Late Pleistocene Sedimentary Environment of the "Homeb Silts" Deposits, along the Middle Kuiseb River in the Namib Desert, Namibia

Abstract

In the Namib, the tectonic and geographic setting of the area means that there are no large lake basins, and relict aeolian deposits appear to be quite rare. This has posed severe problems for reconstructing palaeoclimates in this region. In addition, there are significant problems with developing a well-dated chronology of events, as well as in the interpretation of the dated evidence for hydrologic and climatic changes. The Late Pleistocene "Homeb Silts" have been interpreted in previous studies as follows: (1) dunedamed lake sediments indicating an arid environment; (2) river end-point deposits indicating arid conditions; (3) flood plain sediments of an aggrading river indicating a semi-arid environment and (4) river flood slack water sediments indicating a wet environment and intense precipitation events in the headwaters. In this present study, sedimentary facies of the "Homeb Silts" were re-described and interpretation of the sedimentary environment changes that resulted in their deposition re-assessed. The conclusions are as follows: (1) The "Homeb Silts" were deposited during ca. 26 to 19 k yrs BP (ca. 25 to 19 k cal yrs BP) as indicated by eleven AMS 14C measurements; (2) Almost all of the "Homeb Silts" were deposited under wet conditions by fluvial floods, except during the early depositional phase; (3) The "Homeb Silts" have recorded some detailed environmental changes during ca. 26 to 19 k yrs BP (ca. 25 to 19 k cal yrs BP); and, (4) Depositional events caused by similar climatic events in recent years have occurred, like heavy rains and flood events in the headwaters.