Sediment movements in Lebanese submarine canyons

Abstract

        Three of the seven submarine canyons discovered during recent surveys on the continental shelf of Lebanon have been investigated in detail. Dredge and core samples were collected in Jounie Bay, St. George’s Bay and Beirut submarine canyons and analyzed for organic content, stratification and gram size. Core and dredge samples from Jounie Bay and St. George’s Bay showed evidence of anaerobic conditions in sea floor sediments. These conditions exist to a sediment depth of 45 cm as shown by analysis of cores taken along the axes of the submarine canyons. Organic matter, land plants and shallow-water organisms occurred to depths of at least 450 m. Some cores showed irregular inclined contacts between fine grained sediments and overlying coarse graine layers; other cores showed alternating sand, silt and clay. These features are evidence of sediment movement downslope along canyon axes. This movement is probably seasonal reaching a maximum during the winter months when heavy swells due to offshore storms in the Eastern Mediterranean create conditions of strong surf and consequent agitation of nearshore sediments in the bays surrounding the heads of the submarine canyons.