Lineament Domain of Regional Strike-Slip Corridor: Insight from the Neogene Transtensional De Geer Transform Fault in NW Spitsbergen

Lineaments on regional scale images represent controversial features in tectonic studies. Published models explain the presence of the lineament domains in most geodynamic environments as resulting from the enhanced erosion along strikes normal to the upper crustal regional extension. Despite their success in many tectonic frameworks, these models fail to explain the existing lineament domains in the regional strike-slip corridors that separate regional blocks, including the transform faults. The present paper investigates the lineament distribution in such environments, and specifically presents the results from a study along the shear corridor of the De Geer Transform Fault in the North Atlantic, responsible for the separation and drifting away between Northern Greenland and the Svalbard Archipelago since Oligocene times. The study spans from satellite image analysis and outcrop scale investigations to a more regional analysis on a digital bathymetric model of the North Atlantic\u2013Arctic Ocean. Lineaments were automatically detected in the spectral band 8 (0.52\u20130.9 lm) of a Landsat 7 image (15 m/pixel resolution). A total of 320 image lineaments were extracted from both the regional and the local scale investigations and statistically analyzed. Results from the multi-scalar lineament analyses revealed the existence of a main N\u2013S lineament domain regionally persistent from the De Geer corridor to the western margin of northern Spitsbergen where it relates to the youngest, post-Oligocene, tectonics observed onshore. This is confirmed by field observations showing that the N\u2013S faults represent the youngest brittle deformation system and systematically cut the deformations associated with the building of the Tertiary West Spitsbergen fold and thrust belt. The N\u2013S lineament domain is the result of the activity of a larger, regional scale tectonic feature, NW\u2013SE oriented and responsible for the localized extension within its deformation corridor, the De Geer Transform Fault. A model is presented that involves the presence of a thin upper crust with brittle behavior lying above a deeper crustal layer characterized by a more ductile deformation. The lower layer suffers more diffuse, homogeneous strain. This strain is transmitted to the upper brittle layer, forming clusters of enhanced fracturing zones aligned following the induced stress trajectories. Lineaments develop along these weaker fractured zones, preferentially etched by erosional processes, and align perpendicular to the least horizontal compression (sigma3), which in turn forms an angle to the shear kinematics. In the western part of Spitsbergen, this angle is smaller than 45 due to the transtensional tectonic regime. The proposed model for lineament domain origin in strike-slip environments well integrates the existing models in literature and could be applied to other similar geodynamic contests

New geodetic and gravimetric maps to infer geodynamics of Antarctica with insights on Victoria Land

In order to make inferences on the geodynamics of Antarctica, geodetic and gravimetric maps derived from past and new observations can be used. This paper provides new insights into the geodynamics of Antarctica by integrating data at regional and continental scales. In particular, signatures of geodynamic activity at a regional extent have been investigated in Victoria Land (VL, Antarctica) by means of Global Navigation Satellite System (GNSS) permanent station observations, data from the VLNDEF (Victoria Land Network for Deformation control) discontinuous network, and gravity station measurements. At the continental scale, episodic GNSS observations on VLNDEF sites collected for 20 years, together with continuous data from the International GNSS Service (IGS) and Polar Earth Observing Network (POLENET) sites, were processed, and the Euler pole position assessed with the angular velocity of the Antarctic plate. Both the Bouguer and the free-air gravity anomaly maps were obtained by integrating the available open-access geophysics dataset, and a compilation of 180 gravity measurements collected in the VL within the Italian National Program for Antarctic Research (PNRA) activities. As a result, new evidence has been detected at regional and continental scale. The main absolute motion of VL is towards SE (Ve 9.9 ± 0.26 mm/yr, Vn −11.9 ± 0.27 mm/yr) with a pattern similar to the transforms of the Tasman and Balleny fracture zones produced as consequence of Southern Ocean spreading. Residual velocities of the GNSS stations located in VL confirm the active role of the two main tectonic lineaments of the region, the Rennick–Aviator and the Lillie–Tucker faults with right-lateral sense of shear. The resulting VL gravity anomalies show a NW region characterized by small sized Bouguer anomaly with high uplift rates associated and a SE region with low values of Bouguer anomaly and general subsidence phenomena. The East and West Antarctica are characterized by a different thickness of the Earth’s crust, and the relative velocities obtained by the observed GNSS data confirm that movements between the two regions are negligible. In East Antarctica, the roots of the main subglacial highlands, Gamburtsev Mts and Dronning Maud Land, are present. The Northern Victoria Land (NVL) is characterized by more scattered anomalies. These confirm the differences between the Glacial Isostatic Adjustment (GIA) modeled and observed uplift rates that could be related to deep-seated, regional scale structures

