Structural and fluid-migration control on hill-hole pair formation: Evidence from high-resolution 3D seismic data from the SW Barents Sea

Hill-hole pairs are subglacial landforms consisting of thrust-block hills and associated source depressions. Formed by evacuation of material where ice sheets have been locally frozen to the substrate, they give insights into paleo-ice-sheet dynamics. The aim of this study was to document the relationships between ancient hill-hole pairs identified on a buried glacial unconformity with the structure of the underlying sedimentary deposits, and then to determine if the basin geology and glacial fluid migration pathways promoted local subglacial freeze-on during the hill-hole pair formation. The study is based on seismic geomorphological interpretation of four high-resolution 3D seismic cubes covering an area of 800 km2 in the SW Barents Sea, and fluid seepage data from 37 gravity cores. The seismic datasets allowed the identification of 55 hill-hole pairs along the buried unconformity. The hills are characterized by chaotic to homogenous seismic facies forming up to 19 m high mounds, each covering areas of 2000–644,000 m2. The holes form depressions between 1 and 44 m deep and 2000–704,000 m2 in areal extent, which cut into preglacial Mesozoic bedrock and later infilled by glacial till. The holes are often found above fault terminations. High-amplitude reflections identified along the faults and in the strata below the holes are interpreted as shallow gas migrating upward towards the glacial unconformity. Geochemical data of the seabed sediment cores further indicates an association between hill-hole pair occurrence and present-day thermogenic hydrocarbon seepage. The hill-hole pairs geometries were also used to identify five paleo-ice-flow directions along the glacial unconformity. These ice flows exhibit polythermal regimes, and four of them are parallel to ice-stream flow sets interpreted from glacial lineations. The integrated interpretation supports localized fault-related basal freezing of the Barents Sea Ice Sheet which resulted in the formation of hill-hole pairs when the ice sheet moved. In this context, the faults functioned as migration pathways for deep thermogenic fluids, possibly sourced from leaking Jurassic reservoirs.>p> This study highlights the importance of the underlying geology for ice-sheet dynamics: While hill-hole pairs above glacial till appear to be commonly associated with dispersed gas hydrates, hill-hole pairs above bedrock additionally indicate a link to underlying fault systems and hydrocarbon reservoirs. Freeze-on of underlying bedrock to the basal ice along the strike of faults in sedimentary bedrock explains deeper hill-hole pairs with smaller extents along the glacial unconformity compared to areally larger but shallow hill-hole pairs detected above glacial till on modern seabeds. Such close association between paleo-thermogenic gas seepage and the location of hill-hole pairs strongly support that hill-hole pairs are excellent markers revealing exit points of fluid migration pathways in petroleum system models

The geological implications of the upper seismic unit, southeastern Barents Sea

An upper Quaternary seismic unit has been mapped to the east and southeast of Bjern~yrennain the Barents Sea. The unit is dcfined by interpretation of shallow seismic (sparker) data, and occurs as an upper, seismically transparent sequence in the Quaternary succcssion. Discontinuous internal reflections do, however, occasionally occur, especially in the lower part of the unit. The sediments in the unit are interpreted to be of a glaciogenic origin and they most likely consist mainly of tlll

Chronotherapy for patients with a depressive episode treated in a public outpatient mental healthcare clinic in Norway: protocol for a randomised controlled trial

Introduction Depression is highly prevalent in outpatients receiving treatment for mental disorders. Treatment as usual (TAU) usually consists of either psychotherapy and/or antidepressant medication and often takes several weeks before clinical effect. Chronotherapy, consisting of sleep deprivation, sleep-wake phase advancement and stabilisation, and light therapy, is a possible addition to TAU that may decrease the time to treatment response. This randomised controlled trial will examine the benefits of adding chronotherapy to TAU compared with TAU alone.Methods and analysis The trial will include 76 participants with a depressive episode who initiate outpatient treatment at a secondary mental healthcare outpatient clinic at St. Olavs University Hospital. Participants will be randomly allocated 1:1 to either chronotherapy in addition to TAU or TAU alone. Assessments will be performed at baseline, day 3, day 4, day 7, day 14 and weeks 4, 8, 24 and 52, in addition to longer-term follow ups. The main outcome is difference in levels of depressive symptoms after week 1 using the Inventory of Depressive Symptomatology Self-Report. Secondary outcomes include levels of depressive symptoms at other time points, as well as anxiety, health-related quality of life and sleep assessed through subjective and objective measures.Ethics and dissemination The study protocol has been approved by the Regional Committee for Medical Research Ethics Central Norway (ref: 480812) and preregistered at ClinicalTrials.gov (ref: NCT05691647). Results will be published via peer-reviewed publications, presentations at research conferences and presentations for clinicians and other relevant groups. The main outcomes will be provided separately from exploratory analysis.Trial registration number NCT05691647