Intraplate transtensional tectonics in the East Antarctic Craton: insight from buried subglacial bedrock in the Lake Vostok – 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."

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

Victoria land, antarctica: An improved geodynamic interpretation based on the strain rate field of the current crustal motion and moho depth model

In Antarctica, the severe climatic conditions and the thick ice sheet that covers the largest and most internal part of the continent make it particularly difficult to systematically carry out geophysical and geodetic observations on a continental scale. It prevents the comprehensive understanding of both the onshore and offshore geology as well as the relationship between the inner part of East Antarctica (EA) and the coastal sector of Victoria Land (VL). With the aim to reduce this gap, in this paper multiple geophysical dataset collected since the 1980s in Antarctica by Programma Nazionale di Ricerche in Antartide (PNRA) were integrated with geodetic observations. In particu-lar, the analyzed data includes: (i) Geodetic time series from Trans Antarctic Mountains DEFormation (TAMDEF), and Victoria Land Network for DEFormation control (VLNDEF) GNSS stations installed in Victoria Land; (ii) the integration of on-shore (ground points data and airborne) gravity measurements in Victoria Land and marine gravity surveys performed in the Ross Sea and the nar-row strip of Southern Ocean facing the coasts of northern Victoria Land. Gravity data modelling has improved the knowledge of the Moho depth of VL and surrounding the offshore areas. By the integration of geodetic and gravitational (or gravity) potential results it was possible to better con-strain/identify four geodynamic blocks characterized by homogeneous geophysical signature: the Southern Ocean to the N, the Ross Sea to the E, the Wilkes Basin to the W, and VL in between. The last block is characterized by a small but significant clockwise rotation relative to East Antarctica. The presence of a N-S to NNW-SSE 1-km step in the Moho in correspondence of the Rennick Geo-dynamic Belt confirms the existence of this crustal scale discontinuity, possibly representing the tectonic boundary between East Antarctica and the northern part of VL block, as previously pro-posed by some geological studies

Bedrock erosion surfaces record former East Antarctic Ice Sheet extent

East Antarctica hosts large subglacial basins into which the East Antarctic Ice Sheet (EAIS) likely retreated during past warmer climates. However, the extent of retreat remains poorly constrained, making quantifying past and predicted future contributions to global sea level rise from these marine basins challenging. Geomorphological analysis and flexural modeling within the Wilkes Subglacial Basin is used to reconstruct the ice margin during warm intervals of the Oligocene–Miocene. Flat‐lying bedrock plateaus are indicative of an ice sheet margin positioned >400–500 km inland of the modern grounding zone for extended periods of the Oligocene–Miocene, equivalent to a 2 meter rise in global sea level. Our findings imply that if major EAIS retreat occurs in the future, isostatic rebound will enable the plateau surfaces to act as seeding points for extensive ice rises, thus limiting extensive ice margin retreat of the scale seen during the early EAIS

Inferring bedrock Cenozoic tectonics from ice surface pattern in the Dome C area, East Antarctica

East Antarctica is a Precambrian craton where the thickness of the crust is about 35-40 km. The main geological structures are buried by the extensive continental ice sheet apart from sparse outcrops along the perimeter of the continent. Present understanding of the tectonic evolution of East Antarctica mainly derives from remotely sensed images and geophysical data. Bedrock physiography in Dome C-Vostok region is characterised by Vostok Lake, Aurora and Vincennes basins. A relief region includes the Vostok Subglacial Highlands, the Gamburtsev Subglacial Mountains and the Belgica Subglacial Highlands. Several model have been proposed to tectonically explain the presence of these depressions: the existence of an Early Paleozoic regional rifting, a Paleozoic compressional tectonic setting or else a glacial erosional origin. It is possible to frame the origin and evolution of Lake Vostok and Dome C structural depressions within a common geodynamic scenario: they form a set of elongated, roughly N-S to NNW-SSE structural depressions related to a NE-SW trending trans-extensional corridor. The relative young age of the Antarctic Ice Cap, about 38 Ma, compared to the old, Mesozoic age of the former, peneplanised landscape constrains the age of these structures in Late Cenozoic time. The presence of this subglacial 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. The analysis of the resulting textural anisotropy of the ice surface detected on the Radarsat mosaic of Antarctica proved a useful tool to investigate the active tectonic processes of the bedrock An original algorithm developed in SID software allowed to detect the main lineament domains of the surface ice cap in the investigated area. Gaussian analysis eventually made possible to understand the nature of the linear textural anisotropy by discriminating features produced by exogenous process and the tectonic induced linear features. SID analysis showed that the main lineament domains detected on the ice sheet surface are compatible with the principal N-S to NNW-SSE morpho-tectonic bedrock directions in Dome C-Vostok region (Aurora, Concordia and Vostok structural depression) and that morpho-tectonic directions control the ice-sheet dynamics in the investigated area

Geodynamic constraints of the peri-Tyrrhenian orogen (Tyrrhenian Sea-Apennines) from lineament swarm analysis

