Intraplate orogenesis within accreted and scarred lithosphere: Example of the Eurekan Orogeny, Ellesmere Island

摘要

The Eurekan Orogeny, which created much of the high topography of Ellesmere Island and adjacent Greenland, exhibits a crustal architecture linked to intraplate orogenesis in the Cenozoic It is generally considered that the rotation of Greenland in the Eocene (related to sedimentary basin formation in Baffin Bay) produced compressional intraplate tectonics. Deformation in the region is notably localized to the Central Ellesmere Domain and the Northern Ellesmere Domain. However, an important tectonic feature of Ellesmere Island is the Hazen Stable Block, which shows horizontal Paleogene Eureka Sound group strata overlying Palaeozoic-age steeply dipping beds. The intense deformation in the Hazen Stable Block is related to continental orogenesis in the Late Silurian-Devonian. Therefore, the Hazen Stable Block is thought to have undergone only minor Eurekan-age (55-35 Ma) deformation, while surrounding (highly deformed) units may have re-activated faults from Paleocene continental amalgamation. Here, high-resolution thermal-mechanical numerical experiments are implemented to explore lithospheric deformation (related to continental shortening) for a range of tectonic scenarios, namely, the presence of inherent deformational "scars" and rheologically strengthened crust/mantle lithosphere (both due to ancient continental accretion). This study marks the first geodynamic excursion to this high Arctic region, and we present some of the first interpretations of the development of Eurekan-age lithospheric evolution. Our results show that a rheologically strong Hazen Stable Block crust produces tectonics similar to the Eurelcan Orogeny. Furthermore, lithospheric scars can generate more localized deformation and topography than rheological changes to the lithosphere and may offer a new interpretation on enigmatic intraplate tectonics. (C) 2015 Elsevier B.V. All rights reserved.