High-resolution multi-technique analysis of a continuous sediment core of the Baza Formation at Barranco León (Guadix-Baza Basin, Granada): First petrophysical results

Abstract

We report the first continuous core-based sedimentary record obtained at Barranco León, Spain, based on two boreholes drilled on the western and eastern margins of the ravine. The sediment cores cover an 80 m-thick succession belonging to the Baza Formation, which includes the lithic artefact- and fossil-bearing deposits documenting one of the earliest evidence of hominin presence in western Europe. Based on a series of observations performed at macroscopic (core description) and microscopic (grain size, fabric, thin sections) scales combined with the results obtained from the high-resolution multi-technique analysis of the natural radioactivity, magnetic susceptibility and carbonate content along the sediment cores, we identified six main lithostratigraphic units (named LU1 to LU6 from top to bottom) showing distinct compositions, textures and petrophysical properties. While our results are overall consistent with those from previous works based on outcropping sediment, we nevertheless provide here an unprecedented, detailed and continuous characterization of the 80-m thick sedimentary sequence at Barranco León. In particular, this is the first time that the deposits located > 15 m below the archaeological level can be accessed and thoroughly described in this area. Consequently, the present work offers a robust lithostratigraphic framework for future chronological and paleoenvironmental studies. From a methodological point of view, we observe a good consistency between the various data sets collected, independently of whether they were obtained from in situ or laboratory analyses, or using non-invasive or more destructive approaches. In particular, the magnetic susceptibility records obtained from the direct measurement of the core with a multi-sensor core logger, and from discrete samples collected from that same core, are in excellent agreement.