Geometry and lithofacies of sediment bodies in a tidally influenced alluvial area. Middle Eocene, Southern Pyrenees, Spain

Abstract

Four types of sedimentary macroforms are described from well exposed Eocene deposits in the Tremp-Graus Basin, Spain: channel deposits, depositional lobes, sheet deposits and composite forms of lobe and channel origin. The channel deposits comprise sediment bodies either formed by lateral accretion or by vertical aggradation. Mixed forms also occur. The form of the channel base is used for further subdivision of the channel bodies. The association of the sedimentary macroforms indicates deposition on distal parts of alluvial fans. Influence of tides is suggested by the bipolar cross-stratification, reactivation surfaces and mud drapes occurring in some of the channel deposits and depositional lobes. At some locations intensive burrowing suggests marine conditions.