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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 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]

Pleistocene fluvial incision acceleration resulting in narrow and deeply entrenched valleys has been widely described and is generally attributed to uplift rate increase or greater climatic severity. In this paper, the long-term downcutting pattern of the Upper Ebro River and driving mechanisms are assessed, and we reconstruct the valley incision recorded by an outstanding sequence of 22 river terraces. Dating of 8 fluvial levels by means of the ESR, TCN, and OSL techniques, spanning the last 1.2 Ma, reveals a long-term incision deceleration pattern. The estimated age-incision model indicates a decrease in the incision rates, showing a long-term deceleration during the final Early Pleistocene (from 0.42 to 0.18 m/ka), and a tendency towards a steady state or base level stabilization from the Middle Pleistocene (0.15–0.03 m/ka) to the Late Pleistocene (0.03 m/ka). This incision pattern does not support climate change as a long-term incision-acceleration driver by itself, demonstrating the need for base level lowering effects to have operated. Upper Ebro deceleration incision is explained by the headward attenuation of the incision wave induced by the opening of the Ebro Cenozoic Basin in a geodynamic context characterized by an absence of significant uplift over the last million years. This trend could have changed the aggressor-victim roles of the rivers involved in fluvial captures at the drainage divide. The documented incision deceleration pattern differs from that reported for other valleys in the Iberian Peninsula, suggesting that the degree of maturity of the fluvial systems depends on their relative position with respect to the capture point, in addition to tectonic and lithostructural factors. In the Late Pleistocene-Holocene, a short-lived incision rate increase is recorded, corresponding to the last terrace dissection phase, during the transition from the last glacial MIS 2 to the interglacial MIS 1. • Incision acceleration is widely reported during Pleistocene valley entrenchment. • However, the Upper Ebro valley contains a complex sequence of fluvial terraces • which were dated within the last 1.2 Ma using ESR, TCN and OSL techniques • and indicate an incision deceleration pattern. • This suggests that the river incision is tending to a steady state. [ABSTRACT FROM AUTHOR]