Contourite channels – Facies model and channel evolution

Abstract

Despite the rise in published evidence of deep-marine bottom current processes and associated deposits there are still very few documented outcrop examples. Herein are reported results of a contourite channel system related to the late Miocene palaeo-Mediterranean Outflow Water in the Rifian Corridor, Morocco. This work aims to unravel the sedimentary evolution and facies distribution based on the study of large morphological features related to contourite channels and their subsequent sandstone dominated infill sequences. It was found that the channel evolution and facies distribution are related to spatiotemporal changes in flow characteristics of the palaeo-Mediterranean Outflow Water. The recognized channel facies distribution correlates well with previously established bedform stability diagrams. Erosion and upper-stage flow regime bedforms are associated with the most vigorous bottom currents, generally related to its core. Laterally, following the decrease in flow velocity towards the adjacent drift, bedforms comprise dunes, lower-stage plane bedforms and more heterolithic facies. Similar facies changes are also observed down-channel, related to a decrease in flow velocities resulting from turbulent mixing of water masses, associated decreases in density gradients and the subsequent deceleration due to gravity. Results of this work have been used to propose a three-dimensional facies model for channelized sandy contourites. This study contributes to understanding contourite systems, thus benefitting oceanographic and climatic reconstructions as well as aiding the predictability of contourite channel systems for industry geoscience applications.