Texture and mineralogy as proxies of late Holocene tsunami deposits from the Doñana National Park (SW Spain)

Abstract

The multidisciplinary analysis (dating, texture, total mineralogy) of two deep cores collected in the Donana National Park (SW Spain) allows to distinguish the main features of three tsunami deposits found in three different paleoenvironmental scenarios (TSU-1: inner area of an open lagoon; TSU-2: inner area of a restricted lagoon; TSU- 3: outer area of a restricted lagoon). The main textural feature of the inner lagoonal tsunami deposits is the increase in bioclastic sands, while the outer TSU-3 is composed almost entirely of medium and fine sands without bioclasts. The mineralogical analysis of TSU-1 and TSU-2 reveals a decrease in phyllosilicates in the basal layers of these tsunami deposits and a parallel increase of quartz, feldspars, dolomite and sometimes calcite. Silica is the main component of TSU-3, whose mineralogical composition changes progressively due to the action of tidal currents in the inlet lagoon on which it is deposited. This rich- SiO2 outer tsunami deposit is derived from the erosion of the adjacent aeolian systems, while the inner TSU-1 and TSU-2 were generated by the transport of bioclastic sands from the outermost parts through the lagoon (TSU-1), or through a nearby tidal channel (TSU-2).