Oversampling of sedimentary series collected by giant piston corer: Evidence and corrections based on 3.5-kHz chirp profiles

Type Article
Date 2004-01
Language English
Author(s) Szeremeta N1, Bassinot F2, Balut Y3, Labeyrie L1, Pagel M1
Affiliation(s) 1 : Univ Paris 11, Dept Sci Terre, UMR CNRS UPS Orsay Terre 8616, F-91405 Orsay, France.
2 : CNRS, CEA, LSCE Orme, Lab Mixte, F-91191 Gif Sur Yvette, France.
3 : Inst Polaire Francais Paul Emile Victor, F-29280 Plouzane, France.
Source Paleoceanography (0883-8305) (Amer Geophysical Union), 2004-01 , Vol. 19 , N. PA1005 , P. 1-8
DOI 10.1029/2002PA000795
WOS© Times Cited 49
Keyword(s) correction of coring-induced sediment oversampling, giant piston coring, IMAGES cores, North Atlantic
Abstract The depth-scale accuracy of marine sedimentary series collected by coring is of key importance for the precise calculation of sedimentation rates and fluxes. For three giant piston cores collected during the InterPole MD99-114/International Marine Past Global Changes Study (IMAGES) V cruise (MD99-2227, MD99-2246, and MD99-2251), the 3.5-kHz chirp profiles recorded on board are compared to synthetic seismograms computed from physical property logs measured on cores. In each case, the perfect match of main deep reflectors requires a significant upward shift of the water-sediment (W/S) interface in the synthetic seismograms with respect to the 3.5-kHz profiles. Since no drastic perturbation of the physical property logs is observed, this upward shift is interpreted as resulting from a significant sediment oversampling in the upper part of the cores. The affected depth intervals are consistent with the thickness of the perturbed zones observed in penetrometry and anisotropy of magnetic susceptibility records (similar to10-15 m). To retrieve the true in situ sediment thickness, a linear depth correction is applied between consecutive acoustic reflectors to achieve a perfect match between the synthetic seismogram and the corresponding 3.5-kHz profiles. Depth correction laws ( amount of material excess as a function of initial depth) are deduced from this resynchronization procedure. First estimations of upper core oversampling rates range from 30% (core MD99-2227) to 37% (core MD99-2246). Moreover, we observe that some undersampling may also exist in the lower part of the sediment cores.
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