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The South Atlantic Transect (SAT) is a multidisciplinary scientific ocean drilling experiment designed to investigate the evolution of the ocean crust and overlying sediments across the western flank of the Mid-Atlantic Ridge. This project comprises four International Ocean Discovery Program expeditions: fully staffed Expeditions 390 and 393 (April–August 2022) built on engineering preparations during Expeditions 390C and 395E (October–December 2020 and April–June 2021, respectively) that took place without science parties during the height of the Coronavirus Disease 2019 (COVID-19) pandemic. Through operations along a crustal flow line at ~31°S, the SAT recovered complete sedimentary sections and the upper ~40–340 m of the underlying ocean crust formed at a slow- to intermediate-spreading rate at the Mid-Atlantic Ridge over the past ~61 My. The sediments along this transect were originally spot cored more than 50 y ago during Deep Sea Drilling Project Leg 3 (December 1968–January 1969) to help verify the theories of seafloor spreading and plate tectonics. The SAT expeditions targeted six primary sites on 7, 15, 31, 49, and 61 Ma ocean crust that fill critical gaps in our sampling of intact in situ ocean crust with regard to crustal age, spreading rate, and sediment thickness. Drilling these sites was required to investigate the history, duration, and intensity of the low-temperature hydrothermal interactions between the aging ocean crust and the evolving South Atlantic Ocean. This knowledge will improve the quantification of past hydrothermal contributions to global biogeochemical cycles and help develop a predictive understanding of the impacts of variable hydrothermal processes and exchanges. Samples from the transect of the previously unexplored sediment- and basalt-hosted deep biosphere beneath the South Atlantic Gyre are essential to refine global biomass estimates and examine microbial ecosystems' responses to variable conditions in a low-energy gyre and aging ocean crust. The transect, located near World Ocean Circulation Experiment Line A10, provides 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. During engineering Expeditions 390C and 395E (5 October–5 December 2020 and 6 April–6 June 2021, respectively), a single hole was cored through the sediment cover and into the uppermost rocks of the ocean crust with the advanced piston corer and extended core barrel systems at five of the six primary proposed SAT sites. Reentry systems with casing were then installed either into basement or within 10 m of basement at each of those five sites. Expedition 390 (7 April–7 June 2022) conducted operations at three of the SAT sites, recovering 700 m of core (77% recovery) over 30.3 days of on-site operations. Sediment coring, basement coring, and wireline logging were conducted at two sites on ~61 Ma crust (Sites U1556 and U1557), and sediment coring was completed at the 7 Ma Site U1559. During Expedition 390, more than 1.2 km of sediments was characterized, including 793 m of core collected during Expeditions 390C and 395E at Sites U1556, U1557, and U1559 as well as Expedition 395E Site U1561, which was cored on thinly (<50 m) sedimented ~61 Ma crust. The uppermost ~342 and ~120 m of ~61 Ma ocean crust was cored at Sites U1556 and U1557, respectively. Geophysical wireline logging was achieved at both sites, but the basement hole at Site U1556 was not preserved as a legacy hole because of subsidence of the reentry cone below the seafloor. At Site U1557, the drill bit was deposited on the seafloor prior to downhole logging, leaving Hole U1557D available for future deepening and establishing a legacy borehole for basement hydrothermal and microbiological experiments. Expedition 393 (7 June–7 August 2022) operated at four sites, drilling in 12 holes to complete this initial phase of the SAT. Complete sedimentary sections were collected at Sites U1558, U1583, and U1560 on 49, 31, and 15 Ma crust, respectively, and together with 257.7 m of sediments cored during earlier operations, more than 600 m of sediments was characterized. The uppermost ocean crust was drilled at Sites U1558, U1560, and U1583 with good penetration (~130 to ~204 meters subbasement); however, at the youngest ~7 Ma Site U1559, only ~43 m of basement penetration was achieved in this initial attempt. Geophysical wireline logs were achieved at Sites U1583 and U1560 only. Expeditions 390 and 393 established legacy sites available for future deepening and downhole basement hydrothermal and microbiological experiments at Sites U1557, U1560, and U1559 on 61, 15, and 7 Ma crust, respectively. Highlights of the SAT expeditions include (1) recovering abundant altered glass, hydrothermal veins, complex breccias, and a wide range of alteration halos in the volcanic sequences of the uppermost ocean crust formed at 7–61 Ma, indicating low-temperature hydrothermal processes and exchanges between seawater and basalts across the western flank of the southern Mid-Atlantic Ridge for millions to tens of millions of years; (2) documenting extended redox gradients from both the seafloor and the sediment/basement interface that indicate significant subsurface fluid flow and may support a diversity of microorganisms and metabolisms; and (3) recovering an almost complete stratigraphic record of the Cenozoic (including the Paleocene/Eocene Thermal Maximum and other key climate events) composed of nannofossil oozes with varying amounts of clay indicating the shoaling and deepening of the calcite compensation depth. 

