Sediment records from deep-drilling projects such as those carried out by the International Continental Scientific Drilling Program are often tens to hundreds of meters in length. To ensure the complete recovery of a stratigraphic section, a basin is usually cored multiple times in adjacent holes so that gaps between sequential cores, poorly recovered sections, or intervals affected by disturbance can be bridged or replaced with sediments from another hole. Stratigraphic correlation, the alignment of stratigraphically-equivalent horizons in cores from different holes in a common-depth scale, and splice generation, the integration of the most-representative core sections into a composite-stratigraphic section, are essential steps in this process to both evaluate and synthesize the recovered-sediment record and focus the scientific analyses. However, these undertakings can be complex and are inherently subjective, making the need for the development of a single robust stratigraphic section early in the project critical to its success. Despite this, the steps between core recovery and on-splice data generation are rarely published in sufficient detail to allow reconstruction, or refinement, of the composited record at a later date. To increase the transparency of how the composite record is created, and to provide a template for future projects, we detail the step-by-step approaches and decisions involved in generating the composite-depth scale and complete-stratigraphic splice following recovery of sediments from Lake Junín, Peru. We first explain the details and nuances of different drilling-depth scales before describing how we integrated different physical property records to generate the composite-depth scale and complete-stratigraphic splice. Here, we show that due to the complex stratigraphy in the Lake Junín sediments, high-resolution line-scan images of the cores offer millimeter-scale precision for construction of the primary-stratigraphic splice at a resolution not afforded by other physical property data. Finally, through comparison of the spliced record to physical-property records acquired in situ on the borehole, we demonstrate that the stratigraphic splice is an accurate representation of the sediment accumulated in the Lake Junín basin.
Bibliographical noteFunding Information:
This research was carried out with support from the U.S. National Science Foundation awards EAR-1400903 (Stoner), EAR-1404113 (Abbott), and EAR-1402076 (Rodbell) and was co-funded by the ICDP, which in the US is operated out of the Continental Scientific Drilling Coordination Office (CSDCO) at the University of Minnesota. The Lake Junín Project would not have been possible without the team of drillers from DOESECC Exploration Services (USA), GEOTEC (Peru), and the expertise of Doug Schnurrenberger, Kristina Brady Shannon, and Mark Shapley of CSDCO. Logistical assistance was provided by Bryan Valencia, Angela Rozas-Davila, James Bartle, and Cecilia Oballe. RGH would like to thank Brian Grivna at the CSDCO for assistance with integrating the manually offset cores into LacCore-hosted software.
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- Depth scale
- Lake Junín
- Sediment cores
- Stratigraphic correlation
Continental Scientific Drilling Facility tags