Geology and chronology of the continental Pleistocene archeological and paleontological sites of the Orce area (Baza basin, Spain)

Abstract

The Guadix-Baza Basin hosts a continuous continental record of paleoenvironmental, paleobiological and geological changes from around 8 Ma to 205 ka. A remarkable succession of Pleistocene mammal sites is found in the Lower and Upper members of the Baza Formation in the Orce area. The Upper Member contains the Early Pleistocene paleontological and archeological sites of Barranco León-5 and Fuente Nueva 3. Both sites belong to the early Pleistocene zone defined by Allophaiomys aff. lavocati and a small Mimomys savini. This zone can be correlated with that of central Europe containing Mimomys savini and Microtus praehintoni. These sites are located in the marginal lacustrine deposits of the Baza lake system and originated in expanded phases of the main lake when meteoric surface and shallow groundwater inputs were predominant. The Barranco León-5 site is related to a sudden event of high-energy currents entering a lacustrine - palustrine domain. These currents transported gravels, bones and lithic industries from a short distance (maximum, hundreds of meters). In contrast, the diverse levels in Fuente Nueva 3 do not show evidence of noticeable transport by traction currents. The age of the mammal succession and sites is based on magnetostratigraphy. In the Middle and Upper members of the Baza Formation, only reversed polarities are found (Matuyama epoch). The location of the Olduvai chron is still unclear and could have not been recorded due to the common hiatuses observed in the sedimentary successions. In the Lower Member, normal and reverse polarities (Gauss epoch) are found in the Galera and Vélez-Salar sections. The later contains the site of Fuente Nueva 1, which is pre-Olduvai chron in age according to paleontological data and biostratigraphic correlation.