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West Antarctica developed as the tectonically active margin separating East Antarctica and the Pacific Ocean for almost half a billion years. Its dynamic history of magmatism, continental growth and fragmentation are recorded in sparse outcrops, and revealed by regional geophysical patterns. Compared with East Antarctica, West Antarctica is younger, more tectonically active and has a lower average elevation. We identify three broad physiographic provinces within West Antarctica and present their overlapping and interconnected tectonic and geological history as a framework for future study: 1/ The Weddell Sea region, which lay furthest from the subducting margin, but was most impacted by the Jurassic initiation of Gondwana break-up. 2/ Marie Byrd Land and the West Antarctic rift system which developed as a broad Cretaceous to Cenozoic continental rift system, reworking a former convergent margin. 3/ The Antarctic Peninsula and Thurston Island which preserve an almost complete magmatic arc system. We conclude by briefly discussing the evolution of the West Antarctic system as a whole, and the key questions which need to be addressed in future. One such question is whether West Antarctica is best conceived as an accreted collection of rigid microcontinental blocks (as commonly depicted) or as a plastically deforming and constantly growing melange of continental fragments and juvenile magmatic regions. This distinction is fundamental to understanding the tectonic evolution of young continental lithosphere. Defining the underlying geological template of West Antarctica and constraining its linkages to the dynamics of the overlying ice sheet, which is vulnerable to change due to human activity, is of critical importance.

How to cite: Jordan, T., Riley, T., and Siddoway, C.: Overview of West Antarctic tectonic evolution from ~500 Ma to the present, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8265, https://doi.org/10.5194/egusphere-egu21-8265, 2021.

Antarctica has traditionally been considered continental inside the coastline of ice and bedrock since Press and Dewart (1959). Sixty years later, we reconsider the conventional extent of this sixth continent (Artemieva and Thybo, Earth-Science Reviews, 2020, https://doi.org/10.1016/j.earscirev.2020.103106).

Geochemical observations show that subduction was active along the whole western coast of West Antarctica until the mid-Cretaceous after which it gradually ceased towards the tip of the Antarctic Peninsula. We propose that the entire West Antarctica formed as a back-arc basin system flanked by a volcanic arc, similar to e.g. the Japan Sea, instead of a continental rift system as conventionally interpreted and tagged in the literature as “West Antarctica Rift System”.

Globally, the fundamental difference between oceanic and continental lithosphere is reflected in hypsometry, largely controlled by lithosphere buoyancy. The equivalent (corrected for ice and water) hypsometry in West Antarctica (−580 ± 335 m on average, extending down to −1580 m) is much deeper than in any continent, since even continental shelves do not extend deeper than −200 m in equivalent hypsometry. However, an unusually deep equivalent hypsometry in West Antarctica corresponds to back-arc basins (with average values of equivalent hypsometry between ca −3000 m and −300 m) and oceans proper. This first order observation questions the conventional interpretation of West Antarctica as continental.

We present a suite of geophysical observations that supports our geodynamic interpretation:

• a linear belt of seismicity sub-parallel to the volcanic arc along the Pacific margin of West Antarctica;
• a pattern of free air gravity anomalies typical of subduction systems;
• and extremely thin crystalline crust typical of back-arc basins.

We calculate lithosphere density for two end-member scenarios to fit the calculated mantle residual gravity anomalies and seismic data on crustal thickness and demonstrate that it requires the presence of:

• (1) a thick sedimentary sequence of up to ca. 50% of the total crustal thickness, or
• (2) extremely low density mantle below the deep basins of West Antarctica and, possibly, the Wilkes Basin in East Antarctica.

Case (1) implies that for 25 ±6 km of the total crustal thickness, the crystalline basement is only 12-15 km thick, and such values are not observed in continental crust. Case (2) requires the presence of anomalously hot mantle below the entire West Antarctica with a size much larger than around continental rifts.

These results favor the presence of oceanic or transitional crust in most of West Antarctica and possibly beneath the Ronne Ice Shelf. Our model predicts that a granitic crustal layer with a high radiogenic heat production is almost absent in most of West Antarctica, which may affect heat flux at the base of the ice with potential important implications for models of ice melting. We propose, by analogy with back-arc basins in the Western Pacific, the existence of rotated back-arc basins caused by differential slab roll-back during subduction of the Phoenix plate under the West Antarctica margin.

Our finding reduces the continental lithosphere in Antarctica to 2/3 of its traditional area. It has significant implications for global models of lithosphere-mantle dynamics and models of the ice sheet evolution.

