Spatial and temporal variability of late Neogene Equatorial Pacific carbonate : ODP Leg 138 Public Deposited

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  • High resolution, continuous records of GRAPE wet bulk density (a carbonate proxy) from Ocean Drilling Program Leg 138 provide one the opportunity for a detailed study of eastern equatorial Pacific Ocean carbonate sedimentation during the last 6 m.y. The transect of sites drilled spans both latitude and longitude in the eastern equatorial Pacific from 90° to 110°W and from 5°S to 10°N. Two modes of variability are resolved through the use of Empirical Orthogonal Function (EOF) analysis. In the presence of large tectonic and climatic boundary condition changes over the last 6 m.y., the dominant mode of spatial variability in carbonate sedimentation is remarkably constant. The first mode accounts for over 50% of the variance in the data, and is consistent with forcing by equatorial divergence. This mode characterizes both carbonate concentration and carbonate mass accumulation rate time series. Variability in the first mode is highly coherent with insolation, indicating a strong linear relationship between equatorial Pacific car bonate sedimentation and Milankovitch variability. Frequency domain analysis indicates that the coupling to equatorial divergence in carbonate sedimentation is strongest in the precession band (19 23 k.y.) and weakest though present at lower frequencies. The second mode of variability has a consistent spatial pattern of east west asymmetry over the past 4 m.y. only; prior to 4 Ma, a different mode of spatial variability may have been present, possibly suggesting influence by closure of the Isthmus of Panama or other tectonic changes. The second mode of variability may indicate influence by CaCO₃ dissolution. The second mode of variability is not highly coherent with insolation. Comparison of the modes of carbonate variability to a 4 m.y. record of benthic δ¹⁸O indicates that although overall correlation between carbonate and δ¹⁸O is low, both modes of variability in carbonate sedimentation are coherent with δ¹⁸O changes at some frequencies. The first mode of carbonate variability is coherent with Sites 846/849 δ¹⁸O at the dominant insolation periods, and the second mode is coherent at 100 k.y. during the last 2 m.y. The coherence between carbonate sedimentation and δ¹⁸O in both EOF modes suggests that multiple uncorrelated modes of variability operated within the climate system during the late Neogene.
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  • Hagelberg, T., N.G. Pisias, L.A. Mayer, N.J. Shackleton, A.C. Mix (1995) Spatial and temporal variability of late Neogene Equatorial Pacific carbonate: ODP Leg 138. In: Pisias, N.G., L. Mayer, T. Janecek, A. Palmer-Julson, T.H. van Andel (eds.), /Proceedings of the Ocean Drilling Program, Scientific Results,/ 138, College Station, TX (Ocean Drilling Program), 321-336.
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  • description.provenance : Made available in DSpace on 2009-12-16T15:32:18Z (GMT). No. of bitstreams: 1 HagelbergEtAl1995_Leg138_VariabilityCarbonate.pdf: 5157765 bytes, checksum: 53968ca936a0fab0a8ebd89729be3502 (MD5) Previous issue date: 1995
  • description.provenance : Approved for entry into archive by Linda Kathman(linda.kathman@oregonstate.edu) on 2009-12-16T15:32:18Z (GMT) No. of bitstreams: 1 HagelbergEtAl1995_Leg138_VariabilityCarbonate.pdf: 5157765 bytes, checksum: 53968ca936a0fab0a8ebd89729be3502 (MD5)
  • description.provenance : Submitted by Mary Phan (mpscanner@gmail.com) on 2009-12-15T20:14:17Z No. of bitstreams: 1 HagelbergEtAl1995_Leg138_VariabilityCarbonate.pdf: 5157765 bytes, checksum: 53968ca936a0fab0a8ebd89729be3502 (MD5)

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