1,721,004 research outputs found
Interactions Between Strike-Slip And Thrust Tectonics: Controls on Sand Distributions Through Miocene Basin Arrays, Southern Italy
No full textThe structure and kinematics of substrate entrainment into high concentration sandy turbidites: a field example from the Gorgoglione "flysch" of southern Italy
No full textSandy turbidites commonly show evidence for significant dynamic coupling with their substrate. The resulting deformation can be described using structural kinematic methods, linked to palaeoflow indicators, to better understand the links between flow and entrainment processes. A field example from the syn-orogenic Gorgoglione Flysch, a succession of upper Miocene turbidites deposited into a deforming array of thrust-top basins in the southern Apennine thrust belt, Italy, is described. The succession contains metre-scale packages of alternating sandy turbidites and shales but is notable for containing > 100 m thick, massive sandbodies. These are structureless apart from sporadic horizons of aligned mud clasts. Commonly, the substrate beneath the massive sandbodies is deformed, with minor folds and thrusts verging in the direction of palaeoflow determined from tool marks and flutes at the base of these sandbodies. Structural studies from the base of a selected massive sandbody have identified that the substrate mud has been injected upwards, with flames sheared over in the direction of palaeoflow. Thus the substrate has deformed and become entrained during emplacement of the massive sandy body. At some locations, the substrate can be traced into the overlying deposit, with substrate clay beds becoming boudinaged and entrained into the sandbody. Analysis of the orientation of the mud clasts indicates that this bed disruption and incorporation into the sandy massive- bed turbidite was an organized, viscous process. These features indicate that significant shear stress was partitioned out of the flow and onto the substrate. The incorporation and disruption of substrate into the sandbody suggest that post-disruption strains increase upwards – implying that displacement gradients increased into the flow. These behaviours, showing variations in strain partitioning between the flow and its substrate, are explored in terms of evolving flow dynamics and substrate rheology
Inversion tectonics and structural inheritance in collision mountain belts: An example from the Alps-Apennine system [Tettonica da inversione ed eredità strutturale nelle catene collisionali: un esempio dal sistema Alpi-Appennino]
No full textThe structure of continental lithosphere shows complex variety that is inherited into orogenic belts and influences the localization of contractional structures during mountain building. In the Alps- Apennine system the pre-orogenic template can include arrays of extensional faults. While in some areas of the outer orogenic zones these inherited features may simply reactivate under inversion, more commonly faults show complex, partial reactivation structures. In volumes of distributed strain, pre-orogenic faults may serve to nu- cleate large-scale buckle folds located along, or close to basement- cover interfaces. These different patterns of basement reactivation may reflect spatially-varying strength-depth profiles in continental lithosphere that are themselves inherited from spatially-distinct geo- logical histories. Even when not themselves reactivating, basement faults can control deformation in the overlying sedimentary cover by offsetting otherwise regionally-extensive detachment horizons. The 3D geometry of thrust systems can be strongly compartimentalized by pre-existing cross-faults, such as the oblique lineaments of the Apennines. A comparison between the outer, the intermediate and the inner orogenic zones, with examples from both the Alps and the Apennines, illustrates that the propensity for fault reactivation during mountain building depends on the rheological contrasts between the fault zone and surrounding rocks
Structural inheritance in mountain belts: an Alpine-Apennine perspective
No full textThe geological structure of continental lithosphere shows complex variety that is inherited into orogenic belts and influences the localization and amplification of contractional structures during mountain building. In the Alpine-Apennine sector together with other sectors of the Tethyan orogenic system the pre-orogenic crustal template can include arrays of extensional faults. Other faults can form adjacent to the evolving mountain belt and subsequently become incorporated as the thrust belts migrate into their forelands. While in some areas these inherited features may simply reactivate under inversion, more commonly faults show complex, partial reactivation structures. In volumes of distributed strain, faults may serve to nucleate large-scale buckle folds, for example, along basement-cover interfaces. These different patterns of basement reactivation may reflect spatially varying strength-depth profiles in