fracture cleat analysis of coals from zonguldak basin northwestern turkey relative to the potential of coalbed methane production abstract in this study the fracture structure of three coals sulu k 1 acilik k 2 and cay dogu ayak from two different seams in the zonguldak basin located on the black sea coast of turkey have been analyzed in relation to coalbed methane recovery x ray computerized tomography ct light microscopy image analysis and scanning electron microscopy sem analysis have been performed on mine coal samples to have a better understanding of distribution of minerals fracture morphology and apertures and matrix fracture interactions via examination of fracture surfaces results show that the acilik and sulu coals seem to be structurally more prone to be commercially productive these coals show a high degree of fracturing and cleat development as evidenced by x ray ct and light microscopy examination of polished surfaces although the cay dogu ayak coal shows a high fracture density the cleat surface morphology and smaller fracture apertures may make this coal unfavorable for gas flow

co2 permeability of indian bituminous coals implications for carbon sequestration abstract the permeability of coal is one of the most critical parameters in estimating the performance of coal seams as methane reservoirs or carbon dioxide sinks the reservoir behaviour of coal offers many challenges for the long term planning of gas production performance and the drainage of water from reservoirs moreover heterogeneity in coal from basin to basin from seam to seam and within parts of the same seam makes the process more complex reservoir specific understanding is needed for the best possible estimation of its behaviour factors such as shrinkage swelling of coal matrix gas flow and slippage geomechanical changes cleat anisotropy and effective stresses control the flow behaviour of gases in coal studies of these aspects have gathered momentum in recent decades for different basins across the world however no research is available on swelling induced permeability characteristics or the role of effective stresses for gondwana coals in india considering the fairly high co 2 storage potential of indian coals bituminous coals of the barakar formation in jharia basin india were tested using gas phase co 2 under triaxial conditions this paper presents the results of changing effective stresses in terms of confining stresses and pore pressure incorporating the role of coal swelling with time on the flow pattern of gaseous co 2 corresponding to different depths of target coal seams coal was subjected to different confining stresses in a newly developed triaxial cell for each confinement co 2 was injected at different injection pressures to minimize the effects of temperature on the characteristics of the gas phase it was kept constant at 26 c throughout while use of the drained method of testing maintained the downstream pressure equal to one atmosphere the results showed that at low confinement increase in gas injection pressures leads to an initial decrease in permeability of coal which then becomes almost constant however at higher confinements the permeability increases with increasing injection pressure swelling in coal contributes to reduction of permeability the volumetric expansion in coal reduces the permeability with changing gas injection pressure during the initial confinement as the confining pressure is increased coal permeability reduces by one to two orders of magnitude finally an empirical relation accounting for the role of effective stresses and swelling on coal permeability is proposed for indian coals at lower effective stresses the logarithmic decline model is better suited while the exponential decline relationship fits the data better at effective stresses 12 mpa

a spring and wooded habitat at flk zinj and their relevance to origins of human behavior the 1959 discovery of the hominin fossil zinjanthropus boisei brought the world s attention to the rich records at olduvai gorge tanzania subsequent excavations of archaeological level 22 flk zinj bed i uncovered remains of homo habilis and a high density collection of fossils and oldowan stone tools the occurrence of this unusual collection of bones and tools at this specific location has been controversial for decades we present paleoecological data that provide new insights into the origin of flk zinj our recent excavations 200 m north of the site uncovered a 0 5 m thick tufa mound draped by tuff ic in the same stratigraphic horizon as level 22 stable isotope analyses indicate that the carbonates were deposited by a freshwater spring phytolith analysis of the waxy clay under tuff ic revealed abundant woody dicotyledon and palm phytoliths indicating that the site was wooded to densely wooded the time equivalency and close physical proximity of the two environments indicate the two are related this study has provided the first documented evidence of springs in bed i and these data have important implications for the interpretation of hominin behavior in meat acquisition and the ongoing debate on scavenging versus hunting

evidence for paleoseismic slip on a continental low angle normal fault tectonic pseudotachylyte from the west salton detachment fault ca usa abstract the potential of continental low angle normal faults lanf to nucleate large 6 0 m w earthquakes at low angles remains unclear despite much focused research we document evidence for ancient seismicity along a continental lanf detachment fault that formed and slipped at low angles and produced tectonic pseudotachylyte these thick and laterally persistent pseudotachylyte accumulations along the west salton detachment fault wsdf salton trough usa preserve convincing evidence for a frictional melt origin including spherulitic microlites ductile flow structures preservation of high temperature phases as clasts and injection veins cumulative thickness of pseudotachylyte along the fault ranges from 0 1 to 1 5 m and pseudotachylyte cataclasite in the fault core and damage zone are exposed along 2 6 km length of the fault reworked fragments of pseudotachylyte in cataclasites and multiple generations of cataclasites provide evidence for the preservation of multiple earthquake cycles the limited exposure

new excavations at the flk zinjanthropus site and its surrounding landscape and their behavioral implications renewed excavations at flk zinj and its surrounding landscape have yielded valuable information regarding its paleoecological situation and the prehistoric behavioral function of the site the density of materials at the main cluster of the site excavated by leakey contrasts with the bone and lithic scatters surrounding the site the location of flk zinj situated a few hundred meters away from a freshwater spring would have enabled hominins access to water plants and game the appeal of the spot for hominins also explained by the presence of a wooded habitat is confirmed by inferences of its redundant use prior and during the formation of the flk zinj paleosol as witnessed by materials accumulated both under and on the waxy clay deposit that constitutes the flk zinj stratum the single cluster nature of the site indicates central place behavior and evidence is provided that hominins occupied the site at a time of very low predation hazards in the area

evaluation indexes of coalbed methane accumulation in the strong deformed strike slip fault zone considering tectonics and fractures a 3d geomechanical simulation study both the deformation and rupture characteristics of rocks are related to geomechanics in this paper we identify the evaluation indexes related to coalbed methane cbm accumulation in strongly deformed strike slip fault zones considering tectonics and fractures we found that fault scale the fault combination the tectonic stress the preservation conditions and fractures all have important effects on the cbm distribution areas near the large scale opening faults are unfavourable to the preservation of coalbed methane the distribution of gas wells with different capacities is influenced by tectonic extension and convergence a 3d geomechanical method was used to analyse the influence of the ribbon effect of strike slip faults on the cbm distribution due to the influence of the ribbon effect the tectonic stress presents a plane in situ stress heterogeneity which in turn will affect the gas well productivity we also calculated the integrated rupture rate if to characterize the degree of tectonic fracture development in the target coal reservoir the appropriate fracture development degree can improve the petrophysical properties of the coal reservoirs while maintaining good storage conditions such that the gas wells can achieve a higher production capacity this study is of great significance for the enrichment of the geomechanical theory of oil and gas exploration