How to cite: Artemieva, I. M. and Thybo, H.: One third of Antarctica is not continental: Geophysical evidence for West Antarctica as a backarc system, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9259, https://doi.org/10.5194/egusphere-egu21-9259, 2021.

Yelcho Station is set on Doumer Island located in the southernmost section of Gerlache Strait between Anvers and Wienke Islands at the northwestern region of Antarctic Peninsula. This area is dominated by plutonic and volcanic deposits associated with the active margin developed during the Mesozoic and Cenozoic in the Antarctic Peninsula (e.g. Leat et al., 1995). Although Yelcho Station has been intensively visited since a few decades, the outcropping rocks have not been studied in detail. Furthermore, this location has hosted relevant contributions in the environmental and ecological sciences. We will present a detailed map (1:500) of the geological units outcropping in Yelcho Station based in fieldwork observations, which will be combined with drone and satellite images. Additionally, remote sensing spectral studies will be developed to support the geological mapping. This work will help to establish a geological baseline, which may serve for future studies in the area of Yelcho Station. This contribution will be a detailed geological study in the Antarctic Peninsula, which will also enhance our understanding of the geological units outcropping in Gerlache Strait. This material will also serve as an educational and outreach information for the polar community.

Leat et al. (1995). Geological Magazine 132 (4), 399-412 (DOI: 10.1017/S0016756800021464).

How to cite: Jara, W., Bastias, J., Jaña, R., and Leppe, M.: The geology of Yelcho Station: a new high-resolution geological map at northwestern Antarctic Peninsula, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12707, https://doi.org/10.5194/egusphere-egu21-12707, 2021.

King George Island is the largest one of the South Shetland Islands group distributed parallel to and separated by the Bransfield Strait of the northern tip of Antarctic Peninsula. The archipelago of the South Shetlands is mainly composed of the products of the active margin developed as a result of the subduction of the Phoenix Plate beneath the continental crust of the Antarctic Peninsula (e.g. Barker, 1982; Bastias et al., 2019). The lithologies are largely dominated by Mesozoic and Cenozoic sedimentary and volcanic successions that are cut by a few hypabyssal plutons. While some authors have suggested a southwest to northeast trend along the archipelago from older to younger magmatic activity (e.g. Haase et al., 2012), others have indicated that some of the magmatic events may have been recorded along the entire archipelago (e.g. Valanginian arc rocks; Bastias et al., 2019). Regardless, King George Island hosts an exceptional stratigraphical record of the Cenozoic period. Moreover, this island is mostly covered by an ice cap at the present day, which is commonly terminated with ice cliffs around much of the island. The southern edge of the island host Mesozoic and Paleogene successions, these rocks are dominated by volcanic and volcaniclastic units. The rocks in King George Island are generally young to the east and to the north ends. Cape Melville, the southeast extreme of the island, hosts the youngest sedimentary rocks known on the island: the Moby Dick Group (Birkenmajer, 1985).

While several authors have presented local studies in the King George Island over the last three decades, an integrated assessment of the outcropping units in the entire island remains unexplored. A new geological map for King George Island will allow to update the current understanding of the stratigraphy of the South Shetland Islands, which will help to support not only the geological studies but also those focused on the environmental and paleontological record.

Barker, 1982. Journal of the Geological Society 19, 787-801. (DOI: 10.1144/gsjgs.139.6.0787)

Bastias et al. (2019). International Geology Review 62 (11), 1467-1484. (DOI: 10.1080/00206814.2019.1655669)

Birkenmajer (1985). Bulletin Polish Academic Earth Sciences 33:15-23.

Haase et al. (2012). Contributions to Mineralogy and Petrology 163, 1103-1119. (DOI: 10.1007/s00410-012-0719-7).

How to cite: Lopez, B., Bastias, J., Matus, D., Jaña, R., and Leppe, M.: The geology of King George Island, South Shetland Islands: uniting local geological maps and stratigraphical columns, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13145, https://doi.org/10.5194/egusphere-egu21-13145, 2021.

The Rennick Geodynamic Belt (RGB, East Antarctica) is a regionally sized, ca N-S trending, deformation zone (length > 100 km) where a dense fault network separates tectonic units of northern the Victoria Land, to the W from the East Antarctic Craton, to the E.

The RGB is long known to have been active since Cambrian-Ordovician times up to recent, but its framework and geodynamic evolution is still debated and partially investigated. The long-lived tectonic activity led to a great structural complexity, due to the superposition and polyphasic reactivation of regional faults. Such complexity is reflected by the numerous (in some cases contrasting) tectonic reconstructions of the RGB area.