continental lithosphere that are themselves inherited from spatially-distinct geological histories. Even when not themselves reactivating, basement faults can control deformation in the overlying sedimentary cover by offsetting otherwise regionally extensive detachment horizons. The 3D form of thrust systems can be strongly compartmentalized by pre-existing cross-faults, such as the oblique lineaments of the Apennines. On a large-scale, the distribution of pre-existing faults and other weaknesses may affect the propensity for orogenic contraction in basement and therefore directly control larger-scale tectonic processes. In the central Mediterranean the evolution of slab roll-back and the related growth of overlying extensional basins (e.g. Tyrrhenian Sea) may be strongly modulated by the distribution of rift-related weak zones in the adjacent continental crust. The subduction of continental crust will strongly depend on the inherited structure of this crust, specifically the distribution of deep crust of basic composition. This develops relatively higher densities associated with eclogite metamorphism which act in turn to reduce the buoyancy of thickened continental crust that otherwise serves to inhibit further shortening. Investigating all these aspects, from the scale of bulk crustal compositions to the geometry, timing and strength of earlier fault zones preserved in orogenic belts requires the integration of substantial multidisciplinary geological data sets. The extent to which continental orogenic belts represent the amplification of inherited geological heterogeneities as opposed to self-ordered phenomena modulated by the syntectonic environment remains unclear. © 2006 Elsevier Ltd. All rights reserved
The role of structural inheritance in controlling styles of compressional tectonics: examples from the Apennine-Maghrebian System
No full textSeismic imaging of thrust faults and structural damage: A visualization workflow for deepwater thrust belts
No full textTectonic inversion and structural inheritance in mountain belts
No full textCollisional mountain belts are the product of deformation of former continental margins. During the past 20 years it has be- come increasingly evident that the pre-existing faults, basin structures and the stratigraphic variations they generate can play a significant role in influencing the structural evolution of later compressional tectonics. This Special Issue contains a collection of papers that explore how this type of geological inheritance is manifest in the structural evolution of continental crust, especially associated with orogenesis. It arises from the one-day symposium (G23.03) on ‘‘Tectonic inversion pro- cesses and structural inheritance in mountain belts’’ held at the 32nd International Geological Congress in Florence, Au- gust 2004, that attracted some 31 oral and poster presentations. In summary, the collection of papers in this Special Issue offer a range of new structural interpretations, some applied to well-known tectonic settings, some to novel regions. Thus, although many of the concepts of inversion tectonics are well-established, these papers should promote further tests and applications of these ideas in particular and in the applica- tion of structural geology to illuminate models of continental deformation in general
Comparing thin- and thick-skinned thrust tectonic models of the Central Apennines, Italy
No full textThe geological structure of the Central Apennines
along a section line across the Lazio-Abruzzi carbonate platform
has traditionally been interpreted using a thin-skinned
thrust tectonic model, in which the sedimentary cover has
been detached from an undeformed basement below. Such
models have been used to predict that very large amounts of
crustal shortening (e.g. 172 km over a section 173 km long)
have occurred. Alternatively, in this paper we reinterpret the
surface geology and well data along the same section line using
a thick-skinned thrust tectonic model. Restoration of this
section shows that the amount of shortening (37 km over a
section 158 km long) is considerably lower than previously
predicted; this is accomplished by open buckling of the carbonate
platform, tighter folding of the basin scarp stratigraphy,
and reactivation of pre-existing extensional faults.
Age bracketing on thrust fault movement allows shortening
rates for the two different models to be calculated; these are
<6mm yr−1 for the new interpretation, but over 24mm yr−1
for the equivalent thin-skinned model. This latter value is
significantly greater than shortening rates reported for most
other thrust belts, suggesting that thick-skinned tectonics is a
more satisfactory explanation for the structure of this area.
The two most important implications of this are that subthrust
hydrocarbon plays are largely absent in the area, and
Neogene contractional deformation in this part of the Apennines
resulted in much less crustal shortening than previously
predicted
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