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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.

In this work we present the analysis of the footwall morphology of the Concordia subglacial extensional fault in the East Antarctic Craton. The Concordia Fault is a regional fault zone that extends for almost 200 km. The displacement, up to 1800 m, and the listric geometry were recognized by numerical modeling of the resulting hangingwall bedrock morphology and is responsible for the marked asymmetry that characterizes the corresponding scarp in the Concordia Subglacial Trench. The portion of the footwall in the proximity of the master fault exhibits an excavated morphology, about 500 m deep and up to 5 km wide, showing strong correlation with the master fault displacement. We excluded a predominant glacial and fluvial origin of this morphology considering: (i) the sharp topography of the Concordia Fault, suggesting that the fault activity started after the onset of the ice sheet; (ii) the ice-sheet/bedrock contact is characterized by a general negligible erosion/deposition rates still allowing clast removal; (iii) the lack of significant deposits in the Concordia Trench. We hence explored the possibility that this morphology may result from the combined action of fault-induced fracturing and passive clast removal and scattering by flow and plastic deformation within the ice sheet. We introduced the term tectonic carving for this process. Our modeling shows that tectonic carving relates to the relative fracture intensity in the Concordia fracture zone, that corresponds to the envelope of master and secondary fault damage zones. Fracture intensity depends on the frequency and the displacement of secondary faulting and can be approximated by a normal distribution. Using a Monte Carlo modeling approach we selected the set of parameters that best fits the data set with the carving theoretical curve. The final results of the Monte Carlo analysis show a root mean square of about 50 meters, comparable with the data resolution. This analysis demonstrates a method to unravel the presence of fracture zones in similar, weak erosional environments.

The evolution of deformation patterns during thrust-related folding is of importance for both industrial and academic purposes because of the control that it exerts on the migration and accumulation of fluids in reservoirs. The link between structural position and deformation pattern has been described in both theoretical and field works. On the other hand, the well-documented dependence of deformation structures on the mechanical rock properties and on the environmental conditions indicates that, during folding, structural, stratigraphic, and environmental variables interact to control the deformation pattern within folds. In this work we describe the deformation pattern of the Mt. Catria anticline (Northern Apennines, Italy) and we investigate its variability with (1) the across-strike structural position, and (2) the rock type in the same structural position. Point (1) allowed us to identify and use the syn-folding deformation structures to constrain the fold kinematics. The result of point (2) analyses allowed us to divide the exposed Umbro-Marchean multilayer into three major mechanical units characterised by specific deformation mechanisms and patterns.

Cumulative, polymodal normal (Gaussian distribution) statistics was applied to subsidiary fault data collected from damage zones associated with the Cenozoic Lanterman and Priestley intraplate right-lateral strike-slip fault systems in North Victoria Land, Antarctica. Results show that five Gaussian peaks out of seven in the Lanterman Fault and five out of nine in the Priestley Fault have almost coincident azimuthal values. We named these Gaussian peak pairs as consistent fault sets , arranged in a consistent kinematic architecture that is compatible with the Cenozoic regional strike-slip environment. Angular and kinematic relationships among subsidiary fault sets within the consistent kinematic architecture provide constraints for the inference of the state of stress along the Lanterman and Priestley fault systems. We interpret the fault pattern of the consistent kinematic architecture to be produced by early localisation of the principal displacement zone along pre-existing mechanical discontinuities inherited from the Early Paleozoic Ross Orogeny. Shear localisation was followed by subsidiary faulting at an angle to the principal displacement zone according to the Mohr–Coulomb–Byerlee failure criterion.

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.

The evolution of surficial structures at the toes of orogens arises from the complex interplay between tectonic and surface processes. The internal architecture of syntectonic sediments has been shown to provide useful insights on the kinematic mechanism of folding. Two-dimensional templates of growth strata patterns associated to thrust-related anticlines are available in the literature. In this paper, we show the results of three-dimensional numerical modelling of growth fault-bend folds, fault-propagation folds, fixed limb length decollement folds and fixed limb dip decollement folds. We point out that total thickness contour maps, single syntectonic layer contour maps, and above all, the computation of their directional first-derivative maps, provide useful templates for inferring the kinematic mechanism of folding when compared with similar maps from natural examples. Application of these three-dimensional numerical models includes the comparison and supervised best fit with three-dimensional seismic reflection data sets. Numerical results are contrasted with the growth strata map patterns of the Mediano, Oliana and Pico del Aguila anticlines, in the Spanish Pyrenees.

In fault-related folds that form by axial surface migration, rocks undergo deformation as they pass through axial surfaces. The distribution and intensity of deformation in these structures has been impacted by the history of axial surface migration. Upon fold initiation, unique dip panels develop, each with a characteristic deformation intensity, depending on their history. During fold growth, rocks that pass through axial surfaces are transported between dip panels and accumulate additional deformation. By tracking the pattern of axial surface migration in model folds, we predict the distribution of relative deformation intensity in simple-step, parallel fault-bend and fault-propagation anticlines. In both cases the deformation is partitioned into unique domains we call deformation panels. For a given rheology of the folded multilayer, deformation intensity will be homogeneously distributed in each deformation panel. Fold limbs are always deformed. The flat crests of fault-propagation anticlines are always undeformed. Two asymmetric deformation panels develop in fault-propagation folds above ramp angles exceeding 29°. For lower ramp angles, an additional, more intensely-deformed panel develops at the transition between the crest and the forelimb. Deformation in the flat crests of fault-bend anticlines occurs when fault displacement exceeds the length of the footwall ramp, but is never found immediately hinterland of the crest to forelimb transition. In environments dominated by brittle deformation, our models may serve as a first-order approximation of the distribution of fractures in fault-related folds.

The nucleation and growth of thrust fault-related folds has been simulated using high-resolution sandbox Coulomb wedge-type analogue models. Thrust-related anticlines grew progressively from initial layerparallel shortening, to decollement folding, thrust-tip folding and eventually thrust-ramp folding. Thrust ramps nucleated in the central sector of the overturned forelimb of decollement folds, as a consequence of limb thinning. Thrust-tip folding occurred during outward migration of the ramp tips. The fault-propagation rate was greater at the lower ramp tip, which quickly joined the basal thrust flat, while folding continued beyond the upper tip. The development of the analogue model thrust fault-related folds by progressive changes in kinematics, from decollement folding to thrust-tip folding and finally thrust-ramp folding, compares well with analyses of naturally occurring thrust fault-related folds.