Introduction: Special issue on bottom currents and contourites: Processes, products and impact

This special issue of Marine Geology, published following the 4th Deepwater Circulation (4DWC) Conference held in Edinburgh, 2023, represents a state-of-the-art perspective on oceanographic processes and their depositional products, broadly referred to as contourite systems. With over seven years since the last major compilation of studies on contourite systems (Van Rooij et al., 2016) and the last major review paper (Rebesco et al., 2014), there are numerous developments in this field of research that are documented here. This includes the integration of physical oceanographic observations and measurements with numerical modelling; documentation of previously undescribed active systems, and their influence on the seafloor; new Pleistocene-Holocene sedimentary records of contourites documenting changes in current dynamics on centennial to millennial timescales; ancient (Cenozoic) contourite systems and their record of the evolution of tectonically controlled ocean gateways; mixed turbidite-contourite (hybrid) depositional systems; and new integrated perspectives of geohazards in contourite systems (Fig. 1). These case studies cover all of Earth's major oceans at different latitudes, as well as smaller marginal seas and fjord systems, giving a unique perspective on these different marine environments and oceanographic conditions. These individual contributions are described below according to the main focus of each paper, although many contribute to multiple different themes.