Collaborative Research: Magnitude and timing of shortening in the Greater Caucasus: Locus of Late Cenozoic Arabia-Eurasia convergence?

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The Greater Caucasus Mountains extend for nearly 1000 km between the Black and Caspian seas and form the northernmost margin of the Arabia-Eurasia collision zone. This range has long been speculated to play a central role in accommodating oblique convergence within the collision. Recent GPS studies indicate shortening rates of 10 to 13 mm/yr across the easternmost Greater Caucasus, which represents 50 to 85% of the total 15 to 20 mm/yr of far-field Arabia-Eurasia convergence. Although GPS and earthquake data clearly imply that the eastern Greater Caucasus now plays a central role in accommodating Arabia-Eurasia convergence, current available data are insufficient to confidently determine if strain has been similarly focused in the range throughout the late Cenozoic. In this three-year project, an international team of scientists from the United States, Azerbaijan, Georgia, and the Russian Federation is testing the hypotheses that: 1) the Greater Caucasus range is a first-order structural system that formed by strain localization within the Arabia-Eurasia collision; 2) surface uplift began approximately 10 million years ago due to focusing of 50 to 80% of total Arabia-Eurasia convergence in the range; 3) the timing and magnitude of both exhumation and shortening systematically decrease from west to east along-strike due to eastward propagation of the range; and 4) strain localization within the Greater Caucasus may be the result of the consumption of a relict ocean basin, of which the Black and South Caspian seas are remnants, that was trapped during formation of the orogen in the late Cenozoic. These hypotheses are tested through a field-based, integrated structural, neotectonic, and thermochronologic study of the Greater Caucasus Mountains and the Kura fold-thrust belt, which flanks the southeastern margin of the range in Georgia and Azerbaijan.Almost 40 years after the advent of the theory of plate tectonics, earth scientists are still debating how continents deform when they collide along the boundary between two converging plates. Addressing this question is important for understanding where, how often, and why deformation is suddenly released during earthquakes along faults, how those faults form and behave over time, why they form in some places and not others. The ongoing collision between the Eurasian and Arabian continents produced the highest mountain range in Europe, and the second largest region of active continental collision on Earth. The center of this collision is defined by the Greater Caucasus Mountains, which extend for approximately 1000 km between the Black Sea to the west and Caspian Sea to the east. This mountain belt appears to have formed in only the last 5 to 10 million years, thus providing an unusual opportunity to study the initial stages of continental deformation and mountain building. Results from this research will advance the understanding of continental deformation, the geological conditions in this region that led to the formation of rich oil reserves in the South Caspian basin and eastern Azerbaijan, and the earthquake hazards in this heavily populated and economically important region. This region has been struck by devastating earthquakes in the past, such as an earthquake in 1988 in Armenia that killed at least 25,000 people. The project will support the Ph.D. research of students at the University of California at Davis and the University of Michigan, while also providing important educational and research opportunities for undergraduate students at both universities.