skip to main content

This content will become publicly available on May 1, 2023

Title: Expedition 390/393 Scientific Prospectus Addendum: South Atlantic Transect
The South Atlantic Transect (SAT) is a multidisciplinary scientific ocean drilling project that will recover complete sedimentary sections and the upper ~250 m of the underlying oceanic crust along a slow/intermediate spreading rate Mid-Atlantic Ridge crustal flow line at ~31°S. These cores were originally scheduled to be collected during International Ocean Discovery Program (IODP) Expeditions 390 and 393 in October–December 2020 and April–June 2021, respectively. In 2020 and 2021, the global COVID-19 pandemic resulted in the postponement of several IODP expeditions, including Expeditions 390 and 393, chiefly because science parties were unable to travel to the R/V JOIDES Resolution. In response, the ship was used to conduct preparatory work for the postponed expeditions that did not require a science party aboard but could be carried out by the ship’s crew and a team of technicians from the JOIDES Resolution Science Operator. Two of these expeditions (390C and 395E) were in service of the SAT drilling project, to reduce the operational risks and expedite basement drilling during the rescheduled Expeditions 390 and 393. Expeditions 390C and 395E visited five of the six primary SAT sites and successfully cored a single advanced piston corer/extended core barrel hole penetrating the entire sediment section more » and <10 m into the underlying basalt before installing a reentry system in a second hole at each site visited. Given these accomplishments, the operations plans for the rescheduled Expeditions 390 and 393 have been revised. « less
Authors:
; ; ; ; ; ;
Award ID(s):
1326927
Publication Date:
NSF-PAR ID:
10327929
Journal Name:
Scientific prospectus
Volume:
390/393
ISSN:
2332-1385
Sponsoring Org:
National Science Foundation
More Like this
  1. The South Atlantic Transect (SAT) is a multidisciplinary scientific ocean drilling project that comprises two International Ocean Discovery Program (IODP) expeditions (390, October–December 2020, and 393, April–June 2021). These expeditions will recover complete sedimentary sections and the upper ~250 m of the underlying oceanic crust along a slow/intermediate spreading rate Mid-Atlantic Ridge crustal flow line at ~31°S. The sediments along this transect were originally spot cored more than 50 y ago during Deep Sea Drilling Project Leg 3 to help verify the theories of seafloor spreading and plate tectonics. Given dramatic advances in drilling technology and analytical capabilities since Legmore »3, many high-priority scientific objectives can be addressed by revisiting the transect. The SAT expeditions will target six primary sites on 7, 15, 31, 49, and 61 Ma ocean crust, which will fill critical gaps in our sampling of intact in situ ocean crust with regards to crustal age, spreading rate, and sediment thickness. These sections are required to investigate the history of the low-temperature hydrothermal interactions between the aging ocean crust and the evolving South Atlantic Ocean and quantify past hydrothermal contributions to global geochemical cycles. The transect traverses the previously unexplored sediment- and basalt-hosted deep biosphere beneath the South Atlantic Gyre from which samples are essential to refine global biomass estimates and investigate microbial ecosystems’ responses to variable conditions in a low-energy gyre and aging ocean crust. The drilling operations will include installation of reentry cones and casing to establish legacy boreholes for future basement hydrothermal and microbiological experiments. The transect is also located near World Ocean Circulation Experiment Line A10, providing access to records of carbonate chemistry and deepwater mass properties across the western South Atlantic through key Cenozoic intervals of elevated atmospheric CO2 and rapid climate change. Reconstruction of the history of the deep western boundary current and deepwater formation in the Atlantic basins will yield crucial data to test hypotheses regarding the role of evolving thermohaline circulation patterns in climate change and the effects of tectonic gateways and climate on ocean acidification.« less
  2. International Ocean Discovery Program (IODP) Expeditions 390C and 395E were implemented in response to the global COVID-19 pandemic and occupied sites proposed for the postponed Expeditions 390 and 393, South Atlantic Transect 1 and 2. Expedition 395E completed most of the preparatory work that Expedition 390C did not have time to complete. The overall objective of Expeditions 390C and 395E was to core one hole at each of the South Atlantic Transect sites with the advanced piston corer/extended core barrel (APC/XCB) system to basement for gas safety monitoring and to install a reentry system with casing through the sediment tomore »a few meters into basement in a second hole. Expedition 395E started in Cape Town, South Africa, and ended in Reykjavík, Iceland, after 20 days of on-site operations. We cored to basement at two new