unsaturated zone hydrostratigraphies a novel archive of past climates in dryland continental regions natural chemical tracers contained in moisture within unsaturated zone usz sediments have very significant potential as a novel archive of past climate and palaeoenvironmental conditions in dryland environments however this potential has yet to be fully realised the tracer signature is established in the near surface zone with evapotranspiration processes enriching the concentration inherited from input from atmospheric deposition predominantly rainfall this pore moisture tracer signature then moves vertically through the usz sediments toward the water table producing a hydrostratigraphy that with increasing depth records changes to the moisture balance at the surface through time the small fluxes of water through the usz in dryland climates means that this hydrostratigraphy approach is particularly valuable in these environments for providing climate records longer than the instrumental data period this paper sets out the current state of the art in the use of the usz as an archive we explain the nature of the usz the basis of the tracer technique and also the field and sampling methodologies employed examples of application worldwide by broad geographic region are also evaluated this shows that the usz hydrostratigraphy approach can be used across three key timescales i decadal to multi decadal resolution records covering hundreds of years that provide information about recent climate fluctuations and patterns of land use change ii multi decadal through to millennial scale length records which may record wetter and drier events down to decadal scale resolution and iii last interglacial through to the holocene records of lower resolution that indicate broad shifts over multi millennial timescales we also explore the questions and challenges surrounding the depositional flux of tracer inputs and the extent to which infiltration is non uniform before setting the agenda for their future potential use alongside related proxies for palaeohydrology

tree ring δ18o in southwestern china linked to variations in regional cloud cover and tropical sea surface temperature in this paper we present the first annual oxygen isotope 8180 record 1902 to 2004 from the latewood cellulose of trees growing in a temperate moist forest in southwestern china tree ring delta o 18 ranges from 12 8 to 18 6 parts per thousand and averages 15 2 parts per thousand delta o 18 in the latewood negatively correlates with total cloud cover relative humidity and precipitation during the moist months august to october from 1951 to 2004 and to a lesser extent positively correlates with the temperature in june spatial correlation analysis revealed that tree ring latewood delta o 18 is more strongly related to variability in regional cloud cover and precipitation in autumn tree ring delta o 18 negatively correlates with the indices of the indian summer monsoon 1948 to 2004 the western north pacific monsoon 1948 to 2004 and with the east asian summer monsoon 1902 to 2000 suggesting that these monsoons strongly influence the regional climate under global warming of last century we found a strong inverse correlation between tree ring delta o 18 and the southern oscillation index in different periods indicating a complex association between the el nino southern oscillation and the regional climate which in turn affects tree ring delta o 18 correlation with the global sea surface temperature sst indicates that climatic conditions in the indian ocean might play a dominant role in modulating cloud cover and precipitation over the study region during the monsoon seasons we also found a significant correlation between tree ring delta o 18 and sst over the western north pacific ocean our results suggest strong links between tropical oceans and an enso like climate with the oxygen isotope sources and discrimination for trees in the study region c 2011 elsevier b v all rights reserved

glacial stage ice core records from the subtropical dunde ice cap china the first ice core record of both the holocene and wisconsin wiirm late glacial stage lgs from the subtropics has been extracted from three ice cores to bedrock from the dunde ice cap on the north central qinghai tibetan plateau ice thicknesses at the ice cap summit average 138 m the bedrock surface is relatively flat surface and basal temperatures are 7 3 and 4 7 c respectively and the ice cap exhibits radial flow away from the summit dome these records reveal a major change in the climate of the plateau 10 000 years ago and suggest that lgs conditions were colder wetter and dustier than holocene conditions this is inferred from the more negative 6180 ratios increased dust content decreased soluble aerosol concentrations and reduced ice crystal sizes which characterize the lgs part of the cores total b radioactivity from shallow ice cores indicates that over the last 24 years the average accumulation rate has been 400 mm a 1 at the summit the ice cores have been dated using a combination of annual layers in the insoluble dust and 6180 in the upper sections of core visible dust layers which are annual and ice flow modeling the oxygen isotope record which serves as a temperature proxy indicates that the last 60 years have been the warmest in the entire record

predicting of uniaxial compressive strength of some igneous and metamorphic rocks by block punch index and cylindrical punch index tests abstract uniaxial compressive strength ucs of rock materials is a crucial parameter in designing of engineering structures to be constructed in on rock masses although the suggested methods for determination of ucs are well known and required relatively simple procedures preparation of standard core specimens may not be easy for rock materials of heavily jointed rock and or thinly stratified rock masses in order to overcome these difficulties to be encountered during sample preparation the studies on the alternative equations based on results of simple index tests for predicting of ucs of rock materials have been popular a linear correlation with conversion factor of 5 1 was suggested in literature for predicting of ucs from block punch index bpi considering a wide variety of rock types in this study the relations were investigated to be used for predicting of ucs from bpic and also cylindrical punch index cpi based on experimental studies employed on seven different igneous and metamorphic rocks collected from different locations in hamedan province west of iran the linear regression analysis showed that the conversion factor between ucs and bpic was obtained as 5 7 for the tested rocks which is already higher than the proposed value of 5 1 a conversion factor equal to 7 4 was derived for relation between ucs and cpi in addition the prediction performance of some well known equations on the test results obtained in this study for determination of ucs from bpic and also cpi were evaluated moreover the coefficients of determination of logarithmic and power functions were higher than any other functions for ucs bpic and ucs cpi relations respectively

neotectonic evolution of the brazilian northeastern continental margin based on sedimentary facies and ichnology abstract quaternary post barreiras sediments are widespread along brazil s passive margin these deposits are well exposed in the onshore paraiba basin which is one of the rift basins formed during the pangean continental breakup in this area the post barreiras sediments consist of sandstones with abundant soft sediment deformation structures related to seismicity contemporaneous with deposition the trace fossils thalassinoides and psilonichnus are found up to 38 m above modern sea level in sandstones dated between 60 0 1 4 and 15 1 1 8 ka the integration of ichnological and sedimentary facies suggests nearshore paleoenvironments such deposits could not be related to eustatic sea level rise as this time coincides with the last glaciation hence an uplift of 0 63 mm yr or 1 97 mm yr if sea level was 80 m lower in the last glaciation would have been required to ascend the post barreiras sediments several meters above the present day sea level during the last 60 ka this would suggest that the post rift stage of the south american eastern passive margin may have experienced tectonic reactivation more intense than generally recognized although more complete data are still needed the information presented herein may play an important role in studies aiming to decipher the quaternary evolution of this passive margin

ichnology of fair weather and storm deposits in an upper cretaceous estuary eutaw formation western georgia usa abstract exposures of the eutaw formation in western georgia eastern gulf coastal plain usa were examined to evaluate the ichnologic signature of fair weather and storm related strata deposited within the central bay of a late cretaceous estuary ichnofabrics of fair weather sandy muds and muddy sands compare favorably with those of previously well documented estuarine facies of the cretaceous western interior foreland basin trace fossil assemblages vary with sediment texture reflecting proximity to sources and frequency of deposition of sands but they generally are dominated by simple structures attributed to activities of trophic generalists terebellina teichichnus and planolites although this likely reflects environmental stress associated with estuarine dynamics the degree to which salinity fluctuations governed trace fossil assemblages cannot be confidently assessed trace fossil assemblages in estuarine storm sands also are variable distal central bay tempestites include fair weather ichnofossil suites however commonly in proximal parts of the central bay rapid event related accumulation of suspended clays immediately followed sand emplacement and thereby precluded burrowing of sands by subsequently established fair weather organisms by virtue of proximity to fluvial point sources and or salinity gradients this phenomenon may be unique to and diagnostic of certain estuarine settings ophiomorpha is nearly ubiquitous in storm sands normally attributed to post storm colonization by opportunistic organisms these burrow systems instead may represent the work of storm transported crustaceans

uplift history of the central and northern andes a review the elevation of the andean cordillera is a crucial boundary condition for both climatic and tectonic studies the andes affect climate because they form the only barrier to atmospheric circulation in the southern hemisphere and they intrigue geologists because they have the highest plateau on earth formed at a noncollisional plate margin the altiplano puna yet until recently few quantitative studies of their uplift history existed this study presents both 1 a review of the quantitative paleoelevation estimates that have been made for the central and colombian andes and 2 an examination of the source and magnitude of error for each estimate in the central andes paleobotanical evidence suggests that the altiplano puna had attained no more than a third of its modern elevation of 3700 m by 20 ma and no more than half its modern elevation by 10 7 ma these data imply surface uplift on the order of 2300 3400 m since the late miocene at uplift rates of 0 2 0 3 mm yr paleobotanical and geomorphological data suggest a similar uplift history for the eastern cordillera namely no more than half the modern elevation present by 10 ma no evidence exists for an exponential increase in uplift rate as has been interpreted from fissiontrack data these uplift rates mostly reflect mean surface uplift rather than rock uplift that is uplift of material points because little dissection of the western eastern cordillera has occurred south of lat 19 s and of the altiplano puna thus the central andean plateau appears to be young in the colombian andes paleobotanical data imply rapid uplift of the eastern cordillera between 2 and 5 ma at rates on the order of 0 6 3 mm yr however some of this uplift is likely rock uplift due to erosion driven isostatic rebound rather than mean surface uplift

stable isotope time series and precipitation origin from firn core and snow samples altai glaciers siberia in the summers of 2001 and 2002 glacio climatological research was performed at 4110 4120ma s l on the belukha snow firn plateau siberian altai hundreds of samples from snow pits and a 21m snow firn core were collected to establish the annual seasonal monthly depth accumulation scale based on stable isotope records stratigraphic analyses and meteorological and synoptic data the fluctuations of water stable isotope records show well preserved seasonal variations the d 18 o and dd relationships in precipitation snow pits and the snow firn core have the same slope to the covariance as that of the global meteoric water line the origins of precipitation nourishing the belukha plateau were determined based on clustering analysis of d 18 o and d excess records and examination of synoptic atmospheric patterns calibration and validation of the developed clusters occurred at event and monthly timescales with about 15 uncertainty two distinct moisture sources were shown oceanic sources with d excess 12 two thirds of the annual accumulation was from oceanic precipitation of which more than half had isotopic ratios corresponding to moisture evaporated over the atlantic ocean precipitation from the arctic pacific ocean had the lowest deuterium excess contributing one tenth to annual accumulation

temporal variations of accumulation and temperature during the past two centuries from belukha ice core siberian altai 1 the temporal variation of accumulation and temperature in the siberian altai were investigated using a 86 m long ice core from belukha glacier 49 48 26 n 86 34 43 e 4062 m a s l covering the time period 1816 to 2001 as temperature sensitive parameters the melt percent profiles and the stable oxygen isotopes 18o were evaluated representing summer season and march to november temperatures respectively the accumulation record showed no long term trend and only minor deviations of limited duration from the accumulation average of 0 5 m water equivalent y weq y were observed in contrast the two temperature proxies indicate a strong warming trend in the order of 1 6 0 4 c and 1 7 1 1 c over the last century inferred from melt percentages and the 18o record respectively and 2 5 1 7 c since the mid 19th century inferred from the 18o record this reflects an amplified regional climate response following the little ice age lia as compared to the northern hemisphere average most probably caused by the strong continentality of the siberian altai region the sudden onset of large melt features since 1988 indicates that the upper reaches of belukha glacier are experiencing a change from the recrystallization to the cold infiltration zone that now allows for multiannual percolation of meltwater implying that the conservation of accumulation and geochemical properties including those providing temperature proxies is currently endangered

