Drilling on the Galicia Margin: Retrospect and Prospect

Boillot, G.; Winterer, Edward L.

doi:10.2973/odp.proc.sr.103.180.1988

Cited by 72 publications

(131 citation statements)

References 17 publications

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“…The best studied of these margins is the West Iberian margin (Figure 1), which has been the subject of several drilling legs [Boillot and Winterer, 1988 Serpentinization also requires peridotites at appropriate temperature conditions. The maximum temperature at which serpentine can develop varies somewhat depending on the serpentine mineral under discussion and the study carried out.…”

Section: Introductionmentioning

confidence: 99%

Rheological evolution during extension at nonvolcanic rifted margins: Onset of serpentinization and development of detachments leading to continental breakup

Pérez‐Gussinyé¹,

Reston²

2001

J. Geophys. Res.

285

215

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Abstract. Within the continent-ocean transition several nonvolcanic rifted margins exhibit a zone of partially serpentinized peridotites which continue under the thinned and faulted continental crust and are thought to represent subcontinental lithosphere serpentinized by contact with water. As water in sufficient volumes can only come from the surface, we suggest that a major condition for the onset of serpentinization is the embrittlement of the entire crust during progressive extension and hence the development of active crustal penetrating faults acting as fluid conduits. We investigate this possibility by modeling the rheological evolution of the lithosphere during extension and hence determining at what stretching factors the lower crust enters the brittle regime for a variety of different strain rates and lower crustal rheologies. Using an initial thermal structure appropriate for nonvolcanic margins, we find that the entire crust becomes brittle at stretching factors of between -3 and 5, depending on the strain rate. This compares well with the thickness of the crust observed just landward of the onset of partially serpentinized peridotites west of Iberia. The predicted thickness of the serpentinized peridotites (depth of the thermal limit of serpentinite stability beneath the crust-mantle boundary) also compares reasonably well with their observed thickness. As serpentinites are characterized by low friction coefficients, we suggest that the onset of mantle serpentinization controls the development of decollements at the crust-mantle boundary such as the S and H reflectors west of Iberia (leading to crustal separation). The development of thick serpentinites probably contributes to the weakening of the upper lithosphere and hence the localization of final breakup.

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Section: Introductionmentioning

confidence: 99%

Rheological evolution during extension at nonvolcanic rifted margins: Onset of serpentinization and development of detachments leading to continental breakup

Pérez‐Gussinyé¹,

Reston²

2001

J. Geophys. Res.

285

215

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“…We associate the change of tectonic style at this unconformityfrom a tectonically active to a passive mode-with a decline in stress regimes as the continental crust between Flemish Cap and Galicia Bank separated and seafloor spreading began in this region in the late Aptian. A similar unconformity can be identified on seismic data from Galicia Bank (Boillot, Winterer, et al, 1987), although the existence of this unconformity has not been confirmed by drilling. Site 641 on Galicia Bank penetrated this seismic horizon and found the strata to be conformable with no lacuna (Boillot, Winterer, et al, 1987).…”

Section: Tectonic Frameworkmentioning

confidence: 65%

“…A similar unconformity can be identified on seismic data from Galicia Bank (Boillot, Winterer, et al, 1987), although the existence of this unconformity has not been confirmed by drilling. Site 641 on Galicia Bank penetrated this seismic horizon and found the strata to be conformable with no lacuna (Boillot, Winterer, et al, 1987). The only change was lithologic, with an upward transition from conglomeratic and pebbly beds to shales across the seismic event.…”

Section: Tectonic Frameworkmentioning

confidence: 65%

“…The only change was lithologic, with an upward transition from conglomeratic and pebbly beds to shales across the seismic event. This stratigraphic level has been interpreted by Boillot, Winterer, et al (1987) as representative of the post-rift unconformity on Galicia Bank, and it has been dated paleontological^ as occurring at the Aptian/Albian boundary. Similarly, the outer Carson Basin stratal relations at the mid-Cretaceous unconformity are paraconformable in places.…”

