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We interpret the kinematics of the Tangra Yumco (TYC) rift by evaluating spatiotemporal trends in fault displacement, extension onset, and exhumation rates. We present new geologic mapping, U-Pb geochronology, zircon (U-Th)/He (ZHe) thermochronology, and HeFTy thermal modeling results that are critical to testing dynamic models of extension in Tibet. The TYC rift is bounded by two NNE striking (~N10°E-N35°E) high angle (~45-70°) active normal faults that alternate dominance along strike. Footwall granodiorites show foliation, slip lineation, and fault plane striation measurements indicative of northeast directed oblique sinistral-normal slip. In North and South TYC, hanging wall deposits are cut by a series of active high-angle normal faults which likely sole into a master fault at depth, while in central TYC, hanging wall deposits display synthetic graben structures potentially indicative of low-angle faulting. Analysis of ~50 samples collected across key structural relationships in and around TYC yield 14 mean U-Pb dates between ~59-49 Ma and ~190 single-grain ZHe dates between ~60-4 Ma with spatial trends in ZHe data correlating strongly with latitude. Samples from Gangdese latitudes show a concentration of ~28-15 Ma ages, while those north of ~29.8° latitude yield both younger (~9-4 Ma) and older (~59-45 Ma) ages. We interpret (1) Gangdese Range samples reflect exhumation during contraction and uplift along the GCT peaking at ~21-20 Ma, (2) ~9-4 Ma ages reveal extension timing along fault segments experiencing significant rift-related exhumation, and (3) ~59-45 Ma ages represent un-reset or partially-reset samples from fault segments that have experienced lesser magnitudes of rift exhumation. HeFTy thermal models indicate a two-stage cooling history with initial slow cooling followed by accelerated cooling rates in Late Miocene-Pliocene time (~13-4 Ma) consistent with prior results from TYC and other Tibetan rifts. Our data are consistent with a segment linkage fault evolution model for the TYC rift, with underthrusting of Indian lithosphere likely related to the northward acceleration of rifting. Future work will utilize advanced HeFTy modeling including U-Pb and apatite fission track data to further constrain the exhumation history of TYC and test dynamic models of extension for southern Tibet.
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This content will become publicly available on October 20, 2026
Exhumation History of Rift-Flank Uplift along the Amagmatic Tanganyika Rift in the East African Rift System, Tanzania
The East African Rift (EAR) system is an important geological analog for continental rifting. Despite decades of research, the precise timing of the onset of rifting and the magnitude of faulting remains opaque. This challenge is compounded in magma-poor segments of the EAR, such as Lake Tanganyika. Lake Tanganyika (LT) is a major geomorphological expression of the western branch of the EAR system. Multiple kinematic studies in LT have focused on the timing, amount of extension, and sediment accumulation within the lake axis. However, constraints on the basin-bounding fault history are needed to fully assess the kinematics of the entire rift transect. This study seeks to provide an age-elevation profile of low-temperature thermochronology data across two transects in the hanging wall blocks on the eastern side of LT (Tanzania). Preliminary thermochronology samples will be collected in the central and northern sections of LT. With an average relief of ~1550 m in the central section (Mahali National Park) and ~850 m in the northern section (Kigoma). The age elevation profiles will enable us to evaluate the onset and magnitude of tectonic exhumation. It has been hypothesized that LT experienced multiple phases of extension in the Mesozoic, Paleogene, and Miocene. Results of the timing of exhumation from the northern and southern sections will support or challenge competing hypotheses of the LT rift evolution. Similar exhumation histories from the two profiles will confirm the model of co-evolution of the LT along its strike, while a different timing of exhumation (younger in the north compared to the central region) will support the long-standing hypothesis of the rift propagation model.
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- Award ID(s):
- 2425127
- PAR ID:
- 10656893
- Publisher / Repository:
- Geological Society of America Annual Meeting
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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