the northeast brazilian rift system the northeast brazilian rift basins provide important data critical to the understanding of continental rifting processes associated with the opening of the south atlantic these basins represent the locus of intersection of the southern and equatorial branches and some basins yield substantial chronostratigraphic data that constrain the temporal and spatial interaction of the rift phases similar data are not found in its counterpart in africa especially for the neocomian these early cretaceous rift basins of northeast brazil illustrate key three dimensional geometries of intracontinental rift systems mainly controlled by the basement structural framework during the main rift phase syn rift ii neocomian early barremian extensional deformation was distributed over three main rift axes 1 the gabon sergipe alagoas gsa trend 2 the reconcavo tucano jatoba rtj trend and 3 the cariri potiguar cp trend during this phase extensional deformation jumped west from the easternmost basins gsa trend to a series of ne trending intracratonic basins rtj and cp trends characterized by a set of asymmetric half grabens separated by basement highs transfer faults and or accommodation zones these basins are typically a few tens of kilometers wide and trend ne sw roughly perpendicular to the main extension direction during the neocomian preexisting upper crustal weakness zones like the dominantly ne sw trending shear zones of the brazilian pan african orogeny controlled the development of intracrustal listric normal faults internal transverse structures such as transfer faults and accommodation zones were also controlled by the local basement structural framework the megashear zones of pernambuco brazil and ngaundere africa seem to have behaved like a huge accommodation zone accommodating extensional deformation along the rtj gsa trends with simultaneous extension along the cp trend during the late barremian syn rift phase iii a significant change in rifting kinematics occurred when the cp trend was aborted and major rifting initiated at the equatorial branch during the aptian while the equatorial branch and benue trough africa experienced the main rift phase the rtj trend was aborted and the gsa trend developed a transitional phase between the rift and drift stage the gsa trend and the offshore potiguar basin represent the site of continued evolution into passive margin basins following the main rift episode

the influence of foliation on point load strength anisotropy of foliated rocks abstract the engineering behaviour of rocks depends upon whether the fabric is isotropic or anisotropic which is a reflection of its genetic environment even though anisotropy in fabric can occur in nearly all natural environments metamorphic terrains usually offer the main source of anisotropic fabric elements metamorphic anisotropic fabrics collectively known as foliation may be quantified by a foliation index determined from optical microscopic or x ray diffraction analysis depending upon the degree of coarseness or fineness of the rock on the basis of this index the role of foliation in conditioning anisotropy in point load strength has been quantified the practical significance of the resultant classification scheme lies in the fact that reliable predictions of point load strength anisotropy of foliated rocks can be made on the basis of a critical analysis of their primary anisotropic fabrics foliation

the holocene indian monsoon variability over the southern tibetan plateau and its teleconnections abstract a high resolution stalagmite oxygen isotope record from tianmen cave located in the south central tibetan plateau characterizes detailed climatic variations between 8 7 and 4 3 ka bp on centennial and decadal time scales with a temporal resolution of 3 to 7 years the tianmen record is in good agreement with speleothem records from asian monsoon regions i e dongge cave dykoski et al 2005 wang et al 2005 qunf cave fleitmann et al 2003 upwelling records from the arabian sea gupta et al 2003 gupta et al 2005 and peat bog records from southeast tibetan plateau hong et al 2003 indicating that the indian summer monsoon ism gradually weakened as northern hemisphere summer insolation declined during the early mid holocene and that ism intensity rather than temperature dominates the precipitation 18o on centennial to decadal time scales in the southern tp on centennial to decadal time scales the detrended tianmen record correlates well with the greenland ice core record further confirming the mechanistic connection between the ism and high northern latitude temperature changes meanwhile the tianmen record bears significant solar activity cycles suggesting that the solar output changes may affect the variability of the ism and likely the position of the intertropical convergence zone itcz as well moreover due to joint effects of changes in monsoon precipitation moisture source and temperature the tianmen 18o record shows much larger amplitude changes than speleothem 18o records from low elevation asian monsoon regions which is similar to the previously reported marine isotope stage mis 5 record cai et al 2010 suggesting heightened sensitivity of precipitation isotope composition to climate changes over the high elevation regions and further demonstrating that the stable isotope lapse rate may change under different climatic conditions

controls on intra plate seismicity in southwestern australia abstract although the southwest seismic zone swsz located about 150 km to the east of perth in southwestern australia is one of the most seismically active areas in australia there is little understanding as to why the earthquakes are occurring an analysis of geophysical geological and geodetic data from the area suggests that the swsz coincides with a precambrian terrane boundary seismic data show that the terrane boundary zone dips at a shallow angle in a northeasterly direction reactivation of this zone of weakness in the contemporary stress field east west maximum horizontal stress is interpreted to be the first order control on seismicity in the region gravity data show that the terrane boundary is offset by near orthogonal structures which are interpreted as faults at least one of these trends corresponds with a linear zone of epicentres the temporal and spatial distributions of epicentres associated with the 1968 meckering earthquake ml 6 9 suggest that the second order distribution of seismicity in the swsz can be explained by the intersection model whereby stresses are amplified by space problems associated with displacements on crosscutting faults it is speculated that a zone of high density and high seismic velocity in the lower crust may also be a second order control on the local seismicity however confirmation awaits better delineation of the extent of this zone

association between atmospheric circulation patterns and firn ice core records from the inilchek glacierized area central tien shan asia 1 glacioclimatological research in the central tien shan was performed in the summers of 1998 and 1999 on the south inilchek glacier at 5100 5460 m a 14 36 m firn ice core and snow samples were collected and used for stratigraphic isotopic and chemical analyses the firn ice core and snow records were related to snow pit measurements at an event scale and to meteorological data and synoptic indices of atmospheric circulation at annual and seasonal scales linear relationships between the seasonal air temperature and seasonal isotopic composition in accumulated precipitation were established changes in the 18o air temperature relationship in major ion concentration and in the ratios between chemical species were used to identify different sources of moisture and investigate changes in atmospheric circulation patterns precipitation over the central tien shan is characterized by the lowest ionic content among the tien shan glaciers and indicates its mainly marine origin in seasons of minimum precipitation autumn and winter water vapor was derived from the arid and semiarid regions in central eurasia and contributed annual maximal solute content to snow accumulation in tien shan the lowest content of major ions was observed in spring and summer layers which represent maximum seasonal accumulation when moisture originates over the atlantic ocean and mediterranean and black seas

holocene vegetation and climate of the alashan plateau nw china reconstructed from pollen data a set of 55 recent pollen spectra from the alashan plateau and the qilian mountains qilianshan northwestern china has been analyzed the established relationships between the pollen spectra and modern vegetation and precipitation patterns of the studied area have been applied to 65 fossil pollen spectra from a 825 cm long sediment record collected in the topographic depression formerly occupied by eastern juyan palaeolake 41 89 n 101 85 e 892 m a s l several qualitative approaches e g indicator plant species artemisia chenopodiaceae and ephedra fragilis type s l ephedra distachya type pollen ratios and quantitative methods of vegetation and climate reconstruction have been tested with the surface pollen and then applied to the eastern juyan pollen record fossil pollen data reveal pronounced environmental changes in the studied area of the alashan plateau between ca 10 700 and 1700 cal yr b p desert taxa as chenopodiaceae nitraria calligonum reaumuria were abundant in the vegetation cover around the study site through the whole record pollen spectra dated to ca 10 700 5400 cal yr b p are characterised by highest values of chenopodiaceae e fragilis type and other desert indicating taxa suggesting rather dry climate most favourable conditions are reconstructed between 5400 and 3900 cal year b p on the basis of relative increase in abundance of artemisia pollen a return to dry conditions occurred at about 3900 cal yr b p the lake finally desiccated after 1700 cal yr b p reconstructed dry climate oscillations between 5900 and 5400 and 3100 cal yr b p correlate well with similar events found in the published records from northern and western china and central mongolia however eastern juyan record does not show the early holocene humidity maximum as suggested by the sedimentary data from monsoon influenced areas of china

climatic oscillations over the past 120 kyr recorded in the guliya ice core china recently several ice cores were drilled on the tibetan plateau to examine climate and environmental changes based on the temperature proxy records in the guliya ice core climate oscillations over the past 120 kyr were examined using wavelet analysis and singular spectrum analysis methods the results showed two main milankovitch type oscillatory modes 22 and 44 kyr the 22 kyr period corresponds to the precession period and 44 kyr period corresponds to the earth axis s obliquity inclination period the two periods combined explain 43 of the variance in addition there are millennial and 10 thousand years time scales periods which may be related to the dansgaard oeschger d o cycles and the heinrich h events r 2006 elsevier ltd and inqua all rights reserved

a 700 year history of groundwater recharge in the drylands of nw china a 700 year semi quantitative history of diffuse groundwater recharge in the badain jaran desert inner mongolia is proposed on the basis of solute data from multiple unsaturated zone groundwater profiles using mass balance of chloride to establish recharge rates and profile chronologies four relatively humid 1330 1430 1500 1620 1700 1780 and 1950 1990 and three relatively arid phases 1430 1500 1620 1700 and 1900 1950 are discernable across the profiles the recharge history broadly reflects multidecadal to centurial timescale precipitation changes in the northern tibetan plateau and suggests that variations in east asian summer monsoon intensity affect desert recharge rates uncertainties in the records owing to assumptions about the cl inputs are examined by comparing deterministic and stochastic cl input scenarios such records are valuable for assessing spatial aspects of climate changes in the region as well as for informing sustainable water resource management strategies for northwestern china s drylands

a pollen record of holocene climatic changes from the dunde ice cap qinghai tibetan plateau pollen preserved in ice cores from the dunde ice cap provides a sensitive record of holocene climatic changes and vegetational response in the northern qinghai tibetan plateau at time scales ranging from millennia to centuries and decades pollen analysis of the annually resolvable ice layers for a 30 yr period 1957 1986 suggests that total pollen concentration is correlated positively with summer precipitation and negatively with summer temperature thus it is a sensitive indicator of moisture availability and vegetation density in the steppe and desert regions around dunde high pollen concentrations between 10 000 and 4800 yr b p suggest that the summer monsoon probably extended beyond its present limit to reach dunde and westernmost tibet in response to orbital forcing the summer monsoon retreated time transgressively across the qinghai tibetan plateau during the middle holocene relatively humid periods occurred at 2700 2200 1500 800 and 600 80 yr b p probably as a result of neoglacial cooling prominent pollen changes during the medieval warm period 790 620 yr b p and the little ice age 330 80 yr b p suggest that the vegetation in the qinghai tibetan plateau region is sensitive to abrupt century scale climatic changes such as those anticipated in scenarios of greenhouse warming

climatic and local effects on stalagmite δ13c values at lianhua cave china abstract carbon isotopes in speleothems may serve as indicators of vegetative change climatic conditions and karst processes in many recent studies of chinese stalagmites however carbon isotopes have often been neglected or underutilized in interpreting paleoenvironments here we present a continuous decadal scale 13 c record 819 measurements of the mid to late holocene from a precisely dated 10 230 th dates aragonite stalagmite from lianhua cave hunan province china compared to coeval stalagmites from other chinese caves the average 13 c value 3 6 of stalagmite a1 is higher by 2 7 variations in the 13 c values 0 1 to 6 0 reflect changes in both vegetative productivity and inorganic processes which respond to climatic processes the 13 c record of stalagmite a1 can be subdivided into three intervals 1 warm humid stage 6 6 to 3 8 ka 2 transitional stage 3 8 to 1 6 ka and 3 cool arid stage 1 6 ka to present comparisons with other stalagmite and paleoclimatic records demonstrate that these intervals are generally consistent with changes in regional vegetation and climatic conditions

