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Geometry and Chronology of the Late Pleistocene Distal Almeria Fan (SW Mediterranean Sea)

Belen Alonso, Gemma Ercilla, Carmen Juan, Ferran Estrada, David Casas, Margarita Garcia, Juan-Tomas Vazquez, Elia D'Acremont, and Christian Gorini

Multibeam bathymetry and high and ultrahigh resolution seismic reflection profiles have been used to define the chronostratigraphy and geometry of the Almeria distal fan located in the Eastern Alboran Sea (W Mediterranean Sea). The Late Quaternary deposits are defined by two seismic units, from oldest to youngest U1 and U2, bounded by discontinuities related to the Quaternary isotopic stages MIS 22 and MIS 12 respectively. The thickness distribution of these units reveals two depocentres resulting in up to 200 ms of sediment in U1 and 136 ms in U2. The architecture of these units displays a total of six fan lobes (1 to 6). These fan lobes extend from the base of slope (1200-1500 m water depth) into the Eastern Alboran Basin (> 1800 m).

Based on the geometric parameters (thickness, width, length, surface area, shape) and sedimentary architecture, the Pleistocene sedimentary evolution can be explained by two phases: Phase 1 (0.900-0.440 kyr) is aggrading type during which confinement of three fan lobes (1-3) occurred. They are morphologically elongated with similar geometric dimensions; Phase 2 (0.440 kyr-present) is retrograding type during which three fan lobes (4-6) with lobe/elongate forms and decreased geometric dimensions were created. The formation and evolution of the fan lobes, developed during these two sedimentary stages of the Late Pleistocene, was mainly controlled by 3rd order cycles of sea level changes, fluctuations in the volume of sediment supply, avulsion processes and the pre-existing palaeotopography.

AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013