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Near-surface buckling of horizontally laminated sedimentary rock has been reported to occur in Ontario, Canada and the Upper Midwestern U.S. where high horizontal in situ stresses occur. Often referred to as 'pop ups', these buckling events typically occur suddenly and are commonly accompanied by a rapid energy release akin to rock bursting. In recent years, this mode of instability has become a concern for surface mining and quarry operations, in particular in cases where the buckling failure creates a connection between an underlying aquifer and the excavation. Despite previous research on the topic of buckling instability, there remains many limitations in development of a design methodology to account for buckling failure. The main objective of this research study is to experimentally investigate a simple buckling failure mode, known as three hinge buckling (THB): buckling that involves rotation of a two-rock block configuration with a central hinge. An experimental testing procedure was developed to reproduce THB at laboratory scale, including the design and fabrication of a new testing apparatus and development of a testing methodology. A preliminary THB test was conducted and the results are presented. A simplified, elastic block numerical model was developed using the distinct element method code 3DEC in order to provide insight into the laboratory experiment. Overall, this newly-developed test was able to reproduce the THB failure experimentally in the laboratory and to provide an opportunity to observe the brittle buckling failure to obtain valuable, quantifiable information about the failure process. [ABSTRACT FROM AUTHOR]

The major regions of Taiwan consist of high-relief terrain exposed to frequent typhoons and earthquakes. Recently, thousands of potential large-scale landslides have been delineated via remote sensing analysis and field surveys. However, little attention has been paid to the stability of colluvium, which is a potential hazard. This study investigated a paleo-rockslide site in detail and proposes a geological model to explain the failure mechanism. The studied area is in Jiasian, Southern Taiwan, and the site is a dip slope consisting of Miocene sedimentary rocks. Detailed topographic features, including residual slip surfaces, platforms, scarps, and colluviums, are identified using the slope map of a 1- m airborne remotely sensed digital elevation model. Platforms beneath the residual slip surfaces represent the topographic features of the paleo-rockslide, an interpretation validated by field works and core analysis. The platforms consist of a displaced rock mass (DRM) with a gentle bedding dip angle and interbedded structure that has been preserved. A geological model is established according to the data compiled; outcrops of DRM and colluviums on bedrock were delineated in the geological map and profiles. Outcrops of shear off, buckling, and compressive ridges within the alternating sandstone and shale are distributed at the toe of the residual slip surfaces. A geological model with identified topographic features is adopted to establish the geomorphological evolution of the site. A buckling-induced rockslide model in the dip slope of the interbedded layers is proposed, and potential future slope failure scenarios can be evaluated using the geomorphological evolution model. [ABSTRACT FROM AUTHOR]

Foreland deformation, in the form of arches or uplifts, occurred throughout the eastern Rocky Mountains region during the Laramide orogeny (75-50 Ma). Arches with the same structural style developed in the mid-continent region, east of the Rocky Mountains, although these were subsequently buried by Tertiary sedimentary rocks. We attribute deformation in the Rocky Mountain foreland and continental interior to folding of the entire lithosphere (lithospheric buckling) as a result of horizontal endload on the western edge of North America. The observed wavelength of arches in the western United States is ca. 190 kin, a spacing consistent with a lithospheric buckling interpretation. This buckling model provides a mechanical explanation for the distinction between "thin-skinned" Sevier-style and "thick-skinned" Laramide-style deformation, which depends respectively upon the decoupling or coupling of lithospheric layers. Additionally, the buckling model explains concurrent tectonism east of the Rocky Mountains during Late Cretaceous time. Dextral shearing within the block uplifts indicates that the deformation was broadly transpressional during the Laramide orogeny. [ABSTRACT FROM AUTHOR]

Response analysis of the buried pipeline subjected to reverse fault displacement is very important for design, detection and protection of buried pipelines. This paper looks at the buckling behavior of a buried pipeline subjected to reverse fault displacement in the rock stratum. Effects of internal pressure, wall thickness, fault displacement and burial depth on the buckling mode and the axial strain of the buried pipeline are discussed. The results show that there are two buckling locations on the buried pipeline subjected to reverse fault displacement in the rock stratum and that the buckling modes of the buried pipes with different internal pressures are different. The two buckling locations are not symmetrically distributed along the fault plane. The buckling mode ranges from collapse to wrinkle as the internal pressure increases. The buckling phenomenon becomes more serious as the fault displacement increases, and the shape of the deformation curve changes from the S-shape to the Z-shape. The process of pipeline deformation can be divided into three stages. There is no buckling in the first stage. The second stage is a transition stage, buckling appears on the buried pipeline. Buckling is more serious in the third stage. Fault displacement has a small effect on the maximum strain position of the buried pipeline. The deformation curve of the buried pipeline is smoother as the wall thickness increases. The maximum axial strain of pressure pipes first increases and then decreases as the wall thickness increases. [ABSTRACT FROM AUTHOR]

Based on the combination of FLAC software and strength reduction method, the applicability of three kinds of instability criterion of the stability of dip slopes with interbeddings of weak and hard rocks is studied. Then the failure process, failure mode and stability of the slopes are analyzed. The results show that: (1) the maximum unbalance rate affects the final calculated results; there is no certain relation between the convergence of calculation and the slope stability. The convergence of the displacement curves of key points and the ultimate displacement values should also be concerned to determine the slope stability. The maximum unbalance rate and the amplitude of the reduction affect the determination of the characteristic point in the displacement curve. It is difficult to quantitatively evaluate the shear strain rate when judging the slope stability, the judgment is not convenient and the error is large. Combining with calculation convergence criterion and feature point displacement mutation criterion is helpful to improve the accuracy of judgment on the limit state of the slope. (2) Slope deformation and failure process can be roughly divided into four stages qualitatively; the rock mass has buckling failure can be divided into three stages according to the deformation characteristics. The potential shear export of slope with buckling failure locates above the slope toe. Different combinations of weak and strong rock thickness does not affect the failure mode of slope, which all bellows to buckling failure mode, but it will affect the slope stability coefficient; with the increase of the thickness of strong rock and weak rock, the stability coefficient increases. If the thickness of the strong rock increases, the stability coefficient increases as well when the thickness ratio is constant. [ABSTRACT FROM AUTHOR]

Abstract: A number of prehistoric landslides and rock avalanches occurred in the folded and faulted section of the Molasse Zone in Vorarlberg, Austria. Some developed into a Sturzstrom, defined as a ‘rapidly moving fluidised mass movement of large volumes of rock, derived from the disintegration of a falling rock mass, that spread under the influence of gravity’. Their impact on the landscape usually is related to obstruction of rivers and valleys. In this paper, we analyse the geomorphology and the failure mechanism of a relative small ‘Sturzstrom’. The failure mechanism can be described as a ‘buckling failure’. The morphological situation indicates that failure took place after local deglaciation by the end of the Upper Würm. The period of failure coincides with glacial and ice-marginal remnants, which developed between 15.000 and 14.600 BP. The lithological sequence and rock structure, as well as the impact of the processes related to the former glacial environment, were major causal conditions. The rock sequence consists of conglomerates, sandstone layers, and marls. Next to glacial scouring, which increased the inclination of the valley slopes, the effect of late-glacial unloading and postglacial processes, such as weathering and fluvial erosion, subsequently weakened the mass rock fabric until failure occurred. Discontinuity orientation measurements, geostructural and geomechanical conditions, and the former hydrological and geomorphological conditions support bucklings failure. In fact, three-hinge buckling may have occurred. The frontal section of the Sturzstrom consists mainly of large conglomerate blocks, averaging 1.5 m3 in volume, although megablocks, reaching of up to 4000 m3, are present as well. The volume of the entire Sturzstrom equals approximately 10×107 m3. Present activity is only restricted to minor rock falls derived from the conglomerates and mudflows originating from the marl layers. [Copyright &y& Elsevier]