In this contribution we explore the present-day tectonic framework of the RGB, investigating the stress field that possibly characterised the last geodynamic events in the area. We base on selected datasets of fault-slip data and fractures density (collected by the Authors in various PNRA Italian Antarctic expeditions) and combine fault-slip data inversion with the azimuthal orientation of faults and the spatial distribution of fractures intensity across the RGB.

To obtain a more robust portrait of the RGB geodynamic evolution, two different software based on different fault-inversion methods were used in this study: DAISY (Windows, version 3.5) and FSA (MAC, version 36.5x7i). The software DAISY implements the multiple Monte Carlo convergent method and provides the best orientation of the principal paleostresses with an estimate of the error quantified by the factor MAD (Mean Angular Deviation, corresponding to the average angular deviation between the measured pitch of the kinematic vector on the fault plane and the predicted one by applying to the fault the computed paleostress). At each step, faults are uniquely associated to the stress tensor that provides the lowest MAD. Differently, the FSA software combines a random grid search of the stress tensors following a Monte Carlo approach, under the univocal condition of fulfilment of the frictional constraint (i.e. the fault plane must form with an orientation that satisfies the Mohr-Coulomb yield criterion, i.e. t/s_n = tgf with t = shear stress, s_n = normal stress and f = angle of internal friction). Additionally, this software allows a direct examination of the reduced Mohr circle of the calculated stress tensors, so that we can select the one with the largest number of faults showing a high t/s_n ratio.

The paleostress tensors were computed from 373 fault-slip data collected in 34 structural stations on site. Results from this multi methodological approach revealed:

(i) the existence of two, N-S oriented geotectonic provinces (namely the Bowers Mts province to the W and Usarp Mts to the E) characterized by the different spatial distribution of brittle deformation, more intense in the Bower Mts domain.

(ii) The superposition of two recent (Meso-Cenozoic) major tectonic events, with prevalent strike-slip kinematics and characterized by faults reactivation with right-lateral movement overprinting a previous left-lateral one.

How to cite: Locatelli, M., Cianfarra, P., Crispini, L., and Federico, L.: Multiple reactivation of the Rennick Geodynamic Belt (northern Victoria Land, Antarctica): insights from inversion of fault slip data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11675, https://doi.org/10.5194/egusphere-egu21-11675, 2021.

The Mesozoic Karoo-Maud and Kerguelen plumes had a significant influence on Gondwana and the oceanic lithosphere. Jurassic magmatism, formed under the influence of a huge Karoo plume at 184–178 Ma ago, covered large areas of the Dronning Maud Land in East Antarctica. Later, 130 – 0 m.y. ago, under the influence of the Kerguelen plume, magmatism formed in the area of the Lambert glacier, and the Gaussberg volcano (Quaternary time) appeared, located on the coast opposite the Kerguelen archipelago. We assume that the Karoo mantle plume initiated the formation of a “mega-apophyses” from the main plume manifestation area within the Karoo province in the southeastern African continet (ca. 2000 km in diameter). These mega-apophyses are represented by the Ferrar Igneous Province (ca. 3000 km long area of intrusive activity along the Transantarctic Mountains) and a supposed igneous province (ca. 1500 km long) covering the East Antarctic coast between the Lazarev and Cosmonauts Seas. Based on petrological and geochemical studies, the characteristic features of magmas of the Karoo, Dronning Maud Land, and Ferrar igneous provinces have been determined, which indicate that for all magmas associated with Karoo and Kerguelen plumes, the main source of melt enrichment is a mantle source with characteristics of the EM-II component (most typically for magmas of the Ferrar Province). It reflects the properties of an enriched, fluid-rich, ancient continental mantle, metasomatized at the early stages of the tectonic development of the region and involved in the melting process. A rarer admixture of the ancient lithospheric component (EM-I, with ²⁰⁶Pb/²⁰⁴Pb = 16.5 and ¹⁴³Nd/¹⁴⁴Nd = 0.5122) was revealed in both plumes. The existence of mantle plumes in the Southern Hemisphere and their long-term development had a significant impact on the structure and evolution of the East Antarctica.

How to cite: Sushchevskaya, N., Leitchenkov, G., and Belyatsky, B.: Tectono-magmatic evolution of the Karoo and Kerguelen plumes and their impact onto magmatism of the East Antarctica, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5128, https://doi.org/10.5194/egusphere-egu21-5128, 2021.

