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One of the three narrow rift belts that mark the southern end of the East African Rift System (EARS) intersects the Makgadikgadi Basin of northeastern Botswana. Although tectonic activity in the region is known to have influenced the evolution of these pans, the interrelationship between shoreline geometry, fault strikes, and the intersection of the underlying tectonic terranes has yet to be fully realized. We analyzed faults and subsurface structures in the region of the pans using a field investigation in combination with satellite imagery and geophysical data, to constrain the influence that the regional tectonic regime has had on the formation of the present-day pan geometry. We find that pan shorelines are controlled by the intersection of three preferred fault orientations which can be understood in the context of the "older" terranes they overlie, namely the Magondi Belt and the Limpopo Belt. We propose that the pronounced curvature of the southern Magondi Belt has influ-enced the eastward curvature of the rift-related faults and was likely produced by the impingement of the developing fold belt on the Zimbabwe Craton. Furthermore, limited focal mechanism solutions data from earthquakes north and south of the pans suggests a change in regional extension direction from NW-SE to NE-SW. Determining the relationship between these fault orientations and the underlying tectonic terrains is an important step in understanding the formation of the Makgadikgadi Basin, and more broadly the current tectonic regime of Botswana. The evidence of fault-controlled shorelines within an evaporitic environment may also have implications for regional groundwater activity.

A lithologic investigation has been performed on the Tarn Flat area, Antarctica, based on Landsat-TM and SPOT-XS processed images and on radiometric field data acquired by an EXOTECH radiometer. Results from the field survey, performed during the austral summer 1994-95 expedition, were used to verify the ability of satellite images to discriminate between the main rock. Principal Component transformation allowed to enhance the spectral information of rocks, despite the high band correlation of TM data, while high-pass filtering and TM-SPOT merging allowed a fairly accurate detection of morphologic features. A supervised classification has been carried out on the processed satellite images as a further demonstration of the utility of remote observation to investigate extreme environments.

An extensive distribution of water-altered equatorial layered deposits (ELDs) characterizes the densely cratered terrain of Arabia Terra (AT), Mars. The majority of these deposits reside within craters and are easily identified by laterally continuous layering. The processes that led to their formation have been widely investigated, but remain unresolved. Furthermore, their precise spatial distribution as a whole, as well as their relationship to one another individually, has yet to be fully appreciated. This work examines 1,013 craters and emphasizes 45 that were observed to contain ELDs within the eastern half of AT. We present the statistical relationships between crater characteristics (e.g., location, diameter, depth), as well as evidence supporting a southeast-northwest facies change. The 30-2,000-m range of measured deposit thicknesses, accompanied with individual layer thicknesses, correlate with crater elevation either due to water level differences within craters, or a proximal-distal relationship to the source. Air fall or fluid expulsion appear to stand out among all the prevailing depositional hypotheses, however the volume required to fill these craters in an ash fall scenario is in opposition with the locations of known volcanic provinces and the volume of ash that volcanic eruptions produce. This new evidence of a regional facies change provides a unique opportunity to better understand past climate and sedimentary processes on Mars, as well as the putative groundwater level in ancient AT. Ultimately, our results do not agree well with a unified depositional method for these deposits and the possibility of mixed origins should be taken seriously.

The South Polar Terrain (SPT) of Enceladus is a site with eruptions of gas and water ice particle plumes, which indicate internal geodynamic activity. These eruptions are located along a series of tectonic structures, that is, the Tiger Stripe Fractures (TSF), which are composed of regularly spaced, linear depressions. The SPT is surrounded by sinuous chains of ridges and troughs (the Marginal Zone). To unravel the tectonics that affect the region and its evolution, we performed specific structural mapping and quantitative analyses of brittle features from remotely sensed images. The results are consistent with a block rotation model, in which several tectonic regimes coexist. The TSF are left-lateral strike-slip faults that bound rigid elongated blocks. The blocks rotate clockwise and are enclosed in a regional scale right-lateral kinematic framework expressed in the Marginal Zone. These two opposite and complementary kinematic regimes induce transtensional and transpressional regimes within the SPT. An evolutionary tectonic model is proposed for the past and future evolution of the SPT. This model confirms the role of tectonic-related kinematics in icy satellites and contributes to preparations for future missions.

