Structural Geology

Weakly cemented sands from southern France exposing deformation bands were studied as a sandstone reservoir analogue. The objective was to analyse the observed localised deformation in the presence of imperfections (diagenetic or from deformation processes). 2D nano-(Scanning Electron Microscopy) and 3D micro-(X-ray Computed Tomography) image analysis techniques were employed to inspect samples of deformation bands from the outcrops and laboratory-deformed samples of undisturbed sand. Artificially cemented samples without imperfections, prepared with a novel procedure, were also tested for comparison. Syntaxial quartz overgrowths were identified not only in compactional shear bands but also in undisturbed sand and in a dilation band. Kaolin clay was present at the time of localised deformation, since it interacted with free silica to form micro-quartz, but more clay infiltrated afterwards forming menisci bonds. Kaolinite illitization, observed in multi-strand bands and cluster, and silica cementation required temperatures > 70°C to occur. Therefore, it is supported the hypothesis that the Bédoin sand reached a burial depth of 2 -3 km. The mechanical tests showed that all the samples developed localised deformation before or at the peak stress; however, peak stress was reached later in artificially prepared samples than in the natural ones. The weakly cemented sands exhibited a behaviour close to that of sands. Weaker imperfections were observed, by performing Digital Volume Correlation, to trigger localised deformation, whereas stronger imperfections shifted the bands far from them. Artificially cemented sand samples, with higher cement content than the natural ones, seemed to develop less stress concentration at grain contact, thus generating networks of shear bands, rather than fewer bands as observed in the natural samples. Porosity and permeability analyses were performed through image processing on the samples 3D X-ray tomographies. Porosity values enabled the distinction of zones in each band type; in particular, a dilation band core reported a porosity value (30%) similar to that of the undisturbed sand. Permeability was zero in the strands of compactional shear bands, whereas the dilation band core had values closer to that of the undisturbed sand (10 +4 mD).

Previous studies on fracture networks have shown that fractures contained within distinct mechanical units ("stratabound") are regularly spaced while those that terminate within the rock mass are clustered ("non-stratabound"). Lacunarity is a parameter which can quantify the distribution of spaces between rock fractures. When normalized to account for differences in fracture abundance, lacunarity characterizes the distribution of spaces as the degree of clustering in the fracture network. Normalized lacunarity curves, L * (r), computed using the gliding-box algorithm and plotted as a function of box-size, r, were constructed for natural fracture patterns from Telpyn Point, Wales and the Hornelen basin, Norway. The results from analysis of the Telpyn Point fractures indicate that such curves are sensitive to differences in the clustering of different fracture sets at the same scale. For fracture networks mapped at different scales from the Hornelen basin, our analysis shows that clustering increases with decreasing spatial scale. This trend is attributed to the transition from a "stratabound" system at the scale of sedimentary cycles (100e200 m) that act as distinct mechanical units to a "non-stratabound" fracture system geometry at the finer 10's of meters thick bedding scale.

Outcrop data are presented from the Asquempont-Virginal area, type locality of the Asquempont fault. These are used to redefine the Asquempont fault, to stress the importance of normal faulting in the Palaeozoic deformation history of the Brabant Massif and to suggest large-scale slumping during the middle Caradoc. The Asquempont fault is redefined as a pre-cleavage and pre-folding low-angle extensional detachment that, in the study area, forms the contact between the Lower to lower Middle Cambrian Oisquercq Formation and the Ordovician and was active between the middle Caradoc and the timing of cleavage development. The fault originally described by Legrand (1967) as the Asquempont fault, supposedly a steeply NE-dipping reverse fault with a sinistral component, is in fact a steeply dipping to sub-vertical post-cleavage normal fault that in the classical outcrop of the Asquempont fault truncates the redefined Asquempont fault, and hence only locally forms the limit between the Cambr...

This paper illustrates a case history, based on full-scale tests (trial embankment). More specifically, the settlements of a full-scale trial embankment on a very compressib?e soil (organic clay) for a period of 5 years are reported. The observed settlements are compared with those obtained from an A type prediction, as well as a B type prediction. The analysis results suggest the importance of an appropriate modelling of secondary settlements of organic soils. The difficulties in obtaining good quality undisturbed samples of organic clay and the peculiar creep behaviour point out the importance of full-scale tests.

The Alborz is a narrow (100 km) and elevated (3000 m) mountain belt which accommodates the differential motion between the Sanandaj -Sirjan zone in central Iran and the South Caspian basin. GPS measurements of 12 geodetic sites in Central Alborz between 2000 and 2002 allow to constrain the motion of the belt with respect to western Eurasia. One site velocity on the Caspian shoreline suggests that the South Caspian basin moves northwest at a rate of 6 F 2 mm/year with respect to western Eurasia. North -South shortening across the Alborz occurs at 5 F 2 mm/year. To the South, deformation seems to extend beyond the piedmont area, probably due to active thrusting on the Pishva fault. We also observe a left-lateral shear of the overall belt at a rate of 4 F 2 mm/year, consistent with the geological motion observed along E -W active strike-slip faults inside the belt (e.g., the Mosha fault).

