Gravity inversion predicts the nature of the Amundsen Basin and its continental borderlands near Greenland

Abstract

The high-Arctic Eurekan Orogeny was caused by a northward movement of Greenland relative to North America and Eurasia during the latest Cretaceous to late Eocene. While the Eurekan N–S shortening is well-documented in Ellesmere Island, North Greenland and Svalbard, the nature of the event is largely unknown in the ice-covered Arctic Ocean to the north of Greenland. In this contribution, we show that the tectono-physiographic evolution of the oceanic Amundsen Basin, the continental Lomonosov Ridge and the Morris Jesup Rise were all affected by significant Eurekan compression. We present the results of 3-D gravity inversion for predicting the sediment thickness and basement geometry within the Amundsen Basin and along its borderlands. We use the recently published LOMGRAV-09 gravity compilation and adopt a process-oriented iterative cycle approach that minimizes misfit between an Earth model and observations. The sensitivity of our results to lateral variations in depth and density contrast of the Moho is further tested by a stochastic inversion. Within their limitations, the approach and setup used herein provides the first detailed model of the sediment thickness and basement geometry in the Arctic Ocean north of Greenland. Our preferred result, using a C25 breakup scenario of the Amundsen Basin, correlates well with seismic observations along existing and several new marine seismic profiles. Breakup-related rift basins are predicted along the Lomonosov Ridge and a broad depocentre is predicted above high-relief basement in the central Amundsen Basin. Significantly, an up to 7 km deep elongated sedimentary basin is predicted along the northern edge of the Morris Jesup Rise. This basin continues into the Klenova Valley south of the Lomonosov Ridge and correlates with an offshore continuation of the Eurekan Mount Rawlinson Fault in Ellesmere Island. We compute the anomalous basement topography and show evidence of deformed oceanic and continental crust in relation to this fault zone (LKFZ), suggesting that pronounced Eurekan crustal shortening took place here.