gcm analysis of local influences on ice core δ signals a high resolution gcm is used to examine the effect of changes in local surface climate parameters on the ice sheets that can influence the interpretation of the isotopic signal of the ice from deep cores the model suggests that the 10 c difference between the lgm surface temperature deduced from borehole thermometry and that deduced from the water isotope analysis to a great extent may be due to a modification of the precipitation seasonality in central greenland for central east antarctica the model tends to suggest a weak opposite bias

doppler profiler and radar observations of boundary layer variability during the landfall of tropical storm gabrielle abstract detailed observations of boundary layer structure were acquired on 14 september 2001 prior to and during the landfall of tropical storm gabrielle the mobile integrated profiling system mips and the shared mobile atmospheric research and teaching radar smart r were collocated at the western florida coastline near venice very close to the wind center at landfall prior to landfall the boundary layer was rendered weakly stable by a long period of evaporational cooling and mesoscale downdrafts within extensive stratiform precipitation that started 18 h before landfall the cool air mass was expansive with an area within the 23 c surface isotherm of about 50 000 km2 east northeasterly surface flow transported this cool air off the west coast of florida toward the convergent warm core of the gabrielle and promoted the development of shallow warm and cold fronts that were prominent during the landfall phase airflow properties of the boundary layer around the coastal zone are examined using

north atlantic hurricanes 1977 99 surface hurricane force wind radii abstract the hurricane research division noaa amol hrd flight level data archive of 1977 99 north atlantic hurricanes is used to create radial profiles of earth relative surface wind speeds radii of hurricane force winds are determined directly from these generated profiles the distributions of hurricane force wind radii stratified by minimum central pressure and quadrant relative to the direction of storm motion indicate marked variability among storms however a model which uses storm parameters to predict the radius of hurricane force winds in a given quadrant of a hurricane does seem feasible roughly three quarters of the variance in the hurricane force wind radii of minimal hurricanes and about one half of the variance in the hurricane force wind radii of major hurricanes is explained by parameters of the storm enough to make a predictive model of significant value in addition cumulative two dimensional probability distributions of hurricane force wind radii may have some utility for hurr

the boundary layer winds in hurricanes danielle 1998 and isabel 2003 abstract this paper describes the boundary layer wind structure and dynamics of hurricanes danielle 1998 and isabel 2003 based on the analysis of high resolution global positioning system dropwindsonde data and simulation of the flow by a three dimensional boundary layer model produced by kepert and wang the observations show that the hurricane boundary layer has a complex three dimensional structure with large variability over small distances the analysis emphasizes three aspects the degree of gradient wind balance the radially varying depth of the boundary layer and the strength of the near surface wind speed relative to that at a higher level each aspect is compared both with results obtained in a simulation of the individual storm by kepert and wang s model and with theoretical predictions the observations show that the boundary layer depth decreases toward the center of the storm consistent with theoretical arguments the strongest azimuthal winds occur near the top of but still within

effects of vertical eddy diffusivity parameterization on the evolution of landfalling hurricanes abstractas a result of rapid changes in surface conditions when a landfalling hurricane moves from ocean to land interactions between the hurricane and surface heat and moisture fluxes become essential components of its evolution and dissipation with a research version of the hurricane weather research and forecasting model hwrf this study examines the effects of the vertical eddy diffusivity in the boundary layer on the evolution of three landfalling hurricanes dennis katrina and rita in 2005 specifically the parameterization scheme of eddy diffusivity for momentum km is adjusted with the modification of the mixed layer velocity scale in hwrf for both stable and unstable conditions results show that the change in the km parameter leads to improved simulations of hurricane track intensity and quantitative precipitation against observations during and after landfall compared to the simulations with the original km further diagnosis shows that compared to original km the modified km produces

geochemistry of shales from the archean 3 0 ga buhwa greenstone belt zimbabwe implications for provenance and source area weathering abstract phyllites from the archean 3 0 ga buhwa greenstone belt zimbabwe were deposited on a stable cratonic platform analyses of the phyllites generally define a single geochemical group based on major and trace element abundances the phyllites are strongly depleted in cao na2o and sr with respect to average archean upper crust by contrast k2o ba and rb are enriched several times relative to average archean upper crust reflecting basin scale k metasomatism transition metals are somewhat depleted whereas high field strength elements are typically enriched relative to average archean upper crust samples generally have fractionated lree patterns average cen smn 2 4 with small negative eu anomalies average eu eu 0 78 and generally flat hrees average gdn ybn 1 3 such geochemical characteristics suggest that the source dominantly consisted of tonalite with less common occurrences mafic volcanic rocks and granite mixing calculations which massbalance the rees and th sc suggest 70 tonalite 15 mafic volcanic rocks and 15 granite as possible proportions for the source of the phyllites a nearby early archean 3 5 ga continental nucleus preserves similar lithologies and is the probable source intense chemical weathering of the source terrane is indicated by premetasomatized chemical index of alteration values of 95 100 nearly complete depletion of cao and na2o and high al2o3 na2o ratios fine grained sediments of comparable age and presumed tectonic setting elsewhere in southern africa show similar geochemical characteristics implying that source area compositions and weathering intensities were similar these mature platformal deposits suggest a tectonically stable environment where intense chemical weathering took place at 3 0 ga across southern africa

major features and forcing of high latitude northern hemisphere atmospheric circulation using a 110 000 year long glaciochemical series the greenland ice sheet project 2 glaciochemical series sodium potassium ammonium calcium magnesium sulfate nitrate and chloride provides a unique view of the chemistry of the atmosphere and the history of atmospheric circulation over both the high latitudes and mid low latitudes of the northern hemisphere interpretation of this record reveals a diverse array of environmental signatures that include the documentation of anthropogenically derived pollutants volcanic and biomass burning events storminess over marine surfaces continental aridity and biogenic source strength plus information related to the controls on both high and low frequency climate events of the last 110 000 years climate forcings investigated include changes in insolation of the order of the major orbital cycles that control the long term behavior of atmospheric circulation patterns through changes in ice volume sea level events such as the heinrich events massive discharges of icebergs first identified in the marine record that are found to operate on a 6100 year cycle due largely to the lagged response of ice sheets to changes in insolation and consequent glacier dynamics and rapid climate change events massive reorganizations of atmospheric circulation that are demonstrated to operate on 1450 year cycles changes in insolation and associated positive feedbacks related to ice sheets may assist in explaining favorable time periods and controls on the amplitude of massive rapid climate change events explanation for the exact timing and global synchroneity of these events is however more complicated preliminary evidence points to possible solar variability climate associations for these events and perhaps others that are embedded in our ice core derived atmospheric circulation records

petrology chemistry and texture of modern river sands amazon river system key idea following the spirit of p d krynine the sands of the world s largest tropical river system are studied to reveal much about the general origin of sand and sandstone thin section and chemical study of 95 sand samples from the amazon river system in brazil peru ecuador and colombia a river system with great contrasts in climate and rock types reveals that sands derived from the andes are lithic arenites whereas sands derived from precambrian terrains are much richer in quartz as are sands in rivers draining tertiary molasse sand becomes more mature downstream along the main stem of the amazon solimoes maranon so that a sample analyzed at the mouth does not accurately reflect headwater composition dilution by quartz rich tributaries and quartz rich tertiary outcrops possible differential elimination of rock fragments and even possible weathering on the modern flood plain of the amazon contribute to enhanced maturity downstream we speculate that although data on modern large subarti

observations of the structure and evolution of surface and flight level wind asymmetries in hurricane rita 2005 1 knowledge of the magnitude and distribution of surface winds including the structure of azimuthal asymmetries in the wind field are important factors for tropical cyclone forecasting with its ability to remotely measure surface wind speeds the stepped frequency microwave radiometer sfmr has assumed a prominent role for the operational tropical cyclone forecasting community an example of this instrument s utility is presented here where concurrent measurements of aircraft flight level and sfmr surface winds are used to document the wind field evolution over three days in hurricane rita 2005 the amplitude and azimuthal location phase of the wavenumber 1 asymmetry in the storm relative winds varied at both levels over time the peak was found to the right of storm track at both levels on the first day by the third day the peak in flight level storm relative winds remained to the right of storm track but it shifted to left of storm track at the surface resulting in a 60 degree shift between the surface and flight level and azimuthal variations in the ratio of surface to flight level winds the asymmetric differences between the surface and flight level maximum wind radii also varied indicating a vortex whose tilt was increasing

glaciochemistry of polar ice cores a review human activities have already modified the chemical composition of the natural atmosphere even in very remote regions of the world the study of chemical parameters stored in solid precipitation and accumulated on polar ice sheets over the last several hundred thousand years provides a unique tool for obtaining information on the composition of the preindustrial atmosphere and its natural variability over the past this paper deals with the chemistry of polar ice focused on the soluble mineral na nh4 k ca mg h f cl no3 so4 and h2o2 and organic methanesulfonate ch3so3 formate hcoo acetate ch3coo and formaldehyde hcho species and their interpretation in terms of past atmospheric composition aerosols and water soluble gaseous species we discuss ice core dating the difficulties connected with trace measurements and the significance of the ionic composition of snow we examine temporal from the last decades back to the last climatic cycle and spatial including examples from coastal as well as central areas of greenland and antarctica variations in the ionic budget of the precipitation and evaluate ice core studies in terms of the chemical composition of our past atmosphere we review 1 how greenland and antarctic ice cores that span the last few centuries have provided information on the impact of human activities and 2 how the chemistry of deep ice cores provides information on various past natural phenomena such as climatic variations glacial interglacial changes el nino volcanic eruptions and large boreal forest fires

