Ar ages and 40 Ar ) concentrations of fine - grained sediment fractions from North Atlantic Heinrich layers

نویسندگان

  • S. R. Hemming
  • C. M. Hall
  • P. E. Biscaye
  • S. M. Higgins
  • G. C. Bond
  • J. F. McManus
  • D. C. Barber
  • J. T. Andrews
  • W. S. Broecker
چکیده

New KrAr ages based on ArrAr incremental heating of -2and 2–20-mm size fractions of the well-characterized, carbonate-bearing Heinrich layers of core V28-82 in the eastern North Atlantic are 846–1049 Ma, overlapping with conventional KrAr ages from the same Heinrich layers on the Dreizack seamounts of 844–1074 Ma. This agreement suggests the equivalence of the methods in fine-grained terrigenous sediments. Additionally, Heinrich layer H2 yielded a ArrAr-based KrAr age of 970"4 from Orphan Knoll in the southern Labrador Sea, within the range found in eastern North Atlantic Heinrich layers. Thus, the KrAr data are robust in their indication of a dominant Labrador Sea ice-rafted source to even the finest sediment fraction in the eastern North Atlantic during the massive detrital carbonate-bearing Ž . Heinrich events of the last glacial cycle H1, H2, H4, H5 . Close correspondence of the radiogenic argon concentration Ž ) . Ar from the de-carbonated -63-mm fractions from V28-82 with the -2and 2–16-mm fractions from the Driezack seamounts demonstrates that this measurement is a rapid and reliable method for correlating these layers within their belt of distribution. A ArrAr-based KrAr age of 433"5 million years for H11 in V28-82 is within the range of published data from background sediments in the eastern North Atlantic, and is consistent with published results across this interval in the Driezack seamounts. In contrast, the ArrAr-based KrAr age of H11 in the western Atlantic core EW9303-JPC37 is 614"5 million years. A brick red sample from approximately the interval of H3 of core EW9303-GGC40 yielded a ArrAr-based KrAr age of 567"1 million years, comparable to the published range of 523–543 Ma from the 2–16-mm fractions from that interval on the Dreizack seamounts. Both JPC37 and GGC40 are located in the path of the North Atlantic Drift. The older ages from western samples of H3 and H11 may result from dilution of a Hudson Strait source or an elevated age from southeastern Laurentide sources. q 2002 Elsevier Science B.V. All rights reserved.

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تاریخ انتشار 2002