An integrated geophysics cruise to map the northern edge in the Chukchi Borderland and the adjacent Canada Basin - constraints on basin history and crustal structure

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Over the last fifty years, we have learned the ocean basins are relatively young. Knowing their history is necessary to understand the ancient, adjacent continents. The Amerasia Basin of the Arctic Ocean is a mystery. While it is an ocean basin, the familiar patterns created by seafloor spreading are not obvious. As a result, it has not been possible to understand the basin history. This project will study the history of three adjacent features in the Amerasia Basin: the Chukchi Borderland, the Alpha Ridge and the Canada Basin This project plan to use the Geological Survey of Denmark and Greenland (GEUS) portable, flexible multi-channel seismic reflection (MCS) system on a research vessel. This system, which has been successfully operated in thick pack ice, will collect MCS data, for stratigraphic and structural interpretation, and provide sufficient source strength for full crustal refraction work. Stronger constraint on the deep crustal structure will be obtained in two locations in the Canada Basin with ocean bottom seismometers (OBS). Refraction data will also be acquired with sonobuoys during MCS profiling and will be used to model upper crustal structure. The collection and analysis of the data will provide new knowledge about the formation of the Amerasia Basin and improve our understanding of the history of northeast Eurasia and northwest North America. This project will also help educate a new generation of Arctic marine geoscientists, support scientific ocean drilling to sample the sediments below the seafloor and help define the extent of US territory in the Arctic Ocean. For the most part, current understanding of the Amerasia Basin is based on observations made on the adjacent continents and an assumption about the tectonic displacements that formed the basin. A new approach based on establishing critical relationships between adjacent features will make it possible to recreate the tectonic history of the ocean by scaling up from local relationships. The Chukchi Borderland is a block of extended continental crust embedded in the deep water Amerasia Basin. To understand the basin opening, it is necessary to restore the Borderland to its pre-opening position. The choice of this position distinguishes tectonic models of the basin which are not well constrained by observations. In previous work, a 2- MCS survey across the transition from the Chukchi Shelf to Borderland established that there have been only slight displacements across this boundary since Early Cretaceous. Understanding the structure and history of the northern edge of the Borderland, known primarily from bathymetric data, is the next step. In this area, three of the major structures of the Amerasia Basin intersect: the Borderland, Alpha Ridge and the Canada Basin. A dedicated MCS survey in this area will improve our understanding of these structures and their termination or continuation below the sediment cover to the north and east. In this project, MCS and refraction surveys will elucidate the relations between the overtly continental, high-standing block and the surrounding crust, which may be, in part, of continental composition as well. Observing the northern edge of the Chukchi Borderland and adjacent deeper water areas will, by distinguishing crustal types, provide new constraints on the history of the Amerasia Basin.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.