GNSS networks in Antarctica are a fundamental tool to define actual crustal displacements due to geological and geophysical processes and to constrain the glacial isostatic models (GIA). A large network devoted to the detection and monitoring of crustal deformations in the Northern Victoria Land (Victoria Land Network for DEFormation control – VLNDEF), was monumented during the 1999–2000 and 2000–2001 field campaigns, as part of Italian National Program for Antarctic Research and surveyed periodically during the Southern summer seasons. In this paper, GPS observations of VLNDEF collected over a more than 15-year span, together with various selected POLENET sites and more than 70 IGS stations, were processed with Bernese Software, using a classical double difference approach. A solution was obtained combining NEQs by means of ADDNEQ2/FODITS tools embedded in Bernese Software. All the Antarctic sites were kept free and a subset of 50 IGS stations were used to frame VLNDEF into ITRF2008. New evidence provided by analysis of GPS time series for the VLNDEF network is presented; also displacements along the vertical component are compared with the recently published GIA models. The absolute velocities indicate an overall displacement of the northern Victoria Land region along the south-east direction (Ve = 10.6 mm/yr, Vn = −11.5 mm/yr) and an average uplift rate of Vu = 0.5 mm/yr. Two GIA models have been analyzed: ICE-6G_C-VM5a proposed by Argus et al. (2014), Peltier et al. (2015) and W12A_v1 by Whitehouse et al. (2012a,b). Up rates, predicted over the VLNDEF sites by the mentioned GIA models, have been extracted and compared with those observed. A preliminary comparison with GPS-derived vertical rates shows that the Victoria Land ICE-6G_C-VM5 and W12A_v1 GIA models predict overestimated uplift rates of 0.7 and 0.9 mm/yr weighted mean residuals respectively. The mean horizontal relative motions within the Victoria Land (VL) area are in most cases negligible, while only a few points exhibit horizontal velocities greater than the confidence level. Such a residual horizontal velocity field could represent some of the tectonic characteristics affecting VL, characterized by block faulting, tilting along NE striking and SE dipping extensional faults. Uplift rates, highlighted in the present paper depict a well defined spatial pattern in the investigated areas. Northward, all sites show a general positive trend up to 2.3 mm/yr. In the central and southern areas small negative trends (up to −1.3 mm/yr) were detected in the vertical displacements. Only the site VL06, located atop the Mt. Melbourne volcano, does not concord with such a general reading, as it is representative of the volcanic complex’s evolution. Observed and predicted uplift rates increase westward (inland) where the ice-load increases. The same behavior is predicted southward by the GIA models; whereas GPS values decrease toward the south pole, due to the movements of a few sites reflecting the neotectonic phenomena acting in the Victoria Land region.

Brittle deformation on Ganymede surface is represented by grooves tectonic linear landforms. These are regional scale structures that show well-defined morphology from straight to curvilinear. High density of grooves occupies most of the light terrain of the satellite, the grooved terrain. We map grooves on the USGS Voyager and Galileo Mosaic of Ganymede in order to unravel their spatial distribution and tectonic setting. A total of 14,707 grooves were identified, digitized and statistically analysed. A quantitative structural geology approach was used to classify grooves, by considering their azimuth and regional rotation. This procedure allowed to recognize a total of four groove families, named the NE, WNW, NW, and N-S super-systems. The presented structural map represents a tool to study the stress conditions associated with the groove formation and evolution. This map also aims to contribute to the scientific preparation of the upcoming missions and future exploration of Ganymede.

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 &plusmn, 0.26 mm/yr, Vn &minus, 11.9 &plusmn, 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&ndash, Aviator and the Lillie&ndash, 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&rsquo, 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.

According to the classical paradigm of plate tectonics the cratonic area of the inner part of South America is considered tectonically stable. Nevertheless, the role of neotectonics on the shape of the Brazilian landforms has been demonstrated by several authors. In this work we perform a lineament domain analysis to explore the regional meaning of the sparse and local evidences of neotectonics within Southeast Brazil and frame them in a regional tectonic evolutionary model. Results from lineament analysis allowed finding out two main domains, NW-SE and NE-SW trending. These structural directions frame within an E-W strike-slip corridor characterized by a poly-phased tectonic history. A pre-Neogene left-lateral shear was followed by a right lateral movement whose activity is presently ruling the landform evolution of the region. The two identified structural trends from lineament analysis may represent the Cenozoic reactivation of ancient weakness zone and relate to the upper Cenozoic South Atlantic drifting and N to NW movement of the South America.

