TECTONIC RESPONSE OF THE ARCTIC REALM TO THE OPENING OF THE NORTH ATLANTIC OCEAN

Sea floor spreading of the North Atlantic and the Baffin Bay / Labrador Sea caused northwards movements of Greenland and collision of Greenland with Ellesmere Island and Svalbard, resulting in the Eurekan intraplate orogeny. The Eurekan forms a >2500 km long belt across the High Arctic. Generally, controlling mechanisms of intraplate orogenies are poorly understood, but they may be caused by far-field effects of processes along distant plate margins. Both margins of the northern North Atlantic along the Fram Strait, i.e., the eastern Wandel Hav belt of North Greenland and the Prins Karls Forland of Svalbard, are characterized by high thermal maturation, with vitrinite reflectance values up to >9%. This symmetric pattern of thermal maturation may be related to thermal effects of North Atlantic opening. For understanding relationships between North Atlantic opening and the exhumation of the Eurekan belt, we investigated samples from northern Ellesmere Island, North Greenland, and Svalbard by low-temperature thermochronology. For northern Ellesmere Island, we found periods of rapid exhumation between ~66- 60 Ma, 55-48 Ma, 44-38 Ma, and 34-26 Ma. Rapid exhumation directly correlates with changes of spreading directions and spreading rates in the North Atlantic, suggesting that the opening of the North Atlantic is the main driving force for Eurekan deformation. Presumably, northern Ellesmere Island was coupled to strike-slip tectonics along the De Geer Fault between Greenland and Svalbard and thereby to movements of the North Atlantic spreading systems. After ~26 Ma, Ellesmere Island was decoupled from the De Geer Fault due to the incipient opening stages of the future Fram Strait. Our thermochronology data from North Greenland and Svalbard are still preliminary. However, initial results clearly show that the areas of high thermal maturation along both sides of the Fram Straits have experienced different thermal histories: the eastern margin of North Greenland is characterized by Paleocene fission track and (U-Th-Sm)/He dates, whereas western Svalbard is dominated by Oligocene dates, suggesting that the thermal maturation “event” occurred asynchronously across both margins of the (future) Fram Strait. The central Wandel Hav belt mostly shows Eocene exhumation, similar to northern Ellesmere Island.