The Growth of Mountains and the Petroleum Systems in the Canadian Arctic Archipelago: Thermochronology Constraints
Marcos Zentilli1 and Alexander M. Grist2
1Dalhousie University, Halifax, NS, Canada.
2Univ. of Queensland, Queensland, QLD, Australia.
The Princess Margaret Range (2,110 m), Axel Heiberg Island, Nunavut, is analogous to the mountains of Ellesmere Island (2,616 m). These mountains grew during the Eurekan Orogeny that resulted from interaction between Greenland and Arctic Canada from late Paleocene to Eocene. Fission track (FT) and (U-Th-Sm)/He thermochronology has been used to constrain the timing of major faulting and exhumation in the region. The Princess Margaret Range lies in the hanging wall of the Stolz Thrust, a ca. 150 km long, NNW structure that puts Sverdrup Basin Triassic-Jurassic rocks over Eocene sediments. Sandstones and conglomerates shed into a foreland basin resulting from the advance of the Stolz Thrust host the well-known Tertiary Fossil Forest of the Geodetic Hills; it contains slightly coalified remnants of Metasequoia, which grew at a paleolatitude of ca. 80.2 N during an exceptionally warm and humid period.
Zircon fission track (FT) dating in the Princess Margaret Range show that Cretaceous sills and dykes thermally affected Triassic strata; basin modelling confirms that the intrusions negatively affected the petroleum potential of pre-Cretaceous rocks in the basin’s depocentre. Apatite samples from Cretaceous sills in the hanging wall of the Stolz Thrust yield cooling FT ages of 60 to 48 Ma similar to those from the hanging wall of thrust faults in Ellesmere Island. Time-temperature modelling suggests that the rocks cooled rapidly between 50 and 30 Ma, coinciding with exhumation and the rise of the developing Princess Margaret Range. Apatite within sandstones hosting the Fossil Forest yield ages of 49 Ma, the FT cooling age of the source, and the sandstones remained near the surface since the Eocene. Higher degrees of coalification affected Palaeocene and Eocene coals overridden by thrust faults in eastern Ellesmere Island. Thrust belts have less petroleum potential than the intervening thermally undisturbed parts of the Sverdrup Basin, but may have gas potential. Salt diapirs had significant effects on the thermal history of the rocks: strata cooled below 100oC up to 20 m.y. later in areas underlain by salt canopies in Expedition Fiord.
AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.�����������������������������������