Windblown desert sands in coeval shallow marine deposits: a key for the recognition of coastal ergs in the mid-Cretaceous Iberian Basin, Spain

Abstract

Grain size and SEM analyses suggest the presence of Cretaceous windblown desert sands in coeval shallow marine environments. Size distributions and microtexture data allowed us to infer a climate change to more arid conditions in the Iberian Basin during the mid-Cretaceous. The grain size of the sands in the late Aptian to early Cenomanian shallow-marine deposits in the western sub-basins of the Maestrazgo Basin (Teruel, Spain) is almost exclusively in the range between 1.5 and 3 Φ (0.35–0.125 mm), reflecting a prolonged or at least recurrent preselection of aeolian sands. The palaeolatitude of 25°N showed a change from a warm humid climate during the Lower Cretaceous to an arid desert climate in the eastern sector of Iberia during the late Aptian–early Cenomanian. Winds supplied abundant desert sand to the estuarine and deltaic sedimentary environments where it was worked up in sandy sub- and intertidal facies with a striking absence of mud in cross-bedded sets which otherwise clearly reflect the influence of a semi-diurnal tidal system.