the flk zinj paleolandscape reconstruction of a 1 84 ma wooded habitat in the flk zinj amk ptk ds archaeological complex middle bed i olduvai gorge tanzania abstract we have analyzed the phytolith content of 37 samples from the paleosol capped by tuff ic dated 1 84 ma within middle bed i at olduvai gorge tanzania samples were obtained from different trenches sampling an area of about 25 ha to document the paleovegetation associated with the abundant faunal remains and hominin artifacts in flk amk ptk and ds sites the analysis reveals the abundance of globular granulate and forest indicator phytoliths from 3 to 86 relative to the total number of phytoliths in the assemblages attributed to woody plants and of short cell grass phytoliths up to 22 the presence of palm phytoliths up to 57 attests for meso haline soils in the area in agreement with the presence of the saline alkaline olduvai paleolake and one or more groundwater discharge areas freshwater springs and or wetland phytoliths provide botanical evidence for a mixed paleovegetation dominated by forest and woodland with patches of open spaces occupied by grasses prior to the deposition of tuff ic the presence of fern phytoliths in some assemblages suggest shaded and humid habitat which supports the presence of freshwater watercourses or springs that might have attracted hominins and other animals yet we have found that our phytolith extractions residues also include micrometric zeolites chabazite clinoptilolite phillipsite which attest that the phytolith signal in the zinj paleosols is certainly affected by dissolution this study completes the spatial analysis of the area and reveals that the wooded area extends north south and west of flk zinj with palm trees preferentially located in the periphery like the zinj amk and ds sites the phytolith inferred distribution of plants does not support the hypothesis that topography was influential in the location of these sites particularly given that trees and or shrubs were dominant all over rather it is the presence of freshwater ponds that seem to have been the attractive factor for hominins at this particular place and time

permeability of sub critical carbon dioxide in naturally fractured indian bituminous coal at a range of down hole stress conditions abstract understanding reservoir dynamics from a geotechnical and petrophysical perspective is essential for safe and steady fluid extraction transport or injection in the reservoir the recent approach on storage of anthropogenic greenhouse gases ghg for mitigation of climate change in the deep geologic reservoirs has led to fast paced research on resolving storage related issues a coal seam is one such target reservoir where co 2 may be injected for storage this may be coupled with the enhanced extraction of coalbed methane cbm it is known that the interaction of co 2 with coal induces hydro mechanical changes however detailed investigation is mandatory for site specific operation the lack of such studies on indian coal is the motivation for this research a naturally fractured coal specimen was chosen and the subcritical co 2 flow was maintained by monitoring the injection pressures and ambient temperature the variations in permeability under various scenarios were also investigated the results indicate that initial co 2 injection caused coal matrix swelling which took nearly 5 6 h of flow related sorption for maximum closure of the natural fractures linear variation in flow rate with the pressure gradient across the sample indicated laminar or darcian flow of co 2 through the coal fractures deeper coal seams have high confinements the co 2 permeability results for such in situ conditions indicated an exponential decline in naturally fractured coal due to increasing confining pressures the observed reduction of co 2 permeability with increase in gas inlet pressure is debated and may be attributed fully to matrix swelling or partly to the klinkenberg effect this study is vital for successful ghg sequestration in coal seams and for better understanding of the gas flow behaviour in the seams

transverse drilling induced tensile fractures in the west tuna area gippsland basin australia implications for the in situ stress regime abstract drilling induced tensile fractures ditfs have been interpreted on image logs from vertical wells in the gippsland basin offshore southeastern australia interpreted axial vertical ditfs have previously been well described worldwide we also interpret transverse horizontal ditfs which are horizontal fractures that are electrically conductive non planar bimodal and constrained to the tensile region of the wellbore elasticity theory predicts formation of both transverse and axial drilling induced tensile fractures ditfs in vertical wells depending on the magnitude of the principal in situ stresses pore pressure and mudweight drilling induced tensile fractures initiate in very specific stress environments axial ditfs can closely constrain a lower bound to the maximum horizontal stress s h max magnitude where the minimum horizontal s h min stress is known if transverse ditfs are observed they can constrain a lower bound to maximum and minimum horizontal stress magnitudes the observation of transverse ditfs on image logs can constrain the stress field to one on the border of strike slip and reverse faulting s h max s h min s v without requiring knowledge of the s h min or s h max magnitude the observation of transverse ditfs in the west tuna area combined with wireline log data leak off tests and pore pressure data are used to constrain the in situ stress tensor the interpreted in situ stress tensor lies on the border of a strike slip and reverse faulting regime s h max 40 5 mpa km s h min s v 21 mpa km interpreted data from leak off tests in the west tuna area confirm that s h min s v

tertiary strike slip faulting in southeastern mongolia and implications for asian tectonics abstract geologic maps have long portrayed the late cretaceous recent geologic history of southeastern mongolia as tectonically quiescent we present new data based on outcrop observations that indicate the northeast trending east gobi fault zone egfz was reactivated in the cenozoic as a sinistral strike slip fault system inversions of cenozoic fault slip data imply that faulting was associated with north northwest subhorizontal shortening and east northeast subhorizontal extension we propose that faulting is tertiary in age based on published interpretations of seismic reflection data which reveal that the mid cretaceous 100 95 ma unconformity is deformed by strike slip faults and based on field observation of strike slip faults and fracture sets that cut upper cretaceous and cenozoic strata but lack evidence for neotectonic activity published seismicity maps also appear to argue against significant quaternary faulting within the egfz these new data may lend credence to published models proposing a middle miocene or older kinematic linkage between the egfz and the altyn tagh fault in china the recognition that the egfz has a history of left lateral displacement in both the early mesozoic and cenozoic means that currently available estimates of offset based on displaced paleozoic rocks constrain total offset only this reactivation history supports the notion that inherited lithospheric structures are important in controlling the location and thus modes of intracontinental deformation in asia as a function of collisional far field effects and evolving boundary conditions of the pacific margin

freshwater limestone in an arid rift basin a goldilocks effect abstract the olduvai basin 3 s situated just west of the east african rift system in northern tanzania contains a two million year record of paleoclimate and paleoenvironmental change as well as a rich archive of vertebrate paleontology including hominins milankovitch precession cycles 20 kyr regulate the mean annual precipitation 250 700 mm yr and the 2500 mm yr evapotranspiration results in a negative hydrologic balance despite persistent aridity extensive deposits of freshwater limestone punctuate the stratigraphic record between 2 and 1 ma lake olduvai occupied the basin and its sediments are a proxy for climate driven cycles three limestones 1 84 1 80 and 1 36 ma in age which formed within lake margin floodplains adjacent to the lake were studied to determine their depositional environment using field relations sedimentary structures fossils petrography and stable isotope and major element geochemistry the three limestones are similar in that they contain peloidal micrite siliciclastic detrital grains and rhizoconcretions abundant faunal remains gastropods ostracods charaphytes and fish indicate that ponded water was relatively fresh and alkaline geochemical and stable isotope data indicate two types of groundwater sourced carbonate producing waters a deeper sourced fluid that was enriched in iron and manganese due to extended water rock interactions and a shallower groundwater that traveled through alluvial fan deposits regional faults tapped the deeper groundwater producing carbonate at spring sites while seeps associated with basinward changes in alluvial fan slopes drew on shallower groundwater sources isotope compositions indicate that fault related waters experienced some evaporation as water moved away from the spring sites while compositions of the seep related carbonate remained relatively constant pedogenic alteration and meteoric calcite cementation affected the carbonate when the spring and seep sites dried out secondary strontium rich dolomite precipitated within the limestones during burial under paleo lake olduvai sediments and fluids during periods of lake expansion integrating these data within the geological context of regional paleoclimatic and local environmental change indicates that the freshwater carbonates formed periodically when the conditions were just right i e a goldilocks effect carbonates near the basin center formed from groundwater flowing under a hydraulic head from faults or fractures during the falling limbs of milankovitch cycles when the lake was in recession carbonates near the basin margin formed from an increased rate of groundwater seepage that occurred only on the rising limbs of cycles in both contexts the continuous flow of groundwater with surface evaporation and co2 degassing optimizes the conditions for limestone formation in this arid environment these results help explain the formation of freshwater limestones in the rift basin link the carbonates to specific portions of milankovitch cycles and document that localized sources of potable water were present for use by hominins in olduvai gorge during an important period of human evolution

