary deposits in the Gulf of Cadiz related to the Strait of Gibraltar are presented. Changes in paleoenvironmental (ecological and depositional) conditions induced by gateways evolution, as hydrodynamic energy, rate of sedimentation, organic matter availability, affecting tracemaker community are interpreted based on integration of sedimentological and ichnological features.