major features of glaciochemistry over the last 110 000 years in the greenland ice sheet project 2 ice core major chemical species cl no3 so42 na nh4 k mg2 ca2 and 18o covering the last 110 000 years from the greenland ice sheet project 2 gisp2 ice core were utilized in this study in order to reconstruct the soluble chemistry of the atmosphere over greenland and interpret major climate events that have affected the region during the holocene the major chemical species and 18o do not display any significant relationship however a strong inverse correlation was found between concentrations of the major chemical species and 18o a proxy for temperature during the last glacial period suggesting that in general during periods of decreased temperature there is an increase in atmospheric chemical loading examination of changes in major chemical composition over the last 110 000 years of the gisp2 ice core reveals that during the holocene the atmosphere was acidic during inters t adials the atmosphere was neutral or alkalescent and during stadials the atmosphere was alkaline in addition the relative abundance of major chemical species varied during the holocene stadials and interstadials during the holocene nh4 and no3 are the dominant cations and anions while ca2 and so42 are the dominant cations and anions during the stadials and inters t adials this suggests that source regions or types differed between the holocene and the last glacial period in addition changes in chemical composition and changes in chemical ratios also indicate that source regions differed during the holocene stadials and interstadials twenty four previously identified dansgaard oeschger stadial interstadial events dansgaard et al 1993 were in the gisp2 chemical series the duration of the stadials is inversely correlated with variations in sea level over the last glacial period i e the more extensive the northern hemisphere ice sheet the longer the duration of the stadial there is also a close correspondence between the duration of interstadials and the timing of heinrich events massive icebergs discharged into the ocean in the gisp2 ice core long up to 2000 years warm periods follow each heinrich event suggesting perhaps that enhanced deep water circulation is re initiated following heinrich events

composition of plagioclase feldspar in modern deep sea sands relationship to tectonic setting microprobe analysis of plagioclase in deep sea sands from various tectonic settings gives averages ranging from 19 an for trailing edge continental margins to 56 an for basins on the ocean side of an island arc for each setting except island arcs anomalously high amounts of pure albite are found these albitic grains may be recycled from pre existing sedimentary rocks potassium rich plagioclase thought to be indicative of a volcanic provenance is less abundant than would be expected from the proportion of volcanic rock fragments perhaps such high k plagioclases are less resistant to weathering than low k plagioclase

effects of postdepositional processing on nitrogen isotopes of nitrate in the greenland ice sheet project 2 ice core records of ice core nitrate and its isotopes hold the potential to assess past atmospheric conditions regarding nox and oxidant levels however relating such records to past atmospheric conditions requires a site specific understanding of the postdepositional processing of snow nitrate we report 15n no3 records from the greenland ice sheet project 2 gisp2 ice core over major climate transitions model calculations and comparison with records of parameters influencing uv driven postdepositional processing of snow nitrate suggest that the observed variability in gisp2 15n no3 over major climate transitions is primarily driven by changes in the degree of postdepositional loss of snow nitrate estimates of the fractional loss of snow nitrate is 16 23 in the holocene and 45 53 in the glacial period suggesting a 41 32 lower nitrate depositional flux to greenland during the glacial period relative to the holocene

numerical study on the development of asymmetric convection and vertical wind shear during tropical cyclone landfall idealized simulations on an f plane of tropical cyclone tc landfall under a quiescent environment in the southern hemisphere are performed to investigate the effects of land sea surface contrast on precipitation in the control simulation with realistic roughness and moisture over land to the south of the tc the simulated vortex moves toward land due to a land induced steering flow the abrupt decrease increase of tangential wind at the surface leads to convergence divergence on the onshore offshore flow side enhanced convergence at the top of the planetary boundary layer is found on both onshore and offshore sides and is caused by advection from the surface and the enhanced offshore radial wind the boundary layer top convergence pattern is consistent with the rainfall distribution vertical wind shear develops during the landfall process associated with the low and upper level asymmetric flows across the model domain the wavenumber 1 like low level asymmetric flow is introduced by an asymmetric geopotential height field that is generated by the large area of frictionally induced convergence on the onshore side and divergence on the offshore side the upper level asymmetric flow is attributed to asymmetric convection and associated diabatic heating after landfall most rainfall is found in the down shear right quadrant which is consistent with previous studies that focused on the effect of environmental shear although the existence of feedback from the vertical wind shear to rainfall remains an open question the relation between maximum rainfall and vertical wind shear is robust especially when the shear magnitude is large after landfall

sandstone provenance of north western sectors of the intracontinental cenozoic qaidam basin western china tectonic vs climatic control abstract sandstone samples from all cenozoic formations of the nonmarine internally drained qaidam basin have been collected for provenance analysis to monitor possible changes in sandstone composition driven either by tectonics or climate provided an appropriate hinterland biotite contents may be a reasonable indicator for aridity moderately sorted sandstones with subangular to subrounded grains from the northwestern part of the qaidam basin are immature indicated by a high proportion of feldspars and lithic fragments nevertheless they have relatively high quartz contents of 29 65 averaging between 40 and 45 the average framework compositions of the formations show only a slight variation over time limited to the oldest and youngest cenozoic formations contents of white mica and biotite are significantly higher in upper portions of the section white mica contents increases from 1 0 to 3 7 and biotite from 0 1 to 1 6 respectively this change can be explained by increasing aridity during neogene and surface uplift of altyn mountains and qimantagh which led to higher relief when plotted on basic variation diagrams total quartz feldspar lithic fragments there is a slight shift from continental block field to orogenic field which might reflect the motion of the altyn tagh fault since oligocene times although climate changed during the cenozoic from arid over semiarid back to arid we could not find any distinct changes in the framework mineral compositions over time that could be related to climatic events few selected mudstones from eocene to lower miocene formations have been geochemically analysed by icp ms all samples display uniform high enrichment in light rees in chondrite normalized diagrams with one exception the ree concentrations are decreasing in a stepwise manner although insignificantly from formation to formation with time due to a diluting effect by carbonate

asymmetric structures in a simulated landfalling hurricane abstract highly asymmetric structures in a landfalling hurricane can lead to the formation of heavy rains wind gusts and tornados at prefered locations relative to the center of the hurricane in this study the development of asymmetric structures in an explicitly simulated idealized hurricane during landfall was investigated it was found that the boundary layer friction and its associated convection produce a low level positive potential vorticity pv band ahead of the hurricane the interaction between the pv band and the eyewall pv ring leads to a temporary weakening and reintensifying cycle asymmetric structures arise from the near discontinuity of the surface friction and the latent heat flux the breaking of the eyewall in the rear quadrants is favorable for the intrusion of the low moist entropy air into the core consequently pv increases significantly in the core in and just above the boundary layer due to the stabilization after the hurricane makes landfall the diabatic heating in the

abrupt increase in greenland snow accumulation at the end of the younger dryas event the warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate the best known of which is the younger dryas event1 despite much study of the causes of this event and the mechanisms by which it ended many questions remain unresolved1 oxygen isotope data from greenland ice cores2 4 suggest that the younger dryas ended abruptly over a period of about 50 years dust concentrations2 4 in these cores show an even more rapid transition 20 years this extremely short timescale places severe constraints on the mechanisms underlying the transition but dust concentrations can reflect subtle changes in atmospheric circulation which need not be associated with a large change in climate here we present results from a new greenland ice core gisp2 showing that snow accumulation doubled rapidly from the younger dryas event to the subsequent preboreal interval possibly in one to three years we also find that the accumulation rate change from the oldest dryas to the bo11ing allerod warm period was large and abrupt the extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the north atlantic climate system

infiltrated clays in fluvial jurassic sandstones of reconcavo basin northeastern brazil abstract fluvial sandstones and conglomerates of the sergi formation a jurassic unit of reconcavo basin northeastern brazil contain significant amounts of interstitial detrital clays which are interpreted as the product of early mechanical infiltration developed in an arid semi arid environment within such an environment the lowered water table allowed muddy waters of episodic runoff to infiltrate through the coarse alluvium concentrating the clays in the upper phreatic zone near the sources of influent seepage petrographic textures considered to be typical of mechanically infiltrated mi clays are herein presented using examples from the sergi formation these textures include 1 ridges and bridges 2 geopetal fabrics 3 loose aggregates 4 anisopachous coatings of tangentially accreted lamellae cutans 5 massive aggregates and 6 shrinkage patterns developed during diagenesis in addition their detrital aspect as revealed by sem observations and the presence of impurities in the interior of the clay aggregates were also used as evidence for the interpreted origin of the clays in most hydrocarbon reservoirs in the sergi formation the clays described in this paper are among the main controls on porosity and permeability distribution commonly zones with maximum clay concentration are the main internal permeability barriers within the sergi formation reservoirs

the transition of the hurricane frederic boundary layer wind field from the open gulf of mexico to landfall abstract numerous aircraft ship buoy and land nation data were composited with respect to the center of hurricane frederic for two time periods a 24 h period corresponding to the storm s position in the open gulf of mexico on 12 september 1979 and an 8 h period corresponding to the landfall of frederic near 0400 gmt on 13 september comparison of wind analyses for the two periods indicated a rotation of maximum inflow angles from the southeast to northeast quadrants and a strong frictional decrease of wind speed over land them and other features of the landfall analysis were compared with a model landfall study by moss and jones 1978 the landfall composite wind field was compared with the fujita damage vector analysis to determine the damage time interval and mean wind speed range damage vector directions were found to be well correlated with the surface streamlines with the most severe damage being associated with frederic s northern eyewall ten meter level wind speed data over water vo and

anomalous nitrogen isotopes in ultrahigh pressure metamorphic rocks from the sulu orogenic belt effect of abiotic nitrogen reduction during fluid rock interaction modern nitrogen n fixation is primarily mediated by biological processes however in the early earth where biological activity was absent or limited abiotic n reduction in hydrothermal systems is thought to be a key process to transform atmospheric n2 and nox to ammonium an essential nutrient to support the emergence of life and also an n form that can be incorporated into rocks surprisingly evidence for abiotic n reduction in the rock record has not been clearly identified in this study we reported anomalously low n isotope compositions n15 values as low as 15 8 15 8 of mica samples in ultrahigh pressure metamorphic rocks from the donghai area in the sulu orogenic belt eastern china compared with mica samples with typical crustal n15 values 3 9 3 9 in similar metamorphic rocks from the western dabie orogen the 15n depleted mica samples from the sulu orogen are characterized by significant n enrichment 10 times higher and extreme 18o depletion o18 values as low as 9 9 these features can be best explained by assimilation of n from a source characterized by extremely low n15 values less than 16 16 the extremely low n15 value would be produced by abiotic n reduction during reaction of a meteoric hydrothermal fluid with crustal rocks before subduction this observation provides a clue to the occurrence of abiotic n reduction in continental supracrustal rocks and infer that abiotic n reduction process could be a fundamental process driving the geological n cycling in early earth

