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

Abstract

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 megascale 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.

Pliocene–Pleistocene glacimarine shelf to slope processes in the south‐western Barents Sea

“…Seismic data of even higher vertical and horizontal resolution than that of our seismic cubes (e.g. Bellwald & Planke, 2019; Bellwald et al., 2018, 2019; Waage et al., 2018) are required to more fully investigate the detailed form and timing of development of these slope features.…”

Characterization of a glacial paleo-outburst flood using high-resolution 3-D seismic data: Bjørnelva River Valley, SW Barents Sea

“…2b). These landforms have been analyzed in previous publications (Piasecka and others, 2016; Bellwald and others, 2019). The most striking structure imaged on the URU in the study area is a ~25 km long, southeast-northwest oriented channel belt system within an incised valley (Fig.…”

“…Wide plains are characteristic landscapes in Arctic regions and the dry and cold climate prevailing in these regions favors the build-up of permafrost (Kanevskiy and others, 2011; Schirrmeister and others, 2013). The Barents Sea at the time of the Bjørnelva River Valley formation is most likely characterized by such a climate and permafrost in the shale-dominated subsurface is discussed for landscape evolution of this paleo-surface (Bellwald and others, 2019). Our study shows that highly erosive fluvial events can occur in such dry and cold climates, a type of event also documented for the Coronation – Spondin Scabland of the Canadian Prairies (Sjogren and Rains, 1995).…”

“…Three-dimensional seismic data have given birth to the discipline of seismic geomorphology, which is described by Posamentier and others (2007) as ‘the application of analytical techniques pertaining to the study of landforms and to the analysis of ancient, buried geomorphological surfaces as imaged by 3D seismic data.’ Glacio-fluvial seismic geomorphology is defined here as the study of glaciofluvial systems (deposits and processes) using 3-D seismic images in map view. Applying the concept of seismic geomorphology allows to examine paleo-landscapes and to characterize geological features (Posamentier, 2001; Darmadi and others, 2007; Planke and others, 2017; Bellwald and others, 2019). Even if geological landscapes imaged by 3-D seismic data seem to occasionally express fossilized processes, the interpreted surface of this study (URU) is an amalgamated surface and can include expressions shaped by successive processes during different time intervals.…”

“…2a). The URU is an amalgamated erosional surface and the landforms identified at the URU provide Pleistocene analogues to present-day processes and climate changes (Tasianas and others, 2018; Bellwald and others, 2019). These landforms include mega-scale glacial lineations indicative of grounded ice, hill-hole pairs and depressions indicative of gas-hydrate melting and pockmarks indicative of fluid escape.…”