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IODP Expedition 397

Iberian Margin Paleoclimate


Daily Science Report for 2 December 2022

Location: Hole U1588B (37°57.6149′N, 9°30.9956′W; water depth 1339.3 mbsl; proposed Site SHACK-10B)

Science Update: Coring in Hole U1588A was ended after retrieving Core 49X from 353.0 mbsf at 0045 h. The total core recovered from Hole U1588A is 378.37 m (107%). The drill pipe and the bit were raised above the seafloor and the vessel moved 20 m north. After picking up the top drive and positioning the bit at 1347 mbrf, Hole U1588B was spudded at 0445 h. Based on the amount of material retrieved in the mudline core (5.8 m), the seafloor was calculated to be 1339.3 mbsl, the same as for Hole U1588A. APC coring continued, cutting Cores U1588B-2H through 9H from 5.8 to 81.8 mbsf and recovering 80.06 m (105%). The XCB system was deployed with Core U1588B-10X and the hole was extended to 162.5 mbsf using half advances to allow for core expansion within the liners. At 2130 h, coring was paused for routine maintenance and 500 m from the aft core winch line were cut. Coring resumed at 2245 h, and Core U1588B-27X was retrieved from 167.3 mbsf before the end of the day. Total core recovered with the XCB system today was 126.19 m, with recovery ranging from 124% to 167% (average 148%).

Cores U1588A-25X through 49X and Cores U1588B-1H and 2H were split and described. They consist of clayey nannofossil ooze and nannofossil ooze. Foraminifera, mollusk shells, and shell fragments are disseminated throughout. Bioturbation is light to moderate, and evidence of trace fossils, including Thalassinoides, Planolites, and Zoophycos is observed. Several cores are slightly to strongly affected by gas expansion. Biostratigraphic markers provide an age between 1.92 and 2.3 Ma at the base of Core U1588A-48X.

The scientific team continues to analyze samples and data from Site U1588 and to work on the reports for Site U1385.


Daily Science Report for 1 December 2022

Location: Hole U1588A (37°57.6044′N, 9°30.9961′W; water depth 1339.3 mbsl; proposed Site SHACK-10B)

Science Update: We continued APC coring in Hole U1588A, retrieving Cores U1588A-14H through 17H from 116.2 to 154.2 mbsf by 0305 h. A partial stroke registered with Core U1588A-17H indicated we had reached APC refusal. Then we deployed the XCB system and retrieved Cores U1588A-18X to 48X before by midnight. Owing to significant gas expansion of the sediment, we changed to cutting half-length XCB cores beginning with Core 25X, to allow for the core to expand more cleanly inside the liner. In total, 159.14 m (103%) of core was retrieved with the APC system and 213.2 m (110%) was retrieved with the XCB system. For the half-length XCB cores, recovery ranged from 93% to 143% and averaged 123%.

Cores U1588A-7H through 24X were split and described. They consist of clayey nannofossil ooze and nannofossil ooze. Contacts between lithologies are bioturbated, irregular, and gradational. Foraminifera and small carbonate sand, mollusk shells, and shell fragments are disseminated throughout. Bioturbation is light to moderate, and evidence of trace fossils including Thalassinoides, Planolites, and Zoophycos is observed. Several cores are slightly to strongly affected by gas expansion. Biostratigraphic markers provide an age between 0.91 and 0.97 Ma at the base of Core U1588A-19X.

We held the Site U1385 summary meeting and presented the scientific results from each laboratory team. We then continued to analyze samples and data from Site U1588 and to work on the reports for Site U1385.