The silence of the layers: Archaeological site visibility in the Pleistocene-Holocene transition at the Ebro Basin

Abstract

The Ebro Basin constitutes one of the most representative territories in SW Europe for the study of prehistoric societies during the Pleistocene-Holocene transition. The correlation of palaeoenvironmental and geomorphological proxies obtained from sedimentary records with chronologically well-constrained reference archaeological sites has allowed defining this time frame precisely, such that three main pilot areas haven been broadly depicted: the Alavese region, the Pre-Pyrenees and the Bajo Aragón. Overall, the human imprint in the Ebro Basin was rare during the Upper Palaeolithic, but more visible from the Upper Magdalenian (14500 to 13500 cal BP) to Neolithic times (up to 5500 cal BP). Local environmental resources were continuously managed by the prehistoric communities in the different areas of study. In fact, the Ebro Basin acted during those millennia as a whole, developing the same cultural trends, industrial techniques and settlement patterns in parallel throughout the territory. However, some gaps exist in the 14 C frequency curve (SCDPD curve). This is partially related to prehistoric sites in particular lithologies and geological structures that could have partly been lost by erosional processes, especially during the Early Holocene. In addition, this gap also parallels the reconstructed climate trend for the Pre-Pyrenean and the Bajo Aragón areas, which are defined by high frequencies of xerophilous flora until ca. 9500 cal BP, suggesting that continental climate features could have hampered the presence of well-established human communities in inland regions. The interdisciplinary research (archaeology, geomorphology and palaeoclimatology) discussed in this paper offers clues to understand the existence of fills and gaps in the archaeological record of the Ebro Basin, and can be applied in other territories with similar geographic and climate patterns.

Call it home: Mesolithic dwellings in the Ebro Basin (NE Spain)

“…Some appealing examples are the caves of Abauntz (Utrilla et al, 2015) and Chaves (Baldellou, 2011), where intense Upper Magdalenian occupations are followed by a prolonged occupational gap until Neolithic times when the human presence was heavily resumed. This is possibly the only Mesolithic occupational preference we can firmly establish (Alday et al, 2017). The reason remains unknown, although sometimes it has been noted that between the Magdalenian and the Neolithic, some caves in the Ebro Basin (like Chaves, Utrilla, 1992) suffered floods and karstic reactivations that could have made them inhabitable.…”

“…However, as far as we know, the Mesolithic hunter-gatherers frequently looked for a certain natural roofed protection. We must be aware that the findings of prehistoric dwellings are seriously conditioned by the series of factors previously quoted (Peña-Monné et al, 2005) and that our current knowledge is partial and heavily biased in favour of rockshelter-protected sites (Alday et al, 2017). Rodanés and Picazo (2013) annotate a series of open-air isolate findings in the lowlands of the Ebro Basin that can be dated to the Mesolithic times, although they lack accurate dates.…”

“…8800-7600 cal BP). Dates offered to frame those industries must be seen as approximate: those cultural horizons do not appear synchronically along the Basin (Alday et al, 2017); table 1 details the radiocarbon dates (only those with a standard deviation < 100) available for the studied ensemble. The Mesolithic period is the first moment when a dense network of sites can be documented throughout the basin despite the thus-far empty territories, in which linking the well-established local and regional grids has been difficult for us.…”

La cronología de la Prehistoria de la Península Ibérica y los Sistemas de Información Geográfica del registro arqueológico

“…Deberíamos preguntarnos si para el conjunto peninsular y/o regionalmente los escenarios radiocronológicos reflejan la realidad prehistórica. No parece: p o r e j e m p l o , e n l a C u e n c a d e l E b r o l o s yacimientos/fechas se concentran en determinados polos con amplias comarcas sin datos debido a problemas de visibilidad arqueológica y caracteres geomorfológicos (Alday et al, 2018).…”

“…c). La reiteración de dataciones Algunos proyectos de investigación permiten la datación reiterativa de un contexto arqueológico: es una suerte contar con múltiples valores de un conjunto, pero a la hora de compilarlos cara a un estudio sobre la evolución del poblamiento, o para caracterizar un momento cultural, puede resultar un problema (Attenbrow y Hiscock, 2015;Crombré y Robinson, 2014;Alday et al 2018). d) Últimas reflexiones Otras reflexiones a la hora de compilar dataciones radiométricas:…”