comparison of a paleosol carbonate isotope record to other records of pliocene early pleistocene climate in the western united states paleoecological and paleoenvironmental interpretations of stable isotope composition of pedogenic carbonate collected from the pliocene early pleistocene st david formation in southeastern arizona united states correlate with other proxy records of paleoclimate in the western united states wetter and perhaps cooler conditions between 3 2 and 2 8 ma are associated with lacustrine highstands at tulelake and searles lake in california a general trend toward drier conditions in the late pliocene is also apparent in all records a protracted arid monsoonal climate in the early pleistocene implied by the soil isotope data from arizona is not as readily correlated to other climate records and is perhaps related to uplift in the southern cordillera soil carbonate isotope data provide relatively continuous paleoclimatic records from fluvial sequences that supplement lacustrine records together they provide a framework for interpreting pliocene climate

tectonic setting mineralogy and chemistry of a metamorphosed stratiform base metal deposit within the himalayas of pakistan stratiform zn pb mineralization of probable proterozoic age occurs in a structurally complex area near the northern margin of the indian plate around besham in the north west frontier province of pakistan the sphalerite and galena mineralization is associated with a well defined stratigraphy of carbonate layered calc silicate quartzite garnet bearing quartzo feldspathic gneiss feldspathic granulite and albite gneiss associated with the ore are varying proportions of pyrrhotite pyrite baryte clinopyroxene quartz garnet actinolite pyroxmangite feldspar carbonate and magnetite the mn rich composition of the silicate minerals and the widespread enrichment of ba in the rocks associated with the ore form a distinctive signature of the mineralization recognizable in reconnaissance exploration this signature is distinct from that of skarn minerals formed later in carbonate rocks as a result of the intrusion of pegmatites the recognition of the stratiform nature of the deposits within a well defined stratigraphy enhances the exploration potential of the mineralization over a much wider area

geo tectonic framework of the himalaya of n pakistan in the karakorum range there is a structurally complicated cretaceous are comprising the kohistan sequence on its northern side the northern suture consists of a mega melange and is bounded to the s by tightly folded pillow bearing volcanics and sediments to the s the kohistan plutonic belt consists of southwards a early foliated and late post tectonic tonalites and diorites b aplites and pegmatites up to 30 of rock volume c basic dykes up to 10 m thick d the chilas complex a stratiform cumulate body over 300 km long and 8 km thick chromite layered dunites gabbros and norites with a low pressure granulite facies mineral fabric of tectonic origin e an amphibolite belt with a complex mixture of other rocks and f the jijal complex a 200 km 2 tectonic wedge of high pressure granulites and chromite layered dunites cumulate graded units in the chilas complex show that it is folded by an isoclinal anticline f 1 the mid upper crust of the are is folded by a 50 km half wavelength f 2 syncline the whole kohistan sequence with its two phases of isoclinal folds was tilted during himalayan collision so that the structures are now subvertical the southern suture main mantle thrust has a wedge of glaucophane schists the indian plate contains a basement of psammites and schists intruded by cambrian granites and overlain by isoclinally folded and metamorphosed carbonates and shales

hydrothermal alteration of graywacke and basalt by 4 m nacl separate experiments at 350 degrees c and 500 bars at a rock fluid ratio of 1 10 illite dolomite and quartz amounting to 67 percent of the original graywacke were converted to albite and smectite the rock gained na and released ca k heavy metals and co 2 to solution in sharp contrast the reaction of 4 m nacl with basalt produced only minor alteration albitization of graywacke produces h super whereas albitization of basalt apparently consumes h super all experiments to date that have reacted basalt with sea water natural brine and fully saturated nacl over a variety of conditions have been unsuccessful in producing a spilite alteration assemblage modified journal abstract

introduction energy and the subsurface this theme issue covers topics at the forefront of scientific research on energy and the subsurface ranging from carbon dioxide co2 sequestration to the recovery of unconventional shale oil and gas resources through hydraulic fracturing as such the goal of this theme issue is to have an impact on the scientific community broadly by providing a self contained collection of articles contributing to and reviewing the state of the art of the field this collection of articles could be used for example to set the next generation of research directions while also being useful as a self study guide for those interested in entering the field review articles are included on the topics of hydraulic fracturing as a multiscale problem numerical modelling of hydraulic fracture propagation the role of computational sciences in the upstream oil and gas industry and chemohydrodynamic patterns in porous media complementing the reviews is a set of original research papers covering growth models for branched hydraulic crack systems fluid driven crack propagation in elastic matrices elastic and inelastic deformation of fluid saturated rock reaction front propagation in fracture matrices the effects of rock mineralogy and pore structure on stress dependent permeability of shales topographic viscous fingering and plume dynamics in porous media convection this article is part of the themed issue energy and the subsurface

