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The Galería complex is located in the intermediate level of the Atapuerca multilevel karst in Burgos (Spain). The Galería complex is formed by three subsections filled with sediments and connected to each other: Covacha de los Zarpazos, Galería site, and Tres simas. These cavities are filled with extensively dated entrance facies, rich in fossil and archaeological materials, and on the other hand, with interior facies, barely dated and without fossil and archaeological remains. Studying in greater depth the interior facies deposits is of interest as they record the entrenchment of the regional fluvial system and a transition period between the formation of the intermediate and lower levels of the Atapuerca endokarst. Previous geological works suggest that these interior facies in the Galería-Tres Simas Complex should have been deposited during the Lower Pleistocene-Middle Pleistocene; however, geochronological studies have provided disparate ages by ESR and OSL on the top of the interior facies. Therefore, the objective of this study is to date the lowermost part of the interior facies to complete the chronological framework of the Galería complex and, to provide minimum dates for the formation of this keyhole cross section. With this objective, 5 and 22 samples were taken to be dated by ESR and Paleomagnetism, respectively. Our first results suggest Middle Pleistocene ESR ages that are in agreement with previous results obtained by OSL. In contrast, paleomagnetic data reveal reversal polarity. These results may suggest postsedimentary processes or geological events that underestimate the ages obtained by trapped charge dating techniques. Our results are important to better understand this interval of the fluvio-karstic system of the Sierra de Atapuerca, which preceded the opening of the Gran Dolina and Gallery cavities and their infill by entrance deposits. [ABSTRACT FROM AUTHOR]

The Cueva del Silo is part of the lower karst level of the Cueva Mayor-Cueva del Silo karst system (Sierra de Atapuerca, Burgos, Spain), whose evolution has preserved an impressive archeo-paleoanthropological sequence since the Early Pleistocene. Cueva del Silo is remarkable for the presence of fluvial deposits that record the entry of the Arlanzón River water in the cave system, providing a key sequence to investigate the fluvio-karstic relationships that give rise to this endokarst system. In order to provide a chronological framework to these fluvial deposits, six sediment samples were dated by Electron Spin Resonance and 16 samples by paleomagnetism, collected from two outcrops: Galería de las Arenas and Sala del Caos. Our results provide maximum mean age of around 1600 ka and a minimum age of 916 ± 136 ka for the deposits in Sala del Caos. The younger date from Sala del Caos might represent the last fluvial input from Arlanzón River in the lower karst level. In contrast, ESR ages estimates of 1268 ± 133 ka and 1262 ± 108 ka were obtained for Galería de las Arenas sequence, which could indicate re-sedimentation processes from the intermediate karst level where similar ages were published. The annual dose might be wrongly assessed due to the re-sedimentation processes inside the karst, hence, ESR ages for these facies should be treated with extreme caution. • We date allochthonous fluvial sediments preserved in Cueva del Silo in the Sierra de Atapuerca lower cave level. • For that, we applied ESR and paleomagnetism techniques to two Cueva del Silo sequences. • Results suggest the last fluvial inputs around 900 ka and possible re-sedimentation processes from the intermediate level. [ABSTRACT FROM AUTHOR]