groundwater in the earth s critical zone relevance to large scale patterns and processes although we have an intuitive understanding of the behavior and functions of groundwater in the earth s critical zone at the scales of a column atmosphere plant soil bedrock along a toposequence ridge to valley and across a small catchment up to third order streams this paper attempts to assess the relevance of groundwater to understanding large scale patterns and processes such as represented in global climate and earth system models through observation syntheses and conceptual models evidence are presented that groundwater influence is globally prevalent it forms an environmental gradient not fully captured by the climate and it can profoundly shape critical zone evolution at continental to global scales four examples are used to illustrate these ideas 1 groundwater as a water source for plants in rainless periods 2 water table depth as a driver of plant rooting depth 3 the accessibility of groundwater as an ecological niche separator and 4 groundwater as the lower boundary of land drainage and a global driver of wetlands the implications to understanding past and future global environmental change are briefly discussed as well as critical discipline scale and data gaps that must be bridged in order for us to translate what we learn in the field at column hillslope and catchment scales to what we must predict at regional continental and global scales

paleoenvironmental reconstruction of a paleosol catena the zinj archeological level olduvai gorge tanzania abstract paleosols record paleoclimatic processes in the earth s critical zone and are archives of ancient landscapes associated with archeological sites detailed field micromorphologic and bulk geochemical analysis of paleosols were conducted near four sites at olduvai gorge tanzania within the same stratigraphic horizon as the zinjanthropus paranthropus boisei archeological site paleosols are thin

biogeochemical characterization of a lithified paleosol implications for the interpretation of ancient critical zones abstract modern soils are characterized by an array of physical chemical mineralogical and biological laboratory analyses of samples taken from horizons of pedogenic profiles in contrast fossil soils paleosols are typically characterized from assays of whole rock molecular oxides because of sample lithification where element sources are unconstrained here we for the first time subject a lithified paleosol to an array of modern soil analytical techniques and new pedotransfer functions providing a glimpse into the colloidal world of an ancient critical zone as an analog to research conducted on a network of modern critical zones this methodology provides a framework for decoding a previously unknown archive of terrestrial biogeochemical information at multiple temporal and spatial scales application to a paleosol within an early paleocene critical zone reveals that many biogeochemical properties have been preserved since burial that are similar to modern clay rich vertisols the measured and calculated physical properties of this paleosol include clay content and mineralogy bulk density and water retention available water capacity and coefficient of linear extensibility shrink swell potential the chemical properties include cation exchange capacity exchangeable cations base saturation and exchangeable sodium percentage the solution properties electrical conductivity and ph seem reasonable but are interpreted with less confidence because of their greater vulnerability to alteration from fluid flow new pedotransfer functions to reconstruct pre burial organic carbon and nitrogen contents provide invaluable information of organically derived nutrient content the sum of the measured properties of the early paleocene paleosol in context of reconstructed regional environmental conditions indicate the presence of a mid successional hardwood forest in a humid climate with high water holding capacity high nutrient retention and rapid flux of elements through biogeochemical cycling

analysis of continental shale gas accumulation conditions in a rifted basin a case study of lower cretaceous shale in the southern songliao basin northeastern china abstract the analysis of shale gas accumulation conditions is the basis of shale gas exploration previous research has mainly focused on the upper cretaceous shale in the songliao basin of northeastern china and few studies have analyzed the lower cretaceous shale in this area based on an integrated analysis of the sedimentary facies shale samples and seismic interpretation from the lower cretaceous shahezi yingcheng and denglouku formations of the fulongquan depression in the songliao basin the distribution of the shale and the generation accumulation and preservation conditions of the shale gas are evaluated and discussed core observations and sedimentary facies analysis show that the sedimentary facies types in the shahezi yingcheng and denglouku formations are mainly fan delta braided river delta sublacustrine fan and lacustrine facies the semideep lake shallow lake and delta front sedimentary subfacies are favorable for the deposition of shale the study of the shale distribution indicates that the shale was mainly deposited near the maximum flooding surface of the third order sequences and the shales in the shahezi and yingcheng formations are darker and thicker than those in the denglouku formation in addition the shale in this study area is laterally distributed in the depression belt and the steep slope belt near the boundary faults of the basin according to the geochemistry tests rock properties and mineral constituents the shales in the shahezi and yingcheng formations have favorable gas generation potential compared with the properties of the major gas producing shales in china and the united states the shales in the shahezi and the yingcheng formations are thick and have a favorable organic matter type high average organic matter abundance high organic matter thermal maturity that reached a high maturation stage high porosity and high gas contents these properties meet the standards of industrial exploitation and these shales can therefore be considered favorable targets for unconventional energy exploration

tectonics fracturing of rock and erosion 1 we argue that by fracturing rock not by raising it relative to base level tectonics plays its most important role in causing rapid incision of valleys and rapid erosion of hillslopes tectonic deformation riddles the upper crust with fractures which not only provide avenues for water flow and thus promote weathering and further disintegration of rock but also fragment bedrock into debris that is readily extracted and transported by surface processes bends in active faults require straining of adjacent rock masses aftershocks that occur subsequent to slip on primary faults reflect penetrative brittle deformation of the upper crust at least some aftershocks must nucleate or lengthen cracks which contribute to the comminution of these rock masses scaling rules suggest that dimensions of ruptures for very small m 2 earthquakes can be meters or less the gutenberg richter recurrence relationship implies that such earthquakes are common as high magnification seismographs in low noise environments confirm moreover large differences among fault plane solutions for aftershocks show that the small faults on which they occur are not parallel to one another some faults must intersect thus the upper crust in tectonically active regions should be fragmented into blocks down to the scale of boulders or smaller dismembered rock arrives at the earth s surface already prepared to be transported away as a corollary both deeply exhumed lower crust and posttectonic igneous rock never deformed under brittle conditions and not deformed recently should be less susceptible to detachment and subsequent transport than fractured rock

