Folding (Structural Geology)

This paper examines the geology of the Lagrasse area, southern France. The stratigraphy in the area ranges in age from 72ma-52ma with recent Quaternary superficial deposits noted. All the strata in the region are calcite bearing, this along with tectonic influences in the area forms the rugged valley filled landscape around Lagrasse. The area is located in the Pyrenean foothills and has noticeable deformation throughout many units especially the Ribaute Limestone, likely deformed during the Eocene. The tectonic processes before the Eocene that led to the formation of the Pyrenees are also responsible for the depositional environments of the strata. The depositional settings are controlled by related processes such as foreland basin formation. The rugged landscape created makes the region prone to flooding with narrow valleys that have to share waterways and roads making natural disasters ever present in the area such as disastrous floods in 1999 and 2014.

This is MATLAB's 10 most easy & most basic programs that I's supposed to submit in my practicals. In this document I've complied 10 MATLAB programs from basic to advanced through intermediate levels, But overall they are for beginners only. It's only a 26 pages doc. for academic purposes. well, What else a student can offer you, huh? LOLz

The Sitapahar Anticline and its adjacent areas are characterized by a series of parallel ranges of hills trending NNW-SSE. They are extensional expression of the Indo-Burman Folded Belt of Bengal foredeep by compressional forces during Mio-Pliocene. This anticline is an asymmetrical fold with steeper western flank and gentler eastern flank.
In terms of lithostratigraphy, the area can be divided into 5 major rock units. They are (from bottom to top) - silty shale, sandstone-shale alternation, brownish sandstone, bluish gray shale and yellowish brown sandstone. This rock units are correlated with Bhuban Formation, Boka Bil Formation, Tipam Sandstone Formation, Girujan Clay Formation, and Dupi Tila Formation respectively.
The study based on rock type, grain size, shape, sorting of grain, cementing materials, sedimentary structures reveals that the sediments were deposited in fluvial to shallow marine environment.

Lipatan adalah salah satu struktur geologi pada singkapan batuan yang berbentuk seperti gelombang undulasi pada suatu lapisan kulit bumi, struktur awalnya yaitu vertikal atau horizontal seperti sedimen strata dan berkembang selama deformasi serta memiliki sifat plastis atau lentur. Lipatan adalah struktur yang paling jelas dan umum yang menunjukkan adanya deformasi ductile di bumi. Terlepas dari daya tarik estetika, lipatan biasanya dipelajari untuk mengungkapkan geometrinya. Bentuk, orientasi, dan skala lipatan menjadi sangat penting dalam menemukan deposit yang bernilai ekonomis dan dalam memprediksi kelanjutan dari deposit (resetvoir) yang biasanya berupa minyak dan gas. Reservoir umumnya terjebak di bagian atas lipatan (antiklin atau convex up). deposit bijih dapat terkonsentrasi pada zona lengkungan yang paling tajam dari lipatan (hinge zone) atau terletak di lapisan tertentu yang telah terlipat. Gambar 1 oil yang terjebak pada antiklin Di luar kepentingan ekonomi, lipatan memberikan catatan dari proses tektonik yang terjadi di Bumi. Berbagai bentuk lipatan dalam batuan harus mencerminkan kondisi fisik (seperti stres, suhu, dan tekanan) dan sifat mekanik batuan yang ada saat lipatan berkembang. Jika kita bisa memahami makna geometri lipatan, maka kita akan memiliki kunci berharga untuk memahami kondisi deformasi di Bumi. Deskripsi lipatan harus bebas dari implikasi genetik, karena hal genetik memerlukan penafsiran asal lipatan, yang mungkin tidak dipahami dengan baik. Akhirnya, Namun, kami ingin mengasosiasikan geometri lipatan dengan mekanisme pembentukan sehingga deskripsi yang akurat dapat menghasilkan interpretasi yang berguna. Tujuannya adalah untuk memahami bagaimana lipatan mencapai berbagai macam geometri yang terlihat di alam dan dengan demikian dapat menyimpulkan kondisi permukaan bumi di mana lipatan terbentuk.

The late Paleozoic collision between Gondwana and Laurussia resulted in the polyphase deformation and magmatism that characterizes the Iberian Massif of the Variscan orogen. In the Central Iberian Zone, initial continental thickening (D 1 ; folding and thrusting) was followed by extensional orogenic collapse (D 2) responsible for the exhumation of high-grade rocks coeval to the emplacement of granitoids. This study presents a tectonometamorphic analysis of the Trancoso-Pinhel region (Central Iberian Zone) to explain the processes in place during the transition from an extension-dominated state (D 2) to a compression-dominated one (D 3). We reveal the existence of low-dipping D 2 extensional structures later affected by several pulses of subhorizontal shortening, each of them typified by upright folds and strike-slip shearing (D 3 , D 4 and D 5 , as identified by superimposition of structures). The D 2 Pinhel extensional shear zone separates a low-grade domain from an underlying high-grade domain, and it contributed to the thermal reequilibration of the orogen by facilitating heat advection from lower parts of the crust, crustal thinning, decompression melting, and magma intrusion. Progressive lessening of the gravitational disequilibrium carried out by this D 2 shear zone led to a switch from subhorizontal extension to compression and the eventual cessation and capture of the Pinhel shear zone by strike-slip tectonics during renewed crustal shortening. High-grade domains of the Pinhel shear zone were folded together with low-grade domains to define the current upright folded structure of the Trancoso-Pinhel region , the D 3 Tamames-Marofa-Sátão synform. New dating of syn-orogenic granitoids (SHRIMP U\ \Pb zircon dating) intruding the Pinhel shear zone, together with the already published ages of early extensional fabrics constrain the functioning of this shear zone to ca. 331–311 Ma, with maximum tectonomagmatic activity at ca. 321–317 Ma. The capture and apparent cessation of movement of the Pinhel shear zone occurred at ca. 317– 311 Ma.

Deformasi batuan yang berbentuk gelombang sinusiodal dimana gaya yang bekerja pada batuan tidak melampaui batas elastisnya, sehingga batuan tidak mengalami persesaran. Lipatan sinklin adalah bentuk lipatan yang cekung ke arah bawah, sedangkan lipatan antiklin adalah lipatan yang cembung ke arah atas.