Section: Tectonic Frameworkmentioning

confidence: 92%

“…These tectonic conditions are similar to Figure 12. Stratigraphic diagrams for Carson Basin and Galicia Bank, compiled from Jansa et al (1980b) and Boillot, Winterer, et al (1987). 801 MESOZOIC-CENOZOIC GEOLOGY OF EASTERN MARGIN GRAND BANKS those in the outer Carson Basin beneath the continental slope and rise.…”

Section: Tectonic Frameworkmentioning

confidence: 99%

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Mesozoic-Cenozoic Geology of the Eastern Margin of the Grand Banks and Its Relation to Galicia Bank

Grant¹,

Jansa²,

McAlpine³

et al. 1988

Proceedings of the Ocean Drilling Program

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Late Paleozoic reconstructions of the North Atlantic juxtapose the eastern margin of the Grand Banks with the continental margin off Iberia. Comparison of the geology of the Grand Banks region with results from ODP Leg 103 on the Galicia margin improves our understanding of the Mesozoic-cenozoic tectonic evolution of these regions and provides new constraints on pre-drift fits.The Grand Banks region is underlain by Paleozoic and Precambrian rocks of the Appalachian Orogen, which were rifted, eroded, and buried during Mesozoic and Cenozoic tectonic episodes related to formation of the North Atlantic Ocean and the Labrador Sea. The Carson Basin along the eastern margin of the Grand Banks contains Triassic and Jurassic evaporites overlain by Jurassic and Cretaceous carbonate and clastic rocks that were deeply eroded during the mid-Cretaceous. This unconformity is overlain by a comparatively thin and undeformed sequence of Cretaceous-Tertiary fine-grained marine elastics. Since the mid-Cretaceous, the outer portion of the Carson Basin has subsided to oceanic depths and now underlies the slope-rise zone. Comparison of the seismic stratigraphy of the Carson Basin with that of the Galicia margin indicates similar tectonic histories and depositional environments from Triassic to Tertiary time. Seismic-reflection data have been used to map the minimum seaward extent of continental crust, and this boundary lies approximately along a "headland to headland" line between the Newfoundland Ridge and Flemish Cap. Regional juxtaposition of these margin segments is geologically reasonable, but the evidence for continental crust beneath the slope and rise southeast of the Grand Banks precludes fitting Galicia Bank in this zone.

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Insights into exhumation and mantle hydration processes at the Deep Galicia margin from a 3D high-resolution seismic velocity model

Boddupalli

Minshull

Klaeschen³

et al. 2022

Preprint

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High-resolution velocity models developed using full waveform inversion (FWI) are capable of imaging fine details of the nature and structure of the subsurface. Using a 3D FWI velocity model of hyper-thinned crust at the Deep Galicia Margin (DGM), we constrain the nature of the crust at this margin by comparing its velocity structure with those in other similar tectonic settings. Velocities representative of both the upper and lower continental crust are present in this hyper-thinned crust. However, unlike in many other rifted margin settings, there is no clear evidence for distinct upper and lower crustal layers within the hyperextended crust. Our velocity model also shows evidence for exhumation of the lower crust under the footwalls of fault blocks to accommodate the extension. We used our model to generate a serpentinization map for the uppermost mantle at the DGM, at a depth of 100 ms (~340m) below the S-reflector, a low-angle detachment that marks the base of the crust at this margin. Based on this map, we propose that serpentinization began during rifting and continued into a postrift phase until the faults were sealed. We find a weak correlation between the fault heaves and the degree of serpentinization beneath the hanging-wall blocks, indicating that serpentinization was controlled by a complex crosscutting and unrecognized faulting during and after rifting. A good match between topographic highs of S and local highly serpentinized areas of mantle suggests that the serpentinization process resulted in variable uplift of the S-surface.

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Drilling on the Galicia Margin: Retrospect and Prospect

Cited by 72 publications

References 17 publications

Rheological evolution during extension at nonvolcanic rifted margins: Onset of serpentinization and development of detachments leading to continental breakup

Rheological evolution during extension at nonvolcanic rifted margins: Onset of serpentinization and development of detachments leading to continental breakup

Mesozoic-Cenozoic Geology of the Eastern Margin of the Grand Banks and Its Relation to Galicia Bank

Insights into exhumation and mantle hydration processes at the Deep Galicia margin from a 3D high-resolution seismic velocity model

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