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The Galería karstic complex, situated within the Atapuerca Multilevel Karst system (Burgos, Spain), records an impressive sedimentary sequence from the Early to Middle Pleistocene period. One of the notable features of this complex is the presence of thick fluvial deposits (waterlain facies), providing a detailed record of the transitional moment between the formation of the middle and lower Atapuerca karst levels. Examining these sediments, barely dated thus far, is crucial for gaining a comprehensive understanding of fluvio-karstic dynamics at the Atapuerca site. In our study, we conducted dating analyses on sediment samples from different areas of the Galería complex using Electron Spin Resonance (ESR) on quartz grains (4 samples from Covacha de los Zarpazos and 1 from Tres Simas Norte outcrops) and paleomagnetism (12 samples). The aim was to refine the chronological framework of the Galería complex, providing ages for the formation of these passages. Considering the geological context, our results revealed underestimated Aluminium (Al) ESR ages ranging from 372 ± 78 to 569 ± 80 ka in Covacha de los Zarpazos, along with consistent dates of 1184 ± 120 and 1001 ± 302 ka in Covacha de los Zarpazos and Tres Simas Central, respectively. Our results agree with previous estimates obtained through luminescence dating methods, indicating Middle Pleistocene ages for the samples. In contrast, reverse polarity estimates disagree with those from radiometric dating methods, except for samples ZAR1501 and TSC1501. Caution should be taken when interpreting these ages, as various geological factors including leaching processes from upper zones, post-sedimentary structures, and lithological variations may indicate alterations in the primitive geochemical composition of the sediment. Consequently, these factors can potentially affect the total Dose rate parameter and introduce uncertainties into the age calculations. • We aimed to date interior fluvial sediments preserved in Galería Complex (Atapuerca). • For this purpose, ESR and Paleomagnetism samples were taken in Covacha de los Zarpazos and Tres simas central. • The results showed two distinct data sets: Ages of approximately 1 Ma ago were associated with Arlanzón T3 and T4 terraces. • Anomalous ages may be caused by a potential overestimation of the annual dose, resulting from diagenetic processes. [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]