response of monsoonal temperate glaciers to global warming since the little ice age abstract monsoonal temperate glaciers in china mainly occur in the southeastern part of qinghai tibetan plateau they constitute an area of 13203 2 km2 accounting for 22 2 of china s total glaciated area such glaciers are extremely sensitive to climatic warming due to their unique characters an inconsiderable rise in air temperature may lead to a significant rise in ela and a large shrinkage in glacier area since the maximum of the little ice age 17th century the mean temperature of monsoonal temperate glaciers in china has increased by 0 8 c and the glacier area has decreased by 3921 2 km2 an amount equivalent to 30 of the modern glacier area it is predicted that by the year 2100 the temperature in the monsoonal temperate glaciers of china will rise by 2 1 c the glacier area will decrease by 75 approximately 9900 km2 if the precipitation decreases the retreat of the glaciers will be even faster but the area reduction percentage of the glaciers will not exceed 80 this will no doubt pose a serious threat to the water resources and environment in these regions

late quaternary sedimentation in the paraiba basin northeastern brazil landform sea level and tectonics in eastern south america passive margin abstract late quaternary deposits in the northeastern brazil have been scarcely investigated despite their relevance to the discussion of the post rift evolution of the south american passive margin within the context of landform sea level and tectonic deformation sedimentological stratigraphic and morphological characterization of these deposits referred as post barreiras sediments led to their distinction from underlying early middle miocene strata based on optically stimulated luminescence osl dating two sedimentary units pb1 and pb2 were recognized and related to the time intervals between 74 8 9 3 and 30 8 6 9 ka and 8 8 0 9 and 1 8 0 2 ka respectively unit pb1 consists of indurated sandstones and breccias either with massive bedding or complex types of soft sediment deformation structures generated by contemporaneous seismic activity unit pb2 is composed of massive sands or sands related to structures developed by dissipation of dunes the present work focusing on the post barreiras sediments discusses landform sea level and tectonics of the eastern south american passive margin during the latest quaternary non deposition and sub aerial exposure related to the tortonian worldwide low sea level combined with tectonic quiescence followed the miocene transgression tectonic deformation in the latest pleistocene created space to accommodate unit pb1 in downthrown faulted blocks and perhaps also synclines produced by strike slip deformation although deposition of this unit was simultaneous with the progressive fall in sea level that followed the last interglacial maximum punctuated rises combined with land subsidence led to marine deposition close to the modern coastline renewed subsidence in the holocene gave rise to accommodation of the post barreiras sediments most of unit pb2 was deposited during the holocene transgression but it is not composed of marine sediments which suggests either an insignificant rise in relative sea level or aeolian reworking of thin transgressive sands the data presented here lead to a review of the evolution of the south american passive margin based on assumptions of uniform sedimentation and undeformed planation surfaces over a wide coastal area of the northeastern brazil

correlation between precipitation and temperature variations in the past 300 years recorded in guliya ice core china the guliya ice cap on the crest of the kunlun shan central asia is an ideal site for acquiring ice cores for climate change studies detailed analyses of the precipitation index glacier accumulation and the temperature proxy do recorded in the guliya ice core since 300 years bp show that precipitation correlates with temperature in this region climate conditions in the guliya region since 300 years bp can be separated into three periods warm and wet from ad1690 to the end of the 18th century cold and dry from the 19th century to the 1930s and warm and wet again since the 1940s during this period the climate exhibits just two phases warm wet and cold dry comparison of the temperatures and the precipitation recorded in the guliya ice core shows that variations of temperature and precipitation in the region correlate quite well however changes in the precipitation regime appear to lag behind those of the temperature by 20 40 years we believe this results from the larger heat capacity of the ocean relative to that of the land hence ocean temperatures and corresponding evaporation rates change more slowly than do continental conditions additionally however positive feedback processes such as increasing temperatures and precipitation improving vegetation moisture retention and hence local convective precipitation probably play an important role in this paper we explain how the timescale of evolving vegetation and the feedback mechanism between precipitation and the temperature could help explain why the changes in precipitation lag those of temperature by 20 40 years over long periods taking this time lag into account we should be able to predict future precipitation trends based on observed temperature trends

microparticle content records of the dunde ice core and dust storms in northwestern china abstract dust storms are important atmospheric phenomenon in central asia particularly in the regions bordering deserts arid and semi arid regions dust storms occur quite often in northwestern china there are some research results about past dust storm events using historical archives in china however the archives used cover limited time and area microparticle concentrations in the dunde ice cap qilian mountain of northwestern china represent a continuous record of past dust storms comparison between dust rain frequency reconstructed from historical archives and the ice core record from the dunde ice cap demonstrate that the microparticle record in the dunde ice core is a good indicator of dust storms in northwest china according to the ice core records we can reconstruct the dust storm chronology for historical time during the past 700 years the dust content fluctuated with time and lower frequency variations existed although the linear trend increased over the past 700 years dust content was decreasing since the early 1700s during the little ice age it was slightly higher corresponding to the cold period

speleothem evidence for changes in indian summer monsoon precipitation over the last 2300 years speleothems from a well ventilated dolomitic cave in the pokhara valley central nepal preserve a mineralogic record of indian summer monsoon variability over the past 2300 yr annually deposited aragonite layers formed between 2300 and 1500 yr b p indicating reduced monsoon precipitation and increased cave aridity whereas alternating calcite aragonite laminae deposited after 1500 yr b p record elevated summer monsoon precipitation and increased cave humidity dense optically clear calcite layers deposited from 450 5 to 360 20 yr b p 1550 to 1640 a d indicate a less evaporative cave environment and suggest moister and or cooler conditions possibly related to climatic change associated with the onset of the little ice age

complex decapod burrows and ecological relationships in modern and pleistocene intertidal carbonate environments san salvador island bahamas abstract burrowing by thalassinidean shrimp in modern tropical shallow subtidal to intertidal carbonate environments is widespread and a powerful agent of bioturbation particularly within sandy substrates deep and intense burrowing by callianassids commonly occurs along the intertidal margins of hypersaline lagoons throughout the bahamas such as pigeon creek on san salvador island where the sediments of extensive sand flats are thoroughly bioturbated by glypturus acanthochirus in addition to dominating the deep tier infauna g acanthochirus is a true ecosystem engineer and its prodigious burrowing activity results in a highly mounded topography on sand flats individual sediment cones commonly coalesce with time to form large composite mounds with surfaces stabilized by the development of microbial mats this unique biogenetically produced topography sets the stage for colonization by shallow tier burrowers particularly the upogebiid shrimp upogebia vasquezi and several species of fiddler crabs burrow systems of u vasquezi are distinctive and complex they typically consist of a pair of u shaped burrows in close proximity or criss crossing with knobs or short tunnels at their bases the entire u burrow pair is lined by a thick externally pelleted wall inside burrow diameters range from 0 2 to 1 cm and burrow depths are 10 15 cm in contrast to the much deeper callianassid burrows these complex upogebiid burrows also occur as trace fossils in late pleistocene lagoon margin facies of the grotto beach formation on san salvador initially reported as fragmentary burrow fills whole burrow systems virtually identical to the modern upogebiid burrows recently have been found at several localities these fossil burrows are most abundant in beds lying immediately below a terra rossa paleosol that marks the late pleistocene holocene stratigraphic boundary and the beds likely were deposited with sea level stillstand and regression associated with the onset of wisconsinan glaciation with their high potential for preservation these complex upogebiid trace fossils may prove useful as both paleoenvironmental and sea level position indicators in the study of quaternary carbonate sequences throughout the bahamas and other geologically similar regions

climate variability in the past 19 000 yr in ne tibetan plateau inferred from biomarker and stable isotope records of lake donggi cona abstract we investigated 4 84 m long sediment record spanning over the late glacial and holocene from lake donggi cona to be able to reconstruct circulation pattern on the tibetan plateau tp presently lake donggi cona is located at the boundaries of westerlies and asian monsoon circulations in the northeastern tp however the exact timing and stimulating mechanisms for climatic changes and monsoon shifts in this region are still debated we used a 19 ka long stable isotope record of sedimentary n alkanes to address this discrepancy by providing insights into paleohydrological conditions the d of n c 23 is influenced by lake water evaporation the d values of sedimentary n c 29 are mainly controlled by moisture source and temperature changes long chain n alkanes dominate over the core whereas three mean clusters i e microbial aquatic and terrestrial can be inferred multi proxies suggest five major episodes in the history of lake donggi cona the lake donggi cona record indicates that the late glacial 18 4 14 8 cal ka bp was dominated by low productivity of mainly microbial and aquatic organisms relatively low d values suggest low temperatures and moist conditions eventually caused by stronger westerlies winter monsoon and melt water influence likely the shift 17 9 cal ka bp from microbial to enhanced aquatic input suggests either a change from deep to shallow water lake or a break in local stratification between 14 8 and 13 0 cal ka bp variable climatic conditions prevailed although the westerlies weekend the increase in temperature enhanced the permafrost and snow melting displayed by a high sedimentary accumulation rate higher d values indicate increasingly arid conditions with higher temperatures which eventually lead to high evaporative conditions and lowest lake levels low vegetation cover and high erosion rates led to high sediment accumulation resulting in stratification followed by anoxia in the terminal lake from 13 0 to 9 2 cal ka bp lowered values of d along with high contents of terrestrial organic matter marked the early holocene warming indicating a further strengthening of summer precipitation and higher lake levels a cooling trend was observed in the mid holocene between 9 2 and 3 0 cal ka bp accompanied by higher moisture availability displayed by lowered d values caused by reduced evaporative conditions due to a drop in temperature and recovering westerlies after 3 0 cal ka bp a decrease in lake productivity and cold and semi arid conditions prevailed suggesting lower lake levels and reduced moisture from recycled air masses and westerlies we propose that the summer monsoon was the predominant moisture source during the bolling allerod warm complex and early holocene followed by westerlies in mid to late holocene period stable carbon isotope values 32 indicate the absence of c 4 type vegetation in the region contradicting with their presence in the lake qinghai record the d record from lake donggi cona highlights the importance of the interplay between westerlies and summer monsoon circulation at this location which is highly dynamic in northeastern plateau compared to the north atlantic circulation and insolation changes consequently lake donggi cona might be an important anchor point for environmental reconstructions on the tibetan plateau

