The provenance of Lower Tertiary sands from the Labrador Shelf

• Main Author: Mills, Jean Louise
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1992
• Subjects: Labrador Shelf; Labrador Sea
• Online Access: https://research.library.mun.ca/6618/; https://research.library.mun.ca/6618/1/JeanneLouiseMills.pdf; https://research.library.mun.ca/6618/3/JeanneLouiseMills.pdf

The Mesozoic-Cenozoic sedimentary sequence under the Labrador continental shelf is a sand-shale sequence that records the evolution of the Labrador Sea from the rift stage, through the active sea floor spreading stage to the deep-ocean circulation stage. The sediment prism is thick, ranging from 10,000 to 15,000m and contains several sand units that have been targets for petroleum exploration. -- Seven of the 31 wells drilled in the Labrador Sea were chosen for this study. Samples of the Paleocene-age Gudrid sand of the Cartwright Formation and Eocene-age Leif sand of the Kenamu Formation were examined. -- Study of 37 light fraction grain mounts indicates that the sands are subarkoses and arkoses with middle- to upper-rank metamorphic rocks as dominant sediment sources. Heavy mineral analysis of 55 samples reveals a dominance of those minerals associated with metamorphosed acid plutonic rocks. -- Correspondence analysis of the heavy mineral data set generated in this study demonstrates some profound differences in the sands. The Paleocene-age sands are defined by four factors: (1) Amphibole factor, (2) Kyanite factor, (3) Zircon-Rutile factor, and (4) Epidote factor. The Eocene-age sands are defined by the Staurolite-Garnet-Tourmaline factor. The differences between the groupings of samples is thought to be suggestive of differences in sediment source. The variability in the Paleocene samples likely represents sediment derived from local areas proximal to the site of deposition, while the similarities between the Eocene samples indicate sediment mixing and homogenization. -- The principal source rocks for the Tertiary sands from the Labrador Shelf were amphibolite facies metamorphic rocks (particularly kyanite-, garnet-, and hornblende-rich schists and/or gneisses) and acid plutonics (particularly granites and/or granitic gneisses). Basic intrusive rocks were minor contributors. Pre-existing sedimentary rocks and/or paragneisses were present as local sources.