Identification, Correlation and Origin of Multistage Landslide Events in Volcaniclastic Turbidites in the Moroccan Turbidite System

Abstract

Generation of tsunamis from submarine landslides is sensitive to several parameters such as their volume, failure mechanism and location of failure relative to sea level. These conditions are often difficult to resolve for past events. However, previous studies of turbidites generated from landslides offer insight into the timing, total event volume and failure mechanism. This study confirms the ~ 165 ka Icod landslide originating from the northern flank of Tenerife as a retrogressive multistage landslide. It also shows that the latest volcanic flank collapse from the Canary Islands, the ~ 15 ka El Golfo landslide, is a retrogressive multistage failure. These inferences are developed using high resolution Itrax μXRF bulk geochemistry to better identify and correlate these subunits in a number of core examples of the Icod (seven subunits) and El Golfo (five subunits) event beds. Subunit variations identified through Itrax studies also allow examination of bulk intra-subunit geochemical heterogeneities. These heterogeneities reflect discrete landslides from a single source. A systematic decrease in calcium composition (proxy for carbonate) suggests initial submarine collapses that retrogressively fail the flank leading to an increasing component from subaerial collapses. However, both grain size and density sorting influence bulk geochemical compositions. The geochemistry of volcanic glasses (determined from Eagle III μXRF analyses) from the subunits of the Icod and El Golfo event beds from Agadir Basin demonstrate that these subunits represent discrete separate failures.