Using the tectophase conceptual model to assess late Triassic–Early Jurassic far-field tectonism across the South-central Barents Sea shelf

The Upper Triassic–Lower Jurassic succession of the Barents Sea Shelf (BSS) represents one of Europe’s most prolific and strategic petroleum systems. This succession reflects various depositional environments and tectonostratigraphic events. Even though these strata are considered largely well-understood, connections with far-field stresses triggered by regional tectonics remain a subject of investigation. This study presents new interpretations that focus on relationships between the stratigraphic succession across the south-central BSS and Triassic–Jurassic Novaya Zemlya compressional tectonics. By applying the “tectophase model,” developed in the Appalachian Basin, to analyze this succession, the presence of foreland-basin depozones and associated far-field processes related to compressional tectonics in an adjacent orogen are suggested. This model addresses unconformity development, lithostratigraphic succession, and reactivation of structures. Use of this model suggests far-field tectonostratigraphic responses during two episodes of Novaya Zemlya tectonism, reflected in the coeval BSS stratigraphy. Overall, this tectonostratigraphic study aligns with other research suggesting a Late Triassic inception for Novaya Zemlya compressional tectonism, which influenced larger parts of the BSS through extensive clastic sedimentation, far-field structural reactivation, and flexural responses to deformational loading triggered by tectonics

The Early to Middle Cenozoic Paleoenvironment and Erosion Estimates for the northwestern Barents Sea

The northwestern Barents Sea continental margin is a structurally complex area characterized by a series of basins and highs. It’s Cenozoic development was influenced by: 1) the formation of the Spitsbergen fold-andthrust belt towards the north and a pull-apart basin, the Vestbakken Volcanic Province, to the south, and 2) the subsequent rifting and opening of the Fram Strait, the deep-water gateway connecting the Norwegian – Greenland Sea and the Arctic Ocean. From this, the northwestern Barents Sea margin is suggested to have experienced a complex tectonic evolution during the Cenozoic, including compression/transpression and extension/transtension. The study area forms a part of a broad transform zone to the west of Svalbard that was initiated during the rifting and seafloor opening between Norway and Greenland in the Paleocene-Early Eocene. Newly available 2D seismic data and magnetic data were used to better understand the tectono-sedimentary evolution of the northwestern Barents Sea margin. The seismic data shows a pronounced sequence of Paleogene - Neogene, pre-glacial sediments within the basins overlying the oceanic crust west of the transform zone. To the east, the Svalbard platform and the Stappen High includes very little Cenozoic deposits implying that these areas were subjected to erosion and probably acted as the main sediment source area for the northwestern Barents Sea margin. Updated paleoenvironment maps for this area throughout the Early - Middle Cenozoic will be reconstructed and discussed. A number of studies have addressed the uplift and erosion processes during the Cenozoic for the southwestern Barents Sea margin. However, very limited work have been presented from the northwestern Barents Sea, thus the processes of erosion, erosion estimates, and their inferred source area are still poorly understood. Therefore, we also aim to estimate the erosion and erosion rates for the Paleogene – Neogene strata and compare them to other parts of the Norwegian – Barents Sea – Svalbard margin and relevant modern systems

Cenozoic Erosion of the Barents Sea Shelf, Norwegian Arctic: A Review

The circum North Atlantic-Arctic continental margin and adjacent land areas have experienced several episodes of uplift and erosion during the Cenozoic. A series of efforts quantifying this erosion for the Barents Sea shelf, where the Arctic shelf is at its widest and deepest have been done since the early 90’s using different methods. As the seismic and well database have expanded considerably, our understanding of the Cenozoic evolution of this climatic sensitive and hydrocarbon prospective area has improved. This review includes a comparison of results from different methods (e.g. the mass balance technique,shale compaction, apatite fission track, sandstone diagenesis, and seismic velocities). The Cenozoic erosion is divided into a pre-glacial and a glacial erosion. The pre-glacial erosion is related to the early Cenozoic tectonics and riftflank uplift due to the onset of rifting, shear, and compression followed by sea-floor spreading between Norway and Greenland, whereas the glacial erosion occurred during the late Cenozoic Northern Hemisphere Glaciations when grounded ice sheets repeatedly covered the Barents Sea shelf. The different methods generally show the same order of magnitude of erosion for the major source areas in the Barents Sea, i.e. northern Norway, the Loppa High, the Stappen High, Svalbard, and from the northern Barents Sea margin. Furthermore, we compare sediment load and size of drainage area from various settings and different periods. For similar size of drainage area, sediment load for glacial period is generally higher than for the pre-glacial one. Our review shows that the ratio between the Cenozoic pre-glacial and glacial sedimentation along this part of the Arctic margin is ~40%, ~50%, and ~70% for the southwestern, northwestern, and the northern Barents Sea, respectively. Thus, there is a N-S trend of increasing pre-glacial erosion of the Barents Sea shelf, whereas an W-E trend of increasing erosion is inferred for the glacial period. Future directions of research in refining the erosion estimates and better understanding the mechanisms of uplift and erosion will be addressed