The up to 450 m-thick Upper Jurassic Lemeš Formation includes organic-rich deep-water (max. ~ 300 m) sedimentary rocks deposited in the Lemeš Basin within the Adriatic Carbonate Platform (AdCP). The Lemeš Formation was investigated regarding (1) bio- and chemostratigraphy, (2) depositional environment, and (3) source rock potential. A multi-proxy approach—microfacies, Rock–Eval pyrolysis, maceral analysis, biomarkers, and stable isotope ratios—was used. Based on the results, the Lemeš Formation is subdivided from base to top into Lemeš Units 1–3. Deposition of deep-water sediments was related to a late Oxfordian deepening event causing open-marine conditions and accumulation of radiolarian-rich wackestones (Unit 1). Unit 2, which is about 50 m thick and Lower early Kimmeridgian (E. bimammatum to S. platynota, ammonite zones) in age, was deposited in a restricted, strongly oxygen-depleted basin. It consists of radiolarian pack- and grainstones with high amounts of kerogen type II-S organic matter (avg. TOC 3.57 wt.%). Although the biomass is predominantly marine algal and bacterial in origin, minor terrestrial organic matter that was transported from nearby land areas is also present. The overlying Unit 3 records a shallowing of the basin and a return to oxygenated conditions. The evolution of the Lemeš Basin is explained by buckling of the AdCP due to ophiolite obduction and compressional tectonics in the Inner Dinarides. Lemeš Unit 2 contains prolific oil-prone source rocks. Though thermally immature at the study location, these rocks could generate about 1.3 t of hydrocarbon per m2 surface area when mature. [ABSTRACT FROM AUTHOR]

Highlights: [•] Discussing the exhumation processes of high-pressure rocks in the West African Craton (2.2–2.0Ga). [•] Thickening of the crust by buckling leading to burial of sedimentary rocks. [•] Partial melting of the mid to lower crust and development of gravitational instabilities. [•] Exhumation controlled by large-scale folding and re-melting of felsic material. [Copyright &y& Elsevier]

The Eastern Iranian Ranges are considered to be either a suture zone produced by closure of a Neo-Tethyan back-arc basin between the Lut and Afghan blocks or an oroclinal buckling of multiple terranes accreted to the active margin of the Neo-Tethyan Ocean. Both models are based on the presence of Cretaceous ophiolite complexes and sequences of Eocene turbiditic sedimentary rocks. The Dumak ophiolitic mélange, a significant ophiolitic assemblage that crops out in the western portion of the orogen adjacent to Lut, contains all the essential elements of a typical ophiolite in a matrix of serpentinite and clay-rich sediments. Ultramafic-mafic cumulates in the mélange are characterized by medium, non-rhythmic bedding in limited outcrops where they are in tectonic contact with other ophiolitic units. The cumulates consist of plagioclase-bearing dunite, troctolite, Cpx-troctolite and gabbro composed chiefly of olivine, plagioclase, and clinopyroxene accompanied by rare orthopyroxene. This assemblage is very similar to the differential crystallization sequence of tholeiitic magma at modern mid-ocean ridges. The clinopyroxene in these rocks is diopside (En = 47–49) and the plagioclase is bytownite (An = 71–77). Whole-rock geochemistry of samples from the crustal sequence of Dumak mélange are characterized by low TiO 2 (0.03–0.17 wt%). Investigation of this crystalline sequence and geochemical properties of the rocks suggests that they can be considered as the low-Ti ophiolite originated from mid-ocean ridges. Additionally, the positive Eu anomalies as well as comparison of frequency of LREE and HREE in the mafic and ultramafic samples indicate the cumulates formed by fractional crystallization and differentiation of mantle-derived magmas. According to petrographic, geochemical, and structural evidence, it is possible that the Dumak ophiolite, after being formed or displaced between Lut and Afghan blocks, was firstly accreted to the south of the Lut block and then re-mixed into Eocene sediments emplaced in the current position. • The major and trace element geochemistry as well as the mineral chemistry of the ultramafic to mafic cumulates suggest that the parental magmas of the Dumak cumulates were derived from a previously depleted mantle source at a mid-ocean ridge. • The crystallization order of the minerals of the Dumak cumulates (olivine ± Cr-spinel → plagioclase → clinopyroxene → orthopyroxene) is consistent with crystallization of mid-ocean ridge magmas. • The highly depleted nature of the Dumak rocks and some features of the REE are compatible with very weak refertilization in a SSZ environment. [ABSTRACT FROM AUTHOR]

During the Cretaceous, the Neuquén Basin transitioned from an extensional back-arc to a retroarc foreland basin. We present a multi-proxy provenance study of Aptian to Santonian (125-84 Ma) continental sedimentary rocks preserved in the Neuquén Basin used to resolve changes of sediment drainage pattern in response to the change in tectonic regime. Sandstone petrology and U-Pb detrital zircon geochronology constrain the source units delivering detritus to the basin; apatite U-Pb and fission track dating further resolve provenance and determine the age and patterns of exhumation of the source rocks. Sandstone provenance records a sharp change from a mixed orogenic source during Aptian time ( ca. 125 Ma), to a magmatic arc provenance in the Cenomanian ( ca. 100 Ma). We interpret this provenance change as the result of the drainage pattern reorganisation from divergent to convergent caused by tectonic basin inversion. During this inversion and early stages of contraction, a transient phase of uplift and basin erosion, possibly due to continental buckling, caused the pre-Cenomanian unconformity dividing the Lower from Upper Cretaceous strata in the Neuquén Basin. This phase was followed by the development of a retroarc foreland basin characterised by a volcanic arc sediment provenance progressively shifting to a mixed continental basement provenance during Turonian-Santonian (90-84). According to multi-proxy provenance data and lag times derived from apatite fission track analysis, this trend is the result of a rapidly exhuming source within the Cordillera to the west, in response to active compressional tectonics along the western margin of South America, coupled with the increasing contribution of material from the stable craton to the east; this contribution is thought to be the result of the weak uplift and exhumation of the foreland due to eastward migration of the forebulge. [ABSTRACT FROM AUTHOR]

In low-wall stability analysis, there are many geological factors that must be considered; therefore, in determining the method and parameters, real conditions in field must be taken into consideration. This paper examines what factors need to be considered in low-wall stability analysis, including condition of the study area. The analysis method used in this study was back analysis on a low-wall slope where failure occurred, by collecting all the details of geological conditions and performing finite-element-based stability analysis to break down the contribution of each factor. This method is expected to provide detailed information about geological condition that may be a contributing factor to slope stability analysis. The result showed that physical and mechanical properties, slope length, bed thickness, bedding ratio, lithology type, and aquifer type need to be considered. These considered conditions become important factors in the analysis, especially in determining suitable slope stability method as well as evaluating reasonable results of low-wall stability analysis. Comprehensive slope stability analysis may help improving quality of slope to be optimal. The result of this analysis can be implemented for layered sedimentary rocks with low mechanical properties. [ABSTRACT FROM AUTHOR]

