High-resolution landform assemblage along a buried glacio-erosive surface in the SW Barents Sea revealed by P-Cable 3D seismic data

摘要

The Quaternary sedimentary record in the Arctic captures a diverse and evolving range of landscapes reflecting climate changes. Here we study the geological landform assemblage of the Upper Regional Unconformity (URU) in the SW Barents Sea. The aims are (i) to characterize buried geological landforms on a meter-scale resolution, (ii) to understand their link with underlying structures, and (iii) to reconstruct paleo-ice-sheet dynamics and configurations. The data consist of a high-resolution three-dimensional (3D) P-Cable seismic cube with an extent of c. 200 km(2) and an inline separation of 6 m. Dominant frequencies of c. 150 Hz allow to image landforms at URU with a vertical resolution of 1-5 m and a horizontal resolution of 3-6 m. We conduct detailed horizon-picking and seismic attribute analysis of the buried URU horizon. We identified four sets of mega-scale glacial lineations, and shear band ridges located to the west of a shear margin moraine. Other characteristic features include hill-hole pairs, transverse ridges, rhombohedral ridges and depressions, iceberg ploughmarks and pockmarks. Polygonal faults below URU and deeper faults have a strong effect on the location of structures observed on URU. Bedrock packages deformed down to 30 m below URU and up to 5 m-high transverse ridges at URU are imprints of glacio-tectonic activity. Deformed strata below URU indicate normal faulting superimposed by glaciotectonic deformation. The four sets of mega-scale glacial lineations indicate four streaming events with thawed glacial beds, with shear band ridges forming in the shearing zone during one of these streaming events. Hill-hole pairs and rhombohedral ridges are frozen-bed features which indicate a polythermal regime at the base of the Barents Sea Ice Sheet during multiple streaming phases. This study therefore shows that paleo-ice streams have been temporarily frozen to the ground in the SW Barents Sea, and that landforms evidencing this freezing are associated with underlying faults. (C) 2019 Elsevier B.V. All rights reserved.