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Ground-penetrating radar (GPR) faces complex challenges in identifying underground rock formations and lithological structures. The diversity, intricate shapes, and electromagnetic properties of subsurface rock formations make their accurate detection difficult. Additionally, the heterogeneity of subsurface media, signal scattering, and non-linear propagation effects contribute to the complexity of signal interpretation. To address these challenges, this study fully considers the unique advantages of convolutional neural networks (CNNs) in accurately identifying underground rock formations and lithological structures, particularly their powerful feature extraction capabilities. Deep learning models possess the ability to automatically extract complex signal features from radar data, while also demonstrating excellent generalization performance, enabling them to handle data from various geological conditions. Moreover, deep learning can efficiently process large-scale data, thereby improving the accuracy and efficiency of identification. In our research, we utilized deep neural networks to process GPR signals, using radar images as inputs and generating structure-related information associated with rock formations and lithological structures as outputs. Through training and learning, we successfully established an effective mapping relationship between radar images and lithological label signals. The results from synthetic data indicate a rock block identification success rate exceeding 88%, with a satisfactory continuity identification of lithological structures. Transferring the network to measured data, the trained model exhibits excellent performance in predicting data collected from the field, further enhancing the geological interpretation and analysis. Therefore, through the results obtained from synthetic and measured data, we can demonstrate the effectiveness and feasibility of this research method. [ABSTRACT FROM AUTHOR]

Ground-penetrating radar (GPR) faces complex challenges in identifying underground rock formations and lithological structures. The diversity, intricate shapes, and electromagnetic properties of subsurface rock formations make their accurate detection difficult. Additionally, the heterogeneity of subsurface media, signal scattering, and non-linear propagation effects contribute to the complexity of signal interpretation. To address these challenges, this study fully considers the unique advantages of convolutional neural networks (CNNs) in accurately identifying underground rock formations and lithological structures, particularly their powerful feature extraction capabilities. Deep learning models possess the ability to automatically extract complex signal features from radar data, while also demonstrating excellent generalization performance, enabling them to handle data from various geological conditions. Moreover, deep learning can efficiently process large-scale data, thereby improving the accuracy and efficiency of identification. In our research, we utilized deep neural networks to process GPR signals, using radar images as inputs and generating structure-related information associated with rock formations and lithological structures as outputs. Through training and learning, we successfully established an effective mapping relationship between radar images and lithological label signals. The results from synthetic data indicate a rock block identification success rate exceeding 88%, with a satisfactory continuity identification of lithological structures. Transferring the network to measured data, the trained model exhibits excellent performance in predicting data collected from the field, further enhancing the geological interpretation and analysis. Therefore, through the results obtained from synthetic and measured data, we can demonstrate the effectiveness and feasibility of this research method.

Background. To reveal the possibilities of using the life strategy of cyanobacterial- algal groups in the development of extreme habitats as an indicator of the course of different types of primary xeropesammo-lithophilic successions. Materials and methods. The collection of samples were carried out according to the generally accepted algological method. Results. The floristic analysis revealed 4 divisions, 11 classes, 15 orders, 29 families, 47 genera and 78 species. As expected, cyanobacterial occupy the first place on all substrates (60 % of all flora). At the species level, the coefficients of similarity and inclusion measures showed a weak degree of affinity between the floras of the studied substrates. The indicators of the degree of formation of these formations are the spectra of dominants, their abundance, and spectra of morphotypes, ccurrence of species, phytocenotic load and other indicators. It was revealed that about 23 % of the flora are dominants, but they are quite substrate-specific. It is noted that at the initial stages of development, the dispersed distribution of algae and cyanobacteria prevails. With the appearance of lichens and even more so mosses, the distribution of algae becomes “aggregating”. For each type of substrate, its own model of development and formation of probiogeocenosisis built. Conclusions. The process of primary development of rocks and sandy soil (loose and overburden sands) by cyanobacterial-algal flora in different regions of Russia: Northeast of Asian Russia and Western Siberia is described. The specificity of the course of primary successions has been clarified, different models of the course of successions have been established, which will make it possible to judge the life strategies and the different nature of the phytocenotic organization of cyanobacterial-algal groups, as the initial stage of the formation of probiogeocenoses in the outer habitats.

The main functions of a three-dimensional test device for simulating rock formations and surface movement affected by underground coal mining were described in detail, and a series of similar related tests were carried out. The device consisted of an outer frame, a pressurization unit, a pulling unit, and a coal seam simulation portion. Using this test device, supported by monitoring methods such as the three-dimensional laser scanner method, a model test study on the surface subsidence characteristics caused by coal seam mining was carried out. Combined with the field measurements, the transfer law of surface subsidence caused by coal seam mining was revealed, and the whole surface subsidence response process was analyzed. The experimental results show that the subsidence caused by mining disturbances below the coal seam accounts for 79.3% of the total subsidence, which is the dominant factor of the total surface subsidence. After long-term surface observations, surface subsidence can be divided into four stages after coal mining, and the settlement value of the obvious settlement stage accounts for more than 60% of the total settlement value. The above test results fully reflect the feasibility and practicality of the three-dimensional test device to simulate rock strata and surface movement and provide a new experimental research tool that can be used to further study the surface subsidence characteristics and control caused by coal mining.

The methods of undulatory transillumination found extensive application in engineering and mining practice. They are based on utilization of the parameters of reflected and transmitted waves produced by way of affecting solid materials and formations with diverse sources. In recent years a simplistic technique of the productive-process robust designing enjoys widespread occurrence. It uses notions of ‘signal’ and ‘noise’ and a tenth part of the logarithm value of the reciprocal magnitude of the dispersion squared value corresponds the ratio of the signal and the noise. The article utilizes the confidence boundaries evaluation techniques for dispersion in robust design on chi-square criterion at small sample specified by K. A. Brownly under editorial of academician А. N. Kholmogorov, which essentially increases reliability of the stochastic estimations.Exemplarily of quantitative assessment in the reliability determination of anomalous zones in mining conditions, the author shows the tracing of a map of the formation graph of regular components of the elastic wave field at seismal transillumination along the layerage of the soliferous rocks of lower industrial pad III of potash horizon of the Starobinski minefield. The article claims the feasibility of the offered technique for stochastic estimation of the measurement results of any process where it is necessary to evaluate the reliability of the signal extraction against the noise background. A simple conditional scale built on basis of time and noise level values taken as a unit is convenient to use. The presented alignment chart and graphical dependencies allow quickly appraise the realization probability of the signalto-noise relation and possibility of its rise. Thereat the obtained evaluations depend little on the probable magnitudes distribution form of the employed value.