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

oxygen isotope and palaeotemperature records from six greenland ice core stations camp century dye 3 grip gisp2 renland and northgrip oxygen isotope variations spanning the last glacial cycle and the holocene derived from ice core records for six sites in greenland camp century dye 3 grip gisp2 renland and northgrip show strong similarities this suggests that the dominant influence on oxygen isotope variations reflected in the ice sheet records was regional climatic change differences in detail between the records probably reflect the effects of basal deformation in the ice as well as geographical gradients in atmospheric isotope ratios palaeotemperature estimates have been obtained from the records using three approaches i inferences based on the measured relationship between mean annual 18o of snow and of mean annual surface temperature over greenland ii modelled inversion of the borehole temperature profile constrained either by the dated isotopic profile or iii by using monte carlo simulation techniques the third of these approaches was adopted to reconstruct holocene temperature variations for the dye 3 and grip temperature profiles which yields remarkably compatible results a new record of holocene isotope variations obtained from the northgrip ice core matches the grip short term isotope record and also shows similar long term trends to the dye 3 and grip inverted temperature data the northgrip isotope record reflects i a generally stronger isotopic signal than is found in the grip record ii several short lived temperature fluctuations during the first 1500 yr of the holocene iii a marked cold event at ca 8 2 ka the 8 2 ka event iv optimum temperatures for the holocene between ca 8 6 and 4 3 ka a signal that is 0 6 stronger than for the grip profile v a clear signal for the little ice age and vi a clear signal of climate warming during the last century these data suggest that the northgrip stable isotope record responded in a sensitive manner to temperature fluctuations during the holocene copyright 2001 john wiley sons ltd

first record of marine bivalves from the talchir formation of the satpura gondwana basin india palaeobiogeographic implications abstract marine invertebrate fossils are rarely reported from the permian talchir formation of the intracontinental gondwana basins of peninsular india they are known to occur in umaria and manendragarh rewa basin daltonganj and rajhara daltonganj basin and dudhi nala bokaro basin the fossil assemblages include bivalves brachiopods gastropods polyplacophora crinoids bryozoans foraminifers ostracods conulariids etc the fossil localities define a roughly e w trending linear belt along the present day river valleys of son narmada damodar accordingly the existence of a marine embayment within the indian peninsula along this belt during permian time was inferred which extended westward up to the rewa basin this study reveals for the first time occurrence of marine invertebrate fossils within the hlchir formation of the satpura basin which is located further west of the presently known belt of marine fossils the fossil assemblage of the satpura basin includes bivalves ostracods and foraminifers along with floral remains in this present endeavor i describe two bivalve species praeundolornya subelongata dickins 1963 and eurydesrna sp juv this finding implies that the permian marine embayment of the indian peninsula extended further west than that was so far thought to be

comparison of oxygen isotope records from the gisp2 and grip greenland ice cores recent results1 2 from the greenland ice core project grip summit ice core suggest that the climate in greenland has been remarkably stable during the holocene but was extremely unstable for the time period represented by the rest of the core spanning the last two glaciations and the intervening eemian inter glacial here we present the complete oxygen isotope record for the greenland ice sheet project 2 gisp2 core drilled 28 km west of the grip core we observe large rapid climate fluctuations throughout the last glacial period which closely match those reported for the grip core however in the bottom 10 of the cores spanning the eemian interglacial and the previous glacia tion there are significant differences between the two records it is possible that ice flow may have altered the chronological sequences of the stratigraphy for the bottom part of one or both of the cores considerable further work will be necessary to evaluate the likelihood of this and the extent to which it will still be possible to extract meaningful climate information from the lowest sections of the cores

low level kinematic thermodynamic and reflectivity fields associated with hurricane bonnie 1998 at landfall during 11 h on 26 august 1998 two noaa wp 3d aircraft deployed 85 global positioning system gps dropwindsondes within 2 of latitude of the circulation center of hurricane bonnie as it made landfall in north carolina about 75 of the sondes successfully collected data which were used to create a series of storm relative horizontal maps of kinematic and thermodynamic variables from 10 m to 2 km reflectivity fields were analyzed from the weather surveillance radar 1988 dopplers wsr 88ds located at wilmington and morehead city north carolina and the tail and lower fuselage radars aboard the wp 3ds gps sonde performance and deployment spacing is adequate to identify several aspects of the vortex these include 1 warm dry stable air in the offshore flow that results in reduced equivalent potential temperatures entering the southern portion of the eyewall 2 cooler air collocated with the upwelled water in the right rear quadrant and under the eyewall and 3 an atypical radial wind pattern with strong inflow southwest of the circulation center and outflow northeast of the center the strongly asymmetric structure found at 10 m becomes much more homogeneous by 2 km altitude no intense rainbands developed over land in the onshore flow nor did the bands in the onshore flow undergo any significant changes once they made landfall beyond the eyewall the offshore flow contained much less precipitation than the onshore portion of the storm characteristics beyond the eyewall appear to have been modulated by the proximity to land but hurricane intensity did not vary the authors infer that the lower energy content of the inflow was offset by the contraction of the eyewall

the effects of complex terrain on severe landfalling tropical cyclone larry 2006 over northeast australia abstract the interaction between complex terrain and a landfalling tropical cyclone tc over northeastern australia is investigated using the fifth generation pennsylvania state university national center for atmospheric research psu ncar mesoscale model mm5 severe tc larry in march 2006 made landfall over an area of steep coastal orography and caused extensive damage the damage pattern suggested that the mountainous terrain had a large influence on the tc wind field with highly variable damage across relatively small distances the major aims in this study were to reproduce the observed features of tc larry including track intensity speed of movement size decay rate and the three dimensional wind field using realistic high resolution terrain data and a nested grid with a horizontal spacing of 1 km for the finest domain referred to as ctrl and to assess how the above parameters change when the terrain height is set to zero notopog the tc track for ctrl including the timing and locat

polarimetric radar observations of the persistently asymmetric structure of tropical cyclone ingrid abstract tropical cyclone ingrid had a distinctly asymmetric reflectivity structure with an offshore maximum as it passed parallel to and over an extended coastline near a polarimetric weather radar located near darwin northern australia for the first time in a tropical cyclone polarimetric weather radar microphysical analyses are used to identify extensive graupel and rain hail mixtures in the eyewall the overall microphysical structure was similar to that seen in some other asymmetric storms that have been sampled by research aircraft both environmental shear and the land sea interface contributed significantly to the asymmetry but their relative contributions were not determined the storm also underwent very rapid changes in tangential wind speed as it moved over a narrow region of open ocean between a peninsula and the tiwi islands the time scale for changes of 10 m s 1 was of the order of 1 h there were also two distinct types of rainbands observed large scale principal bands with embedded d

geochemistry of permo triassic mudstone of the satpura gondwana basin central india clues for provenance abstract major and trace element data of the permo triassic mudstones from the intracratonic satpura gondwana basin central india have been used to investigate provenance the satpura succession 5 km thick unconformably overlies the precambrian basement sediment dispersal pattern suggests that the precambrian rocks straddling the southern margin of the satpura basin were the most probable source for the sediments the lowermost unit of the satpura succession comprises glacio marine and glacio fluvial deposits the rest of the succession largely represents a variety of fluvial depositional systems with some records of fluvio deltaic and fluvio lacustrine sedimentation under a climatic spectrum of temperate humid to warm semi arid the present study is confined to the lower six formations namely talchir barakar motur bijori pachmarhi and denwa arranged in that order from bottom to top the oldest rocks of this sequence the talchir formation are enriched in mobile elements such as na ca and mg depleted in alumina and have high icv 0 93 1 29 and lower cia values 61 82 74 89 compared to those of the younger mudstones k 2 o al 2 o 3 ratios of the talchir mudstones 0 24 0 28 are higher than the younger mudstones in this sequence these results suggest that the talchir mudstones were weathered less intensely and are thus more immature than the younger mudstones this is consistent with the prevailing cold climate and relatively higher rate of basin subsidence in contrast the majority of the mudstones from the younger formations are depleted in mobile elements have relatively low icv 0 18 0 87 and k 2 o al 2 o 3 values 0 07 0 26 higher cia values 76 99 92 86 and appear compositionally more mature reflecting moderate to high intensity source rock weathering among them the barakar mudstones likely have been more intensely weathered than mudstones from any of the other formations the trace element compositions and ratios are consistent with most mudstones being derived from a felsic source with some mudstones being derived from a more mafic source for example la sc 0 805 and 0 114 la th 6 245 5 072 7 418 6 245 and 5 072 and eu eu 1 431 0 868 and 0 805 of some mudstones indicate mafic source bivariate plot of th sc and zr sc indicates considerable enrichment of zircon that suggests recycling from meta sedimentary rocks prominent negative eu anomaly high lree hree and flat hree pattern reflect sediment derivation from predominantly felsic rocks of the old upper continental crust sio 2 al 2 o 3 versus k 2 o na 2 o plot for the mudstones suggests that they formed in a passive margin also total ree content of most of the mudstones is conformable with passive margin tectonic setting and craton interior type of provenance plotting in la th sc th sc zr 10 and la sc versus ti zr diagrams largely indicates continental margin settings for majority of the mudstones but fails to differentiate between active and passive continental margins