The structure of the south Taiwan fold-and-thrust belt (FTB) comprises a roughly N-S striking, west-verging imbricate thrust system that has been developing since the Late Miocene. Here, we present the results of new surface geological mapping, serial balanced cross sections, long sections, and a map of the basal thrust that are combined with published borehole data and a 3D P-wave tomography model to constrain the structure at depth. The stratigraphy of the area comprises Eocene syn-rift sediments that are unconformably overlain by Oligocene through Middle Miocene shallow water post-rift sediments. These are unconformably overlain by Late Miocene through Holocene-age syn-orogenic sediments. We define the basement to these as the Mesozoic pre-rift rocks of the Eurasian margin, and assign it a P-wave velocity of > 5.2 km/s in the velocity model. The syn-orogenic sediments thicken and get progressively involved in the thrust sheets toward the south. The south Taiwan FTB can be divided into several thrust sheets. In the northern part of the map area, the structural grain is roughly N-S striking, changing southward to become NE-SW oriented. The westernmost thrust sheets form broad, open synclines cored by Pliocene to Holocene sediments, and tight hanging wall anticlines formed by Miocene rocks. Along its eastern flank, a narrow, complexly folded anticlinorium is developed in Miocene rocks. Restoration of the cross-sections indicates about 15 to 17 km of shortening. The basal thrust deepens from the surface towards the E and SE in a staircase trajectory, with narrow ramps and wide flats, reaching up to 8 km depth in the east before ramping down into the basement. The basal thrust has two pronounced, NE-striking oblique ramps that coincide with sigmoidal changes in shape of structures in the hanging wall. These correlate with a SW-NE trending increase in the P-wave velocity that is interpreted to image a basement high. We interpret this basement high to be an inherited extensional structure of the margin, and that faults associated with it are being reactivated, causing the changes in strike of the basal thrust, as well as in the surface trace of thrust and fold axes.

Bharathapuzha River is the second longest river in southwest India, where three physiographic regions show a distinctive spatial variation and their bed sediments can be considered environmental hosts for end-products generated by human activities and natural radionuclide components. Thus, the study of this river sediments in SW India is important not only because they are recorders of adverse human impacts (e.g., intense agricultural activities and urban pollution), but also because of their potential health hazards due to their common use as construction materials. Magnetic (e.g., magnetic susceptibility, anhysteretic remanent magnetisation and isothermal remanent magnetisation), radionuclide ( 226 Ra, 232 Th and 40 K) and chemical (trace and major elements) measurements were carried out in bed sediment samples along 33 sites from the uppermost catchment downstream. Magnetic measurements show the dominance of ferrimagnetic minerals; their concentration ranges widely along the river and between regions, showing up to 7-fold higher values for concentration-dependent magnetic parameters, e.g., mean values of saturation of isothermal remanent magnetisation acquisition are 67.9 and 9.4  10 3 Am 2 kg 1 for highland and lowland regions, M.A.E. Chaparro et al. ii Stud. Geophys. Geod., 59 (2015) respectively. Multivariate statistical analyses show the existence of relationships between magnetic, radioactivity and chemical variables. In particular, magnetic concentrationdependent parameters are significantly correlated with radioactivity variables 40 K and 226 Ra (with concentrations about 20% higher than the worldwide mean values), as well as with some elements: Fe, Ca and P. Such analyses also show differences between physiographic regions where samples from the highland (and lowland) region are well grouped showing higher (lower) magnetic concentrations and lower (higher) coercivity minerals. The spatial variation of magnetic parameters along the river can be related to the influence of both natural sources and human activities, i.e. urbanisation and intense agricultural activities. In this sense, environmental magnetism data provide very useful tools to investigate adverse human activities occurring in the riverine environment. K e y w o r d s : magnetic parameters, major and trace elements, multivariate statistical Stud. Geophys. Geod., 59 (2015)

Himalayan units using U-Pb detrital zircon dating reveal the existence of a Main Central Thrust (MCT) window and a prominent ductile thrust zone within the Greater Himalayan Crystallines in the Arunachal Himalaya of NE India. The newly discovered MCT window is cut and offset by several active north-trending normal faults extending from southeast Tibet, indicating the fault is no longer active. Ion-microprobe dating of monazite inclusions in garnets from the MCT zone indicates that the fault was active at 10.1 ± ± 1.4 Ma. Our structural data together with a synthesis of existing geologic maps suggest that the eastern Himalaya is composed of a large thrust duplex with the folded MCT as the roof fault. The total amount of crustal shortening accommodated by the duplex and the MCT south of the South Tibetan Detachment may exceed 500 km, which is probably greater than the amount of crustal shortening across the central Himalaya in Nepal and definitely greater than the amount of shortening across the western Himalaya in Pakistan. The observed systematic variation of crustal shortening suggests that Himalayan crustal thickening and uplift are uneven along strike, which may be in response to the westward decrease in convergence rate between India and Asia during the Cenozoic.

During the last years, several investigations on the earthquakes and related tectonic structures along the Java trench have been conducted. In this study, we focus on the Lombok Island -West Nusa Tenggara (Indonesia), which lies between the centres of the highest intensity of contiguous negative-positive geomagnetic anomalies in this region. The geological and tectonic structures, however, are not known in detail for this island, whereas a better knowledge of these conditions could lead to better estimate the potential earthquake risks and thus a possible improvement of the existing early warning system. We have performed a ground-based geomagnetic survey at 56 stations in the Lombok Island during October-November 2006 for a detailed mapping and interpretation of geomagnetic anomalies related to the geological and tectonic characteristics. The 2D and 3D magnetic maps show a general geomagnetic anomaly pattern in the Lombok Island which consists of repeated contiguous negative-positive anomalies. Two forward models have been proposed for a profile connecting a strongest apparent dipolar structure. The first model assumes a uniformly magnetized sphere as the source of the anomaly, and could be interpreted as a specific local structure composed by a quite large magnetic body. The second model considers several rocks with different susceptibilities and magnetizations, and could be interpreted as a discontinuity in the geological structures. This model agrees with the local geological surface conditions and the known large scale regional tectonic structure. Therefore, it is used to interpret our results in terms of tectonic characteristics, which suggests the potential existence of a new tectonic element (e.g. a local normal fault) in this region.