a review on the applications of image logs in structural analysis and sedimentary characterization abstract image logs provide important information on lithology sedimentary textures paleoflow directions fractures and in situ stress analysis lacking of criteria used for establishing the image log facies limits the applications of image logs in sedimentary reservoir interpretation this paper provides a thoroughgoing review focusing on the recent applications of borehole image logs for sedimentological and structural description and interpretation and aims to establish image log facies which can provide guidelines in sedimentary reservoir interpretation this paper firstly summarizes the principles and basic characteristics of various imaging logging tools and then briefly introduces the pre processing workflow of the image log data then the generated images are used for depth and orientation shifts of cores by calibrating individual sedimentary and structural features descriptive and concise image log facies are established based on combinations of image textures including dip type dip pattern and color scheme and the characteristics as well as physical criteria for each individual image facies are summarized the established image log facies are then interpreted in terms of structural and sedimentological features such as lithology sedimentary structures vugs fractures and faults the image log facies and its stacking patterns are then used to interpret the lithofacies associations by calibrating with cores and conventional logs natural fractures and induced fractures are recognized by image logs and the principles of breakouts and drilling induced fractures for in situ stress analysis are reviewed then the applications of image logs in investigation of fracture attitudes and states as well as in computation of fracture parameters are summarized the procedures to evaluate fracture effectiveness through image logs are discussed at last the application of image logs for structural dip analysis is reviewed and image logs are used for recognizing faults fracture sets and attitudes of stratum through the dip patterns the basic procedures for paleocurrent reconstruction which includes dip picking of cross beddings structural dip determination and structural dip removal are reviewed then the paleocurrent directions of the lower cretaceous bashijiqike formation in the kuqa depression were reconstructed which could help further understanding of the depositional systems this review will help extend the utility of image logs in interpreting small to large scale sedimentary and structural features and bridges the gaps between well log analysis and sedimentary and structural interpretation

lithological control on fracture cementation in the keuper marl triassic north somerset uk the spatial arrangement of gypsum veins as preserved natural hydraulic fractures have been characterized in the triassic keuper marl formation uk a caprock for hydrocarbon reservoirs and co 2 sequestration the marls cropping out are subdivided into five discrete fracture units based on the presence and abundance of gypsum veins the nodular gypsum in evaporite horizons provides excess gypsum for nodule rooted horizontal gypsum veins our petrographic observations demonstrate that the development of gypsum veins in beds lacking macroscopic evaporites is closely associated with disseminated gypsum cement in the marls we interpret that the gypsum veins in marl are sourced from disseminated gypsum cements in the host rocks based on stratigraphic correlations and much lower sr concentrations than gypsum nodules gypsum was transported to adjacent veins mainly through diffusion in the low permeability marls the localization of gypsum veins and varied sr concentrations of veins and nodules indicate that the diagenetic fluids are a mix of connate water with meteoric water rather than brines transported from evaporite beds along faults to non evaporite beds this results in the absence of gypsum fillings in fractures in rocks without primary gypsum cements the study implies that the cementation of natural fractures in low permeability rocks can highly depend on the presence of cement minerals in the host rock

buried paleoindian age landscapes in stream valleys of the central plains usa abstract a systematic study of late quaternary landscape evolution in the central plains documented widespread deeply buried paleosols that represent paleoindian age landscapes in terrace fills of large streams 5th order in alluvial fans and in draws in areas of western kansas with a thick loess mantle alluvial stratigraphic sections were investigated along a steep bio climatic gradient extending from the moist subhumid forest prairie border of the east central plains to the dry subhumid and semi arid shortgrass prairie of the west central plains radiocarbon ages indicate that most large streams were characterized by slow aggradation accompanied by cumulic soil development from ca 11 500 to 10 000 14c yr b p in the valleys of some large streams such as the ninnescah and saline rivers these processes continued into the early holocene the soil stratigraphic record in the draws of western kansas indicates slow aggradation punctuated by episodes of landscape stability and pedogenesis beginning as early as ca 13 300 14c yr b p and spanning the pleistocene holocene boundary the development record of alluvial fans in western kansas is similar to the record in the draws slow aggradation was punctuated by multiple episodes of soil development between ca 13 000 and 9000 14c yr b p in eastern kansas and nebraska development of alluvial fans was common during the early and middle holocene but evidence shows fan development as early as ca 11 300 14c yr b p buried soils dating between ca 12 600 and 9000 14c yr b p were documented in fans throughout the region in stream valleys across the central plains rapid alluviation after ca 9000 14c yr b p resulted in deeply buried soils that may harbor paleoindian cultural deposits hence the paucity of recorded stratified paleoindian sites in the central plains is probably related to poor visibility i e deep burial in alluvial deposits instead of limited human occupation in the region during the terminal pleistocene and early holocene the thick dark cumulic a horizons of soils representing buried paleoindian age landscapes are targets for future archaeological surveys

mesozoic basins in eastern china and their bearing on the deconstruction of the north china craton abstract mesozoic basins occur widely in the eastern block and the neighboring area of the north china craton including the bohai bay the jiaolai the hefei and the north yellow sea in the north and the jianghan and the subei south yellow sea basins to the south their spatial temporal framework is the consequence of the indosinian and yanshanian tectonic regimes in eastern china and record the events related to mesozoic deconstruction of the north china craton our results demonstrate that the mesozoic tectonic evolution of the eastern north china craton was related to both sub crustal delamination and intra crustal extrusion or escape tectonics thus we propose that the mechanism of uplift of the yanshanian north china plateau and related lithosphere thinning in the eastern north china craton were related to sub crustal delamination at depth however the different distribution patterns of the basins on both sides of the tan lu fault system as well as the co existence of both compressional and extensional basins in the mesozoic indicate that these were controlled by escape tectonics in different tectonic parts of the crust

c4 plant productivity and climate co2 variations in south central texas during the late quaternary abstract a continuous record of organic carbon 13c from a buried soil sequence in south central texas demonstrates 1 strong coupling between marine and adjacent continental ecosystems in the late pleistocene as a result of glacial meltwater entering the gulf of mexico and 2 ecosystem decoupling in the holocene associated with a reduction of meltwater and a shift in global circulation patterns in the late pleistocene reduction in c4 plant productivity correlates with two well documented glacial meltwater pulses 15 000 and 12 000 14c yr b p indicating a cooler than present adjacent continental environment increased c4 production between 11 000 and 10 000 14c yr b p suggests that the younger dryas was a warm interval responding to the diversion of glacial meltwater away from the mississippi river with waning meltwater flow c4 productivity generally increased throughout the holocene culminating in peak warm intervals at 5000 and 2000 14c yr b p shifts in the abundances of c3 c4 plants through the late quaternary show no correlation to ecophysiological responses to atmospheric co2 concentration

the last glacial termination a major puzzle of paleoclimatology is why after a long interval of cooling climate each late quaternary ice age ended with a relatively short warming leg called a termination we here offer a comprehensive hypothesis of how earth emerged from the last global ice age a prerequisite was the growth of very large northern hemisphere ice sheets whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation the southern hemisphere westerlies shifted poleward during each northern stadial producing pulses of ocean upwelling and warming that together accounted for much of the termination in the southern ocean and antarctica rising atmospheric co2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres

