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doi:10.2204/iodp.proc.340.202.2015

Introduction

A major objective of Integrated Ocean drilling Program (IODP) Expedition 340 Site U1396 was to utilize the marine record to characterize the eruptive history of Montserrat. Three holes were cored at the site with the advanced piston corer (APC) system; two of them were quasicontinuous 140.5 m (Hole U1396A) and 145.9 m (Hole U1396C) records, whereas Hole U1396B was a single 10 m core (340-U1396B-2H) taken to replicate a disturbed interval (Core 340-U1396A-2H) in Hole U1396A. Shipboard-derived biostratigraphic and paleomagnetic data sets revealed that the sediment and intercalated tephra record at Site U1396 date back ~4.5 My to the early Pliocene (see the “Site U1396” chapter [Expedition 340 Scientists, 2013]). As subaerial radiometric ages place the origin of Montserrat around 2.5 Ma (Harford et al., 2002) Site U1396 is an important sedimentary sequence potentially capable of addressing fundamental questions about the evolution of the Lesser Antilles volcanic arc.

Many of the scientific objectives for Site U1396 required recovery of a continuous and complete stratigraphic section. Continuous sedimentary sections cannot be recovered from a single borehole because gaps in recovery occur between successive cores. Furthermore, Core 340-U1396A-2H suffered a shattered liner, and two 10 cm whole-round (WR) samples were taken from every core in Hole U1396C, resulting in irregular gaps in records from individual holes. A continuous complete section can be constructed by combining intervals from all three holes to bridge gaps and replace disturbed intervals. This can be achieved by (1) correlating physical property data to identify coeval horizons between cores, which may be substantially offset in depth, and (2) mapping individual holes onto a common depth scale that allows the generation of a spliced record and development of a complete stratigraphic section. Shipboard correlation of the three holes from Site U1396 was accomplished using Analyseries (Paillard et al., 1996) (see the “Site U1396” chapter [Expedition 340 Scientists, 2013]). However, this methodology linearly interpolated data between assigned tie points, artificially “stretching” and “squeezing” the sequence, which may not reflect sediment deposition processes. This methodology also retained the core depth below seafloor (CSF-A) depth scale (e.g., Manga et al., 2012; Jutzeler et al., 2014; Wall-Palmer et al., 2014), which is subject to numerous errors and inaccuracies. Here, I outline the methodology used for correlating Holes U1396A–U1396C and develop a composite depth scale and splice for Site U1396.

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