Crustal Heterogeneity Onshore Spitsbergen: Data Integration and Forward Modeling of Potential Field Data

Abstract

The Svalbard archipelago is well-known for its outcropping geology, but its subsurface geometry and physical properties are less well constrained. To address this knowledge gap, a multidisciplinary approach has been applied to integrate potential field data with seismic reflection profiles, exploration boreholes and geology. We constructed five 2D gravity and magnetic forward models along pre-existing seismic lines in central Spitsbergen, utilizing newly acquired ground-borne gravity, helicopter-borne magnetic, and regional gridded potential field data. Specifically, we focused on characterizing the geophysical signature of the pre-Devonian basement composition and topography, position of the Billefjorden Fault Zone (BFZ), and the magmatic bodies related to the High Arctic Large Igneous Province (HALIP). Regional trends show a 15 km wide NNW-SSE trending magnetic and gravity high east of the BFZ and a long-wavelength elliptical magnetic anomaly of ca. 50 km diameter below central Isfjorden with no anomalous gravity response. We observe outcropping igneous rocks and interpret HALIP-related igneous sills on 2D seismic data in this region matching the short-wavelength signal. Our models show that most of the gravity signal is related to the arrangements of the sedimentary basins and the influence of the BFZ on the basement topography. Large lateral intra-basement magnetic susceptibility contrasts and a deep magnetic source were necessary to fit the magnetic signal, indicating basement heterogeneity and locally the influence of magmatic bodies.