A Mass Balance Across The Rapidly Growing Mediterranean Ridge Accretionary Complex

Depth migration of seismic reflection profiles across the Mediterranean Ridge accretionary complex between the African and Eurasian blocks illustrate profound variations in the geometry and<br>internal structure along strike. Structural interpretations of four cross sections, together with bathymetric and acoustic surface information and drilling data, are used to volumetrically balance the amount of subduction versus accretion with time. Results infer the existence of three distinct scenarios, with a jump in décollement in the west, intense backthrusting in the central part between Libya and Crete, and transcurrent tectonism in the east. The onset of accretion coincides with exhumation of thrust sheets approximately 19 Ma before present. Thereafter, rapid sediment accretion is inferred for either scenario, with thick, evaporite-bearing incoming successions facilitating outward growth of the wedge. The minimum rate of accretion (20-25% of the total sediment supply) is observed where the ridge suffers maximum deformation. Here, the indenting leading edge of the African Plate apparently forces the sediment into subduction, or local underplating. In contrast, an estimated 40-60% of the available sedimentary input got accreted in the western domain where collision is less accentuated. The results support the hyp.othesis that highly destructive forearc collisional events, like the slab breakoff and exhumation of thrust sheets, are followed by periods of accretion and continuous growth of accretionary wedges.