Deciphering site formation processes through soil micromorphology at Contrebandiers Cave, Morocco.

ABSTRACT

Contrebandiers Cave preserves a Late Pleistocene sequence containing Middle Stone Age (MSA) so-called Maghrebian Mousterian and Aterian occupations, spanning from ∼126 to 95 ka (thousands of years ago), followed by spatially restricted Iberomaurusian industries. Micromorphological analyses, complemented by instrumental mineralogical identification and fabric orientation, allowed for the reconstruction of the main site formation processes at the site. Initial deposition is characterized by local reworking of marine shelly sands dating to Marine Isotopic Stage 5e (MIS5e). The subsequent stratification reveals sedimentary dynamics predominantly associated with gravity-driven inputs and contributions from weathering of the encasing bedrock, at the same time that anthropogenic sediments were being accumulated. The allochthonous components reflect soil degradation and vegetation changes around the cave during the last interglacial. Human occupations seems to be somewhat ephemeral in nature, with some stratigraphic units apparently lacking archaeological components, while in others the human-associated deposits (e.g., burned bones, charcoal, and ashes) can be substantial. Ephemeral breaks in sedimentation and/or erosion followed by stabilization are mainly discernible microscopically by the presence of phosphatic-rich laminae interpreted as short-lived surfaces, peaks of increased humidity and colonization by plants. More substantial erosion affects the uppermost Aterian layers, presumably due to localized reconfigurations of the cave's roof. The subsequent Iberomaurusian deposits are not in their primary position and are associated with well-sorted silts of aeolian origin. While the effects of chemical diagenesis are limited throughout the whole stratigraphic sequence, physical bioturbation (e.g., by wasps, rodents, and earthworms) is more pervasive and leads to localized movement of the original sedimentary particles.