A complex tectonic history and global climate change has influenced the land masses bordering the Arctic ocean.  On land tectonic movement affects runoff patterns, local hydology such as increased precipitation and local surface elevation, which again affects landform development, coastline distribution, discharge routing and vegetation distribution. Land- atmosphere- biosphere links and feedback loop with the ocean are continuously refined for use in earth system models for the youngest part of geological history. With access to large data sets, improved technology and new knowledge and methodologies it is now increasingly possible to also reconstruct direct surface response to tectonic movement in deep time.

The Paleogene Central Tertiary Basin, Svalbard, Norway formed in response to the complex opening and collision at the entrance to the Arctic Ocean, causing uplift in the west and basin formation and fill in the Central Spitsbergen area. Well exposed outcrops and extensive work in the area for decades provides a framework of palaeogeographic change within the basin. The basin deposits range from continental to deep marine with changing coastline positions largely caused by tectonic activity. The timing of the basin development coincides with the time period immediately before and after the PETM and thus provides an example of a terrestrial system in a warm Arctic. Syndepositional volcanic eruptions in the Arctic area are reflected in tephra layers, which also provide opportunity for correlation and absolute time estimates (Jones et al. 2017).

We use data from two formations deposited within the basin as a field laboratory for surface response to tectonic and climate change in the Arctic. The Paleocene Firkanten Fm, is deposited during the early stages of basin formation and pre-PETM. The Eocene Aspelintoppen Formation, is deposited during late stages of basin filling and is post-PETM. Both formations are characterized by continental to paralic deposits and contain traces of palaeovegetation such as coal seams, palaeosols and fossil leaves. A large amount of exploration drill holes through the Firkanten Fm provide a unique insight into the palaeotopography and depositional trends relative to topography during deposition (Marshall et al., submitted). The presence of coal seams allows for direct reconstruction of vegetation (peat bogs) and interaction between hydrology and deposition. The Aspelintoppen Formation comprises a thick succession of channel and floodplain deposits and reflects a balance between sediment supply and accommodation. We use virtual outcrops to provide 3D architecture from inaccessible mountain sides to improve the possibilities for quantification of precipitation and discharge parameters from the basin.

References:

Jones, M.T., Augland, L.E.,, Shephard, G.E., Burgess, S.D., Eliassen, G.T., Jochmann, M.M., Friis, B., Jerram, D.A., Planke, S. & Svensen, H.H., 2017: Constraining shifts in North Atlantic plate motions during the Palaeocene by U-Pb dating of Svalbard tephra layers. Nature Scientific Reports 7: 6822 DOI:10.1038/s41598-017-06170-7

Marshall, C., Jochmann, M., Jensen, M., Spiro, B.F., Olaussen, S., Large, D.J.: Time, hydrologic landscape and the long-term storage of peatland carbon in sedimentary basins. Submitted to Journal of Geophysical Research - Earth Surface

How to cite: Jensen, M. A., Jochmann, M., Marshall, C., and Bøgh Mannerfelt, A.: How does increased palaeosurface reconstruction contribute to understanding of the Arctic? -  Developing a deep time palaeoclimate field laboratory in Svalbard., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16340, https://doi.org/10.5194/egusphere-egu21-16340, 2021.

Sub-surface sampling of marine sediments allows investigation of paleo-depositional conditions and subsequent modification by post-depositional geochemical processes. This sedimentary record can encompass many thousands of years and record discrete events where proximal and distal material is incorporated into the pelagic sediment column. The Arctic Ocean is the world’s smallest ocean, however evidence from sedimentary records show it has a pivotal role in the regulation of many oceanographic and physiographic processes. Despite this, there are only limited studies on the distribution and geochemical behaviour of metals within sub-surface marine sediments of the Arctic Ocean basin. This study presents a detailed geochemical investigation for two sediment piston cores to a maximum of 5.7 metres depth and spanning at least 44,000 years BP, from two seamounts bordering the western flanks of the Molloy Hole in the Fram Strait.

