Expedition 385 Scientific Prospectus: Guaymas Basin Tectonics and Biosphere: feedbacks between continental rifting, magmatism, sedimentation, thermal alteration of organic matter, and microbial activity

Abstract

Expedition 385 is based on International Ocean Discovery Program (IODP) drilling Proposals 833-Full2 and 833-Add (available at http://iodp.tamu.edu/scienceops/expeditions/guay-mas_basin_tectonics_biosphere.html). Following ranking by the IODP scientific advisory structure, the expedition was scheduled for the research vessel (R/V) JOIDES Resolution, operating under contract with the JOIDES Resolution Science Operator (JRSO). At the time of publication of this Scientific Prospectus, the expedition is scheduled to start in San Diego, California (USA), on 16 September 2019 and to end in San Diego on 16 November 2019. Accounting for 5 days of port call and 9 days of transit, a total of 47 days will be available for the drilling, coring, and downhole measurements described in this report (for the current detailed schedule, see http://iodp.tamu.edu/scienceops). Further details about the facilities aboard JOIDES Resolution can be found at http://www.iodp.tamu.edu/publicinfo/drillship.html.

Sites U1547 and U1548

“…Physical properties data for Sites U1547 and U1548 are reported here, starting from the most distal holes to the center of the Ringvent structure (U1548D, U1548E, U1548A, U1548B, U1548C, U1547E, U1547D, U1547A, U1547C, and U1547B). Site U1548 can be regarded as a reference for Site U1547, where igneous bodies were identified in 2-D seismic images (Teske et al, 2018). Physical properties measured on whole-round and split core sections from Holes U1547A-U1547E and U1548A-U1548E were compared with each other and with downhole logging measurements from Hole U1547B for lithostratigraphic characterization and correlation between core description, logging data, and preexpedition seismic survey profiles.…”

“…Physical properties of recovered cores were measured on whole-round and working-and archivehalf sections in the core laboratory for all holes at Sites U1547 and U1548 (U1548A-U1548E and U1547A-U1547E) (see Tables T17 and T18 in the Expedition 385 methods chapter [Teske et al, 2021a]). Measurements from Site U1548 are used as a reference for Site U1547, where one or more underlying sills are thought to host a still-active seafloor hydrothermal system (Teske et al, 2018).…”

“…Holes that recovered igneous rock and depth/thickness distribution of igneous intervals, Sites U1547 and U1548. A. Southwest-northeast trending seismic cross section of the Ringvent structure showing positions of drilled holes (modified fromTeske et al, 2018). B.…”

Expedition 385 summary

“…The following three primary scientific objectives were outlined in the Expedition 385 Scientific Prospectus (Teske et al, 2018):…”

“…Site U1551 (proposed Site GUAYM-15A) is located ~29 km southeast of the axial graben of the northern Guaymas Basin spreading segment (Figures F1, F15). The type of sediment, the depositional environment, and the type, size, and, presumably, age of sill intrusions were all proposed to differ in the southeastern side of the spreading segment relative to the northwestern side (Teske et al, 2018). The sediment at Site U1551 was predicted to be predominantly terrigenous and deposited as gravity-driven flows ranging from landslides to turbidites, with the underlying sills appearing to be larger and more saucer-shaped than those in the northwest.…”