Labrador shelf benthic Foraminifera and stable oxygen isotopes of Cibicides lobatulus related to the Labrador Current

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Vilks, G., Deonarine, B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1988
• Subjects: General Earth and Planetary Sciences; Labrador Shelf; Subarctic
• Online Access: http://dx.doi.org/10.1139/e88-120; http://www.nrcresearchpress.com/doi/pdf/10.1139/e88-120

Foraminifera from 38 samples of surface sediments contained 22 calcareous and 17 agglutinated species. Eight stenotopic species relate to different waters of the Labrador Current: Cassidulina reniforme, Reophax arctica, and Cribrostomoides crassimargo are associated with the inner shelf–estuarine environment; Islandiella helenae and Haynessina orbiculare are associated with the cold and diluted inner shelf waters; Buccella frigida is related to the slope waters; and Melonis zaandamae is related to the deep waters of the basins and the outer Labrador Shelf. The distribution of these species down core in core 13, collected from one of the basins on the Labrador Shelf, indicates the presence of inshore waters in the bottom of the basin about 15 000 years BP.The ratios of the two stable oxygen isotopes 18 O and 16 O were determined in the tests of Cibicides lobatulus from surface sediment samples collected at 28 localities on the Labrador Shelf. The range of bottom salinities at station locations was 28.6 to 34.8‰, and the corresponding range in bottom temperatures was 4 to −1.5 °C. The range in δ 18 O measured in the tests of C. lobatulus was −0.5 to 2.4‰. The significance of the linear regression between salinity and δ 18 O is better than a 99.9% level of probability.The down-core δ 18 O profile and the proportion of estuarine species in core 13 show a trend that corresponds to lower paleosalinities on the Labrador Shelf. The δ 18 O values become more negative, approaching the mean value of the present-day inshore waters, and the total assemblage of Foraminifera also changes towards a greater proportion of estuarine species. The paleoceanographic boundary is estimated to be slightly younger than 15 000 years BP, according to extrapolation of dated lithologic and faunal boundaries from nearby cores.We demonstrate that the stable oxygen isotope ratios from tests of the epibenthic foraminifer Cibicides lobatulus are useful in establishing paleosalinities on a subarctic continental shelf, where waters have been ...