Joint vegetation and mammalian records at the early Pleistocene sequence of Bòvila Ordis (Banyoles-Besalú Basin, NE Spain) and their bearing on early hominin occupation in Europe

Abstract

The early Pleistocene site at Bovila Ordis (Banyoles-Besalu Basin in NE Iberia) delivered in the past a significant pollen succession which can be assigned to the upper Matuyama geomagnetic chron owing to the identification of the Cobb Mountain magnetic subchron (1.2 Ma ago). It has been previously shown by palynology that the succession of lakes recorded at Bovila Ordis corresponds to a succession of late early Pleistocene glacial–interglacial phases, between 1.2 and 1 Ma, which can be correlated with MIS 35, 33 and 31. The present investigation focuses on lake 1 (borehole BOIV) and lake 3 (boreholes BOI, BOII and BOIII and outcrops) from this site, where both fossil pollen and rodent teeth were recovered together in the same sediment, and offers the potential to provide a vegetation and climatic context to sites that are dated by rodent teeth, such as some hominin sites in Western Europe. Here we analyse the rodent content and their biostratigraphical implications in the context of early hominin dispersal in Western Europe. In lake 1, pollen data had revealed in previous analysis a complete glacial–interglacial cycle and parts of a second one. The uppermost part of BOIV sequence yielded rodent remains that can be assigned to the arvicolid species Allophaiomys chalinei and Mimomys cf. savini. Previous palynological investigations from lake 3 had revealed a temperate deciduous forest, indicative of warm and humid conditions. At the top of the section of lake 3, a regression of the forest and the spread of open landscape elements indicated drier, more steppic conditions. The palaeobiological record of lake 3 includes pollen and large (Cervus philisi, Hippopotamus antiquus and Equus stenonis) and small mammal remains (Mimomys savini and Allophaiomys lavocati). The rodent material from lake 1 clearly indicates an early Pleistocene age somewhat older than that of lake 3. According to these new biostratigraphic data in the context of previous palynological and chronological data, it is clear that Allophaiomys chalinei entered Iberia before 1 Ma ago and A. lavocati remained until 1 Ma ago. The fact that Allophaiomys lavocati and Allophaiomys chalinei, two arvicolids currently associated with the earliest evidence of hominin presence in Western Europe, appear in Bovila Ordis at a time of mild, temperate conditions reinforce the idea that the first hominin dispersal in this region was strongly dependent on favourable climatic conditions.