Latitudinal variability in the Quaternary development of the Eurasian ice sheets—Evidence from the marine domain

Here we present the first compilation of sediment volumes, sedimentation rates, and chronology of Quaternary sediment packages along the entire marine margin of the Eurasian ice sheets (EurIS; British–Irish, Kara–Barents Sea–Svalbard, and Fennoscandian). This compilation allows for a subdivision of the EurIS development into three phases (2.6–1.5 Ma, 1.5–0.78 Ma, and 0.78–0 Ma). At the start of the Quaternary, sedimentation rates increased, relative to pre-Quaternary rates, by an order of magnitude. This abruptness in rate change excludes tectonic raising of landmasses as the main factor, but more likely reflects climate change through increased glacial erosion. The sediment distribution data suggest that the Kara–Barents Sea–Svalbard Ice Sheet (KBSIS) already was quite large at the beginning of the Quaternary, and well before 1.5 Ma it extended to the shelf edge and coalesced with the Fennoscandian Ice Sheet (FIS), which prior to 1.5 Ma most likely was located near the coast. Large ice streams and intense glacial erosion characterized the KBSIS in the 1.5–0.78 Ma time period, whereas the FIS at that time extended farther out on the continental shelf. After 0.78 Ma, a north-south change in EurIS development occurred. In the FIS and the British–Irish Ice Sheet (BIIS), large ice streams developed and shelf-edge glaciations occurred nearly 1 m.y. later compared to the KBSIS. The FIS and BIIS also repetitively coalesced in the North Sea. A significant drop in sediment input along the KBSIS marine margin, to the lowest Quaternary level, suggests a less erosive KBSIS.publishedVersio

Late Plio-Pleistocene evolution of the Eurasian Ice Sheets inferred from sediment input along the northeastern Atlantic continental margin

High-latitude marine sediment archives may contain information about the configuration and dynamics of former ice sheets, paleoclimate and the intensity of glacial erosion and uplift in catchment areas. Compiling information on the Late Cenozoic sediment packages along the NE Atlantic continental margin shows that large sediment volumes (c. 982 × 103 km3) were deposited during the Northern Hemisphere Glaciations (NHG), and that significant spatial and temporal variations in sediment input occurred during three distinct NHG Phases. NHG Phase I (2.7–1.5 Ma) was characterized by high sediment input to the trough mouth fan systems offshore Svalbard, suggesting strong glacial erosion and the development of large ice sheets over Svalbard. Comparatively moderate sedimentation and erosion rates are observed along the SW Barents Sea and the Norwegian margins during NHG Phase I. This indicates more restricted ice sheets over Fennoscandia compared to Svalbard, although periods of shelf edge glaciation most likely occurred. The most prominent overall margin development occurred during NHG Phase II (1.5–0.8 Ma), when recurrent large-scale, continental shelf edge, glaciations are suggested for the entire Eurasian Ice Sheets (EurIS). Compared to NHG Phase I, average sedimentation rates are three (91 cm/kyr) and two times higher (20 cm/kyr), respectively, in the Kara-Barents Sea-Svalbard Ice Sheet (KBSIS) region and the Fennoscandian/British-Irish Ice Sheet (FIS/BIIS) region. During NHG Phase III (0.8–0 Ma), sediment input decreases considerably (73%) along the marine margin of the KBSIS, while increasing significantly (62%) from the FIS/BIIS, in comparison to NHG Phase II. These estimates mark a major transition in the evolution of the EurIS, where the submergence below sea level of the Barents Sea region and the initiation of the Norwegian Channel Ice Stream are suggested to be key factors in this change. Furthermore, the submergence of the Barents Sea region affected ocean-atmosphere coupling and circulation which may have had a potential impact on global long-term climate change.publishedVersio

The Cenozoic western Svalbard margin: sediment geometry and sedimentary processes in an area of ultraslow oceanic spreading

