Sedimentological data from the Tanquary High: new constraints for Triassic to Jurassic extensional fault activity in the Sverdrup Basin, NE Canadian Arctic.

The Sverdrup Basin constitutes a Carboniferous to Late Cretaceous presently inverted extensional basin exposed in the NE Canadian Arctic. Its contains up to 13 km of Carboniferous to Late Cretaceous strata unconformably overlain by latest Cretaceous to Palaeogene sediments from the Eurekan Orogen. These rocks constitute important sources of information to constrain the yet enigmatic geological evolution of the neighbouring Amerasia Basin.

However, there is still significant uncertainty regarding the key tectonic events that controlled the development of the Sverdrup Basin. The main reason for this incertitude is that deformation associated with the Eurekan Orogeny overprinted any structures related to the development of the basin and direct observations of potential Carboniferous to Late Cretaceous faults are difficult, if not impossible. The prevailing view is that the basin was initiated as a result of rifting during the Mississippian which persisted until the early Permian. The rest of the Sverdrup Basin evolution, from the mid Permian to the Late Cretaceous, was characterised by two long periods of tectonic quiescence and thermal subsidence interspersed with one period of renewed rifting during the Late Jurassic to the Early Cretaceous. This model fails to explain the creation of accommodation space for 13 km of strata.

Based on sequential restorations of structural cross-sections, unpublished work by CASP identified syn-sedimentary Triassic and Jurassic extensional faults in the Sverdrup Basin across which strata change their thickness. However, the lack of published works studying thickness variations at basin scale prevented us from estimating the timing of deformation in more detail. This communication presents sedimentological data from the Tanquary High, a basin-scale basement high located in the Sverdrup Basin margin, where significant thickness changes on the Carboniferous to Cretaceous sediments have been observed in the existing maps and are likely related to syn-sedimentary faults. Stratigraphic columns were logged in the field in order to quantify these thickness variations and to identify major stratigraphic trends. Our results support two main phases of extensional fault activity, one occurring during the Carboniferous to the Mid Triassic and the second one from the Late Triassic to the Jurassic. These newly recognised periods of extensional faulting should be relevant to constrain the palaeogeographic reconstructions of the Arctic.