GSA Annual Meeting in Indianapolis, Indiana, USA - 2018

Paper No. 275-1
Presentation Time: 1:30 PM


POWERS, Monica C.1, ANASTASIO, David J.1 and PARES, Josep M.2, (1)Earth & Environmental Sciences, Lehigh University, 1 West Packer Avenue, Bethlehem, PA 18015, (2)Geochronology Research Group, National Research Center on Human Evolution (CENIEH), Paseo Sierra de Atapuerca s/n, Burgos, 09002, Spain

New magneto- and cyclostratigrapy from rock magnetic data recovered from paleo-lakeshore strata in Southern Spain provides high-resolution chronology of hominin migration and occupation. Baza Basin archaeological sites, including Barranco León, have yielded lithic tools, animal bones, and a hominin tooth. Measured stratigraphic sections near the towns of Orce and Corte de Baza provide a basis for facies determination, environmental reconstructions, and new chronologies. Based on comparative sedimentology, we determined the environment of deposition of the Orce section to be an embayment of the paleo-lake consisting of paludal ponds and wetlands. Unoriented samples were collected every 0.25 meters for rock magnetic measurements, including low field magnetic susceptibility, Anhysteretic Remnant Magnetization (ARM), and Isotropic Remnant Magnetization (IRM). Oriented samples were collected every 3 meters for paleomagnetic investigation. IRM acquisition experiments confirmed the presence of fine grained magnetite in all the collected samples. We recovered Milankovitch frequencies encoded in the sections and calibrated our results with age constraints from our new magnetostratigraphy. Taken together, these data allow for higher resolution and greater confidence in correlation to GTPS. Precessional cyclicity was constrained from significant stratigraphic frequencies at 1.3-1.6m for both the ARM and susceptibility data series in the Barranco Conejos section (Orce), nearby and correlated with the Barranco León site. Based on the cyclostratigraphy, our favored sediment accumulation rates vary from 3.13 to 3.85 cm/kyrs, consistent with published paludal lake sedimentation rates. The favored magnetostratigraphy documents the presence of the normal Olduvai and Vrica subchron polarity zones within the longer, reversed Matuyama Chron. This Calabrian aged site is sub-Jaramillo (>1.08Ma) and above the Olduvai (<1.77Ma) in age. Using our favored sediment accumulation rate and the stratigraphic position above the Olduvai subchron, we calculate the age of Barranco León site to be 1.54±0.08 Myr, consistent with previous studies, which estimated the site age to be around 1.4 Ma based on micromammal biostratigraphy and magnetostratigraphy within the Barranco León section.