Expedition 391 Preliminary Report: Walvis Ridge Hotspot

Sager, William W.; Hoernle, Kaj; Höfig, T.W.

doi:10.14379/iodp.pr.391.2022

Cited by 6 publications

(18 citation statements)

References 142 publications

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“…At Site U1577, the transition from C34n to C33r occurs in chalk ∼7 m above the basement surface. Biostratigraphy indicates that basal sedimentary rocks at this site are earliest Campanian and possibly Turonian, consistent with C34n (Sager et al., 2022; Figure S5 in Supporting Information ). Microfossil biostratigraphy indicates a sedimentation rate of ∼14–16 m/Ma at both sites.…”

Section: Resultssupporting

confidence: 62%

“…The most striking is a curved negative anomaly along the VB western flank (Figure 2), which has been interpreted as C33r (Cande et al., 1988; Thoram et al., 2019). This interpretation is supported by bio‐ and magneto‐stratigraphic ages from IODP Site U1576 (Sager et al., 2022; Figure S4 in Supporting Information ). Under symmetrical spreading conditions, the expected C33r anomaly on one plate is a linear negative band with a trend of N26°W and width of ∼170 km, which is observed in the spreading corridors north of the Rio Grande‐Florianopolis FZ (22.5°S at the MAR) and south of the 32.5° FZ (Figure S2 in Supporting Information ).…”

Section: Resultsmentioning

confidence: 61%

“…Sites U1576 and U1577 were sited in part to test the magnetic anomaly interpretation, with the former located on a negative magnetic anomaly and the latter on a positive anomaly. Bio‐ and magnetostratigraphic analyses were performed on recovered cores to determine age and magnetic polarity (Sager et al., 2022; Text S1 and S2 in Supporting Information ).…”

Section: Methodsmentioning

confidence: 99%

“…IODP Expedition 391 cored into igneous rock on the north, west, and south flanks of VB at Sites U1575, U1576, and U1577, respectively (Sager et al., 2022). Sites U1576 and U1577 were sited in part to test the magnetic anomaly interpretation, with the former located on a negative magnetic anomaly and the latter on a positive anomaly.…”

Section: Methodsmentioning

confidence: 99%

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Nature and Origin of Magnetic Lineations Within Valdivia Bank: Ocean Plateau Formation by Complex Seafloor Spreading

Thoram

Sager

Gaastra

et al. 2023

Geophysical Research Letters

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Valdivia Bank (VB) is a Late Cretaceous oceanic plateau formed by volcanism from the Tristan-Gough hotspot at the Mid-Atlantic Ridge (MAR). To better understand its origin and evolution, magnetic data were used to generate a magnetic anomaly grid, which was inverted to determine crustal magnetization. The magnetization model reveals quasi-linear polarity zones crossing the plateau and following expected MAR paleo-locations, implying formation by seafloor spreading over ∼4 Myr during the formation of anomalies C34n-C33r. Paleomagnetism and biostratigraphy data from International Ocean Discovery Program Expedition 391 confirm the magnetic interpretation. Anomaly C33r is split into two negative bands, likely by a westward ridge jump. One of these negative anomalies coincides with deep rift valleys, indicating their age and mechanism of formation. These findings imply that VB originated by seafloor spreading-type volcanism during a plate reorganization, not from a vertical stack of lava flows as expected for a large volcano.Plain Language Summary Oceanic plateaus are large, elevated underwater features commonly formed from volcanic material from a hotspot. Valdivia Bank is a Late Cretaceous oceanic plateau in the southeast Atlantic Ocean formed by volcanism from the Tristan-Gough hotspot near the Mid-Atlantic Ridge. The origin and evolution of Valdivia Bank is poorly defined, but new magnetic data suggests the edifice originated through ridge-centered volcanism, with lateral accretion of crust. This is unlike the evolution of a massive volcano, which would be expected to create a vertical stack of lava flows. Magnetic inversion modeling suggests the plateau was formed by seafloor spreading during the formation of anomalies C34n-C33r, with the plateau becoming younger from east to west, rather than north-south as predicted by some hotspot models. Results from International Ocean Discovery Program Expedition 391 paleomagnetism and biostratigraphy confirm the anomaly interpretation.