""\\"Regional geodynamics is responsible of a series of effects. that notably include tectonics and seismicity. They in turn control. the morphology of the surface of the planet. The regional. dimension of the peri-Tyrrhenian orogen reveals that its. evolution is deeply involved in a lithospheric scale dynamics. As. a result, we expect different observable and\\\\\\\/or measurable effects. at the various scales from the outcrop evidences to the subcontinental. deformation corridors. Effects at the various scales. not necessarily are directly related, and their relations should be. carefully understood taking into account both their geometry and. spatial distribution. A classical example is represented by an en. echelon system. Each single fracture is the effect of a local. extension, yet their spatial distribution shows that these local. stresses are the effect of a larger scale shear zone with a different. orientation.. Remotely sensed images proved the existence on the Earth. surface of linear features with dimensions spanning over three. order of magnitude: from hundreds of meters to thousand of. kilometers. Such features are referred to image lineaments and. are generally related to alignment of morphological features in. continental environment such as onshore crests, ridges, valleys. and troughs. In the oceans lineaments relate to the scars. associated to the seafloor spreading and fracture zones. Synthetic. scale images of tectonically active regions revealed the existence. of groups of regional scale lineaments on the earth surface. appearing as image textural anisotropies. They clusters around. preferential orientations to form lineament domains. These. domains occupies well defined areas to form lineament swarms.. Lineament domain analysis on regional scale images of the. Earth surface proved a useful tool to investigate regions. characterized by active tectonics (Wise et al., 1985; Funiciello et. al., 1977; Cianfarra & Salvini, 2008).. Both the Tyrrhenian Sea and the Apennines are geodynamic. blocks within the collisional puzzle between Africa and Europe. in the Central Mediterranean area.. In this work we explore the possible relations between these. two blocks by lineaments analysis. The found lineament domains. were interpreted as reflecting the structural grain of these two. geodynamic regions. Lineament detection was done by using. original automatic methods. Domains were identified by. statistical analysis. This work analyses lineaments detectable by. simulating different directions of lighting condition on the. DEMs. This allowed to properly evaluate the influence of the. light condition changes in the lineaments produced by. morphological features. The comparison among the analyses. showed that the different lighting conditions induce rotations of. few degrees of the mean azimuth of each lineament domain. This. rotation relate to the result of two contrasting effects: tectonics,. that tends to enhance linear morphologies, and erosion that. progressively smoothes them. Lineament domains characterised. by small rotations relate to morphologies where the tectonic. processes prevail on the erosional ones. Lineament domains. therefore have rotations inversely proportional to their tectonic. activity.\\""

Ice cap surface lineaments in the Vostok-Dome C area, East Antarctica. What are they telling us on the East Antarctica craton tectonics?

Since the recent discovery of subglacial lakes beneath the East Antarctic ice cap, the international scientific community have performed extensive geophysical investigations in order to define the poorly known bedrock physiography of the East Antarctic craton. Increasingly available satellite images of remote regions of the globe have provided preliminary constraints for unravelling the tectonic evolution of the East Antarctic plate. Radio echo sounding (RES) data collected in the Vostok-Dome C region revealed the presence of regional, elongated subglacial valleys, namely the Aurora and Concordia trenches (Tabacco et al. 2003). Their marked asymmetric morphology is similar to that of the Vostok lake depression and relates to the activity of two crustal west-dipping listric normal faults of Cenozoic age with a length of over 100 km (Cianfarra et al., 2003). The Radarsat mosaic of Antarctica shows abrupt changes in tones that run across the mosaic and have a length of hundreds to thousands of kilometres. The mosaic therefore reveals for the first time the presence of regional-scale sub-parallel linear features on the ice cap surface expressed on the image mosaic as sharp tonal variations and marked textural anisotropies (see Fig. 1). These intriguing linear features, up to several hundreds of kilometres long and less than 4-5 kilometres wide, will be referred to as lineaments, following Wise (1969) and Wise et al. (1985). This work investigates how the lineament pattern detected on the ice surface relates to the morpho-tectonic setting of the bedrock in the Vostok-Dome C region. Lineaments detected on the Radarsat mosaic of Antarctica and on the ice surface and bedrock morphology DEMs cluster in domains (sensu Wise et al., 1985), similarly to lineaments in emerged regions. Short, well defined lineaments detected on the high-pass spatially filtered Radarsat image depend on the roughness of the bedrock, which is determined by the tectonic setting of the area. Longer lineaments detected on the high-pass spatially filtered Radarsat image relate to ice cap dynamics. These conclusions agree with the findings of Wise et al. (1985), who demonstrated that regional lineaments on the surface of our planet are the surface expression of recent or active tectonic stress fields in the brittle upper crust. The East Antarctic Ice Sheet represents a thin \u201cfilm\u201d when compared with the about 34 km-thick continental crust. This \u201cfilm\u201d records tectonic processes in the more brittle upper crust, despite differences in the velocity (up to 2 orders of magnitude) of ice dynamics and tectonics. Radarsat images of Antarctica proved to be an effective tool for investigating ice dynamics and bedrock tectonics in the Vostok-Dome C area