International Ocean Discovery Program (IODP) Site U1556, located on a basement high above Site U1557, is one of the oldest sites drilled on the South Atlantic Transect with a basement age of ~61 Ma. Here, we present semiquantitative X-ray fluorescence core scan data from the Site U1556 splice and compare them with shipboard magnetic susceptibility and natural gamma ray (NGR) measurements to characterize elemental composition changes downcore. Elements primarily associated with detrital (e.g., Al, Fe, K, Ti, and Zr) and biogenic (e.g., Ca) sources are inversely correlated. Biogenic and detrital sourced elements vary synchronously with magnetic susceptibility and NGR measurements following alternations between silty clay and calcareous nannofossil ooze/chalk in Unit I, whereas biogenic sourced elements tend to dominate Unit II, corresponding to a lithology change to predominantly calcareous nannofossil ooze/chalk. 

International Ocean Discovery Program (IODP) Expeditions 390C, 395E, 390, and 393 recovered deepwater sediments from the western flank of the Mid-Atlantic Ridge in the South Atlantic Ocean along the South Atlantic Transect (SAT) at ~31°S. Collectively, these expeditions recovered ~2 km of sediment cores that have the potential to capture key features of Cenozoic climate change. In this report, we show semiquantitative bulk elemental results from X-ray fluorescence (XRF) scanning of the sediment cores from IODP Site U1560 recovered during Expeditions 395E and 393. The oceanic basement at this site is ~15 My old, making it the second youngest of the SAT sites located west of the Mid-Atlantic Ridge. Here, XRF data are compared with pass-through magnetic susceptibility and natural gamma radiation of the sediment cores, measured aboard JOIDES Resolution. The resulting trends and correlations highlight elemental variations through time, mainly reflecting lithologic and compositional differences. At Site U1560, Ca counts reflect the occurrence of nannofossil ooze, which is the dominant lithology for the whole site. In the Miocene-aged Lithologic Units IE–IA from 140 to 50 m core composite depth below seafloor (CCSF), several high-intensity spikes of detrital elements (i.e., Fe, Ti, Al, Si, and Zr) correspond to intervals of clay-rich nannofossil ooze. Detrital elemental counts in the entire Pliocene record (50 to ~25 m CCSF) are the lowest. A sharp shift is observed at the Pliocene/Pleistocene boundary at ~25 m CCSF, with the uppermost Pleistocene record showing high-frequency and high-intensity variations in siliciclastic elements, which correlates well with the pass-through magnetic susceptibility. 

We report semiquantitative elemental data from X-ray fluorescence (XRF) scanning of Site U1558 sediment cores drilled during International Ocean Discovery Program Expeditions 390C and 393. These expeditions, together with Expeditions 395E and 390, form the South Atlantic Transect, which collected sediment and basement cores from the western flank of the southern Mid-Atlantic Ridge. XRF scanning of the continuous splice of Site U1558, using Holes U1558A and U1558F, was conducted at three acceleration voltages to capture a range of major, minor, and trace elements. At Site U1558, positive correlations exist between terrigenous-sourced elements (Al, Si, Ti, and Fe) and a negative correlation exists between the terrigenous-sourced elements and Ca. XRF geochemistry is correlated with lithologic changes, most notably at the boundary of Lithologic Units I and II, where Unit I is brown and reddish brown nannofossil-rich clay and Unit II is pink, pinkish white, pinkish gray, and light brown nannofossil ooze and chalk with varying amounts of clay and foraminifera. Peaks in XRF data align with the boundaries of Lithologic Subunits IIA and IIB and Subunits IIB and IIC. 