Purpose: The present paper focuses on the propagation behaviour of Shear Horizontal (SH) waves in a fluid-saturated functionally graded fractured porous material layer consisting of sedimentary rocks perfectly bonded to an irregular piezoelectric semi-infinite substrate with flexoelectric effect. Two distinct cases corresponding to two differently shaped irregularities, viz. rectangular and parabolic, are considered at the layer-substrate interface. Methods: With the help of Fourier transform, inverse Fourier transform, and perturbation technique, complex frequency relation has been derived for each type of irregular interface. Two different flexoelectric materials, viz. Lithium niobate (LiNbO 3) and Barium titanate (BaTiO 3) , are taken into account for performing comparative graphical analysis. Results: Obtained frequency relations are dissociated into real and imaginary components representing the dispersion and damping of SH-wave propagation. Dispersion and attenuation characteristics of SH-waves are executed graphically on the basis of several key parameters, such as irregularity, functional gradient, flexoelectric coefficient, volume fraction of matrix and fracture pores, piezoelectric, and dielectric constants. Conclusions: On applying the referred conditions, the dispersion equations for both type of irregularities fairly match with the Classical Love wave equation. This fact validates the consideration of the layered composite structures. The noteworthy effects of the key parameters on the dispersion and damping of SH-waves are revealed graphically. Moreover, the phase and damped velocities of SH-waves are observed to be significantly greater for LiNbO 3 than for BaTiO 3 in each irregular case. [ABSTRACT FROM AUTHOR]

We investigated the relationship between contractional deformation of sedimentary mass in the upper crust and the geodetic strain rate in a high-strain zone (part of the Niigata–Kobe Tectonic Zone) of the mid-Niigata region, Central Japan. We observed numerous examples of layer-parallel slip (bedding-plane slip) generated by folding. The slip layers have an average spacing of ~ 3.6 m (measured normal to bedding planes) at the Katagai site. In shallow sedimentary units of the upper crust, numerous bedding-plane slip events act to reduce the mechanical strength (effective elastic thickness) of sedimentary rocks under contractional deformation. The results support an existing model, based on geodetic observations, of mechanical decoupling between the weak sedimentary layers and basement. On the layer-parallel slip, we measured the friction coefficient of gouge generated by bedding-plane slip and of mud around non-slip surfaces using double-direct shear tests, and found no difference in frictional coefficient between slip and non-slip surfaces. [ABSTRACT FROM AUTHOR]

Abstract The Paleoproterozoic Central Lapland Granitoid Complex (CLGC) forms the northern core of the Fennoscandian Shield. We present here new U-Pb age data and review the existing ones from plutonic and metasedimentary rocks of the CLGC, and integrate the results with the structural field observations to decipher the tectonic history of this region. Granitoids vary in age from 2.43 Ga to 1.78 Ga, whereas metamorphic zircon overgrowths, both in granites and metasedimentary rocks, vary between 1.90 Ga and 1.76 Ga with several age peaks indicating prominent metamorphic pulses. The almost continuous growth of metamorphic zircon domains favors that the central part of the CLGC was near solidus for 100–120 Ma. A succession of five deformations and associated foliation-producing events, which were near-orthogonal to each other, have been identified. East-vergent thrusting and stacking (D1) commenced at ca. 1.92 Ga, and led to the onset of Barrovian-type metamorphism followed by a radical tectonic shift that yielded E-W trending D2 structures. Exhumation at 1.88–1.87 Ga caused decompression melting of thermally evolved thickened crust and led to the emplacement of large volumes of granites and triggering of Buchan-type metamorphic conditions. NE-SW collision (D3) at the southwestern margin of Fennoscandia heterogeneously overprinted the S3 fabric on D2 structures. Orogen parallel (NNW-SSE) buckling at 1.87–1.85 Ga formed oroclines in the hot linear arc segments. Renewed NNW-SSE shortening (D4) at 1.84–1.81 Ga produced long wavelength folds and caused the formation of domal structure in the CLGC. The final 1.78–1.76 Ga far-field collision (D5) in the west overprinted all the pre-existing structures. This complex multi- directional tectonic scenario provoked the intermittent exhumation phases between different contraction events of the CLGC. Highlights • Central part of the Lapland Granitoid Complex (CLGC) was near solidus for 100–120 Ma. • Five major deformation events (D1-D5) occurred between 1.92 Ga and 1.76 Ga. • Barrovian- to Buchan-type metamorphism at 1.88–1.87 Ga. • Migmatitic core was transformed to long wavelength folds during D4. [ABSTRACT FROM AUTHOR]

The Mesozoic subduction history of the Paleo‐Pacific plate below the East Asian margin remains contentious, in part because the southern part is poorly understood. To address this, we conducted a sediment provenance study to constrain Mesozoic subduction history below West Sarawak, Borneo. A combination of detrital zircon U‐Pb geochronology, heavy minerals, trace element, and bulk rock Nd isotope data were used to identify the tectonic events. The overall maturity of mineral assemblages, dominantly felsic sources, abundant Precambrian‐aged zircons, and low εNd(0) values (average −13.07) seen in Late Triassic sedimentary rocks suggest a period of inactive subduction near Borneo. Slab shallowing subduction occurred between 200 and 170 Ma based on subdued magmatism and tectonic compression across West Sarawak. From c. 170 to 70 Ma there was widespread magmatism and we interpret the Paleo‐Pacific slab steepened. Collectively, we show the Paleo‐Pacific plate subduction had variable slab dip histories in Borneo. Plain Language Summary: Modeling studies have shown that the ocean slab underwent periodic shallowing and steepening in the long‐term subduction system. To know the Mesozoic Paleo‐Pacific subduction history of the southern section, we established the subduction process of West Sarawak by studying the provenance of Mesozoic sedimentary rocks. Based on it, we subsequently deduce that west dipping subduction of the Paleo‐Pacific slab underwent periodic shallowing and steepening of slab dip from north to south. Key Points: Triassic sediments in West Sarawak were mainly sourced from the craton erosionPaleo‐Pacific slab underwent the Early Jurassic shallowing subduction, followed by slab steepening after the Middle Jurassic in West BorneoThe subduction of Paleo‐Pacific plate had variable slab dip histories from West Borneo to northeast China during the Mesozoic [ABSTRACT FROM AUTHOR]

Parasitic folds are typical structures in geological multilayer folds; they are characterized by a small wavelength and are situated within folds with larger wavelength. Parasitic folds exhibit a characteristic asymmetry (or vergence) reflecting their structural relationship to the larger-scale fold. Here we investigate if a pre-existing geometrical asymmetry (e.g., from sedimentary structures or folds from a previous tectonic event) can be inherited during buckle folding to form parasitic folds with wrong vergence. We conduct 2D finite-element simulations of multilayer folding using Newtonian materials. The applied model setup comprises a thin layer exhibiting the pre-existing geometrical asymmetry sandwiched between two thicker layers, all intercalated with a lower-viscosity matrix and subjected to layer-parallel shortening. When the two outer thick layers buckle and amplify, two processes work against the asymmetry: layer-perpendicular flattening between the two thick layers and the rotational component of flexural flow folding. Both processes promote de-amplification and unfolding of the pre-existing asymmetry. We discuss how the efficiency of de-amplification is controlled by the larger-scale fold amplification and conclude that pre-existing asymmetries that are open and/or exhibit low amplitude are prone to de-amplification and may disappear during buckling of the multilayer system. Large-amplitude and/or tight to isoclinal folds may be inherited and develop type 3 fold interference patterns. [ABSTRACT FROM AUTHOR]

