Southeastern Arctic Ocean, seismic reflection images of cruise ark2018

In autumn 2018 a multichannel seismic reflection survey was performed in the southeastern part of the Amundsen Basin, on the Lomonosov Ridge and its transition to the Siberian Shelf. We present the new data, and a first glance at the findings, with the aim to enhance insights into the tectonic evolution, sedimentation history, and paleoceanography of the southeastern Arctic Ocean. Lines on the Lomonosov Ridge confirm the presence of 1600 m thick, undisturbed, parallel sedimentary layers. A prominent highamplitudereflector sequence within the strata can be used to directly correlate to previous seismostratigraphic models. A major aim of the expedition was the acquisition of cross lines relative to previous surveys covering the location of the upcoming IODP377 project. A 300 km long transect across the Amundsen Basin images a 3 km thick sedimentary sequence covering a rough acoustic basement. The highamplitudereflector sequence can also be traced in the basin, indicating widespread changes in tectonic and deposition conditions in the eastern Arctic Ocean. The crustal surface shows strong deformation, especially in the western part of the Basin, which can be associated with a reorganisation of tectonic plates accompanied by a significant decrease in spreading rates. A seamount, likely of a magmatic origin, was observed rising from the crust and penetrating all sedimentary layers. Dredgesampling on an outcrop at the western slope of the rise reveal a cover of consolidated sandand siltstones. Lines across the transition from the Lomonosov Ridge to the Laptev Sea Shelf image a more than 2 km thick sedimentary sequence overlying a rugged and faulted acoustic basement. At first glance, no indications of a larger transform fault can be detected, which could elucidate the tectonic relation between the ridge and the shelf. Several large mass wasting events or debris flows are indicated in the strata. An erosional channel with a sediment drift on its southern edge may provide clues to ocean current development

Initial opening of the Eurasian Basin, Arctic Ocean

Analysis of the transition from the NE Yermak Plateau into the oceanic Eurasian Basin sheds light on the Paleocene formation of this Arctic basin. Newly acquired multichannel seismic data with a 3600 m long streamer shot during ice-free conditions enables the interpretation of crustal structures. Evidence is provided that no major compressional deformation affected the NE Yermak Plateau. The seismic data reveal that the margin is around 80 km wide and consists of rotated fault blocks, major listric normal faults, and half-grabens filled with syn-rift sediments. Taking into account published magnetic and gravimetric data, this setting is interpreted as a rifted continental margin, implying that the NE Yermak Plateau is of continental origin. The transition from the Yermak Plateau to the oceanic Eurasian Basin might be located at a prominent basement high, probably formed by exhumed mantle. In contrast to the Yermak Plateau margin, the North Barents Sea continental margin shows a steep continental slope with a relatively abrupt transition to the oceanic domain. Based on one composite seismic line, it is speculated that the initial opening direction of the Eurasian Basin in the Arctic Ocean was highly oblique to the present day seafloor spreading direction

New reflection seismic profiles across the southern Amundsen Basin and Lomonosov Ridge, Arctic Ocean

In autumn 2018 a multichannel seismic reflection survey was performed in the southeastern part of the Amundsen Basin, on the Lomonosov Ridge and its transition to the Siberian Shelf. We present the new data, and a first glance at the findings, with the aim to enhance insights into the tectonic evolution, sedimentation history, and paleoceanography of the southeastern Arctic Ocean. Lines on the Lomonosov Ridge confirm the presence of 1600 m thick, undisturbed, parallel sedimentary layers. A prominent high amplitude reflector sequence within the strata can be directly correlated to previous seismo-stratigraphic models. A major aim of the expedition was the acquisition of cross lines relative to previous surveys covering the location of the upcoming IODP377 project. A 300 km long transect from the Gakkel Deep across the southeastern Amundsen Basin and over the Lomonosov Ridge images an up to 3 km thick sedimentary sequence covering a rough acoustic basement in the Amundsen Basin. A prominent unconformity can be traced trough the basin, indicating widespread changes in tectonic and deposition conditions in the Arctic Ocean. The crustal surface shows strong deformation, in partucular in the western part of the basin. Tentatively we link the deformation to a reorganisation of tectonic plates accompanied by a significant decrease in spreading rates. Tectonics led to uplift of the oceanic crust and the overlaying lowermost sedimentary sequence which are now exposed at a seamount like structure piercing through younger sediments. The structure was sampled successfully by employment of a dredge. The exposed rocks directly overlaying the oceanic crust consist of consolidated sand- and siltstones. Lines across the transition from the Lomonosov Ridge to the Laptev Sea Shelf image a more than 2 km thick sedimentary sequence overlying a rugged and faulted acoustic basement. At first glance, no indications of a larger transform fault are found, which could elucidate the tectonic relation between the ridge and the shelf