The aim of this work is to study the spatial dynamic of wave propagation in rock formations, taking into account ravines and caverns. The dynamics of the seismic and acoustic waves generated by explosions of different types is investigated using seismograms measured by several reception lines. The research uses the numerical experiments using the full-wave joint simulation of acoustic and seismic wave propagation in heterogeneous mixed acoustic and linear-elastic media. The grid-characteristic method is used to obtain the mathematically and physically correct description of spatial dynamic wave processes taking the boundary and contact surfaces, including the interfaces between the linearelastic and the acoustic environments, into consideration. The influence of the type of explosion on the spatial dynamic wave patterns and seismograms is analyzed for the cases of horizontal and vertical reception lines. The dependences of spatial dynamic wave patterns and seismograms recorded by the horizontal and vertical reception lines on the distance of the karst caverns from the ravine are studied. The basic types of waves that different types of explosions generate in the rock formations, ravines, and caverns are investigated. The basic laws that characterize the emerging wave patterns and their influence on seismograms are found. [ABSTRACT FROM AUTHOR]

The Mine Waste Directive (2006/21/EC) requires the risk-based inventory of all mine waste sites in Europe. The geochemical documentation concerning inert classification and ranking of the mine wastes requires specific field study and laboratory testing and analyses of waste material to assess the Acid Mine Drainage potential and toxic element mobility. The procedure applied in this study used a multi-level decision support scheme for the inert classification of waste rock material including: 1) expert judgment, 2) data review, 3) representative field sampling and laboratory analysis and testing of rock formations listed in the National Inert Mining Waste List, and 4) requesting available laboratory analysis data from selected operating mines. Based on a preliminary expert judgment, the listed formations were classified into three categories. A: inert B: probably inert, but has to be checked, C: probably not inert, has to be examined. This paper discusses the heavy metal contamination risk assessment (RA) in the Hungarian quarrymine waste sites. In total 30 waste sites (including both abandoned mines and active quarries) were selected for scientific testing using the EU Pre-selection Protocol. Altogether 93 field samples were collected from the waste sites including andesite, rhyolite, coal (lignite and black coals), peat, alginite, bauxite, clay and limestone. Laboratory analyses of the total toxic element content (aqua regia extraction), the mobile toxic element content (deionized water leaching) carried out according to the Hungarian GKM Decree No. 14/2008. (IV.3) concerning mining waste management. A detailed geochemical study together with spatial analysis and GIS were performed to derive a geochemically sound contamination RA of the mine waste sites. Key parameters such as heavy metals, in addition to the landscape metric parameter such as the distance to the nearest surface and ground water bodies, or to sensitive receptors such as settlements and protected areas calculated and statistically evaluated in order to calibrate the RA methods. Results show that some of the waste rock materials, assumed to be inert, were found non-inert. Thus, regional RA needs more spatial and petrological examination with special care to rock and mineral deposit genetics.

Rock fragmentation is considered to be one of the most important aspects of quarrying because of its direct effect on the costsof drilling, which include blasting, loading, hauling and crushing. Thus, it is essential to consider fragmentation size in blasting design.Fragmentation depends on many variables, such as rock properties, geological structures, and blasting parameters. Although empiricalmodels for the estimation of the size distribution of rock fragmentation have been developed by considering these parameters,no complete empirical prediction model for fragmentation exists since rock properties and geological structures vary from site to site.However, these models regard rock properties as constant. In this study, a step–wise multiple linear regression analysis has beencarried out to determine the degree of dominance of various influencing parameters on fragmentation and to develop a fragmentationprediction model. The results showed that the rock mass properties, burden width and specific charge are the main parameters affectingfragmentation. The relations among those parameters were used to develop guideline charts to determine blast layouts for desiredfragmentation on the basis of rock characteristics.

Rock formations are among the most spectacular landscape features both for experts and the public. However, information about these objects is often stored inaccurately in existing spatial databases, their corresponding elevations are missing, or the entire rock object is completely absent. Cartographic depiction is also reduced to a point of areal symbology of a largely generalized character. This paper discusses options in identifying and analyzing rock formations from two digital terrain models (DTMs), DMR 5G and DMR 5G+, and irregularly spaced points of airborne laser-scanning (ALS) data with different point densities. A semi-automatic method allowing rock formations to be identified from DTMs is introduced at the beginning of the paper. A method to evaluate elevation models (volume differences) is subsequently applied and a 3D model of a selected rock object is created from terrestrial laser-scanning data. Finally, positional and volumetric comparisons of that 3D object are performed in 2D, 2.5D, and 3D. The results of the pilot study confirmed that the digital terrain models studied are a reliable source in identifying and updating rock formations using the semi-automatic method introduced. The results show that DMR 5G model quality decreases with increasing fragmentation and relative rock formation height, while the proportion of gross errors increases. The complementary DMR 5G+ is better in terms of location and altitude.

A large increase in the creation of 3D models of objects all around us can be observed in the last few years; thanks to the help of the rapid development of new advanced technologies for spatial data collection and robust software tools. A new commercially available airborne laser scanning data in Czech Republic, provided in the form of the Digital terrain model of the fifth generation as irregularly spaced points, enable locating the majority of rock formations. However, the positional and height accuracy of this type of landforms can reach huge errors in some cases. Therefore, it is necessary to start mapping using terrestrial laser scanning with the possibility of adding a point cloud data derived from ground or aerial photogrammetry. Intensity correction and noise removal is usually based on the distance between measured objects and the laser scanner, the incidence angle of the beam or on the radiometric and topographic characteristics of measured objects. This contribution represents the major undesirable effects that affect the quality of acquisition and processing of laser scanning data. Likewise there is introduced solutions to some of these problems. [ABSTRACT FROM AUTHOR]

