Impact of Holocene marine transgression and climatic changes on the Moros marsh (western Mediterranean, Spain)

Coastal wetlands are the most common environments in the Spanish Mediterranean. They provide valuable information about past interactions between sea level fluctuations, climate variability and sediment dynamics, which could enable us to predict the future response of coastal systems to global climate change. This study analyses the palaeoenvironmental evolution of the Moros Marsh (Western Mediterranean) during the Holocene, with the aim of assessing the impact of the MIS 1 marine transgression and climate change on the configuration of the wetland during this period. To achieve this goal, 347 samples extracted from four boreholes were studied from a sedimentological, micropalaeontological and chronological perspective. The results show a thick alluvial unit at the base of all the boreholes, dated as Middle Holocene, on which brackish marsh facies developed, which later became freshwater. A barrier facies has been detected in the most coastal borehole (Moro 2), with a maximum Holocene transgression (MIS 1) dated around 5200 cal yr BP. The first flooding evidence appears in the innermost borehole (Moro 1) around 3562-3440 cal yr BP and continues to the present day, with episodes of oscillation in the water table related to climatic changes in the Northern Hemisphere. A low-salinity, low-energy environment is determined, with little marine influence and a powerful supply of fresh water from the aquifer. This environment is the result of the interaction between eustatic and climatic factors. The former account for the formation of the lagoon system, and the latter are the main controllers of its subsequent evolution.