modeling the effects of land sea roughness contrast on tropical cyclone winds abstract the fifth generation pennsylvania state university national center for atmospheric research psu ncar mesoscale model mm5 is used to simulate tropical cyclone tc wind distribution near landfall on an f plane at 15 n the effects of the different surface roughness between the land and sea on the wind asymmetry is examined under a strong constraint of a dry atmosphere and time invariant axisymmetric mass fields the winds are found to adjust toward a steady state for prelandfall 50 100 and 150 km offshore landfall and postlandfall 50 100 and 150 km inland tc positions the tc core is asymmetric even when it lies completely offshore or inland the surface 10 m wind asymmetry at the core for pre post landfall position is apparently related to the acceleration deceleration of the flow that has just moved over the sea land as a response to the sudden change of surface friction for prelandfall tc positions the resulted strong surface inflow to the left and front left relative

detrital modes of the pyeongan supergroup late carboniferous early triassic sandstones in the samcheog coalfield korea implications for provenance and tectonic setting abstract medium to coarse sandstones of the carboniferous to early triassic pyeongan supergroup in the samcheog coalfield korea were studied to infer the provenance and tectonic settings of the source areas sandstone detrital modes change upwards stratigraphically sandstone types from the manhang to dosagog formations low to middle in the sequence are quartzarenite and sublitharenite to litharenite whereas sandstones of the gohan and donggo formations high in the sequence are feldspathic litharenite and arkose respectively using various ternary diagrams the provenance of the manhang to gohan formations is suggested to be a recycled orogen setting some gohan formation sandstones plot within the arc related setting field and the donggo formation sandstones plot within both continental block and recycled orogen fields results of quartz grain petrography are consistent with those of detrital modes quartz in sandstones of all units except the donggo formation indicates derivation from low rank metamorphic sources quartz in donggo sandstones was derived from medium to high rank metamorphic and plutonic source rocks considering the sandstone composition and palaeocurrent data the pyeongan supergroup probably was deposited in a molasse foreland basin and was derived from a synbasinal orogenic belt probably the akiyoshi orogen located in southwest japan

modeled variations of precipitation over the greenland ice sheet abstract a parameterization of the synoptic activity at 500 hpa and a simple orographic scheme are used to model the spatial and temporal variations of precipitation over the greenland ice sheet for 1963 88 from analyzed geopotential height fields produced by the national meteorological center nmc model coefficients are fitted to observed accumulation data primarily from the summit area of the ice sheet all major spatial characteristics of the observed accumulation distribution are reproduced apart from the orographic accumulation maximum over the northwestern coastal slopes the modeled time averaged total precipitation amount over greenland is within the range of values determined by other investigators from surface based observations a realistic degree of interannual variability in precipitation is also simulated a downward trend in simulated ice sheet precipitation over the 26 years is found this is supported by a number of lines of evidence it matches the accumulation trends during this peri

boundary layer structure and dynamics in outer hurricane rainbands part i mesoscale rainfall and kinematic structure abstract results of hurricane boundary layer experiments conducted in outer rainbands of hurricanes josephine 1984 and earl 1986 are presented comparisons of precipitation and kinematic structures in these storms and in hurricane floyd 1981 indicate that principal rainbands have common characteristic mesoscale and convective scale features in the boundary layer the two dimensional mesoscale structure suggests that these rainbands are made up of a linear aggregate of cellular reflectivity elements on the inner upshear side of the band and stratiform rain on the outer downshear side the bands are oriented perpendicular to the shear above the boundary layer and cells move downband at about 85 of the density weighted mean wind speed of the 0 2 6 km layer the boundary layer wind field is strongly influenced by the rainband with alongband and crossband wind maxima located on the outer side of the band axis and minima 4 8 km to the inner side maximum crossband convergence and cyclonic shear vor

the dynamics of boundary layer jets within the tropical cyclone core part i linear theory abstract observations of wind profiles within the tropical cyclone boundary layer have until recently been quite rare the recent massive increase in observations due to the operational implementation of the global positioning system dropwindsonde has emphasised that a low level wind speed maximum is a common feature of the tropical cyclone boundary layer here is proposed a mechanism for producing such a maximum whereby strong inward advection of angular momentum generates the supergradient flow the processes that maintain the necessary inflow against the outward acceleration resulting from gradient wind imbalance are identified as being i vertical diffusion ii vertical advection and iii horizontal advection two complementary tools are used to diagnose the properties and dynamics of the jet the first presented here is a linear analytical model of the boundary layer flow in a translating tropical cyclone it is an extension of the classical ekman boundary layer model as well as of earlier w

biological oxygen productivity during the last 60 000 years from triple oxygen isotope measurements during isotope exchange between o2 and co2 in the stratosphere the relative rates of biologic o2 production and stratospheric processing determine the relationship between d 17 o and d 18 oo f o2 in the atmosphere variations of this relationship thus allow us to estimate changes in the rate of mass dependent o2 production by photosynthesis versus the rate of o2 co2 exchange in the stratosphere with about equal fractionations of d 17 o and d 18 o in this study we reconstruct total oxygen productivity for the last glacial the last glacial termination and the early holocene from the triple isotope composition of atmospheric oxygen trapped in ice cores with a box model we estimate that total biogenic productivity was only 76 83 of today for the glacial and was probably lower than today during the glacial interglacial transition and the early holocene depending on how reduced the oxygen flux from the land biosphere was during the glacial the oxygen flux from the glacial ocean biosphere was 88 140 of its present value index terms 3344 meteorology and atmospheric dynamics paleoclimatology 4870 oceanography biological and chemical stable isotopes 1615 global change biogeochemical processes 4805 0315 atmospheric composition and structure biosphere atmosphere interactions keywords gisp2 siple ice cores oxygen isotopes past oxygen productivity stratospheric isotope exchange respiration

geochemistry of sandstones from the upper miocene kudankulam formation southern india implications for provenance weathering and tectonic setting abstract petrographic major trace and rare earth element compositions of sandstones from the upper miocene kudankulam formation southern india have been investigated to determine their provenance tectonic setting and weathering conditions all sandstone samples are highly enriched in quartz q but poor in feldspar f and lithic fragments l the major element concentrations of these sandstones reveal the relative homogeneity of their source geochemically the kudankulam sandstones are classified as arkose subarkose litharenite and sublitharenite the cia values chemical index of alteration mean value 44 5 for these sandstones and the a cn k diagram suggest their low weathering nature similarly their fe2o3 mgo mean 2 7 al2o3 sio2 0 09 k2o na2o 2 2 ratios and tio2 contents 0 3 are consistent with a passive margin setting the eu eu 0 5 la lu cn 21 la sc 5 9 th sc 1 9 la co 5 7 th co 1 8 and cr th 5 3 ratios support a felsic source for these sandstones chondrite normalized ree patterns with lree enrichment flat hree and negative eu anomaly also are attributed to felsic source rock characteristics for kudankulam sandstones total ree concentrations of these sandstones reflect the variations in their grain size fractions the source rocks are probably identified to be proterozoic gneisses charnockites and granites of the kerala khondalite belt which must have been exposed at least since the late miocene finally the unusual ni enrichment in the kudankulam sandstones unaccompanied by a similar enrichment in cr co and v may be related to either the presence of pyrite in the sandstones or more likely the fractionation of garnet from the source rocks during transportation

an electron microprobe study of detrital feldspar microprobe analysis of detrital alkali feldspar and plagioclase is useful in provenance studies detrital grains of alkali feldspar more sodic than 50 weight percent albite molecule are derived almost exclusively from volcanic sources alkali feldspar grains more potassic than 87 percent orthoclase molecule are derived from metamorphic and plutonic rocks for the more sodic varieties of detrital plagioclase it is possible to distinguish on the basis of potassium content between volcanic and non volcanic sources non volcanic albite and volcanic and non volcanic oligoclase and andesine are abundant forms of detrital plagioclase in tertiary sandstones from the southern colorado plateau area labradorite and bytownite are present as detrital grains in some deposits from this region most of the detrital alkali feldspar in these rocks is highly potassic containing more than 90 percent or molecule intermediate alkali feldspar is common in sandstones of volcanic and mixed provenance detrital plagioclase from several sandstones of mixed provenance contains between 0 to 0 7 percent fe and 0 to 0 5 percent sr alkali feldspar from the same samples contains between 0 and 0 5 percent fe and 0 and 1 5 percent ba detrital plagioclase interpreted as volcanic in origin generally contains more fe and sr than non volcanic plagioclase other approaches to the study of detrital feldspar with the microprobe are useful in provenance analysis chemical zoning of plagioclase established previously as a provenance tool can be studied more accurately and in more detail with a microprobe than with a petrographic microscope also sand sized volcanic lithic fragments can be classified as mafic intermediate or silicic in composition by analyzing their feldspar microphenocrysts

