Tectonic Trigger of Mass Movement Deposits in the Southern Alboran Basin

Abstract

The post-Messinian tectonic activity has an important role on the physiographic configuration of the Alboran Sea basin. The compressive regime between the Eurasian and Nubian plates has produced the progressive narrowing of this basin and the formation sub-basins and highs while the surrounding Betic-Rif Mountains uplift. The major submarine reliefs include the Alboran Ridge, a 1000 m high NE-SW structural and volcanic high with steep slopes facing northwards and southwards and the Cape Tres Forcas promontory in the Moroccan margin, which are the northern and southern borders of the South Alboran Basin respectively.

The bathymetric and high resolution study of South Alboran Basin highlights the presence of several mass movement deposits (MMDs) ranging from sliding to well-defined slope apron characterized by channelized and lobulated deposits coming from the basin margins and resting on the basin interior. Seismic stratigraphy study of this basin shows it has been filled partially since the Pliocene. These deposits show a major recurrence since the Late Pleistocene (0.92 M.y.), with a successive stack of at least five MMDs implying a recurrence interval o about 0.18 M.y. during this period. Many of them proceed from the Alboran Ridge, altough the largest one, the just discovered Montera Slide, comes from the Cape Tres Forcas promontory. This MMD is 50 ms average thick (maximum 180 ms), and covers an area around 90 km².

The successive deposition of MMDs since the Pliocene in the SAB would be triggered by the interplay between the tectonic activity of the Alboran Ridge and the promontory of Cape Tres Forcas. In this sense the major number of MMDs appoints to a reactivation of tectonics since the Late Pleistocene.