ages of alpine tectonometamorphic events in the northwestern himalaya northern pakistan by 39ar 40ar method the main tectonometamorphic alpine events which occurred in the western part of the western himalayan virgation at south of the main suture in northern pakistan are dated by the 39ar 40ar method these events are as follows 1 the blueschist metamorphism 80 5 ma present in tectonic ophiolititic melanges along the suture this event occurred during an early subduction or obduction stage 2 the alpine barrovian metamorphism 50 30 ma developed in the sedimentary cover and orthogneisses of the indian plate during the postcollisional northward underthrusting of this plate below asia and 3 the emplacement of postmetamorphic leucogranites 23 ma resulting from the melting of the indian crust during the climax of the alpine metamorphism

metamorphism and crustal stacking in the north indian plate north pakistan abstract the northern part of the indian plate in north pakistan is composed of a number of large scale crustal nappes each of which are stratigraphically distinct and which were stacked late in the main phase of southeasterly directed thrusting associated with the himalayan event the major nappes recognised in the swat to kaghan area of north pakistan are the besham swat hazara banna lower kaghan and upper kaghan nappes metamorphism was synchronous with early stages of deformation within each nappe the metamorphic grade increases upwards an overall inversion that represents post metamorphic imbrication within individual nappes synchronous with the main phase of nappe stacking rather than a hot iron type inversion as described under the mct in nepal and india as a result of this within nappe imbrication each thrust slice within any particular nappe contains rocks of a higher metamorphic grade than those in the slice below with sharp metamorphic breaks across the imbricating thrusts as well as across the major shears that bound the crustal scale nappes uplift along these imbricating thrusts initiated cooling of the stack k ar mica and hornblende cooling ages imply that much of this uplift was completed by 30 ma or within 20 ma of the collision

growth model for large branched three dimensional hydraulic crack system in gas or oil shale recent analysis of gas outflow histories at wellheads shows that the hydraulic crack spacing must be of the order of 0 1m rather than 1m or 10m consequently the existing models limited to one

a 24 000 year period climate signal in 1 7 2 0 million year old death valley strata continental records of plio pleistocene climatic fluctuations are often confined to fragmentary localized basins and not easily dated one exception is the confidence hills of southern death valley in this study we present a detailed description of a plio pleistocene section of interfingering alluvial fan and saltpan sediments from the confidence hills southern death valley this well exposed section accumulated with an average deposition rate of 25 cm 1000 yr with no bioturbation permitting more precise paleomagnetic dating than in oceanic records 1 we interpret the sequence of facies changes in the olduvai normal polarity zone of the confidence hills to represent alternations between wetter and drier regional climatic regimes the frequency of this variation 24 000 yr appears to correspond to the milankovitch precessional cycle 23 000 yr we believe this section records a milankovitch driven climatic variation in the death valley basin annual precipitation about 1 7 2 0 ma this is the first report of the precessional cycle in continental sediments of this age in the united states

middle to late miocene middle eastern climate from stable oxygen and carbon isotope data southern alborz mountains n iran abstract the alborz mountains of northern iran intercept and divert the northern hemisphere westerlies carrying moisture from the mediterranean and black sea and form an orographic barrier to moisture sourced to the north in the caspian sea this implies that terrestrial deposits along the southern alborz mountains leeward side of northerly winds and windward side of westerlies with the respect to tibet and other mountainous terrain in the himalayan karakoram realm potentially track changes in past moisture and erosional regimes and mirror rainfall patterns here we present results of a stable isotope analysis and clay mineral study of the miocene ca 17 5 7 6 ma upper red formation in the foreland of the southern alborz mountains the changes recorded by stable oxygen and carbon isotope data from pedogenic and lacustrine palustrine carbonate in the southern alborz mountains suggest 1 an increase in aridity possibly related to the evolution of the alborz orographic rain shadow which became more efficient between 17 5 and 13 2 ma 2 a steady increase in precipitation between 13 2 and 10 3 ma with a significant increase in rainout along the southern slope of the alborz mountains between 11 and 10 3 ma possibly related to perturbations in atmospheric circulation pattern in the northern hemisphere as suggested by coeval wetter phases in southern europe and 3 a decrease in aridity from ca 9 6 to 7 6 ma possibly reflecting an increase in the seasonality of precipitation based on environmental and climatic changes observed across southern asia and india starting from ca 10 ma we speculate that the topographic evolution of the himalayan tibetan system might have affected the late miocene climate in middle east

