Reconstructing depositional environments through cave interior facies: The case of Galería Complex (Sierra de Atapuerca, Spain)

This work showed that cave sediments are useful for geomorphologic studies and for reconstructing depositional environments. While the cave entrance facies have been extensively studied for their relationship with the fossil and archaeological record, the cave interior facies have received much less attention, although they can provide much information on the geomorphological evolution of the karst. This work presents the stratigraphic and sedimentological study of a section >6 m thick and 10 m long of cave interior sediments of Galeria Complex (Sierra de Atapuerca, Spain). Galeria Complex is a cavity infill of the Sierra de Atapuerca (Spain), composed of three sections filled by at least 30 m of Pleistocene sediments. This sequence is divided into 5 lithostratigraphic units named from bottom to top: GI - GV. GI unit is 19 m thick of interior facies in the base of the Galeria Complex, divided into two sub-unit, GIa and GIb, by the Matuyama-Bruhnes paleomagnetic boundary. GI unit shows an issue with the chronology since has uncoherent between TT-OSL and ESR/U-series and paleomagnetism dates. This work has been done by combining field observation with laboratory sedimentary analysis to characterize the texture and structure of the sediments. Based on these studies, 12 layers and 9 sedimentary facies have been identified. The facies associations indicate a clear separation between GIa and GIb sub-units. GIa subunit is dominated by epiphreatic conditions and represents continuous relativity sedimentation during the Early Pleistocene; meanwhile, GIb shows important erosion events and facies with reworked materials that indicate vadose conditions during the Middle Pleistocene. This environmental change is related to the geomorphological evolution of the Arlanz ' on River. In addition, soft-sediment deformation structures have been described, including faults and low-angle folds. An important leaching process has been identified by the presence of phosphates that could explain the underestimated ages obtained in other works.

Automated summary

This study demonstrates the usefulness of cave sediments for geomorphologic studies and reconstructing depositional environments. By conducting stratigraphic and sedimentological analysis on the cave interior sediments of Galeria Complex in Spain, the researchers were able to identify 12 layers and 9 sedimentary facies and observed distinct differences between the GIa and GIb sub-units. This study provides important insights into the geomorphological evolution of the area during the Pleistocene.