This contribution provides a case example on the generation of large-scale recumbent folds in syn-orogenic gran-itoids. We analyze the progressive reworking of extension-related structures into later ones after a period of crustal thickening. The Padrón migmatitic dome formed after the climax of the Gondwana-Laurussia collision in the late Paleozoic. Petrostructural analysis carried out in the eastern flank of this dome reveals that extensional flow resulted in progressive exhumation of mainland Gondwana, which rested under peri-gondwanan alloch-thonous terranes and a suture zone during maximum crustal thickening. Exhumation proceeded up to upper crust levels (andalusite stability field) along with partial melting of the middle-lower crust and with the generation of granitoid laccoliths during an early extensional stage. Newly-formed lithological and mechanical anisot-ropies, such as the presence of variably-sized sheet-shaped bodies of syn-orogenic granitoids, provided a favorable rheological setting for fold nucleation during the intermediate stages of extension. In extending oro-genic crust, whether recumbent folds occur after significant melt production depends on the lateral/vertical flow ratio, and on the orientation of deforming bodies with regard to kinematic/strain axes. We suggest that subhorizontal extensional flow dominated over vertical flow during the early and intermediate stages of the evolution of the Padrón dome. A component of vertical (diapiric) flow caused progressive tilting of the sheet-like bodies and obliquity respect to strain axes. This resulted in the development of regional-scale folds at the expense of syn-orogenic granitoids, such as in the case of the Portomouro recumbent synform. Extensional ductile flow was oblique to the trend of the orogen during the whole process, and directed to the NNW during the formation of recumbent folds. Non-coaxial shearing favored an (NNW-SSE) elongate shape for the syn-kinematic granitic massifs as well as the subsequent nucleation of recumbent folds. Deformation concentrated along discrete detachments during the late stages of extension.

The oblique Segre ramp zone between the eastern and central Pyrenees constitutes one of the major unsolved problems in the southern Pyrenees. Its geometry and evolution not only solve the eastern boundary of the South Central Unit but is also an advanced step for the recognition of the whole evolution of the southern Pyrenees.
A network of 15 perpendicular seismically supported cross-sections is presented in this work. Some of these are balanced and restored, allowing shortening calculations. Cross-cutting relationships between structures and syntectonic sediments in addition to internal geometries of these sediments were extensively studied to constrain the timing of thrusting.
The final versions of these 15 cross-sections are the result of a double loop of testing based on: a) the comparison of thrust geometries, rotation, amount of shortening and ages of thrusting between different cross-sections, and b) the fit between restored cross-sections and maps (palinspastic maps). The resultant structure is geometrically homogeneous and geologically consistent. The agreement between restored cross- sections and maps results in a 3D restoration.
13
The network of cross-sections shows the varying structure of the southern Pyrenean cover thrust sheets along the strike for ~150 km from the easternmost cross-section J-1 to the westernmost cross-section J-13. The evolution, shortening and rates of shortening for the southern Pyrenean thrust sheets can be briefly summarised as follows:
The positive inversion of the Mesozoic extensional basins and further southward motion restrained the irregular geometry of the upper and older Pyrenean thrust sheets (Pedraforca and South Pyrenean Unit) and also their limits (Segre thrust). The Vallfogona thrust branched eastwards with the Segre thrust (South Central unit) carrying the previously emplaced and blocked Pedraforca thrust sheets on its hanging wall, after 47 Ma. The eastern margin of the South Central Unit (Segre thrust zone) was emergent to the synorogenic surface and exposed to erosion throughout its evolution. The western margin was blind and accretionary during Middle-Upper Eocene. These two contrasting geometries were controlled by the original disposition of the Keuper décollement level.
Cross-section J-3 shows the most complete geological record for calculating shortening and timing. The total amount of shortening is ~70 km for the cover thrust sheets. Shortening including all south-directed structures south of the North Pyrenean Fault is 88.5 km.
During the uppermost Cretaceous-Paleocene time (83-55 Ma), the rates of shortening were extremely low (<0.5 mm/a). From Early Ilerdian (55 Ma) to Middle Lutetian (47 Ma) the rates of shortening increased until 4.4 mm/a, mainly during the second half of this period. The lower rates of shortening (1.3-2.6 mm/a) characterised the period ranging from Middle Lutetian (47 Ma) to Early Miocene. The end of thrusting migrated from 34.4 Ma (J-1 section) in the east to 23 Ma (Riglos section) and younger to the west. The end of thrusting propagated at a rate of 11 mm/a in the eastern Pyrenees (34.4-29 Ma) and 21 mm/a in the central Pyrenees (29-23 Ma and younger).

Much of this guide was published originally for the 1976 Annual Meeting of the Geological Society of America:

Matthews, V.; Work, D.F.; LeMasurier, W.; Stearns, D.W., 1976, Mechanism of Laramide deformation along the northeastern flank of the Front Range (Road Log), in Epis, R.C. and Weimer, R.D., ed., Studies in Colorado Field Geology; Colo. Sch. of Mines Prof. Contr. No. 8, p. 386-397.

This version differs in several ways:
1. Color images
2. GPS locations for stops
3. Numerous updates over the four decades in which a wide assortment of groups and associations were taken on this trip by the senior author.  The final trip was led in the summer of 2016 for invited scientists from the USGS, CSM, and CSU.

Origami is a Japanese art of folding paper. Recently it has started to be used in
aerospace applications such as deployable masts, satellite antennas, and in architectural
applications such as emergency shelters, temporary shelters, portable exhibition stands.
Deployable plate structures based origami art are attractive to both architects and
engineers because of their structural and spatial qualities. They have special geometries
according to the rigid origami patterns. The Miura-Ori is a rigid origami pattern that is
formed from a tessellated arrangement of a single repeated unit consists of four
quadrangle plates. It has fully folded and fully deployed configurations.
This research investigates geometric and mobility aspects of Miura-Ori pattern
with its derivations and explore the possibilities of constructing a deployable plate
structure using the same pattern. The first part of the research investigates geometry of
the Miura patterns. The aim is to generate derivations by changing the input parameters.
Small scale physical models are built to verify the geometric design guidelines.
Miura unit consisted of four plates and four joints is a single degree of freedom
spherical mechanism. The second part of the research is concentrated on mobility
analysis. The aim is to develop a method for removing excessive plates and joints
without changing the mobility. The established equations assist us to determine nth term
of the excessive plates and joints. A Method of Double Arrangement (MoDA) is
developed in order to determine the placement of excessive plates.
Finally, a deployable plate structure based on Miura-Ori pattern is proposed for
an architectural application. However, the plates cause obstruction of the sky, thereby
affecting sunlight and daylight availability inside the building. Thus, some excessive
plates are reduced according to the proposed method. The final form of the structure lets
to get more energy from the sun to provide heating and lighting.
Keyword: rigid origami, Miura-Ori, spherical mechanisms, mobility.

