Mapping Saharan Dust Fluxes through the Onset and Termination of the African Humid Period in a Transect of African Margin Cores

DESCRIPTION: The project will examine past climatic changes in the Sahel over the past 15ka through changes in dust fluxes and sedimentation rates in the meridional transect along the northwest African margin. During the African Humid Period between 11 and 5 thousand years ago, central North Africa supported large lakes, abundant megafauna and numerous human settlements. The transition from this period to the dry conditions of the last 5 thousand years marks one of the most dramatic regional climate changes since the end of the last glacial period, but currently available records disagree over the timing and abruptness of the transition. This research develops records of wind-blown dust deposition-- a sensitive recorder of continental aridity and atmospheric circulation-- from a north-south transect of eight sediment cores from along the northwest African continental margin. These records will reveal whether the beginning and end of the African Humid Period occurred synchronously and with similar abruptness throughout North Africa. Fluvial sediment fluxes and dust grain size data from the cores will provide complementary insights into changes in precipitation and wind strength. In addition to elucidating the mechanisms driving abrupt climate changes in monsoonal regions, this project's broader impacts include support and mentoring for a new principal investigator in a postdoctoral position, involvement of undergraduate students in research, and adaptation of project findings for inclusion in undergraduate Earth science courses at Columbia University and in high school curricular materials.

OUTCOMES: Completed a full suite of radiocarbon, U/Th, and grain size data from five cores dating back 20ka. These data indicate that the ODP658C terrigenous flux record is representive of dust fluxes over a large region of northwest Africa. Found that the African Humid Period came to an abrupt end at 5.51+/-0.19ka ago and occurred much faster than ODP658C suggests.