Distal Glacial-Marine Sedimentation: Abundance, Composition, and Distribution of North Atlantic Ocean Pleistocene Ice-Rafted Sediment

  • Bruce F. Molnia
Chapter

Abstract

During the Pleistocene, as much as 40% of the sediment deposited in the North Atlantic Ocean was transported to its site of deposition by ice-rafting. Examination of sediment samples from eight eastern North Atlantic Ocean piston cores, collected by USNS Kane and selected thin sections from an additional 32 Lamont Doherty North Atlantic Ocean piston cores, indicates that North Atlantic Ocean ice-rafted sediment is composed predominantly of fine-grained material. About one-quarter of the ice-rafted sediment is sand-size and coarser. The sand-sized fraction contains quartz, feldspar, and rock fragments, with minor amounts of hornblende, olivine, garnet, mica, chlorite, pyroxene, epidote, and apatite.

By weight and volume, the ice-rafted pebble component represents 1% of the total ice-rafted sediment. Surprisingly, more than 400 pebbles were recovered from the eight Kane cores. Analyses of ice-rafted pebbles show that fine grained basalts are the most abundant pebble-sized rock type in the eastern North Atlantic, while clastic sedimentary rocks are most abundant in the western North Atlantic. Iceland, Jan Mayen, the Faroe Islands, and Spitsbergen, all glacier-covered during the Pleistocene, are the most probable source areas for eastern North Atlantic basalts, while North American Triassic basins are the probable source areas for sandstone, the dominant western North Atlantic Ocean clastic sedimentary rock component.

Assuming the quantity of ice-rafted sediment contained in the Kane cores is typical of the-entire eastern North Atlantic Ocean, then about 7.6 × 1019 g of glacially-eroded sediment was ice-rafted into the eastern North Atlantic Ocean from Europe, Iceland, the Faroe Islands, Jan Mayen, Spitsbergen, and Greenland during the past 1.2 m. y. Based on Flint’s (1971) calculated glacial erosion rate of 70 cm/1000 yr, this ice-rafted detrital input represents <5% of the total volume of sediment eroded by glacial processes.

As many as 18 periods of increased ice-rafting (the >500 μm fraction ≥2% of total sample) have occurred during the last 300,000 yr. However, for the Kane cores, the coarse pebble fraction comprises <1% of total sediment. The dominant ice-rafted component is the silt and clay fraction, which averages 77.2% of all sediment. The >500 μm fraction represents 2.9% of the total sediment.

Keywords

North Atlantic Ocean Faroe Island Piston Core Clastic Sedimentary Rock Western North Atlantic Ocean 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Plenum Press, New York 1983

Authors and Affiliations

  • Bruce F. Molnia
    • 1
  1. 1.Marine Environmental Science Associates, Inc.NorthridgeUSA

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