In the deformation of layered materials such as geological strata, or stacks of paper, mechanical properties compete with the geometry of layering. Smooth, rounded corners lead to
voids between the layers, while close packing of the layers results in geometrically-induced curvature singularities. When voids are penalized by external pressure, the system is forced
to trade off these competing effects, leading to sometimes striking periodic patterns.

In this paper we construct a simple model of geometrically nonlinear multilayered structures under axial loading and pressure confinement, with non-interpenetration conditions
separating the layers. Energy minimisers are characterized as solutions of a set of fourthorder nonlinear differential equations with contact-force Lagrange multipliers, or equivalently
of a fourth-order free-boundary problem. We numerically investigate the solutions of this free boundary problem, and compare them with the periodic solutions observed experimentally.

Strike-slip shear zones of the Variscan orogen are used to derive the evolution of paleostrain and discuss the kinematics of the waning stages of the Gondwana-Laurussia collision during the amalgamation of Pangea. In the Iberian Massif, the recognition of three late Carboniferous deformation events related to strike-slip tectonics (D3, D4, D5) in the Trancoso-Pinhel region (Portugal) reveals that late orogenic transcurrent deformation was episodic and occurred in a short period of time (<15 m.y.). Early stages of strike-slip deformation included dextral and sinistral shear zones and orogen-parallel upright folds (D3; ca. 311 Ma). These structures followed the development of extensional shear zones (D2) during the tectonothermal reequilibration of the orogen. D3 structures were deflected and folded by the sinistral D4 Juzbado-Penalva do Castelo shear zone, dated as ca. 309–305 Ma by SHRIMP (sensitive high-resolution ion microprobe) U-Pb zircon dating of synkinematic granitoids. D3 and D4 structures were folded under east-west compression (D5) influenced by the strike-slip movement of the dextral Porto-Tomar shear zone. Variscan movement along the Porto-Tomar shear zone started ca. 304 Ma (onset of the Buçaco basin and syn-D5 granites), but ceased before ca. 295 Ma (age of the final closure of the Ibero-Armorican arc and crosscutting granites). The contrasting geometry, kinematics, and timing of these strike-slip shear zones are explained by deformation partitioning upon a rheologically inhomogeneous crust with structural and tectonothermal anisotropies generated during previous deformation. The convergence vector between Gondwana and Laurussia during D3–D5 remained the same, and was equivalent to the vector that explains the previous tectonic record (D2) in central and northwestern Iberia.

This thesis contains several distinct studies aimed at better understanding fracturing in compressional fault-cored folds. At outcrops of growth strata in the Oliana anticline in the Spanish Pyrenees, the relationship of two joint sets may reflect changing mechanical properties (i.e. via diagenesis) during the folding process. Using a Schmidt hammer, I assess the rigidity contrast between the individual units and suggest that late-stage, throughgoing joints formed in strata with conditions similar to those of the present day and that early, bed-contained joints formed when the rigidity contrast between beds was significantly greater than the present day contrast. Modeling algorithms that are used for fracture prediction assume plane strain to construct, model and restore fault-cored folds. Using mechanical models that allow heterogeneous transport in three dimensions, I explore the distribution and magnitude of out-of-plane transport in plunging fault-cored anticlines and provide guidelines of where plane strain should and should not be applied. I show that out-of-plane transport is significant in the simplest non-cylindrical folds, and suggest that complex non-cylindrical structures should not be modeled using plane strain. I mapped five bed-orthogonal fracture sets associated with folding and faulting events at Sant Corneli anticline, a non-cylindrical, fault related anticline in the Spanish Pyrenees. Fold axis perpendicular, calcite healed joint sets associated with similarly oriented normal faulting both pre-date, and are cross cut by calcite healed, N-NW striking joints. Later bed strike oblique joint sets are distinguished by the presence of iron oxide mineralization that probably occurred during Paleocene-Oligocene time. This study directly links fold-related fracturing to fold evolution because fracture sets can be dated relative to the structural evolution of the anticline. I use three-dimensional restorations of Sant Corneli anticline in the Spanish Pyrenees to test the fracture prediction capability of a fully three-dimensional finite element geomechanical restoration algorithm. Reconstruction of the three-dimensional architecture of the syn-tectonic strata provides a template for incrementally unfolding the anticline. Strains predicted by the restorations are compared to the fracture sets that formed over the corresponding time intervals, which are consistent with the observed fracture patterns at Sant Corneli anticline.

3D structural interpretation, well information and dynamic production data are combined to propose a different trapping geometry for the rich condensate gas in the Mirador Reservoir of the northernmost part of the Cupiagua Field.
The proposed model consists of two completely overlapping ramp anticlines separated by east verging partially sigmoidal thrust faults. The lowest thrust fault (Informally Named Base Fault) is the main thrust, and has a detachment along the Upper Guadalupe Mudstone. The upper thrust (Informally Named Core fault), which separates the two anticlines and creates the main trap in Recetor, has a detachment along the shaly Los Cuervos Formation. This duplex structure merges to the north allowing the communication between the two Mirador sections, explaining their dynamic behavior in terms of fluids and pressure through time.
The described ramp anticlines in the Recetor area were buried by the El Morro and the Nunchia folds, which were transported by the Yopal Fault System along the shaly Carbonera C6 unit.
This structural configuration was geometrically restored using dip cross sections, where a maximum shortening of 3.5 Km is interpreted, confirming the feasibility of the model and honoring the depth maps generated for each one of the reservoirs. The proposed structural configuration was also confirmed by the latest results observed during the 2007 drilling campaign.
Although genetically similar to the previous interpretation of this area, the proposed model considers an additional detachment zone along Los Cuervos Formation, creating new opportunities for exploration and production projects.

