Records of human occupation from Pleistocene river terrace and aeolian sediments in the Arneiro depression (Lower Tejo River, central eastern Portugal)

Abstract

In the uppermost reach of the Lower Tejo River (eastern central Portugal), where the river crosses two quartzite ridges that separate the Ródão (upstream) and Arneiro (downstream) depressions, Palaeolithic artefacts have been recovered from three lower river terrace levels and a cover unit of aeolian sands. This paper presents data on the discovery of archaeological artefacts from the terrace levels and the aeolian sands that can be linked to Middle and Upper Palaeolithic industries from new field sites at Tapada do Montinho and Castelejo. The archaeological data when placed in a geomorphological, sedimentary and chronological framework, contribute new information on the understanding of human occupation in western Iberia during coldclimate episodes of the last 62 to 12 ka; and especially during the cooler and driest conditions that occurred between 32 and 12 ka, when the climate favoured aeolian sediment transport. In the Lower Tejo River, the integration of absolute age datasets with archaeological, geomorphological and sedimentary data indicate that in westernmost Iberia the first appearance of artefacts in river terrace sediments suggests that the earliest marker for human occupation dates from the lower Acheulian (Lower Palaeolithic), probably corresponding to an age of~340 ka. Data also suggest, for the first time, that Acheulian lithic industries were replaced by Middle Palaeolithic ones (namely the Levallois stone knapping technique) by~160 ka (~MIS6). Middle Palaeolithic industries were later replaced by Upper Palaeolithic industries at 32 ka. The post 32 ka period, dominated by aeolian sediment transport, is related to the onset of cold-dry climate conditions which resulted in low river flow discharges, floodplain exposure and reworking by NW winds. This colddry period is coeval with the disappearance of Megafauna and associated Neanderthal communities, and the replacement of the Middle Palaeolithic industries by Upper Palaeolithic ones in this westernmost part of Europe.

New data on the chronology of the Vale do Forno sedimentary sequence (Lower Tejo River terrace staircase) and its relevance as a fluvial archive of the Middle Pleistocene in western Iberia

“…Correlations by Martins et al (2010b) and Cunha et al (2012), based mainly on geomorphologic criteria and new luminescence dating, indicated that the terrace containing the Lower Palaeolithic industries at Vale do Forno is equivalent to the T4 terrace of the upstream reach III (at Abrantes) and reach I (at R odão) of the Lower Tejo. In these reaches, finite infrared stimulated luminescence (IRSL, from K-feldspar) and optically stimulated luminescence (OSL, from quartz) ages were obtained for the T4, T5 and T6 terrace deposits (Cunha et al, 2008Martins et al, 2010aMartins et al, , 2010b: T4 e ca.…”

“…This resulted in a significant underestimation for the oldest samples (Cunha et al, 2008;Martins et al, 2009Martins et al, , 2010aMartins et al, , 2010b. Because of this age underestimation issue, Cunha et al (2012) proposed that the T4 aggradation should probably range in age from 340 ka to 160 ka. In the present study, these limitations in luminescence dating are largely overcome by a new protocol that uses the elevated-temperature post-IRIR stimulation (Thomsen et al, 2008;Buylaert et al, 2009) for measuring samples that have the quartz-OSL signal in saturation.…”

“…This uppermost sedimentary unit of the LTCB, and the upstream equivalent in Portugal, represented by the Falagueira Formation (Cunha, 1992(Cunha, , 1996, has been considered of latest Zanclean to Gelasian age (3.65e1.8 Ma; Cunha et al, 2012Cunha et al, , 2016Pais et al, 2012;Diniz et al, 2016). Previous studies (e.g.…”

Geocronología de los yacimientos achelenses de Pinedo y Cien Fanegas (Valle del Tajo) e implicaciones en la evolución fluvial en el entorno de Toledo (España)

“…Este hecho también se ha constatado para los valles de los grandes ríos de la fachada atlán-tica del suroeste de Europa (Bridgland et al, 2006) y en concreto para el caso de la Península Ibérica (Santonja & Pérez-González, 1997y 2010Oosterbeek et al, 2010;Cunha et al, 2012). Estos autores indican que las condiciones medioambientales benignas del MIS 11, período cálido interglaciar que comenzó aproximadamente hace 420 ka (Imbrie et al, 1992), favorecieron el incremento de poblaciones con industria achelense en el suroeste de Europa, siendo antes su presencia poco significativa.…”

“…En el curso bajo del río Tajo (Portugal), las dataciones OSL disponibles (Cunha et al, 2008(Cunha et al, , 2012Martins et al, 2009Martins et al, , 2010 indican que las terrazas de c. +30−48 m, con edades de c. 260-340 ka, poseen industrias achelenses (Monte do Famaco), mientras que la terraza inmediatamente inferior (+16−28 m) posee industrias claramente musterienses con fechas comprendidas entre 135 ka (base) y 73 ka (techo), dentro del tránsito Pleistoceno Medio-Superior (MIS 6 -MIS 5). Estas cronologías más recientes son también características de las unidades superiores de las terrazas complejas a +18-20 m en los valles del Jarama y Manzanares (Panera et al, 2011;Pérez-González et al, 2013;Silva et al, 2013).…”