sediment deformation in miocene and post miocene strata northeastern brazil evidence for paleoseismicity in a passive margin abstract stratigraphic intervals characterized by varied and complex styles of soft sediment deformation structures are well preserved in miocene and late pleistocene to holocene deposits of a sedimentary basin located in northeastern brazil the miocene strata represented by the barreiras formation record only brittle structures including numerous faults and fractures with straight and high angle dipping planes that are often filled with sands derived from overlying beds folds consisting of broad anticlines and synclines are also present in this unit the late pleistocene to holocene deposits named post barreiras sediments contain an indurated sandy package with a large variety of ductile and brittle deformation structures i e massive sandstones with isolated sand fragments and breccias undulatory strata sand dykes and diapirs sinks and bowls pebbly pockets plunged sediment mixtures fitted sand masses cone shaped cracks fault grading and sedimentary enclaves these features confined to sharp based stratigraphic horizons that progressively grade downward into undisturbed deposits are related to seismic shocks of high surface wave magnitude i e ms 5 or 6 amalgamated seismites suggest that previously formed seismites were affected by subsequent seismic wave propagation seismic waves caused by activity along one or most likely several tectonic structures would have propagated throughout the depositional environment producing laterally extensive seismites the close proximity to earthquake epicenters would have promoted pervasive re sedimentation due to pore overpressure resulting high volumes of massive sandstones and breccia the similarity between deposits with correlatable strata from many other areas along the brazilian coast allows raise the hypothesis that the seismic episodes might have affected sedimentation patterns in a large i e extension of several hundreds of kilometers geographic area thus the modern seismicity recorded along northeastern brazil was recurrent during the quaternary and perhaps also in the pliocene the estimated high magnitude of the seismic events and the great regional extent of the affected area demonstrate that the brazilian coast experienced tectonic stress through the last geological episodes of its evolution which would have favored sediment accumulation and penecontemporaneous re sedimentation this geological context is unexpected in a passive margin inducing to revisit the debate on how active is a passive margin

late pleistocene marine terrace deposits in northeastern brazil sea level change and tectonic implications abstract coastal areas of passive margins are among the best places to examine the reality of sea level changes elevation of marine terraces is central to interpretation of their approximate age in this kind of tectonic setting the recognition of pleistocene shorelines on the south american eastern continental margin is becoming increasingly common but data are commonly imprecise in both time and space and the resulting chronology is based mainly on geomorphological attributes nine thermoluminescence dates and four optically stimulated luminescence dates of 220 206 ka and 117 110 ka were obtained for two marine terrace deposits along 340 km of coast in rio grande do norte state northeastern brazil they are correlated with the highstands of marine oxygen isotope substages 7c and 5c sea level respectively the older deposit occurs mainly on the n s trending coast and ranges in elevation between 7 5 and 1 3 m the latter is found along the e w trending coast at altitudes that vary between 1 m and 20 m it indicates relative downfaulting of the 220 206 ka marine terrace and uplift of the 117 110 ka marine deposit which is locally about 12 m higher than deposits of similar age described 1000 km to the south it follows that elevation alone is an unreliable tool for establishing a quaternary sea level change chronology also on passive margin coastal areas

late oligocene miocene transgressions along the equatorial and eastern margins of brazil abstract the seaboard of brazil is a highly favorable setting for studying episodes of worldwide sea level rise because of its passive nature previous studies of the equatorial coast of brazil have led to the recognition of extensive oligo miocene and miocene marine influenced deposits but these deposits have been overlooked in other coastal areas of brazil the aim of the present study is to show the origin and evolution of late oligocene and miocene marine influenced strata exposed in more than 5000 km of coastal areas along the wnw trending equatorial and nne trending eastern brazilian continental margins we review the most relevant data concerning the strata of these ages exposed along the equatorial and eastern margins of brazil and combine them with new data based on these occurrences we analyze the history of sea level fluctuations and show that marine influenced strata are more widespread in these margins than originally thought our main results indicate that a marine influence is not only imprinted in the deposits exposed along the equatorial margin but it is also widespread in several areas of the eastern margin for a long geological time interval ranging from the end of the cretaceous or paleogene up to the late oligocene most of the brazilian coast remained a non depositional site exposed to subaerial erosion and lateritic soil development the combination of sea level rise and tectonic subsidence promoted sediment accumulation in the onshore portion of several basins two transgressive episodes occurred one in the oligo miocene and another in the early middle miocene the latter gave rise to deposition of the barreiras formation however during the supposedly middle miocene eustatic sea level highstand in coastal brazil there was a renewed and extensive phase of non deposition and subaerial erosion with lateritic soil formation a process that lasted up to the late quaternary this mismatching of the sedimentary record with other south american and continental areas is discussed herein as in many other areas of south america and of the world the regressive transgressive events recorded along the brazilian coast most likely responded to a combination of eustatic sea level fluctuations and local factors such as tectonic activity intraplate stresses and changes in dynamic topography during the post rift history of the eastern south american plate

engineering behaviour of phyllites abstract the physico mechanical behaviour of intrinsically anisotropic rocks cannot be assessed through common engineering experiences due to a number of governing intrinsic factors e g variation of mineral assemblage fabric and physical and mechanical properties the study of such rocks under the stress conditions existing within the drilling reach of the earth s crust has not been given due attention not even in laboratory simulated conditions therefore it seemed worthwhile to undertake a comprehensive study using three varieties of intrinsically anisotropic phyllites obtained from the vicinity of the chamera hydroelectric project site in the himalayan region attention has been paid to their petrographic and petrofabric analyses through thin sections x ray diffraction and scanning electron microscopy and the physical and geotechnical properties with special reference to their anisotropyp compression tests were run from unconfined to a maximum confining pressure 3 of 70 mpa for the three phyllites at specified orientation angles angle between the plane of weakness and the direction of the major principal stress 1 of 0 15 30 45 60 75 and 90 thus the physico mechanical response of the phyllites as a function of confining pressure and the orientation angle has been determined and the degree of anisotropy could be quantified in terms of physically measureable parameters

a 1000 year climate ice core record from the guliya ice cap china its relationship to global climate variability in 1992 an american chinese expedition successfully recovered three ice cores 308 6 93 2 and 34 5m from the guliya ice cap summit 6710 m a s l in the far western kunlun on the qinghai tibetan plateau china guliya resembles a polar icecap with 10 m 200 m and basal temperatures of 15 6 5 9 and 2 1 c respectively the 308 6 m core to bedrock is the longest ice core retrieved from an elevation greater than 4000 m a s l and provides the first ice core history from the western side of the qinghai plateau the plateau experiences a pronounced annual precipitation cycle during which 70 80 of annual total precipitation falls in the summer monsoon season this leads to a marked visible stratigraphy in the glaciers which allows accurate dating of the ice cores and reconstruction of the net mass accumulation this paper presents 1 the results of the geophysical program to determine ice thickness ice flow and surface topography 2 an assessment of net accumulation from stake measurements snow pits and shallow core samples and 3 the analyses of the upper 100 m of the 308 6 m core which provide a 1000 year history including the little ice age which is compared with chinese historical records extended periods of positive accumulation on guliya are closely contemporaneous with dry periods in eastern china a trans pacific teleconnection is suggested by the strong temporal coherence between extended wet and dry phases on guliya and on the quelccaya ice cap peru

effect of planar structures on the anisotropy of ranyah sandstone saudi arabia the anisotropy of metamorphic and sedimentary rocks is mainly due to the presence of a single set of discontinuity surfaces such as cleavage foliation schistosity joints microfissuring or bedding the uniaxial compressive strength anisotropy curve is usually u shaped however the presence of more than one discontinuity modifies the shape of the anisotropy curve therefore ranyah sandstone having two sets of mutually perpendicular discontinuities was selected and tested the investigation includes the geological and engineering geological descriptions as well as the classification of the rock mass it also includes the determination of the physical mechanical and dynamic properties of the rock material the most sensitive engineering property to the anisotropic behaviour for ranyah sandstone was found to be the compressive strength a w shaped anisotropy curve was obtained this shape is due the superimposed effects of the two directions of bedding and microfissures acting almost at right angles to each other and is in line with hoek and brown s hoek e brown e t 1980 underground excavations in rock the institution of mining and metallurgy london p 165 hypothesis for two mutually perpendicular discontinuities a comparison of the anisotropic behaviour of the ranyah sandstone with same foreign sandstones of different origin was also made

commensal worm traces and possible juvenile thalassinidean burrows associated with ophiomorpha nodosa pleistocene southern brazil abstract the pleistocene chui formation at osorio rio grande do sul brazil consists of coastal marine and eolian sands the former containing abundant and well preserved ophiomorpha nodosa burrow systems detailed ichnological study has revealed interesting features associated with them small sized ophiomorpha here assigned to a new ichnospecies o puerilis are interpreted as possible burrows of juvenile thalassinidean crustaceans probably belonging to the same species as the producers of larger o nodosa additionally helicoidal burrows with thick concentrically laminated linings are associated with the walls of o nodosa they are assigned to the new ichnospecies cylindrichnus helix and they are interpreted as dwellings of commensal annelid worms the association of these three ichnospecies constitutes a fossil example of the role of thalassinideans as ecosystem engineers able to modify their environment and to create new space and resources usable by other organisms

monsoon and dust signals recorded in dasuopu glacier tibetan plateau during summer 1997 a 15 m firn core was recovered from dasuopu glacier 28 23 n 85 44 e 7000 m a s l on the northwest margin of xixabarngma feng in the central himalaya oxygen isotope values and concentrations of ca 2 mg 2 nh 4 so 4 2 and no 3 were measured over the 10 years of snow accumulation captured in the firn core the seasonal variations of 18 o values and major ion concentrations in the dasuopu core indicate that summer monsoon and dust signals are clearly recorded in dasuopu glacier annual variations in 18 o values are controlled by the amount effect with more negative i e lighter 18 o values representing summer monsoon precipitation characteristic of tropical regions higher concentrations of ca 2 mg 2 and so 4 2 reflect the influx of mineral aerosols from the vast arid and semi arid desert regions to the north and west during the spring dust storm period high spring concentrations of nh 4 and no 3 appear to reflect changes in regional biogenic source strength

the role of precambrian mylonitic belts and present day stress field in the coseismic reactivation of the pernambuco lineament brazil abstract the pernambuco lineament is a steeply dipping continental scale ductile shear zone rooted within the precambrian lithosphere of intraplate northeastern brazil it was formed during the brasiliano orogeny 600 ma and reactivated during the pangea breakup in the cretaceous when it controlled fault propagation and sediment accumulation in several rift basins the region is now under an e w trending horizontal compression and n s trending extension and faulting occurs predominantly in a strike slip regime we investigated two aftershock sequences and the preexisting tectonic fabrics along the pernambuco lineament in order to evaluate the role of these fabrics in the coseismic reactivation of continental scale structures the lineaments consist of a main ene wsw trending mylonitic belt about 2 3 km wide and two secondary ne trending mylonitic belts about 100 m wide they both present steeply dipping mylonitic foliations and shallowing plunging stretching lineations the mylonites present granitoid protoliths and mineral parageneses that range from amphibolite to greenschist facies brittle deformation overprints the ductile fabric in all mylonitic belts in 1991 coseismic reactivation nucleated along the ene wsw striking 3 3 5 6 km deep normal fault of less than 1 km in length in the main mylonitic belt in 2002 seismicity migrated to a ne trending secondary mylonitic branch and moved as a right lateral strike slip 1 2 km long 3 8 4 9 km deep fault plane both fault segments reactivated the mylonitic foliation and form part of a major system we conclude that the interplay between the present day stress field and preexisting fabrics controls seismogenic fault location attitude and kinematics the pernambuco lineament is an example of a long lived continental scale structure where selective reactivation has occurred other shear zones in the region also show a long history of brittle reactivation and present similar orientation in relation to the present day stress axes they might be dormant structures prone for reactivation under the present day stress field

