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

Contreras, E.; García, P. Jiménez; Sager, William W.; Thoram, S.; Hoernle, Kaj; Sarralde, Roberto; Zhou, H.

doi:10.1029/2022gc010624

Cited by 3 publications

(14 citation statements)

References 80 publications

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“…However, the E‐W progression was disrupted by a ridge jump which captured a narrow band of South American crust. Furthermore, the narrow C33r band atop the eastern flank exactly coincides with a prominent rift valley that was mapped in seismic and bathymetry data (Contreras et al., 2022; Figure S3 in Supporting Information ). Similar rifts are found within Rio Grande Rise (Gamboa & Rabinowitz, 1984) and are probably related to the VB rifts (Sager et al., 2021).…”

Section: Discussionsupporting

confidence: 60%

“…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: Iodp 391 Drilling At Vbmentioning

confidence: 99%

“…Thick chalk sequences were recovered above basement at Sites U1576 and U1577 providing magnetic stratigraphy context. Basal sediments from both holes show a long-reversed polarity chron that is interpreted as C33r (Sager et al, 2022;Figures S4 and S5 in Supporting Information S1) because this is the only reversed period during the early Campanian. At Site U1576, the C33r sediment chronozone is contiguous with reversed polarity igneous basement.…”

Section: Iodp Core Datamentioning

confidence: 99%

“…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 S1).…”

Section: Iodp 391 Drilling At Vbmentioning

confidence: 99%

“…Dashed green and white lines in Panel D show the locations of rift‐bounding faults identified in Contreras et al. (2022). VB = Valdivia Bank, CWR = Central Walvis Ridge, FR = Frio Ridge, AFR = Africa, SAM = South America.…”

Section: Introductionmentioning

confidence: 97%

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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: Discussionsupporting

confidence: 60%

Section: Iodp 391 Drilling At Vbmentioning

confidence: 99%

Section: Iodp Core Datamentioning

confidence: 99%

Section: Iodp 391 Drilling At Vbmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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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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Evidence for compositionally distinct upper mantle plumelets since the early history of the Tristan-Gough hotspot

et al. 2023

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Recent studies indicate that mantle plumes, which transfer material and heat from the earth’s interior to its surface, represent multifaceted upwellings. The Tristan-Gough hotspot track (South Atlantic), which formed above a mantle plume, documents spatial geochemical zonation in two distinct sub-tracks since ~70 Ma. The origin and the sudden appearance of two distinct geochemical flavors is enigmatic, but could provide insights into the structural evolution of mantle plumes. Sr–Nd–Pb–Hf isotope data from the Late Cretaceous Rio Grande Rise and adjacent Jean Charcot Seamount Chain (South American Plate), which represent the counterpart of the older Tristan-Gough volcanic track (African Plate), extends the bilateral-zonation to ~100 Ma. Our results support recent numerical models, demonstrating that mantle plumes can split into distinct upper mantle conduits, and provide evidence that these plumelets formed at the plume head-to-plume tail transition. We attribute the plume zonation to sampling the geochemically-graded margin of the African Large Low-Shear-Velocity Province.

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Expedition 391 summary

Sager,

Hoernle,

Höfig

et al. 2023

Proceedings of the International Ocean Discovery Program

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

Cited by 3 publications

References 80 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

Evidence for compositionally distinct upper mantle plumelets since the early history of the Tristan-Gough hotspot

Expedition 391 summary

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