Contrasting Neogene–Quaternary continental margin evolution offshore mid-north Norway: Implications for source-to-sink systems

The Neogene–Quaternary development of the ∼700 km long mid-Norwegian and Lofoten–Vesterålen continental margin is reconstructed using a dense grid of 2D seismic data and exploration wellbores. Overall, widespread ocean current-controlled contourite drifts built up along the whole margin segment from the mid-Miocene onwards (c. 11 Ma, Kai Formation). The onset (c. 8.8 Ma) of a large inner shelf progradation (Molo Formation) was, however, restricted to the southern part of the study area, the inner mid-Norwegian shelf. In the Quaternary (c. 2.7 Ma), grounded ice sheets repeatedly brought large sediment volumes (Naust Formation) to the shelf beyond the Molo Formation. A similar build-out is less pronounced further north, where contourite drift growth instead continued and resulted in build-up of the Lofoten and Vesterålen drifts. In contrast, the drifts of the southern part of the study area occur for the most part stratigraphically below, interbedded with and distal to the progradational Molo and Naust deposits. The study area exemplifies pronounced variability in Neogene–Quaternary continental margin growth. The wide and gently dipping mid-Norwegian margin facilitated coastal and shelf progradation related to fluvial and glacial processes, while the narrow and steep Lofoten–Vesterålen margin received little input from these sources although exposed to the same paleoclimate. Instead, erosion of canyons promoted downslope reworking across the slope and into the deep basins. This low sediment input is interpreted to be controlled by the alpine relief in the north resulting in a small source area and thus low fluvial and glacial sediment input. To the south, hinterland relief allowed for a much larger fluvial and later, glacial source area. Both margin segments were also influenced by contour currents throughout the studied period. We emphasize their importance for understanding the role of erosion and deposition in source-to-sink systems, and thus the need for these processes to be integrated within source-to-sink model

Cenozoic uplift and erosion of the Norwegian Barents Shelf – A review

Uplift and erosion are complex phenomena in terms of their governing processes, precise timing and exact magnitude. The intricate relationship between different geodynamic processes leading to uplift may increase uncertainties in estimating spatial and temporal patterns. Sediment distribution from uplifted (and eroded) topography and the corresponding paleoenvironmental reconstructions require reliable constrains. The Barents Shelf provides a unique arena to study uplift and erosion due to extensive seismic and well data attributed to high petroleum activity. This particular interest has led to a voluminous literature about this topic over the last three decades. Here, we present the current status of the Cenozoic uplift and erosion on the Norwegian Barents Shelf by reviewing the key terminology, its tectonic history and paleoenvironment, methods in quantifying uplift and erosion, as well as timing and possible mechanisms. Our new erosion maps show an increase in net erosion to the north and northeast that represents key underlying concepts, including tectonic (compression, rift-flank uplift, thermo-mechanical coupling, mantle dynamics, flexural/isostatic response) as well as magmatic and glacial processes. We have integrated pre-glacial and glacial net erosion using the mass balance method and added our results from sonic velocity, interval velocity and sandstone diagenesis methods to the new maps. This review shows that discrepancies of net erosion estimates from different methods are on the order of 500 m. Finally, we identify research gaps for future studies, with implications for the Barents Shelf and other uplifted basins worldwide

Using the tectophase conceptual model to assess late Triassic–Early Jurassic far-field tectonism across the South-central Barents Sea shelf

The Upper Triassic–Lower Jurassic succession of the Barents Sea Shelf (BSS) represents one of Europe’s most prolific and strategic petroleum systems. This succession reflects various depositional environments and tectonostratigraphic events. Even though these strata are considered largely well-understood, connections with far-field stresses triggered by regional tectonics remain a subject of investigation. This study presents new interpretations that focus on relationships between the stratigraphic succession across the south-central BSS and Triassic–Jurassic Novaya Zemlya compressional tectonics. By applying the “tectophase model,” developed in the Appalachian Basin, to analyze this succession, the presence of foreland-basin depozones and associated far-field processes related to compressional tectonics in an adjacent orogen are suggested. This model addresses unconformity development, lithostratigraphic succession, and reactivation of structures. Use of this model suggests far-field tectonostratigraphic responses during two episodes of Novaya Zemlya tectonism, reflected in the coeval BSS stratigraphy. Overall, this tectonostratigraphic study aligns with other research suggesting a Late Triassic inception for Novaya Zemlya compressional tectonism, which influenced larger parts of the BSS through extensive clastic sedimentation, far-field structural reactivation, and flexural responses to deformational loading triggered by tectonic