paleosurfaces from northeastern amazonia as a key for reconstructing paleolandscapes and understanding weathering products the characterization and mapping of paleoweathering surfaces as well as their associated deposits throughout the northeastern amazonia can be a useful tool for inter basin stratigraphic correlations and for establishing the evolution of landscapes and climates through time this type of investigation has led to the recognition of five weathering surfaces developed from the upper cretaceous through the quaternary designated here as s1 to s5 surface s1 occurs at the top of late cretaceous deposits represented by the ipixuna cujupe succession as well as on older precambrian and paleozoic rocks surface s2 marks the top of an indurated massive semi flint1 unit for cases in which surfaces s1 and s2 are amalgamated a thick lateritic paleosol displaying hexagonal branched concretions is present surface s3 occurs at the top of the pirabas and lower portion of the barreiras formations of late oligocene early miocene age and it is also associated with paleosol but has no lateritization when surface s3 is amalgamated with surfaces s1 and s2 bauxite is present in association with the underlying laterites surface s4 bounds the top of the middle to upper barreiras formation of middle miocene age as well as correlatable deposits known as the belterra clay this surface is marked by a lateritic paleosol having columnar concretions surface s5 occurs between a lower unit consisting of massive light red sands of the plio pleistocene post barreiras 1 sediments and an upper unit of yellow eolian sands of the holocene post barreiras 2 sediments the paleoweathering surfaces present in the northeastern amazonia enable the reconstruction of several depositional episodes represented by thin only few meters thick sedimentary units from the late cretaceous to the quaternary the creation of new accommodation space on subsiding areas gave rise to sediment accumulation during transgressions intervening weathering surfaces formed during significant falls in relative sea level associated with tectonically stable episodes the overprinting of weathering surfaces formed during different times and thus under different climatic conditions seems to have been crucial for the development of the various weathering products observed throughout the region which include economically important laterites bauxites semi flint beds and kaolin deposits this paper shows that the genesis of these deposits was controlled by the complex interplay of tectonics climate sediment deposition and erosion resulting in a complex evolution of paleolandscapes

microorganisms in the malan ice core and their relation to climatic and environmental changes 1 a 102 m long ice core retrieved from the malan ice cap on the tibetan plateau provides us with a historical record of the microorganisms trapped in the ice the microorganisms in the malan ice core are identified as and proteobacteia and the lgc hgc and cfb group by means of the results of 16s rrna sequence analysis and physiological characteristics while the eukaryotes in the ice core are mainly composed of chlamydomonas sp and pseudochlorella sp based on the phylogenetic examination of the 18s rrna gene the microbial populations show observable differences at different depths in the ice core reflecting the effects of climatic and environmental changes on the distribution of the microorganisms in the glacier examination of the malan ice core shows four general periods of microbial concentration which correspond to four phases of temperature revealed by 18o values in the core observations also indicate that microorganism concentrations tend to be negatively correlated with the temperature at a relatively long timescale and to some extent positively correlated with mineral concentrations the present study demonstrates that more microorganisms are associated with colder periods while fewer microorganisms are associated with warm periods which provides us with a new proxy for the reconstruction of past climatic and environmental changes by means of ice core analysis

3 d geometry and luminescence chronology of quaternary soft sediment deformation structures in gravels northeastern brazil abstract this paper reports and describes soft sediment deformation in gravels and gravelly sediments in quaternary alluvial deposits of the potiguar basin northeastern brazil deformation structures were measured in terms of geometry size and relationship with sedimentary bedding using geological mapping and ground penetrating radar tl and osl irsl methods following mar and sar protocols were used to date sediments and soft sediment deformation events our results indicate that soft sediment deformation structures are widely distributed in several stratigraphic intervals of alluvial channel deposits in a low lying topographic valley depending on their geometry and composition two types of soft sediment deformation structures occur pockets and dome like load structures these structures resulted from the shaking of sediments with a reverse density gradient system which caused collapse and realignment of pebbles these features are similar in morphology and size to modern examples of seismically induced soft sediment deformation in coarse sediments tl and osl ages indicate that sediment deposition and associated soft sediment deformation occurred at least six times from 352 ka to 9 ka

an 80 year summer temperature history from the xiao dongkemadi ice core in the central tibetan plateau and its association with atmospheric circulation abstract the climate significance of oxygen isotopes from the central tibetan plateau ctp ice cores is a debated issue because of large scale atmospheric circulation a high resolution 18 o record was recovered from the xiao dongkemadi xd ice core which expanded the spatial coverage of 18 o data in this region annual average 18 o correlated significantly with nearby mjjas air temperatures suggesting the 18 o can be used as a proxy to reconstruct regional climate change the reconstructed temperature anomaly is related to the regional and global warming trends and the greater warming amplitude since 1970s is related to the elevation dependency of the warming signal the close relationship of the warming to variations in glacier mass balances and discharge reveal that recent warming has led to obvious glacier shrinkage and runoff increase correlation analysis suggests that monsoon and westerly moisture substantially influence the ctp ice core records along with an increase in their level of contribution to the xd core accumulation in recent decades and confirms a teleconnection of regional climate of the ctp ice cores with climate parameters in the indian and north atlantic oceans

a 7 ka climatic variability record inferred from peat bog sediments in the north of bayan har mountains northeastern tibetan plateau reconstructions of the holocene especially the mid holocene climatic and environmental changes may serve as an analogue for future scenarios about 7 ka of holocene climatic variability in the north of bayan har mountains on the northeastern tibetan plateau is reconstructed using grain size magnetic susceptibility geochemical parameters and accelerator mass spectrometry 14c chronology from peat bog sediments the peat s source is found to be aeolian sediments climatic variability from the peat bog sediments during the last 7 3 ka can be divided into four stages warm and wet from 7 3 to 5 7 cal ka bp cool and dry semi wet from 5 7 to 2 5 cal ka bp relatively cool and wet from 2 5 to 1 1 cal ka bp and cold and dry from 1 1 cal ka bp to present mid late holocene climate in the north of bayan har mountains was significantly unstable during the last 7 3 ka and characterized by five centennial scale oscillations 6 2 6 0 4 3 3 9 2 5 2 1 1 7 1 4 and 0 7 0 2 cal ka bp this mid late holocene climate recorded by peat bog deposits is consistent with most lacustrine sediment records in the north of bayan har mountains and its adjacent areas these lacustrine sediments indicated that the climate on the northeastern tibetan plateau was warm and humid in the early holocene cold and dry after the mid holocene ca 7 5 6 0 cal ka bp and relatively cool and wet in the late holocene

engineering properties of quartz mica schist quartz mica schist which is a highly anisotropic metamorphic rock usually presents a geotechnical challenge in construction projects to ensure a safe and economical design a comprehensive in situ and laboratory investigation scheme is necessary for projects to be built in quartz mica schist in this study such a comprehensive laboratory study of the engineering behavior of quartz mica schist has been carried out the p wave velocity tests tensile and uniaxial compressive strength tests and creep deformation tests conducted on specimens with differently oriented schistose planes all reveal the strong anisotropic characters of the rock the relevant crack initiation stress and crack damage stress analysis in uniaxial compression test which has not been previously applied to studying schistose rock has been performed in the present study when loading is parallel to schistose planes crack initiation stress and crack damage stress are lower than those in other loading directions as the compressive loading is applied parallel to schistose planes local tensile stresses are preferentially induced normal to the relatively weak schistose planes cracks are thus easier to develop than in any other loading directions since schistose plane orientation is one of the key factors to control the formation of macro cracks and hence failures of unloading test specimens these engineering geological characters should be taken into consideration in engineering design

a holocene paleotemperature record based on radiolaria from the northern okinawa trough east china sea using a radiolarian based transfer function mean annual sea surface temperature sst and seasonal temperature range are reconstructed through the last 10 500yrs in the northern okinawa trough down core sst estimates reveal that throughout the holocene the changes of mean annual sst display a three step trend i an early holocene continuous warming between 10 500 and 8500yr bp which ends up with a abrupt cooling at about 8200yr bp ii a relatively stable middle holocene with high sst that lasted until 3200yr bp and iii a late holocene distinct sst decline between 3200 and 500yr bp this pattern is in agreement with the ice core and terrestrial paleoclimatic records in the chinese continent and other regions of the world five cooling events with abrupt mean annual sst drops which occur at similar to 300 600 1400 3100 4600 5100 and 8200yr bp are recognized during the last 10 500yrs comparison of our results with records of gisp2 ice core and marine sediment in north atlantic region suggests these cooling events are strongly coupled which implies a possible significant climatic correlation between high and low latitude areas c 2007 elsevier ltd and inqua all rights reserved

glacier and permafrost signals of 20th century warming currently available evidence of 20th century warming from glaciers and permafrost is briefly reviewed the signals are clear and strong warming of polar firn and permafrost and mass losses of glaciers at lower latitudes were most striking towards the middle of the century the easily observable length reduction of mountain glaciers confirms the global character of the evolution a probably intermittent reversal of the trend was observed in places after about 1950

global dynamics of a temperate valley glacier mer de glace and past velocities deduced from forbes bands transverse profiles and velocities which have been measured on the ablation zone of mer de glace more or less continuously since 1891 contradict the weertman nye theory of glacier kinematic waves faint broad waves which undoubtedly result from fluctuations in the balance travel down the glacier faster than this theory predicts this theory having first been completed by taking changes in width with time and with distance down the glacier into account on the other hand velocity fluctuations are synchronous and more or less the same over the entire length studied 6 km these discrepancies result from bottom friction being of the solid type i e independent of sliding velocity friction should also be almost insensitive to discharge in subglacial waterways since in the steady state energy for keeping them open not entirely flooded and at atmospheric pressure is superabundant the sliding velocities at all cross profiles are thus controlled by some areas where the body of the glacier suffers strong deformation because the valley shape is far from cylindrical one such controlling zone exists on mer de glace owing to the existence of a subglacial transverse shoulder a new perturbation equation and a new rough expression for wave velocity are given intervals between forbes bands were plotted on seven aerial surveys between 1939 and 1979 progressive tilting of the slices of blue dusty ice from the position from which these dark bands proceed and progressive lowering of their exposed edge must be taken into account this analysis confirms the validity of our simple model for velocity fluctuations and allows us to estimate the entire series since the year 1888

controls on quaternary coastal evolution of the east northeastern coast of brazil roles of sea level history trade winds and climate abstract east northeastern brazil has a wave dominated micro to meso tidal coast lying entirely within the southern atlantic trade wind belt integration of geologic mapping radiocarbon dating and vibracoring data shows that the quaternary coastal evolution of this area was controlled by three major factors 1 sea level history 2 trade winds and 3 climate change sea level history along the east northeastern coast of brazil relative sea level has fallen approximately 5 m during the last 5000 y correlation of this sea level history with the evolution of beach ridge lagoonal and coastal plain deposits shows that 1 sea level rise favours the formation of barrier island lagoonal systems and the construction of intralagoonal deltas 2 sea level lowering is not conductive to barrier island formation rather lagoons and bays become emergent and beach ridge plains rapidly prograde trade winds sediment dispersal systems along the coastal zone of east northeastern brazil have been highly persistent since pleistocene time as deduced from beach ridge orientation this persistence results from the fact that sediment dispersal in wave dominated settings is ultimately controlled by atmospheric circulation which for the east northeastern coast of brazil is associated with the south atlantic high pressure cell the remarkable stability of this cell through time has allowed the accumulation of extensive beach ridge plains at the longshore drift sinks located along the coast climate change effects of quaternary climate changes on coastal sedimentation are twofold climate changes may affect rainfall patterns thus exerting an important control on coastal dune development along the coast of northeastern brazil active coastal dunes are only present in those areas in which at least four consecutive dry months occur during the year mapping of these areas has shown that dune development during the holocene has been episodic these episodes being probably controlled by variations in rainfall patterns associated with climate changes secondly despite its overall stability the position of the high pressure cell has experienced small shifts in position during the holocene in response to climate changes changes in wind direction associated with these shifts have induced modifications in the coastal dispersion system which are recorded in the strandplains as small truncations in the beach ridge alignments these results have important implications in understanding accumulation of ancient sandstone shoreline sequences