New reflection seismic profiles across the southern Amundsen Basin and Lomonosov Ridge, PS115-2

In autumn 2018 a multichannel seismic reflection survey was performed in the southeastern part of the Amundsen Basin, on the Lomonosov Ridge and its transition to the Siberian Shelf. We present the new data, and a first glance at the findings, with the aim to enhance insights into the tectonic evolution, sedimentation history, and paleoceanography of the southeastern Arctic Ocean. Lines on the Lomonosov Ridge confirm the presence of 1600 m thick, undisturbed, parallel sedimentary layers. A prominent high amplitude reflector sequence within the strata can be directly correlated to previous seismo-stratigraphic models. A 300 km long transect from the Gakkel Deep across the southeastern Amundsen Basin and over the Lomonosov Ridge images an up to 3 km thick sedimentary sequence covering a rough acoustic basement in the Amundsen Basin. A prominent unconformity can be traced trough the basin, indicating widespread changes in tectonic and deposition conditions in the Arctic Ocean. The crustal surface shows strong deformation, in partucular in the western part of the basin. Tentatively we link the deformation to a reorganisation of tectonic plates accompanied by a significant decrease in spreading rates. Tectonics led to uplift of the oceanic crust and the overlaying lowermost sedimentary sequence which are now exposed at a seamount like structure piercing through younger sediments. The structure was sampled successfully by employment of a dredge. The exposed rocks directly overlaying the oceanic crust consist of consolidated sand- and siltstones. Profiles across the transition from the Lomonosov Ridge to the Laptev Sea Shelf image a more than 2 km thick sedimentary sequence overlying a rugged and faulted acoustic basement. At first glance, no indications of a larger transform fault are found, which could elucidate the tectonic relation between the ridge and the shelf

Evidence for mantle exhumation since the early evolution of the slow-spreading Gakkel Ridge, Arctic Ocean

We study the basement configuration in the slow-spreading Eurasia Basin, Arctic Ocean. Two multichannel seismic (MCS) profiles, which we acquired during ice-free conditions with a 3600 m long streamer, image the transition from the North Barents Sea Margin into the southern Eurasia Basin. The seismic lines resolve the up to 5000 m thick sedimentary section, as well as the crustal architecture of the southern Eurasia Basin along 120 km and 170 km, respectively. The seismic data show large faulted and rotated basement blocks. Gravity modeling indicates a thin basement with a thickness of 1–3 km and a density of 2.8*103 kg/m3 between the base of the sediments and the top of the mantle, which indicates exhumed and serpentinized mantle. The Gakkel spreading ridge, located in northern prolongation of the seismic lines is characterized by an amagmatic or sparsely magmatic segment. From the structural similarity between the basement close to the ultra-slow spreading ridge and our study area, we conclude that the basement in the Eurasia Basin is predominantly formed by exhumed and serpentinized mantle, with magmatic additions. An initial strike-slip movement of the Lomonosov Ridge along the North Barents Sea Margin and subsequent near-orthogonal opening of the Nansen Basin is supposed to have brought mantle material to the surface, which was serpentinized during this process. Continuous spreading thinned the serpentinized mantle and subsequent normal faulting produced distinct basement blocks. We propose that mantle exhumation has likely been active since the opening of the Eurasia Basin

Late Cenozoic erosion estimates for the northern Barents Sea: Quantifying glacial sediment input to the Arctic Ocean

A compilation of seismic data has been used to characterize the Neogene – Quaternary sedimentary succession of the northwestern Barents Sea continental margin to better understand the paleoenvironmental evolution and the sedimentary processes involved. The Neogene strata are dominated by contourites related to the ocean circulation established from the opening of the Fram Strait connecting the Atlantic and the Arctic Oceans (< ~17.5 Ma). The upper Plio–Pleistocene strata (< ~2.7 Ma) are dominated by stacked gravity‐driven deposits forming trough‐mouth fans that were sourced from paleo‐ice streams. Within the inter‐fan areas, contouritic sedimentation prevailed. Thus, this margin provides an example of interaction of glacigenic debris flows, contour currents, and hemipelagic/glacimarine sedimentary processes. A total of ~29,000 km3 of sediments with an average sedimentation rate of about 0.24 m/Kyr were estimated. These numbers reflect the sediment input to this part of the Arctic Ocean from the northwestern Barents Sea shelf and adjacent land areas. For the first time, the average erosion and erosion rates for this source area are estimated using a mass balance approach. Approximately 410 – 650 m of erosion has on average occurred, corresponding to an average erosion rate of ~0.15 – 0.24 m/Kyr. These rates are comparable to those reported from other glaciated margins, including the western Svalbard and mid‐Norway margin, but up to only half the rates reported from the western Barents Sea margin. This variation is interpreted due to the size and bedrock types of the drainage area, ice dynamics, and the continental slope gradient