The objective of this work is to give new insights into the
geometry and kinematics of the tectonic wedge of the
Piedemonte License. The interpretation presented herein
involved and integrated the lately acquired surface and
subsurface data; 470 km2 of pre-stack depth migrated (PSDM)
3D seismic, geological information and production data from
11 wells and detailed surface geology. The main reservoirs,
Mirador, Barco and Guadalupe formations, are involved into
the hanging wall of the thrust sheets of the intercutaneous
wedge.
The structural analysis is based on “backward” modeling
(cross section restoration) and on forward modeling of the area
using the fault parallel flow algorithm. The Forward
Modelling comprises a model divided into 15 stages of
deformation; taking into account the deformation produced
since the Oligocene.
The main structural features are the Monterralo, El Morro,
Floreña, Dele, Pauto and Volcanera anticlines, and the
Nunchia syncline. The anticlines of the wedge could be
divided into two groups. One is characterized by greater
amplitude and been more symmetrical. The second one is
characterized by slightly more elongated back limbs and
shorter front limbs.
The structural analysis of the PTZ is based in the
modification of the Hubbert and Rubey`s (1959) model.
Previous experiments demonstrate that the relative strength
affects the development of active- or passive-roof duplexes.
Based on available surface and subsurface data, is
proposed that the structure of the License is an antiformal
stack duplex instead of the classic triangle zone.
Tectonic wedges remain undrilled along the Foothills of
the Eastern Cordillera. Those areas where is a syncline at
surface, may be a potential tectonic wedge. However, in the
southern part of the Llanos foothills some of the structures
may be pseudo – tectonic wedges.

The only occurrence of monoclines along the eastern flank of the Colorado Front Range is near Llvermore at the northern end of the tten echelonrl fold-and-fault belt (Fig. l). The monocl ines I ie along the Kawuneeche-Livermore Iineament (h/ork and tlatthev,rs, in preparatlon). sedimentary rocks elsewhere along the eastern flank of the Front Range were deformed into either homoclines, anticllnes, or syn-clines during the Laramide orogeny. Erosion has removed the sedlmentary rock cover from the Precambrian basement on the western edge of the area of monoclinal folding. Thus, the area pro-vldes an unusual opportunlty for studying the role of structural basement in the formation of the monocllnes. Our study comblned detalled field work with photo-interpretation of NASA U-2 photography stereo-pa I rs. DESCR I PT ION OF I1ONOCL lNES Northeast of Llvermore, Colorado the Paleozoic and l.lesozoic strata are folded into a series of narrov't linear monoclines (Flgs. 2r3)" The monoctines separate large areas where the strata are planar and lilanuscript received, February 18, 1976; accepted, llarch 3, 1976. fhe Mowttain Geologiet u. 73, no. 2 (Aprti lszol p. 61-66 6]. ABSTMCT: Honoclinal foldlng is the dominant style of deformation in Paleozoic and }lesozolc sedimentary strata northeast of Livermore, Colorado. The markedly llnear monocllnes are narrow and bound large areas of nearly flat-lylng strata. Axes of the monoclines are not parallel, which indlcates that they did not form as a resutt of reglonal horizontal compression. Several mlles to the west, eroslon has stripped the sedimentary cover from the underlylng Precambrian basement. The basement is characterized by brittle deformation in the form of dlfferentlally upllfted fault blocks. The pre-Pennsylvanian erosion surface developed on top of the Precambrlan igneous and metamorphlc rocks Is only sllghtly tilted. Where the faults ln the basement pass under the Paleozoic sedimentary cover to the east, the sedlmentary rocks are folded into unfaulted monoclines. This suggests that the monocllnes in the area are formed by passive draping of sedimentary rocks over dlfferentially uplifted basement blocks. Such an interpretation ls conslstent with the geometrlcal relationships of the monocllnes, with burlal conditlons durlng the Laramlde orogeny, and with experimental results on the behavior of rock materlals.

The Meso- to Neo-proterozoic Delhi Fold Belt (DFB) forms the backbone of Aravalli mountain range  which flanks the western edge of Indian shield. The DFB is delimited in the east by the Banded Gneissic Complex (BGC), Aravalli Fold Belt near Gogunda and the Vindhyan Supergroup, in the west by the pockets of BGC, Erinpura Granite (towards the South-West) and vast expanse of Phanerozoic and Alluvium elements along the Phulad Shear Zone which is also referred as Western Margin Fault in some other literature.
As far as the structural interpretation of the DFB is concerned, co-axial deformation and type 3 interference pattern are the two dominant phases described by Roday (1979), Naha (1984) and others. They described two types of major folding pattern: first isoclinal, recumbent folds and after that upright, open folds. According to them there is a large synclinorium in DFB but they mostly worked on the North Delhi Fold Belt (NDFB). Based on the fold vergence a flower structure is indicated instead of a synclinorium in the South Delhi Fold Belt (SDFB) by Sugden, (1987, p 138), where the faults splay upwards. Although a lot of work is done on the NDFB but little work is done in the SDFB which is also very unclear to understand the tectono-  stratigraphy of the mobile belt. So, the present study covers the study of the two part of the eastern boundary of the Ranakpur Shear Zone (RSZ). The Parashuramji is situated in the east just adjacent to RSZ. Kumbhalgarh is in the northeast of Parashuramji.
In the present study, it covers almost 215 sq. Km area along two transects between Kelwara to Sadri (East to West) and from Parashuramji Mahadev cave to Sayra (North to South) respectively. The rocks of the area are almost NNE-SSE trending The major difference between and the foliation planes dip towards west in Kumbhalgarh area whereas the foliations of Parashuramji dip towards east direction. Stereonet plotting shows that the fold axis of the major fold plunges around 100 southerly. Z- and S- shaped folds are also found within the foliation planes in several places as well as M-shaped folds in outcrop scale. So, a large synclinorium structure can thus be assumed. Within the foliation, boudins are found which are also folded . It thus supports polyphase deformation events in this region which occurs as follows: An initial extensional event where boudins are formed, followed by an compression when the boudins are folded. The isoclinal, upright folds plunge around 300 towards south, so E-W compressional events of several phases may be considered for the development of tight isoclinal folds of SDFB. Hook shaped fold  (type 3 of Ramsay and Huber) are also observed in Kumbhalgarh fort area.
The effects of the shear zone are present in Parashuramji, the central part of the area. some meso-scopic structures like rotation of foliation and  asymmetry of intrafolial fold are found in the area. Sheath folds are also found in the southern part of Parashuramji. The orientation of the axial planes of the folds are NNE-SSW/600 towards East. Teardrop shape folds are also found here.

