A Multi-Proxy Stalagmite Record of Paleoenvironmental Change in Equatorial Africa during the African Humid Period

Abstract:

A multi-proxy record from U-Th dated Stalagmite MAT-12 from Matupi Cave (1.19°N, 30.01°E) in northeastern Democratic Republic of Congo provides a reconstruction of the paleoenvironmental effects of the African Humid Period (AHP) in eastern equatorial Africa. Results from stable isotope analysis (δ¹³C, δ¹⁸O) and petrographic analysis (mineralogy, layer specific width, and layer bounding surfaces) are paired with a high-resolution radiometric U-Th age model to reveal the local response to the AHP, a climate event of the late Pleistocene to mid-Holocene, 14,800 to 5500 yr BP. During the AHP, much of north and east Africa was wetter than the present. Though various proxy records have demonstrated the orbitally-forced, pluvial nature of the AHP, much debate has surrounded the spatial and temporal patterns of AHP onset, intensity, and termination. This new record from our ongoing study highlights the local effects of the AHP and its termination specific to eastern equatorial Africa. Though the 1300-year record from Stalagmite MAT-12 is somewhat brief and only covers a portion of the AHP, it provides a detailed reconstruction of changes in vegetation and rainfall near Matupi Cave while Stalagmite MAT-12 was deposited. Our preliminary assessment of the stable isotope and petrographic data suggests a pronounced wet period from ca. 8000 to 7800 yr BP, soon after the 8.2 ka event, and followed by gradual drying until ca. 6750 yr BP when Stalagmite MAT-12 ceased growth. This gradual drying suggests that the transition to AHP termination in eastern equatorial Africa was likely not as abrupt as the transition to AHP termination in northern Africa that is well-documented in the literature. Our record supports the previously-suggested notion of a time-transgressive termination of the AHP, with great potential for differences in local response.