A decision support process is presented to accommodate selecting and scaling of earthquake motions as required for the time domain analysis of structures. Prequalified code-compatible suites of seismic motions are provided through a multi-criterion approach to satisfy prescribed reduced variability of selected Engineering Demand Parameters. Such a procedure, even though typically overlooked, is imperative to increase the reliability of the average response values, as required for the code-prescribed design verification of structures. Structure-related attributes such as the dynamic characteristics, as well as criteria related to the seismic motions variability and their compliance with a target spectrum are quantified through a newly introduced index, δsv-sc, tailored to prioritize motions suites for the response history analysis. An actual multi-story building is used to demonstrate the efficiency of the method, by being subjected to numerous suites of motions that were highly ranked according to both the proposed approach (δsv-sc) and the conventional index (δconv), already used by most existing code-based earthquake records selection and scaling procedures. The findings reveal the superiority of the herein proposed multi-criterion approach, particularly in terms of extensively reducing the intra-suite response variability of ground motions, while at the same time increasing the reliability of the design values. They also demonstrate that the new index greatly reduces the size of the suite of selected ground motions, for a given level of target reliability, with respect to the conventional methods.

Migmatite rocks are complex rocks largely due to the degree of partial melting and nature of parent rocks of this rock type. Partial melting or anatexis yield metatexite and diatexite components with variable mineralogical and chemical compositions. The nature of fractionation of elements during anatexis is not clearly understood. The migmatite quartzite gneiss complex of southwestern Nigeria exposed at Ogbomoso was studied in order to constrain the geochemical character of its metatexite and diatexite components. Field mapping revealed migmatite with stromatic, surreitic and dictyonitic structures represented the metatexite while parts of the migmatite with schollen structure and granitic component represent the diatexite. Several sections of representative samples were cut and examined for mineralogical compositions. Thin section analysis revealed occurrence of hornblende and garnet with plagioclase, microcline, biotite and muscovite implying greenschist to amphibolite facies for ...

To tackle the history of active thrust or reverse faults, it is often necessary to open the observation window on time scales on the order of 10^ 4-10 5 years by studying the morphologies associated to their activities. Because fluvial systems are particularly ...

The major tectonic structure of the Lower Silesia Region is connected with the Sudetic Marginal Fault (SMF), which past and contemporary activity has been pointed by many authors. Within the "GEOSUD" project the geodynamic profiles have been set up across the most active tectonic zones covering Sudetes and Fore-Sudetic Block. Repeated every year satellite GPS measurements were carried out on the sites of these profiles during the period 1996-2002. The analysis of the results of these measurements shows that tectonic activity of the SMF zone is still going on, but individual segments of this zone are marked by different character of horizontal movements.

Выполнены новые магнитотеллурические исследования в зоне Таласо-Ферганского разлома (ТФР). Работы проводились современной аппаратурой канадской фирмы "Феникс" с регистрацией периодов поля до 10000 с. Результаты интерпретации новых магнитотеллурических данных, полученных по Чаткальскому профилю в северо-западной части района исследования, свидетельствуют о существовании тенденции к ослаблению выявленной ранее аномалии электропроводности, приуроченной к зоне ТФР. Ключевые слова: магнитотеллурические зондирования, нормализация, двумерная инверсия, тензор импеданса, Таласо-Ферганский разлом. Рис. 1. Схема геоэлектрической изученности Киргизского Тянь-Шаня методом МТЗ.

Hydrocarbon exploration in the deepwater Western Gulf of Mexico, offshore Burgos Basin, Tamaulipas, Mexico, has been mainly focused in the NE-SW structural trend of the Perdido fold belt. Recent exploration efforts have targeted the adjacent Lamprea thrust and fold belt, located south of the Perdido trend. Deepwater channel and lobe systems constitute the Oligocene plays in the underexplored Lamprea trend. The objective of this research is to understand the tectonic evolution of the Lamprea thrust and fold belt, as recent oil and gas discoveries proved the presence of economic hydrocarbon accumulations. The Lamprea thrust and fold belt is located at the toe of a regional, gravity-driven linked system in the Western Gulf of Mexico. Middle Eocene to Late Oligocene strata were folded and thrusted during a Late Oligocene to Early Miocene compressional episode. A wide variety of thin-skinned NW-SE trending structures, such as imbricate systems, pop-up anticlines, and shear fault propagation folds characterizes the structural style. This compressional province detaches on an overpressurized Middle Eocene shale-system. Seismic velocity analysis suggests that variable degrees of overpressure affected the mechanical properties of the shale-based detachment, exerting a first order control on the development of different structural styles. Sequential restorations suggest that the Lamprea thrust and fold belt initiated as a series of N-S shale-cored folds. Subsequent shortening was accommodated by imbrication to the West of the shale-cored folds. Precursor folds evolved into breakthrough shear fault propagation folds in the East, and pop-up structures in the central area. The Lamprea thrust and fold belt followed an out-of-sequence propagation style, and most of the thrusts propagated along strike in a N-S direction. Shortening rates decreased from 4.75 mm/y in the South to 4.09 mm/y in the North. Restoration sensitivity analysis of seismic-derived interpretation error, and forward and inverse numerical modeling decreased uncertainty while providing viable restored cross-sections. ` v TABLE OF CONTENTS ABSTRACT .

