Spatial and Temporal Variation in the Nature of Pleistocene Pluvial Phase Environments Across North Africa

Abstract

Pleistocene-aged fluvial, lacustrine, and spring sediments across North Africa record times of enhanced rainfall relative to the present. Much, though not all of the preserved record, is found near modern oases or extant (sometimes seasonal) bodies of water. Pluvial phase indicators point to a variety of environmental conditions during humid events; reconstructed Pleistocene lakes range in size from several square kilometers to tens of thousands of square kilometers, and from long-lived perennial freshwater lakes, to large brackish lakes, to seasonal playas. Spring-fed wetlands would also have been a relatively common feature of pluvial phase environments. In most localities that record more than one pluvial phase, sedimentological and geochemical evidence suggests humid events following ~70 ka were less intense than those associated with Marine Isotope Stage (MIS) 5, though distributions of dates on these humid phases indicate they were still significant and continent-wide. Comparison of the timing of humid phases across the region is made possible through compilation of U-series, TL, and OSL dates on sediments indicative of relatively wet conditions. Available geochronological data suggest that the western Sahara and Mediterranean North Africa exhibit different climatic variation than the rest of the region, perhaps tied to the influence of Mediterranean rainfall.