Site U1619. Proceedings of the International Ocean Discovery

10. Downhole measurements 10.1. Formation temperature During APC coring in Hole U1619A, in situ formation temperature was measured every third core (4H, 7H, 10H, and 13F) using the APCT-3 tool. After switching to XCB coring, in situ formation temperature was measured before Cores 29X and 45X using the SET2 probe. Temperature increased almost linearly with depth, and the slope of linear regression provides a typical geothermal gradient (87.5°C/km) for oceanic sediments compared with the statistical data set (Kolawole and Evenick, 2023) (Figure F36). For Hole U1619A, the heat flow in the sediments and the temperature at the seafloor were calculated using the measured thermal conductivity in Cores 1H– 84X (see Physical properties) and the formation temperature measurements. Assuming a linear relationship between thermal conductivity and depth, the heat flow in the sediments and the temperature at the seafloor are approximately 112.9 mW/m2 and −1.23°C, respectively. 10.2. Downhole logging At Site U1619, planned downhole logging runs using the triple combination and Formation MicroScanner (FMS)-sonic tool strings were canceled because the marginal ice zone was approaching the site, which rendered it impossible to fully drill and log.