Incorporation of substrate blocks into mass transport deposits: Insights from subsurface and outcrop studies

Abstract

Mass movements are common on the continental slope, affecting not only thesubsequent sea floor morphology but often substantially modifying the underly-ing deposits. Various styles of substrate interaction have been recognised, rep-resenting the various degrees of involvement of the underlying material and itsincorporation into the mass movement. This work presents a new style of basalinteraction not previously described. Based on the morphology of the basal sur-face of a mass transport deposit, this can be recognised both in seismic data andin an outcrop analogue. A subsurface example, from an ca 100 m thick masstransport deposit located in Santos Basin, offshore Brazil, displays a basal surfacewith spoon- shaped scours or scoops. These scoops are of the order of tens up to400 m in maximum dimension, where masses of underlying sediment have beenremoved and incorporated into the mass movement. Outcrops used for this workare located in La Rioja Province, Western Argentina, where the study involves awell- exposed ca 200 m thick mass transport deposit that crops out continuouslyover 7 km. Its basal surface is incised irregularly into the underlying sandstones,incorporating the blocks of sandstone into the mass movement. The strikingsimilarities observed between outcrop examples and the northern Santos Basinsuggest that they can be effective analogues, facilitating a comprehensive under-standing of mass transport deposit dynamics across diverse basin environments.