      The rocks of the DFB are mostly of a metasedimentary origin and comprise gneisses and schists with very minor occurrences of quartzite, granite, pegmatite, diorite and amphibolite which indicate a metamorphic terrain multiply intruded by the igneous bodies of varying origin. Several microstructures are identified in the thin section of the rocks. Presence of σ-structure and C-S structure indicate the evidence of shearing. Low  (300-4000C) to medium (400-5000C) temperature metamorphism is interpreted from the microstructural study of the rocks. Bulging (BLG) recrystallisation is the one of the evidence of low temperature grain boundary migration. Undulose extinction and deformation lamellae are the other evidences of low grade metamorphism of the rocks.

Recrystallised quartz in a fabric with alternating quartz and feldspar layers is evident of medium temperature metamorphism. Here grain size of quartz depends upon the width of the quartz layer. Perthite with flame shaped albite lamellae (Ab) and tapered deformation twining of feldspar (type II) as well as greenschist (albite + epidote + quartz) to amphibolite facies (hornblende + plagioclase + garnet) mineral assemblage support the medium grade metamorphism of the rocks.

Curved thrust systems are commonly associated to linked frontal, oblique and lateral thrust ramps, which are oriented normal, oblique and parallel, respectively, to the regional compressive tectonic transport direction. Abrupt lateral variations of the thrust architecture usually occur in thrust belts across lateral/oblique ramps and their identification is crucial since they may mark the transition from different structural styles, kinematics of the thrust sheets and stratigraphic domains. Arcuate thrusts systems composed by linkage of frontal, oblique and lateral thrust ramps characterizing curved thrust belts likely indicate that the thrust system architecture has been strongly influenced by the sub-thrust inherited extensional fault pattern. Indeed, in fold-and-thrust belts that suffered an extensional fault heritage the localisation of lateral/oblique thrust ramps is strictly controlled by deep-rooted pre-orogenic normal faults that are transpressively reactivated when favourably oriented. The identification of inversion structures in thrust belts has a direct impact on both the unravelling of the structural style and the hydrocarbon prospectivity of a region, because the inversion processes control the petroleum system elements from the initial extension up through the later compressional deformation. The study of tectonic inversion-related folds in regions where the mechanical stratigraphy is well known is valuable for the development of geometric and kinematic models that may add useful information for unravelling the structural style of thrust belts.
In this contribution, we document the geometrical characteristics of inversion structures (i.e., push-up inversion structures and fault-bend reactivation anticlines) occurring along oblique thrust ramps, by examining some examples of buried Apulian structures in the Central-Southern Apennines (i.e., Setteporte and Mt. Taburno push-ups) and outcropping thrust-related folds in the Central-Northern Apennines of Italy (i.e., Sabini Mts. push-up and OAS hanging-wall fault-bend macro-anticlines). The different geometrical features between push-up inversion structures and fault-bend reactivation anticlines are functionally controlled by: (i) the mechanical characteristics of the involved sedimentary multilayer, (ii) the original architecture of the former extensional basin, and (iii) the amount of thrust displacement. The recognition of such inversion structures is important in understanding the anatomy and structural style of foreland fold-and-thrust belts; in addition, this recognition is critical in interpreting the geometry and types of structural traps that may be expected along oblique thrust ramps. This study reveals that push-up inversion structures and fault-bend reactivation anticlines could coexist along oblique thrust ramps within a unique curved thrust system and may be detected among analogous foreland thrust belts that experienced structural inheritance of extensional basins.

A regional study starting from detailed geological mapping has been carried out in the Malpica-Tui Complex of Galicia in NW Spain. The complex is formed by two units representing pieces of the external edge of Gondwana, subducted and exhumed during the Variscan collision. The study shows that synsubduction and early synexhumation structures in continental subduction channels tends to be obscured and even erased once exhumation is complete. Detailed structural analysis, matched with the knowledge of the history, and available data for other Galician basal units have elucidated the major structures developed during the subduction-exhumation process. The results include evidence of the plate convergence causing early Variscan continental subduction of the Gondwana margin. Subduction was followed by exhumation driven by ductile thrusting within the subduction channel, which, in turn, provoked crustal duplication in the subducted slab and modified the initial tectonometamorphic architecture of the subduction wedge. The next step was accretion to the adjacent continental domains, placing the subduction wedge on top of unsubducted parts of the Gondwana margin via ductile thrusting. Thrusting was preceded by progressive propagation of a train of recumbent folds toward the foreland that affected the previous structural stack. Subsequent transference of oceanic (Rheic) and peri-Gondwanan terranes to the Gondwana margin took place by out-of-sequence thrusting followed by crustal extensional collapse and strike-slip tectonics.

The rocks of this area is generally NNE-SSW trending but the major difference between the nearby two area is the dip direction of foliation planes. In the eastern part, near Kumbhalgarh fort, foliation planes dip towards west whereas foliations of Parashuramji cave area dip towards east. In detail study of the both part it is noticed in many places that there are Z- and S- shaped folds present in the eastern part and western part respectively. The plunge of the fold axes are nearly 18 towards 180.So, in the large scale it can be assumed that there is a large synclinorium. M-shaped folds are present within an almost 50m outcrop. The folds also plunges 15 degree towards 190 degree. Shear zones signatures like asymmetric folds, rotation of boudins and sheath folds are observed. Three phases of deformation are interpreted clearly in the mapped area. First, an early extension was followed by compression and formation of isoclinal, tight folding are observed. Therefore the boudins are folded. Hook shaped folds (Type 3) are also seen. The fantastic structures of the region show that there is a shear zone running parallel to the axis of the
synclinoriun. Some workers have suggested that the area is a major transpressional zone with development of a flower structure. The structure of North Delhi Fold belt is well known but relatively lesser data is available from Southern part of Delhi Fold belt. This study has a potential to extract more focused structural information from the SDFB and improve the understanding ofthe Delhi-Aravalli orogeny.