In the article, our research of the tectono-stratigraphic imprints of the Indian–Asian plates collision in the outcrops of Kurram and North Waziristan agencies in Pakistan with the help of detailed mapping and subsurface modeling, is presented. Three tectonic domains have been identified in the research based on the stratigraphic mismatch including the Nappe Domain, the allochthonous Indian Plate margin (Orakzai Ranges), and the autochthonous Indian Plate margin (Kohat Basin). In our work we focused on establishing the sequence of tectonic events based on the emplacement of the Nappe Domain eastward on top of the other two domains. The rocks from each domain have been measured and logged to determine their stratigraphic differences. Nappe Domain consists of Jurassic and Cretaceous sequence of sedimentary mélange rocks which are intensely folded and faulted and emplaced on the other two domains. These mélange rocks are emplaced on the Eocene shales of Kohat Basin in the southern part of the research area, while the same mélange rocks overlie the Paleocene carbonates in the Orakzai Ranges. This variable emplacement of the mélange sequence signifies that the research area represents the confluence of tectonically distinct blocks which were far apart during the post-Cretaceous and later, from Late Eocene to Miocene, these blocks were juxtaposed under influence of regional faulting. Our research also proves that the emplacement of the mélange rocks from the west started in post-Paleocene in the northern Orakzai Ranges while the southern Kohat Basin was receiving extensive Eocene deposition which was later overlained by the mélange rocks. [ABSTRACT FROM AUTHOR]

Abstract: Along active margins, tectonic features that develop in response to plate convergence are strongly controlled by subduction zone geometry. In West Junggar, a segment of the giant Palaeozoic collage of Central Asia, the West Karamay Unit represents a Carboniferous accretionary complex composed of fore-arc sedimentary rocks and ophiolitic mélanges. The occurrence of quasi-synchronous upright folds and folds with vertical axes suggests that transpression plays a significant role in the tectonic evolution of the West Junggar. Latest Carboniferous (ca. 300Ma) alkaline plutons postdate this early phase of folding, which was synchronous with accretion of the Carboniferous complex. The Permian Dalabute sinistral fault overprints Carboniferous ductile shearing and split the West Karamay Unit ca. 100km apart. Oblique convergence may have been provoked by the buckling of the Kazakh orocline and relative rotations between its segments. Depending upon the shape of the convergence zone, either upright folds and fold with vertical axes, or alternatively, strike–slip brittle faults developed in response to strain partitioning. Sinistral brittle faulting may account for the lateral imbrication of units in the West Junggar accretionary complex. [Copyright &y& Elsevier]

Abstract: The 2004 Mid Niigta prefecture earthquake (MJMA 6.8) triggered more than one thousand landslides in the Miocene to Quaternary sedimentary rocks in Japan. The most common landslides were shallow disrupted landslides on steep slopes, which has been common in many previous disastrous earthquakes in the world. The Mid Niigta prefecture earthquake also triggered more than one hundred deep landslides, providing valuable information on the conditions for their occurrence. A field investigation and the interpretation of aerial photographs taken before and after the earthquake suggest that reactivation of existing landslides and undercutting of slopes are the most important factors for deep landslides to be triggered by earthquakes. In addition, planar sliding surfaces seem to be essential for the generation of catastrophic landslides triggered by this earthquake. Planar bedding–parallel sliding surfaces were formed at the boundary between the overlying permeable sandstone and underlying siltstone or along the bedding planes of alternating beds of sandstone and siltstone. Sliding surfaces along the slope-parallel oxidation front were formed in the area of black mudstone. New landslides (rockslide-avalanches) occurred with the sliding surfaces in a several-cm thick tuff interbedded in siltstone. One rockslide-avalanche occurred on a slope where buckling deformation preceded the earthquake. Gentle valley bottom sediments were mobilized in many locations, probably because they were saturated and partial liquefaction had occurred due to the earthquake shaking. [Copyright &y& Elsevier]

Terzaghi (Geotechnique 12 (1962) 251) and Young (Young, A., 1972. Slopes. Oliver and Boyd, Edinburgh, 288 pp.) described the stable forms of slopes in sedimentary rock masses, assuming penetrative discontinuities, which are parallel to bedding and joints which are perpendicular to bedding. The only movements considered were slides along bedding. Experience in the Canadian Rockies indicates that the cohesionless rock masses that exist at or above tree line may also move by toppling, buckling and sliding along joints. These processes also act to limit the inclinations of stable slopes. Rock strength is a factor in the critical height of a slope that buckles. The processes can be represented as fields on a process diagram, a plot of slope inclination against bedding dip, using the basic friction angles of the rocks present.The process diagram also separates five common mountain peak shapes, which form on homoclinal sequences of beds. Castellate and Matterhorn mountains occur in sub-horizontal beds, cuestas develop in gently to moderately dipping beds. Hogbacks formed in moderately to steeply dipping beds have similar slope angles on both cataclinal and anaclinal slopes. Dogtooth mountains occur in steeply dipping sub-vertical beds. [Copyright &y& Elsevier]

Deciphering the relationship between polyphase tectonic foliations and their associated mineral assemblages is significant in understanding the process from diagenesis to low‐/medium‐/high‐grade metamorphism. It can provide information related to strain, metamorphic conditions and overprinting relationships and so help reveal the tectonic evolution of orogenesis. In this study, we predominately focus on the formation of foliations and their related minerals, as developed in two separate basins. First of all, two stages of axial plane cleavages (S1 and S2) were recognized in the Hongyanjing inter‐arc basin, the formation of the S1 axial plane cleavage is associated with mica rotation and elongation in mudstones in the local area. The pencil structure of S2 formed during the refolding phase, the minerals in the sedimentary rocks not changing their shape and orientation. Secondly, in the Liao‐Ji backarc basin, foliations include diagenetic foliation (bedding parallel foliation), tectonic S1 foliation (secondary foliation or axial plane cleavage of S0 folding) and crenulation cleavage (S2). The formation mechanism of foliation changes from mineral rotation or elongation and mineral solution transfer in S1 to crystal‐plastic deformation, dynamic recrystallization and micro‐folding in S2. Many index metamorphic minerals formed from low‐grade to medium‐grade consist of biotites, garnets, staurolite and kyanite, constituting a typical Barrovian metamorphic belt. Accordingly, a new classification of foliation is presented in this study. The foliations can be divided into continuous and disjunctive foliations, based on the existence of microlithons, detectable with the aid of a microscope. Disjunctive foliation can be further sub‐divided into spaced foliation and crenulation cleavage, according to whether (or not) crenulation (micro‐folding) is present. The size of the mineral grains is also significant for classification of the foliations. [ABSTRACT FROM AUTHOR]

3D-printed (3DP) analogs of natural rocks have been used in laboratory tests concerning geomechanical and transport properties. Rock analogs manufactured by 3D printing can be used to manufacture batch of the samples with specified heterogeneity compared to natural rocks. Rock analogs were manufactured with silica sand (SS) and gypsum powder (GP) using binder jetting as well as with coated silica beads (CSB) using selective laser curing. The uniaxial and triaxial compressive tests were conducted to investigate the strength and deformation characteristics of 3DP rocks that were quantitatively compared with natural rocks. CSB and SS specimens experienced tensile failure, while the GP specimen has shown shear failure and shear-expansion behavior. The microstructural characteristics (e.g. grain shape, pore type, and bonding form) of the SS specimen were similar to a natural sandstone (Berea sandstone reported in the literature) with a relatively loose texture. In addition, 3DP rocks were more permeable than Berea sandstone (permeability of SS, CSB, and Berea sandstone was 12580.5 mD, 9840.5 mD, and 3950 mD, respectively). The effect of microscopic mechanical behavior on macroscopic strength and failure characteristics was investigated using scanning electronic microscopy. CSB and SS specimens could be suitable to simulate the transport behavior of the highly permeable sedimentary rocks. The GP specimen could be used to study the large deformation characteristics and creep failure mode of highly stressed soft rocks. Despite the early stage of 3DP rock analog studies, the potential applications could be expanded by controlling the physical properties (e.g. wettability and surface roughness). [ABSTRACT FROM AUTHOR]

