Human colonisation and vegetation response to Late Pleistocene to mid-Holocene climate variability in Northern Iberia based on a multiproxy analysis of the Atxurra cave-fill

Abstract

Atxurra Cave (Berriatua, Northern Spain) contains an important Magdalenian archaeological assemblage comprising evidence of ephemeral occupation in the lower cave level and a unique assemblage of rock art. With the aim of understanding the palaeoenvironmental conditions and the nature of the human occupation, detailed micromorphological, mineralogical, palynological and anthracological analyses were undertaken near the entrance of the cave. The lower part of the excavated sequence comprises almost unfossiliferous silty units deposited over a thick speleothem deposit, which alternates with a sandy-silt matrix-supported microfacies dated about 33.4 kyr B.P. Palynological assemblage in this unit suggest regional vegetation was formed by montane pines, junipers and broadleaved elements like birch and hazel. Overlying units of brown clayey material, dated to ca. 19.7–18.4 kyr B.P., contain evidence of a Gravettian occupation with Noailles burins, and a palynoflora indicative of localized conifers with a dense herbaceous steppe understory, in an arid and cold climate. At ca. 15.5–14.5 kyr B.P. there is a return to meso-thermophilous tree and shrub taxa within a warmer and humid climate background, which may have favored the regional development of the Magdalenian culture. The uppermost unit, dated ca. 7.7–7 kyr B.P., reveals postglacial expansion of a mixed Atlantic forest with no signals of anthropization before the start of the Neolithic.