The Argentinean and Bolivian sub-Andean fold-and-thrust belt is located in the orogenic front between 18-23°S and 64-63°W and immediately to the east of the Puna-Altiplano system and Eastern Cordillera. This fold-and-thrust belt is characterized by thinskinned structures detached in Lower Paleozoic sequences. The compressional stage that affected this part of the orogen began in late Miocene and is ongoing. Examining the morphology of the folds and thrusts by combining digital elevation models, geological maps, and field observations allows us to present tectonic and geomorphological data on lateral fold growth and spatially linked shortening along the San Antonio range. The crest of this fold chain shows multiple culminations , slightly right-stepping, that merge to form the full San Antonio structural trend. Forked drainage patterns and the presence of wind gaps suggest recent fold amplification and lateral growth from these culminations. Linear and stepped linkage geometries are found between single structures. A northward increase in surface elevation and fluvial erosion follows the south to north increase in fold amplitude, aspect ratio, and change in structural style from folding to thrusting. The observed along-strike alternation of topographic highs and lows correlates well with the locations of subsurface hydrocarbon traps and saddle spill points indicating that the shallow and deep deformation patterns are coupled as a single structural feature.

The structure of the Ciudad Rodrigo area (Iberian Massif, Central Iberian Zone) has been revisited in order to integrate new geological data with recent models of the evolution of the Iberian Massif. Detailed mapping of fold structures along with a compilation of field data have been used to constrain the geometry and relative timing of ductile deformation events in this section of the hinterland of the Variscan belt. The structural evolution shows, in the first place, the development of a regional train of overturned folds with associated axial planar foliation (D 1 ). Towards the lower structural levels, the deflection of the fold limbs and a subhorizontal crenulation cleavage depict the upper structural boundary of a superimposed low angle shear zone (D 2 ), which extends at least to the deepest parts of the basement exposed in the study area. The amplification and rotation of D 1 folds about a horizontal axis also occurred within this shear zone. The flat-lying character of the D 2 structures accounts for the attenuation of the previously thickened crust, which developed following gravity gradients during thermal re-equilibration. Subsequent deformation led to the formation of two orthogonal sets of upright folds (D 3 ), representing a new shift between crustal thinning and crustal thickening in the region.

Mining, process of extracting useful minerals from the surface of the Earth, including the seas. A mineral, with a few exceptions, is an inorganic substance occurring in nature that has a definite chemical composition and distinctive physical properties or molecular structure. (One organic substance, coal, is often discussed as a mineral as well.) Ore is a metalliferous mineral, or an aggregate of metalliferous minerals and gangue (associated rock of no economic value), that can be mined at a profit. Mineral deposit designates a natural occurrence of a useful mineral, while ore deposit denotes a mineral deposit of sufficient extent and concentration to invite exploitation.

Archaeological discoveries indicate that mining was conducted in prehistoric times. Apparently, the first mineral used was flint, which, because of its conchoidal fracturing pattern, could be broken into sharp-edged pieces that were useful as scrapers, knives, and arrowheads. During the Neolithic Period, or New Stone Age (about 8000–2000 BCE), shafts up to 100 metres (330 feet) deep were sunk in soft chalk deposits in France and Britain in order to extract the flint pebbles found there. Other minerals, such as red ochre and the copper mineral malachite, were used as pigments. The oldest known underground mine in the world was sunk more than 40,000 years ago at Bomvu Ridge in the Ngwenya mountains, Swaziland, to mine ochre used in burial ceremonies and as body colouring.

Gold was one of the first metals utilized, being mined from streambeds of sand and gravel where it occurred as a pure metal because of its chemical stability. Although chemically less stable, copper occurs in native form and was probably the second metal discovered and used. Silver was also found in a pure state and at one time was valued more highly than gold.

According to historians, the Egyptians were mining copper on the Sinai Peninsula as long ago as 3000 BCE, although some bronze (copper alloyed with tin) is dated as early as 3700 BCE. Iron is dated as early as 2800 BCE; Egyptian records of iron ore smelting date from 1300 BCE. Found in the ancient ruins of Troy, lead was produced as early as 2500 BCE.

One of the earliest evidences of building with quarried stone was the construction (2600 BCE) of the great pyramids in Egypt, the largest of which (Khufu) is 236 metres (775 feet) along the base sides and contains approximately 2.3 million blocks of two types of limestone and red granite. The limestone is believed to have been quarried from across the Nile. Blocks weighing as much as 15,000 kg (33,000 pounds) were transported long distances and elevated into place, and they show precise cutting that resulted in fine-fitting masonry.

Previous studies of jointing in sedimentary rocks have shown that joint-network architecture is controlled by mechanical stratigraphy, which is described by (1) the thickness and rigidity of stratigraphic units and (2) the nature of interfaces between beds. Using joint pattern to infer rigidity contrast between beds is complicated by the possibility that material properties of the beds may change between fracturing events. Observation of both an early bed-contained joint set and a differently oriented late throughgoing joint set in the same beds of growth strata in the Oliana anticline in the Spanish Pyrenees may reflect changing mechanical properties (i.e., via diagenesis) during the folding process. Using a Schmidt hammer, we assess the rigidity contrast between the individual units and show that the present-day contrast is not great enough to terminate joints at interfaces. This result is consistent with an interpretation that the late-stage throughgoing joints formed in strata with conditions similar to those of the present day and that the early bed-contained joints formed when the rigidity contrast between beds was significantly greater than that of the present day. For example, differential diagenesis rates between layers of differing grain size would produce temporally changing mechanical stratigraphy. We propose that changes in mechanical stratigraphy may have previously been unrecognized in other stratigraphic sections and that these changes affect joint-network architecture and subsequent fluid-flow pathways.

The structure of the Ciudad Rodrigo area (Iberian Massif, Central Iberian Zone) has been revisited in order to integrate new geological data with recent models of the evolution of the Iberian Massif. Detailed mapping of fold structures along with a compilation of field data have been used to constrain the geometry and relative timing of ductile deformation events in this section of the hinterland of the Variscan belt. The structural evolution shows, in the first place, the development of a regional train of overturned folds with associated axial planar foliation (D1). Towards the lower structural levels, the deflection of the fold limbs and a subhorizontal crenulation cleavage depict the upper structural boundary of a superimposed low angle shear zone (D2), which extends at least to the deepest parts of the basement exposed in the study area. The amplification and rotation of D1 folds about a horizontal axis also occurred within this shear zone. The flat-lying character of the D2 structures accounts for the attenuation of the previously thickened crust, which developed following gravity gradients during thermal re-equilibration. Subsequent deformation led to the formation of two orthogonal sets of upright folds (D3), representing a new shift between crustal thinning and crustal thickening in the region.