The Gunung Kromong complex is a solitary hill which physiographically located within the Jakarta Coastal Plain Zone. The research is mainly formed of primary data from observations and measurements of all geological elements especially morphological aspects and geological structures to reveal the tectonic background and its relation to the oil seepage. Sedimentary rocks outcrops appear in the western part around the cement plant surrounded by well exposed of igneous rocks. Oil seepage, gas and hot springs are found in limestone which has high fracture intensity and at low elevation. The distribution of sedimentary rocks is not only controlled by the folds and fault structures but also influenced by the igneous rock intrusion. The alignment of the structure in West Palimanan is formed by steep slopes on dacite igneous rock which is concluded as fault scarp. There are found abundance of fault indications in the form of slickenside, fault breccias, millonites, drag folds and have high intensity of shear joint. The KRG-7, KRG-8 and KRG-9 observation points, a slickenside with the same plane was found but has different slicken line, each shows a thrust fault and normal faults. The direction of slickenside divided into 4 units of fault groups. The series of hills in the south of the Baribis Fault occur because of the lifting through the fold and the thrust faults mechanism. The thrust fault in the Gunung Kromong complex is the hanging wall section of the Baribis thrust fault, so that it belongs to the leading thrust system. [ABSTRACT FROM AUTHOR]

Mountain building in the Al-Hajar Mountains (NE Oman) occurred during two major shortening stages, related to the convergence between Africa–Arabia and Eurasia, separated by nearly 30 Ma of tectonic quiescence. Most of the shortening was accommodated during the Late Cretaceous, when northward subduction of the Neo-Tethys Ocean was followed by the ophiolites obduction on top of the former Mesozoic margin. This shortening event lasted until the latest Santonian – early Campanian. Maastrichtian to Eocene carbonates unconformably overlie the eroded nappes and seal the Cretaceous foredeep. These neo-autochthonous post-nappe sedimentary rocks were deformed, along with the underlying Cretaceous tectonic pile, during the second shortening event, itself including two main exhumation stages. In this study we combine remotely sensed structural data, seismic interpretation, field-based structural investigations and apatite (U–Th)/He (AHe) cooling ages to obtain new insights into the Cenozoic deformation stage. Seismic interpretation indicates the occurrence of a late Eocene flexural basin, later deformed by an Oligocene thrusting event, during which the post-nappe succession and the underlying Cretaceous nappes of the internal foredeep were uplifted. This stage was followed by folding of the post-nappe succession during the Miocene. AHe data from detrital siliciclastic deposits in the frontal area of the mountain chain provide cooling ages spanning from 17.3 to 42 Ma, consistent with available data for the structural culminations of Oman. Our work points out how renewal of flexural subsidence in the foredeep and uplift of the mountain belt were coeval processes, followed by layer-parallel shortening preceding final fold amplification. [ABSTRACT FROM AUTHOR]

Two impact experiments were carried out on blocks of Maggia gneiss to assess the influence of mechanical target anisotropies on the cratering process. The experiments were done within the framework of Multidisciplinary Experimental and Modeling Impact Research Network. In one experiment the metamorphic foliation was vertical, that is, oriented perpendicular to the target surface, and in the other horizontal, that is, parallel to the target surface. This study reveals that due to preferred spallation along the foliation, the cratering efficiency is higher if the foliation is horizontal. The study further presents a comprehensive quantitative strain analysis in the subsurface of these craters. We use biotite kink bands as strain markers. The distribution of strain differs strongly in both experiments. If the foliation is vertical, the area beneath the central crater floor shows a high compressive strain. This is attributed to the ability of biotite to kink more easily when shortened parallel to its basal plane. If the foliation is horizontal, surface kinking is reduced and tensile failure along the foliation deepens the crater during unloading. Key Points: Kinked bioites are appropriate strain markers to quantify the strain in the target rocksLayering in the target causes mechanical heterogeneity and affects the cratering processesOrientation of the layering with respect to the target surface affects the crater morphology and the distribution of strain in subsurface [ABSTRACT FROM AUTHOR]

The City of Pittsburgh, PA is located west of the Appalachian Mountains in the Appalachian Plateaus Province. The relatively flat surface of the plateau is dissected by drainage from the three principal rivers of the region, the Allegheny, Monongahela, and Ohio. The formation of Pittsburgh's three rivers and drainages has a long history dating back to before the Pleistocene Epoch, linked closely to the advance and retreat of continental glaciation. Western Pennsylvania is associated with the westernmost formation of the Appalachian Mountain chain with deformation in the form of a series of nearly flat-lying, gently warped Paleozoic sedimentary rocks. Rocks cropping out in the region range in age from Devonian to Permian. Pennsylvanian strata are dominated by thin cyclic sequences of sandstone, shale, claystone, coal, and limestone. Most of the geologic hazards present in the region include slope instability, expansive shales and slags, mine subsidence, acid mine drainage, pyritic acid rock and flooding. The region also has an abundance of natural resources including coal, natural gas, oil, salt, limestone, sand and gravel and water. Pittsburgh's strategic location helped shape westward expansion during the formation of the Nation, largely because of the rivers, which served as an inexpensive, yet efficient means of transportation. Infrastructure was always significant in Pittsburgh. However, the existing aging infrastructure are deteriorating. Today, Pittsburgh has transcended the legacy name, "Steel City" and has revitalized itself with nationally-recognized universities and medical centers and a resurgence in natural gas exploration. However, many environmental legacy issues still burden the area. [ABSTRACT FROM AUTHOR]

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Magnetic fabric allows to unravel the petrofabrics of sedimentary rocks and to assess their deformational history. The use of this technique, in addition to classical structural field observations in the limbs of seven asymmetric folds in the Pyrenees, helps to determine the differences of internal deformation as well as the folding kinematics. Three folds developed during the Variscan Orogeny in Ordovician and Devonian rocks, and four folds developed during the Pyrenean Orogeny in Eocene rocks, are studied. Folds show a variety of structural locations, in different thrust sheets of the Southern Central Pyrenees, different cleavage development, age, geometry and lithology. Sampling follows an equivalent lithological layer in the two limbs, except for one case, of the selected folds. Results show a modified tectonic magnetic fabric in most sites with the magnetic lineation on the tectonic foliation plane. A larger scattering of the magnetic lineation (maximum magnetic anisotropy axis) and a higher intensity of the preferred orientation of minerals (eccentricity of the anisotropy of magnetic susceptibility - AMS ellipsoid) is better observed in the overturned (short) limb of the asymmetric Variscan folds than in the normal (long) limb. On the other hand, the shape parameter in Alpine folds is generally larger in the overturned (short) limb then in the normal (long) one. A good clustering of the minimum magnetic anisotropy axes is observed in all limbs. The combination of the AMS data with the structural data helps to understand and better constrain the deformation degree in these asymmetric folds and to unravel the deformational history. [ABSTRACT FROM AUTHOR]