Hydrocarbon exploration in the deepwater Western Gulf of Mexico, offshore Burgos Basin, Tamaulipas, Mexico, has been mainly focused in the NE-SW structural trend of the Perdido fold belt. Recent exploration efforts have targeted the adjacent Lamprea thrust and fold belt, located south of the Perdido trend. Deepwater channel and lobe systems constitute the Oligocene plays in the underexplored Lamprea trend. The objective of this research is to understand the tectonic evolution of the Lamprea thrust and fold belt, as recent oil and gas discoveries proved the presence of economic hydrocarbon accumulations. The Lamprea thrust and fold belt is located at the toe of a regional, gravity-driven linked system in the Western Gulf of Mexico. Middle Eocene to Late Oligocene strata were folded and thrusted during a Late Oligocene to Early Miocene compressional episode. A wide variety of thin-skinned NW-SE trending structures, such as imbricate systems, pop-up anticlines, and shear fault propagation folds characterizes the structural style. This compressional province detaches on an overpressurized Middle Eocene shale-system. Seismic velocity analysis suggests that variable degrees of overpressure affected the mechanical properties of the shale-based detachment, exerting a first order control on the development of different structural styles. Sequential restorations suggest that the Lamprea thrust and fold belt initiated as a series of N-S shale-cored folds. Subsequent shortening was accommodated by imbrication to the West of the shale-cored folds. Precursor folds evolved into breakthrough shear fault propagation folds in the East, and pop-up structures in the central area. The Lamprea thrust and fold belt followed an out-of-sequence propagation style, and most of the thrusts propagated along strike in a N-S direction. Shortening rates decreased from 4.75 mm/y in the South to 4.09 mm/y in the North. Restoration sensitivity analysis of seismic-derived interpretation error, and forward and inverse numerical modeling decreased uncertainty while providing viable restored cross-sections. ` v TABLE OF CONTENTS ABSTRACT .

The Caledonian thrust nappes and basal de ´collement zone above the Baltic shield record penetrative Caledonian deformation related to ESE-directed nappe transport, and subsequent WNW-directed ductile shearing during extensional collapse of the orogen. Muscovite within Proterozoic quartzite conglomerates in the Lower Bergsdalen Nappe that record only ESE-vergent Caledonian deformation display internally concordant 40 Ar/ 39 Ar age spectra which yield plateau ages of 403 Ma and 398 Ma. Similar plateau ages (402 and 399 Ma) were obtained from muscovite from mica schists which record additional penetrative WNW-directed shearing, suggesting that muscovite intracrystalline argon systems did not cool below appropriate closure temperatures until during or after extensional WNW-vergent movements. Quartz microfabrics indicate that temperatures were higher than those required for argon retention in muscovite until the end of the WNW-directed nappe translation (extension), and that lower temperatures were maintained during subsequent movements along W-and NW-dipping extensional ductile shear zones. The 40 Ar/ 39 Ar muscovite ages are therefore interpreted to post-date the extensional WNW-directed shearing along the de ´collement zone, and closely date the initiation of W-and NW-dipping extensional shear zones. When compared to the age of contractional deformation, the results confirm that extension followed orogenic contraction very shortly after the main, Scandian orogenic phase.

We use discrete element modeling to investigate three-dimensional fault geometry and the three-dimensional evolution of a fault network that develops above a 60° dipping planar pre-existing weakness striking 60° relative to the extension direction. The evolution of the fault network comprises three stages: (i) reactivation of preexisting structure and nucleation of new faults (0-10% extension); (ii) radial propagation and interaction between reactivated structure and new faults (15%-20% extension); and (iii) linkage between reactivated structure and adjacent faults (20%-25% extension). During the first stage, the pre-existing structure mostly reactivates, forming a long and under-displaced fault. New faults are mainly extensionperpendicular and dip at 60°. During the second stage, 'saw-tooth' fringes grow upwards from the upper tip of the reactivated structure (which becomes the major fault) and influence the density and orientation of surrounding faults. During the third stage, the reactivated structure links laterally and vertically with adjacent faults, creating non-planar fault geometries. Following linkage, the reactivated structure enhances the displacement of linked faults along branch lines. Our study demonstrates that pre-existing weak faults can be reactivated, propagating upwards in an irregular ('saw-tooth') pattern, and affecting fault density, orientation, dip and displacement, and providing the nucleation site of new faults.

Pre-existing structures within crystalline basement may exert a significant influence over the evolution of rifts. However, the exact manner in which these structures reactivate and thus their degree of influence over the overlying rift is poorly understood. Using boreholeconstrained 2D and 3D seismic reflection data from offshore Southern Norway we identify and constrain the three-dimensional geometry of a series of enigmatic intrabasement reflections. Through 1D waveform modelling and 3D mapping of these reflection packages, we correlate them to the onshore Caledonian thrust belt and Devonian shear zones. Based on the seismic-stratigraphic architecture of the post-basement succession we identify several phases of reactivation of the intrabasement structures associated with multiple tectonic events. Reactivation preferentially occurs along relatively thick (c. 1km), relatively steeply dipping (c. 30°) structures, with three main styles of interactions observed between them and overlying faults: (i) faults exploiting intrabasement weaknesses represented by intra-shear zone mylonites; (ii) faults that initiate within the hangingwall of the shear zones, inheriting their orientation and merging with said structure at depth; or (iii) faults that initiate independently from and cross-cut intrabasement structures. We demonstrate that large-scale discrete shear zones act as a long-lived structural template for fault initiation during multiple phases of rifting.

Observations from quartz-rich eolian Navajo Sandstone in the Buckskin Gulch site in southernmost Utah show that pure compaction bands only occur in sandstones where current porosity > 0.29 AE 3, permeability > 10 AE 7 darcy, and grain size > 0.4 mm e properties restricted to the lower and most coarsegrained and well-sorted parts of grain flow units within the dune units. Hence a direct correlation between stratigraphy and band occurrence has been established that can be used to predict deformation band occurrences in similar sandstone reservoirs. We show that the pure compaction bands formed perpendicular to a subhorizontal s 1 , bisecting conjugate sets of shear-enhanced compaction bands. The latter bands locally developed into sheardominated bands that transect entire dune units, suggesting that an increase in the amount of simple shear promotes band propagation into less porous and permeable lithologies. Stress considerations indicate that, as a continuous and overlapping sequence of events, pure compaction bands in quartz-rich Navajo Sandstone initiated at 10e20 MPa (w1 km depth), followed by shear-enhanced compaction bands that locally developed into more stratigraphically extensive sheardominated bands. The rare combination of special lithologic and stress conditions may explain why pure compaction bands are rarely observed in naturally deformed sandstones.

