Spatial variability of multi-controlled aeolian supersurfaces in central-erg and marine-erg-margin systems

Abstract

During the Albian Iberia was under the influence of the Northern-Hemisphere Hot Arid Belt favouring the development of an extensive sandy desert system with a marine-erg margin where prograding aeolian dunes interacted with Tethyan waters. The interplay of different controls, such as synsedimentary tectonics, compaction of the underlying coal-bearing unit, eustatic sea-level variations, climate modulation, and the autodynamics of the different sedimentary subenvironments determined the character of bounding surfaces, which separate four erg sequences. These bounding surfaces, or supersurfaces, may display a different sedimentary expression in adjacent areas. Bounding surface 1 is a sand-drift surface (SDS) in the central-erg and a transgressive surface (TS) in the marine erg margin. Bounding surface 2 is associated with a basin re-configuration associated to active extension tectonics, followed by deflation. Bounding surface 3 marks the end of erg expansion, the start of its partial destruction and redeposition and reworking in restricted marine environments. Bounding surface 4 marks the return to more arid conditions and draa progradation into Tethyan waters. These bounding surfaces separate four erg sequences. On the basis of the relative role of allocyclic processes, two megasequences are defined. The first comprises erg sequences 1–3, and the second megasequence comprises erg sequence 4. Erg megasequence 1 developed while synsedimentary tectonic activity and substrate (peat) compaction were active. Erg megasequence 2 was mainly modulated by climate (change). A nomenclature for supersurfaces is proposed based on the types of external control.