This integrated study of deep earthquake locations and focal mechanisms investigates the relationship between the shape of subducting slabs and seismic behaviour in Wadati-Benioff zones. High quality earthquake locations are used to map the shapes of subducting slabs which have reached the upper-lower mantle boundary. The resulting slab models reveal the presence of large slab folds in the mantle transition zone. The distributions and focal mechanisms of deep earthquakes are analysed to determine whether these folds have a role in governing Wadati-Benioff zone seismicity.

Bands or lineations of dense seismicity are associated with the hinge zones of identified folds. The focal mechanisms of earthquakes within these bands reveal that the mapped fold hinges are commonly perpendicular to the directions of maximum coseismic extension and compression. The hinges plunge at a variety of angles, resulting in systematic deviations from the downdip stress field expected within planar slabs. Slab synforms are typified by earthquake focal mechanisms indicating in-plane compression (e.g. Izu-Bonin, Tonga), while antiforms have earthquake focal mechanisms indicating in-plane extension (e.g. Solomons) or a mixture of in-plane compression and extension (e.g. Tonga).

Slab buckling explains both the clustering of earthquakes and the observed focal mechanism orientations within fold hinges. The localization of strain within buckle zones results in several of the peaks observed in regional earthquake depth distributions. During buckling, the directions of maximum shortening and extension are expected to be perpendicular to the fold hinges, in agreement with deep earthquake moment tensors. Displacement of the minimum-strain surface away from the centre of each seismogenic zone can explain the predominance of in-plane compression within synforms and in-plane extension within antiforms. More complex local variation in focal mechanism orientations in the Tonga slab can be explained by a superposition of in-plane compression and bending strain.

Buckling appears to be a common mechanism facilitating convergence between subducting slabs and the lower mantle. The consequent rotation and translation of fold limbs may explain the discrepancy between estimates of convergence based on subduction velocities and long-term coseismic strain.

Impact crater development on every planetary body requires catastrophic movement of large volumes of crustal rocks. The process produces well-known features such as brecciation and frictional melting, but a mechanism that explains how rocks accommodate the strain during the cratering flow remains unclear. Here, we investigate target rocks from the Araguainha impact crater (central Brazil) that typify what happens to a consolidated, fluid-saturated sedimentary rock at ∼2 km below the surface prior to the impact event. Sandstone units record a pattern of chaotic large-scale folds and pervasive microscopic (grain-to-grain) brecciation that result from rock strength degradation triggered by the impact. Field mapping and extensive textural observations indicate that these sandstones experienced initial microstructural damage from the shock wave and that this process may have weakened grainto-grain bonds and started the process of pervasive microbrecciation. Accompanying heating and decompression lead to vaporization and expansion of fluids in the sandstone pores, magnifying the process of brecciation by effectively liquefying the rock mass and allowing for chaotic folding (at a range of scales up to blocks 100 m in length) in the central uplift. This is a vaporization-assisted microbrecciation, and it may have inhibited the formation of pseudotachylites, because energy was dissipated by pervasive microcracking, vaporization of pore fluids, and large scale chaotic folding, rather than localized displacement on brittle faults and frictional heating. We suggest that impact liquefaction of sedimentary rocks depends on whether the presence of pore-fluids and related micro-brecciation are sufficient to dissipate most of the impact energy. (C. Lana). violent acoustic vibrations could temporarily reduce the internal frictional strength of the rocks, allowing them to behave like fluids . This model is convenient because liquefied debris has an effective viscosity sufficiently low to permit collapse within the required time-scale. Other physical models propose that rocks lose internal cohesion through thermal softening due to extreme temperatures released upon impact , but direct evidence for these theoretical models have not been fully documented in nature. While there are many studies of the characteristic effects of shock deformation on target rocks, the phenomenon that causes loss of cohesion in target rocks around large impact structures has not been fully documented. Here we show that the structural integrity of fluidsaturated sedimentary rocks is destroyed at grain scale by shock damage and pore-fluid expansion during the impact.

Many algorithms assume plane strain to construct, model and restore fault-cored folds. Using mechanical models that allow heterogeneous transport in three dimensions, we explore the distribution and magnitude of out-of-plane transport in plunging fault-cored anticlines and provide guidelines of where plane strain should and should not be applied. We developed a new technique of incrementing infinitesimal elastic strains to produce folds with aspect ratios similar to natural folds. Map views of displacement vectors show that in general, out-of-plane displacement is localized near the lateral fold tips. Cross-sections show that out-of-plane transport is depth dependent with out-of-plane displacement increasing toward the surface. Flexural slip surfaces compartmentalize out-of-plane transport within distinct mechanical units, with the maximum outof-plane displacement near the tops of mechanical units. Two-dimensional models with additional frictionally slipping bed contacts suggest that freely slipping contacts can approximate the deformation of many frictionally slipping contacts. We show that out-of-plane transport is significant in the simplest non-cylindrical folds, and suggest that complex non-cylindrical structures should not be modeled using plane strain exclusively. We also show that flexural slip surfaces exert a significant control on the magnitude and structural position of out-of-plane transport in our models.

The Mont Fort nappe, former uppermost subunit of the Grand St-Bernard nappe system, is an independent tectonic unit with specific structural and stratigraphic characteristics (Middle Penninic, NW Italy and SW Switzerland). It consists in a Paleozoic basement, overlain by a thin, discontinuous cover of Triassic-Jurassic metasediments, mainly breccias, called the Evolène Series. The contact of this Series over the Mont Fort basement is debated: stratigraphic or tectonic? We present new observations that support the stratigraphic interpretation and consequently imply that the Evolène Series belongs to the Mont Fort nappe. We moreover show that the Mont Fort nappe was strongly affected by normal faulting during Jurassic. These faults went long unnoticed because Alpine orogenic deformation blurred the record. Alpine strain erased their original obliquity, causing confusion with an Alpine low-angle thrust. These Jurassic faults have been passively deformed during Alpine tectonics, without inversion or any other kind of reactivation. They behaved like passive markers of the Alpine strain. Detailed field observations reveal the link between observed faults and specific breccia accumulations. Areas where the Evolène Series is missing correspond to sectors where the fault scarps were exposed on the bottom of the sea but were too steep to keep the syn- to post-faulting sediments. The Mont Fort nappe thus represents an example of a distal rifted margin. The succession of synsedimentary extensional movements followed by orogenic shortening generated a situation where passively deformed normal faults mimic an orogenic thrust.

