Early Tertiary Eurekan palaeostresses in the Eastern Sverdrup Basin (Ellesmere and Axel Heiberg Island, Canadian Arctic Islands)

Abstract

Two successive and independent stress regimes related to the Late Cretaceous to Early Tertiary Eurekan Orogeny have been identified in Upper Palaeozoic and Lower Tertiary strata of the Eastern Sverdrup Basin in the northeast Canadian Arctic (Ellesmere and Axel Heiberg Island), using small-scale tectonic structures. The oldest, minor event is related to a NE-ENE orientation of the maximum stress σ 1. It is likely to correspond to the sinistral oblique-slip motion of Greenland with respect to Ellesmere Island which mainly occurred between magnetic anomalies 25 (Late Paleocene) and 24 (Early Eocene) and supports the hypothesis of distributed shear during the early stage of the Eurekan Orogeny. The youngest, major stress regime recorded in the uppermost Middle Eocene (possibly to Early Oligocene) rocks of the synorogenic Eureka Sound Group, is compressional and is characterized by a WNW-ESE (eastern Axel Heiberg Island) to NNW-SSE (northern Ellesmere Island) orientation of the maximum horizontal stress σ 1. It can be correlated with the northwestward convergent motion of Greenland toward Ellesmere Island between magnetic anomalies 21 (Middle Eocene) and 13 (Early Oligocene); the resulting fan-shaped stress pattern can be explained by the indentation of the Canadian Shield into the Sverdrup Basin. Structural evidence for the initial Late Cretaceous-Paleocene counter-clockwise rotation of Greenland with respect to the Canadian Shield between anomalies 34 (Campanian) and 25 (Late Paleocene) has not been found in the studied areas.