The Rio Pardo salient, the large antitaxial curve described by the Araçuaí fold-and-thrust belt along the southeastern edge of the São Francisco craton, is one of the most prominent and one of the least studied features of the Brasiliano Araçuaí-West Congo orogenic system (AWCO). In addition to the Archean/Paleoproterozoic basement, the salient is comprised of metasedimentary rocks mainly from the Neoproterozoic Macaúbas Group and the Salinas Formation. Its western limb occupies a portion of the Espinhaço ridge, where the NS-trending structures of the Araçuaí belt progressively curve NE and E, thereby defining the hinge zone along the Serra Geral on the Minas-Bahia boundary. The eastern limb is NW-trending and marked by a major shear zone. In models postulated to generate the AWCO through the closure of the Neoproterozoic Macaúbas basin, this large curve plays a critical kinematic role. Yet, in spite of this, its development is still not fully understood. How did this curve originate? Which factors controlled its generation? Our field study performed in the northern Araçuaí orogen characterized the kinematic picture of the salient, and led to a model that addresses these questions. The results we obtained indicate that the Rio Pardo salient developed in response to four deformation phases. The contractional D1 and D2 phases are coaxial and responsible for a craton-directed tectonic transport along the salient's outer arc, which is coupled with an overall southward motion of the inner arc, thereby giving rise to a rather complex kinematic picture. Furthermore, structures of the D1/D2 phases define a zigzag pattern with alternating NE- and NW-trending segments along the salient's leading edge. Along the NE-trending segments, the metasedimentary rocks are thrust northwestwards on top of the craton basement, while along the NW-trending segments, the supracrustal rocks are displaced along dextral to reverse-dextral transpressional shear zones located on the basement/cover contact. Structures of the D3 phase, which are well developed in the hinge zone, record a final WSW-ENE contraction, which was responsible for rotation of the preexistent fabric elements around NNW-trending axes and the enhancement of the salient curvature. The D4 phase is extensional and is recorded by two large-scale structures, the Chapada Acauã and Tingui normal shear zones, as well as by the normal-sinistral reactivation of the Itapebi strike-slip shear zone that marks the salient eastern limb. We interpret the initiation of the Rio Pardo salient during the collisional 565-575 Ma D1/D2 phases essentially as a primary arc that is mainly controlled by the geometry of the Macaúbas precursor basin. The thickened internal portion of the Rio Pardo salient was affected by extensional tectonism at c. 530 Ma, and is recorded by the D4 deformation phase, which is currently ascribed to the extensional collapse of the Araçuaí-West Congo orogen. [ABSTRACT FROM AUTHOR]

Sedimentary basins in the interior of orogenic plateaus can provide unique insights into the early history of plateau evolution and related geodynamic processes. The northern sectors of the Iranian Plateau of the Arabia-Eurasia collision zone offer the unique possibility to study middle-late Miocene terrestrial clastic and volcaniclastic sediments that allow assessing the nascent stages of collisional plateau formation. In particular, these sedimentary archives allow investigating several debated and poorly understood issues associated with the long-term evolution of the Iranian Plateau, including the regional spatio-temporal characteristics of sedimentation and deformation and the mechanisms of plateau growth. We document that middle-late Miocene crustal shortening and thickening processes led to the growth of a basement-cored range (Takab Range Complex) in the interior of the plateau. This triggered the development of a foreland-basin (Great Pari Basin) to the east between 16.5 and 10.7 Ma. By 10.7 Ma, a fast progradation of conglomerates over the foreland strata occurred, most likely during a decrease in flexural subsidence triggered by rock uplift along an intraforeland basement-cored range (Mahneshan Range Complex). This was in turn followed by the final incorporation of the foreland deposits into the orogenic system and ensuing compartmentalization of the formerly contiguous foreland into several intermontane basins. Overall, our data suggest that shortening and thickening processes led to the outward and vertical growth of the northern sectors of the Iranian Plateau starting from the middle Miocene. This implies that mantle-flow processes may have had a limited contribution toward building the Iranian Plateau in NW Iran. [ABSTRACT FROM AUTHOR]

Brittle basement and sedimentary rocks, in particular if these are underlain by radiogenic crust, are considered a prime target for enhanced geothermal systems (EGS). They are marked by high geothermal gradients, caused by radiogenic heat production, and are well suited to be used for geothermal doublets after hydraulic stimulation. Critical conditions for successful EGS projects are: (a) tectonic stresses close to failure, allowing creation of induced fractures by means of hydraulic stimulation; (b) sufficient high temperatures >150 °C, preferably in excess of 200 °C, at depths of less than 5 km; (c) sufficient high water flow rates, to be sustained through induced fractures. For geothermal production, knowledge on thermo-mechanical properties of the lithosphere provides critical constraints on crustal stresses and basement temperatures. We developed a freely available 1D thermal and rheological model for basement-sedimentary areas. This tool helps to understand variability of deep temperatures, as an effect of uncertainties in thermal and rheological properties and tectonic constraints for the lithosphere, important for assessing geothermal prospectivity. The tool is demonstrated on the Central System in Spain and the adjacent Tajo and Duero basins. [ABSTRACT FROM AUTHOR]

The cohesive-frictional nature of cementitious geomaterials raises great interest in the discrete element method (DEM) simulation of their mechanical behavior, where a proper bond failure criterion is usually required. In this paper, the failure of bond material between two spheres was investigated numerically using DEM that can easily reproduce the failure process of brittle material. In the DEM simulations, a bonded-grain system (composed of two particles and bond material in between) was discretized as a cylindrical assembly of very fine particles connecting two large end spheres. Then, the bonded-grain system was subjected to compression/tension, shear, rolling and torsion loadings and their combinations until overall failure (peak state) was reached. Bonded-grain systems with various sizes were employed to investigate bond geometry effects. The numerical results show that the compression strength is highly affected by bond geometry, with the tensile strength being dependent to a lesser degree. The shear, rolling and torsion strengths are all normal force dependent; i.e., with an increase in the normal force, these strengths first increase at a declining rate and then start to decrease upon the normal force exceeding a critical value. The combined actions of shear force, rolling moment and torque lead to a spherical failure envelope in a normalized loading space. The fitted bond geometry factors and bond failure envelopes obtained numerically in this three-dimensional study are qualitatively consistent with those in previous two-dimensional experiments. The obtained bond failure criterion can be incorporated into a future bond contact model. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Ediacaran and Early Cambrian sedimentary rocks from NW Iberia have been investigated for detrital zircon U-Pb ages. A total of 1,161 concordant U-Pb ages were obtained in zircons separated from four Ediacaran samples (3 from the Cantabrian Zone and one from the Central Iberian zone) and two Lower Cambrian samples (one from the Cantabrian Zone and one from the Central Iberian Zone). Major and trace elements including REE and Sm-Nd isotopes were also analyzed on the same set of samples. The stratigraphically older Ediacaran sequence in the Cantabrian Zone has a maximum sedimentation age of ca. 600 Ma based on detrital zircon content and is intruded by ca. 590-580 Ma granitoids constraining the deposition of this part of the sequence between ca. 600 and 580 Ma. The stratigraphically younger Ediacaran sequence in the Cantabrian Zone has a maximum sedimentation age of ca. 553 Ma. The Ediacaran sample from the Central Iberian Zone has an identical within error maximum sedimentation age of ca. 555 Ma. The detrital zircon U-Pb age patterns are very similar in all the Ediacaran samples from both zones including the main age groups ca. 0.55-0.75 Ga, ca. 0.85-1.15 Ga and minor Paleoproterozoic (ca. 1.9-2.1 Ga) and Archean (ca. 2.4-2.6 Ga) populations. Kolmogorov-Smirnov statistical tests performed on this set of samples indicate that they all were derived from the same parent population (i.e., same source area). The same can be said on the basis of Nd isotopes, REE patterns and trace element concentrations. The two Cambrian samples, however, show contrasting signatures: The sample from the Cantabrian Zone lacks the ca. 0.85-1.15 Ga population and has a high proportion of Paleoproterozoic and Archean zircons (>60 %) and a more negative ε and higher T values than the Ediacaran samples. The Early Cambrian sample from the Central Iberian Zone has the same U-Pb detrital zircon age distribution (based on KS tests) as all the Ediacaran samples but has a significantly more negative ε value. These data suggest apparently continuous sedimentation in the NW Iberian realm of northern Gondwana between ca. 600 and 550 Ma and changes in the detrital influx around the Ediacaran-Cambrian boundary. The nature and origin of these changes cannot be determined with available data, but they must involve tectonic activity on the margin as evidenced by the angular unconformity separating the Ediacaran and Lower Cambrian strata in the Cantabrian Zone. The absence of this unconformity and the apparent continuity of detrital zircon age distribution between Ediacaran and Cambrian rocks in the Central Iberian Zone suggest that the margin became segmented with significant transport and sedimentation flux changes in relatively short distances. As to the paleoposition of NW Iberia in Ediacaran-Early Cambrian times, comparison of the data presented herein with a wealth of relevant data from the literature both on the European peri-Gondwanan terranes and on the terranes of northern Africa suggests that NW Iberia may have lain closer to the present-day Egypt-Israel-Jordan area and that the potential source of the hitherto enigmatic Tonian-Stenian zircons could be traced to exposed segments of arc terranes such as that described in the Sinai Peninsula (Be'eri-Shlevin et al. in Geology 40:403-406, ). [ABSTRACT FROM AUTHOR]