Evidences for Neogene-Quaternary tectonics in Svalbard

Svalbard locates along the De Geer Transform Fault that separates the kinematics of North Atlantic and Arctic Ocean and are a continental rise along the North Atlantic portion of this transform. A fold and thrust belt of Paleogene age boards theWestern margin of the Spitsbergen with a NNW-SSE trend. In the ‘60s theWest – Spitsbergen fold and trust belt was related to the relative movements between Laurentia and Eurasia. Specifically, it was regarded to be a transpressive orogen developed at the intra-continental De Geer Transform margin between the Barents and the Greenland Shelves. This setting was suggested by the necessity of a continental transform off the western margin of Svalbard needed to restore the relative openings of the North Atlantic-Arctic Ocean basins, and the Paleogene age of the fold-belt. Later structural studies in other areas of Svalbard suggested that convergent tectonics have been prevailing during much of the fold and thrust development. However this belt can hardly be regarded as a classical orogen resulting from an active continental margin for the lack of evidence for subduction, synorogenic magmatism, metamorphism or a thickened crust. On the other hand, it would be difficult to merely relate this fold and thrust belt to the De Geer Transform Fault. According to Authors a transform fault should produce structures with vergence away from the fault on both sides, whereas the found direction of tectonic transport in North Greenland is the same as in Spitsbergen, i.e. to the E and NE. In this way the transform separation of North-Greenland and Spitsbergen should postdate the formation of the Tertiary North-Greenland and Spitsbergen fold and trust belt. This rises the question on possible Neogene-Quaternary tectonics in Spitsbergen. Evidence for this younger tectonics includes the occurrence of Quaternary volcanism and thermal springs in the northern part of Spitsbergen and the moderate seismicity in Nordaustlandet. Other clues supporting a recent tectonics derive from the analysis of satellite images and air photos, including the glacier and fluvial drainage suggesting a strong tectonic control. Moreover some authors have found in Ny Alesund an uplift rate from GPS measurements higher than those predicted by postglacial rebound models, again suggesting a tectonic contribution. Preliminary results from field work in the Brogger peninsula confirmed the presence of Neogene-Quaternary tectonics. Marine terraces and fluvio-glacial deposits show several N-S elongated steps along the northern projection of N-S trending faults cutting the Meso-Cenozoic rocks. N-S trending faults have been systematically found in Devonian to Tertiary rocks. These faults are characterised by right-lateral, strike-slip movements and the presence of near surface to sub aerial mineralizations on their surfaces, including kinematic indicators. N-S faults with the same kinematics show the presence of deformed Quaternary clastic, unconsolidated deposits within their shear zones. All the found brittle deformation evidence are compatible with the kinematics of the recent activity of the De Geer Transform Fault

Ice sheet surface lineaments as nonconventional indicators of East Antarctica bedrock tectonics

