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Orogenic curvatures can have various origins and are widely debated worldwide. In the Poland-Ukraine border area, the Outer Western Carpathians are characterized by a marked curvature. The origin of this curvature was analysed by integrating stratigraphic information with structural constraints and anisotropy of the magnetic susceptibility (AMS) data. Hangingwall frontal ramp domains are characterized by a relatively simple deformation dominated by layer-parallel shortening and folding around a regional NW-SE trending axis, recorded by an AMS lineation with a similar trend. On the other hand, the N-S trending hangingwall oblique ramp domain is characterized by maximum AMS axes recording transpressional strain either dominated by simple shear (sub-horizontal AMS lineation) or pure shear (steeply plunging AMS lineation) components. Early Miocene basin inversion with two distinct depocentres created a number of different detachment surfaces and thickness variations for the sedimentary successions involved in thrusting. The main depocentre of the Lower-Middle Miocene foredeep was originally located in the recess area of the curved Carpathian front. On the other hand, the occurrence of a salient to the west resulted in the axial zone of the foreland flexure being filled with allochthonous units, thereby dramatically reducing the accommodation space for foredeep sediments in this area. Our results suggest that thrust-belt geometry was controlled by the inherited Mesozoic extensional basin architecture.

In this study we performed a fracture analysis on a Cretaceous bedded carbonate succession well exposed in the Sorrento Peninsula. The studied succession includes stratigraphic units that are very similar to the productive units of the buried Apulian Platform reservoir rocks in southern Italy. We analyzed eight carbonate beds, including both limestones and dolomites. The basic technique used in this study consisted of measuring fractures along bedding-parallel scan lines. For one limestone bed, a microscale scan line, about 15 cm long, was also analyzed using a digital microcamera. Provided the cumulative distribution of fracture apertures is well described by a power law, our analysis shows how the uncertainty in the estimate of fracture aperture cumulative frequencies grows for large aperture values. This feature results in a large uncertainty in the estimate of the slope of the least-squares line (in a bi-logarithmic diagram) approximating the data distribution, which is the exponent of the power law. As the latter represents a fundamental parameter characterizing a fracture set and fracture distribution over different scales, reducing the uncertainty in the estimate of the slope of the curve represents an important objective of quantitative fracture analysis. This is obtained in this study by the application of multi-scale analysis, and by integrating micro-scan line data with classic outcrop-based scan line analysis. The quantification of uncertainties in the cumulative distribution estimates of fracture apertures is performed by analyzing in detail the spacing distribution – and consequently fracture-density distribution – for each aperture value. Our results suggests that a meaningful statistical analysis of fracture attributes such as aperture (or opening displacement) may be effectively carried out by using properly determined confidence intervals and by the integration of outcrop-based and micro-scan line data sets.

Mathematical models are proposed to describe heterogeneous shear zones characterized by variation thickness with time. These models take into account several combinations of deformation type regime (simultaneous simple shear, pure shear, and volume change) and degree of strain localization. Increasing or decreasing shear zone thickness results, respectively, from strain hardening where deformation progressively diffuses into the host rock, and strain softening where deformation gradually localizes within a narrow zone. Shear zone models are made of a series of layers, each characterized by homogenous strain. A quantitative evaluation of displacement–thickness relationship and finite strain development may be obtained from each model. Temporal evolution depends on the following parameters: (i) rate of shear strain hardening/softening, (ii) initial shear strain increment imposed to the system, and (iii) thickness of homogenously deformed units within a layered shear zone. Based on data coming from natural shear zones, displacement rates may be obtained independently of shear zone thickness.

Coaxial strain history, although not representing a common situation in rocks, can provide the opportunity to quantify very important parameters such as the amount of volume change occurring during compaction and tectonic deformation. In the case of coaxial superposition of compaction and tectonic plane strain, a co-ordinate system is defined with the x-y plane lying parallel to bedding and the z axis normal to it, and with the x-z plane corresponding to the plane in which tectonic strain occurs. Bulk strain data are represented on a simple deformation plot with axes 1 + e x , 1 + e x (where e x and e x are the finite extensions along the x and z axes of the co-ordinate system, respectively). With respect to the conventional Flinn diagram, the use of this plot for representing coaxial deformation paths brings several advantages, in that: (1) the magnitudes of the finite strains and their orientation with respect to the chosen co-ordinate system are represented; (2) the volume changes occurring during both compaction and tectonic strain are easily visualized for all the stages of progressive deformation; and (3) the transitions from the oblate to the prolate shape (and vice versa) of the finite strain ellipsoid during progressive deformation are shown continuously, without the artificial zig-zag pattern of the Flinn diagram.