Collaborative Research: Suturing the Heart of Asia: Tectonics of the Mongol-Okhotsk Ocean Closure

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The closure of ocean basins and formation of supercontinents throughout geologic history have directly influenced the distribution of natural hazards and natural resources. Changes in the distribution of ocean basins and land masses have also impacted the history of Earth's climate and the evolution of life. The modern-day continent of Asia consists of remnants of old continents, relict ocean basins, and fragments of island chains assembled over hundreds of millions of years. The ancient Mongol-Okhotsk Ocean was one of the largest oceans that previously separated fragments of the present core of the Asian continent, and yet remarkably little is known about it. This study examines the timing and mechanisms of the closure of the Mongol-Okhotsk Ocean through a multidisciplinary approach that includes field mapping and dating of key rock types. The project supports collaborations between diverse scientists from universities in the US and Mongolia, and training and mentoring of US and Mongolian students. Outreach efforts associated with this project include new educational resources for US and international students, along with new educational modules on plate tectonics, supercontinents, and geologic time for secondary school students.This project integrates stratigraphic, paleomagnetic, structural, and geochronologic datasets for the Mongol-Okhotsk suture that are assessed in the context of competing end-member hypotheses regarding modes of ocean basin closure and continental collision, such as major oroclinal bending as compared with scissor-like suturing. The project also investigates the role of strike-slip faulting during ocean closure and its relationship to subsequent orogenic collapse. Research outcomes are multidisciplinary and include: 1) stratigraphic analyses to document marine-nonmarine facies transitions and better delineate subtypes of remnant ocean basins; 2) structural datasets that document deformation in the nominal western hinge zone near the Hangay Dome; 3) verification of existing low-volume paleomagnetic data sets and new reference poles to improve APWP comparisons; and 4) development of an overarching geochronologic framework for key rock types. The project includes collaboration with international teams focused on regional magmatism and metallogeny.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.