A recent focus of major international exploration in East Antarctica has been aimed at revealing its bedrock topography and imaging its tectonic architecture and evolution. Here we present the tectonic interpretation of regional-scale lineaments revealed by the Radarsat mosaic of Antarctica on the ice sheet surface in the Vostok\u2013Dome C\u2013 Adventure Basin region. These lineaments appear in the radar backscatter textures as alignments of marked tonal variations with lengths of tens to hundreds of kilometers and were identifi ed using an automated methodology. We explore the origin scenarios for the ice sheet surface lineaments by comparing their azimuthal trends and spatial distribution with the main morphotectonic features of the bedrock. Azimuthal analysis reveals that lineaments cluster around two preferential directions interpreted as structural or tectonic domains. These show strong correlations with azimuths of tectonic fabrics in the bedrock. The main lineament domain parallels the morphotectonic features of the study area, namely the Adventure Basin and the Concordia and Aurora Trenches. The second lineament set corresponds to the mean orientation of the Lake Vostok depression. The spatial analyses of the two lineament domains strengthen our fi ndings and interpretations. Comparisons with wind and ice fl ow directions exclude their infl uence on the identifi ed lineament pattern. Results reveal the tectonic origin of the lineament domains, and demonstrate the method\u2019s usefulness as a tool for tectonic studies of regions characterized by thick covers. These regions include other areas of the East Antarctic craton such as the Gamburtsev Subglacial Mountains, as well as deserts or surfaces of other planets

Ice sheet surface lineaments as nonconventional indicators of East Antarctica bedrock tectonics

A recent focus of major international exploration in East Antarctica has been aimed at revealing its bedrock topography and imaging its tectonic architecture and evolution. Here we present the tectonic interpretation of regional-scale lineaments revealed by the Radarsat mosaic of Antarctica on the ice sheet surface in the Vostok–Dome C– Adventure Basin region. These lineaments appear in the radar backscatter textures as alignments of marked tonal variations with lengths of tens to hundreds of kilometers and were identifi ed using an automated methodology. We explore the origin scenarios for the ice sheet surface lineaments by comparing their azimuthal trends and spatial distribution with the main morphotectonic features of the bedrock. Azimuthal analysis reveals that lineaments cluster around two preferential directions interpreted as structural or tectonic domains. These show strong correlations with azimuths of tectonic fabrics in the bedrock. The main lineament domain parallels the morphotectonic features of the study area, namely the Adventure Basin and the Concordia and Aurora Trenches. The second lineament set corresponds to the mean orientation of the Lake Vostok depression. The spatial analyses of the two lineament domains strengthen our fi ndings and interpretations. Comparisons with wind and ice fl ow directions exclude their infl uence on the identifi ed lineament pattern. Results reveal the tectonic origin of the lineament domains, and demonstrate the method’s usefulness as a tool for tectonic studies of regions characterized by thick covers. These regions include other areas of the East Antarctic craton such as the Gamburtsev Subglacial Mountains, as well as deserts or surfaces of other planets

Intraplate transtensional tectonics in the East Antarctic Craton: insight from buried subglacial bedrock in the Lake Vostok \u2013 Dome C region

""This study presents the results of forward numerical models of a series of sections of the Aurora Trench (East Antarctica). derived from radio echo-sounding data that allowed to reconstruct the 3D shape of the Aurora Fault, a crustal listric. normal fault characterized by a length exceeding 100 km. A similar extensional fault setting allows to replicate the. asymmetric buried morphology of the magnetic basement at the Lake Vostok depression derived by the available gravity. and magnetic profiles. Both the Aurora and Vostok listric fault reach their basal decollment at 34 km depth, possibly. the base of the crust in this intracratonic environment. Integration of these results with the existing geologic interpretations. of the tectonic origin of the Concordia Trench by normal faulting allowed to frame the Concordia, Aurora and. Vostok normal faults within an intraplate transtensional corridor with a left-lateral movement component. The westward. projection of the proposed strike-slip deformation belt may develop in correspondence of an older tectonic lineament. stretching from the Eastern flanks of the Gamburtsev Subglacial Mts to the Lambert rift and characterized by a. poly-phased complex tectonic history. The possible Cenozoic reactivation of these structures is discussed in the paper."