Comparison to other studies of sub-surface ridge sediments below 60^oS on the Mid-Atlantic Ridge reveals these piston cores contain elevated metal concentrations, particularly for Mn, Co, and Ni. Distinct variability is observed within, and between the cores; particularly the interplay between Fe and Mn, the two most common authigenic elements in marine pelagic sediments. Within the Molloy Ridge neovolcanic zone, in the upper half of the easternmost core (PC127/79), Fe and Mn are decoupled and metal distribution is controlled by redox front migration. Decoupling occurs as Mn is more readily dissolved compared to Fe, and Fe in solution is more reactive and precipitates quicker during remobilisation. In PC127/79, Mn is strongly associated with other redox-sensitive metals (e.g., Co, Ni, Mo, U) likely in Mn-oxide dominated horizons, and Fe is strongly associated with V and As. Towards the base of the core, Fe and Mn are coupled, but are not associated with a distinct discrete metalliferous signature of Co, Ni, Cd and Ti. These metals are also negatively associated with major rock-forming elements such as Si, Al, Mg, and Ca. In the western core (PC127/80), Fe and Mn are coupled, are positively associated with the majority of metals and the major rock forming elements, and negatively correlated with common clay-derived components.

Investigation of pelagic versus hydrothermal component indices indicate that the distinct metalliferous signature towards the base of PC127/79 may have a hydrothermal origin. Hydrothermal activity associated with ultramafic oceanic core complexes is known on superslow-spreading ridges to the north and south of the Molloy Ridge, however contributions of metals from ice-rafted debris or past mass wasting events off the Spitsbergen margin cannot be ruled out.

How to cite: Grant, H., Lockwood-Ireland, C., Howe, J., and Stewart, H.: Controls on the distribution and behaviour of metals in sub-surface metalliferous seamount sediments from the Molloy Ridge system, Arctic Ocean, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10154, https://doi.org/10.5194/egusphere-egu21-10154, 2021.

The High Arctic Large Igneous Province (HALIP) represents extensive Cretaceous magmatism throughout the circum-Arctic borderlands and within the Arctic Ocean (e.g., the Alpha-Mendeleev Ridge). Recent aeromagnetic data shows anomalies that extend from the Alpha Ridge onto the northern coast of Ellesmere Island, Nunavut, Canada. To test this linkage we present new bulk rock major and trace element geochemistry, and mineral compositions for clinopyroxene, plagioclase, and olivine of basaltic dykes and sheets and rhyolitic lavas for the stratotype section at Hansen Point, which coincides geographically with the magnetic anomaly at northern Ellesmere Island. New U-Pb chronology is also presented.

The basaltic and basaltic-andesite dykes and sheets at Hansen Point are all evolved with 5.5–2.5 wt% MgO, 48.3–57.0 wt% SiO2, and have light rare-earth element enriched patterns. They classify as tholeiites and in Th/Yb vs. Nb/Yb space they define a trend extending from the mantle array toward upper continental crust. This trend, also including a rhyolite lava, can be modeled successfully by assimilation and fractional crystallization. The U-Pb data for a dacite sample, that is cut by basaltic dykes at Hansen Point, yields a crystallization age of 95.5 ± 1.0 Ma, and also shows crustal inheritance. The chronology and the geochemistry of the Hansen Point samples are correlative with the basaltic lavas, sills, and dykes of the Strand Fiord Formation on Axel Heiberg Island, Nunavut, Canada. In contrast, a new U-Pb age for an alkaline syenite at Audhild Bay is significantly younger at 79.5 ± 0.5 Ma, and correlative to alkaline basalts and rhyo- lites from other locations of northern Ellesmere Island (Audhild Bay, Philips Inlet, and Yelverton Bay West; 83–73 Ma). We propose these volcanic occurrences be referred to collectively as the Audhild Bay alkaline suite (ABAS). In this revised nomenclature, the rocks of Hansen Point stratotype and other tholeiitic rocks are ascribed to the Hansen Point tholeiitic suite (HPTS) that was emplaced at 97–93 Ma. We suggest this subdivision into suites replace the collective term Hansen Point volcanic complex.

The few dredge samples of alkali basalt available from the top of the Alpha Ridge are akin to ABAS in terms of geochemistry. Our revised dates also suggest that the HPTS and Strand Fiord Formation volcanic rocks may be the hypothesized subaerial large igneous province eruption that drove the Cretaceous Ocean Anoxic Event 2.

How to cite: Naber, T. V., Grasby, S. E., Cuthbertson, J. P., Rayner, N., and Tegner, C.: New constraints on the age, geochemistry and environmental impact of High Arctic Large Igneous Province magmatism: Tracing the extension of the Alpha Ridge onto Ellesmere Island, Canada, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16329, https://doi.org/10.5194/egusphere-egu21-16329, 2021.