effects of rock mineralogy and pore structure on stress dependent permeability of shale samples we conducted pulse decay permeability experiments on utica and permian shale samples to investigate the effect of rock mineralogy and pore structure on the transport mechanisms using a non adsorbin

oxygen isotope evidence of climate change from pedogenic clay minerals in the himalayan molasse abstract in this study we examine the oxygen isotope ratios of smectite and kaolinite in a stratigraphic sequence of paleosols in the siwalik himalayan molasse on the potwar plateau northern pakistan there is a 3 4 o increase in the smectite 18 o values synchronous with a 3 5 o increase in 18 o values of pedogenic calcite at 8 5 6 5 ma previously observed by quade et al 1989 the covariation of the 18 o values of smectite with calcite gd 18 o values through time strongly suggests a pedogenic origin of smectite and that its 18 o values reflect the oxygen isotope ratio of the soil water present during pedogenesis these data show that the 18 o values of clay minerals in paleosols in aggrading sedimentary sequences are viable paleoclimate indicators kaolinite 18 o values are similar to smectite 18 o values as would be expected for pedogenic kaolinite but there is greater variation in these data which we attribute to incomplete mineral separation the measured permil oxygen isotope fractionation between calcite and smectite within individual paleosols is on average 3 o higher than the equilibrium fractionation this isotopic disequilibrium can be explained by the calcite forming predominantly during the dry winter season and the smectite forming predominantly during the wet summer season the synchronous 3 5 o increase in oxygen isotope ratios of smectite and calcite at 8 5 6 5 ma indicates that this 18 o 16 o increase is not due to diagenesis but rather results from a climate change the most likely causes of the 18 o 16 o increase in smectite and calcite are either increased aridity resulting in increased soil water evaporation thus 18 o enrichment and or a change from more continental to more marine sourced precipitation the tibetan plateau which is suggested to have undergone rapid uplift around 8 ma e g harrison et al 1992 may have acted as an effective orographic barrier to low 18 o precipitation originating from central asia causing higher 18 o values of the precipitation falling on the potwar plateau currently it is impossible to distinguish between these two potential causes of the 18 o 16 o increase at 8 5 6 5 ma but these clay mineral 18 o values support that there was a significant climate change in this region

diatom inferred salinity changes from the yushe paleolake indicate an aridification during the pliocene pleistocene transition in north china abstract the global climate changed significantly during the pliocene pleistocene transition and a worldwide aridification occurred in order to investigate the influence of the aridification during the pliocene pleistocene transition in the east asian interior diatom assemblages from the upper zhangcun formation north china deposited during 2 7 2 5 ma bp were analyzed and the lake salinity was reconstructed using diatom environment transfer functions a total of 74 diatom taxa were found in the sediments belonging to 21 families and 32 genera four zones were established from the bottom to the top based on the changes in the diatom assemblages over the 15 7 m sediment sequence in zone 1 cyclotella iris dominated in assemblage while caloneis westii and staurosira construens were less presented among representative species in zone 2 c iris dominated which indicates carbonate rich water but in zone 3 benthic pennate taxa such as c westii and anomoeoneis sphaerophora became more abundant indicating a significant increase in water salinity from carbonate type to sulfate type caused by climatic change in zone 4 c iris became dominant again with abundant gomphonema intricatum and rare pinnularia rathsbergiana and martyana martyi species the salinity inferred by conductivity reconstruction increased from 1 9 ppt in zone 2 to 4 1 ppt in zone 3 the significant changes of anion ratio alk cl so42 indicate an abrupt change from carbonate rich to a sulfatic type water the increase of salinity reflects changes in the precipitation evaporation balance the change from carbonate to sulfatic water inferred from the diatom assemblages could indicate a significant aridification around ca 2 6 ma bp on the eastern edge of the loess plateau this is the most easterly record of aridification across the eastern asian interior and may be related with the global cooling and the development of the northern hemisphere glaciation