estimation of atmospheric transmissivity of solar radiation from precipitation in the himalaya and the tibetan plateau though solar radiation is important for glacier mass balance simulation solar radiation data are not always available as a result of analyzing meteorological data measured in the himalaya and the tibetan plateau a favorable correlation between precipitation and atmospheric transmissivity of solar radiation is found in terms of monthly values monthly mean solar radiation is derived from the relationship between atmospheric transmissivity of solar radiation and precipitation with input of monthly precipitation latitude skyline and time the differences between estimated and observed monthly mean solar radiation are 40 w m 2 in most cases however the differences at some sites are significantly large the error in the estimated solar radiation during the monsoon season can be large when the monthly mean precipitation rate is about 5 mm d 1 though the error in the estimated solar radiation during the non monsoon season is generally small due to low precipitation in the himalaya and the tibetan plateau during this season it can exceed 100 w m 2

investigating extreme flood response to holocene palaeoclimate in the chinese monsoonal zone a palaeoflood case study from the hanjiang river abstract palaeoflood events recorded by slackwater deposits swds were investigated extensively by sedimentological criteria of palaeohydrology along the upper hanjiang river valley modern flood swds were collected for comparison with palaeoflood swd in the same reaches three typical palaeoflood swds were observed within holocene loess soil blanket on the first river terrace land the grain size distributions of palaeoflood swds are similar to modern flood swds whereas they are different from eolian loess and soil palaeoflood swd lies in three major pedo stratigraphic boundaries ts l 0 l 0 s 0 and s 0 l t in the holocene loess soil profiles the chronology of three palaeoflood episodes was established by osl dating and pedo stratigraphic correlation with the well dated holocene loess soil profiles in the upper hanjiang river basin holocene palaeoflood events were dated to 9500 8500 3200 2800 and 1800 1700 a b p respectively palaeoflood discharges were estimated by the palaeoflood model i e slope area method and step backwater method the highest discharges are 51 680 53 950 m 3 s 1 at the 11 500 time scale in the xunyang reach of the upper hanjiang river valley holocene extraordinary hydroclimatic events in the hanjiang river often result from abnormal atmospheric circulations from southwest monsoons in the chinese monsoonal zone these results provide a regional expression of extreme flood response to holocene palaeoclimate to understand the effects of global climatic variations on the river system dynamics

high resolution record of paleoclimate since the little ice age from the tibetan ice cores climate changes during the little ice age were studied based on oxygen isotope values 18o measured from ice cores recovered on and nearby the qinghai tibetan plateau three cold periods have been identified and are supported by three widely existing moraine ridges formed during the little ice age importantly the amplitude of the three cold periods differ in the cores studied in the dunde ice core the coldest period occurred in the 17th century while it occurred in the 19th century in the guliya ice core all the ice cores recovered from the tibetan plateau and nearby regions show strong climatic warming in the 20th century

alkenone based reconstruction of late holocene surface temperature and salinity changes in lake qinghai china china the alkenone temperature proxy u k 0 37 indicates up to a 1 c change in mean annual air temperature or a 2 c change in summer lake water temperature during the late holocene oscillating warm and cold periods could be related to the 20th century warm period the little ice age the medieval warm period the dark ages cold period and the roman warm period the relative importance of c37 4 alkenone to total c37 alkenone production c37 4 fluctuated between 15 45 with higher values during warm periods suggesting that lake water was also fresher during these periods the coupled late holocene surface temperature and salinity changes suggest that asian monsoons strongly influenced the climate of the lake qinghai region citation liu z a c g henderson and y huang 2006 alkenone based reconstruction of lateholocene surface temperature and salinity changes in lake qinghai china geophys res lett 33 l09707 doi 10 1029 2006gl026151

engineering geological and geotechnical responses of schistose rocks from dam project areas in india abstract for a rational and safer design of civil and mining engineering structures in or on rocks a proper understanding of the quality of rock mass is required to assess the rock mass quality evaluation of physical and mechanical characteristics of the intact rocks is essential especially if the rock is anisotropic in nature the genetic complexity associated with its petrofabric makes it more difficult to predict its behaviour in this paper a comprehensive study of the compositional physical and geotechnical responses of four varieties of schists i e quartzitic chlorite quartz mica and biotite schists obtained from two hydroelectrical project sites in the foot hills of himalayas india has been presented anisotropic strength behaviour of the schists has been brought out through the testing of specimens with varying orientation of schistosity with respect to the major principal stress under uniaxial and triaxial conditions the significance of anisotropic response for consideration in the design is emphasized

asynchronous evolution of the indian and east asian summer monsoon indicated by holocene moisture patterns in monsoonal central asia abstract the numerical meta analysis of 92 proxy records 72 sites of moisture and or temperature change confirms earlier findings that the dominant trends of climatic evolution in monsoonal central asia since the last glacial roughly parallel changes in northern hemisphere summer insolation i e the period following the last glacial maximum was characterized by dry and cold conditions until 15 cal kyr bp followed by a warm wet period coincident with the bolling allerod warm period and terminated by a cold dry reversal during the younger dryas period after an abrupt increase at the start of the holocene warm and wet conditions prevailed until ca 4 cal kyr bp when moisture levels and temperatures started to decrease ordination of moisture records reveals strong spatial heterogeneity in moisture evolution during the last 10 cal kyr the indian summer monsoon ism areas northern india tibetan plateau and southwest china exhibit maximum wet conditions during the early holocene while many records from the area of the east asian summer monsoon indicate relatively dry conditions especially in north central china where the maximum moisture levels occurred during the mid holocene we assign such phenomena to strengthened hadley circulation centered over the tibetan plateau during the early holocene which resulted in subsidence in the east asian monsoonal regions leading to relatively dry conditions our observations of the asynchronous nature of the two asian monsoon subsystems on millennial time scales have also been observed on annual time scales as well as implied through the spatial analysis of vertical air motion patterns after strong ascending airflows over the tibetan plateau area that were calculated from ncep ncar reanalysis data for the last 30 years analogous with the early holocene the enhancement of the ism in a future warming world will result in an increase in the asynchronous nature of the monsoon subsystems this trend is already observed in the meteorological data from the last 15 years

quantification of strength anisotropy of metamorphic rocks of the hamedan province iran as determined from cylindrical punch point load and brazilian tests abstract in this research different experimental techniques have been used to determine the strength of five types of anisotropic foliated rocks selected from different parts of the hamedan province west of iran for this purpose after sample preparation and assessment of mineralogical and physical properties selected samples were subjected to cylindrical punch point load and brazilian tests and their strengths were evaluated with respect to different angles beta i e 0 15 30 45 60 75 and 90 between anisotropy planes and the major loading directions data analyses show that the types and amounts of minerals have an influence on the physical and mechanical properties of the tested anisotropic rocks porosity and water absorption also have a dominant control on the mechanical indices such as cylindrical punch index cpi point load index is 50 and brazilian tensile strength bts on the basis of the test result two empirical equations eqs 3 and 5 are proposed for calculating cpi and is 50 other empirical equations relating studied indices are also presented

holocene sea level history evidence from coastal sediments of the northern rio grande do norte coast ne brazil the holocene sea level history of the mesotidal northern rio grande do norte coast ne brazil was reconstructed from sedimentology and ams radiocarbon dating of beachrock and tidal lagoonal sediments at 7000 cal year bp at 3 m sea level stood and passed the modem sea level 6700 cal year ago the holocene highstand reached 1 3 m above modem sea level at 5900 cal year bp as determined by beachrock samples from the uppermost part of an intertidal foreshore deposit a 5700 cal year old shell midden overlies this beachrock that represents the spring tide sea level after the highstand sea level dropped to its present position beachrock samples from intertidal upper foreshore deposits were used for elevation and age control beachrock positions with their error bars are all within the tidal range envelope therefore no secondary oscillations during the sea level fall can be confirmed a linear sea level fall of this magnitude can be explained by the mechanism of equatorial ocean syphoning c 2005 elsevier b v all rights reserved

quaternary glaciations of the rongbuk valley tibet randomisation tests on boulder weathering data distinguish moraines of four different ages in the rongbuk valley all deposited by valley glaciers flowing northward into tibet from the himalaya lichenometry utilising subgenus rhizocarpon distinguishes two groups of moraines those 100 yr old and those older than several thousand years the degree of soil development has a similar limited utility in relative age dating these moraines the radiocarbon ages of calcium carbonate coatings in the lower horizons of moraine soils provide minimum limiting ages of 1900 yr bp for the penultimate advance of the rongbuk glacier samdopo moraine and 9500 yr bp for the rongbuk moraine the moraine suggested by previous workers to represent the last glacial maximum equilibrium line depression associated with the rongbuk moraine probably was slight 200 m the small magnitude of this depression relative to glaciers in other mountain ranges could relate to a weakening of the monsoon in full glacial times recent tectonic uplift and or to the insensitivity of these high altitude glaciers to lowering temperatures in the rain shadow of mount everest

crayfish burrows from late jurassic late cretaceous continental deposits of patagonia argentina their palaeoecological palaeoclimatic and palaeobiogeographical significance abstract the trace fossil loloichnus baqueroensis igen and isp nov from late jurassic late cretaceous continental deposits of patagonia argentina includes thickly lined mostly passively filled and y branched burrows other important features of this ichnofossil are the inner surface texture of lining showing transversal elongated and adjacent grooves and less commonly the pelletal filling of burrows l baqueroensis is recorded from the bajo grande bajo tigre punta del barco and laguna palacios formations which were deposited in different volcaniclastic environments of the deseado massif and san jorge basin geological provinces respectively the described burrows are found in many levels of palaeosols developed in reworked piroclastic deposits where they are the main component of the ichnofabrics in association with meniscate and thinly lined burrows and a diffuse and complex boxwork of small diameter burrows root traces are also present and in many cases occur inside l baqueroensis considering general morphology surface texture filling types palaeoenvironments in which they occur and comparisons with extant and fossil decapod burrows the likely trace makers of l baqueroensis were crayfishes decapoda astacidea probably parastacidae the producers of l baqueroensis inhabited soils where their burrows probably reached the water table and contained roots that were used for feeding considering climatic preferences of extant parastacids it is proposed a temperate climate for central patagonia during the deposition of the studied units the widespread presence of crayfishes during late jurassic late cretaceous times in central patagonia supports the monophyletic origin of this group during the triassic and suggests that the present restricted geographic distribution in southern south america is a relict of a broader one

