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Journal of the Geological Society

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Tectonic framework of the mud mounds, associated BSRs and submarine landslides, offshore Nicaragua Pacific margin

¹ IFM-GEOMAR, Research Center for Marine Science, Wischhofstrasse 1–3, 24148 Kiel, Germany (e-mail: atalukder{at}ifm-geomar.de)
² University of Birmingham, Birmingham B15 2TT, UK

The regional distribution of mounds, associated bottom-simulating reflectors (BSRs) and submarine landslides of the Pacific margin of Nicaragua suggests a genetic relationship between them. In the landslide-dominated parts of the margin, mud mounds occur in groups upslope behind the scarps and aligned parallel to the headwall. The morphotectonic features associated with the slides suggest that the slope failure could be triggered by slope oversteepening on the trailing flank of subducted seamounts. Geometric analysis of the faults triggering and controlling the mud mounds and associated BSRs also indicates that they were caused by collapses of the uplifted sea floor. Thus we propose a simple conceptual genetic model for the occurrences of the submarine landslides, surrounding mud mounds and associated BSRs in the area. Seamount subduction created locally higher fluid overpressure in the décollement. The uplift and fracturing of the margin wedge above the subducting seamount opened pathways for the overpressured fluid to escape, leading to the formation of numerous mud mounds on the sea floor and the BSR in the subsurface. The higher fluid supply locally reduced the shear strength of the sediments and facilitated failure of these sediments as landslides on the oversteepened slope caused by the subduction of the seamount.