Elastic thickness estimates at northeast passive margin of North America and its implications

Abstract

Global estimates of the elastic thickness (Te) of the structure of passive continental margins show wide and varying results owing to the use of different methodologies. Earlier estimates of the elastic thickness of the North Atlantic passive continental margins that used flexural modelling yielded a Te value of ∼20-100 km. Here, we compare these estimates with the Te value obtained using orthonormalized Hermite multitaper recovered isostatic coherence functions. We discuss how Te is correlated with heat flow distribution and depth of necking. The E-W segment in the southern study region comprising Nova Scotia and the Southern Grand Banks show low Te values, while the zones comprising the NE-SW zones, viz., Western Greenland, Labrador, Orphan Basin and the Northern Grand Bank show comparatively high Te values. As expected, Te broadly reflects the depth of the 200-400 • C isotherm below the weak surface sediment layer at the time of loading, and at the margins most of the loading occurred during rifting. We infer that these low Te measurements indicate Te frozen into the lithosphere. This could be due to the passive nature of the margin when the loads were emplaced during the continental break-up process at high temperature gradients.

India–Madagascar paleo-fit based on flexural isostasy of their rifted margins

“…They iteratively compared the calculated gravity anomaly to the observed free-air gravity anomaly to derive a best-fit Te structure that shows a significant variation of 0 b Te b 40 km, which they attributed to strength variation in the rifted lithosphere. Several studies revealed crustal thinning and depth of necking as appropriate parameters to predict the flexural response of lithospheric stretching (Braun and Beaumont, 1989;Fourno and Roussel, 1994;Ratheesh Kumar et al, 2011). Ratheesh used the orthonormalized Hermite multitaper method to estimate Te along the northeastern passive margin of North America, and suggested that low-Te values were indicative of the passive nature of the margin when loads were emplaced during the continental break-up process at hightemperature gradients.…”

Moho depth and equivalent elastic thickness of the lithosphere over the Vema Channel: A new evidence of an aborted ridge

“…The total equivalent topography ( Fig. 4), defined as the height or depth that the crust will assume in the absence of water and under isostatic conditions (Kumar et al, 2011), is calculated with equation 4.…”