seasonal chemical and mineralogical variability of atmospheric particles in the coastal region of the northeast mediterranean abstract a time serial analysis of atmospheric particles collected since 1990 at a coastal site bordering the northeastern mediterranean sea shows that the collected samples display seasonal patterns in both concentration and color the 1990 91 and 1992 collections yield an annualised average of around 0 5 g day dust loading reducing to around 0 3 g day when the sea salt contribution is excluded the highest concentrations of atmospheric particles of continental origin for both natural e g fe mn and anthropogenic e g cd pb materials are observed between april and october and this variability is inversely related to the frequency and the amount of rainfall sea salt aerosol na contents do not follow this pattern but are related to local wind speeds trace elements in the dusts also display seasonal variations in enrichment factors ef with respect to average elemental abundances in crustal rocks the non enriched crustal elements appear to be indicators of long distance supply while the strongly enriched anthropogenic and moderately enriched suites of elements represents inputs from local or anomalous sources the similar morphology of quartz and calcite grains and the uniformity of the clay mineral assemblages in samples collected over a two year period strongly indicate a common source for the bulk of the atmospheric particles the dominant clay types palygorskite and smectite document a desertic source areas

the role of pressure solution seam and joint assemblages in the formation of strike slip and thrust faults in a compressive tectonic setting the variscan of south western ireland abstract the ross sandstone in county clare ireland was deformed by an approximately north south compression during the end carboniferous variscan orogeny the initial assemblage consists of mutually abutting orthogonal arrays of 170 oriented set 1 joints veins jvs and approximately 75 oriented set 1 pressure solution seams psss formed under the same stress conditions orientations of splay jvs and psss set 2 suggest a clockwise remote stress rotation of about 35 responsible for the contemporaneous shearing of the set 1 arrays among these nearly orthogonal strike slip faults the prominent set is sub parallel to set 1 jvs these faults are formed by the linkage of en echelon segments with broad damage zones responsible for right lateral offsets of hundreds of meters thrust faults with up to 30 m of offset initiate within shale horizons and follow either the psss in the sandstones or high angle shales within tilted sequences within the large thrust fault zones compartmentalised blocks of rocks are bounded by thrust faults segments with various dip angles strike slip and thrust faults are contemporaneous and owe their existence to initial weaknesses in the form of jvs and psss rather than by switching relative stress magnitudes and orientations associated with andersonian models of faults and related stress orientations

fractal analysis of tight shaly sandstones using nuclear magnetic resonance measurements assessing quantitatively the microscopic pore structures of porous rocks including irregularities of pore shapes and pore size distributions is becoming one of the most challenging efforts nuclear magnetic resonance nmr measurements were used to provide insights into the pore geometry pore size and shape and pore connectivity of the chang 7 tight shaly sandstones in situ permeability 0 1 md in ordos basin the incremental transverse relaxation time t2 distributions for the 100 brine saturated samples display unimodal and bimodal behaviors presenting a geometrical arrangement composed of small to large pore size domains the nmr parameters such as bulk volume irreducible bvi capillary and clay bound water free fluid index ffi movable water the value of t2 separating the bvi from ffi the amplitude weighted mean on a logarithmic scale t2gm and the value of t2 that shows the highest frequency on the t2 spectrum t2peak for each sample were determined then the fractal theory was adopted to quantitatively express the complexity and heterogeneity of the sandstones the results show that only minor primary intergranular porosity remains and variable amounts of micropores and secondary intragranular porosity with poor connectivity occur in the chang 7 tight shaly sandstones assuming spherical pores a new model to calculate the fractal dimension of pore structure from the nmr t2 distributions is proposed the fractal dimensions of all the samples are calculated and the accuracy of the proposed model is verified by the regression coefficients the microscopic pore structures are heterogeneous in these tight sandstones according to the high value of fractal dimensions micropores are the primary causes of heterogeneity in tight sandstones and samples with unimodal t2 distribution behaviors and high content of short components have the highest fractal dimension and heterogeneity the calculated fractal dimension is strongly correlated with t2peak and t2gm therefore the fractal model proposed in this study can be used to calculate the fractal dimensions and evaluate the heterogeneities of the porous rocks satisfactorily the fractal model proposed in this study helps to quantitatively assess the pore structures of tight sandstones using nmr measurements

an isochron method for cosmogenic nuclide dating of buried soils and sediments we describe an improved method for dating buried paleosols using measurements of the cosmic ray produced radionuclides 10be and 26al in quartz grains and apply it to a sequence of intercalated tills and paleosols in central missouri usa that record plio pleistocene advances of the laurentide ice sheet a buried paleosol implies a period of surface exposure and nuclide accumulation followed by burial and a halt to nuclide production if the paleosol is formed in a sedimentary unit such as till this unit may also have been emplaced with unknown 26al and 10be concentrations inherited from past surface exposure if the inherited nuclide concentrations are the same at all depths in the soil as is true for well mixed sediments such as till then the 26al and 10be concentrations at different depths in the paleosol will show a linear relationship the slope of this line depends on the duration of burial of the paleosol but not on the inherited nuclide concentrations or on the sample depths thus one can date strata overlying buried paleosols by measuring 26al and 10be at multiple depths in the paleosol and calculating the burial age of the paleosol from the resulting isochron we focus on applying this approach to till paleosol sequences but the basic idea of forming an 26al 10be burial isochron with a set of samples that share the same burial age but differ in other aspects of their exposure history applies to other stratigraphic settings as well the method yields ages for four tills in missouri that are stratigraphically consistent agree with paleomagnetic age constraints and show that ice advanced into missouri near 1 25 ma near 0 8 ma and twice between ca 0 4 and 0 2 ma

controls on fracture distribution in cretaceous sedimentary rocks from the isfahan region iran in this study relationships between fracture patterns lithology thickness diagenetic processes and grain size are evaluated within cretaceous sediments in two sections of dizlu and kolah ghazi of isfahan this study area was selected based on its outcrops of different rock units and its well developed tectonic fractures the fracture patterns within stratigraphic units of these sections are studied using geometrical and statistical analyses this study finds that variable fracture spacing and fracture spacing ratios can be affected by lithology thickness grain size of sediments and diagenetic processes a study of fracture stratigraphy based on fracture pattern evaluation within different cropped out sedimentary rocks can be used to improve understanding of the same types of sedimentary rock units below the surface or throughout other sedimentary basins consequently this could improve information regarding storage and fluid flow pattern throughout sedimentary rocks in different regions even for subsurface purposes

paleo critical zones windows into the changing life and landscapes during the quaternary period the critical zone cz as visualized in 1998 was a way to integrate the research of the four scientific spheres lithosphere hydrosphere biosphere and atmosphere at the surface of earth and to study the linkages feedbacks and record of processes rather than closeting studies by a variety of disciplines into their respective pigeonholes the cz perspective provides the symbiotic framework from which the tendrils of improved understanding can radiate outward to new disciplines and or feedback into the component disciplines during the last 2 decades cz research has been limited to the modern environment knowledge gained from the modern and the focus on interpreting ancient records allows for the development of paleo czs pczs pczs provide a powerful tool for improved understanding of the landscapes during the quaternary period and the response of this thin skin to glaciations sea level fluctuations and evolving life case studies from hominins in east africa and homo sapiens in the americas provide examples of the rich records stored in pczs as we move into the space age the cz can provide a platform from which to guide future exploration of the proto critical zones on the rocky planets and asteroids of our solar system