The northeastern high-latitude North Atlantic is characterised by the Bellsund and Isfjorden fans on the continental slope off west Svalbard, the asymmetrical ultraslow Knipovich spreading ridge and a 1,000 m deep rift valley. Recently collected multichannel seismic profiles and bathymetric records now provide a more complete picture of sedimentary processes and depositional environments within this region. Both downslope and alongslope sedimentary processes are identified in the study area. Turbidity currents and deposition of glacigenic debris flows are the dominating downslope processes, whereas mass failures, which are a common process on glaciated margins, appear to have been less significant. The slide debrite observed on the Bellsund Fan is most likely related to a 2.5–1.7 Ma old failure on the northwestern Barents Sea margin. The seismic records further reveal that alongslope current processes played a major role in shaping the sediment packages in the study area. Within the Knipovich rift valley and at the western rift flank accumulations as thick as 950–1,000 m are deposited. We note that oceanic basement is locally exposed within the rift valley, and that seismostratigraphic relationships indicate that fault activity along the eastern rift flank lasted until at least as recently as 1.5 Ma. A purely hemipelagic origin of the sediments in the rift valley and on the western rift flank is unlikely. We suggest that these sediments, partly, have been sourced from the western Svalbard—northwestern Barents Sea margin and into the Knipovich Ridge rift valley before continuous spreading and tectonic activity caused the sediments to be transported out of the valley and westward.publishedVersio

Seal bypass at the Giant Gjallar Vent (Norwegian Sea): indications for a new phase of fluid venting at a 56-Ma-old fluid migration system

Highlights: • The Giant Gjallar Vent is still active in terms of fluid migration and faulting. • The Base Pleistocene Unconformity acts as a seal to upward fluid migration. • Seal bypass in at least one location leads to a new phase of fluid venting. The Giant Gjallar Vent (GGV), located in the Vøring Basin off mid-Norway, is one of the largest (~ 5 × 3 km) vent systems in the North Atlantic. The vent represents a reactivated former hydrothermal system that formed at about 56 Ma. It is fed by two pipes of 440 m and 480 m diameter that extend from the Lower Eocene section up to the Base Pleistocene Unconformity (BPU). Previous studies based on 3D seismic data differ in their interpretations of the present activity of the GGV, describing the system as buried and as reactivated in the Upper Pliocene. We present a new interpretation of the GGV’s reactivation, using high-resolution 2D seismic and Parasound data. Despite the absence of geochemical and hydroacoustic indications for fluid escape into the water column, the GGV appears to be active because of various seismic anomalies which we interpret to indicate the presence of free gas in the subsurface. The anomalies are confined to the Kai Formation beneath the BPU and the overlying Naust Formation, which are interpreted to act as a seal to upward fluid migration. The seal is breached by focused fluid migration at one location where an up to 100 m wide chimney-like anomaly extends from the BPU up to the seafloor. We propose that further overpressure build-up in response to sediment loading and continued gas ascent beneath the BPU will eventually lead to large-scale seal bypass, starting a new phase of venting at the GGV

Rapid ice sheet retreat triggered by ice stream debuttressing: Evidence from the North Sea

Using high-resolution bathymetric and shallow seismic data from the North Sea, we have mapped hitherto unknown glacial landforms that connect and resolve longstanding gaps in the Quaternary geological history of the basin. We use these data combined with published information and dates from sediment cores to reconstruct the extent of the Fennoscandian and British Ice Sheets (FIS and BIS) in the North Sea during the last phases of the last glacial stage. It is concluded that the BIS occupied a much larger part of the North Sea than previously suggested and that North Sea ice underwent a dramatic disintegration ~18,500 yr ago. This was triggered by grounding-line retreat of the Norwegian Channel Ice Stream, which debuttressed adjacent ice masses, and led to an unzipping of the BIS and FIS accompanied by drainage of a large ice-dammed lake. Our reconstruction of events provides an opportunity to improve understanding and modeling of the disintegration of marine-based ice sheets, and the complex interplay between ocean circulation and the cryosphere

