Semester of Graduation

Fall 2020

Degree

Master of Science (MS)

Department

Geology and Geophysics

Document Type

Thesis

Abstract

Located along the northernmost boundary of the Arabia-Eurasia collision zone, the Greater Caucasus are a young, actively deforming mountain range striking WNW-ESE between the Black and Caspian Seas. Previous thermochronometric studies predominantly focused on the western portion of the range partially constrain the thermal and tectonic history of the Greater Caucasus. However, due to the complex nature of the tectonics in the region, multiple competing tectonic models have been suggested to explain the exact timing of collision and onset of rapid uplift. Furthermore, the Greater Caucasus exhibit competing along-strike gradients in modern shortening rates, mean annual precipitation, structural architecture and lithology, yet topography throughout the range remains remarkably similar. In an attempt to investigate the controversial tectonic regime and along-strike gradients, we utilize detrital zircon (U-Th)/He thermochronology from seven sediment samples that nearly span the entirety of the range and thermally model the cooling ages for each sample. Five of the seven samples consist of reset, partially reset, and un-reset detrital zircon cooling ages and the two remaining samples predominantly consist of reset ages. Thermal modelling for this set of samples predicts a variety of possible time-temperature paths before 10 Ma, however, consistently suggest a period of rapid cooling (>20°C/Myr) between ~8-1 Ma with total amount of exhumation ranging from ~5-8 km. Cooling rates, timing and total amount of exhumation are reasonably consistent with previously published results from the western, western-central, and eastern portions of the Greater Caucasus, and do not exhibit any major spatial trends along-strike. Additionally, long-term exhumation rates, millennial erosion rates, and decadal convergence rates appear fairly constant with minimal temporal variations throughout time. Rapid uplift at ~5 Ma is likely v a result of hard collision between the Lesser Caucasus and Eurasian basement, which is also coincident with a major reorganization of the Arabia-Eurasia plate boundary. Furthermore, similar cooling histories and total exhumation along-strike suggests uniform topography in the Greater Caucasus reflects the long-term uplift history.

Committee Chair

Forte, Adam

DOI

10.31390/gradschool_theses.5233

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