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PALEOCEANOGRAPHY, VOL. 22, PA4213, doi:10.1029/2006PA001401, 2007

Automated composite depth scale construction and estimates of sediment core extension

Lorraine E. Lisiecki

Department of Earth Sciences, Boston University, Boston, Massachusetts, USA


Timothy D. Herbert

Department of Geological Sciences, Brown University, Providence, Rhode Island, USA


Abstract

A composite section, which reconstructs a continuous stratigraphic record from cores of multiple nearby holes, and its associated composite depth scale are important tools for analyzing sediment recovered from a drilling site. However, the standard technique for creating composite depth scales on drilling cruises does not correct for depth distortion within each core. Additionally, the splicing technique used to create composite sections often results in a 10–15% offset between composite depths and measured drill depths. We present a new automated compositing technique that better aligns stratigraphy across holes, corrects depth offsets, and could be performed aboard ship. By analyzing 618 cores from seven Ocean Drilling Program (ODP) sites, we estimate that ∼80% of the depth offset in traditional composite depth scales results from core extension during drilling and extraction. Average rates of extension are 12.4 ± 1.5% for calcareous and siliceous cores from ODP Leg 138 and 8.1 ± 1.1% for calcareous and clay-rich cores from ODP Leg 154. Also, average extension decreases as a function of depth in the sediment column, suggesting that elastic rebound is not the dominant extension mechanism.

Received 29 November 2006; accepted 20 August 2007; published 15 December 2007.

Keywords: composite depth scales; ocean drilling; sediment core deformation.

Index Terms: 4994 Paleoceanography: Instruments and techniques; 3036 Marine Geology and Geophysics: Ocean drilling; 3022 Marine Geology and Geophysics: Marine sediments: processes and transport; 4999 Paleoceanography: General or miscellaneous.

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Citation: Lisiecki, L. E., and T. D. Herbert (2007), Automated composite depth scale construction and estimates of sediment core extension, Paleoceanography, 22, PA4213, doi:10.1029/2006PA001401.