Origin of the Adventure Subglacial Trench linked to Cenozoic extension in the East Antarctic Craton

The Antarctic plate occupies a unique geodynamic setting being mostly surrounded by divergent or transform margins. Major intracontinental basins and highlands characterize its bedrock, buried under the 34Ma East Antarctic Ice Sheet (EAIS). Their formation atop of the cratonic lithosphere in the interior of East Antarctica remains a major open question. Post-Mesozoic intraplate extensional tectonic activity has been proposed for their development and is supported by this work. Here we focus on the Adventure Subglacial Trench (AST) whose origin is poorly constrained and controversial, as currently available geophysical models suggest either extensional or compressional tectonic origin. The AST is an over 250-km-long, 60-km-wide subglacial trough, elongated in the NNW-SSE direction adjacent to the westernmost flank of the Wilkes Subglacial Basin, and is parallel to regional scale alignments of magnetic and gravimetric anomalies. Geophysical campaigns allowed better definition of the AST physiography showing its typical half-graben geometry. The rounded morphology of the western flank of the AST was simulated through tectonic numerical modelling. We consider the subglacial landscape to primarily reflect a preserved relict of the tectonic processes affecting the interior of East Antarctica in the Cenozoic, due to the negligible erosion/deposition capability of the EAIS. The bedrock morphology was replicated through the activity of the listric Adventure Fault, characterized by a basal detachment at the base of the crust (34km) and a vertical displacement of 2.5km. This length suggests its regional/crustal importance. The predicted displacement is interpreted either as a newly formed fault or as the partial reactivation of a weaker zone along a major Precambrian crustal-scale tectonic boundary. The extensional regime in the AST is part of a more extensive 800-km long intraplate corridor characterized by nearly along-strike extension in Cenozoic times with a left-lateral transpressional component. This corridor may represent the effect of far-field stresses induced by plate motions

Lineament Domain of Regional Strike-Slip Corridor: Insight from the Neogene Transtensional De Geer Transform Fault in NW Spitsbergen

Lineaments on regional scale images represent controversial features in tectonic studies. Published models explain the presence of the lineament domains in most geodynamic environments as resulting from the enhanced erosion along strikes normal to the upper crustal regional extension. Despite their success in many tectonic frameworks, these models fail to explain the existing lineament domains in the regional strike-slip corridors that separate regional blocks, including the transform faults. The present paper investigates the lineament distribution in such environments, and specifically presents the results from a study along the shear corridor of the De Geer Transform Fault in the North Atlantic, responsible for the separation and drifting away between Northern Greenland and the Svalbard Archipelago since Oligocene times. The study spans from satellite image analysis and outcrop scale investigations to a more regional analysis on a digital bathymetric model of the North Atlantic–Arctic Ocean. Lineaments were automatically detected in the spectral band 8 (0.52–0.9 lm) of a Landsat 7 image (15 m/pixel resolution). A total of 320 image lineaments were extracted from both the regional and the local scale investigations and statistically analyzed. Results from the multi-scalar lineament analyses revealed the existence of a main N–S lineament domain regionally persistent from the De Geer corridor to the western margin of northern Spitsbergen where it relates to the youngest, post-Oligocene, tectonics observed onshore. This is confirmed by field observations showing that the N–S faults represent the youngest brittle deformation system and systematically cut the deformations associated with the building of the Tertiary West Spitsbergen fold and thrust belt. The N–S lineament domain is the result of the activity of a larger, regional scale tectonic feature, NW–SE oriented and responsible for the localized extension within its deformation corridor, the De Geer Transform Fault. A model is presented that involves the presence of a thin upper crust with brittle behavior lying above a deeper crustal layer characterized by a more ductile deformation. The lower layer suffers more diffuse, homogeneous strain. This strain is transmitted to the upper brittle layer, forming clusters of enhanced fracturing zones aligned following the induced stress trajectories. Lineaments develop along these weaker fractured zones, preferentially etched by erosional processes, and align perpendicular to the least horizontal compression (sigma3), which in turn forms an angle to the shear kinematics. In the western part of Spitsbergen, this angle is smaller than 45 due to the transtensional tectonic regime. The proposed model for lineament domain origin in strike-slip environments well integrates the existing models in literature and could be applied to other similar geodynamic contests

Quanti\ufb01cation of fracturing within fault damage zones affecting Late Proterozoic carbonates in Svalbard