SUMMARY We present the interpretation of 11 radio echo-sounding (RES) missions carried out over the Vostok‐Dome Concordia region during the Italian Antarctic expeditions in the period 1995‐ 2001. The extension and the density of the radar data in the surveyed area allowed to reconstruct a reliable subglacial morphology and to identify four relevant morphological structures namely: the Aurora trench, the Concordia trench, the Concordia ridge and the South Hills. These structures show evidence compatible with the presence of tectonic features. Morphological considerations indicate their development in Cenozoic time. Hybrid cellular automata (HCA)based numerical modelling allowed to justify a possible role played by the tectonics of the Aurora and Concordia trench evolution. This was accomplished by matching the bed profiles along opportunely projected sections with the modelled surfaces as derived by the activity of normal faults with variable surfaces within the continental crust. The Vostok‐Dome C region is characterized by a large number of subglacial lakes. From the analysis of basal reflected power echo, we identified 14 new lakes and obtained information about their physiography as well as their possible relations with tectonics. We propose a grouping of subglacial lakes on the base of their physiography and geological setting, namely relief lakes, basin lakes and trench lakes. Relief lakes located in the Belgica subglacial highlands and are characterized by sharp and steep symmetric edges, suggesting a maximum water depth of the order of 100 m. Their origin may well relate to localized, positive geothermal flux anomalies. Basin lakes located in the Vincennes subglacial basin and are characterized by wider dimension that allow the development of well-defined, flat ice surface anomalies. Trench lakes characterize the Aurora and Concordia trenches as the possible effect of normal fault activity.

Fault-bend folding is a common folding mechanism in thrust and fold belts worldwide. The widely used kink-band geometric model of fault-bend folding necessitates complex ramp segmentations to reproduce the rounded shape of many natural thrust related anticlines. Curvilinear hinge sectors provide a geometric and kinematic alternative solution to kink bands for modelling curved-hinge folds. We developed an analytical solution for modelling fault-bend folding using circular hinge sectors. The velocity field of this kinematic solution is different from that associated with the classical, kink-style model. Our solution predicts the development of curvilinear anticlines above staircase fault geometries, the occurrence of limb rotation and, consequently, the development of rotational syngrowth wedges on both the forelimb and the crest. Conversely to the kink-style kinematics, curvilinear hinge sectors imply a dependence of deformation intensity from the fold shape and stratigraphic position of the folded layer. Application to natural thrust-related anticlines validates the effectiveness of curvilinear fault-bend folding.

Field data on Cenozoic faults and the McMurdo dyke arrays in the Reeves Glacier–Mawson Glacier area, Victoria Land, Antarctica, allow us to support noncoaxial transtensional tectonics along the N–S-trending western shoulder of the Ross Sea. Dyke injection within a crustal-scale right-lateral strike-slip shear zone is testified by magma filled, tension gash-like arrangements within some master fault zones, and by the left-stepping arrangements of dykes in the intrafault zones. The noncoaxiality of deformation is shown by the re-activation of many dyke walls as right-lateral strike-slip faults. This suggests an increase in the strike-slip component over time along the western shoulder of the Ross Sea. Our data support the relevance of transtensional to strike-slip tectonics for triggering melting and controlling the geometry and modes of magma emplacement.