More than a hundred abandoned but presently maintained fruit trees are scattered in the Negev Desert Highlands in Southern Israel. Most of the older groves were planted by Bedouins in pre-existing agricultural systems built in the distant past, mainly during the Byzantine era, mostly during the sixth and seventh centuries AD. In these groves a variety of domesticated fruit trees such as date palms, figs, pomegranates, almonds, carobs, pistachios, bitter oranges, grapevines and olives have been planted. The trees growing in these abandoned sites throughout the Negev Highland region are strictly rain-fed and dependent on the amount of runoff water accumulating from the surrounding old runoff harvesting systems with no modern artificial irrigation at least for the past several decades. Despite the lack of active irrigation, some of the trees of all species continue to flourish and even persist in bearing fruit to this day. The trees growing in the Negev Highlands can be divided into several planting periods. The oldest olive trees are apparently descendants of trees planted in the area during the Byzantine period (sixth and seventh centuries AD), while the youngest consist of varieties and species recently planted by Bedouins, until 1948. The factors affecting the survival of the trees are mainly of a geological nature, especially the rock types and their spatial distribution that contribute to the potential of runoff water. Topographic layouts are also critical for enhancing water runoff, as well as various soil parameters, such as water-holding capacity, depth, salinity, and organic matter content. A significant impact on the trees’ condition and survival depends also on the preservation state of the ancient terraces in which they were planted and the level of horticultural expertise of the Bedouins in growing fruit trees. During this study we characterized the geographical, geological and topographical conditions enabling the survival of different fruit trees with no artificially added irrigation in various locations within the Southern Israeli desert. Apparently no specific genotypes were required and involved in the survival of the various fruit trees, but the microconditions at each tree's location were found to be critical. [ABSTRACT FROM AUTHOR]

Xenoceratops foremostensis gen. et. sp. nov., a new centrosaurine ceratopsid from the Foremost Formation (Campanian) of Alberta, is described based on frill material from at least three adult-sized individuals collected from a low-density bone bed. The material can be assigned to Centrosaurinae based on features of the preserved squamosal. Although the parietals are incomplete, the shape of the diagnostic parietal can be inferred from several overlapping serial elements. The parietal of the new taxon shares with all other centrosaurines, except Centrosaurus apertus, spike-like ornamentation at the posterolateral (P3) locus under traditional coding methods. At approximately 78 Ma, it is the oldest known Canadian ceratopsid, approximately 0.5 Ma older than Albertaceratops from the lower Oldman Formation of Canada and approximately 1.0 Ma younger than Diabloceratops from the Wahweap Formation of Utah. A phylogenetic analysis resolves the new taxon as the basalmost centrosaurine and places Centrosaurus brinkmani as the sister taxon to Styracosaurus albertensis. The type species of Centrosaurus brinkmani is moved to a new genus. Xenoceratops foremostensis gen. et. sp. nov., un nouveau ceratopside centrosaurine de la Formation de Foremost (Campanien) d'Alberta, est decrit a la lumiere de materiel de collerette provenant d'au moins trois individus de taille adulte recueilli dans un lit a ossements de faible densite. Le materiel peut etre affecte aux Centrosaurines a la lumiere de caracteristiques des os squamosaux preserves. Bien que les os parietaux soient incomplets, la forme du parietal diagnostique peut etre inferee a la lumiere de plusieurs elements en serie superposes. Le parietal du nouveau taxon a en commun avec ceux de tous les autres centrosaurines, a l'exception de Centrosaurus apertus, une ornementation d'aspect epineux de la bordure posterolaterale (P3), selon les methodes de codage traditionnelles. Datant d'environ 78 Ma, il s'agit du plus ancien ceratopside canadien connu, precedant d'environ 0.5 Ma Albertaceratops, de la partie inferieure de la Formation d'Oldman du Canada, et d'environ 1.0 Ma Diabloceratops, de la Formation de Wahweap de l'Utah. L'analyse phylogenetique etablit que le nouveau taxon est le centrosaurine le plus basal et situe Centrosaurus brinkmani comme taxon-frere de Styracosaurus albertensis. L'espece type de C. brinkmani est reaffectee a un nouveau genre. [Traduit par la Redaction], Introduction Ceratopsidae is the most speciose clade of dinosaurs known from the Late Cretaceous of Laramidia. The fossil-rich Belly River and Edmonton groups of Alberta, Canada, alone have produced at [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.earscirev.2008.11.004 Byline: G.J.H. McCall Keywords: impact structures; craters; shock metamorphism; geophysical investigations; biotic extinctions Abstract: The author, who investigated the Wolfe Creek, Australia, in 1962 and edited two Benchmark Sets of Readings on Meteorite Craters and possible Astroblemes in 1977 and 1979, reviews the state of knowledge at the present time. The text is concerned with terrestrial impact structures, geological features, without any consideration of extraterrestrial analogues. A handful of definitive publications are drawn on to present the story of terrestrial impact in a single article. The text covers historical aspects (briefly); the effect of target variations; the paucity of human observation of such large-scale events; distinction from volcanic (endogenous) structures; modification by geological processes; the transience of the crater initially formed on the target, and its subsequent modifications; the global geographic distribution of the 174 structures now listed (of which a number are dubious attributions); their distribution in geological time (many ages being known only known to wide limits, maximum or minimum values); their size distribution; calculations of impact frequencies; shock effects; processes on impact; the stages of formation; impact into shallow marine and deep sea targets; impacts on ice (about which little is known); and finally the input of impact into biotic extinctions. In this last lengthy section, the summaries of the conclusions of scientists researching impact on Earth and palaeontologists researching biotic impact are set side by side. It is concluded that, if the recent foraminiferal evidence obtained by Gerta Keller and associates is taken at its face value, the case of impact as a sole agent in extinction is non-existent: biotic extinction is clearly a complex process involving a number of causes, in some cases it was staggered in time, and different sets of organisms responded quite differently and surprisingly, even in the same extinction event. Extraterrestrial impact may have been one of the causes in some cases, but it may have been regional rather than global in its effects. We may never know how much input it had into the record of biotic extinction on Earth? An enormous amount of new knowledge has arisen from detailed studies of this new family of remarkable geological structures. Author Affiliation: Western Australian Museum, 44 Robert Franklin Way, South Cerney, Glos., England GL7 5UD, United Kingdom Article History: Received 3 March 2008; Accepted 12 November 2008