a numerical study of the effects of land proximity and changes in sea surface temperature on hurricane tracks a three layer shallow water model with a convection parametrization is used to study the track deflections of slow moving hurricanes on a plane as they approach straight coastlines of different orientations with respect to north or as they cross to a cooler or warmer body of water in the landfall experiments the land surface is level and is characterized by an abrupt increase of the drag coefficient and zero evaporation the tracks of a 72 h integration on a plane are compared with an ocean control experiment it is found that the divergent flow in the boundary layer in regions of offshore winds is responsible for the observed track deflections in this region middle layer air descends into the boundary layer and increases the positive potential vorticity anomaly in the middle layer in the case of land conditions to the west of the vortex the maximum potential vorticity anomaly extends less to the north of the vortex centre and results in a more southerly track than in the ocean control case if land conditions are specified in the north the positive potential vorticityasymmetry maximum extends more to the north west and results in a northward deflection of the track on the other hand land conditions to the north west of the initial vortex centre do not significantly change the location of the asymmetry and therefore the track deflection is small the magnitude of the track deflections as well as the drift speed increases when the roughness of the land is increased it is significant that track deflections commence about 20 h before landfall reaching a value of about 150 km at the time of landfall compared with landfalling hurricanes track deflections of model hurricanes which drift into a region of different sea surface temperature sst are smaller and are a result of intensity changes of the vortex circulation the maximum wind speed at the time of landfall increases if a region of higher sst is located adjacent to the coastline

nitrate in greenland and antarctic ice cores a detailed description of post depositional processes a compilation of nitrate no 3 data from greenland has shown that recent no 3 concentrations reveal a temperature dependence similar to that seen in antarctica except for sites with very low accumulation rates lower temperatures tend to lead to higher no 3 concentrations preserved in the ice accumulation rate which is closely linked to temperature might influence the concentrations preserved in snow as well but its effect cannot be separated from the temperature imprint processes involved in no 3 deposition are discussed and shown to be temperature and or accumulation rate dependent apart from scavenging of nitric acid hno 3 during formation of precipitation uptake of hno 3 onto the ice crystal s surface during and after precipitation seems to contribute further to the no 3 concentrations found in surface snow post depositional loss of no 3 from the top snow layers is caused by release of hno 3 and by photolysis of no 3 it is suggested that photolysis accounts for considerable losses at sites with very low accumulation rates depending on the site characteristic and given that the temperature and accumulation rate dependence is quantified it should be possible to infer changes in atmospheric hno 3 concentrations

air mass trajectories to summit greenland a 44 year climatology and some episodic events the seasonal variation in atmospheric transport patterns to summit greenland is examined using a 44 year record of daily 10 day isobaric back trajectories at the 500 hpa level over 24 000 modeled trajectories are aggregated into distinct patterns using cluster analysis ten day trajectories reaching summit are longest during winter with 67 extending upwind westward as far back as asia or europe trajectories are shortest during summer with 46 having 10 day origins over north america during all seasons a small percentage 3 7 of trajectories originate in west asia europe and follow a meridional path over the arctic ocean before approaching summit from the northwest trajectories at the 700 hpa level tend to be shorter than at 500 hpa with many of the 700 hpa trajectories from north america tracking over the north atlantic and approaching summit from the south the long range transport climatology for summit is similar to a year round climatology prepared for dye 3 located 900 km to the south davidson et al 1993b an analysis of several aerosol species measured at summit during summer 1994 reveals examples of the usefulness and also the limitations of using long range air trajectories to interpret chemical data

the effect of a river delta and coastal roughness variation on a landfalling tropical cyclone 1 numerical simulations on an f plane are performed using the weather research forecasting wrf model to study how the presence of a river delta and variations in coastal roughness might affect the motion and the structure of a tropical cyclone tc near landfall in each delta experiment an idealized triangular shaped delta pointing to the west with length 150 km and a river mouth size of 100 km is inserted along the coastline the surface roughness and the moisture availability of the delta vary among the delta experiments and the surface properties are uniform in the rest of the land area in another set of experiments where there is no delta the roughness of a whole land area has different values along the north south oriented coast results suggest that the tc in the control experiment ctrl with no delta or roughness variation along the coast is weaker than all the delta cases during a certain period before landfall moisture supply from the delta appears to have an effect on sustaining the approaching tc despite the relatively small scale of the delta tracks of the tcs in the roughness variation experiments deviate from that of the ctrl the roughness variation along the coast apparently affects the convergence patterns higher roughness induces stronger convergence and hence increases the vertical advection term in the potential vorticity tendency distribution over the rougher area hence a tc tends to move toward a region with higher roughness

new precipitation and accumulation maps for greenland annual total precipitation and the annual accumulation on the greenland ice sheet are evaluated and presented in two maps the maps are based on accumulation measurements of 25 1 pits and cores obtained from the upper accumulation zone and precipitation measurements made at 35 meteorological stations in the coastal region to construct the accumulation map the annual precipitation was split into solid and liquid precipitation components annual total precipitation exceeding 2500 mm w e occurs on the southeastern tip of greenland while the minimum precipitation is estimated to occur on the northeastern slope of the ice sheet the mean annual precipitation for all of greenland is 340 mm w e the largest annual accumulation of about 1500 mm w e is found on the glaciers in the southeastern corner of greenland while the smallest accumulation is found on the northeastern slope of the ice sheet west of danmarkshavn the mean accumulation on the greenland ice sheet is estimated at 310 mm w e the regional difference in accumulation is examined with respect to the 850 hpa m bar level circulation the present surface topography is found to play an important role in determining regional accumulation on the ice sheet

critical evaluation of six tectonic setting discrimination diagrams using geochemical data of neogene sediments from known tectonic settings abstract an attempt is made to evaluate 6 tectonic setting discrimination diagrams 1 discriminant function and 5 bivariate diagrams frequently used by many researchers for this purpose an extensive database was established for major element geochemistry derived from miocene to recent sand and sandstone medium to fine grained samples collected from a variety of tectonic settings including 1 passive margin pm setting 2 active continental margin acm setting and 3 oceanic island arc oia setting our results suggest that the discrimination fields proposed to infer tectonic settings for six commonly used discrimination diagrams do not work properly for the analyzed miocene to recent sediments the success for these diagrams varies from 0 to about 62 we therefore recommend that these diagrams be used with prudence

paleomagnetic data support early permian age for the abor volcanics in the lower siang valley ne india significance for gondwana related break up models confusion exists as to the age of the abor volcanics of ne india some consider the unit to have been emplaced in the early permian others the early eocene a difference of 230 million years the divergence in opinion is significant because fundamentally different models explaining the geotectonic evolution of india depend on the age designation of the unit paleomagnetic data reported here from several exposures in the type locality of the formation in the lower siang valley indicate that steep dipping primary magnetizations mean 72 7 6 2 equating to a paleo latitude of 58 1 are recorded in the formation these are only consistent with the unit being of permian age possibly artinskian based on a magnetostratigraphic argument plate tectonic models for this time consistently show the ne corner of the sub continent 50 s in the early eocene it was just north of the equator which would have resulted in the unit recording shallow directions the mean declination is counter clockwise rotated by 94 around half of which can be related to the motion of the indian block the remainder is likely due local himalayan age thrusting in the eastern syntaxis several workers have correlated the abor volcanics with broadly coeval mafic volcanic suites in oman ne pakistan nw india and southern tibet nepal which developed in response to the cimmerian block peeling off eastern gondwana in the early middle permian but we believe there are problems with this model instead we suggest that the abor basalts relate to india antarctica india australia extension that was happening at about the same time such an explanation best accommodates the relevant stratigraphical and structural data present day position within the himalayan thrust stack as well as the plate tectonic model for permian eastern gondwana

oxygen 18 16 variability in greenland snow and ice with 10 3 to 105 year time resolution the 3 km long greenland ice sheet project 2 gisp2 ice core presents a 100 000 year detailed oxygen isotope profile covering almost a full glacial interglacial cycle measuranents of isotopic fluctuations in snow frost and atmospheric water vapor samples collected during summer field seasons up to 20 0 are compatible with the large and abrupt 80 160 changes observed in accumulated tim snow pit 15 80 profiles from the gisp2 summit area however show rapid smoothing of the 180 160 signal near the surface beyond about 2 m depth the smoothedi5180 signal is fairly well preserved and can be interpreted in terms of average local weather conditions and climate the longer climate fluctuations also have regional and often global significance in the older part of the record corresponding to marine isotope stages mis 5a to 5d the effect of orbital climate forcing via the 19 and 23 kyr precession cycles and the 41 kyr obliquity cycle is obvious from the end ofmis 5a at about 75 000 years b p till the end of the glacial at the younger dryas preboreal transition at 11 650 years b p the o180 160 record shows frequent rapid switches between intermediate interstadial and low stadial values fourier spectra of the oscillations that are superimposed on the orbitally induced changes contain a strong periodicity at 1 5 kyr a broad peak at 4 0 kyr and additional shorter periods detailed comparison of the gisp2 180 160 record with the vostok antarctica 15d record pacific ocean foraminiferal 180 160 grande pile france tree pollen and insolation indicates that a counterpart to many of the rapid 180 160 fluctuations of gisp2 can be found in the other records and that the gisp2 isotopic changes clearly are the local expression of climate changes of worldwide extent correlation of events on the independent gisp2 and specmap time scales for the interval 10 000 50 000 years b p shows excellent chronometric agreement except possibly for the event labeled 3 1 the glacial to interglacial transition evidently started simultaneously in the arctic and the antarctic but its development and its expression in greenland isotopes was later suppressed by the influence of meltwater especially from the barents sea ice sheet on deep water formation and ocean circulation meltwaters from different ice sheets bordering the north atlantic also influenced ocean circulation during the bolling allerod interstadial complex and the younger dryas and led to a distinct development of european climate and greenland 180 160 values the holocene interval with long term stable mean isotopic values contains several fluauations with periods from years to millennia dominant is a 6 3 year oscillation with amplitude up to 3 to 4 0 periodicities of 11 and 210 years also found in the solar modulated records of the cosmogenic isotopes 1obe and 14c suggest solar processes as the cause of these cycles depression of180 160 values cooling by volcanic eruptions is observed in stacked gisp215 80 records but the effect is small and not likely to trigger major climate changes