postrift stress field inversion in the potiguar basin brazil implications for petroleum systems and evolution of the equatorial margin of south america rifting and related normal stress regime in the equatorial continental margin of brazil ceased during the late cretaceous when the stress regimes in eastern south america and west africa changed to induce strike slip or reverse motion in this study we explore the postrift tectonic geomorphic magmatic and sedimentary responses to stress changes using the potiguar basin the easternmost basin in the equatorial margin of brazil as a case study we use field and topographic data 2d seismic reflection lines vertical electric soundings and geochronological and borehole data to constrain the stress evolution of the potiguar basin from the late cretaceous to the quaternary discussing the role of basin inversion on sedimentation and landforms our results indicate the presence of two strike slip stress regimes after rifting the first stress field sf1 occurred from late cretaceous to the middle miocene and consisted of a n s oriented maximum subhorizontal compression and an e w oriented extension the second stress field sf2 took place from the middle miocene to the present day and included subhorizontal e w to nw se compression combined with n s and ne sw subhorizontal extension emplacement of volcanic rocks occurred along transtensional faults with a principal peak during sf1 at 20 30 ma and a subordinate peak during sf2 at 5 10 ma in response to shortening during sf2 a 70 km long and 50 km wide dome formed where marine miocene strata were uplifted to 250 m asl this uplift induced the displacement of alluvial channels away from the dome anticlines formed by transpression along the main ne sw striking faults during both sf1 and st2 acted as traps in the petroleum system similar shifts and stress field inversions documented in other areas of the brazilian continental margin are consistent with the neogene rise of the andes and may have implications for reconstructing the tectonic history of the equatorial atlantic margin of south america

thirty year history of glacier melting in the nepal himalayas 1 two net balance records of neighboring glaciers under different conditions are analyzed to extract temporal variations in glacier melting in the himalayas significant melt was observed every year at one site wet site whereas no melt occurred at the second site because of its high elevation dry site accumulation at the wet site of a glacier is estimated from the dry site neighboring another glacier through a measured precipitation record for a short time period the difference between the estimated accumulation and the net balances at the wet site is obtained as the melt index which represents the glacier melting conditions the melt index with an interannual timescale is significant as a climatic proxy at high elevation since no relationship between stable isotopes and temperature is established and few long term temperature records are available at high elevations in the himalayas the melt index showed a decadal fluctuation with a major amplitude never reported in previous studies with respect to temperature and ice cores analyses in the himalayas ice cores from a site where significant melt occurs every year have not been considered available in reconstructing past climates since climatic signals in ice were disturbed by meltwater infiltration however we suggest a new approach to glean temperature information by a combination of wet and dry cores not obtainable from a good quality ice core alone

fractal geometry in the san andreas fault system it has been noted that the spatial distribution of earthquakes and the mode of strain release in the san andreas fault system is related to the complexity of fault geometry because of their rough appearance over many length scales faults can be regarded as fractal surfaces direct estimates of fractal dimension d of portions of the san andreas fault system between the northern gabilan range and the salton sea including the postulated extent of the great 1857 fort tejon earthquake are obtained from measured fault lengths analogous to the lengths of coastlines as discussed by mandelbrot regions characterized by complicated fault geometry are associated with larger values of d based on fault traces mapped at a scale of 1 750 000 d is 1 3 for this reach of the fault defined as a 30 km wide band about a main fault trace for that part near parkfield which could be associated with the nucleation of the 1857 earthquake d is 1 1 at this same scale d is 1 4 for the san andreas and related faults near san bernardino where the 1857 rupture stopped compared to 1 2 for the san andreas san juan fault segments near the point of arrest of the 1966 parkfield earthquake at finer map scales 1 24 000 and 1 62 500 critical lengths of 500 m and 1 km are identified which might relate to the extent of off san andreas fault offsets the critical lengths also suggest that fault geometry is not self similar if this fractal geometry persists through the seismic cycle it may be possible to use a quantitative measure of complexity to explain the occurrence of great and characteristic earthquakes along a given reach of fault

a model based determination of spatial variation of precipitation δ18o over china abstract many works show the dependence of precipitation 18o on altitude and latitude as a result of air temperature change the assumption that these quantitative relations can hold across a large geographical region can be used to give a rough estimation of local precipitation 18o where there is on direct observation of precipitation 18o although there truly exists uncertainty in the estimation an effect was made in this paper to establish the precipitation 18o pattern over the whole china based on regional topography and the 18o of meteoric precipitation this paper established a quantitative relationship between 18o in precipitation and latitude and altitude using the existing 18o data from 55 sites over china the model describes as 18oppt 0 0073lat2 0 3261lat 0 0015alt 9 7776 and was used to generate a higher resolution map of mean annual 18o for precipitation over china using geographic information system software integrating with latitude altitude and the moisture cycle this determination of the spatial distribution of 18o in modern precipitation of china provides important information for ancient climate and stable isotope hydrology studies

neotectonic reactivation of shear zones and implications for faulting style and geometry in the continental margin of ne brazil abstract the eastern continental margin of south america comprises a series of rift basins developed during the breakup of pangea in the jurassic cretaceous we integrated high resolution aeromagnetic structural and stratigraphic data in order to evaluate the role of reactivation of ductile neoproterozoic shear zones in the deposition and deformation of post rift sedimentary deposits in one of these basins the paraiba basin in northeastern brazil this basin corresponds to the last part of the south american continent to be separated from africa during the pangea breakup sediment deposition in this basin occurred in the albian maastrichtian eocene miocene and in the late quaternary however our investigation concentrates on the miocene quaternary which we consider the neotectonic period because it encompasses the last stress field this consisted of an e w oriented compression and a n s oriented extension the basement of the basin forms a slightly seaward tilted ramp capped by a late cretaceous to quaternary sedimentary cover 100 400 m thick aeromagnetic lineaments mark the major steeply dipping ductile e w to ne striking shear zones in this basement the ductile shear zones mainly reactivated as strike slip normal and oblique slip faults resulting in a series of miocene quaternary depocenters controlled by ne e w and a few nw striking faults faulting produced subsidence and uplift that are largely responsible for the present day morphology of the valleys and tablelands in this margin we conclude that precambrian shear zone reactivation controlled geometry and orientation as well as deformation of sedimentary deposits until the neogene quaternary

wavelet analysis reveals periodic oscillations in a 1700 year ice core record from guliya china ice cores contribute important records of past climate changes as one of the thickest ice caps in central asia the guliya ice cap 35817 0 n 81829 0 e provides valuable information for this critical region about the past climate and environment changes we used wavelet analysis to examine periodic temperature and precipitation oscillations over the past 1700 years recorded in the guliya ice core the results show non linear oscillations in the ice core records with multiple timescales temperature records indicate persistent oscillations with periodicities of approximately 200 150 and 70 years precipitation records show significant periodicities at 200 100 150 and 60 years however the amplitude modulation and frequency vary with time wavelet analysis can explore these time series in greater detail and furnish additional useful information

evaluation of the anisotropy and directionality of a jointed rock mass under numerical direct shear tests abstract the characteristics of the anisotropy and directionality of jointed rock masses are the key to simplifying it as a transversely anisotropic material experimental direct shear tests were performed on stratified rocks cored from granulite rocks the influence of normal stresses and joint orientations was tested and the anisotropy and directionality of the shear strength were evaluated numerical shearing tests on stratified rock models and discrete fractures network dfn models were subsequently conducted in addition the shear anisotropy and directionality in the dfn models were tested and discussed the results demonstrate that the peak shear stress was more sensitive to the inclination angles than the normal stress the stratified rocks in the experimental test showed apparent shear anisotropy and directionality the maximum value of directionality coincided with the direction of the strike of the bedding plane the more apparent the anisotropy was the higher the directionality became the failure patterns of stratified rocks exhibited more complex characteristics under higher normal stress significant variation of the shear strength distribution occurred due to the different orientations of fractures relative to the directions of the shear load the failure patterns of dfn models of varied scales differed and no apparent convergence was discovered the shear strength of the dfn model showed an apparent principal direction the numerical results presented in this paper are valuable for evaluating the prediction of the failure behaviour of rock masses and can be further applied to the study of the failure mechanism of surrounding rock in engineering

time marker of 137cs fallout maximum in lake sediments of northwest china abstract caesium 137 137cs has no natural source and is commonly employed in establishing the chronology of recent lake sediments in the anthropocene epoch because of their location in the northern mid latitude westerlies circulation region downwind of the chernobyl accident and their proximity to the lop nur chinese nuclear testing cnt site lake sediments in nw china record a137cs fallout maximum of global atmospheric thermonuclear weapon tests gtwt in 1963 1964 common era ce with probably local fallout subpeaks due to the chernobyl accident in 1986 ce and cnt in 1976 ce this complexity means that the use of 137cs fallout maximum in lake sediments as a time marker in nw china is thus far not well constrained impeding assessment of recent and future changes in paleoclimate and human activities to identify the 137cs time marker and provide a reliable chronology of surface lake sediments for investigating paleoclimatic changes and for defining the anthropocene epoch in nw china during the last 50 100 years here we describe chronologies of 6 near surface sediment cores from nw china based on 137cs and 210pb activities and review the chronology of 23 lake sediments and 10 ice cores from nw china and central asia based on 137cs 210pb 239 240pu 3h 241am and beta activity dating methods and annual layer counting as well as 240pu 239pu isotopic ratios based on the potential influence of radioactivity transport from the chernobyl accident and cnt and the comparison with deposition records of 26 european lake sediments and 5 alpine ice cores we propose that the 137cs fallout maximum of lake sediments in nw china and central asia is primarily attributable to gtwt and that there is no unambiguous evidence to confirm the chernobyl and cnt derived 137cs local fallout subpeaks taking into account the approximately one year delay between injection of 137cs into the atmosphere and its incorporation in lake sediment records we conclude that the 137cs fallout maximum in lake sediments of nw china provides a reliable gtwt time marker for 1964 ce

use of the block punch test to predict the compressive and tensile strengths of rocks this study aimed to explore the applicability of the block punch test in estimating uniaxial compressive and brazilian tensile strengths of granite schist and sandstone from india it was experimentally shown that when predicting uniaxial compressive strength of rocks the block punch test is as useful as the point load test efficacy of the existing empirical equations for predicting uniaxial compressive strength by the block punch index was also evaluated prediction of brazilian tensile strength by block punch index appears to be more precise than by the point load strength performances of the existing strength anisotropy transformation factors in the literature in order to normalize the block punch index in the direction perpendicular to foliations were assessed based on the results of the tests performed on the schistose rocks

holocene late pleistocene climatic ice core records from qinghai tibetan plateau three ice cores to bedrock from the dunde ice cap on the north central qinghai tibetan plateau of china provide a detailed record of holocene and wisconsin wurm late glacial stage lgs climate changes in the subtropics the records reveal that lgs conditions were apparently colder wetter and dustier than holocene conditions the lgs part of the cores is characterized by more negative 18 o ratios increased dust content decreased soluble aerosol concentrations and reduced ice crystal sizes than the holocene part these changes occurred rapidly 10 000 years ago in addition the last 60 years were apparently one of the warmest periods in the entire record equalling levels of the holocene maximum between 6000 and 8000 years ago

