Publication Date:
2022-05-25
Description:
Author Posting. © Blackwell, 2006. This is the author's version of the work. It is posted here by permission of Blackwell for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 167 (2006): 127-156, doi:10.1111/j.1365-246X.2006.02988.x.
Description:
A P-wave velocity model along a 565-km-long profile across the Grand
Banks/Newfoundland basin rifted margin is presented. Continental crust ~36-kmthick
beneath the Grand Banks is divided into upper (5.8-6.25 km/s), middle (6.3-
6.53 km/s) and lower crust (6.77-6.9 km/s), consistent with velocity structure of
Avalon zone Appalachian crust. Syn-rift sediment sequences 6-7-km thick occur in
two primary layers within the Jeanne d’Arc and the Carson basins (~3 km/s in upper
layer; ~5 km/s in lower layer). Abrupt crustal thinning (Moho dip ~ 35º) beneath the
Carson basin and more gradual thinning seaward forms a 170-km-wide zone of rifted
continental crust. Within this zone, lower and middle continental crust thin
preferentially seaward until they are completely removed, while very thin (〈3 km)
upper crust continues ~60 km farther seaward. Adjacent to the continental crust, high
velocity gradients (0.5-1.5 s-1) define an 80-km-wide zone of transitional basement
that can be interpreted as exhumed, serpentinized mantle or anomalously thin
oceanic crust, based on its velocity model alone. We prefer the exhumed-mantle
interpretation after considering the non-reflective character of the basement and the
low amplitude of associated magnetic anomalies, which are atypical of oceanic crust.
Beneath both the transitional basement and thin (〈6 km) continental crust, a 200-kmwide
zone with reduced mantle velocities (7.6-7.9 km/s) is observed, which is
interpreted as partially (〈10%) serpentinized mantle. Seaward of the transitional
basement, 2- to 6-km-thick crust with layer 2 (4.5-6.3 km/s) and layer 3 (6.3-7.2
km/s) velocities is interpreted as oceanic crust. Comparison of our crustal model
with profile IAM-9 across the Iberia Abyssal Plain on the conjugate Iberia margin
suggests asymmetrical continental breakup in which a wider zone of extended
continental crust has been left on the Newfoundland side.
Description:
This research was supported by National Science Foundation (NSF)
grants OCE-9819053 and OCE-0326714, by the National Sciences and Engineering
Research Council of Canada (NSERC), and by the Danish National Research
Foundation. B. Tucholke also acknowledges support from the Henry Bryant Bigelow
Chair in Oceanography from Woods Hole Oceanographic Institution.
Keywords:
Continental margins
;
Crustal structures
;
Refraction seismology
;
Rifted margins
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
28777307 bytes
Format:
application/pdf
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