Whole-rock and clay mineralogy as paleoenvironmental tracers during the Late Holocene sedimentary evolution of the Doñana National Park (SW Spain)

Abstract

In recent decades, numerous studies have focused on the paleoenvironmental reconstruction of coastal areas, with special emphasis on the detection of tsunami layers. These multidisciplinary investigations usually do not study the mineralogy of the environment as well as the underlying or overlying layers.This paper analyzes the whole-rock mineralogy and clay minerals contained in seven short cores obtained in the Doñana National Park (SW Spain) and deposited during the 5.000–1.500 cal. yr BP interval.The main purpose is to deduce the paleoenvironments from which the sedimentary facies present in them were formed and an approximation to the transport mechanisms involved in their formation. Results of X-ray diffraction analysis indicate that the main minerals are phyllosilicates, quartz and calcite, with smectites and illite being the most abundant phyllosilicates. According to the whole-rock mineralogy and additional statistical procedures (correlation, cluster analysis), the main source of quartz is the erosion of Doñana spit, while the Guadalquivir river, its tributaries and the old lagoon have contributed mainly with smectite-rich phyllosilicates. On the contrary, waves, tides and high-energy events introduced illite and bioclasts in an old lagoon from the nearby shallow marine sectors. Consequently, the mineralogical analysis is revealed as an interesting tool for palaeoenvironmental reconstruction in this area, since it varies between different sedimentary environments. In addition, the combined study of whole-rock and clay mineralogy detects the tsunami layers and the provenance of their sediments in the studied cores.