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.earscirev.2008.09.001 Byline: Renato Posenato Keywords: biostratigraphy; magnetostratigraphy; carbon isotopes; Early Triassic; Dolomites; Southern Alps Abstract: The Dolomites (Southern Alps, Italy) are a reference-area for research on the end-Permian mass extinction and its Early Triassic aftermath. The effects on shallow marine benthic biota are recorded in the Werfen Formation, a thick mixed carbonate-siliciclastic sedimentary succession. Only in its lower (Griesbachian) and upper (Spathian) parts, this formation is bio-chronologically constrained by means of conodonts and ammonoids, whilst no significant bioevent occurs in its middle part. This represents an impediment to the biochronologic recognition of the Induan/Olenekian boundary (IOB). The Bulla/Pufels (Val Gardena) succession is a key-section for the P/T boundary and Early Triassic for global correlation due to the abundance of studies on biostratigraphy (mostly on conodonts), magnetostratigraphy and chemostratigraphy carried out there by stratigraphers of various nationalities. Recent chemostratigraphic studies have permitted the recognition of some carbon isotope positive peaks, the strongest of which is considered to approximate the IOB. However, various authors have reached different conclusions on the position of the maximum peak and thus on the IOB location. This leads to important stratigraphic consequences for the calibration of conodont biostratigraphy. The critical revision of the traditional stratigraphic units (litho- and biostratigraphy), under-evaluated in most of the recent literature, and magneto-, chemo- and sequence stratigraphic units allowed herein an integrated stratigraphic scale for the Bulla/Pufels section to be proposed. This contribution highlights the mid Early Triassic Dolomites record for regional and global correlations. The most significant results attained herein regard the different lithostratigraphic subdivisions of the middle Werfen Formation and its consequences on the position of the IOB with respect to the conodont and bivalve biostratigraphy and sequence stratigraphic units. The upper part of the section is attributed herein to the Gastropod Oolite Member, which is represented by the lithozone A, a predominant supratidal episode, and the lower part of the subtidal lithozone B. Between the lithozones A and B, a sequence boundary of 3th order (Sc2/Sc3) is located. The maximum carbon isotope excursion is near this boundary, which therefore approximates the IOB in the Dolomites. This proposal suggests a Dienerian age for the FO of the conodont Pachycladina obliqua, which occurs about 60 m below the stage boundary. No significant biotic event, either for molluscs or conodonts, occurred across this stage boundary. Author Affiliation: Dipartimento di Scienze della Terra, Universita di Ferrara, Via Saragat 1, 44100 Ferrara, Italy Article History: Received 13 March 2008; Accepted 23 September 2008

Abstract In 2006 volcanic glass deposits on Vanua Lava and Gaua Islands were re-visited and systematically sampled. Twenty-nine source samples were analysed using EDXA-SEM and LA-ICP-MS with a focus on [...]

Abstract: Pre-Mesozoic rocks are exposed on the southeastern third of Grand Manan Island and adjacent offshore islands in the Bay of Fundy. U-Pb (zircon) ages reported here demonstrate that most [...]

Earth is the only known planet with subduction zones and plate tectonics, and this fact demonstrates that special conditions are required for this mode of planetary heat loss. Sinking of cold, dense lithosphere in subduction zones is the principal plate-driving force, so plate tectonics could not have begun until Earth cooled sufficiently to allow lithosphere to collapse into the underlying asthenosphere. Direct geologic evidence for when the modern episode of subduction tectonics began focuses on the first appearance of ophiolitic graveyards, blueschist facies metamorphic rocks, and ultrahigh-pressure metamorphic terranes. Ophiolites manifest two modes of lithospheric motion expected from subduction tectonics: seafloor spreading and obduction. High-pressure, low-temperature metamorphic blueschists and ultrahigh-pressure terranes indicate subduction and exhumation of oceanic and continental crust, respectively. These lines of evidence indicate that the modern style of subduction tectonics began in Neoproterozoic time. This revolution in the functioning of the solid Earth may have driven wild fluctuations in Earth's climate, described under the 'snowball Earth' hypothesis. These conclusions may be controversial, but suggest fruitful avenues for research in geodynamics and paleoclimate. Keywords: plate tectonics, Neoproterozoic, ophiolites, blueschist, ultrahigh-pressure metamorphism, subduction.

Reprocessed Lithoprobe seismic reflection data across the Appalachian orogen in Newfoundland provide images of an Ordovician-Devonian collision zone that separates Laurentia from Ganderia, an accreted peri-Gondwanan microcontinent. Prominent reflectivity within Ganderian basement tapers westward and merges with reflections that project beneath the Moho, outlining a probable Ordovician to Devonian subduction zone. Reflectivity within Ganderian basement likely originates from transposed compositional layering within Cambrian-Neoproterozoic arc basement. Migmatites and other high-grade rocks of the Meelpaeg allochthon were likely extruded in the Devonian toward the northeast. The reflection Moho may have been established in the Devonian in parts of Newfoundland by partial melting of the lower crust. Reflection truncations outline a near-vertical Carboniferous strike-slip fault zone that cuts the entire crust. Keywords: Newfoundland, Appalachian orogeny, crustal structure, seismic reflection profiles, Lithoprobe, subduction zones.

[1] The Indus River is the only major drainage in the western Himalaya and delivers a long geological record of continental erosion to the Arabian Sea, which may be deciphered and used to reconstruct orogenic growth if the modern bedload can be related to the mountains. In this study we collected thermochronologic data from river sediment collected near the modern delta. U-Pb ages of zircons spanning 3 Gyr show that only ~5% of the eroding .crust has been generated since India-Asia collision.' The Greater Himalaya are the major source of zircons, with additional contributions from the Karakoram and Lesser Himalaya. The [sup.39]Ar/[sup.40]Ar dating of muscovites gives ages that cluster between 10 and 25 Ma, differing from those recorded in the Bengal Fan. Biotite ages are generally younger, ranging 0-15 Ma. Modern average exhumation rates are estimated at ~0.6 km/m.y. or less, and have slowed progressively since the early Miocene (~20 Ma), although fission track (FT) dating of apatites may indicate a recent moderate acceleration in rates since the Pliocene (~1.0 km/m.y.) driven by climate change. The [sup.39]Ar/[sup.40]Ar and FT techniques emphasize the dominance of high topography in controlling the erosional flux to the ocean. Localized regions of tectonically driven, very rapid exhumation (e.g., Nanga Parbat, S. Karakoram metamorphic domes) do not dominate the erosional record. INDEX TERMS: 8102 Tectonophysics: Continental contractional orogenic belts; 1625 Global Change: Geomorphology and weathering (1824, 1886); 1094 Geochemistry: Instruments and techniques; 1035 Geochemistry: Geochronology; 9320 Information Related to Geographic Region: Asia; KEYWORDS: Himalaya, Indus River, fission track, exhumation, erosion, thermochronology. Citation: Clift, P. D., I. H. Campbell, M. S. Pringle, A. Carter, X. Zhang, K. V. Hodges, A. A. Khan, and C. M. Allen (2004), Thermochronology of the modern Indus River bedload: New insight into the controls on the marine stratigraphic record.

