Milankovitch paleoceanographic cycles in geophysical logs from ODP Leg 105, Labrador Sea and Baffin Bay

R. D. Jarrard, M. A. Arthur

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19 Scopus citations


Ocean Drilling Program Sites 645 and 646, in Baffin Bay and the Labrador Sea, respectively, were logged following drilling during Leg 105. The interval 288-455 mbsf of Site 645 was logged with sonic, resistivity, and gamma-ray tools. This zone corresponds to an estimated time interval of 1.9-3.1 Ma. These logs exhibit strong cyclicity throughout, which is mainly controlled by variations in porosity. The cycles most likely correspond to variations in flux of ice-rafted debris and/or to variations in activity of bottom currents. The patterns suggest waning influence of precession and increasing importance of obliquity as glaciation progressed in the Baffin Bay region. At Site 646, the openhole interval of 210-737 mbsf was logged with neutron, spectral-gamma-ray, gamma-spectroscopy, sonic, and resistivity tools. This interval corresponds in time to ~8.5-2.1 Ma. The variation is largely in porosity, which apparently is directly related to variations in clay content. The cycles, which are alternations between clay-rich and coarser-grained sediment, most likely reflect orbital control on changes in intensity of bottom currents. -from Authors

Original languageEnglish (US)
Pages (from-to)757-772
Number of pages16
JournalUnknown Journal
StatePublished - 1989

All Science Journal Classification (ASJC) codes

  • General Environmental Science
  • General Earth and Planetary Sciences


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