A simplied variational model for the formation of convoluted accommodation structures, as seen in the hinge zones of larger-scale geological folds, is presented. The model encapsulates
some important and intriguing nonlinear features, notably: infinite critical loads, formation of plastic hinges, and buckling on different length scales. An inextensible elastic beam is forced by
uniform overburden pressure and axial load into a V-shaped geometry dictated by formation of a plastic hinge. Using variational methods developed in [1], energy minimization leads to representation as a fourth-order nonlinear dierential equation with free boundary conditions. Equilibrium solutions are found using numerical shooting techniques. Under the Maxwell
stability criterion, it is recognized that global energy minimizers can exist with convoluted physical shapes. For such solutions, parallels can be drawn with some of the accommodation
structures seen in exposed escarpments of real geological folds.

We applied the detailed structural analysis to 394 outcrops in the southern and northern metamorphic cover of the Karkonosze Intrusion. We recognised five generations of fold structures: F 1 – poorly preserved tight intrafoliation folds; F 2 – the most common generation, with the whole variety of fold geometries, W–E and WSW–ENE-oriented fold axes in the northern contact zone, and W–E and WNW–ESE-oriented fold axes in the southern contact zone; F 3 – chevron folds; F 4 – kink folds observed only in the Stara Kamienica schist belt; and F 5 – wide open folds, locally transformed into monoclinal kink folds, probably formed during the Variscan intrusion of the Karkonosze pluton. Similarity observed in the structural style in the northern and southern contact zones prove that these lithostratigraphic units had formed a single unit – the Izera-Kowary Unit – and had undergone the same deformational stages before the Karkonosze granitoid intrusion took place.

The identification of inversion structures in thrust belts has a direct impact on both the unravelling of the structural style and the hydrocarbon prospectivity of a region, because the inversion processes control the petroleum system elements from the initial extensional phase up through the later compressional deformation. The study of tectonic inversion-related folds in regions where the mechanical stratigraphy is well known is valuable for the development of geometric and kinematic models, which may provide additional useful information for unravelling the structural style of foreland fold-and-thrust belts and that are instrumental in guiding the interpretation of subsurface seismic data for detecting structural hydrocarbon traps.
In this study we reconstructed the geometric characteristic of positive inversion structures occurring along oblique inversion-related thrust ramps of curved foreland thrust systems. By combining surface geological and structural data with the interpretation of onshore seismic reflection profiles, we sought to identify Pliocene-Quaternary positive inversion structures that developed in both the hanging-wall and the footwall of oblique thrust ramps within the Apennines carbonate-dominated foreland fold-and-thrust belt. These oblique thrust ramps belong to: the buried Apulian chain in the Central-Southern Apennines, and to the Central-Northern Apennines fold-thrust belt. Balanced cross-section construction, seismic interpretation, time-to-depth conversion, and section restoration were performed, and the selected examples were analysed to identify the various geometric characteristics of positive inversion structures with respect to the mechanics of the involved multilayer, the configuration of the pre-existing extensional basin, and the extent of thrust displacement. Plio-Quaternary positive inversion tectonics occurred in the Apennines foreland fold-and-thrust belt by reactivating in transpression N-S-trending pre-thrusting normal faults and giving rise to regional-scale oblique thrust ramps (e.g. Olevano-Antrodoco-Sibillini and Sangro-Volturno oblique ramps). Inversion structures characterizing both hanging-wall and footwall blocks of such oblique thrust ramps display different geometrical features of the thrust-fold profile and they may appear as push-up inversion structures (e.g. Setteporte, Mt. Taburno and Sabini Mts. structures) or as fault-bend reactivation anticlines (e.g. OAS hanging-wall macro-anticlines). Their geometrical characteristics are functionally controlled by: (i) the mechanical characteristics of the involved carbonate sedimentary multilayer, (ii) the original architecture of the former extensional basin, and (iii) the amount of thrust displacement.
This study reveals that these peculiar inversion structures (i.e., push-up inversion structures and fault-bend reactivation anticlines) could coexist and may occur along oblique thrust ramps within the same thrust system of a curved foreland thrust belt. The recognition of such inversion structures is important in understanding the anatomy and the structural style (e.g., thin-skinned detachment-dominated style vs. thick-skinned basement-involved inversion tectonics) of curved thrust systems characterizing foreland fold-and-thrust belts; in addition, this recognition is critical in interpreting the geometry and types of structural traps that may be expected along oblique thrust ramps (e.g., vertically-stacked traps vs. inversion-related structures).

The three-dimensional crustal architecture of the eastern part of the Mount Isa Inlier is investigated from serial cross-sections constructed using geological map data, revised chronostratigraphy, gravity, magnetics, worms (multiscale wavelet edges of potential field data) and seismic data. The top part of the crust consists of rift and platform type metasediments that were deposited in three cover sequences from 1850 to 1610 Ma. These rocks constitute the Mount Isa Eastern Succession, and they were intruded by mafic-felsic plutons, dykes and sills of various ages before and during the Isan Orogeny (ca. 1.6-1.5 Ga). The Eastern Succession overlies a felsic metamorphic basement, which in turn sits on a tonalitic-gabbroic lower crust. The depositional basin architecture for the Eastern Succession was controlled by major N-S trending structures that penetrated the lower crust, and accommodated E-W extension. These structures also underlie major upper crustal structures such as the Mitakoodi Culmination and Snake Creek Anticline that were formed by contraction in the Isan Orogeny. Positive inversion may therefore have been a key process in the evolution of the eastern part of the inlier, and governs its architecture at the crustal scale. Inversion involved reactivation of basement-penetrating structures, which localised contractional structures in the cover sequences above, as well as influencing pluton emplacement. The felsic metamorphic basement may have been penetratively deformed during inversion. The spatial association between the basin-controlling and contractional structures suggests that either early extensional displacements were completely reversed by later contraction, or that much of the Eastern Succession has remained essentially parauthochthonous relative to the basement.