Chronology of Early to Mid-Pleistocene sediments in the northern North Sea: New evidence from amino acid and strontium isotope analyses

Sediments deposited during glacial-interglacial cycles through the Early to Mid-Pleistocene in the North Sea are chronologically poorly constrained. To contribute to the chronology of these units, amino acid racemization (AAR) and strontium (Sr) isotope analyses have been performed on samples from four shallow borings and one oil well along a transect in the northern North Sea. D/L Asp (aspartic acid) values obtained through reverse-phase liquid chromatography in the benthic foraminiferal species Elphidium excavatum is focused on because of consistent results and a good stratigraphic distribution of this benthic species. For the Early Pleistocene, an age model for the well 16/1–8, from the central part of the northern North Sea based on Sr ages allows for dating of the prograding wedges filling the pre-Quaternary central basin. A regional calibration curve for the racemization of Asp in Elphidium excavatum is developed using published ages of radiocarbon-dated samples and samples associated with the previously identified Bruhnes/Matuyama (B/M) paleomagnetic boundary and a Sr age from this study. Based on all the available geochronological evidence, samples were assigned to marine oxygen isotope stages (MIS) with uncertainties on the order of 10–70 ka. Sr ages suggest a hiatus of <2 million years (Ma) possibly due to non-deposition or low sedimentation between the Utsira Formation (Pliocene) and the Early Pleistocene. An increase in sedimentation rates around 1.5 ± 0.07 Ma (∼MIS 51) may partly be due to sediment supply from rivers from the south-east and partly due to the extension of ice sheet around 1.36 ± 0.07 Ma from the Norwegian coast to the central North Sea. A possible basin-wide glaciation occurred around 1.1 Ma (∼ MIS 32) (upper regional unconformity/top of unit Q4 in this study), resulting in erosion and regional unconformity. Two interglacials in the Norwegian Channel have been dated: the Radøy Interglacial to 1.07 ± 0.01 Ma (possibly MIS 31, the ‘super interglacial’), and the Norwegian Trench Interglacial to 0.50 ± 0.02 Ma (possibly MIS 13). A massive till unit identified at the same stratigraphic level in all shallow borings may partly represent an extensive MIS 12 glaciation. This study shows that the combined use of amino acid racemization data and Sr isotope chronology can refine the chronological ambiguities of Quaternary North Sea sediments related partly to the impact of glacial processes.publishedVersio

An overview of the Upper Paleozoic-Mesozoic stratigraphy of the NE Atlantic region

This study describes the distribution and stratigraphic range of the Upper Paleozoic–Mesozoic succession in the NE Atlantic region, and is correlated between conjugate-margins and along the axis of the NE Atlantic rift system. The stratigraphic framework has yielded important new constraints on the timing and nature of sedimentary basin development in the NE Atlantic, with implications for rifting and the breakup of the Pangaean supercontinent. From a regional perspective, the Permian–Triassic succession records a northward transition from an arid interior to a passively-subsiding, mixed carbonate/siliciclastic shelf margin. A Late Permian–earliest Triassic rift pulse has regional expression in the stratigraphic record. A fragmentary paralic to shallow-marine Lower Jurassic succession reflects Early Jurassic thermal subsidence and mild extensional tectonism; this was interrupted by widespread Mid-Jurassic uplift and erosion, and followed by an intense phase of Late Jurassic rifting in some (but not all) parts of the NE Atlantic region. The Cretaceous succession is dominated by thick basinal-marine deposits, which accumulated within and along a broad zone of extension and subsidence between Rockall and NE Greenland. There is no evidence for a substantive and continuous rift system along the proto-NE Atlantic until the Late Cretaceous

The role of ocean and atmospheric dynamics in the marine-based collapse of the last Eurasian Ice Sheet

