46 Limnogeology: Sedimentary Records from Modern and Ancient Lakes II

Friday, 29 March 2019
2:00 PM - 3:00 PM
Gold Ballroom

PATTERNS AND INDICATIONS OF LIMNOGEOLOGICAL CHANGE IN HOLOCENE-AGED SEDIMENTS FROM LAKE TANGANYIKA (EAST AFRICA)

Paper number: 46-3
Program: Theme Sessions
Time: 2:40 PM – 3:00 PM

Authors

Abstract

Exploring for signals of limnological change in Holocene-aged sediments is important for understanding how climatic and hydrological variability impacts Lake Tanganyika, the second largest lake in Africa. Lake Tanganyika is a biodiverse meromictic lake with anoxic bottom waters, which makes it an excellent environment for preserving proxy-rich sediments that can be dated using radiocarbon. This research outlines two sediment cores collected from the Nitiri horst and ramp, relatively unknown deepwater settings in southern Lake Tanganyika. Techniques in sedimentology (facies analysis) and geochemistry (carbon content) were applied to radiocarbon dated cores, in order to infer limnogeological changes (e.g., upwelling, paleo- productivity) at the coring sites. Initial results of the analysis indicates that the Nitiri horst experiences slow sedimentation rates, whereas the ramp site experiences much faster sedimentation, as well as multiple sedimentary processes. Both cores contain a cm-thick tephra layer which may prove useful for chronological control, as well as carbonate laminae that may indicate lake level lowstands. In the ramp core, thick green-yellow diatom laminations are especially prominent and these are tentatively interpreted to have resulted from algal blooms associated with wind mixing and vertical nutrient transport. These data provide indications about how sedimentation is affected by climatic and hydrological changes, and bring to light a new opportunity to further unpack depositional, limnological, and volcanic processes in Lake Tanganyika’s southern basin.

Geological Society of America Abstracts with Programs. Vol. 51, No. 3

doi: 10.1130/abs/2019SE-326054

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