High Arctic geopotential stress field and implications for geodynamic evolution

Abstract

We use new models of crustal structure and the depth of the lithosphere-asthenosphere boundary to calculate geopotential energy and its corresponding geopotential stress field for the High Arctic. Palaeo-stress indicators such as dykes and rifts of known age are used to compare the present-day and palaeo stress field. When both stress fields coincide, a minimum age for the configuration of the lithospheric stress field may be defined. We identify three regions in which this is observed. In North Greenland and the eastern Amerasia Basin the stress field is likely the same as during the late Cretaceous. In western Siberia, the stress field is similar to that of the Triassic. The stress directions on the eastern Russian Arctic shelf and the Amerasia Basin are similar to that of the Cretaceous. The persistent misfit of the present stress field and Early Cretaceous dyke swarms associated with the High Arctic Large Igneous Province indicates a short-lived transient change of the stress field at the time of dyke emplacement. Most rifts in the Amerasia Basin coincide with the stress field, suggesting that dyking and rifting were unrelated. We present new evidence for dykes and a graben structure of Early Cretaceous age on Bennett Island.

Lithospheric Structure of Greenland From Ambient Noise and Earthquake Surface Wave Tomography

“…The velocity heterogeneity across the Labrador Sea and Baffin Bay may suggest lateral variations in lithospheric thickness, with thicker oceanic lithosphere to the north of the Davis Strait. These variations are consistent with regional tomography models (Lebedev et al, ; Schaeffer & Lebedev, ) and the lithosphere‐asthenosphere boundary depth model of Schiffer et al ().…”

“…In both cases and independent of potential temperature, thin lithosphere would cause elevated GHF in the region (e.g., Rogozhina et al, ; Rysgaard et al, ). The low‐velocity anomalies from CE Greenland are consistent with previous P and S waves tomography (Jakovlev et al, ; Lebedev et al, ; Mordret, ; Rickers et al, ; Schaeffer & Lebedev, , ) and with indications of lithospheric thinning in this region (Kumar et al, ; Schiffer et al, ). The presence of this mantle low‐velocity anomaly in a region of documented postrift uplift (Anell et al, ; Døssing et al, ; Japsen & Chalmers, ) and unusually high GIA uplift rates (e.g., +10 mm/year; Khan et al, ) could also be an evidence of low upper mantle viscosity and explain the mechanism for isostatic compensation in a region with no deep crustal roots.…”

“…From this region, relatively thick crust extends southward and eastward and coincides with part of the South Archean Block, Eastern Archean Block, and Nagssugtoqidian orogen. In northern Greenland, our model does not indicate crustal thinning as suggested by gravity‐based models (Braun et al, ; Petrov et al, ; Schiffer et al, ; Steffen et al, ) but is relatively consistent with surface wave‐based crustal thickness models (Darbyshire et al, ; Mordret, ). The high degree of heterogeneity in crustal thickness estimates in northern Greenland may be the result of the limited sensitivity of surface waves.…”

“…P wave receiver function measurements from Dahl‐Jensen, Larsen, et al () point toward a SW‐NE trending boundary separating Greenland into two distinct Proterozoic blocks with crustal thickness estimates ranging from 40–42 km in the north to 45–50 km in the south. Gravity models (Braun et al, ; Petrov et al, ; Schiffer et al, ; Steffen et al, ) correlate well with the seismically suggested north‐south divide with thicker crust in the southeast and thinner crust in the north. Gravity‐derived crustal thickness also tends to be relatively large in central‐eastern Greenland.…”

Mesozoic‐Cenozoic Regional Stress Field Evolution in Svalbard

“…Gabrielsen et al () document a dominant NNE‐SSW trending sub‐vertical joint set, in Tertiary strata (Figure a). This direction is also roughly aligned with the stress field modeled by Schiffer et al () and would be consistent with coupled dextral transpression.…”