with plaster as the deforming medium produce faults and related structures that closely resemble natural examples. The faults with the largest displacement are normally developed at about 25% overall extension @ = 1.25). Major faults develop as composite structures, and although the main movement may be accommodated by a relatively simple slip surface, the fault zones commonly develop internal, lense-shaped geometries. Small, synthetic faults dipping more steeply than the main zone are typical components of the fault zones, particularly on the hanging wall side. Fault displacements develop over 2 orders of magnitude, and the distribution of fault displacements closely follows a power-law relationship similar to data from seismic and field mapping. The main, through-cutting faults accommodate about 60-70% of the total deformation, while smaller, visible faults typically account for ca lO-20%. Only 2@30% extension is due to faults and ductile deformation that occur below the resolution of the models, which roughly corresponds to seismic resolution when scaled up to natural size. The internal fault-block formation may include zones of normal faults accommodating significant internal shear deformation associated with collapse of fault blocks. Collapse has been recorded in the upper part of footwalls, resulting in a flattening of the upper part of the main faults. Although internal block deformation by simple shear or other deformations can be shown to play a significant role in the deformation, a component of rigid-block rotation is demonstrated, for example by the rotation of steep normal faults into orientations where they appear as reverse faults.

U/Pb zircon dating and trace element geochemical analysis were performed on rhyolite clasts of different Middle Jurassic sedimentary mélanges from the Western Carpathian and Dinaric orogen. These igneous clast-bearing sedimentary successions were deposited on the westernmost passive margin of the Neotethys Ocean. During the latest Jurassic and Cretaceous, they became parts of different nappe stacks forming now the Inner Western Carpathians and some inselbergs within the Pannonian Basin. The Meliata nappe was stacked on the northern passive margin, while the Telekesoldal and Mónosbél nappes were part of the imbricated western -south-western margin. U/Pb dating of the 100m-sized blocks and redeposited smaller clasts and fine-grained sediments formed two age groups: 222.6±6.7 and 209.0±9 Ma. Trace element geochemistry suggested within plate continental volcanism as magma source. However, the measured ages are definitely younger than the classic, rift-related Anisian -Ladinian (238-242 Ma) magmatism, which was widespread along the western and south-western margin of the Neotethys Ocean (e.g. Dolomites, different Dinaridic units). On the other hand, similar, Late Triassic ages are reported from tuff intercalations from the Outer Dinarides and Western Carpathians, along with even more sparse effusive rocks of the Slovenian Trough. Trace element (incl. rare earth We have removed all remaining highlited texts, comments and responses. The text is clean. authors' response to reviewers' comments Click here to download authors' response to reviewers' comments 2018_Kover_IJES_reviewed2_final comments.docx 1 Late Triassic acidic volcanic clasts in different Neotethyan sedimentary mélanges: paleogeographic and geodynamic implications

This information may be provided in an alternative format if required. Contact the IDNR Clearinghouse at 217-782-7498 for assistance. The Illinois State Geological Survey (ISGS) conducts four tours each year to acquaint the public with the rocks, mineral resources, and landscapes of various regions of the state and the geological processes that have led to their origin. Each trip is an all-day excursion through one or more Illinois counties. Frequent stops are made to explore interesting phenomena, explain the processes that shape our environment, discuss principles of earth science, and collect rocks and fossils. People of all ages and interests are welcome. The trips are especially helpful to teachers who prepare earth science units. Grade school students are welcome, but each must be accompanied by a parent or guardian. High school science classes should be supervised by at least one adult for every ten students. The inside back cover shows a list of guidebooks of earlier field trips.

LOCATION

11N 14E Sec. 10 SBM latitude: 35.04721 longitude: -115.47393 (MRDS, 2011)

SW1/4NE1/4 sec. 16, T. 11 N, R. 14 E., S.B.M. This property lies within a State grant section which is included in the study area. (Moyle and others, 1986:130).

Mining activity increased during the World War I era. Production up to World War II from the Castor-Pollux (Columbia mine, Macedonia mine), Globe, Frisco No. 3, Double H Nos. 1 and 2, Jo Je, and Rex mines was sporadic until Kaiser Steel Corp. brought the Vulcan mine-Burro prospect into production in 1942. The Vulcan mine-Burro prospect produced 2.643 mi 11 ion long tons (Wright and others, 1953) of blast-furnace-grade i ran ore from a large open pit in Foshay Pass, 1/4 mi outside of the study area. Production ceased in 1947 with the acquisition and development by Kaiser of the Eagle Mountain deposit, near Desert Center, CA. After World War II, only minor production was reported from the Silver Buddy, Rex, and Bonanza King mines and, possibly, the Grande 1-7 or Max Dorl and 2 mines. Several mines and prospects (Bell McGilroy, Mitchell, Mexican, etc.), which were worked primarily from the 19401 s to the early 19601 s (Wright and others, 1953; USBM statistical files), are within the Mitchell Caverns State Park on the southeast side of the study area. (Moyle and others, 1986, p. 189).

The early history of the property is unknown. Described by and Tucker and Sampson (1930, p. 235; 1931, p. 295-296), Eric (1948, p. 305) and Wright and others (1953 p. 35) tables as the Frisco No. 5 owned and operated by P. Thebadeau of Kelso, California about 1930-1931. A claim notice indicates that the Double H Nos 1 & 2 were located by E.C. Herndon and G. B. Hallis in December, 1948 (Moyle and others, 1986:130).