The main functions of a three-dimensional test device for simulating rock formations and surface movement affected by underground coal mining were described in detail, and a series of similar related tests were carried out. The device consisted of an outer frame, a pressurization unit, a pulling unit, and a coal seam simulation portion. Using this test device, supported by monitoring methods such as the three-dimensional laser scanner method, a model test study on the surface subsidence characteristics caused by coal seam mining was carried out. Combined with the field measurements, the transfer law of surface subsidence caused by coal seam mining was revealed, and the whole surface subsidence response process was analyzed. The experimental results show that the subsidence caused by mining disturbances below the coal seam accounts for 79.3% of the total subsidence, which is the dominant factor of the total surface subsidence. After long-term surface observations, surface subsidence can be divided into four stages after coal mining, and the settlement value of the obvious settlement stage accounts for more than 60% of the total settlement value. The above test results fully reflect the feasibility and practicality of the three-dimensional test device to simulate rock strata and surface movement and provide a new experimental research tool that can be used to further study the surface subsidence characteristics and control caused by coal mining. [ABSTRACT FROM AUTHOR]

The Spring Mountains are located in southern Nevada and lie along the western margin of the Las Vegas Valley. A diamicton located approximately 2,590 m (8,500 ft) above sea level in the Spring Mountains contains numerous striated limestone clasts ranging in size from 0.5 cm to 1.0 m. There are a variety of physical processes that can produce diamictons, and glacial geologists are often faced with the task of deciding what process controlled the formation of enigmatic diamictons. One characteristic distinctive to glacially derived diamictons is the presence of parallel surface striations on transported clasts. This study presents a GIS-based methodology used to evaluate surface striations on limestone clasts sampled from the Spring Mountain diamicton in southern Nevada. Using a combination of graphical software, ArcView GIS, and Avenue scripting, we streamlined the process of measuring and analyzing orientation values from individual surface striations. The results demonstrate a well-developed preferred orientation for clast striations and support our working hypothesis that the Spring Mountain diamicton is glacial in origin. If we accept a glacial origin, the presence of this deposit at 36[degrees] north latitude suggests the Spring Mountains represent the southernmost extent of Late Quaternary glaciation in the Great Basin. Key Words: diamicton, GIS, glacial geology, orientation, striations.

Differences in radiocarbon apparent ages between coexisting planktonic and benthic (B-P) foraminifers in the Santa Barbara Basin contain information about changes in the age (and thus the source) of water entering the basin. The Holocene sequence indicates a greater variability in circulation than previously detected. During the early Holocene, ca. 9 ka, B-P [sup.14]C apparent age differences fluctuated between 220 and 560 [sup.14]C yr, similar to rapid variations seen during the Younger Dryas and the last glacial episode. During the relatively stable middle Holocene (8.5-2 ka), B-P [sup.14]C apparent age differences averaged 440 [sup.14]C yr. After 2 ka, the average B-P [sup.14]C apparent age difference increased to 620 [sup.14]C yr, which has persisted until the present. The shift in B-P [sup.14]C apparent age differences likely represents a change in the strength or source of North Pacific Intermediate Water production and is concurrent with changes in regional climate patterns as well as with changes in temperature and accumulation rates measured in the Greenland Ice Sheet Project 2 ice core, suggesting large-scale changes in atmospheric circulation patterns. Keywords: radiocarbon, foraminifera, Santa Barbara Basin, Holocene, climate change.

Certain volcanogenic massive sulfide (VMS) ore deposits form in submarine calderas. This association is well known, but the link between caldera formation and the origins of the deposits remains poorly understood. Here we show that the size and location of a VMS deposit within a submarine caldera may be determined by how and when the caldera formed. These spatial-temporal conditions control development of the hydrothermal system associated with the VMS deposit. We propose that caldera opening along outward-dipping faults promotes magma degassing, seawater influx, and high-temperature leaching, resulting in a metal-rich hydrothermal fluid. These outward-dipping faults are considered to provide critical pathways for ore-forming fluids responsible for some caldera-hosted VMS deposits and may also be fundamentally important for the formation of many other caldera-hosted ore deposit types. Keywords: calderas, volcanogenic massive sulfide deposits, fluids, subsidence.

High-Mg, low-Ti diorites in the Cambrian-Ordovician Glenelg River Complex (southeastern Australia) have compositional affinities with the boninitic lavas erupted in intra-oceanic arcs, but occur in an anatectic environment mingled with crustal melts. Boninitic rocks have not previously been recorded from such a setting. Field and petrologic evidence suggests that the parental boninitic liquids are approximated by hornblende diorites, crystallization from which yielded complementary cumulates and evolved tonalitic derivatives. The presence of these rocks, and associated arc-like intrusions, compromises collisional tectonic models for the Glenelg River Complex and instead implies early development of the terrane above a subduction zone. Boninitic magmas were subsequently trapped at deep crustal levels during convergent orogenesis. Keywords: boninite, subduction, crustal melt, diorite.

Dicynodont therapsids have long played an important role in global Late Permian and Triassic biostratigraphy, including recent studies of the effects of the extinction at the Permian-Triassic boundary on terrestrial vertebrates. In particular, the last appearance of the Late Permian taxon Dicynodon has been used to mark the Permian-Triassic boundary in the Karoo Basin of South Africa and to correlate this basin with others in Africa, Europe, and Asia. These practices assume that the named taxon Dicynodon corresponds to a biologically real entity. Here we present the results of a phylogenetic analysis that suggests that this is not the case. Our analysis includes two species referred to Dicynodon that occur only in Russia and the type species that occurs in southern Africa. Our results suggest that these three species do not form a clade to the exclusion of all other dicynodonts; the alternative hypothesis of a monophyletic Dicynodon is more weakly supported. Although preliminary, our analysis challenges the use of Dicynodon for biostratigraphic correlations between Russia and South Africa, and we urge caution in using this taxon to correlate other widely separated basins. This study also emphasizes that without phylogenetic information, there is no guarantee that named taxa represent biologically real entities, and the uncritical use of named taxa can easily lead to spurious biostratigraphic correlations. Keywords: Dicynodontia, biostratigraphy, biochronology, Kazoo Basin, Permian, Russia, South Africa, Therapsida.

Crystal size distributions (CSDs) of quartz and zircon phenocrysts in individual pumice clasts from several voluminous ash-flow tuffs provide a quenched snapshot view of conditions in preclimactic magma chambers. A common feature of these CSDs is a concave-down, lognormal shape, in contrast to the reported linear CSDs in more mafic systems. This feature is interpreted to be a general result of surface-controlled, size-dependent growth by a layer nucleation in silicic magmas at low supersaturation. Specific CSDs may be important for interpreting nucleation and crystal-growth conditions and mechanisms in magmas erupted as large ash-flow tuffs and smaller-volume volcanic units, and for fingerprinting different magma batches (layers) in products of the same eruption. Keywords: crystal size distribution, ash-flow sheets, acid extraction, quartz, zircon, caldera, silicic, nucleation.