borehole versus isotope temperatures on greenland seasonality does matter new simulation results obtained with the hamburg atmosphere general circulation model echam 4 under maximum glacial boundary lgm conditions confirm the paleotemperatures on greenland determined by borehole thermometry the disagreement between 18o isotope based temperatures and the borehole temperatures of the lgm is not only reproduced by the model but the simulation results provide a plausible explanation paleotemperatures inferred from 18o measurements in ice cores are biased by a substantially increased seasonality of precipitation over greenland during the lgm during the glacial winter a much more zonal circulation prevents the effective transport of moisture to the greenland ice sheet and therefore reduces the contribution of isotopically strongly depleted winter snow to the annual mean isotope signal

exceptions to the relationship between plate tectonics and sandstone composition abstract routine use of qfl qplsmlvm and lmlslv plate tectonic provenance diagrams has led to the recognition of error populations for these sandstones the interpretation of tectonic setting based on data exclusive of petrography does not coincide with the interpretation of tectonic setting based on their location on compositional diagrams the anomalous sandstones can be separated into at least four categories i sandstones deposited during the transition between tectonic regimes may be derived in part from relict source rocks ii the relative enrichment of sandstones in detrital quartz by weathering and or depositional reworking may lead to an inaccurate interpretation of tectonic setting from compositional data iii sandstones deposited in tectonic settings as yet unrepresented on he provenance diagrams may plot between the provenance fields or overlap existing fields iv the role of detrital carbonate rock fragments directly affects the location of data points on provenance diagrams and is an unresolved problem the first two categories represent permanent problems in the use of sandstone composition as an indicator of plate tectonic setting whereas the last two may only be temporary problems that can be solved by more data and a consensus on determining detrital modes recognition of anomalous sandstones in the rock record will reduce the probability of erroneous interpretations of tectonic setting and enhance the use of sandstone petrology as an indicator of plate tectonic setting

isotopic view on nitrate loss in antarctic surface snow 1 massive post depositional processes alter the nitrate concentration in polar firn where the annual snow accumulation is low this hinders a direct atmospheric interpretation of the ice core nitrate record fractionation of nitrate isotopes during post depositional nitrate loss may allow estimating the amount of nitrate loss in the past we measured 15 n of nitrate in two antarctic surface cores from the dome c area in concert with the known concentration decrease with depth we observe an increase in the isotopic signature assuming a rayleigh type process we find an isotope effect of e 54 o we measured the fractionation factor for photolysis in the laboratory and obtained e 11 7 1 4 o as the observed fractionation factor in the fim is much lower this rules out that photolysis in the surface snow is the main process leading to the dramatic nitrate loss in the top centimeters of the firn citation blunier t g l floch h w jacobi and e quansah 2005 isotopic view on nitrate loss in antarctic surface snow

textures and geochemistry of authigenic albite from miocene sandstones louisiana gulf coast feldspars in louisiana miocene sandstones at depths of 2 400 to 6 000 m 80 to 150 degrees c show progresssive reaction with increasing burial plagioclase undergoes both dissolution and replacement by albite whereas k feldspar undergoes only dissolution reactions do not reach completion by 6 000 m 150 degrees c where a small amount of oligoclase and k feldspar remain within an assemblage of nearly pure authigenic albite dissolution of plagioclase gradually becomes volumetrically important near 3 600 m 100 degrees c and for the most part ends by 5 000 m 130 degrees c albite replacement of plagioclase also occurs primarily between 3 600 and 5 000 m 100 to 130 degrees c but continues to the limit of sample control at 6 000 m 150 degrees c k feldspar dissolution is negligible until 4 800 to 5 600 m 125 to 140 degrees c below 5 600 m k feldspar is nearly absent in the rocks discontinuous zones of blocky to tabular extinction characterize grains of partially albitized plagioclase backscattered electron images of these grains coupled with electron microprobe analyses indicate that these zones represent domains of unreacted calcic plagioclase an sub 10 30 interspersed with domains of nearly pure authigenic albite an sub 0 2 sem images show that some albite domains form from precipitation of small albite overgrowths on nucleation sites within secondary intragranular megascopic pores in thin section the overgrowths are optically clear other highly vacuolized albite domains may develop from direct replacement of calcic domains by dissolution reprecipitation in submicroscopic pores without the formation of megascopic pores here pore fluid may have been trapped between large numbers of subcrystals that grew together with imperfect boundaries operating on both megascopic and submicroscopic scales albite replacement of plagioclase grains can be completed

quartz grain types in holocene deposits from the spanish central system some problems in provenance analysis holocene sands of the spanish central system were exclusively derived from plutonic middle upper grade and low grade metamorphic rocks modal composition of studied sands is mostly controlled by grain size and source area lithology thus sands derived from slates and schists plot near the qr edge on the qfr diagram for ali grain size fractions sands derived from granitic or gneissic rocks have a wide dispersion on the qfr diagram from the r pole to the qf edge depending on sand grain size percentages of quartz types in granitic derived sands are qnu42 qu40 qp2 314 and qp 34 sands of gneissic origin have qnu 51 qu 1 5 qp2 323 and qp 311 sands derived from slates and schists have qnu 20 qu 1 2 qp2 35 and qp 363 quartz types easily discrimina te sands of low grade origin but distinction of sands derived from plutonic rocks from those derived from middle upper grade metamorphic rocks is difficult because of the highly variable qu content of plutonic rocks related to strain history and crystallization conditions thus quartz types mus be used with caution in source discrimination if plutonic rocks are present in the source area

the geochemistry of the sedimentary rocks from the huadi no 1 well in the wufeng longmaxi formations upper ordovician lower silurian south china with implications for paleoweathering provenance tectonic setting and paleoclimate abstract the late ordovician early silurian transition was a critical interval in earth s history marked by mass extinction the gondwana glaciation and volcanic events here we present mineralogical and geochemical characteristics across the ordovician silurian boundary wufeng guanyinqiao and longmaxi formations from the huadi no 1 well in the sichuan basin in order to explore the paleoweathering provenance tectonic setting and paleoclimatic conditions of the source area thin sections xrd x ray diffraction data and major element results reveal that the rocks were abundant in clay minerals quartz minor feldspar pyrite and carbonate minerals the samples have similar chondrite normalized ree patterns to those of paas which are characterized by slight lree enrichments and accompanied by flat hree trends with weakly negative eu anomalies paleoweathering indices cia and pia suggest that the sediments experienced weak to moderate chemical weathering in the source area cia values in the lower wufeng formation range from 67 11 to 72 17 indicating a warm and humid climate the cia values in the upper wufeng formation decrease from 70 35 to 66 15 and the cia values in the guanyinqiao and lower longmaxi formation are persistently low 56 64 62 87 suggesting a cold and dry climate which is consistent with the widespread presence of glaciation in the hirnantian period further upward in the upper longmaxi formation the cia returns to a high value 65 59 which may reflect that the climate started getting warm and glaciation had finished fluctuations in cia values reflect that the climate shifted from warm to cold and then to warm again during the end ordovician early silurian time period the a cn k triangular diagram and sio2 al2o3 tio2 tio2 zr and la th hf bivariate diagrams indicate that the provenance of the rocks from the three formations was primarily felsic igneous rocks discriminant function diagrams and la th sc th co zr 10 and th sc zr 10 triangular diagrams show that the clastic sediments of the wufeng longmaxi formations were derived most likely from an active continental margin finally across the late ordovician early silurian tectonic activity and the end of the ordovician glaciation dominantly controlled the deposition of black shales and siltstones in the wufeng longmaxi formations of south china

biomass burning recorded in the gisp2 ice core a record from eastern canada combustion byproducts from biomass burning are preserved in annually stratified layers in the greenland ice sheet electrical conductivity ecm and ammonium records from the gisp2 ice core in central greenland have been used to develop a 6000 year record of biomass burning although there is some uncer tainty regarding the source area for the combustion byproducts it is likely that the majority of the material originates in eastern canada time periods of high biomass burning activity occurred in 0 150 bp 350 750 bp and 5000 to 6000 bp the period 1150 3250 bp is characterized by moderately elevated levels of biomass burning activity these periods are associated with drier conditions the 5000 to 6000 bp period of high biomass burning activity may also be related to forest successional sequences following the removal of the laurentide ice sheet this paper explains how ice cores can be used to develop records of biomass burning and offers suggestions for future studies

a multiscale numerical study of hurricane andrew 1992 part vi small scale inner core structures and wind streaks abstract the objectives of part vi of this series of papers are to a simulate the finescale features of hurricane andrew 1992 using a cloud resolving grid length of 2 km b diagnose the formation of small scale wind streaks and c perform sensitivity experiments of varying surface fluxes on changes in storm inner core structures and intensity as compared to observations and a previous 6 km model run the results show that a higher resolution explicit simulation could produce significant improvements in the structures and evolution of the inner core eyewall and spiral rainbands and in the organization of convection the eyewall becomes much more compact and symmetric with its width decreased by half and the radius of maximum wind is reduced by 10 to 20 km a zone of deep and intense potential vorticity pv is formed at the edge of the eye a ring of maximum pv is collocated in regions of maximum upward motion in the eyewall and interacts strongly with the eyewall convection the convective cor