The deposit is a 1- to 3-ft-thick quartz vein and a siliceous, altered shear zone in  deeply weathered iron-oxide-stained granite gneiss (fig. A-15). The N. 50o to 60 o W. striking, 45 o to75 o NE dipping, tabular structure crops out approximately 1,000 ft exhibits and has massive a vertical exposure of 170. The quartz is white to gray, exhibits massive comb structure, and contains disseminated pyrite, galena, sphalerite, and minor chalcopyrite (Moyle and others, 1986:130).

The Double H Nos. 1 & 2 Mine has inferred subeconomic resources of 17,000 tons averaging 0.4 oz/ton a (Moyle and others, 1986:36; Goldfarb and others, 1988: Table 2, p. D11).

The subsurface geology of Okigwe in southeastern Nigeria was studied and interpreted for resource potential using gravity data. The geology of Okigwe makes the area suitable for hydrocarbon exploration, mineral prospecting, and geothermal investigations. We carried out a detailed analysis of the region's Bouguer gravity anomalies, including residual, regional, and derivative properties. The Bouguer anomaly map displays strong positive anomalies (13.0-21.7 mGal) in the Ohia River and Eziagu, indicating the presence of thick igneous or metamorphic rock formations. In Umuawke and Mpam, smaller anomalies (-10.0-0.0 mGal) suggest sedimentary deposits or aquifers. Residual anomalies revealed high-density formations around Ezike and Eziagu, likely igneous intrusions or uplifted blocks, and low-density basins around Umu Nwa Nwa and Afara. Subsequently, regional gravity anomaly maps highlighted structural patterns and basin configurations. Batholiths or dense basins correlated with positive anomalies, whereas sedimentary deposits or tectonic subsidence were linked to negative anomalies. Application of vertical and tilt derivatives enhanced the detection of fault zones and lithological boundaries. SPI depth estimates indicated sedimentary basins exceeding 5000 meters, favourable for hydrocarbon formation. The results confirm Okigwe's complex geological framework, shaped by tectonic and sedimentary processes. Gravity techniques proved essential for subsurface characterisation of Okigwe, as they identified mineralised zones, potential hydrocarbon reserves, and extensive fault networks.

The Maliau Basin is one of a series of saucer-shaped basins found in Central and Southeast Sabah. These basins are depositional sites of ancient sedimentary rocks. The Maliau Basin is made up of about 7,500 metres thick sandstone and mudstone layers deposited in a deltaic-coastal environment, assigned the Kapilit Formation. The layer at the base of the basin consists mainly of mudstones reaching up to 2,000 metres thick. Near the rim of the basin, thick sandstone interbedded with thin mudstone and coal seam occur. Towards the centre of the basin a series of sandstone-dominated and mudstone-dominated sequences of various thicknesses occur. The deposition took place during the Middle Miocene epoch (10-15 million years ago). The basin sits on older sedimentary rocks (Tanjong Formation), also comprising of thick layers of sandstone and mudstone, with slight unconformity. The orientation of bedding generally follows the semi-circular shape of the basin. The dip of bedding varies from 5 degrees to 40 degrees. The dip becomes gentler towards the rim of the basin. Based on the

Fluids can circulate in all levels of the crust, as veins, ore deposits and chemical alterations and isotopic shifts indicate. It is furthermore generally accepted that faults and fractures play a central role as preferred fluid conduits. Fluid flow is, however, not only passively reacting to the presence of faults and fractures, but actively play a role in their creation, (re-) activation and sealing by mineral precipitates. This means that the interaction between fluid flow and fracturing is a twoway process, which is further controlled by tectonic activity (stress field), fluid sources and fluxes, as well as the availability of alternative fluid conduits, such as matrix porosity. Here we explore the interaction between matrix permeability and dynamic fracturing on the spatial and temporal distribution of fluid flow for upward fluid fluxes. Envisaged fluid sources can be dehydration reactions, release of igneous fluids, or release of fluids due to decompression or heating.

Hydrofractures, or hydraulic fractures, are fractures where a significantly elevated fluid pressure played a role in their formation. Natural hydrofractures are abundant in rocks and are often preserved as magmatic dykes or sills, and mineral-filled fractures or mineral veins. However, we focus on the formation and evolution of non-igneous hydrofractures. Here we review the basic theory of the role of fluid pressure in rock failure, showing that both Terzaghi’s and Biot’s theories can be reconciled if the appropriate boundary conditions are considered. We next discuss the propagation of hydrofractures after initial failure, where networks of hydrofractures may form or hydrofractures may ascend through the crust as mobile hydrofractures. As fractures can form as a result of both tectonic stresses and an elevated fluid pressure, we address the question of how to ascertain whether a fracture is a hydrofracture. We argue that extensional or dilational fractures that formed below c. 2–3 ...

Uncertainty still persists on the structure and evolution of the West Antarctic Rift System, which is one of the largest extensional provinces on Earth. In this paper, we present results of a combined structural and apatite fission track study of the western shoulder of the rift system, in the western coastal area of the Ross Sea between the Reeves and the Mawson glaciers. Structural data indicate that the onshore fault pattern is dominated by N–S striking right‐lateral strike‐slip to transtensional fault systems and their related subsidiary fault populations in the damage zones. Thermochronological data support a Cenozoic age for these faults and, in particular, the onset of the oblique rifting event at about 50 Ma, in Eocene times. Apatite fission track analyses also suggest the possible occurrence of an older cooling/exhumation event in Cretaceous times. When integrated with the geological and geophysical data sets available in the literature, our structural and thermochronologic...