A semipermanent Global Positioning System (GPS) network of 30 vertices known as the Victoria Land Network for Deformation Control (VLNDEF) was set up in the Austral summer of 1998 in northern Victoria Land (NVL), including Terra Nova Bay (TNB), Antarctica. The locations were selected according to the known Cenozoic fault framework, which is characterized by a system of NW‐SE regional faults with right‐lateral, strike‐slip kinematics. The TNB1 permanent GPS station is within the VLNDEF, and following its installation on a bedrock monument in October 1998, it has been recording almost continuously. The GPS network has been surveyed routinely every two summers, using high‐quality, dual‐frequency GPS receivers. In this study we present the results of a distributed session approach applied to the processing of the GPS data of the VLNDEF. An improved reference frame definition was implemented, including a new Euler pole, to compute the Antarctic intraplate residual velocities. The projection of the residual velocities on the main faults in NVL show present‐day activities for some faults, including the Tucker, Leap Year, Lanterman, Aviator, and David faults, with right‐lateral strike‐slip kinematics and local extensional and compressional components. This active fault pattern divides NVL into eight rigid blocks, each characterized by its relative movements and rigid rotations. These show velocities of up to several millimeters per year, which are comparable to those predicted by plate tectonic theory at active plate margins.

Fault-related folds in fold-and-thrust belts and accretionary prisms are commonly simulated by three end-member classes of geometric models: decollement folding, fault-propagation folding, and fault-bend folding. A given model produces a fold shape that depends on the amount of shortening, the fault shape and, eventually, the fault propagation history. The great variety of geometric solutions implies that the final fold shape is adequate to distinguish among different folding mechanisms only in a limited suite of cases. Additional information to better constrain fold kinematics is provided by the analysis of growth strata patterns, which passively register the progressive evolution of deformation in the substratum. Availability of growth strata pattern templates associated with different geometric and kinematic solutions provides a useful tool for inferring the dominant kinematic pathways of natural thrust-related structures. In this paper, we present growth strata patterns associated with double-edge fault-propagation folding. The influence of the sedimentation rate, the fault shape, and the fault S/P ratio (i.e. slip versus ramp propagation rate) on growth strata architectures are investigated. Geometrical modelling and application to natural examples indicate that double-edge fault-propagation anticlines are characterised by growth triangles on both limbs. Their position and geometry relate to the ramp shape and propagation history, and on the sedimentation rate.

Fault-propagation folding is a common folding mechanism in thrust-and-fold belts and accretionary prisms. Several geometrical models relating the fold shape to the ramp shape have been proposed. In all these models, ramps always emanate from a basal fault and propagate upwards. We have developed a new kinematic and geometric model of fault-propagation folding, named double-edge fault-propagation folding. The model simulates folding at thrust ramps as a function of their nucleation site and propagation history within the folded multilayer. The fold shape depends on the initial length and location of the ramp, its dip, and the S / P ratio (i.e. incremental ramp slip versus propagation) of both the upper and lower ramp tips. This solution increases the geometrical flexibility of fault-propagation folding reducing, for example, the direct dependence between the backlimb dip and the ramp dip, as double-edge fault-propagation folding is characterised by a backlimb panel not necessary parallel to the ramp. Non-parallelism between the ramp and the backlimb is commonly observed in thrust-related anticlines, within fold-and-thrust belts and accretionary prisms. The excess layer-parallel shear imposed by the development of double-edge fault-propagation folding can be easily accommodated by discrete faulting and/or penetrative deformation. The dependence of the fold shape on the fault behaviour provides a tool for including the role of mechanical stratigraphy and environmental conditions of deformation into kinematic models. Natural examples of anticlines that could be modelled by double-edge fault-propagation are presented.

The Ethiopian Rift is characterized by several Quaternary calderas. Remote sensing and field analyses were used to investigate the regional structural control on three calderas (Fantale, Gariboldi, Gedemsa) in the axial part of the rift. These calderas are located along the Wonji Fault Belt (WFB), a zone of Quaternary NNE–SSW normal faults and extensional fractures. The three calderas show E–W elongation and major E–W vent alignments, oblique with regard to the mean NW–SE extension direction. No significant evidence of E–W tectonic structures has been found near the calderas, the only relevant systems being those of the WFB. Conversely, left-lateral E–W-trending faults are present at the rift borders and on the Nubia and Somalia plateaus, implying a predominant pre-rift activity. The E–W fractures were partly reactivated during rifting, possibly controlling the development of the magma chambers. Thus, the E–W elongation of the calderas would be the surface expression of such a control, rather than the result of regional extension. An evolutionary model on the role of different structures on magmatism at different crustal levels within the rift is proposed.