We present a kinematic model for the Himalayan thrust belt that satisfies structural and metamorphic data and explains recently reported late Miocene-Pliocene geochronologic and thermochronologic ages from rocks in the Main Central thrust zone in central Nepal. At its current exposure level, the Main Central thrust juxtaposes a hanging-wall flat in Greater Himalayan rocks with a footwall flat in Lesser Himalayan rocks of the Ramgarh thrust sheet, which is the roof thrust of a large Lesser Himalayan duplex. Sequential emplacement of the Main Central (early Miocene) and Ramgarh (middle Miocene) thrust sheets was followed by insertion of thrust sheets within the Lesser Himalayan duplex and folding of the Main Central and Ramgarh thrusts during late Miocene-Pliocene time. Thorium-lead (Th-Pb) ages of monazite inclusions in garnets from central Nepal record the timing of coeval, progressive metamorphism of Lesser Himalayan rocks in the footwall of the Main Central thrust. Although this model does not rule out minor, late-stage reactivation of the Main Central thrust, major late Miocene reactivation is not required. Keywords: Main Central thrust, Ramgarh thrust, Himalaya, Nepal, Lesser Himalayan duplex.

Laterally extensive beds of highly siliceous, hematitic chert (jasper) are associated with many volcanogenic massive sulfide (VMS) deposits of Late Cambrian to Early Cretaceous age, yet are unknown in analogous younger (including modern) settings. Textural studies suggest that VMS-related jaspers in the Ordovician Lokken ophiolite of Norway were originally deposited as Si- and Fe-rich gels that precipitated from hydrothermal plumes as colloidal silica and iron-oxyhydroxide particles. Rare earth element patterns and Ge/Si ratios of the jaspers reflect precipitation from plumes having seawater dilution factors of [10.sup.3] to [10.sup.4], similar to modern examples. We propose that silica in the ancient jaspers is not derived from submarine hydrothermal fluids--as suggested by previous workers--but instead was deposited from silica-rich seawater. Flocculation and precipitation of the silica were triggered inorganically by the bridging effect of positively charged iron oxyhydroxides in the hydrothermal plume. A model involving amorphous silica (opal-A) precursors to the jaspers suggests that silica contents of Cambrian-Early Cretaceous oceans were at least 110 mg/L Si[O.sub.2], compared to values of 40-60 mg/L Si[O.sub.2] estimated in other studies. The evolution of ancient silica-rich to modern Fe-rich precipitates in submarine-hydrothermal plumes reflects a changeover from silica-saturated to silica-depleted seawater through Phanerozoic time, due mainly to ocean-wide emergence of diatoms in the Cretaceous. Keywords: jasper, silica, seawater, hydrothermal plume, germanium, rare earth elements.

Analyses of [sup.87]Sr/[sup.86]Sr in foraminifera and sedimentological observations suggest that the Chicxulub impact was not the trigger for slumps or a hiatus within the Maastrichtian section recovered at Ocean Drilling Program Sites 1049, 1050, and 1052 (subtropical western North Atlantic). The slumps and hiatus occur within a sequence dominated by pelagic chalk. The [sup.87]Sr/[sup.86]Sr measurements show a general increase through the Maastrichtian at each site, but suggest chronostratigraphic gaps on the order of [10.sup.6] yr across the slumps. Some of the slumps have burrowed upper surfaces and are composed of material that is older and coarser grained than the bounding chalks. Pelagic deposition punctuated by gravity flows easily explains the Maastrichtian record on Blake Nose, whereas an impact-based explanation for slumping is difficult to reconcile with sedimentological and geochemical observations. Keywords: Cretaceous-Tertiary boundary, strontium isotopes, slump, Maastrichtian, Ocean Drilling Program.

Pre-Quaternary terrestrial climate records in which time has been calibrated using astronomical cycles are, with the exception of lacustrine proxies, poorly represented in the geological record. This omission is a significant gap in our knowledge of ancient climate systems. Here we present new evidence of orbital periodicities in an 18.3-m-thick late Paleocene coal and conclude that coal has the potential to provide continuous time-calibrated terrestrial climate data. Spectral analysis of changes in the relative proportions of vitrinite to inertinite, two environmentally sensitive coal macerals, reveals several characteristic frequencies, some of which display evidence of amplitude modulation every five to six cycles. Combining this observation with depositional time limitations derived from present-day rates of carbon accumulation in mires, we interpret the characteristic frequencies as resulting from precession and obliquity and their influence on oxidation and decay. Using the inferred precession component of the data to derive an internal time scale, we estimate that the Wyodak coal was deposited over a period of ~414 k.y. with a long-term carbon sequestration rate of 29 g [m.sup.-2] [yr.sup.-1]. The identification of an internal astronomical time scale in coal is an important step toward realizing the potential for coal to extend our high-resolution knowledge of Earth's terrestrial climate back to the formation of the first peat deposits at 360 Ma. Keywords: Paleocene, coal, climate, carbon.

The tectonic convergence between the South China block and Qinling belt that occurred in Mesozoic time was not homogeneous along strike; it was mainly concentrated in the Shengnongjia and Hannan domes, which formed a pair of indentors, along which the South China block penetrated the Qinling belt. As a consequence, the Tongbai-Dabie Shan belt, the eastern part of the Qinling orogenic belt, may have undergone large-scale eastward extrusion, clockwise rotation, and uplift, as indicated by its boundary deformation features. It was originally located beneath the narrowest part of the Qinling belt, where it underwent ultrahigh-pressure metamorphism in the Early Triassic. Keywords: Tongbai-Dabie Shan belt, extrusion, rotation, uplift, indentation.

We demonstrate that cosmogenic radionuclides can be employed to trace sediment when the sources have sufficiently distinct concentrations, and develop a theoretical mixing model for a rocky coastline littoral system. We combine the resulting mixing model with existing cosmogenic radionuclide methods that quantify river inputs and terrace ages to determine the major components of the long-term littoral sediment budget of the Santa Cruz, California, coastline. Sediment derived from coastal basins eroding at 0.2 mm/yr has a much lower concentration than sediment derived from 60-84 ka terrace sands atop backwearing seacliffs. The complex pattern of cosmogenic radionuclide concentrations in littoral sands along >100 km of coastline can be explained by mixing sediment derived from seacliffs backwearing at 10 cm/yr with that delivered by rivers having widely different amounts of sediment discharge. Keywords: littoral cell, sediment budget, cosmogenic elements, Santa Cruz County, California.

