Publication Date:
2017-06-10
Description:
We studied the 3-D shear-wave velocity ( V s ) structure in the Gulf of St. Lawrence (GSL) and adjacent onshore areas to 20 km depth by inverting Rayleigh-wave dispersion extracted from the vertical components of continuous ambient seismic noise waveforms. The region is divided into three broad zones based on their V s characteristics. In the northwest, the Grenville Province (i.e., the exposed edge of predominantly Middle-Proterozoic Laurentian crust) is dominated by high- V s , except for well-known anorthosite sites, which are characterized by relatively lower- V s . In contrast, the central segment of the GSL region corresponds to a belt with generally low- V s at upper-crustal levels. In the southeastern part of the GSL, prominent low- V s in the uppermost-crust are found to coincide with locations of subsidiary basins of the Canadian Maritime Basin, while higher- V s characterize the accreted Appalachian terranes where they are exposed on land. The Grenville Province is wedged out at depth by the Red Indian Line, which is the suture between composite-Laurentia and peri-Godwanan Ganderia in the Canadian Appalachians. The geometry and V s characteristics of the south-easternmost peri-Gondwanan terranes of Avalonia and Meguma, suggest that they may be fully or partially structurally overlying a basement with distinct seismic characteristics, which could be a vestige of the West-African craton that was under-thrust beneath composite-Laurentia during the terminal Alleghenian continent-continent collision. In the middle of the GSL, the 3-D geometry of the Canadian Maritimes sedimentary basins overlying the Appalachian terranes shows that the depth to the top of basement is in excess of 8 km.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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