Site U1557 is the deepest and one of the oldest sites drilled during International Ocean Discovery Program Expeditions 390C, 395E, 390, and 393 on the South Atlantic Transect. It differs from the nearby Site U1556, which also sits on early Paleocene crust, by its stratigraphically expanded Paleocene–Eocene section. Here, we present the results of programmatic X-ray fluorescence (XRF) core scanning of the entire thickness of the sedimentary section at Site U1557. We find a major shift in XRF geochemistry at the boundary between Lithologic Units I and II, coincident with a shift in spectral gamma ray and magnetic susceptibility, as well as a shift from alternating pelagic carbonate and pelagic clay in Unit I to pelagic carbonate in Unit II. Within Unit I, shifts in major elemental composition of core material track alternations between carbonate-rich and clay-rich intervals. 

The western South Atlantic Ocean is a relatively understudied area of the world’s ocean, in part because of the lack of scientific ocean drilling and complete sedimentary sequences. During 2020–2022, a series of International Ocean Discovery Program Expeditions (390C, 395E, 390, and 393; South Atlantic Transect) sailed to this area, recovering material from the western flank of the Mid-Atlantic Ridge at a latitude of ~31°S. Here, we used X-ray fluorescence scanning of the sediment cores recovered and combined the data with shipboard magnetic susceptibility and natural gamma radiation to generate long-term geochemical records at Site U1561. These records enable us to document climatic and environmental perturbations on varying timescales and explore the paleoclimatic and paleoceanographic history of the western South Atlantic Ocean during the Cenozoic. 

During International Ocean Discovery Program (IODP) Expeditions 390C, 395E, 390, and 393, deepwater sediments were recovered from the western flank of the southern Mid-Atlantic Ridge along a crustal flow line at ~31°S. This multidisciplinary experiment allowed the recovery of data fundamental to reconstructing past climate changes as well as variations in ocean circulation, productivity, and chemistry (i.e., fluctuations in the carbonate compensation depth) in the South Atlantic Ocean. Here, we report semiquantitative elemental results from X-ray fluorescence (XRF) scanning of the sediment package cored at IODP Site U1559 in the South Atlantic Ocean. Located at 15°02.0941′W, Site U1559 is the easternmost site of the South Atlantic Transect and the closest to the Mid-Atlantic Ridge, located on ~6.6. Ma ocean crust. The XRF data are also compared with magnetic susceptibility and natural gamma radiation measured on the R/V JOIDES Resolution to assess correlations with the different lithologic units/subunits. At Site U1559, sediments are predominantly nannofossil ooze with varying amounts of foraminifera, which is reflected by the dominant Ca counts. Trends in elemental counts reflect the slight variations in siliciclastic materials within the Pleistocene. Major shifts in elemental counts were observed at the sharp contact between Pliocene–Pleistocene Subunits IC and ID, as well as the Miocene–Pliocene transition. 

The western South Atlantic Ocean has not been drilled since the end of the Deep Sea Drilling Program, leading to a dearth of sedimentary sequences available from this sector of the Atlantic Ocean. In 2020–2022, a transect of new sites was drilled during International Ocean Discovery Program Expeditions 390C, 395E, 390, and 393 at 31°S and spanning from 28.8°W to 15.2°W. Here, we use X-ray fluorescence data, combined with shipboard magnetic susceptibility and natural gamma radiation, to characterize the sediments below the oligotrophic South Atlantic Gyre at Site U1583. These geochemical data add to the otherwise understudied southwest Atlantic Ocean. 