The Appalachian area as a tectonostratigraphic analogue for the Barents Sea shelf

This is the peer reviewed version of the following article: Martins, Ettensohn, Knutsen. The Appalachian area as a tectonostratigraphic analogue for the Barents Sea shelf. Basin Research. 2021, which has been published in final form at https://doi.org/10.1111/bre.12619. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.The US Appalachian Basin and the Arctic Norwegian and Russian Barents Sea shelf (BSS) areas are two strategic provinces for the energy industry. The Appalachian Basin is a well-studied, mature, onshore basin, whereas the offshore BSS is still considered a frontier area. This study suggests that the Appalachian Basin may be an appropriate analogue for understanding the BSS and contribute to development of a tectonostratigraphic framework for the area. Although the Appalachian and BSS areas reflect different times and settings, both areas began as passive margins that were subsequently subjected to subduction and continent collision associated with the closure of an adjacent ocean basin. As a result, both areas exhibited multi-phase subduction-type orogenies, a rising hinterland that sourced sediments, and a foreland-basin sedimentary system that periodically overflowed onto an adjacent intracratonic area of basins and platforms with underlying basement structures. Foreland-basin sedimentary systems in the Mid-to-Late Palaeozoic Appalachian Basin are composed of unconformity-bound cycles related to specific orogenic pulses called tectophases. Each tectophase gave rise to a distinct sequence of lithologies related to flexural events in the orogen. In this study, similar sequences are recognised in both BSS foreland-basin and adjacent intracratonic sedimentary sequences that formed in response to the Late Palaeozoic–Mesozoic Uralian–Pai–Khoi–Novaya Zemlya Orogeny, suggesting that the processes generating the sequences are analogous to the tectophase cycles in the Appalachian Basin. Hence, this pioneering use of the Appalachian area and its succession as large-scale tectonostratigraphic analogues for the BSS may further enhance understanding of Upper Palaeozoic to Middle Jurassic stratigraphy across the BS

The Cenozoic pre-glacial tectono-sedimentary development of the western Barents Sea margin: implications for uplift and erosion of the sediment source areas

The Cenozoic development of the western Barents Sea continental margin is strongly related to the rifting and seafloor spreading between Norway and Greenland. The margin is characterized by a series of highs and basins that formed as part of the development of a mega-transform zone. To the north, the Spitsbergen Fold and Thrust Belt and the Eocene clinoform development in the Central Basin that were initiated in the Paleocene Early Eocene are the evident of compression / transpression, and sediment erosion, transport and deposition respectively. At that time, the Vestbakken Volcanic Province and the Sørvestsnaget Basin to the south experienced a period of subsidence. A marginal high and an intra- basinal high in the Sørvestsnaget Basin, as well as the Senja Ridge and the Veslemøy High are identified as positive bathymetric features that acted as local source areas. Seismic data also shows a set of Eocene clinoform in the eastern part of the Sørvestsnaget Basin that probably was sourced from the Stappen High area. Available well data show an overall deep-water paleoenvironment during the Paleocene-Eocene in the south western Barents Sea, probably shallowing north of Bjørnøya. During the Oligocene, a period of plate reorganization occurred that resulted in the onset of extension also in the north western Barents Sea including sea floor spreading west of Svalbard. Here, the Forlandsundet and Bellsund grabens as well as most of the extensional faults show a significant growth. In the southwestern Barents Sea, traces of compression structures are seen on seismic data suggesting a period of tectonic inversion. An overall shallow marine paleoenvironment characterized the south western Barents Sea shelf during the Oligocene being deeper towards the west. Seismic data shows contourite development in the continentalslope areacontemporaneouswiththeopeningoftheFramStrait that connected the oceanic circulation of the Atlantic and the Arctic Ocean. Seismic mapping of the Paleogene-Neogene strata shows an eastward and northward increasing uplift trend in the western Barents Sea that was amplified in the late Cenozoic due to glacio-isostatic subsidence and uplift due to sediment loading/unloading process. This study suggests also a period of pre glacial’s subsidence and uplift during the Eocene due to the rifting and sea floor spreading between Norway and Greenland. A local secondary uplift in the Oligocene with lesser magnitude is also identified. Erosion estimates for the western margin is calculated to be 900-1400 m in the southwestern and probably more than 2000 m in the north western BarentsSea. The sedimentation rates and erosion rates for the Cenozoic preglacial period shows values one order of magnitude lower than during the Late Cenozoic

Cenozoic pre-glacial tectonostratigraphy and erosion estimates for the northwestern Barents Sea

Poster presentation at European Geosciences Union General Assembly 2017, Vienna, Austria