sites, U1560 and U1561, and completed reentry systems at three sites, U1556, U1557, and U1560. These operations will expedite basement drilling during the rescheduled Expeditions 390 and 393. Hole U1560A (Proposed Site SATL-25A) lies in ~15.2 Ma crust and is composed of carbonate-rich sediments to 120 meters below seafloor (mbsf) and 2.5 m of underlying basalt. A reentry system was deployed in Hole U1560B to 122.0 mbsf. We then moved to the sites at the western end of the transect on ~61 Ma crust. In Hole U1557D, 10¾ inch casing was deployed to 571.6 mbsf to deepen the 16 inch casing that was deployed during Expedition 390C, and in Hole U1556B, a reentry system was deployed to 284.2 mbsf. The remaining operations time was insufficient to install a reentry system at the originally planned site, Proposed Site SATL-33B. Instead, we cored Hole U1561A (Proposed Site SATL-55A) to 47 mbsf. It is composed of red clay and carbonate ooze overlying 3 m of basalt. The six primary sites of the South Atlantic Transect lie perpendicular to the Mid-Atlantic Ridge on the South American plate, overlying crust ranging in age from 7 to 61 Ma. Basement coring will increase our understanding of how crustal alteration progresses over time across the flanks of a slow/intermediate-spreading ridge and how microorganisms survive in deep subsurface environments. Sediment will be used in paleoceanographic and microbiological studies.« less
  3. The objective of International Ocean Discovery Program (IODP) Expedition 384 was to carry out engineering tests with the goal of improving the chances of success in deep (>1 km) drilling and coring in igneous ocean crust. A wide range of tools and technologies for potential testing were proposed by the Deep Crustal Drilling Engineering Working Group in 2017 based on reports from recent crustal drilling expeditions. The JOIDES Resolution Facility Board further prioritized the testing opportunities in 2018. The top priority of all recommendations was an evaluation of drilling and coring bits because rate of penetration and bit wear andmore »tear are the prevalent issue in deep crustal drilling attempts, and bit failures often require an excessive amount of fishing and hole cleaning time. The plan included drilling in basalt with three different types of drill bits: a tungsten carbide insert (TCI) tricone bit, a polycrystalline diamond compact (PDC) bit, and a more novel TCI/PDC hybrid bit. In addition, a TCI bit was to be paired with an underreamer with expanding cutter blocks instead of extending arms. Finally, a type of rotary core barrel (RCB) PDC coring bit that was acquired for the R/V JOIDES Resolution several years ago but never deployed would also be given a test run. A second objective was added when additional operating time became available for Expedition 384 as a result of the latest schedule changes. This objective included the assessment and potential improvement of current procedures for advanced piston corer (APC) core orientation. Expedition 384 began in Kristiansand, Norway, on 20 July 2020. The location for tests was based on various factors, including the JOIDES Resolution's location at the time, our inability to obtain territorial clearance in a short period of time, and a suitable combination of sediment and igneous rock for the drilling and coring operations. IODP Expedition 395, which was postponed due to the COVID-19 pandemic, had proposed sites that were suitable for our testing and offered the opportunity to carry out some serendipitous sampling, logging, and casing work for science. We first spent 3 days triple coring the top 70 m of sediment at Site U1554 (Proposed Site REYK-6A) to obtain cores for evaluating potential problems with the magnetic core orientation tools and for assessing other potential sources of errors that might explain prior anomalous core orientation results. Comparison of the observed core orientation from magnetic orientation tools to the expected orientation based on the paleomagnetic directions recorded in the cores revealed an 180° misalignment in the assembly of one of the tools. This misalignment appears to have persisted over several years and could explain most of the problems previously noted. The assembly part was fixed, and this problem was eliminated for future expeditions. We subsequently spent 20 days at Site U1555 (Proposed Site REYK-13A) to test the three types of drill bits, an underreamer, and a coring bit in six holes. The TCI bits were the best performers, the TCI/PDC hybrid bit did not stand up to the harsh formation, and the PDC bit did not get sufficient run time because of a mud motor failure. The cutter block underreamer is not considered able to perform major hole opening in basalt but could be useful for knocking out ledges. The PDC coring bit cut good quality basalt cores at an unacceptably low rate. In the seventh and final hole (U1555G), we used a regular RCB coring bit to recover the entire 130 m basalt section specified in the Expedition 395 Scientific Prospectus and provided the project team with shipboard data and samples. The basalt section was successfully wireline logged before the logging winch motor failed, which precluded further operations for safety reasons. Additional operations plans in support of Expedition 395, including coring, logging, and casing at Site U1554, had to be canceled, and Expedition 384 ended prematurely on 24 August in Kristiansand.« less
