McGlue, Michael M.; Lezzar, Kiram E.; Cohen, Andrew S.; Russell, James M.; Tiercelin, Jean-Jacques; Felton, Anna A.; Mbede, Evelyne; Nkotagu, Hudson H.
Description:
New intermediate-resolution, normalincidence
seismic reflection profiles from Lake
Tanganyika’s central basin capture dramatic evidence
of base-level change during two intervals of the late
Pleistocene. Four seismically-defined stratigraphic
sequences (A–D) tied to radiocarbon-dated sediment
cores provide a chronology for fluctuating environmental
conditions along the Kalya Platform. Stacked,
oblique clinoforms in Sequence C are interpreted as
prograding siliciclastic deltas deposited during a
major regression that shifted the paleo-lake shore
*21 km towards the west prior to *106 ka. The
topset-to-foreset transitions in these deltas suggest
lake level was reduced by *435 m during the period
of deposition. Mounded reflections in the overlying
sequence are interpreted as the backstepping remnants
of the delta system, deposited during the
termination of the lowstand and the onset of transgressive
conditions in the basin. The youngest
depositional sequence reflects the onset of profundal
sedimentation during the lake level highstand. High
amplitude reflections and deeply incised channels
suggest a short-lived desiccation event that reduced
lake level by *260 m, interpreted as a product of
Last Glacial Maximum (32–14 ka) aridity. Paleobathymetric
maps constructed for the two interpreted
regressions reveal that despite the positive lake-floor
topography created by the Kavala Island Ridge
Accommodation Zone, Lake Tanganyika remained
a large, mostly connected water body throughout the
late Pleistocene. The results of this analysis further
imply that Lake Tanganyika is the most drought
resistant water body in the East African tropics, and
may have acted as a refuge for local and migrating
fauna during periods of prolonged aridity.