Sedimentology of bottom current processes and their bedforms, The

Abstract

This doctoral thesis (this work) is aimed at better understanding ocean bottom current processes and their bedforms in the contexts of 1) ancient outcrops, 2) modern oceans and 3) geophysical bedform processes. First, Miocene Rifian Corridor deposits in Northern Morocco are described, which have been interpreted to have formed under the action of ocean bottom currents. The independent paleontological, sedimentary, and stratigraphic analysis presented in this work shows that these deposits have likely been misinterpreted and actually represent shallow marine tide-dominated delta deposits. The implications of these findings to our understanding of ancient bottom current deposits in an outcrop are discussed and independent interpretations for these sediments are outlined. Second, the abyssal plain geomorphologies are compiled and analyzed to illustrate the bedform types and the diversity of ocean bottom current-controlled landscapes. This work shows that ocean bottom current deposits comprise mostly of migrating dunes and have morphological, sedimentological, and process similarities to aeolian deposits. Compiled abyssal dune data is then used to develop a global map with regions of ocean bottom deposition, erosion, and stasis. A separate chapter of this work discusses the use of ocean floor sediment core to quantify the origin of oceanic sediments, and documents that on average ± 8% of the sediments on the ocean floor are derived from authigenic suspension fallout, as compared to ± 92% that is detrital sediment derived from continental sources. The final two chapters of this work examine active aeolian systems to define physical laws of dune formation and migration, showing that the shapes and migration rates of dunes are controlled by surface-to-volume ratios. These laws are then applied to better understand the role of topography on dune morphology transitions.