geomechanical simulation of low order fracture of tight sandstone abstract the core factors in the study of fractures within tight sandstone reservoirs are tectonics geomechanics and fluid mobility which are not independent but are coupled to each other in this paper taking the upper paleozoic gas reservoir within the low amplitude tectonic zone in the sulige gas field of the ordos basin as an example the developmental characteristics and geomechanical model of fractures and their relationships with the productivity of tight gas sandstone reservoirs were systematically studied the results show that this low amplitude structural zone develops mainly low order ruptures the paleotectonic stress field of the target layer in the yanshanian period was restored using a 3d finite element method the horizontal principal stresses exhibited stress diffusion and were affected by local low amplitude structures there was a positive correlation between h and h and h h was distributed primarily between 1 35 and 1 95 with an average of 1 62 the strain energy density u was calculated to quantitatively characterize the microfracture distribution of the target layer based on the principle of energy conservation there are certain positive correlations between u and the horizontal principal stresses the geostresses of high u regions underwent a certain degree of stress torsion which manifested as a stress deflection reaching up to 30 during stress propagation finally we proposed the concept of u value geomechanical sweet spots in a tight gas sandstone based on this criterion commercial gas wells can be effectively identified

geological controls on prediction of coalbed methane of no 3 coal seam in southern qinshui basin north china article i nfo in order to better understand the geological controls on coalbed methane cbm in southern qinshui basin sqb north china geological surveys and laboratory experiments including coal petrology analysis proximate analysis and methane adsorption desorption were conducted results show that the coals from the sqb contain 0 59 3 54 moisture 3 5 15 54 ash yield 73 62 88 92 fixed carbon and 2 14 4 04 hydrogen with c h ratios in the range of 19 96 36 25 the vitrinite reflectance ro m ranges from 1 95 to 3 49 the coals are composed of 18 5 97 4 vitrinite and 2 4 81 4 inertinite the geologic structures coal bearing strata and coal depositional environment were studied by both field geological research and laboratory tests a positive relationship is found between cbm content and basin hydrodynamics in which cbm easily concentrates in the groundwater stagnant zone because of the water pressure furthermore integrated geographical information system gis and analytical hierarchy fuzzy prediction method ahp were used to evaluate the cbm resources in the sqb the results show that the amount of cbm associated with the no 3 coal seam in the sqb is 3 62 10 11 m 3 t he cbm resource concentration gas in place per square kilometer in the sqb is in the range of 0 72 2 88 10 8 m 3 km 2 with an average of 1 21 10 8

predicting the regional distribution of fracture networks using the distinct element numerical method previous research has shown the importance of understanding the relationship between fault geometry and current applied tectonic stresses in the prediction of critically stressed faults and their propensity for fluid flow via generated fracture networks along and or around the fault plane this article summarizes research aimed at increasing this understanding by applying the distinct element method dem to predict stress within a rock mass generated by far field stress on seismically resolvable faults within a modeled area we showed that increases in differential over regional stress can be correlated with the presence of fractured rock as detected by petrophysical logs and core and drilling data a case study example is used to illustrate the methodology from the penola trough otway basin south australia modeled using two dimensional dem assuming a reasonable understanding of 1 rock properties 2 structure and 3 far field or regional stress then the technique described in this article provides a valid workflow to increase confidence in the prediction of the generation of fractures and their spatial distribution

fracture detection in oil based drilling mud using a combination of borehole image and sonic logs abstract the deeply buried 5 5 7 1 km lower cretaceous bashijiqike sandstones are important fractured reservoirs in the kuqa depression in these high temperature high pressure drilling environments oil based muds are used to limit drilling risks and improve efficiency making facture detection using resistivity based image logs difficult the maximum horizontal stress sh max trends close to north south 0 10 based on orientations of the drilling induced fractures and borehole breakouts core descriptions thin sections and image logs used to describe the fractures in the bashijiqike sandstone reservoirs show that opening mode natural fractures are common and the fractures range from fully open to sealed by calcite and clay minerals the open fractures are dominantly steeply dipping or vertical and primarily strike north south locally horizontal fractures or fractures with low angle dip are detected we compare fracture visibility on image logs acquired in the same ks 2 2 12 key well in oil based mud and water based mud fmi hd logs successfully detect large 0 1 mm aperture vertical fractures in oil based mud better than obmi image logs and the two imaging tools have a similar ability in detecting the high dip angle fractures since the ubi tool is not affected by oil based muds most of the fractures can be picked out on ubi images minor negative deviations of bulk density could be observed in fractured zones and the presence of fractures obviously causes an increase in sonic transit time full waveforms from dsi tools combined with electrical image logs detect fractured zones both the velocity and amplitude of the sonic waves are sensitive to fractures and the fractured zones could be identified according to the attenuation of stoneley waves the combination of cores image logs and full wave sonic logs offers comprehensive detection of fractures in oil based mud environments

paleoenvironmental reconstruction and water balance of a mid pleistocene pluvial lake dakhleh oasis egypt mid pleistocene lacustrine sediments exposed as erosional remnants in dakhleh oasis in the western desert of egypt provide evidence for a more humid climate than that which persists today the sediments range in facies from palustrine to fully lacustrine and generally reflect an increase in water depth upward through the strata ironstone spring deposits associated with the lacustrine sediments and modern artesian discharge in the oasis indicate that nubian aquifer water was probably an important component of the water balance but the high carbonate content of the lake sediments requires the input of surface drainage derived from the nearby limestone capped libyan plateau although definitive shorelines have not been observed a maximum lake size of 1735 km2 is derived from extrapolation of the elevations of the deposits onto the modern deflated topography theoretical water balance modeling suggests that in addition to the discharge derived from the nubian aquifer 410 860 mm yr of rainfall would be required over the dakhleh oasis drainage basin in order to maintain the lake at hydrologic steady state the persistence of climatic and hydrologic conditions amenable to maintaining a shallow freshwater lake would have allowed the region to be inhabited by a savanna fauna as well as early human groups

characterizing the pore structure in the silurian and permian shales of the sichuan basin china abstract nitrogen sorption and mercury intrusion methods were applied to characterize the pore structure of the lower silurian shales of the long ma xi formation and upper permian shales of the da long formation in the sichuan basin the results indicate that the specific surface areas and porosities of the silurian shales are in the range of 17 83 29 49 m 2 g and 3 65 18 26 respectively the silurian shales show a bimodal pore size distribution and consist of both micropores and nanopores ranging from 30 to 60 m and 1 7 20 nm respectively a strong positive linear correlation between the surface areas and total organic carbon content toc suggests that the organic matter contributes mostly to the amount of specific surface area of the silurian shales whereas the contribution of clay minerals appears to be negligible the organic matter also accounts for 50 70 of the porosity in the silurian shales soluble organic matter in the form of bitumen however has a negative impact on the surface area and porosity of the silurian shales and reduce the amount of surface area and porosity in these shales for the permian shales their surface area and porosity are lower than those of the silurian shales and are in the ranges of 2 20 3 52 m 2 g and of 1 30 4 15 respectively the pore size distribution of the permian shales shows a unimodal pattern of micropores in a size range of 30 60 m their toc and clay mineral contents display poor correlation with the surface areas and suggest that both the organic matter and clay minerals have very low surface areas a clear negative correlation between the porosity and toc in the permian shales indicates that organic matter contributes little or insignificantly to the porosity due to poorly developed organic pores in kerogen because the permian shales are much lower in thermal maturity than the silurian shales furthermore there is a consistent negative linear correlations between the bitumen content and the porosity for both the permian shales and silurian shales and indicate that the bitumen may significantly reduce the porosity of the shales by occupying the pore spaces in the mineral and organic matrix finally it is clear that the lower silurian shales have a greater shale gas potential than the upper permian shales do based on their surface area and porosity

