APPLICATION OF ROCK MAGNETIC BASED CYCLOSTRATIGRAPHY TO THE BAZA LAKE, SPAIN AND IMPLICATIONS FOR PLEISTOCENE HUMAN OCCUPATION OF THE IBERIAN PENINSULA

Recovery of Milankovitch cyclicity in Quaternary lake sediments, calibrated with a refined magnetostratigraphy, allows sediment accumulation rate and stratigraphy to be determined with improved fidelity. Lakeshore sedimentary strata in the Baza paleo-lake contain evidence of lithic tools, hominin fossils, and human occupation in several locations. Detailed stratigraphic sections near the towns of Orce and Cortes de Baza anchor the magnetic measurements and form the basis of comparative facies determination. Two sections, both ~60m in depth were sampled, every 3m for paleomagnetic measurements and every 0.25cm for rock magnetic measurements, near the eastern and western shorelines of the large lake watershed. Isothermal Remanant Magnetization acquisition curves confirmed the presence of fine-grained magnetite in all of the samples. Anhysteretic Remanant Magnetization (ARM) and magnetic susceptibility data series were analyzed using the multi-tapered method of a time-frequency analysis used to isolate orbital rhythms after calibrating the sections to the new magnetostratigraphies and tuning to the Precessional bandwidths. Frequency peaks between 1.0 and 1.5m at the Barranco Conejos section, near Orce, correlate to a sediment accumulation rate of 3.5cm/kyr, using a Precession parameter lineage test with Analyeries. Preliminary paleomagnetic results have identified the Matuyama C2 Chron with reversed and normal intervals that are likely pre-Jaramillo (>1.07Ma) and post basal Olduvai in age (<1.95Ma), consistent with previous paleomagnetic and biostratigraphic results. Hominin activity in the southern Iberian Peninsula during the Early-Mid Pleistocene sheds new light on biped migration corridors out of east Africa and northward through Europe.