Abstract
AbstractContourite drifts are sediment deposits formed by ocean bottom currents on continental slopes worldwide. Although it has become increasingly apparent that contourites are often prone to slope failure, the physical controls on slope instability remain unclear. This study presents high-resolution sedimentological, geochemical and geotechnical analyses of sediments to better understand the physical controls on slope failure that occurred within a sheeted contourite drift within the Faroe–Shetland Channel. We aim to identify and characterize the failure plane of the late Quaternary landslide (the AFEN Slide), and explain its location within the sheeted drift stratigraphy. The analyses reveal abrupt lithological contrasts characterized by distinct changes in physical, geochemical and geotechnical properties. Our findings indicate that the AFEN Slide likely initiated along a distinct lithological interface, between overlying sandy contouritic sediments and softer underlying mud-rich sediments. These lithological contrasts are interpreted to relate to climatically controlled variations in sediment input and bottom current intensity. Similar lithological contrasts are likely to be common within contourite drifts at many other oceanic gateways worldwide; hence our findings are likely to apply more widely. As we demonstrate here, recognition of such contrasts requires multi-disciplinary data over the depth range of stratigraphy that is potentially prone to slope failure.
Highlights
Based on centimetreresolution characterization of these deposits we address the following questions: first, what is the nature of the undisturbed sediment and do material heterogeneities explain the location of the failure plane? As many aspects of cohesive landslides appear to be scale invariant, this study of a relatively small landslide may provide key insights into our understanding of much larger ones (Micallef et al 2008; Chaytor et al 2009; Baeten et al 2013; Casas et al 2016; Kuhlmann et al 2017; Clare et al 2018)
The integration of physical properties and geochemical core-log data, grain-size distribution, and geotechnical data indicate that the AFEN Slide initiated along a distinct lithological interface within the slope stratigraphy, which matches the depth of the failure plane obtained from seismic data
This lithological interface correlates with the base of a 25 cm sandy contourite layer, overlying a thick, relatively homogeneous silty clay unit
Summary
We present a detailed characterization of a bedding-parallel, cohesive submarine landslide (called the AFEN Slide), which occurred within a low angle (,2.5°) laterally extensive sheeted contourite drift, based on physical, geochemical, sedimentological and geotechnical analyses. Based on centimetreresolution characterization of these deposits we address the following questions: first, what is the nature of the undisturbed sediment and do material heterogeneities explain the location of the failure plane? We explore how climatic changes and ocean circulation may play a key role in governing not just the failure plane depth, and influence the timing of slope failure. We discuss the implications of climatically controlled sediment supply and deep ocean circulation for pre-conditioning slope instability in contourite depositional systems in oceanic gateways, which are narrow, deep passages connecting adjacent basins, elsewhere in the world
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
