Tracing sand-types across the Sverdrup Basin, Canadian Arctic

Within the Late Paleozoic-Cretaceous Sverdrup Basin and the overlying Paleogene strata there are thick, laterally extensive, commonly quartz-rich, sandstone-dominated formations. These sandstones yield provenance data which may, on a circum-Arctic scale, cause us to question current plate and palaeogeographic reconstructions, and locally, help to trace and predict the occurrence and quality of hydrocarbon reservoirs.

The study involved 4 field seasons along the northern and southeastern margins of the Sverdrup Basin on Ellesmere and Axel Heiberg islands. Our approach involves collection of field data by multidisciplinary teams and a comprehensive analytical programme. An age framework is provided by integrated biostratigraphy (macropalaeontology, palynology and micropaleontology). Sediment provenance and transportation information is provided by field observations, petrography, heavy mineral analysis, mineral geochemistry, detrital zircon dating, and palynology (reworked fossils). Uplift and burial histories are provided by vitrinite reflectance and apatite fission track analysis.

We will use an example from the southeastern Sverdrup Basin (Slidre Fiord, Ellesmere Island) to illustrate the changes in sediment provenance observed, and then begin to trace these changes to other parts of the basin. At Slidre Fiord we identify at least 4 sand-types and can place time constraints upon the provenance changes:

• Triassic (Norian and older) and mid Jurassic sandstones have common provenance signatures; they are sublitharenites and subarkoses with abundant apatite and Permo-Triassic detrital zircons
• At the Triassic-Jurassic boundary there is a pulse of mature sandstone, lacking in apatite and Permo-Triassic detrital zircons
• During the mid Jurassic the metamorphic grade of the sediment source area increased, suggesting either an unroofing history, different or possibly deeper source
• Early Cretaceous mature sandstones have a different signature to the underlying units, containing abundant Proterozoic-Archean detrital zircons
• Late Cretaceous-Paleogene sandstones contain kyanite (high-pressure metamorphism) and volcanic debris

Based on published paleogeographic reconstructions it is predicted that sediments on the north and south side of the Sverdrup Basin may have different provenance signatures. However, when data were collected from opposing sides, surprisingly, similar sediment provenance trends are noted, and many of the sand-types identified in the southern part of the basin are also recognised in the northern part.

• Sandstones of Triassic, Norian and older, and mid Jurassic age are characterised by abundant apatite and Permo-Triassic detrital zircons,
• Late Triassic-Early Jurassic a pulse of mature sandstone with few apatite grains and lacking Permo-Triassic detrital zircons.

Work is now underway to provide the same sand-type framework in other parts of the Sverdrup Basin, and to determine the sedimentary source regions. An increase in sandstone compositional maturity at around the Triassic/Jurassic boundary has also been reported from the Barents Shelf. Prior to early Cenozoic breakup, and formation of the Eurasian Basin and the Norwegian-Greenland Sea, the Sverdrup Basin and the Barents Shelf were much closer together. Therefore sedimentary succession in the two areas may share a common provenance history. CASP is undertaking a comprehensive provenance analysis programme of Permian to Paleogene age sandstones from the Barents Shelf. This will allow us to determine whether the sandstones from the Sverdrup Basin and the Barents Shelf have a common provenance, prior to breakup. The data from this on-going study provide a framework on which we can base models of sediment provenance and transport, therefore constraining palaeogeographic reconstructions.