Information from former ice sheets may provide important context for understanding the response of today’s ice sheets to forcing mechanisms. Here we present a reconstruction of the last deglaciation of marine sectors of the Eurasian Ice Sheet, emphasising how the retreat of the Norwegian Channel and the Barents Sea ice streams led to separation of the British-Irish and Fennoscandian ice sheets at c. 18.700 and of the Kara-Barents Sea-Svalbard and Fennoscandian ice sheets between 16.000 and 15.000 years ago. Combined with ice sheet modelling and palaeoceanographic data, our reconstruction shows that the deglaciation, from a peak volume of 20 m of sea-level rise equivalent, was mainly driven by temperature forced surface mass balance in the south, and by Nordic Seas oceanic conditions in the north. Our results highlight the nonlinearity in the response of an ice sheet to forcing and the significance of ocean-ice-atmosphere dynamics in assessing the fate of contemporary ice sheets

Cognitive Trajectories in Older Patients with Cancer Undergoing Radiotherapy—A Prospective Observational Study

Cognitive function can be affected by cancer and/or its treatment, and older patients are at a particular risk. In a prospective observational study including patients 65 years referred for radiotherapy (RT), we aimed to investigate the association between patient- and cancer-related factors and cognitive function, as evaluated by the Montreal Cognitive Assessment (MoCA), and sought to identify groups with distinct MoCA trajectories. The MoCA was performed at baseline (T0), RT completion (T1), and 8 (T2) and 16 (T3) weeks later, with scores ranging between 0 and 30 and higher scores indicating better function. Linear regression and growth mixture models were estimated to assess associations and to identify groups with distinct MoCA trajectories, respectively. Among 298 patients with a mean age of 73.6 years (SD 6.3), the baseline mean MoCA score was 24.0 (SD 3.7). Compared to Norwegian norm data, 37.9% had cognitive impairment. Compromised cognition was independently associated with older age, lower education, and physical impairments. Four groups with distinct trajectories were identified: the very poor (6.4%), poor (8.1%), fair (37.9%), and good (47.7%) groups. The MoCA trajectories were mainly stable. We conclude that cognitive impairment was frequent but, for most patients, was not affected by RT. For older patients with cancer, and in particular for those with physical impairments, we recommend an assessment of cognitive function.This work was funded by Innlandet Hospital Trust, Norway. This research received no external funding.publishedVersio

Geriatric impairments are associated with reduced quality of life and physical function in older patients with cancer receiving radiotherapy - A prospective observational study

Introduction: Quality of life (QoL) and function are important outcomes for older adults with cancer. We aimed to assess differences in trends in patient-reported outcomes (PROs) during radiotherapy (RT) between (1) groups with curative or palliative treatment intent and (2) groups defined according to the number of geriatric impairments. Materials and methods: A prospective observational study including patients aged ≥65 years receiving curative or palliative RT was conducted. Geriatric assessment (GA) was performed before RT, and cut-offs for impairments within each domain were defined. Patients were grouped according to the number of geriatric impairments: 0, 1, 2, 3, and ≥ 4. Our primary outcomes, global QoL and physical function (PF), were assessed by The European Organisation for Research and Treatment of Cancer Quality-of-Life Core Questionnaire (EORTC) (QLQ-C30) at baseline, RT completion, and two, eight, and sixteen weeks later. Differences in trends in outcomes between the groups were assessed by linear mixed models. Results: 301 patients were enrolled, mean age was 73.6 years, 53.8% received curative RT. Patients receiving palliative RT reported significantly worse global QoL and PF compared to the curative group. The prevalence of 0, 1, 2, 3 and ≥ 4 geriatric impairments was 16.6%, 22.7%, 16.9%, 16.3% and 27.5%, respectively. Global QoL and PF gradually decreased with an increasing number of impairments. These group differences remained stable from baseline throughout follow-up without any clinically significant changes for any of the outcomes. Discussion: Increasing number of geriatric impairments had a profound negative impact on global QoL and PF, but no further decline was observed for any group or outcome, indicating that RT was mainly well tolerated. Thus, geriatric impairments per se should not be reasons for withholding RT. GA is key to identifying vulnerable patients in need of supportive measures, which may have the potential to improve treatment tolerance.publishedVersio