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doi:10.2204/iodp.proc.342.202.2017

Introduction

Integrated Ocean Drilling Program (IODP) Expedition 342, “Paleogene Newfoundland Sediment Drifts,” was completed during June and July 2012 and recovered a total of ~5.4 km of predominantly Paleogene clay-rich sediments (see the “Expedition 342 summary” and “Methods” chapters [Norris et al., 2014a, 2014b]). The nine sites drilled on the J-Anomaly and Newfoundland Ridges span a depth transect from ~4.9 km (Site U1403) to ~3.0 km water depth (Site U1408). The sites at the J-Anomaly Ridge (Sites U1403–U1406) recovered expanded records (up to 25 cm/ky at Site U1405) of late Paleogene to early Neogene age.

Site U1406 (40°21′N, 51°39′W; Fig. F1) is located in the middle of the Expedition 342 depth transect at 3.8 km present-day water depth. A comprehensive recognition and characterization of climatic events recorded at Site U1406 requires a continuous and undisturbed sequence. A single IODP hole inevitably yields discontinuous geological records because of stratigraphic gaps between successive cores. Recovered cores from a single hole may also contain disturbed intervals. Drilling of multiple closely spaced holes is therefore crucial to ensure complete recovery for the construction of a continuous composite record or “splice” (e.g., Ruddiman et al., 1987; Hagelberg et al., 1992; Westerhold et al., 2012). Correlating stratigraphic information from multiple holes also helps identifying hiatuses and condensed or expanded intervals because such stratigraphically complex intervals may only occur in a subset of holes. Once a composite record has been constructed, additional scaling (“stretching and squeezing”) is typically required to correlate off-splice intervals to the composite record in the depth domain (e.g., Hagelberg et al., 1995; Westerhold et al., 2012).

The modest variability of the physical properties data (i.e., magnetic susceptibility, gamma ray attenuation [GRA], and natural gamma radiation [NGR]) from the clay-rich drift sediments at Site U1406 challenged the construction of a reliable shipboard splice (see the "Site U1406" chapter [Norris et al., 2014c]). Postexpedition high-resolution X-ray fluorescence (XRF) core scanning, however, has made it possible to construct a decimeter-scale composite depth scale and near-continuous spliced record. This initial depth scale, hereinafter referred to as the “shipboard splice,” was generated using a subset of the postexpedition XRF data. In this report, we present an updated composite depth scale and revised splice for Site U1406 developed after reassessing the available XRF data, aided by newly generated XRF core scanning data. We also present detailed (i.e., decimeter-scale) correlations to the revised splice for core intervals that lie outside the revised splice.

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