The Cenozoic activity of the De Geer transform fault, which releases the relative movements between of the North Atlantic and the Arctic Ocean, produced a wide deformation zone that presently affects the western coast of the Svalbard (Spitsbergen Island) as testified in the extended rock exposure along the West Spitsbergen fold and thrust belt. In particular, the still ongoing tectonic activity along this transform is responsible for the formation of fault strands characterized by highly fractured damage zones (DZs). These DZs represent hydraulic conduit that steer the pathway of deep fluids (e.g., oil and gas). Understanding the fracturing evolution in fault DZs represent a key factor to model potential reservoirs in the arctic region (and in the Barents Sea area) for various purposes including natural resources development (oil/gas production), gas storage (CO2) as well as nuclear waste disposal. In the present work, we analyze two faults representative of the status of brittle deformation of Vendian carbonates in Svalbard where it was possible to study the fracturing in their DZ. The intensity of brittle deformation was quantified and its spatial variation within the DZ was modeled through an empirical/physical approach that allowed to develop a predictive model to quantify fracturing. This model was prepared by comparing field measurements with an empirical equation taking into account the main fracturing and sealing processes operating during the fault activity. Results can be successfully applied to other carbonate rocks, including the Svalbard analogues of the carbonate reservoirs in the Barents Sea

Tectonic signature on the ice cap surface pattern in Dome C area, East Antarctica

The bedrock morphology in Dome C area in East Antarctica is characterised by the presence of a series of elongated depressions separating ridges, with the Aurora and Concordia trenches representing the major depressions with a length of over 100km. In this area the ice cap reaches a thickness of up to 4000 m, leaving the possibility to have water formation and accumulation at its bottom. Vostok Lake is the largest, most famous among these subglacial depression. The geodynamic scenario responsible for the tectonic origin of these structural depression is not still clear: some Authors hypothesise the existence of an Early Paleozoic regional rifting, others propose a Paleozoic compressional tectonic setting. TheAurora and Concordia trenches can be associated to the Vostok Lake to the West, and together form a set of elongated, roughly N-S to NNW-SSE structural depressions, not perfectly parallel. Therefore, it is reasonable to frame their evolution within a NE-SW trending trans-extensional corridor characterised by left lateral, strike-slip shear, with the depressions associated to faults in horse tail geometry (Cianfarra et al., 2003). The relative young age of the Antarctic Ice Cap, about 38 Ma, compared with the old, Mesozoic age of the former, peneplanised landscape constrains the age of these sharp and fresh structures in Late Cenozoic time. The majority of the observed lakes and depressions are situated in relatively close proximity to ice divides where both the surface slope and ice velocity is small. The presence of this morphology induces variations in the surface texture of the ice cap either due to the movements of the ice sheet on the roughness of the bedrock morphology, and/or to the interaction with active tectonic processes. A series of preferential orientations may relate also to exogenous processes as regional winds. The resulting textural anisotropy of the ice surface can be easily detected from regional scale remotely sensed images. Radarsat mosaic of Antarctica proved a useful tool to investigate the active tectonic processes of the bedrock. Automatic lineament domain analysis performed on a pre-processed subset of the radarsat mosaic allowed to identify the morphological alignment of the surface ice cap whose origin is connected with Cenozoic tectonic processes acting in the bedrock. Images were processed by a series of dedicated algorithms (among which threshold slicing and edge continuity enhancement) to enhance linear textural variations. An original algorithm developed in SID software allowed to detect the main lineament domains of the surface ice cap in the investigated area. The statistical (gaussian) analysis eventually made possible to understand the nature of the linear texture changes as observed in the regional scale images by discriminating features directly produced by wind activity and the tectonic induced linear features. SID analysis showed that the main lineament domain detected on the ice sheet surface is compatible with the principal N-S to NNW-SSE morpho-tectonic bedrock directions in Dome C area (Aurora, Concordia and Vostok structural depression) and that morpho-tectonic directions control the ice-sheet dynamics in the investigated area