Este trabalho apresenta, mediante uma abordagem geoambiental, uma caracterização geológicoestrutural do subsolo granítico da cidade do Porto, e ainda uma avaliação hidrogeológica, isotópica e ecotoxicológica da água subterrânea. Este estudo foi realizado ao longo de um sistema de galerias subterrâneas, com mais de 3 km de extensão, captando o antigo manancial de Paranhos (também conhecido como o manancial da Arca d'Água), o qual constituiu, durante mais de cinco Séculos, uma das principais fontes de abastecimento de água à população da cidade do Porto. A investigação em curso inclui diversas técnicas, onde se destacam: (i) a elaboração dum quadro geológico, morfotectónico e geotécnico; (ii) a inventariação de pontos de água para a caracterização hidrogeológica; (iii) a recolha de amostras de água subterrânea para estudo hidrogeoquímico convencional e isotópico e ecotoxicológico. Por fim, procedeu-se à elaboração de mapas temáticos integradores da informação subterrânea (e.g., mapa geológico-estrutural, mapa do grau de alteração, mapa de hidrogeológico) e da cartografia superficial disponível. Um estudo desta índole pretende contribuir para uma melhor gestão do geo-espaço urbano, quer em termos históricos e patrimoniais, quer no que toca ao aproveitamento da água para diversos fins de utilidade pública.

Este trabalho apresenta, numa abordagem multidisciplinar, uma caracterização geológicoestrutural e geotécnica do subsolo granítico da cidade do Porto. Este estudo foi realizado ao longo de um sistema de galerias subterrâneas, com mais de 3 km, captando o antigo manancial de Paranhos (também conhecido como o manancial da Arca d'Água ou da Arca das Três Fontes), o qual constituiu, durante mais de cinco séculos, uma das principais fontes de abastecimento de água da população da cidade do Porto. O trabalho envolveu, numa fase inicial, a cartografia geológica e geotécnica subterrânea do traçado das galerias (escala 1/1.000), o levantamento geológico-geotécnico das superfícies de descontinuidades ao longo de todo o traçado subterrâneo e a realização de ensaios geomecânicos do material-rocha. Numa fase posterior, foi efectuado o estudo da compartimentação do maciço granítico com vista ao seu zonamento geotécnico e geomecânico. Por fim, procedeu-se à elaboração de mapas temáticos integradores da informação subterrânea (e.g., mapa geológico-estrutural, mapa do grau de alteração, mapa de zonamento geotécnico) e da cartografia superficial disponível. Um estudo desta índole pretende contribuir para uma melhor gestão do geo-espaço urbano, quer em termos históricos e patrimoniais, quer no que toca ao aproveitamento da água para diversos fins de utilidade pública.

New paleomagnetic data from Permo-Triassic and Late Cretaceous rocks yield a consistent trend of vertical-axis-tectonic-rotations which are consistent with the Central Andean Rotation Pattern (CARP). However, three sites in the Tuina Formation and one site in the Purilactis Group record large rotations (80 ). These mayor rotations are probably due to dextral-transpressive deformation occurring in close relation with the Incaic tectonic phase. Consequently, it is possible to infer that previous tectonic phases Peruvian and K-T would not have produced significant tectonic rotations in the area.

Certain degrees of safety, economic, and financial risk are implicit in any mining operation. At Thabazimbi Mine, slope stability was one of the major sources of risk, largely due to data uncertainties. Consequently, a risk-based approach in slope design was followed. On 6 June 2015, a slope failure occurred in Thabazimbi Mine's Kumba pit, involving approximately 65 million tonnes of rock failing into the pit and the valley below. Although the failed mass moved rapidly and resulted in a run-out distance of approximately 900 m, controls had been put in place to successfully evacuate all personnel. Risk assessment during the onset of failure supported the decision to not compromise the safety of personnel in any way, leading to unavoidable equipment loss. This contribution presents the failure as a case study in the context of a risk-based approach to slope design as well as the importance of implementing geotechnical controls to effectively manage slope instability risk. Furthermore, a comprehensive back-analysis was performed, on a fully constrained 3D model, utilising 3DEC software, to gain insights into the failure mechanism. In conclusion, lessons from the Thabazimbi slope failure are valuable as they demonstrate the importance of following a risk-based approach in slope design to effectively manage safety and financial risk in open pit mines.

Geological mapping was carried out on the Gilas and Malau rivers in the Muaradua area, South Ogan Komering Ulu Regency, South Sumatra by observing the presence of joints, faults, and veins in the granite and phyllite rock outcrops of the Tarap Formation. Research on pattern geometry and vein type in the crushing zone is focused on measuring the direction (trend) of veins and joints. The measurement results are then analyzed to obtain a general pattern of quartz and calcite veins so that the orientation of their development can be known. The method used in this study is in the form of determining the orientation and geometry of the veins based on classifications that refer to several studies, then an analysis is carried out using DemNAS data to determine the general direction of the straightness pattern of the study area. The quartz veins that developed in the study area have an extensional fracture type with the geometry found in the form of isolated, abutting, cutting, mutually-cut...

sufrido una serie de movimientos en los años 1924, 1954, 1974 y 2002, todos ellos desencadenados por episodios de lluvias intensas y prolongadas durante varios días. En el año 2002, la posibilidad de taponamiento del torrente por la masa deslizada, puso en alerta a las autoridades de la isla y condicionó la realización de un estudio detallado de la zona. Este estudio incluyó la realización de perfiles geofísicos mediante sísmica de refracción y tomografía eléctrica; la ejecución de 4 sondeos mecánicos de reconocimiento, así como numerosos ensayos in situ y de laboratorio que tuvieron como objetivo determinar las propiedades hidráulicas y resistentes de los materiales de la ladera. El análisis e interpretación de los datos obtenidos pone de manifiesto la existencia de un deslizamiento principal de tipo planar, cuya superficie de rotura coincide con el contacto entre dos tipos de materiales de diferente naturaleza y propiedades resistentes. El deslizamiento (y sucesivas reactivaciones), aunque superficial, involucra un volumen de material de unos 300.000 m 3 y determina que la zona sea una de las de mayor riesgo por este tipo de procesos en la isla, debido a la cercanía del pueblo de Fornalutx. Palabras clave: caracterización geomecánica, deslizamientos, laderas, Mallorca, riesgo