intraplate earthquake swarm in belo jardim ne brazil reactivation of a major neoproterozoic shear zone pernambuco lineament summary intraplate earthquakes in stable continental areas have been explained basically by reactivation of pre existing zones of weakness stress concentration or both zones of weakness are usually identified as sites of the last major orogeny provinces of recent alkaline intrusions or stretched crust in ancient rifts however it is difficult to identify specific zones of weakness and intraplate fault zones are not always easily correlated with known geological features although northeastern brazil is one of the most seismically active areas in the country magnitudes 5 roughly every 5 yr with hypocentral depths shallower than 10 km and seismic zones as long as 30 40 km no clear relationship with the known surface geology can be usually established with confidence and a clear identification of zones of weakness has not yet been possible here we present the first clear case of seismic activity occurring as reactivation of an old structure in brazil the pernambuco lineament a major neoproterozoic shear zone the 2004 earthquake swarm of belo jardim magnitudes up to 3 1 and the recurrent activities in the nearby towns of sao caetano and caruaru magnitudes up to 4 0 and 3 8 show that the pernambuco lineament is a weak zone a local seismic network showed that the belo jardim swarm of 2004 november occurred by normal faulting on a north dipping e w oriented fault plane in close agreement with the e w trending structures within the pernambuco lineament the belo jardim activity was concentrated in a 1 5 km e w by 2 km downdip fault area and average depth of 4 5 km the nearby caruaru activity occurs as both strike slip and normal faulting also consistent with local structures of the pernambuco lineament the focal mechanisms of belo jardim caruaru and s caetano indicate e w compressional and n s extensional principal stresses the ns extension of this stress field is larger than that predicted by numerical models such as those of coblentz richardson and we propose that additional factors such as flexural stresses from the nearby sergipe alagoas marginal basin could also affect the current stress field in the pernambuco lineament

neotectonics in the south american passive margin evidence of late quaternary uplifting in the northern paraiba basin ne brazil abstract the relief evolution of several areas of northeastern brazil has been increasingly related to tectonic events this is the case for the paraiba basin where an abundance of faults and folds were recorded in neogene and even late pleistocene holocene deposits we tested whether dome like morphologies in the northern sector of this basin where geological exposures are scarce were also formed by tectonic deformation the work combined limited geological data with qualitative and quantitative analyses of the relief applying the 1 arc second digital elevation model provided by the shuttle radar topography mission the geomorphic indices of basin asymmetry factor af swath topographic profiles enhanced transverse hypsometry index thi and normalized river long profiles were used for validating a neotectonic origin for the dome like morphologies this interpretation was also supported by other morphological evidence of the dome relief including recurving channels featured in radial to recurved trellis patterns tectonically controlled drainage sub basins high relative relief values related to increased fluvial incision and anomalous river long profiles indicative of ungraded rivers the domic structures were attributed to fault and fold related strike slip deformation during the late quaternary this record supports the proposal that the south american passive margin remained under tectonic stress long after the main rifting in the late jurassic early cretaceous

characteristic trace fossils in nearshore to offshore sequences upper cretaceous of east central utah more than 20 trace fossil species occur in marine facies of the cretaceous star point and blackhawk formations in the book cliffs and wasatch plateau provinces of utah major genera include ancorichnus arenicolites aulichnites chondrites conichnus cylindrichnus medousichnus ophiomorpha palaeophycus planolites rosselia schaubcylindrichnus scolicia skolithos teichichnus teredolites and thalassinoides newly named taxa include ancorichnus capronus medousichnus loculatus and rosselia chonoides most trace fossils occur in characteristic albeit intergradational ichnofacies correlative with major lithofacies of regressive nearshore to offshore sequences the latter include foreshore foreshore shoreface transition shoreface and offshore facies landward facies are typified by clean well sorted well stratified sparsely burrowed sandstones seaward facies except where interrupted by hummocky bedded sandstones exhibit successively less pure less well sorted and stratified more intensely

rapid sea level fall and deep ocean temperature change since the last interglacial period we have dated huon peninsula papua new guinea and barbados corals that formed at times since the last interglacial period applying both 230 th and 231 pa dating techniques as a test of age accuracy we show that marine isotope stage mis 5e ended prior to 113 1 8 0 7 kyr when sea level was 319 m during mis 5b sea level was 357 m at 92 6 8 0 5 kyr having dropped about 40 m in approximately 10 kyr during the mis 5c 5b transition sea level then rose more than 40 m during the mis 5b 5a transition also in about 10 kyr mis 5a lasted until at least 76 2 8 0 4 kyr at a level of 324 m at that time combined with earlier data that places mis 4 sea level at 381 m at 70 8 kyr our late mis 5a data indicate that sea level fell almost 60 m in less than 6 kyr 10 6 m kyr during the mis 5 4 transition the magnitude of the drop is half that of the glacial interglacial amplitude and approximatelyequivalent to the volume of the present dayantarctic ice sheet during this interval the minimum average rate of net continental ice accumulation was 18 cm yr likely facilitated by efficient moisture transport from lower latitudes at three specific times 60 6 8 0 3 50 8 8 0 3 and 36 8 0 2 kyr during mis 3 sea level was between 385 and 374 m sea level then dropped to 3107 m at 23 7 8 0 1 kyr early in mis 2 before dropping further to last glacial maximum lgm values and then rising to present values during the last deglaciation times of rapid sea level drop correspond to times of high winter insolation at low northern latitudes and high winter latitudinal gradients in northern hemisphere insolation supporting the idea that these factors mayhave resulted in high water vapor pressure in moisture sources and efficient moisture transport to high latitude glaciers therebycontributing to glacial buildup we combined our sea level results with deep sea n 18 o records as a means of estimating the temperature and ice volume components in the marine n 18 o record this analysis confirms large deep ocean temperature shifts following mis 5e and during termination i deep ocean temperatures changed bymuch smaller amounts between mis 5c and 2 maximum temperature shift in the deep pacific is about 2 whereas the shift at a site in the atlantic is 4 under glacial conditions temperatures at both sites are near the freezing point the shift in the atlantic is likelycaused bya combination of changing proportions of northern and southern source waters as well as changing temperature at the sites where these deep waters form

non steady long term uplift rates and pleistocene marine terrace development along the andean margin of chile 31 s inferred from 10be dating pleistocene uplift of the chilean coast is recorded by the formation of wave cut platforms resulting from marine erosion during sea level highstands in the altos de talinay area 31 s we have identified a sequence of 5 wave cut platforms using in situ produced 10be exposure ages we show that these platforms were formed during interglacial periods at 6 122 232 321 and 690 ka these ages correspond to marine isotopic stages mis or substages miss 1 5e 7e 9c and 17 shoreline angle elevations used in conjunction with our chronology of wave cut platform formation illustrate that surface uplift rates vary from 103 69 mm ka between 122 and 6 ka to 1158 416 mm ka between 321 and 232 ka the absence of preserved platforms related to the mis 11 13 and 15 highstands likely reflects slow uplift rates during these times we suggest that since 700 ka the altos de talinay area was predominantly uplifted during 2 short periods following mis 17 and miss 9c this episodic uplift of the chilean coast in the pleistocene may result from subduction related processes such as pulses of tectonic accretion at the base of the forearc wedge

composite ichnofabrics and tiering of burrows infaunal communities in marine environments typically are tiered that is different taxa live at different depths within the sediment tiered suites of biogenic structures yield complex biogenic sedimentary fabrics ichnofabrics with the traces of deep burrowing organisms overprinted on those of shallow burrowing organisms careful analysis of crosscutting relationships of burrows in such composite ichnofabrics allows reconstruction of the tiered nature of fossil endobenthic communities it is important to recognize that the best preserved and most prominently displayed trace fossils in most assemblages usually represent the deepest tier thus they were farther removed from the sea floor and therefore less indicative of actual sea floor conditions than the more poorly preserved traces of the shallower tiers on which the deeper traces are juxtaposed

oxygen isotopic and soluble ionic composition of a shallow firn core inilchek glacier central tien shan oxygen isotopic and soluble ionic measurements made on snow pit 2 m depth and firn core 12 4 m depth samples recovered from the accumulation zone 5100 m of inilchek glacier 43 n 79 e provide information on recent 1992 98 climatic and environmental conditions in the central tien shan region of central asia the combined 14 4 m snow pit firn core profile lies within the firn zone and contains only one observed melt feature 10 m temperature 12 c although some post depositional attenuation of the sub seasonal 18 o record is possible annual cycles are apparent throughout the isotope profile we therefore use the preserved 18 o record to establish a depth age scale for the core mean 18 o values for the entire core and for summer periods are consistent with 18 temperature observations and suggest the 18 o record provides a means to reconstruct past changes in summer surface temperature at the site major ion na k mg 2 ca 2 nh 4 cl no 3 so 4 2 data from the core demonstrate the dominant influence of dust deposition on the soluble chemistry at the site and indicate significant interannual variability in atmospheric dust loading during the 1990s anthropogenic impacts on nh 4 concentrations are observed at the site and suggest a summer increase in atmospheric nh 4 that may be related to regional agricultural nitrogen rich fertilizer use activities

relative sea level fall since the last interglacial stage are coasts uplifting worldwide the growing interest in quantification of vertical ground motion stems from the need to understand in detail how the earth s crust behaves for both scientific and social reasons however only recently has the refinement of dating techniques made possible the use of paleoshorelines as reliable tools for tectonic studies although there are many local studies of quaternary vertical motions of coastlines we know of no comprehensive worldwide synthesis here we provide a compilation of 890 records of paleoshoreline sequences with particular emphasis on the last interglacial stage marine isotopic stage mis 5e 122 ka the quality of dating mis 5e makes it a reliable marker to evaluate vertical ground motion rates during the late quaternary on a global scale the results show that most coastal segments have risen relative to sea level with a mean uplift rate higher than 0 2 mm yr i e more than four times faster than the estimated eustatic drop in sea level the results also reveal that the uplift rate is faster on average for active margins than for passive margins neither dynamic topography nor glacio hydro isostasy may explain sustained uplift of all continental margins as revealed by the wide distribution of uplifted sequences of paleoshorelines instead we suggest that only plate tectonic processes reconcile all observations of quaternary coastal uplift we propose that long term continental accretion has led to compression of continental plates and uplift of their margins therefore this study concludes that plate tectonics processes impact all margins and emphasizes the fact that the notion of a stable platform is unrealistic these results therefore seriously challenge the evaluation of past sea levels from the fossil shoreline record

holocene sea level history on the rio grande do norte state coast brazil abstract the rio grande do norte state coast northeastern brazil lies in an intraplate region which displays elevated holocene shorelines abandoned tidal flats and other intertidal deposits a field and chronological investigation which used 48 radiocarbon dates on unaltered mollusk shells peats coral reefs and vermetids in living position and death assemblages encrusted on beachrock tidal flat and peat deposits was carried out along two littoral zones one trending east west and the other north south the sea level envelope curve for the region indicates at least one sea level oscillation after the maximum holocene highstand which occurred at 5000 cal yr bp this curve shows notable deviations from the mean sea level curve for the central brazilian coast in the early and mid holocene however in general this envelope curve fits a glacio isostatic prediction for the area a significant deviation from this prediction related to a small sea level oscillation occurred from 2100 to 1100 cal yr bp the comparison between the glacio isostatic prediction and the sea level observation enables us to conclude that local events may have disturbed the sea level record minor holocene sea level oscillations which were mainly associated with climate changes or tectonics and superimposed on a major smooth pattern were observed in south africa and australia but in northeastern brazil neotectonic controlled crustal movements or variation in marine and wind currents could provide the answer the data indicate that local events may have an important role in the history of coastal progradation and retreat