Stratigraphic numerical modelling of a carbonate platform on the Romanche transverse ridge, equatorial Atlantic

Gasperini, Luca; Bonatti, Enrico; Ligi, Marco; Sartori, R.; Borsetti, Anna Maria; Negri, Alessandra; Ferrari, Alice; Sokolov, S. Yu.

doi:10.1016/s0025-3227(96)00068-0

Cited by 19 publications

(31 citation statements)

References 14 publications

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“…This suggests a 0.06 mm/a subsidence rate of the Romanche sunken islands since middle Miocene, assuming a present day 1200–1300 m depth of the erosional surface at the base of the carbonate platform. Sr isotopic ages of Romanche platform A samples (up to 10 Ma) are significant lower than those estimated by Gasperini et al []. The complex tectonic framework of the eastern Romanche may have resulted in multiple stages of transtension/transpression and in more than one event of uplift, emersion and subsidence.…”

Section: Discussionmentioning

confidence: 99%

Nonvolcanic tectonic islands in ancient and modern oceans

Palmiotto

Corda

Ligi

et al. 2013

Geochem Geophys Geosyst

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[1] Most oceanic islands are due to excess volcanism caused by thermal and/or compositional mantle melting anomalies. We call attention here to another class of oceanic islands, due not to volcanism but to vertical motions of blocks of oceanic lithosphere related to transform tectonics. Sunken tectonic islands capped by carbonate platforms have been previously identified along the Vema and Romanche transforms in the equatorial Atlantic. We reprocessed seismic reflection lines, did new facies analyses and 87 Sr/ 86 Sr dating of carbonate samples from the carbonate platforms. A 50 km long narrow paleoisland flanking the Vema transform, underwent subsidence, erosion, and truncation at sea level; it was then capped by a 500 m thick carbonate platform dated by 87 Sr/ 86 Sr at $11-10 Ma. Three former islands on the crest of the Romanche transverse ridge are now at $900 m bsl; they show horizontal truncated surfaces of oceanic crust capped by $300 m thick carbonate platforms, with 10-6 Ma Sr isotopic ages. These sunken islands formed due to vertical tectonics related to transtension/transpression along long-offset slow-slip transforms. Another tectonic sunken island is Atlantis Bank, an uplifted gabbroic block along the Atlantis II transform (SW Indian Ridge) $700 m bsl. A modern tectonic island is St. Peter and St. Paul Rocks, a rising slab of upper mantle located at the St. Paul transform (equatorial Atlantic). ''Cold'' tectonic islands contrast with ''hot'' volcanic islands related to mantle thermal and/or compositional anomalies along accretionary boundaries and within oceanic plates, or to supra-subduction mantle melting that gives rise to islands arcs.

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Section: Discussionmentioning

confidence: 99%

Nonvolcanic tectonic islands in ancient and modern oceans

Palmiotto

Corda

Ligi

et al. 2013

Geochem Geophys Geosyst

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“…This category of topographic anomalies, peculiar to slow spreading oceans, favours mantle uplift with extremely reduced or absent magmatic crust. It has been repeatedly suggested that transverse ridges result from strong rates of vertical tectonic uplift and may even undergo accelerated thermal subsidence (Bonatti, 1978, 1994; Gasperini et al ., 1997). However, the common characteristic of these models is the assumption that, at the beginning of seafloor spreading, the tops of such structures were at zero‐age depths, i.e.…”

Section: Discussionmentioning

confidence: 99%

Discovery of Late Jurassic fossils inside modern sediments at Gorringe Bank (Eastern Atlantic Ocean) and some geological implications.

et al. 2004

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During a recent expedition at the Gorringe Bank (eastern Atlantic, 150 miles SW off Portugal), one of the rare sites in the ocean where mantle rocks crop out at very shallow depths (-30 m), the Gettysburg and Ormonde seamounts, the two summits on the Gorringe Bank, were surveyed in detail. At Gettysburg seamount, within the modern bioclastic material, which is continually produced on the summit and exported to deep water, several examples of Mesozoic cephalopods were found. These fossils, reworked 'in situ', gave an age spanning from Kimmeridgian-Tithonian to Hauterivian (145-155 Ma) and recall some condensed Jurassic sequences of the Thetyan region compatible with shallow water (<200 m). The serendipitous discovery of such ancient faunas within modern sediments suggests that Gorringe Bank was a seamount at the early opening of the Atlantic Ocean and requires us to reassess the age of rifting along the Iberian margin and the importance of vertical tectonics for non-volcanic, mantle-rooted seamounts

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“…The Romanche transverse ridge (equatorial Atlan tic) is located at the northern side of the Romanche Fracture Zone across the eastern intersection of the MAR and the Romanche Fracture Zone (Gasperini et al, 1997). A number of separate blocks of this trans verse ridge emerged in the early-middle Miocene above sea level and are now covered with shallow water carbonate sediments, which were deposited on the subsiding oceanic basement simultaneously with subaerial erosion (Gasperini et al, 1997).…”

Section: Geodynamic Interpretation Of the Weathering Conditions Of Thmentioning

confidence: 99%

“…A number of separate blocks of this trans verse ridge emerged in the early-middle Miocene above sea level and are now covered with shallow water carbonate sediments, which were deposited on the subsiding oceanic basement simultaneously with subaerial erosion (Gasperini et al, 1997). The sum mits of these submersed blocks of the Romanche transverse ridge occur now at a depth of 1000 m. According to the data of seismic profiling and litho logical investigations, the ocean floor subsidence of such considerable amplitude began in this region of the crest zone of the Mid Atlantic Ridge in the early Miocene (Gasperini et al, 1997).…”

Section: Geodynamic Interpretation Of the Weathering Conditions Of Thmentioning

confidence: 99%

Silicification of peridotites at the stalemate fracture zone (Northwestern Pacific): Reconstruction of the conditions of low-temperature weathering and tectonic interpretation

et al. 2012

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During cruise SO201 1b of the joint Russian-German expedition on the R/V Sonne in 2009, mantle peridotites affected by varying secondary alteration were dredged on the eastern slope of the north western segment of the Stalemate transverse ridge adjacent to the eponymous fracture zone. The collection discussed in this paper included four samples of silicified serpentinites after dunites and 11 lherzolite samples serpentinized to a varying degree. The abundance of amorphous silica and quartz, very high SiO 2 content (up to 88.7 wt %), and unusually low MgO (up to 1.4 wt %) in the serpentinized dunites strongly distinguish these rocks from the known products of hydrothermal alteration and low temperature (seafloor) weathering of peridotites in the oceanic crust. In order to determine the conditions and processes resulting in the silicifica tion of peridotites at the Stalemate Fracture Zone, thermodynamic modeling accounting for the kinetics of mineral dissolution implemented in the GEOCHEQ program package was used in this study. The results of modeling allowed us to suppose that the geochemical and mineralogical effects observed in the silicified ser pentinized dunites of the Stalemate Fracture Zone are consequences of low temperature deserpentinization of oceanic materials under subaerial conditions.

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Stratigraphic numerical modelling of a carbonate platform on the Romanche transverse ridge, equatorial Atlantic

Cited by 19 publications

References 14 publications

Nonvolcanic tectonic islands in ancient and modern oceans

Nonvolcanic tectonic islands in ancient and modern oceans

Discovery of Late Jurassic fossils inside modern sediments at Gorringe Bank (Eastern Atlantic Ocean) and some geological implications.

Silicification of peridotites at the stalemate fracture zone (Northwestern Pacific): Reconstruction of the conditions of low-temperature weathering and tectonic interpretation

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