polygenetic development of the mormon mesa nv petrocalcic horizons geomorphic and paleoenvironmental interpretations abstract mormon mesa nevada usa is of one of earth s rare and unique landforms regionally mormon mesa is important because of its relationship to the lower colorado river and its connection to stream incision petrocalcic horizons at mormon mesa developed from multiple exposure erosion and sedimentation events driven by variations in paleoclimate since the early pliocene this study utilizes pedogenic features at mormon mesa to construct a sequence of development for the soil profile we sampled and described seven profiles at mormon mesa to determine the soil and geomorphic processes that have influenced the development of this geomorphically important soil the mormon mesa soil profile generally consists of four petrocalcic soil horizons from the base upward transitional laminar massive and brecciated and an additional set of horizons that formed in unconsolidated surficial eolian sediments the transitional horizon formed after cessation of muddy creek fm deposition 5 to 4 ma and accumulated calcium carbonate to a stage ii iii morphology maybe iv in some locations after a period of landform stability the upper portion of the transitional horizon was exposed and eroded 2 8 ma petrocalcic fragments and stage ii pendants that formed in the transitional horizon were exposed on the surface and later mixed with aggrading eolian sediments after the surface re stabilized calcium carbonate accumulated along the underlying discontinuity with the transitional horizon and formed a laminar horizon shallower accumulations of calcium carbonate formed pendants on the undersides of the rotated petrocalcic fragments and pendants that had previously been eroded from the transitional horizon continued rooting and bioturbation caused rotation and multiple directions of pendant formation today in plan view these pendants appear concentric and are the pisoliths described by bachman and machette bachman g o machette m n 1977 calcic soils and calcretes in the southwestern united states usgs open file report 77 797 continued calcium carbonate precipitation eventually plugged the horizon massive horizon after the massive horizon became indurated the upper portion was exposed fractured eroded and mixed with aggrading eolian sediments these brecciated fragments experienced erosion brecciation and soil stabilization cementation with pedogenic calcite multiple times probably as a result of the pleistocene glacial interglacial climate cycles all of the features described in this study are interpreted to have formed in response to climatic changes that caused either soil erosion with concurrent eolian deposition or soil development and pedogenic carbonate accumulation it is important to understand the development of the mormon mesa soil because it can provide an understanding of the pedogenic and geologic processes that effect the development of stages v and vi soil horizons this study provides a relative sequence of events for the formation of pedogenic features at mormon mesa that can be used for future dating applications more precise dates for the development of the mormon mesa soil will contribute to our understanding of the geomorphic tectonic and climatic processes that have affected this region

cooling and uplift histories of the crystalline thrust stack of the indian plate internal zones west of nanga parbat pakistan himalaya abstract amphibole and mica k ar ar ar and rb sr geochronology for the crystalline internal zones of the indian plate define both an extensive pre himalayan thermal history and a post himalayan metamorphism cooling history south of the main mantle thrust near besham hornblende ar ar ages from basement gneisses record an ca 1850 ma mid proterozoic thermal event hornblende muscovite and biotite cooling ages from cover sequences metamorphosed during the himalayan orogeny are 35 4 30 to 24 and 29 to 22 ma respectively the mica ages together with those derived from zircon and apatite fission track data zeitler 1985 demonstrate a rate of cooling of about 30 c ma during the late oligocene to early miocene that was greater than that either before or since this rapid cooling was initiated during the post metamorphic evolution of the indian plate south verging crustal scale thrust stack during which cover sequences metamorphosed during the himalayan orogeny were imbricated with basement rocks thermally unaffected during that event most of the cooling which happened during the stripping of some 10 2 km of overburden reflects exhumation due to a combination of erosion recorded in the miocene molasse sediments of the foreland basin and major crustal extension within the mmt zone both erosion and extension were the direct consequence of the evolution of the thrust stack

understanding hydraulic fracturing a multi scale problem despite the impact that hydraulic fracturing has had on the energy sector the physical mechanisms that control its efficiency and environmental impacts remain poorly understood in part because the length scales involved range from nanometres to kilometres we characterize flow and transport in shale formations across and between these scales using integrated computational theoretical and experimental efforts methods at the field scale we use discrete fracture network modelling to simulate production of a hydraulically fractured well from a fracture network that is based on the site characterization of a shale gas reservoir at the core scale we use triaxial fracture experiments and a finite discrete element model to study dynamic fracture crack propagation in low permeability shale we use lattice boltzmann pore scale simulations and microfluidic experiments in both synthetic and shale rock micromodels to study pore scale flow and transport phenomena including multi phase flow and fluids mixing a mechanistic description and integration of these multiple scales is required for accurate predictions of production and the eventual optimization of hydrocarbon extraction from unconventional reservoirs finally we discuss the potential of co2 as an alternative working fluid both in fracturing and re stimulating activities beyond its environmental advantages this article is part of the themed issue energy and the subsurface