  4. International Ocean Discovery Program (IODP) Expedition 390C was implemented in response to the global COVID-19 pandemic and occupied sites proposed for the postponed Expeditions 390 and 393. The objectives for Expedition 390C were to core one hole at each site with the advanced piston corer/extended core barrel (APC/XCB) system to basement for gas safety monitoring and to install a reentry system with casing through the sediment to between ~5 m above basement and <5 m into basement in a second hole. These operations will expedite basement drilling during the rescheduled South Atlantic Transect Expeditions 390 and 393. The six primarymore »sites for those expeditions form a transect perpendicular to the Mid-Atlantic Ridge on the South American plate, overlying crust ranging in age from 7 to 61 Ma. Basement coring will increase our understanding of how crustal alteration progresses over time across the flanks of a slow/intermediate spreading ridge and how microorganisms survive in deep subsurface environments. Sediment will be used in paleoceanographic and microbiological studies. Expedition 390C started in Kristiansand, Norway, and ended in Cape Town, South Africa, after 31 days of operations. We cored a single APC/XCB sediment hole to the contact with hard rock material at four of the six sites and successfully installed reentry systems with casing at three. Two failed attempts at drilling in casing and a reentry system into hard rock at Site U1558 indicate that the Dril-Quip reentry cones and running tools are incompatible with use in hard rock because the release mechanism does not work when the casing string weight cannot be fully removed from the running tool. Therefore, at Sites U1558 and U1559, casing was installed to ~10 m above basement. Site U1557 has a thick sediment cover (564 m) and will require multiple casing strings to reach basement; a single 16" casing string was installed to 60 meters below seafloor at this site, and later expeditions will extend casing.« less
  5. International Ocean Discovery Program (IODP) Expedition 378 was designed to recover the first comprehensive set of Paleogene sedimentary sections from a transect of sites strategically positioned in the South Pacific Ocean to reconstruct key changes in oceanic and atmospheric circulation. These sites would have provided an unparalleled opportunity to add crucial new data and geographic coverage to existing reconstructions of Paleogene climate. Following the ~15 month postponement of Expedition 378 and subsequent port changes that resulted in a reduction of the number of primary sites, testing and evaluation of the research vessel JOIDES Resolution derrick in the weeks preceding themore »expedition determined that it would not support deployment of drill strings in excess of 2 km. Consequently, only one of the originally approved seven primary sites was drilled. Expedition 378 recovered the first continuously cored, multiple-hole Paleogene sedimentary section from the southern Campbell Plateau at Site U1553. This high–southern latitude site builds on the legacy of Deep Sea Drilling Project Site 277 (a single, partially spot cored hole), providing a unique opportunity to refine and expand existing reconstructions of Cenozoic climate history. As the world’s largest ocean, the Pacific Ocean is intricately linked to major changes in the global climate system. Previous drilling in the low-latitude Pacific Ocean during Ocean Drilling Program Legs 138 and 199 and Integrated Ocean Drilling Program Expeditions 320 and 321 provided new insights into climate and carbon system dynamics, productivity changes across the zone of divergence, time-dependent calcium carbonate dissolution, bio- and magnetostratigraphy, the location of the Intertropical Convergence Zone, and evolutionary patterns for times of climatic change and upheaval. Expedition 378 in the South Pacific Ocean uniquely complements this work with a high-latitude perspective, especially because appropriate high-latitude records are unobtainable in the Northern Hemisphere of the Pacific Ocean. Expedition 378 provides material from the South Pacific Ocean in an area critical for high-latitude climate reconstructions spanning the early Paleocene to late Oligocene. Site U1553 and the entire corpus of shore-based investigations will significantly contribute to the challenges of the “Climate and Ocean Change: Reading the Past, Informing the Future” theme of the 2013–2023 IODP Science Plan (How does Earth’s climate system respond to elevated levels of atmospheric CO2? How resilient is the ocean to chemical perturbations?). Furthermore, Expedition 378 provides material from the South Pacific Ocean in an area critical for high-latitude climate reconstructions spanning the Paleocene to late Oligocene.« less