a simulation of hurricane landfall with a numerical model featuring latent heating by the resolvable scales abstract a nested grid hurricane model is used to transport a strong vortex over a straight coastline at 4 m s 1 the track at landfall of the vortex is 20 km to the left of a control simulation without land just before landfall a 15 km amplitude trochoidal oscillation of the vortex track occurs this amplitude is nearly double that of similar oscillations of the control simulation about 10 h before landfall a spiral rainband nearly surrounds the vortex at radii of 135 km this rainband has a weak secondary maximum in the tangential wind and is the model analog of the secondary eyewalls observed by willoughby et al in several hurricanes the rainfall in spiral rainbands diminishes during the 7 h before landfall however rainfall in the inner core of the vortex is greater during landfall than in the control simulation the greatest rainfall accumulation is to the right of the vortex however compared with the control simulation rainfall is greater to the left and less to the right of the vorte

changes in the low level kinematic and thermodynamic structure of hurricane alicia 1983 at landfall abstract aircraft land station and buoy data were composited with respect to the center of hurricane alicia 1983 for three 8 h periods corresponding to prelandfall in the open gulf of mexico landfall in the galveston area and postlandfall in the vicinity of houston comparison of the wind analyses before during and after landfall emphasizes the land sea frictional asymmetry at landfall in addition other asymmetries in the surface wind field and differences between the flight level and the surface wind fields are revealed the asymmetric structure of the surface wind field may be interpreted as having resulted from the combined effects of land sea roughness differences background environmental flow and storm translation the land sea frictional difference acted to oppose the mean vortex flow over land and reinforce it over water the southwest background environmental flow acted nearly parallel to the coastline producing surface inflow on the left side and outflow on the right side while the

petrology of holocene sand peninsular ranges california and baja norte mexico implications for provenance discrimination models abstract the peninsular ranges of southern california and baja california norte mexico represent an uplifted and variably dissected mesozoic magmatic arc they are composed mostly of cretaceous plutonic rocks and mesozoic greenschist to amphibolite facies metasedimentary and metavolcanic rocks in order to evaluate the reliability of the diamond shaped qnuquqp provenance discrimination diagram developed by basu et al 1975 and the qfl provenance discrimination diagram developed by dickinson et al 1983 we collected 62 samples of holocene sand from four drainage basins along the west side of the peninsular ranges the qfl composition of each specimen was determined by the gazzi dickinson point counting method the relative percentages of med um grained fragments of qnu qu and qp were determined by counting 100 grains in each specimen the results of our study indicate that holocene sands derived from the peninsular ranges have the following average petrological characteristics 1 sands derived mostly or exclusively from plutonic rocks are composed of 16 46 percent q 54 83 percent f and 0 2 0 5 percent l the medium grained quartz population produced by erosion of mostly or exclusively plutonic rocks consists of 61 77 percent qnu 4 17 percent qu and 13 27 percent qp 2 sands originating from the erosion of metasedimentary rocks are composed of 63 percent q 13 percent f and 24 percent l the medium grained quartz population derived from a metasedimentary source is made up of 25 percent qnu 9 percent qu and 66 percent qp 3 sands produced by the erosion of mostly or exclusively metavolcanic rocks are composed of 19 percent q 39 44 percent f and 38 43 percent l the medium grained quartz population originating from a mostly or exclusively metavolcanic source consists of 48 74 percent qnu 6 percent qu and 20 46 percent qp petrological data obtained during this study indicate that the qfl provenance discrimination model generally yields a correct interpretation of tectonic setting when applied to holocene sand from the peninsular ranges data however also show that local source areas produce sands that when interpreted on the basis of their position on the qfl provenance discrimination diagram yield an erroneous interpretation of tectonic setting data obtained from counting varieties of medium grained quartz show that detrital quartz populations produced by plutonic rocks are discriminated from those derived from metasedimentary rocks by the qnuquqp provenance discrimination diagram in contrast quartz populations originating from a mostly or exclusively metavolcanic source are difficult to interpret on the qnuquqp diagram therefore we recommend that the qfl provenance discrimination model be used with caution when sand or sandstone samples are from a limited geographic area and that the qnuquqp provenance discrimination diagram be used with prudence when metavolcanics are suspected in the provenance

climatic control on the composition of carboniferous permian gondwana sediments khalaspir basin bangladesh abstract late paleozoic or permo carboniferous gondwana successions world wide are marked by widespread and lengthy glaciation 67 ma and multiple transitions from icehouse to greenhouse state mineralogical and compositional changes in sandstones and mudstones of the gondwana succession in drill hole gdh 45 from the khalaspir basin of bangladesh are interpreted in a climatic framework using the proxies of the mineralogical index of alteration mia and the chemical index of alteration cia low mia

large arctic temperature change at the wisconsin holocene glacial transition analysis of borehole temperature and greenland ice sheet project ii ice core isotopic composition reveals that the warming from average glacial conditions to the holocene in central greenland was large approximately 15 c this is at least three times the coincident temperature change in the tropics and mid latitudes the coldest periods of the last glacial were probably 21 c colder than at present over the greenland ice sheet

sandstone provenance point loma formation san diego california evidence for uplift of the peninsular ranges during the laramide orogeny abstract previous petrologic study of sandstones from the upper cretaceous point loma formation utilized methodology advocated by folk 1974 in order to improve comparability with other provenance studies of cretaceous sandstones in california new modal data for sandstones from the point loma formation were determined using the gazzi dickinson point counting method in addition varieties of quartz were studied following methods described by basu et al 1975 the new petrologic data indicate that sandstones in the point loma formation are composed of detritus derived primarily from the exposed plutonic metamorphic roots of a segment of the magmatic arc of the peninsular ranges this conclusion is significant because it implies that parts of the magmatic arc of the peninsular ranges were u lifted deeply dissected and nearly stripped clean of their volcanic cover by late cretaceous time the late cretaceous uplift of parts of the magmatic arc of the peninsular ranges occurred at the same time as the uplift of the magmatic arc of the sierra nevada and both uplift events may have been associated with the early phase of an abnormally low angle of subduction during the laramide orogeny

asymmetric distribution of convection associated with tropical cyclones making landfall along the south china coast this study examines the convection distribution associated with 18 tcs that made landfall along the south china coast during 1995 and 2005 cloud top temperatures from high resolution satellite imageries of the geosynchronous meteorological satellite 5 are used as proxy of strong convection it is found that convection tends to be enhanced on the western side of the tc as it makes landfall in 10 of the cases in agreement with the conclusion of some previous studies four cases have stronger convection on the eastern side this deviation from the general rule appears to be related to the tcs being more slow moving or their interaction of the tc with another land surface prior to its making landfall along the south china coast for the remaining cases in which no significant asymmetries in convection can be identified the vertical wind shear appears to enhance convection on the east side

composition of modern stream sand in a humid climate derived from a low grade metamorphic and sedimentary foreland fore thrust belt of north georgia abstract conditions of tectonics and drainage in north central georgia provide an excellent natural laboratory to study the composition of stream sand derived from a low grade metamorphic and sedimentary foreland fold thurst belt under humid climatic conditions the streams head in a high relief phyllite schist and metasandstone terrain and flow westward across a bounding fault into lower relief paleozoic shales cherty carbonates and quartz arenites the relative abundance of the source rock types in the drainage basin of each sample site was determined and a source rock ratio was calculated as the ratio of the area underlain by metamorphic rock to the total area of the drainage basin low grade metamorphic source rocks supply subequal amounts of monocrystalline quartz polycrystalline quartz and foliated quartz mica rock fragments to stream sediment whereas sand from the sedimentary source terrain consists primarily of monocrystalline quartz a surprisingly large number of pelitic rock fragments and chert mixing of sediment from both source rock types is recognizable on the quartz provenance diagram of young 1976 by a high instability index unstable polycrystalline quartz total polycrystalline quartz and a low polycrystallinity index polycrystalline total quartz this diagram is especially sensitive to the presence of sandstones as source rocks which further decreases the polycrystallinity index the ratio of metamorphic rock fragments to total rock frag ents also is directly related to the source rock ratio modern sand derived from the foreland fold thurst belt of north georgia can be distinguished from neogene subduction complex derived sand and collision orogen derived sand on qfl lmlslv and qplsmlvm provenance diagrams by containing less total feldspar more total quartz and no volcanic rock fragments the concepts developed from the recent sand are applied to the mississippian parkwood formation alabama and the cretaceous muddy formation montana the results suggest that both sandstone units were derived from foreland fold thrust belts but that the parkwood source area contained a greater proportion of low grade metamorphic source rocks than the source area of the muddy

antarctic aerosol and snowfall chemistry implications for deep antarctic ice core chemistry in this paper we first summarise major findings of recent atmospheric studies of nitrogen and sulphur species present in the boundary layer of coastal antarctic regions we then discuss the implications of such atmospheric data for the interpretation of nitrate ammonium methanesulphonate and sulphate records in deep ice cores extracted from central antarctica in terms of past atmospheric chemistry changes

glacial interglacial changes in the isotopes of nitrate from the greenland ice sheet project 2 gisp2 ice core received 3 march 2005 revised 23 september 2005 accepted 26 october 2005 published 24 december 2005 1 the 15 n 14 n and 18 o 16 o ratios of nitrate in the greenland ice sheet project 2 gisp2 summit greenland ice core are much higher in ice from the last glacial period than in the pre industrial holocene despite the lack of a significant glacial interglacial change in nitrate concentration while both the 15 n 14 n and 18 o 16 o records are anticorrelated with snow accumulation rate neither is satisfactorily explained by accumulation changes or post depositional processes the similarity in the glacial interglacial change in 15 n 14 n from several different greenland ice cores and the large amplitude of this change relative to observed seasonal variation raise the possibility that the isotopes of nitrate in ice cores indicate a large scale glacial interglacial change in the isotopic composition of atmospheric nox the glacial interglacial change in 18 o 16 oi s best explained by a greater contribution of hno3 production from hydrolysis of n2o5 which has implications for reconstruction of past atmospheric oxidant levels although isotope effects associated with nox photochemistry and nitrate scavenging have not been fully characterized the 15 n 14 n data may indicate glacial interglacial changes in the relative contributions from different natural sources of nox on a hemispheric or global scale

