A new conceptual model for the deposition process of homogenite: Application to a cretaceous megaturbidite of the western Pyrenees (Basque region, SW France)

摘要: Abstract The north Pyrenean megaturbidite is a 19–63 m exceptional thick bed deposited during the Late Turonian and extending over more than 90 km in Basque region Country (SW France). Its thickness varies from 63 m to about 19 m east (Mauleon area) west (Basque coast). It represents total compacted volume of 90 km3 carbonates. On field, rare sedimentary structures are visible turbidite bed. They consist laminar planar lamination cross laminations eastern antidune-like western region. Five sites have been sampled with vertical step 50 cm 1 m. Thin sections quantitatively analyzed for counting terrigeneous fraction, quartz grain size mineral orientation. deposits fine westward, which suggests source located Mauleon Basin. This consistent orientation lower part megaturbidite. upward medium sand clayey-silt. classical definition homogenites that these kinds turbidites. These observations also suggest term “megaturbidite” appropriated deposits. analysis indicates deposit results single event. sediment involved process, as well indicating flow motion opposite direction initial structure formation reflected flows standing waves complete water column flysch sub-basins corresponding “Seiche effect”. origin probably an earthquake-generated collapse on carbonate platform. example allows providing new conceptual model process homogenite deposition. explains deposition thick, fine-grained, crudely-graded megaturbidites.