The southeast Hazara forms a part of a fold and thrust belt in the Lesser Himalayas of Pakistan. This paper attempts to address the structural geology of a part of southeastern Hazara and explains the geometry and evolution of various structures present within the Hazara Slates and overlying younger rocks. The study area is covered by Pre-Cambrian and Mesozoic-Cenozoic age rocks that have undergone severe deformation, as illustrated by the development of southeast verging thrust faults and associated folds. The structural evolution of the study area is controlled by the deformation associated with Hazara Thrust Zone which is the major tectonic event and has resulted in thrusting of Pre-Cambrian Hazara Slates over the Mesozoic-Cenozoic rocks. Two discrete phases of deformation have been identified in the area, inferred from the cleavage study in the Hazara Slates. Cleavages in the Hazara Slates include a well developed bedding parallel slaty cleavage 51 which is the result of Pre-Cam...

The current research work mainly focuses on tectonic evolution of the Central Kirthar Fold Belt. It also deals with the structural impact of the Late Cretaceous/Paleocene, Indian-Eurasian collision on the Central Kirthar Fold Belt which is situated in the western shear zone of Indian Plate. The Kirthar Fold Belt is different from the rest of western shear zone because it is mainly deformed by compressional tectonics which has created wide anticlines, narrow synclines and overturned folds as shown by geological mapping. It has been observed that thin-skinned deformation has played a major role in structural disharmony which is mainly seen in the Early Eocene Ghazij and Oligocene Nari formations. Seismic data shows thick-skinned deformation because the faults seem to penetrate deeper stratigraphic levels. Involvement of the basal decollement and the penetration of the interpreted faults to the level of basement rocks is also evident from the exposure of Jurassic/Cretaceous rocks at su...

The Jeremoabo fault, located in the Early Cretaceous Reco ˆncavo -Tucano Rift, northeastern Brazil, represents an example of transfer fault. A field-based structural analysis along 20 km of exposures revealed an E -W-trending and steeply dipping reverse-sinistral fault that resulted from transpressional reactivation of a pre-existent weak zone. The fault is associated with a 5-km-wide footwall deformation zone, in which sandstone layers are folded and locally overturned becoming parallel to the fault. The deformation zone contains a pervasive system of NEand NNW-trending conjugate Riedel shear fractures of outcrop to kilometer scale. A paleostress analysis based on these Riedel fractures indicated s 1 and s 3 trending, respectively, 0168 and 1088, and s 2 subvertical, consistent with transpression and local switch between s 1 and s 2 relative to the regional paleostress field. The Jeremoabo fault links smaller rift border faults and has sense of slip consistent with the mapped offset of the basin border. Its transfer function is attested by linkage with a major dextral transfer fault and a transfer zone during the rifting period. By acting together these structures accommodated the change in asymmetry between the two major half-grabens of the rift.

The earthquake (M w =6.3) was located in the central Italy region of Abruzzo. Much of the damage occurred in the capital city of L'Aquila, a city of approximate population 73000, although many small villages in the surrounding region of the middle Aterno river valley were also significantly damaged. In the weeks following the earthquake, the Geo-Engineering Extreme Events Reconnaissance (GEER) international team, comprised of members from different European countries and the U.S., was assembled to provide post-earthquake field reconnaissance. The GEER team focused on the geological, seismological, and geotechnical engineering aspects of the event. We describe the principal seismological findings related to this earthquake including moment tensors of the main shock and two triggered events, the aftershock pattern and its variation with time, tectonic deformations associated with the main shock, surface fault rupture, and the inferred fault rupture plane. We describe damage patterns on a village-to-village scale and on a more local scale within the city of L'Aquila. In many cases the damage patterns imply site effects, as neighbouring villages on rock and soil had significantly different damage intensities (damage more pronounced on softer sediments). The April 6 mainshock was the best-recorded event to date in Italy. We present metadata related to the recording sites and then present preliminary comparisons of the data to GMPEs. Those comparisons support the notion of faster distance attenuation in Italy relative to the average for active regions as reflected in NGA GMPEs. Several incidents of ground failure are then discussed, including a number of rockfalls and minor landslides. Perhaps the most significant incidents of ground failure occurred at Lake Sinizzo, for which we describe a number of slumps and spreads around the lake perimeter. This is documented using field observations as well as LIDAR and bathymetric data.

With the aim of studying the multi-scale fault architecture and permeability in hydrocarbon-rich porous carbonate rocks, we are currently involved in a project focused on the structural analysis of fractured and faulted platform-to-ramp carbonates cropping out in ...

This study presents a data set comprising estimated permeabilities of 22 natural mudstones which also have been characterised in terms of their pore size distribution, porosity, grain density and Total Organic Carbon (TOC) content. Pore size distribution and grain density were determined using mercury porosimetry and pycnometer method. TOC was determined by direct combustion of the organic carbon in LECO RLS-100 Carbon Sulphur analyser. Permeabilities were estimated based on the measured pore throat size distribution plus assumed pore alignment and pore shape using the model of Yang and Aplin. TOC and grain density ranges from 3.44-9.98% and 2.61-2.70 g/cm 3 , respectively. Porosity decreases from ~24-3% between the depth range of 1515-4781 m. The pore size distribution data show that the mean pore radius decreases from ~36-2 nm within the same depth range, the shift to smaller mean pore radii is driven primarily by the collapse of pores larger than 10nm with increase in consolidation. These values represent some of the smallest pore sizes known for rocks and in part provide a qualitative explanation for the low shale permeabilities. Estimated vertical permeabilities range from 9.5×10G 23 to 8.6×10G 21 m 2 . In general, permeability decreases logarithmically with porosity.