Continental sedimentation in an evolving rift basin: the Lower Cretaceous of the western Cameros Basin (northern Spain)

Abstract

The Lower Cretaceous of the western Cameros Basin comprises up to 2.5 km of clastic and carbonate continental sediments deposited in a variety of fluvial and lacustrine settings. ?Kimmeridgian-Berriasian red beds and lacustrine limestones are overlain by the Valanginian-?Aptian Pedroso Group, which is dominated by sheet flood sandstones and distal alluvial mudstones with vertebrate footprints, mudcracks and intercalated carbonate paleosols. Lacustrine limestones are also present, commonly containing spongiostromate oncoids. The upper part of the sequence, the Salas Group and Utrillas Formation (Aptian-Lower Cenomanian), comprises quartzose pebbly sands and conglomerates with rare muddy paleosols. These sediments are interpreted as braided stream deposits. Deposition of this thick continental sequence may be correlated with the extensional history of the Cameros Basin and of the evolving Bay of Biscay rift to the north. Clastic supply was dominantly controlled by tectonic factors; facies evolution may also have reflected climatic influence.