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Section: Resultssupporting

confidence: 62%

Section: Resultsmentioning

confidence: 61%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Nature and Origin of Magnetic Lineations Within Valdivia Bank: Ocean Plateau Formation by Complex Seafloor Spreading

Thoram

Sager

Gaastra

et al. 2023

Geophysical Research Letters

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“…This advisory group recommended drilling several hotspot seamount chains to leverage then new results from the Hawaiian-Emperor chain drilling. The proposal matured under the guidance of the IODP Science Plan 2013-2023(Bickle et al, 2013 and mainly addresses the theme "Earth Connections: Deep processes and their impact on Earth's surface environment" because the project cored volcanic hotspot seamounts to understand the sources of hotspot magmas and their evolution with time. In particular, the project addressed "Challenge 8: What are the composition, structure, and dynamics of Earth's upper mantle?"…”

Section: Connections To the 2050 Science Frameworkmentioning

confidence: 99%

Expedition 397T Preliminary Report: Return to Walvis Ridge Hotspot

Sager¹,

Blum²

2022

International Ocean Discovery Program Preliminary Report

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International Ocean Discovery Program Expedition 397T sought to address the shortage of drilling time caused by COVID-19 mitigation during Expedition 391 (Walvis Ridge Hotspot) by drilling at two sites omitted from the earlier cruise. A week of coring time was added to a transit of JOIDES Resolution from Cape Town to Lisbon, which would cross Walvis Ridge on its way north. These two sites were located on two of the three seamount trails that emerge from the split in Walvis Ridge morphology into several seamount chains at 2°E. Site U1584 (proposed Site GT-6A) sampled the Gough track on the east, and Site U1585 (proposed Site TT-4A) sampled the Tristan track on the west. Together with Site U1578, drilled on the Center track during Expedition 391, they form a transect across the northern Walvis Ridge Guyot Province. The goal was to core seamount basalts and associated volcanic material for geochemical and isotopic, geochronologic, paleomagnetic, and volcanologic study. Scientifically, one emphasis was to better understand the split in geochemical and isotopic signatures that occurs at the morphologic split. Geochronology would add to the established age progression but also give another dimension to understanding Walvis Ridge seamount formation by giving multiple ages at the same sites. The paleomagnetic study seeks to establish paleolatitudes for Walvis Ridge sites for comparison with those published from hotspot seamount chains in the Pacific, in particular to test whether a component of true polar wander affects hotspot paleolatitude.

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Bathymetry of Valdivia Bank, Walvis Ridge, South Atlantic Ocean: Implications for Structure and Geologic History of a Hot Spot Plateau

Contreras¹,

García²,

Sager³

et al. 2022

Geochem Geophys Geosyst

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Valdivia Bank is an oceanic plateau in the south Atlantic formed by hot spot volcanism at the mid-Atlantic Ridge (MAR) (Kumar, 1979;O'Connor & Duncan, 1990). It is part of Walvis Ridge, an aseismic volcanic chain that stretches from the Namibian margin of west Africa nearly to the MAR. Although commonly attributed to volcanism from a deep mantle plume (Courtillot et al., 2003;Hoernle et al., 2015), its morphology is more complex than plume trails such as the Hawaiian-Emperor and Louisville seamount chains (e.g., O'Connor & Jokat, 2015b;O'Connor & Le Roex, 1992;Sager et al., 2021). Off Africa, the Walvis Ridge is a linear ridge (Frio Ridge) trending SW-NE. It turns to N-S by nearly a right angle at Valdivia Bank, and upon resuming its SW-NE

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Expedition 391 Preliminary Report: Walvis Ridge Hotspot

Cited by 6 publications

References 142 publications

Nature and Origin of Magnetic Lineations Within Valdivia Bank: Ocean Plateau Formation by Complex Seafloor Spreading

Nature and Origin of Magnetic Lineations Within Valdivia Bank: Ocean Plateau Formation by Complex Seafloor Spreading

Expedition 397T Preliminary Report: Return to Walvis Ridge Hotspot

Bathymetry of Valdivia Bank, Walvis Ridge, South Atlantic Ocean: Implications for Structure and Geologic History of a Hot Spot Plateau

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