Abstract

Cretaceous–Paleocene strata of the Labrador Shelf and the Davis Strait are composed of clastic sedimentary and volcanic rocks, and some of these strata are considered possible petroleum reservoirs. The U-Pb provenance distributions of detrital zircons from nine different wells located in Davis Strait and on the Labrador Shelf, and which penetrate these rocks, were studied by LA-ICP-MS in order to assess sediment dispersal patterns and distribution of potential reservoirs. Samples from the mid-Cretaceous Bjarni Formation, the Upper Cretaceous Markland Formation, and the Paleocene Cartwright Formation were analysed.

Based on U-Pb provenance data, the Bjarni Formation can be divided into northern and southern depositional areas. The northern area is dominated by 3000 Ma and 3200 Ma zircons, interpreted as derived primarily from the Hopedale block; in contrast, the southern area is dominated by 1800–1700 Ma ages, interpreted to be derived from the Makkovik Province and the Grenville Province. Markland Formation strata also show a variation in ages from north to south. Strata in the northern area are dominated by Archean zircons, with the main population at 3600–3500 Ma and significant numbers of 3800–3700 Ma and 2800–2700 Ma ages; in the southern area, no Eoarchean zircons were noted and strata are instead dominated by 3200–3100 Ma, 2900–2800 Ma, and 1800 Ma zircon populations. The Saglek block is interpreted as the dominant source for the northern area, mixed with sediment from the Hopedale block; the source for the southern area is inferred to be a combination of the Hopedale block and the Makkovik Province. Finally, the Cartwright Formation also shows distinct variations in source depending on the area. The northernmost samples yield a range of ages, and hence represent a large source area, with dominant zircon ages of 2800–2700 Ma. The middle area is dominated by a broad peak in ages from 3200–2550 Ma, whereas the southern area is dominated by Paleoproterozoic ages, with a large population at 1800 Ma. The general pattern for the Cartwright Formation is similar to that of the Bjarni and Markland formations in that the sediment transport direction was northerly and the main sources are interpreted to have been the Saglek block, Hopedale block, and the Makkovik Province. In addition, signatures from the Grenville Province, the Nain Plutonic Suite, and the Appalachian Orogen are also present. The detrital zircon patterns of the wells are consistent with Labrador as the main source region and the overall pattern indicates that the main sediment transport direction was generally northerly from Early Cretaceous until Paleocene time.

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