The Arctic Eurekan orogen: A most unusual fold-and-thrust belt
The Tertiary Eurekan orogen of northernmost North America differs from a standard fold-and-thrust belt in several respects. It lacks a metamorphic-plutonic hinterland and wedge-shaped profile; instead, 2-km-high mountains of southeast Ellesmere Island face the frontal thrust, whereas halotectonic polygons, gentle warps, and subdued topography extend from Axel Heiberg Island in the center of the system back to the Sverdrup Rim at its rear. Clastic deposits are not located in a single flexural foredeep but are distributed in topographic lows amid several thrust sheets. The age of the stratigraphy, amount of displacement, and intensity of strain all increase cratonward, and the system9s width-to-length ratio is anomalously high. The orogen is attributed to Greenland9s pivotal movement relative to North America, which formed a braided Cenozoic plate boundary in Ellesmere and Axel Heiberg Islands, not a single transform in Nares Strait as previously proposed. The three major strands of this braided system are the Parrish Glacier, Vesle Fiord, and Stolz thrusts. They die out toward a structural pole of rotation in the south, whereas to the north, movement is accommodated by a dextral transpression zone extending from Lake Hazen to northern Greenland. Field studies on Ellesmere Island combined with a regional synthesis of previous work show that Eurekan deformation style is indicative of pivotal tectonism, that the contraction necessary to accommodate Greenland9s displacement is similar in magnitude to that documented by Eurekan structures, and that the ages of continental structures are compatible with the paleomagnetic record of seafloor spreading in Labrador Sea and Baffin Bay. Previously proposed sinistral strike-slip displacement is not confirmed; rather, eastvergent thrusts and dextral wrench faults typify the system. We propose that the Eurekan orogeny marked a change from tip propagation to pivotal tectonism as the North Atlantic rift system penetrated the entire width of the Laurasian continent.