inward migration of faulting during continental rifting effects of pre existing lithospheric structure and extension rate abstract lithospheric scale analogue models are used to analyse the parameters controlling the typical evolution of deformation during continental narrow rifting characterized by early activation of large boundary faults and basin subsidence followed by localization of tectonic activity in internal faults at the rift axis integration of current and previous experiments shows that the evolution of deformation in particular the amount of extension needed for the abandonment of boundary faults and migration of deformation to in rift faults is dependent on at least five boundary conditions i thickness of brittle layers including syn rift sediments ii thickness of ductile layers iii extension rate iv width of the weak zone localizing extension and v rift obliquity with respect to the extension direction an increase in the amount of extension corresponding to the inward migration of faulting i e a longer phase of slip on boundary faults is observed for a an increase in the thickness of both brittle and ductile crustal layers and syn rift sediment accumulation b a decrease in extension rate and width of the weak zone and c a decrease in rift obliquity a unified account of these correlations is presented based on the hypothesis that fault migration occurs when boundary faults can no longer accommodate the imposed bulk extension leading to time space variations of internal strain and strain rate and consequently stress in the ductile layers which overcome the total resistance of brittle layers to thoroughgoing faulting

superposed deformation and inherited structures in an ancient dilational step over zone post mortem of the rengali province india abstract in the eastern indian shield a dextral strike slip system juxtaposed the archaean singhbhum province against the proterozoic eastern ghats belt at 490 470 ma two wnw ese trending strands of the strike slip system enclose a multiply deformed d1 to d3 intervening domain called the rengali province with d3 representing dextral shearing in a granulite lens within the province an early fabric sgr was deformed by an amphibolite facies d1 d2 deformation continuum in the late archaean time forming cylindrical folds in the surrounding quartzofeldspathic gneisses quartzites and mica schists of the province superimposition of syn d3 shortening on d1 d2 folds generated complex non cylindrical geometries the granulites escaped d3 strain microstructures in the province bounding shear zones confirm that d3 deformation was associated with mylonitization dynamic recrystallization and greenschist facies metamorphism in the quartzites syn d3 folds can be correlated with rotation of d1 d2 structures through the shortening zone of bounding dextral shears since the province bounding shears form a step over zone the structural complexity within the rengali province arises from superposition of syn d3 shortening structures on initially asympathetically oriented inherited cylindrical d1 d2 folds hydrous fluid channeling causing greenschist facies metamorphism and quartz vein emplacement accompanied d3 as the step over zone was dilational in nature

extension structural records in the qinshui basin north china since the late mesozoic qinshui basin has abundant coal bed methane resources and has been undergoing intensive intracontinental rifting and extensional tectonics since the late mesozoic some fractures which were previously considered as conjugate shear fractures are interpreted as joint sets with extension characteristics for the first time in the qinshui basin the widely distributed joint sets with stable attitudes can be divided into four sets this paper presents updated results of fault slip datasets collected in different zones of the qinshui basin and addresses the changes in the direction of extensional stresses since the late mesozoic based on the analysis results of the slickenline of normal faults joint sets in the field and focal mechanism solutions data from the shanxi province we identified four main directions of extension since the late mesozoic in the qinshui basin 1 early cenozoic ene wsw 85 15 extension 2 palaeogene nne ssw 30 5 extension 3 miocene nw se 135 15 extension and 4 late pliocene quaternary nnw sse 170 5 extension the principal extension directions in the qinshui basin seem to have undergone a counterclockwise rotation from the early cenozoic to the miocene we prefer that the extension deformation events in the qinshui basin since the late mesozoic were mainly related to the back arc spreading induced by westward subduction of the paleo pacific plate under the eurasian continent

the upper paleozoic coalbed methane system in the qinshui basin china the coalbed methane resource is very abundant in qinshui basin 3 28 1012 m3 114 tcf the investigation on the upper paleozoic coalbed methane system is a guide to the exploration and development of coalbed methane the upper paleozoic coalbed methane system in the qinshui basin is sealed by a low permeability roof and floor strata comprising mudstone siltstone and bauxite of the carboniferous benxi formation and the permian shanxi and xiashihezi formations the overburden is the lower permian xiashihezi formation and the upper permian triassic and middle jurassic clastic deposits the source and reservoir rocks are the carboniferous permian coal seams the hydrocarbon generation of the source rocks reached its first peak in the late triassic the highest maturity was about ro 1 2 under a normal paleogeothermal gradient 2 3c 100 m 1 1 1 7f 100 ft a tectonic thermal event during the jurassic and cretaceous yanshanian orogeny enhanced the coal maturity and caused a second peak of hydrocarbon generation varying igneous intrusions caused the coal maturity to be higher in the southern northern and eastern parts of the qinshui basin instead of the central and western parts the highest maturity was greater than ro 4 in the jincheng area the migrated thermogenetic coalbed methane accumulated in the reservoirs in which abnormally high reservoir pressure exists locally under the hydrodynamic drive because of the different hydrodynamic background and sealing condition the distribution of coalbed methane content is inhomogeneous the reservoir is undersaturated with gas in most areas based on the coalbed methane system investigation we assessed the coalbed methane producibility in different parts of the qinshui basin and the major producibility area is in the southern part of the basin

fractures in continental shale reservoirs a case study of the upper triassic strata in the se ordos basin central china fractures are important for shale gas reservoirs with low matrix porosity because they increase the effective reservoir space and migration pathways for shale gas thus favouring an increased volume of free gas and the adsorption of gases in shale reservoirs and they increase the specific surface area of gas bearing shales which improves the adsorption capacity we discuss the characteristics and dominant factors of fracture development in a continental organic matter rich shale reservoir bed in the yanchang formation based on observations and descriptions of fracture systems in outcrops drilling cores cast thin sections and polished sections of black shale from the upper triassic yanchang formation in the se ordos basin detailed characteristics and parameters of fractures analyses and tests of corresponding fracture segment samples and the identification of fracture segments with normal logging the results indicate that the mineral composition of the continental organic matter rich shale in the yanchang formation is clearly characterized by a low brittle mineral content and high clay mineral content relative to marine shale in the united states and china and mesozoic continental shale in other basins the total content of brittle minerals such as quartz and feldspar is c 41 with quartz and feldspar accounting for 22 and 19 respectively and mainly occurring as plagioclase with small amounts of carbonate rocks the total content of clay minerals is high at up to 52 and mainly occurs as a mixed layer of illite smectite i s which accounts for more than 58 of the total clay mineral content the upper triassic yanchang formation developed two groups of fracture joint systems a nw se trending system and near e w trending system multiple types of fractures are observed and they are mainly horizontal bedding seams and low dip angle structural fractures micro fractures are primarily observed in or along organic matter bands shale fractures were mainly formed during late jurassic late early cretaceous time under superimposed stress caused by regional wnw ese trending horizontal compressive stress and deep burial effects the extent of fracture development was mainly influenced by multiple factors tectonic factors and non tectonic factors such as the lithology rock mechanical properties organic matter abundance and brittle mineral composition and content specifically higher sand content has been observed to correspond to more rapid lithological changes and more extensive fracture development in addition higher organic matter content has been observed to correspond to greater fracture development and higher quartz feldspar and mixed layer i s contents have been observed to correspond to more extensive micro fracture development these results are consistent with the measured mechanical properties of the shale and silty shale the observations of fractures in cores and thin sections from more than 20 shale gas drilling wells and the registered anomalies from gas logging

