Data report: revised composite depth scales for Sites U1336, U1337, and U1338: Expedition 320/321

Abstract

The eastern equatorial Pacific (EEP) is one of the most dynamic regions of the open ocean. To fully appreciate the history of this area in the time domain, correlative and complete sedimentary records are required from multiple drill sites. One essential step for each site is the construction of an accurate composite depth scale, whereby selected intervals of successive cores from proximal holes are spliced together to render a full stratigraphic section. Here, we generate revised composite depth scales for Integrated Ocean Drilling Program (IODP) Sites U1336, U1337, and U1338, recovered during IODP Expeditions 320 and 321. Composite sections were generated using physical properties data overlain on high-resolution scanned images of adjacent core sections from all holes cored at a site. Coring disturbance, particularly deeper in the holes, prevented composite construction to total depth at each site. At Site U1336, utilizing two holes, the composite record reaches almost 135 m core composite depth below seafloor (CCSF). At Site U1337, with four holes, a depth of close to 450 m CCSF was reached with only three gaps. Using the three holes of Site U1338, a composite section of almost 400 m CCSF was developed with only two breaks. Composite depth records are crucial for working on these sites because sediment composition varies considerably over short (<30 cm) depth intervals. The composite gamma ray attenuation density records will be particularly important to a range of studies in the region because they can be coupled to those collected at earlier drill sites in the EEP.