Large variations in lithospheric thickness of western Laurentia:Tectonic inheritance or collisional reworking?
Date
2015-09
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Abstract
The ca. 2.0–1.8 Ga tectonic assembly of Laurentia provides a record of complex processes resulting in amalgamation of distinct lithospheric domains. In global and continental-scale teleseismic tomographic models, however, the subcontinental lithosphere beneath western Laurentia appears to have a deceptively simple structure that lacks a clear correlation with mapped crustal domains. Here we present a new shear-velocity model of the upper mantle beneath western Laurentia through Rayleigh-wave tomography, using data from several newly deployed broadband seismic arrays. Our models show prominent heterogeneities that appear to correlate well with crustal domains and other geophysical observations. The tomographic results delineate high-velocity keel-shaped anomalies beneath the Archean Hearne Province and the Paleoproterozoic Buffalo Head Terrane; these features are inferred to extend to depths of up to 260 km and likely represent ancient thick cratonic roots, whereas relatively thin lithosphere characterizes the adjacent Wabamun domain and Medicine Hat Block. A regional isostatic residual gravity anomaly in the foreland of the Cretaceous–Paleocene southern Canadian Rockies coincides with an area of inferred thick lithosphere in the Hearne Province, suggesting that along-strike variations in flexural rigidity correlate with lithospheric thickness. Taken together, our results suggest that high-amplitude basal topography of the lithosphere–asthenosphere boundary beneath cratons reflects a complex lithospheric evolution that combines effects of both tectonic inheritance and collisional reworking.
Description
Post-print version of article deposited according to Elsevier open access agreement: https://www.elsevier.com/about/open-science/open-access#greenOA
Keywords
Western Laurentia, Lithospheric evolution, Cratonic keel, Lithosphere-asthenosphere boundary, Surface-wave tomography
Citation
Bao, X., & Eaton, D. W. (2015). Large variations in lithospheric thickness of western Laurentia: Tectonic inheritance or collisional reworking?. Precambrian Research, 266, 579-586.