ABSTRACT

?Serravalian-Tortonian sediments of the Sorbas Basin, Southeast Spain, preserve an oblique slice through a narrow east-west-trending turbidite basin. Close to Lucainena, unusual "composite" sandstone sheets with thick mudstone caps can be traced obliquely away from the faulted southern margin of the trough in the vicinity of where north-to-south transverse paleoflows are replaced eastward by west-to-east axial flows. Three distinctive types of bed profile are recognized. Lateral correlations over distances up to 5 km establish that Types I, II, and III bed profiles are laterally equivalent and must have been emplaced together as part of the same event. Beds with Types I and II profiles are present to the WSW, where they thin and pinch out toward the contact with the Alhamilla basement to the south. As beds are followed along strike to the ENE, they thicken and develop Type III profiles before thinning again and passing laterally into bioturbated marls. The structure and lateral relationships are thought to have been produced by deposition from turbidity currents derived from the north and northwest but deflected against a raised Alhamilla block and forced to flow eastward. The composite structure of the beds close to the Alhamilla basement is related to deceleration and subsequent collapse of flows that partly rode up the southern flank of the basin as they were turned to travel eastward down the basin axis. The thick mudstone caps represent fallout from a suspension cloud produced by axial ponding of the muddy tail of the deflected currents (suggesting that the basin was closed to the east); internal seiches set up by ponding of the flows may account for some of the features of Type II profiles.