New major element, trace element, and Nd isotope data are reported for volcanic rocks from the 2.9 Ga Lower Greenstone and 2.7 Ga Upper Greenstone assemblages of the Belingwe Greenstone Belt. The majority of samples from five distinct stratigraphic units have generally unfractionated to slightly depleted trace element patterns similar to those observed, in the small number of previous studies. However, previously unrecognized incompatible element-enriched samples with distinct high field strength anomalies invariably also occur in close association. These are reminiscent of crustally contaminated rocks from other well-documented greenstone settings. Numerical modeling of combined assimilation-fractionation processes using both trace and major elements suggests 10%-30% incorporation of model Archean continental crust in their genesis, in accord with Nd isotope compositions. These new observations are not consistent with a mid-ocean-ridge or oceanic plateau-type setting for Belingwe Greenstone Belt volcanism, but instead favor a model in which melts interacted with preexisting continental crust. Keywords: Archean, Belingwe Greenstone Belt, crustal contamination, komatiite, Zimbabwe craton.

Synmagmatic and solid-state structures within the Naxos pluton and its rim may provide insight into the interplay between plutonism and regional deformation at upper-crustal level. Within the hornblende--biotite granite of western Naxos, synmagmatic foliations display two distinct patterns, onion-skin in the north and tangential to the rim in the south. The two areas are separated by the NE-trending Glinadon fault. Deformed mafic enclaves in the pluton are prolate, with their long axes parallel to the synmagmatic lineation. In contrast, phenocryst distribution analysis, using the Fry method, defines an apparent oblate strain with a horizontal stretching lineation. Planar markers within the pluton progressively steepen through the vertical at the east pluton border. Several lines of evidence, such as dykes intruding axial areas of rim-parallel folds, foliated or folded aplite veins, folds and spaced cleavage in the mollase, and inverted stratigraphy, suggest pluton emplacement and deformation during transpressional deformation. A northward divergent flow regime with magma spreading out mainly from the Naxos fault, and the deflection of both the synmagmatic foliation pattern and the flow lines at the Glinadon fault, suggest that the NE-SW- and N-S-trending faults were active during pluton formation. In the south the pluton has grown by the expansion of dykes occupying P-shear positions with respect with the Naxos fault; in the north a piecemeal block down-drop complements this process and favours voluminous magma concentration. During the late evolutionary stages of pluton construction, the magma chamber was compartmentalized into NE-trending sectors affected by block rotation in an anticlockwise manner. Understanding the role of faults in the emplacement of the Naxos pluton is important for understanding emplacement of other plutons in the Aegean Sea region, since most of them are controlled by N-S- (Ikaria pluton) or NE- (Tinos, Serifos and Delos plutons) trending faults. Keywords: Naxos, plutons, faults, strain, transpression, Greece.

The relationship between the Dalradian Supergroup and the Highland Border Complex in Scotland has remained contentious for over a century. In western Ireland, the contact between the Dalradian Supergroup and the Clew Bay Complex (a correlative of the Highland Border Complex) is superbly exposed on the island of Achill Beg on the North Mayo coast. The unfossiliferous South Achill Beg succession has been traditionally assigned to the Clew Bay Complex, and this interpretation is supported by a combination of Sm-Nd model age data, heavy mineral analysis and lithostratigraphic correlation. [T.sub.DM] ages range from 1.99-2.66 Ga (mean = 2.28 Ga, n = 6). Detailed structural mapping shows that both the Dalradian and the Clew Bay Complex share the same structural history. A D1 high strain event is common to both units, and is associated with the development of tectonic slides. The D2 event is responsible for the formation of crustal-scale nappes. In both units, beds are consistently downward facing on the S2 foliation. Later dextral shearing (D3) resulted in the tilting of the originally recumbent, S-facing D2 nappes into this downward-facing orientation. Rb-Sr and [sup.40]Ar-[sup.39]Ar radiometric dating of muscovite confirms that both units were deformed contemporaneously as the S2 nappe fabric in each is dated at c. 460 Ma. This Middle Ordovician age for deformation of the Clew Bay Complex is highly significant, not least because published microfossil data suggest a Silurian age. Keywords: Dalradian Supergroup, Highland Boundary Fault, Ireland, structural geology, geochronology, Sm/Nd.

Many late Mesozoic lamprophyre dykes occur in the Taihang Mountains (north China). These lamprophyres are rich in large ion lithophile elements (e.g. Rb, Sr, Ba and K) and light REE, and have highly differentiated REE patterns. They show large but regular variations in chemical and Nd-Sr isotopic compositions. All these suggest that the lamprophyres were produced from differentiation of a parental magma, coupled with contamination by lower crust. The parental magma was derived from melting of a long-term enriched sub-continental lithospheric mantle source as is indicated by the highly enriched isotopic signatures of the lamprophyres. Mantle enrichment in the area was probably produced by interaction of volatile-rich melts released from the asthenosphere with the above lithosphere in middle Proterozoic times. Keywords: geochemistry, lamprophyres, lithosphere, Mesozoic, northern China.

Heavy minerals in Ordovician successions in western Ireland record, in the Upper Arenig Sheeffry Formation, the erosion of an ophiolite/island are complex. The appearance of staurolite and garnet at a basin-wide horizon in the Lower Llanvirn Upper Derrylea Formation signals the unroofing of the Dalradian metamorphic complex. Parts of the Ordovician sequence on Inishturk and in two small inliers are correlated with the standard sequence with unexpected results. The garnet-, sillimanite-, and staurolite-bearing Letter Formation correlates with the Upper Derrylea Formation and, on Inishturk, heavy minerals in south-younging turbidites reveal a sinistral ramp zone, that places the Sheeffry Formation structurally above and to the south of the younger Derrylea Formation. Keywords: Dalradian, Grampian Orogeny, island arcs, accretionary prisms, heavy minerals, correlation.