Alaska is made up of a mosaic of terranes that have enigmatic origins. Several plate restorations for the assembly of Alaska have been proposed, but their validity remains debated, partly due to the removal of vast volumes of oceanic plate material via subduction at the accretionary margins. The position, depth and volume of this subducted lithosphere, recognised as seismically fast anomalies in tomographic images, can be used to track the locations of subduction plate boundaries of the past, thus serving as an important constraint for plate restorations of convergent margins. Existing plate tectonic reconstructions can be assessed and developed further by integrating seismic tomographic models of the mantle with geological and palaeomagnetic bedrock datasets, a procedure which we term “tomotectonic analysis”.

Previous tomotectonic studies (e.g., Sigloch & Mihalynuk, 2017, GSA Bulletin) have highlighted various discrepancies between the most generally accepted tectonic reconstruction models of the western coast of North America and tomographic observations of slabs in the mantle. For example, the kinematic reconstruction of Laurentia, constrained by the opening of the Atlantic Ocean, places the Cordilleran margin thousands of kilometres east of the tomographically imaged Angayucham and Mezcalera slabs in the mantle during the Early to Late Jurassic. This suggests that there was extensive westward subduction beneath the Insular and Intermontane superterranes that involved multiple plates, rather than a single subduction zone. Though a recent plate reconstruction that employed tomotectonic methods (Clennett et al., 2020, G-Cubed) provided a coherent explanation of bedrock, plate kinematic and mantle observations for the Cordilleran margin, application of this model to Alaska and the Arctic was hindered by low tomographic resolution beneath that region and requires further investigation. In particular, restoration of the Arctic Alaska terrane is complicated further by its possible relationship with the proposed Arctic Alaska-Chukotka microcontinent and its involvement in the accretionary development of the Siberian peninsula and the opening of the Canada Basin, for which several working hypotheses continue to be debated.

In this study we consider the application of tomotectonic analysis to Mesozoic reconstructions of the western Arctic and central Alaska. We will compare and contrast these tectonic reconstructions with respect to the distribution of slabs in the deep mantle based on observations from the latest seismic tomographic models, such as DETOX-P1, P2 and P3 (Hosseini et al., 2020, GJI). We will also highlight the limitations of current tomographic models and the need for targeted seismic investigations with greater resolution of the underlying mantle. This discussion provides the motivation and rationale for a new seismic tomographic model of the mantle beneath North America currently being produced by the authors using a more complete USArray dataset.

How to cite: Kemp, M., Parsons, A., Sigloch, K., Mihalynuk, M., and Stephenson, S.: Tomotectonic constraints on the assembly of the western Arctic region and central Alaska: progress, problems and future direction, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12554, https://doi.org/10.5194/egusphere-egu21-12554, 2021.

The Eastern Arctic is poor studied by offshore drilling. There are some wells drilled on the Alaska shelf, but Russian sedimentary basins are separated from Alaska basins by tectonic structures, therefore seismic complexes could not be traced confidently from Alaska to the North Chukchi Basin. Nevertheless, seismic lines in the Eastern Arctic acquired in last decade, samples from seafloor scarps on the Mendeleev Rise (Skolotnev et al., in preparation) and geologic data from adjacent onshore geology allows to assume the mechanisms and timing of the Eastern Arctic Basins forming. According to data from De-Longa Islands and from sampling on the scarps of the Mendeleev rise, the wide basalt volcanism was acting during ±125-100 Ma. The volcanism related to forming of rift basins all over the Eastern Arctic. On the seismic lines crossing the Mendeleev Rise some structures that could be interpreted as volcanos and Seaward Dipping Reflectors (SDR) are identified at the base of geological section. The top of these structures are traced on the seismic lines, and continue from the Mendeleev rise to the North Chukchi Basin where they are covered by clastic complexes that prograde from the territory of the Early Cretaceous Verkhoyansk-Chukotka Orogen. On this account the North Chukchi Basin started to form not earlier than in Barremian-Aptian. Continuation of Mendeleev Rise into the North Chukchi Basin is confirmed by the data of magnetic anomalies. To the south of the North Chukchi Basin on the Wrangel-Gerald High the volcanic build-ups and associated intrusions are interpreted. Presence of magmatic features in this area is confirmed on the magnetic anomaly map. The volcanic horizons lay below the sedimentary cover of the North Chukchi Basin. Our main conclusion is that Mendeleev Rise and North Chukchi Basin started to form nearly simultaneously during Aptian (Barremian) - Albian time and they compile connected geodynamic system.

How to cite: Startseva, K., Nikishin, A., and Rodina, E.: Mendeleev Rise basalts compile an acoustic basement of the North Chukchi Basin?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8840, https://doi.org/10.5194/egusphere-egu21-8840, 2021.