ArcCRUST: Arctic Crustal Thickness From 3‐D Gravity Inversion

Abstract

The ArcCRUST model consists of crustal thickness and estimated crustal thinning factors grids for the High Arctic and Circum‐Arctic regions (north of 67°N). This model is derived by using 3‐D forward and inverse gravity modeling. Updated sedimentary thickness grid, an oceanic lithosphere age model together with inferred microcontinent rifting ages, variable crystalline crust and sediment densities, and dynamic topography models constrain this inversion. We use published high‐quality 2‐D seismic crustal‐scale models to create a database of Depths to Seismic Moho (DSM) profiles. To check the quality of the ArcCRUST model, we have performed a statistical analysis of misfits between the ArcCRUST Moho depths and DSM values. Systematic analysis of the misfits within the Arctic sedimentary basins provides information about tectonic processes unaccounted by the assumed model of pure‐shear lithospheric extension. In particular, our model implies a less dense and/or thin mantle lithosphere underneath microcontinents in the deep Arctic Ocean where the ArcCRUST depth to Moho values exceed the DSM. A systematically larger gravity‐derived crustal thickness (~3 km) under the western and northern Greenland Sea points to a hotter upper mantle implied by the seismic tomography models in the North Atlantic.

High Arctic geopotential stress field and implications for geodynamic evolution

“…We compute the lithosphere-derived present-day stress field by calculating the geopotential stress field that results from lateral pressure differences in the lithosphere. The lithospheric density model used for calculating the geopotential energy (GPE) is a compilation of new data that includes sedimentary thickness, crustal thickness, dynamic topography (Lebedeva- Ivanova et al, 2015;2016) and the lithosphereasthenosphere boundary (LAB) (Schaeffer et al, submitted;Schaeffer & Lebedev, 2015b).…”

“…The spatial variation in such structures results in lateral variations in the integrated mass of the vertical columns driving pressure differences -the source of geopotential stresses. In this study we combine recent geophysical datasets for the whole High Arctic region, including a newly compiled crustal model (Lebedeva-Ivanova et al, 2015, 2016 and LAB depth model (Schaeffer et al, submitted;Schaeffer & Lebedev, 2015b). Together, these form the basis for our density model used to calculate geopotential energy and, ultimately, the corresponding geopotential stress field.…”

“…The crustal model of Lebedeva-Ivanova et al (2016) describes observed topography and bathymetry ( Fig. 1, left), thicknesses and densities for a sedimentary and a crustal layer from 68-90 °N (Fig.…”

“…Modifications were made at the boundaries in order to incorporate it into the global CRUST1.0 model (Laske et al, 2013). The Arctic model of Lebedeva-Ivanova et al (2016) shows sedimentary basins (Fig. 2, top left) with depths of 10 km and more in the southern Canada Basin/Beaufort-MacKenzie Sea (Stephenson et al, 1994b;Sippel et al, 2013), Chukchi Basin (Drachev, 2011) and in the eastern Barents Sea (Drachev et al, 2010;Minakov et al, 2012;Klitzke et al, 2015).…”

“…Such a pressure anomaly gives rise to dynamic topography. The Arctic crustal model from Lebedeva- Ivanova et al (2016) provides an estimate of dynamic topography. The model was translated into a sub-lithospheric pressure anomaly that is required to produce the resulting dynamic uplift or subsidence.…”