Diagenetic illite (mixed layer illite-smectite, I-S) from Ordovician and Devonian potassium bentonite (K-bentonite) and shales was studied in the proximal southern Appalachian Basin (Alabama through Virginia) to understand in more detail the timing of illite formation as well as attempt to describe the chemistry of the fluids that formed illite during the Alleghanian Orogeny through combined K/Rb and oxygen isotope analyses. The clay fraction of the K-bentonites is composed predominantly of illite-smectite (I-S) and chlorite. Most I-S exhibited Kalkberg order (IISI) with >85% illite layers. The K-Ar dates of I-S from Ordovician K-bentonites and Devonian K-bentonites mostly range from 260-310 Ma and indicate I-S formed during the Alleghanian Orogeny. Internally concordant dates and similar percentages of illite layers of I-S are measured from several samples collected within a thick (1 m) Ordovician K-bentonite at Fort Payne, Alabama. The oxygen isotopic values ([delta][sup.18]O) of I-S range from 18-23[per thousand] SMOW. At lowest levels of thermal maturity and burial, as seen by conodont alteration index values (CAI) of 1.5-2.0, the range in [delta][sup.18]O values of water in equilibrium with I-S is 2.5-3.5 [per thousand]. At higher thermal maturity (CAI = 2.5-4.5), the [delta][sup.18]O of water in equilibrium with I-S is from 4.5 to 12 [per thousand]. The [delta][sup.18]O analyses are mostly consistent with I-S having formed in the presence of orogenic (i.e., saline) waters. The mean K/Rb of the Appalachian illites from this study is 325 (N = 20). This mean K/Rb is also consistent with the formation of diagenetic I-S in the presence of a saline fluids having higher K activities than meteoric waters. The combined data indicate these diagenetic illites in K-bentonites formed from saline/orogenic waters during the Alleghanian Orogeny along the Valley and Ridge Province in the southern Appalachian Basin. Although the data rule out formation of diagenetic illite in the presence of meteoric water or long-term reaction with connate formation waters, the combined data cannot distinguish the source and the mechanism (tectonic push or flush from tectonic highlands) for the movement of saline fluids in the Appalachian Basin.

Previous research indicates that if layered sand deposits are liquefied during earthquakes, water films are likely to develop beneath less permeable sublayers and lead to the destabilization of sloping ground. In Niigata City, large lateral flow displacements were reported in almost flat areas during the 1964 Niigata earthquake. The involvement of water films in lateral flow failure during the earthquake is examined in this research based on site investigation data. Soil profiles in the investigated areas estimated from many borehole logs indicate that continuous or partially continuous sublayers of fine soil that cap liquefiable loose sand exist. Elevation contours of 0.1 m increments are drawn based on an in situ leveling survey and local maps. The ground slopes obtained are found to be closely related to flow displacements evaluated in previous research, indicating that a gentle slope of less than 1% results in displacement of several meters. This strongly suggests that water films with literally no shear resistance formed beneath fine soil sublayers were highly responsible for the large lateral flow displacements in these areas during the Niigata earthquake. DOI: 10.1061/(ASCE) 1090-0241 (2002) 128:11 (917) CE Database keywords: Liquefaction; Japan; Slopes; Earthquake damage; Soil.

An SEM, REE, and mineral Sm-Nd isotope study on olivine-plagioclase coronas in the Vestre Dale gabbro, Norway, was carried out in order to solve the temporal relationships within these coronas. It is demonstrated that in contrast to common models, corona formation is a multistage, late-magmatic process, starting with the formation of orthopyroxene by (partial) dissolution of olivine, followed by the nucleation and rapid outward growth of orthopyroxene + spinel symplectites at its outer margin, and concluded by replacement of this precursory outer shell by calcic amphibole. Isotopic equilibrium between inner shell orthopyroxene and the magmatic assemblage, and the REE contents of orthopyroxene and outer shell amphibole also provide strong arguments for a magmatic origin, with the local availability of fractionated magma acting as a limiting factor. The absence of replacement of intercumulus clinopyroxene by amphibole also favours a late stage magmatic rather than a metamorphic origin for corona amphibole.

The Jurassic-Cretaceous Peninsular Ranges batholith of southern and Baja California exhibits several along-strike variations that are most pronounced across the Agua Blanca fault. These variations include differences in the age of magmatism, degree of inheritance in zircons, depositional environment of volcanic strata, extra-arc basin geography, lateral extent of continentally derived flysch strata, and the structures attending juxtaposition of the two segments with the North American continental margin and with each other. We propose that these variations, when taken together, imply that the two segments of the western zone currently juxtaposed by the active Agua Blanca fault were accreted to North America diachronously and did not share a common history prior to the late Early Cretaceous. The Santiago Peak arc segment north of the fault developed on oceanic lithosphere juxtaposed with the continental margin prior to and during arc magmatism. Conversely, the Alisitos arc segment developed on oceanic lithosphere exotic to North America prior to accretion at 115-108 Ma. If this model is correct, it implies that the Agua Blanca fault initiated as a transpressional continuation of the suture joining the latter arc segment to the continent and that a large portion of the forearc that existed between them was subducted. Keywords: Peninsular Ranges batholith, accretion, island arc, Agua Blanca fault, Main Martir thrust.

Hypervelocity impacts of cosmic projectiles larger than ~200 m diameter are capable of forming complex craters on Earth. At these craters, shock loading, shock damage, and excavation flow are followed by a gravity-driven collapse of the deep transient cavity. Such impact structures are characterized by a central uplift, a flat crater floor, and a terraced crater rim. Collapse-induced deformation features, like folds and brittle fault zones, have many similarities to tectonic structures. Typical deformation patterns of complex terrestrial impact craters of 5-15 km diameter are compiled and analyzed with respect to their kinematic development. Unlike their tectonic counterparts, deformation structures are always the result of non-plane-strain deformation and are formed in a single event that takes place in seconds to minutes. To understand the high-strain-rate processes, the microstructure of an impact-induced fold of the Crooked Creek impact crater (~7 km diameter), Missouri, United States, is investigated in detail. A period of 20-30 s at the most is determined for the collapse phase of this crater. The gross plastic deformation behavior of the fold is achieved by localized brittle deformation along millimeter- to centimeter-spaced fault zones, forming a network of veins. Shock damage has fractured ~40% of grain boundaries. The onset of collapse and associated deformation started in rocks with a reduced cohesion and is friction controlled. Keywords: folding, impact craters, cratering, brittle deformation, friction.

Soil development can significantly influence the topographic evolution of a tectonically deforming mountain piedmont. Faults and folds associated with the North Frontal thrust system deform piedmont sediments of variable compositions along the north flank of the San Bernardino Mountains. The topographic expressions of folds with similar structural characteristics diverge appreciably, primarily as a function of differences in sediment composition and associated soil development. Soils with petrocalcic horizons in limestone-rich deposits are resistant to erosion, and anticlinal folds form prominent ridges. Folds forming in granite-derived deposits with argillic soil horizons are eroded and/or buried and are therefore topographically less pronounced. We propose that these landform contrasts can be explained by differences in soil-controlled hydrologic and erosion characteristics of deposits without calling upon changes in tectonic style along the mountain front. Keywords: soil, landscape evolution, tectonics, folds, erosion, San Bernardino Mountains.