Reconstructing flood basalt lava flows using terrestrial laser scanning and GSI3D software

We present a novel application of terrestrial laser scanning (TLS) technology: to continental flood basalt provinces (CFBPs). CFBPs consist of sequences of basaltic lava flows, associated sediments and hyaloclastites, and can be several kilometres in thickness. Flood basalts are characterised in terms of key internal facies that occur at different levels within the sequence, which can vary both spatially and temporally. In the North Atlantic, potentially prospective sedimentary basins may lie under a CFBP (the North Atlantic Igneous Province). Lava flow sequences cause major problems with seismic imaging; however improved knowledge of lava flow sizes and structures can help improve the picture. We have used TLS equipment to capture data from outcrops of lava flow sequences within the North Atlantic Igneous Province to build true 3D geological models of flood basalt sequences. This allows us to obtain data on lava flow thickness, lateral extent and the ratio of flow crust to flow core, by identifying these key surfaces in the TLS data. We present examples from the Faroe Islands and the Isle of Skye, UK, acquired with a Riegl Z420i laser scanner. After identifying the key horizons in the TLS data, we use a novel method to extend these into 3D surfaces. The GSI3D software, developed by the British Geological Survey, is used to reconstruct the lava flow top surfaces. This software also allows palaeo-reconstruction between outcrops, as demonstrated in our case study from Skye. The final results are 3D block models, which are interrogated to give flow thicknesses, volumes and crust to core ratios. We will then use these data to investigate the effect of a sequence of basalt lava flows on subsurface seismic imaging.