Provenance of Reservoir Sandstones in the Flemish Pass and Orphan Basins (Canada): U-Pb Dating of Detrital Zircons Using the Laser Ablation Method
Michael R. McDonough1, Paul Sylvester2, Simon Haynes1, Jaime Lo3, and Paul B. O'Sullivan4
1Statoil Canada Ltd., Calgary, AB, Canada.
2Earth Sciences, Memorial University, St. John's, NF, Canada.
3Husky Energy, Calgary, AB, Canada.
4Apatite to Zircon Inc., Moscow, ID.
U-Pb age dating has been undertaken on detrital zircon populations from Tithonian, Berriasian and Aptian age sandstones from wells in the Flemish Pass and Orphan basins, located in the northeastern Grand Banks of Atlantic Canada. Flemish Pass basin is filled with Kimmeridgian through Aptian rift sediments, and comprises an elongate oblique slip extensional basin, forming a displacement transfer system connecting late Jurassic to early Cretaceous rifting in the Jeanne d’Arc Basin to the south with extension in the Orphan Basin to the northeast. The main phases of rift-related sedimentation occurred in Tithonian and Berriasian times.
Utilising the laser ablation U-Pb method, 207Pb/206Pb ages have been determined for detrital zircons. Results of the laser ablation U-Pb dating are very consistent from well to well. There are three primary detrital zircon 207Pb/206Pb age populations present in Berriasian and Tithonian sandstones, which are: 1) 340-460 Ma; 2) 530-680 Ma; and 3) broadly Grenvillian ages in the range of 0.9-1.2 Ga. An important secondary age population in late Jurassic sandstones ranges from 295-325 Ma.
Detrital population (1) has multicyclic zircon grains with 340-460 Ma 207Pb/206Pb ages that are interpreted to be derived from the Central Meguma belt of the Appalachian orogen. Population (2) zircons are also multicyclic, and have 530-680 Ma 207Pb/206Pb ages that are indicative of sandstone provenance from the Avalon Belt of eastern Newfoundland, or alternatively from pre-Variscan granites of Flemish Cap and Iberia. The Grenvillian 207Pb/206Pb ages of population (3) can arguably have been derived from North American and/or Iberian sources, and are not diagnostic in terms of provenance.
Jurassic sandstones from 3 wells contain a secondary population of detrital zircons, which are first cycle grains with 295-325 Ma 207Pb/206Pb ages. Intrusive rocks of this age range are not known as a provenance source within North America. These are equivalent in age to Variscan granites of the Iberian Peninsula, and are therefore interpreted to be indicative of Iberian sediment provenance. Sandstones from the Flemish Pass basin also contain elongate, prismatic zircon grains with concordant 207Pb/206Pb ages that cluster at 141 Ma. Their morphology indicates that they are of volcanic origin, and they are interpreted to be rift related.
The new detrital zircon data from Flemish Pass and Orphan basins demonstrate an Iberian connection for sediment provenance, and therefore provide an independent validation of the Tithonian and Berriasian palinspastic reconstructions of the North Atlantic. Ongoing work is focussed on dating of Jura-Cretaceous sands from Orphan basin to test the Flemish Cap escape model, as well as high resolution U-Pb dating of both the detrital and volcanic zircon populations from Jura-Cretaceous sandstones in Flemish Pass and Orphan basins.
AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.������