This manuscript outlines the different sedimentary deposits that characterise the Tavoliere di Puglia plain (the second largest Italian plain). The plain is largely covered by Quaternary terrace deposits that unconformably lie on older deposits, most commonly the argille subappennine unit. The outcropping units have been divided into categories of descending rank: the first subdivision is made on the basis of geological domain; within each domain a subdivision of lower rank is based on age; within each age a further subdivision is based on the nature of the sediments. The main map presents an updated synthesis of the geology and geomorphology of the Tavoliere di Puglia plain and provides a firm foundation for further, more detailed studies. [ABSTRACT FROM AUTHOR]

Potash, a fertiliser currently in demand worldwide, lies beneath beds of salt and other evaporites deep within the ground. The ground support challenge encountered when excavating through these strata is that of time dependent (creep) deformation control. The deformation is radial, causing the shaft excavation to close up over time, eventually loading the permanent lining with the full geostatic pressure and causing lining failure. In order to achieve a significant design life for an economical shaft lining in creeping rocksalt strata, a deformation zone filled with a compressible material is employed between the excavation and permanent lining. This helps resist the ground pressure, and reduce the magnitude and velocity of creep deformation. Optimum lining designs have been developed by predicting the creep deformation at a given time and by considering the behaviour of different compressible materials available to fill the deformation zone. Foamed concrete is the favoured material for an intermediate compressible lining. [ABSTRACT FROM AUTHOR]

The Late Neoproterozoic Ediacara Member of the Rawnsley Quartzite in South Australia has been considered aeolian, fluvial, intertidal and deep marine by various authors. Palaeosols would not be expected for the deep marine interpretation, but some palaeosols should be evident for the aeolian-fluvial-intertidal interpretations, and this is the first study to examine the Ediacara Member at a petrographic and geochemical scale appropriate to recognize potential palaeosols. Recognition of palaeosols and floodplain facies in Neoproterozoic rocks is a challenge because such rocks are too ancient for diagnostic non-marine fossils such as root traces. The varied thickness of Ediacara Member red siltstones and white sandstones is distinct from laterally persistent overlying and underlying grey shales and limestones with acritarchs, stromatolites and other marine fossils. The sandstones are trough cross-bedded and fill palaeovalleys. The red siltstones have poorly sorted, highly angular, silt-size grains characteristic of loess. Particular sandy and silty beds were sampled for detailed petrographic and geochemical studies, because they include desiccation cracks, sand crystals, ice cracks, carbonate nodules and soft-sediment deformation like those of palaeosols. Chemical and grain-size variations within these beds reveal surficial clay formation and oxidation from feldspar as in soils. Petrographic studies also revealed surficial disruption of these palaeosols by filamentous structures comparable with microbial ropes of biological soil crusts. This array of palaeosol features may be of use for recognizing palaeosols in other Neoproterozoic siliciclastic sequences. [ABSTRACT FROM AUTHOR]

The Songliao Basin is a large Mesozoic nonmarine petroliferous basin in northeastern China. Based on an analysis of high-resolution three-dimensional seismic data, a large-scale lacustrine turbidite channel and fan system is identified within the lacustrine mudstone of the Nenjiang Formation in the central depression. The system was fed by a delta complex and extends to the south along the Daqing anticline. This system is composed of three trunk channels and four tributary channels, with a maximum length of about 71 km. Changes in channel patterns, specifically bifurcations and terminations into fans, are associated with gradient changes along the palaeoslope, which vary from 0.13 to 0.02°. Interpretation of geophysical well logs and core indicate that channel sand bodies are oil charged. The widest channel sandstone body is about 600 m with an average around 300 m, and the maximum thickness of sandstone is more than 6 m with an average of about 3 m. The sandstone bodies of the turbidite system, which are encased within organic-rich source rocks, provide a new target for hydrocarbon exploration and development. [ABSTRACT FROM AUTHOR]

Geological structure of the active foreland fold and thrust belt of Papua New Guinea has been interpreted using high-quality seismic-reflection data. Three en echelon anticlines, the Strickland, Cecilia and Wai Asi, are located along the frontal margin of the Papuan Fold Belt. All three are foreland-vergent and cut by hinterland-dipping thrust faults that sole into a common detachment beneath the Oligocene to Miocene Darai Limestone. Two of the anticlines are linked by a right-lateral transfer zone. Folding occurs primarily in the upper 2000 m of strata, which consist of Darai Limestone overlain by Miocene to Quaternary siliciclastic sedimentary rocks. Beneath the Darai Limestone lies the less-competent shaly Ieru Formation, which exhibits disharmonic folding and variable bed thickness. Seismic-reflection data clearly show that the Plio-Pleistocene upper Era Beds are deformed to the same extent as the underlying Darai Limestone, demonstrating that most of the observed deformation has occurred during the Late Pliocene and Pleistocene. [ABSTRACT FROM AUTHOR]

40Ar/39Ar dating of slate and phyllite in the Nambucca Block, southern New England Orogen, indicates that deformation took place between 264 and 260 Ma. These data further show that indentation of the Early Permian turbidite successions by the southward-moving Coffs Harbour Orocline ceased at this time. Folding of the Sakmarian to Sarginian sequences in the Silver Spur Basin (294.6 - 275.6 Ma) during the megafolding event constrains the formation of the Texas Orocline to be post-ca 276 Ma. The presence of brachiopod faunas indicates that orocline formation commenced in the early Kungurian (ca 273 Ma) during the early stages of the Hunter - Bowen Orogeny. Thus, development of the Texas and Coffs Harbour Oroclines took place within a period of 13 million years, from 273 to 260 Ma. Oblique convergence is believed to be responsible for the formation of the Texas and Coffs Harbour Oroclines and associated constrictional structures during the Hunter - Bowen Orogeny. Slip on a dextral, strike-slip fault formed during convergence, buckled and rotated the meridional-trending arc - forearc - subduction complex to form north-northwest-trending, Z-shaped megafolds. [ABSTRACT FROM AUTHOR]

The term ‘cap carbonate’ is commonly used to describe carbonate units associated with glacigenic deposits in Neoproterozoic successions. Attempts to use carbonate units as stratigraphic markers have been counfounded by inconsistent identification of ‘cap carbonates’ and a somewhat broad use of the term. Systematic sedimentological and geochemical analysis of carbonate rocks (mostly dolomite) associated with glacigenic deposits from the Neoproterozoic succession of the Kimberley region, north-western Australia, shows that it is possible to characterize such units by their specific mineralogical, sedimentological, petrographic, geochemical and stratigraphic features. Hence, it is possible to differentiate true ‘cap carbonates’ from other carbonate units that are associated with glacigenic deposits. In the Kimberley successions two broad carbonate types are identified that reflect two stratigraphically distinct depositional realms. Carbonate rocks from the Egan Formation and Boonall Dolomite (the youngest carbonate units in the succession) are characterized by sedimentary components and features that are consistent with deposition on shallow platforms or shelves, analogous to Phanerozoic warm-water carbonate platform deposits. In contrast, dolomite from the Walsh, Landrigan and Moonlight Valley Tillites preserves a suite of sedimentary and geochemical characteristics that are distinctly different from Phanerozoic-like carbonate rocks; they are thin ( ca 6 m), laterally persistent units of thinly laminated dolomicrite/dolomicrospar recording δ13C fluctuations from −1‰ to −5‰. These latter features are consistent with a ‘Marinoan-style cap-carbonate’ rock described from other Neoproterozoic successions. The similarity and broad distribution of these rocks in Australia, when considered within the context of genetic models suggesting a global oceanographic–atmospheric event, support their use as a lithostratigraphic marker horizon for the start of the Ediacaran Period at ca 635 Ma. [ABSTRACT FROM AUTHOR]

