Expedition 397 Scientific Prospectus: Iberian Margin Paleoclimate

Abstract

Portions of this work may have been published in whole or in part in other IODP documents or publications.This IODP Scientific Prospectus is based on precruise JOIDES Resolution Facility advisory panel discussions and scientific input from the designated Co-Chief Scientists on behalf of the drilling proponents. During the course of the cruise, actual site operations may indicate to the Co-Chief Scientists, the Expedition Project Manager/Staff Scientist, and the Operations Superintendent that it would be scientifically or operationally advantageous to amend the plan detailed in this prospectus. It should be understood that any substantial changes to the science deliverables outlined in the plan presented here are contingent upon the approval of the IODP JRSO Director and/or JOIDES Resolution Facility Board.

A 1.5-Million-Year Record of Orbital and Millennial Climate Variability in the North Atlantic

“…In addition to documenting MCV, the planktic and benthic isotope records from Site U1385 provide unprecedented detail of the amplitude and shapes (waveforms) of the glacial cycles on orbital time scales for the last 1.45 Ma. We emphasize our record is from a single site and should be compared with other records from higher latitude in the North Atlantic (e.g., Barker et al, , 2022 and elsewhere in order to map geographical differences Expedition 397 is to return to the Iberian margin and extend the U1385 record to study how orbital and millennial variability co-evolved during through the Quaternary and Pliocene (Hodell et al, 2022). Understanding these interactions of climate on orbital and suborbital time scales will lead to a fuller understanding of the mechanisms responsible for the Quaternary ice ages.…”

Site U1385

“…CaCO 3 is relatively constant in the uppermost ~200 m (mean = 33.3 ± 8.35 wt%), and then increases below ~250 m CSF-A (Figures F34, F35; Table T23). CaCO 3 correlates positively with L* reflectance (adjusted R 2 = 0.474) and negatively with NGR (adjusted R 2 = 0.615) (Figures F35, F36; see Figures F27, F28, F29, and F31 in the Site U1587 chapter [Hodell et al, 2024]). The uppermost ~25 m shows more scatter in the crossplot with NGR; below this depth the regression is slightly strengthened (adjusted R 2 = 0.721) (Figure F37).…”

Expedition 397 methods

“…Because of the significant curvature in the relationship between the CCSF-A and CSF-A depth scales, polynomial fits were required to achieve a good relationship that ran through the zero depth (mudline) at the top of each site. The fits are presented in each site chapter (see Figures F50 in the Site U1385 chapter [Hodell et al, 2024a], F60 in the Site U1586…”

“…chapter , F47 in the Site U1587 chapter [Hodell et al, 2024b], and F39 in the Site U1588 chapter [Abrantes et al, 2024b]). The CCSF-A* depth scale is used in stratigraphic summary Figures F48 in the Site U1385 chapter (Hodell et al, 2024a) and F55 in the Site U1586 chapter because it represents the closest match of the spliced sequences to data presented elsewhere in the CSF-A depth scale. In the case of Site U1588, severe gas expansion required us to build a composite based on the CSF-B, convention, whereby core thickness is compressed to 100% recovery.…”

“…The core composite depth below seafloor, Method B (CCSF-B), is then corrected to approximate driller's depth on the CCSF-B* scale. Tables for conversion of CCSF-A depths to the CCSF-A* depth scale are given in Tables T32 in the Site U1385 chapter (Hodell et al, 2024a), T32 in the Site U1586 chapter , and T32 in the Site U1587 chapter (Hodell et al, 2024b).…”