Interacción entre la topografía y las corrientes de fondo en la dinámica sedimentaria de la ZT del margen continental de Galicia

Resumo

We present an integrated facies analysis of high-resolution geochemical, magnetic, and textural data acquired from five piston cores to describe the sedimentary evolution of the sediments from the Transitional Zone (TZ) province at the Galician Continental Margin. Facies analyses revealed seven different facies, corresponding to pelagic, hemipelagic and detrital facies, the latter related to Heinrich Layers, and redeposition and abraded facies. Seafloor images and high-resolution seis- mic profiles confirmed erosional processes in the study area. Sedimentation rates have been low for the last 170 cal ka BP, especially during cold stadials. These low rates indicate strong topographic control of the bottom currents and important changes related to glacial/interglacial hydrodynamic conditions. The present-day vigorous bottom current is a consequence of the elevated topography and the confined disposition of the TZ province that causes a constriction of the water masses (MOW and LSW) and induces velocity increase of the bottom currents, enhancing their erosive capacity. During cold sta- dials, these vigorous bottom currents experience intensification because of the vertical downward migration of denser MOW water mass, resulted by the weakness of the AMOC. Thus, the topography and the glacial/interglacial hydrodynamic changes are the main factors that controlled the sedimentary dynamic of the TZ.