The Pleistocene And Holocene Records Of The Mazarron Basin (Se Spain)

Here we reconstructed the evolution of the Mazarron Basin during the Pleistocene and Holocene. In this regard, we studied 9 cores with the aim to: 1) define a chronological framework; 2) obtain data on the palaeoenvironment; and 3) establish the relationship with recent tectonics. A total of 158 samples were recovered for amino acid racemization (AAR) dating, 4 for radiocarbon dating (C-14), and 332 for sedimentological and palaeontological determination, and 110 for determination of the mineralogical content. These approaches allowed us to elucidate the evolutionary phases of the palaeo-landscape of the Mazarron Basin, a fault-controlled graben affected by diverse faults, mainly those of Las Moreras and Rella. The ages of the records and the facies correlation indicate that Las Moreras Fault controlled sedimentation during Marine Isotope Stage (MIS) 7, whereas the Rella Fault was strongly active during the Middle Holocene. During MIS7, a brackish lagoon developed in the western area, overlying alluvial fan deposits. Later, the area was uplifted, thereby becoming exposed to erosion. The activity of the Rella Fault allowed sedimentation in the western part of the Mazarron Basin during the Middle Holocene, while in the Upper Holocene sedimentation occurred in the eastern part. The Holocene transgression was reflected in a temporarily floodable marsh in the hinterland, with changing salinity conditions, from brackish to euhaline waters. Along the sea front, the marine influence was evident but not dominant. Thus, the Mazarron Basin during the Holocene was brackish to highly euhaline, with variable biological diversity linked to a narrow and probably discontinuous communication with the sea, with restricted circulation and long flushing times, which was reflected by the significant presence of halite. The record ended with recent alluvial/anthropic sediments.