T35 Advances and Applications of Thermochronology to Tectonic, Magmatic, Basin, and Geomorphic Problems (Posters)

Sunday, 22 September 2024
8:00 AM - 5:30 PM
Hall D

CONSTRAINING THE INITIATION OF RIFTING IN A MAGMA POOR SYSTEM: LAKE TANGANYIKA (EAST AFRICAN RIFT)

Paper number: T35-7
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

The East African Rift (EAR) is commonly cited as a modern analog for early stages of continental rifting. Lake Tanganyika lies within the western branch of the EAR. The modern Tanganyika rift consists of discrete normal faults that alternate facing direction down the rift axis, with footwall relief that can exceed 2.5 km and subsided hanging wall basins with > 5 km of sediment fill. However, the age of rift-related uplift and subsidence along Lake Tanganyika is poorly constrained and mostly derived from the basin-fill, but these estimates are dependent upon assumptions of long-term rates of sediment accumulation. Low-temperature thermochronology can capture tectonic/erosional events by tracking the exhumation of minerals within rocks from depth following normal faulting through fission track analysis. Previous studies have applied low-temperature thermochronology in other rift segments of the western branch, but no studies have included the footwall uplifts of Lake Tanganyika. Here, apatite fission-track (AFT) analyses were applied to riverine detritus along two different footwall uplifts of the Tanganyika rift axis, to track rock cooling and infer the associated exhumation history. AFT analysis of these detrital samples yields a broad range of single-grain ages from Miocene (13 Ma) to Silurian (366 Ma) in central Lake Tanganyika and Eocene (41 Ma) to Neoproterozoic (842 Ma) in southern Lake Tanganyika. The cooling age populations in central Lake Tanganyika are consistent with previous basement AFT ages from the Albertine Rift to the north and Lake Malawi Rift to the south, both interpreted to result from Cenozoic rifting along rift flanks in the western branch. However, the southern sample captures cooling associated with Permo-Triassic to Cretaceous rifting. These AFT data suggest that rifting nucleated in the center basins then continued along the rift axis as opposed to coeval rift initiation across all subbasins. Continued thermochronological analysis along the length of the rift will help further constrain the rift history of Lake Tanganyika.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-401778

© Copyright 2024 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.