The South Atlantic Transect (SAT) is a multidisciplinary scientific ocean drilling experiment designed to investigate the evolution of the oceanic crust and overlying sediments across the western flank of the Mid-Atlantic Ridge. This project comprises four International Ocean Discovery Program expeditions: fully staffed Expeditions 390 and 393 (April–August 2022) built on engineering preparations during Expeditions 390C and 395E that took place without science parties during the height of the Coronavirus Disease 2019 (COVID-19) pandemic. Through operations along a crustal flow line at ~31°S, the SAT recovered complete sedimentary sections and the upper ~40–340 m of the underlying ocean crust formed at a slow to intermediate spreading rate at the Mid-Atlantic Ridge over the past ~61 My. The sediments along this transect were originally spot cored more than 50 y ago during Deep Sea Drilling Project Leg 3 (December 1968–January 1969) to help verify the theories of seafloor spreading and plate tectonics. The SAT expeditions targeted six primary sites on 7, 15, 31, 49, and 61 Ma ocean crust that fill critical gaps in our sampling of intact in situ ocean crust with regards to crustal age, spreading rate, and sediment thickness. Drilling these sites was required to investigate the history, duration, and intensity of the low-temperature hydrothermal interactions between the aging ocean crust and the evolving South Atlantic Ocean. This knowledge will improve the quantification of past hydrothermal contributions to global biogeochemical cycles and help develop a predictive understanding of the impacts of variable hydrothermal processes and exchanges. Samples from the transect of the previously unexplored sediment- and basalt-hosted deep biosphere beneath the South Atlantic Gyre are essential to refine global biomass estimates and examine microbial ecosystems’ responses to variable conditions in a low-energy gyre and aging ocean crust. The transect is located near World Ocean Circulation Experiment Line A10, which provides a baseline for 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. During engineering Expeditions 390C and 395E, a single hole was cored through the sediment cover and into the uppermost rocks of the ocean crust with the advanced piston corer (APC) and extended core barrel (XCB) systems at five of the six primary proposed SAT sites. Reentry systems with casing were then installed either into basement or within 10 m of basement at each of those five sites. Expedition 390 (7 April–7 June 2022) conducted operations at three of the SAT sites, recovering 700 m of core (77%) over 30.3 days of on-site operations. Sediment coring, basement coring, and wireline logging were conducted at two sites on 61 Ma crust (Sites U1556 and U1557), and sediment coring was completed at the 7 Ma Site U1559. Expedition 393 operated at four sites, drilling in 12 holes to complete this initial phase of the SAT. Complete sedimentary sections were collected at Sites U1558, U1583, and U1560 on 49, 31, and 15 Ma crust, respectively, and together with 257.7 m of sediments cored during earlier operations, more than 600 m of sediments was characterized. The uppermost ocean crust was drilled at Sites U1558, U1560, and U1583 with good penetration (~130 to ~204 meters subbasement), but at the youngest ~7 Ma Site U1559, only ~43 m of basement penetration was achieved in this initial attempt. Geophysical wireline logs were aquired at Sites U1583 and U1560. Expeditions 390 and 393 established legacy sites available for future deepening and downhole basement hydrothermal and microbiological experiments at Sites U1557, U1560, and U1559 on 61, 15, and 7 Ma crust, respectively. 

The South Atlantic Transect (SAT) is a multidisciplinary scientific ocean drilling project that comprises four International Ocean Discovery Program (IODP) expeditions: engineering Expeditions 390C and 395E as well as Expeditions 390 and 393. Altogether, the expeditions aim to recover complete sedimentary sections and the upper 100–350 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 (December 1968–January 1969) to help verify the theories of seafloor spreading and plate tectonics. Given dramatic advances in drilling technology and analytical capabilities since Leg 3, many high-priority scientific objectives can be addressed by revisiting the transect. The SAT expeditions target six primary sites on 7, 15, 31, 49, and 61 Ma ocean crust, which fill critical gaps in our sampling of intact in situ ocean crust with regards to crustal age, spreading rate, and sediment thickness. Drilling these sites is 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 biogeochemical cycles. Samples from the transect of the previously unexplored sediment- and basalt-hosted deep biosphere beneath the South Atlantic Gyre are essential to refining global biomass estimates and examining microbial ecosystems’ responses to variable conditions in a low-energy gyre and aging ocean crust. The transect is 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. Engineering Expeditions 390C and 395E cored a single hole through the sediment/basement interface with the advanced piston corer/extended core barrel system at five of the six primary proposed SAT sites and installed a reentry system with casing either into basement or within 10 m of basement at each of those five sites. Expedition 390 (7 April–7 June 2022) conducted operations at three of the SAT sites, recovering 700 m of core (77% recovery) over 30.3 days of on-site operations. Sediment coring, basement drilling, and logging were conducted at two sites on 61 Ma crust, and sediment coring was completed at the 7 Ma crust site. At Site U1557 on 61 Ma crust, the drill bit was deposited on the seafloor prior to downhole logging, leaving Hole U1557D available for future deepening and to establish a legacy borehole for basement hydrothermal and microbiological experiments. Expedition 390 scientists additionally described, and analyzed data from, 792 m of core collected during Expeditions 390C and 395E. Expedition 393 plans to operate at four sites, conducting basement drilling and downhole logging at the 7 Ma site, in addition to sediment coring, basement drilling, and logging at the sites intermediate in age.