Strain reversal of structural/stratigraphic profiles at different scales in the western Lachlan Orogen provides a perspective on original crustal thickness estimates, the former depositional basin width of the proto-western Lachlan Orogen, the original sedimentary-fan thickness, and the possible length extent of lower crust lost by subduction. Retrodeformation using strain-reversal techniques allows basin reconstruction giving an original width of the western Lachlan Orogen basin receptor of between 800 km (minimum) and ∼⃒1150 km (maximum), depending on the amount of stratal duplication allowed in the turbidites. Crude area balancing of the regional cross-section, adding in sectional volume lost by erosion and assuming strain compatibility between the upper and lower crust, suggests that the predeformation crustal thickness ranges between 15 km and ∼⃒21 km, with a lower crustal thickness (oceanic lithosphere) of ∼⃒9 km and a turbidite fan thickness of ∼⃒6 km (minimum) and ∼⃒12 km (maximum allowable), respectively. Disparity between the calculated fan thickness and that derived from measured stratigraphic sections adjusted for strain (∼⃒6 km) indicates that some form of crustal stacking must be important in structural thickening of the turbidite crustal component. By varying shortening due to fault stacking, mass balance dictates the mismatch of the upper crustal (uc) and lower crustal (lc) retrodeformed lengths, and therefore provides an estimate of lower crustal loss by subduction. End members range from: (i) a 12 km-thick fan without fault duplication, a basin width of ∼⃒800 km where uc = lc giving no lower crustal loss by subduction; to (ii) a ∼⃒6 km fan, requiring duplication by faulting, a basin of ∼⃒1150 km where uc > lc, and ∼⃒360 km of lower crust length (∼⃒30%) lost by subduction. This suggests that the total thickness of underplated igneous material in the western Lachlan Orogen is low, probably [ABSTRACT FROM AUTHOR]

Abstract We carried out paleomagnetic measurements and K–Ar dating on Neogene andesitic lavas and sills of the Shigarami Formation in North Fossa Magna, central Japan. The Shigarami Formation is distributed in the axial part of the Komiji Syncline in the folding zone of the southwestern North Fossa Magna. Results of the present study indicate that the Komiji Syncline was formed shortly after 4.42 ± 0.12 Ma during the Pliocene. The sedimentary rocks of the Shigarami Formation consist of shallow marine and fluvial deposits. Intrusions of andesitic sills are found in the shallow marine deposits and two andesitic lava flows are present in the fluvial deposits. Oriented samples were taken from the sills at four sites and from the lavas at three sites. The samples produced stable remanent magnetization through stepwise alternating field and thermal demagnetizations. Results of a positive fold test indicate that the stable remanent magnetizations concentrate around a mean reversed polarity of declination = 169.0°, inclination = -58.5° and 95% confidence limit = 9.0° after corrections have been made according to the direction of the bedding of the sedimentary rocks. Four fresh samples were selected for K–Ar dating from the samples used for paleomagnetic measurements. The groundmass of three samples taken from the sills yield ages of 4.42 ± 0.12, 4.49 ± 0.22 and 4.69 ± 0.13 Ma, whereas the one taken from the lower lava has an age of 5.91 ± 0.26 Ma. We believe that the Komiji Syncline was formed after the emplacement of lavas and sills in the area, because the descending Miocene strata were folded concordantly with the Shigarami Formation. The Pliocene and Pleistocene strata rest unconformably on the folded strata. The deformation might have progressed during the Pliocene, then slowed down in the Early Pleistocene. Our results suggest that the northwestward motion of the Philippine Sea Plate and the collision of the Tanzawa Block affected not only the South Fossa Magna, but also the North Fossa Magna. [ABSTRACT FROM AUTHOR]

This paper presents a time-dependent constitutive model that has been developed for the swelling of shaly rocks. Laboratory test results on many shales, including Queenston shale, show that the swelling of these rocks depends on the applied stresses. The applied stress in one principal stress direction reduces swelling strain not only in that direction but also in the perpendicular directions. It was found that swelling strain reductions are nonlinearly dependent on applied stress. The reduction in lateral swelling caused as a result of axial stress is modeled using the "pseudo-Poisson's effect". The proposed model is used to simulate the development of swelling strain with time under uniaxial and biaxial stress conditions. Comparison between the computed and experimental results shows that the pseudo-Poisson's effect is a key parameter for simulating the observed time-dependent swelling. [ABSTRACT FROM AUTHOR]

Three main kinds of syndepositional deformation are found in cross-bedded sand-grade .sediments. The first type is characterized by simple recumbent folds of broadly parabolic form. The second is marked by series of folds, with or without overturning. The third type is much more complex, presenting a combination of faulting, folding, and the local destruction of bedding. The type marked by recumbent folds is interpreted as due to the deformation of a liquefied for perhaps fluidized) sand by current drag following an event in the majority of cases suspected to be an earthquake shock. By reference to empirical and theoretical studies of sedimenting systems, and the behaviour under small shear stresses of liquids of high viscosity, this physical model is developed analytically to yield equations describing the geometry of the deformations in terms of the thickness of the deformed bed, the settling velocity and concentration of particles in the liquefied sand, the viscosity of the liquefied sand, and the magnitude of the deforming force. The equations describe a fold surface that is a portion of a flat-lying parabola, and show that the proposed circumstances of deformation are plausible in terms of what is known of the real situation. They further reveal that, under the assumptions made in the analysis, the vertical height of the fold hinge above the base of the bed is a function only of the initial shape of the deformed cross-stratum, the shear rate in the liquefied materials, and the falling velocity and concentration of particles in the liquefied bed. The shapes of deformations calculated from the equations agree well with patterns observed from the geological record. [ABSTRACT FROM AUTHOR]

The 1963 Vajont landslide is a reference example of large rockslides involving clay interbeds emplaced in sedimentary rock masses in correspondence with the basal rupture zone (thinly stratified cherty limestone of the Fonzaso Formation dated to Middle–Upper Jurassic). The basal shear zone of the 1963 Vajont landslide was made up of a chaotic assemblage of displaced rock masses, limestone angular gravel, and spread clay lenses. The mineralogical investigations showed that the clays are characterized by complex assemblages of illite/smectite mixed layers (36–96%) admixed with variable amounts of calcite (4–64%) and quartz (0–6%). The clay layers show highly variable plasticity properties and shear strength characteristics. The samples with a large prevalence of clay mineral content (CM) (CM > 79%) are characterized by low values of the residual friction angle (6.7–14.9°), whereas clay materials characterized by a higher content of granular minerals (calcite and quartz) clearly show greater friction angle values (19.5–26.7°). The high permeability of the limestone angular gravel, which caused a rapid reservoir-induced inflow (1960–1963), together with the low friction angle of the clay layers were responsible for the overall shear strength reduction in correspondence with the basal rupture zone, thus favoring the huge sliding on 9 October 1963. [ABSTRACT FROM AUTHOR]