Complex sedimentology and palaeohabitats of Holocene coastal deserts, their topographic controls, and analogues for the mid-Cretaceous of northern Iberia

Desert coasts in plate margins contain one of the most variable sedimentary records in terms of facies and stacking patterns. Reliefs in these basins together with massif palaeogeography and palaeotopography strongly control the spatial distribution of facies belts and complex lateral facies changes between very different coeval sub-environments, leading to mixtures of sedimentary particles with variable composition. Palaeotopography and palaeogeography also control the distribution of flora palaeohabitats in the desert basins depending on the spatial distribution of fresh water, the basin geometry, the topographic variability and associated phreatic level, as well as the effective distance from highlands to the coast. The Albian desert basin that developed in northern Iberia presents similarities with the geomorphology of modern Oman, UAE and Eritrea desert coasts. In both systems (Cretaceous and Holocene) the distance between highlands and arid coastline determines the occurrence of extensive aeolian sand seas (e.g. wide desert basin where distance between the highlands and the coastline increases) or the development of wadi-fed alluvial fans that reach directly the desert coast (e.g. narrow desert basin) leading to a variety of clastic and mixed carbonate facies. Due to prevailing arid conditions, vegetation is mainly restricted to highlands and water-conditioned lowland environments such as wadis, (tidal) coastal marshes and lagoons. Depending on sea influence and water availability, Cretaceous vegetation in Iberia were characterized by montane communities including arboreal/shrubby gymnosperms (mainly conifers) and lowland communities composed by a patchy mixture of ferns, Cupressaceae (cypress family), Cheirolepidiaceae and early angiosperms and/or costal woodlands incorporating Araucariaceae (monkey puzzle tree family). This distribution presents similarities with the ecosystems observed today in Eritrea mountains and other Holocene desert coasts.