evidence for late pleistocene climate changes from buried soils on the southern slopes of mt kilimanjaro tanzania abstract the distribution of the altitudinal vegetation zones on the slopes of mt kilimanjaro is well known but no reliable data are available about the vegetation shifts during the quaternary here i present palaeopedological results elemental biomarker stable isotope and radiocarbon analyses indicating that the frequently occurring buried black a horizons in the montane forest belt are developed under ericaceous vegetation since erica species are not abundant at this altitude nowadays but are characteristic for the sub alpine zone the palaeosols reflect palaeoclimatically driven fluctuations and changes of the vegetation zones on mt kilimanjaro the downhill descent of the ericaceous belt coincided with cold and dry periods like the late glacial and the last glacial maximum older palaeosols document that such events also took place during the marine isotope stages 3 and 4

lithospheric structure variations between the eastern and central north china craton from s and p receiver function migration abstract i imaged the lithospheric structure beneath the bohai bay basin bbb in the eastern north china craton ncc and the taihang mountains tm and areas further to the west in the central ncc by applying the wave equation migration technique to both the s and p receiver functions rfs collected in this region the data images and synthetic modeling results indicate that s rf imaging is more appropriate than p rf imaging for mapping lithospheric discontinuities especially the lithosphere asthenosphere boundary lab in various types of regions even directly applicable to basin areas that are covered by thick sediments the constructed s rf images show that the lithospheric thickness of the study region is highly variable the imaged lab is on average 80 km beneath the bbb and displays obvious undulations from 120 km under the tm to 40 km under the mountain areas in the central ncc consistent with previous p rf imaging results the observed structural differences between the eastern and central ncc are likely associated with different lithospheric tectonics in these two regions while widespread lithosphere reactivation and extension in the eastern ncc during the late mesozoic time was plausibly responsible for both the thinned crust and lithosphere in the bbb lithospheric thinning in the central ncc may be equally heterogeneous but less significant and probably occurred mainly in cenozoic such a process may have given rise to the highly variable present day lithospheric thickness in this region however it probably did not noticeably affect the overlying crust that was reported to have thickened in response to the early magmatic underplating in the mesozoic time the different tectonic processes in the eastern and central ncc may have induced the formation of the nsgl which likely serves as a major tectonic boundary separating the two regions of contrasting lithospheric structures at present

deep burial diagenesis and reservoir quality evolution of high temperature high pressure sandstones examples from lower cretaceous bashijiqike formation in keshen area kuqa depression tarim basin of china the deep high temperature high pressure lower cretaceous bashijiqike sandstone buried to depths as great as 6 5 7 1km is an important natural gas reservoir in keshen gas field kuqa depression of the tarim basin reservoir quality is a critical risk factor in the development of these ultradeep reservoirs integrated approaches incorporating routine core analyses mineralogical petrographic and geochemical analyses have been used to investigate the diagenetic history of these rocks and their impact on reservoir quality with the aim to unravel the mechanisms for maintaining anomalously high porosities in sandstones that are buried to such a great depth these sandstones are dominantly fine to medium grained moderately to good sorted lithic arkoses and feldspathic litharenite most primary pores have been lost by mechanical compaction or carbonate cementation and the reduction of porosity by mechanical compaction was more significant than by cementation dissolution of framework grains contributed to the enhancement of reservoir quality eogenetic diagenetic alterations mainly include mechanical compaction precipitation of calcite cements and grain coating clays mesogenetic diagenesis is characterized by dissolution of framework grain by organic acids and subsequent precipitation of clay minerals and quartz infiltration of meteoric water related to teleodiagenesis would result in dissolution of the framework grains the meteoric leaching events during teleodiagenesis are of great importance for the bashijiqike sandstones grain coating clay minerals mixed layer illite smectite clays help to preserve porosity at depth by retarding quartz cementation and pressure solution the unique burial regime as early stage shallow burial with late stage rapid deep burial contributes to porosity preservation in eodiagenesis fluid overpressure caused by intense structural compression in the middle himalayan movement retarded compaction and helped preserve porosity in the late rapid deep burial stage anomalously high porosities are mainly found in medium grained good sorted sandstones with grain coating clays but with low clay and carbonate cement content of which the porosity is preserved primarily and enhanced secondarily the lowest porosities are associated with sandstones that are tightly compacted or cemented with carbonates or rich in detrital matrix porosity depth trends may vary significantly with lithofacies due to its differences in textural and compositional attributes five lithofacies are defined in terms of detrital composition and texture type and degree of diagenesis the reservoir quality prediction models of various lithofacies are constructed and the results of this study provide insights into mechanisms for maintaining anomalously high porosity and permeability in high temperature high pressure sandstone reservoirs and may help explain hydrocarbon distribution

paleosols and paleoenvironments of early mars fluviolacustrine sediments filling gale crater on mars show two levels of former exposure and weathering that provide new insights into late noachian 3 7 0 3 ga paleoenvironments of mars diagnostic features of the two successive paleosols in the sheepbed member include complex cracking patterns of surface dilation peds and cutans a clayey surface a horizon deep sand filled cracks with vertical lamination sand wedges and replacive sulfate nodules aggregated into distinct bands gypsic by horizon above bedded sandy layers sedimentary c horizon shallow gypsic horizon periglacial sand wedges and limited chemical weathering are evidence of a hyperarid frigid paleoclimate and this alternated with wetter conditions for the lacustrine parent materials in gale crater during the late noachian depletion of phos phorus vesicular structure and replacive gypsic horizons of these martian paleosols are fea tures of habitable microbial earth soils on earth and encourage further search for definitive evidence of early life on mars

learning to read the chemistry of regolith to understand the critical zone the base of the critical zone includes the mantle of altered soil and rock regolith that changes in response to chemical physical and biological processes occurring at earth s surface these processes are recorded in the chemistry of the regolith and this long term record can often be deciphered for example on eroding ridgetops where flows are generally downward for water and upward for earth material element concentrations vary with depth to constitute depletion addition depletion enrichment and biogenic profiles models can be used to explore the records of mineral dissolution atmospheric input coupled dissolution precipitation and biolifting documented in these profiles these models enable interpretation of the effects of time climate rates of erosion and human and other biotic impacts on the profile patterns by testing quantitative models against the long term record of information in regolith we will learn to project changes arising from human and natural perturbations of the critic