the ice age methane budget 1 accounting for the natural 40 reduction in methane during the last glacial maximum lgm represents one of the most challenging problems posed by polar ice core studies inverse modelling constrained by observations suggest it is driven by a decline in wetland sources but this is not supported by forward modelling using a comprehensive earth system model we show that closure of the methane budget requires reduced emissions and an amplified sink caused by reduction in emissions of volatile organic compounds vocs from lgm forests our study emphasizes a key role for the terrestrial biosphere in the methane budget during the quaternary

seasonal precipitation timing and ice core records this is a commentary on global circulation model experiments of moisture source changes in greenland urging caution in how they are applied because they have important implications for paleoclimate reconstruction from ice cores the work comes from preliminary find is of a ice core gisp2 of the authors the authors conclude that at present anomalies in greenland ice core records should not be interpreted solely in terms of source region variations the combined use of oxygen 18 d and ionic species in the new summit greenland cores should make it possible to answer empirically some of the questions raised by the gcm experiments as to the interpretation of oxygen 18 records in terms of temperature 4 refs 1 fig

petrography and major element geochemistry of the permo triassic sandstones central india implications for provenance in an intracratonic pull apart basin abstract detrital mode composition of feldspars and heavy minerals and major element chemistry of sandstones from the permo triassic succession in the intracratonic satpura gondwana basin central india have been used to investigate provenance the talchir formation the lowermost unit of the succession comprises glacio marine and glacio fluvial deposits the rest of the succession base to top comprising the barakar motur bijori pachmarhi and denwa formations largely represent variety of fluvial depositional systems with minor fluvio deltaic and fluvio lacustrine sedimentation under a variety of climatic conditions including cold warm arid sub humid and semi arid qfl compositions of the sandstones indicate a predominantly continental block provenance and stable cratonic to fault bounded basement uplift tectonic setting compositional maturity of sandstones gradually increases upwards from the early permian talchir to the middle triassic denwa but is punctuated by a sharp peak of increased maturity in the barakar sandstones this temporal change in maturity was primarily controlled by temporal variation in fault induced basement uplift in the craton and was also influenced by climatic factors plots of different quartz types suggest plutonic source rocks for the talchir sandstones and medium to high rank metamorphic plus plutonic source rocks for the younger sandstones composition of alkali feldspars in the permo triassic sandstones and in different precambrian rocks suggests sediment derivation from felsic igneous and metasedimentary rocks compositions of plagioclase in the talchir and bijori sandstones are comparable with those of granite acid volcanic and metasedimentary rocks of the precambrian basement suggesting the latter as possible source rare presence of high k plagioclase in the talchir sandstones however indicates minor contribution from volcanic source rock exclusively plagioclase bearing metasedimentary rock tonalite gneiss and mafic rocks are the probable sources of plagioclase in the upper denwa sandstones quartz rich nature of the sandstones predominance of k feldspar over plagioclase and albite rich character of plagioclase in the sandstones is consistent with deposition in an intracratonic pull apart basin like the satpura gondwana basin composition of garnet and its comparison with that from the precambrian basement rocks suggests mica schist and amphibolite as possible sources predominance of dravite variety of tourmaline in the permian sandstones suggests sediment supply from metasedimentary rocks presence of both dravite and schorl variety of tourmaline in subequal amount in the triassic sandstones indicates sediment derivation from granitic and metasedimentary rocks however schorl bearing rocks are absent in the basement complex of the study area a cn k plot suggests granites acid volcanic rock and meta sediments of the basement as possible sources of the talchir sandstones and metasedimentary rocks for the barakar to pachmarhi sandstones the denwa sandstones were possibly derived from k feldspar free plagioclase bearing metasediments mafic rocks and tonalite gneiss chemical index of alteration cia values suggest low intensity source rock weathering for the talchir sandstones and higher intensity source rock weathering for the others various bivariate plots of major oxides composition of the sandstones suggest passive to active continental margin setting and even arc tectonic setting for a few samples

surface cold pools in the outer rainbands of tropical storm hanna 2008 near landfall surface mesonet observations were used to document the structure of prominent cold pools associated with twoconvectiveouterrainbandsoftropicalstormhannaon5september2008 thedevelopingrainbandswere located 400 kmnorth ofthestormcenterastheycrossedthecarolinacoastlineandpassedover themesonet the combination of moderate cape moderate low level cross band vertical shear and dry midlevel air provided an environment supportive of surface cold pool formation and long lived quasi linear convection both rainbands exhibited multiple outward tilting convective cells and discrete line segments centered within a narrow zone of nearly continuous stratiform precipitation the mesonet observations provided a unique along and cross band perspective of discrete cold pools situated beneath andbehind the convection portions of each rainband prominentcold pools extended 40 80 km behind the rainband s leading edge and exhibited maximum potential temperature mixing ratio and equivalentpotentialtemperaturedeficitsof2 4 k 1 2 g kg 21 and4 10 k respectively inthecross banddirection convergence of storm relative inflow along the cold pool leading edge was coincident with a modest high pressure anomaly while inflow divergence prevailed through the cold pool and rainfall maxima several cold pools expanded along band while being advected downband by the prevailing cyclonic flow cold pool wakes were observed more than 50 km behind the rainband leading edge and up to 20 km downband from intense convection variations in cold pool intensitywerenotwell correlated with convectiveintensity rainfallrate or the degree of midlevel dryness implications of prominent cold pools on tropical cyclone convection size and intensity are discussed

diagenetic albitization of detrital k feldspar in jurassic lower cretaceous and tertiary clastic reservoir rocks from offshore norway i textures and origin abstract the origin of albitized grains in sandstones has been the topic of considerable discussion in recent years some workers believe that the albitization of feldspar can occur in situ during burial diagenesis but others argue that albitization is a feature inherited from source clastic grains our petrological and chemical studies of subsurface samples of the jurassic lower cretaceous and tertiary reservoir sandstones from offshore norway show that detrital grains of potassium feldspar have been albitized during burial diagenesis criteria suggesting that the albitization has occurred during burial diagenesis include 1 euhedral habit of albite crystals with sharp edges and comers and markedly smooth crystal faces 2 generally untwinned albitized grains mostly riddled with minute br wnish inclusions 3 lack of cathodoluminescence in albite 4 homogeneous and pure albite composition 99 ab 5 absence of albitized grains in carbonate cemented zones and 6 increase in the percentage and degree partial to complete of albitized k feldspar with depth under sem albitized grains display two types of fabrics type i albitized grains are composed of numerous tiny albite crystals 1 30 m growing along cleavage planes in parent grains and they have abundant dissolution porosity while type ii albitized grains show blocky albite crystals 5 80 m forming pseudomorphs of detrital k feldspar and they lack any dissolution porosity type i albitized grains are found commonly at shallower depths between 2 2 and 3 km and temperatures varying from 65 to 90 c whereas type ii albitized grains dominate at greater depths 3 5 km and at temperatures 90 c albitization proceeds by a dissolution precipitation mechanism at shallower depth dissolution of the parent k feldspar is more rapid than the precipitation of albite and rates of albite precipitation increase with depth favoring pseudomorphic replacement of k feldspars other factors that influence albitization processes are ana ak permeability reduction and surface dissolution kinetics of the parent grain

a high resolution prediction study of two typhoons at landfall abstract the landfall on the china coast of two typhoons has been studied using both observational diagnostics and a 30 km 19 level prediction system the typhoons vary in size and in the amount of rainfall they produced after landfall use is made of a synthetic typhoon insertion scheme and the relatively dense observational network around china to provide objective analyses the authors illustrate that in the forecast model as the typhoon s outer circulation impinges on the china coast an outer cloud band develops offshore parallel to the coast extending cyclonically north and east during this time the inner circulation weakens as the outer cloud band strengthens the center of the circulation approaches it from the east and there is a short term intensification of both the inner region vertical motion and vorticity following landfall rapid dissipation of the core occurs using detailed diagnostics from the model integration the changing thermal structure of the forecast vortex is illustrated

provenance of palaeozoic sandstones from the carnic alps austria petrographic and geochemical indicators an integrated approach of petrographic analysis whole rock geochemistry and microprobe analysis has been applied to obtain information on the geodynamic development and the provenance for ordovician to permian siliciclastic successions exposed within the carnic alps austria sandstone detrital mode and geochemical results refine previous geodynamic interpretations late ordovician samples indicate a stable craton and recycled orogenic and possible extensional setting the early carboniferous is interpreted to represent a compressional environment followed by a late carboniferous molasse type foreland basin and a permian extensional geodynamic setting contrasting geochemical patterns of post variscan and permian sequences suggest a rift setting electron microprobe data of detrital white mica also indicate changes in the provenance compositional data reflect a shift from low to medium grade metamorphic ordovician to high grade metamorphic carboniferous to low to medium grade metamorphic and plutonic source rocks permian additionally our data show that various chemical discrimination diagrams do not include all possible ranges of sandstones and that high contents of detrital mica and ultra stable heavy minerals may cause misclassification consequently we propose the use of multi method approach for provenance studies including the control of geochemical data by modal analysis and heavy mineral investigations

temperature accumulation and ice sheet elevation in central greenland through the last deglacial transition we present a combined heat and ice flow model constrained by measurements of temperature in the greenland ice sheet project 2 gisp2 borehole and by the gisp2 18o record and depth age scale which determines a history of temperature accumulation rate and ice sheet elevation for the past 50 000 years in central greenland important results are that the temperature increase from average glacial to holocene conditions was large approximately 15 c with a 20 c warming from late glacial to holocene that the average accumulation rate during the last glacial maximum between 15 and 30 kyr b p was 5 5 to 7 cm yr 1 approximately 25 of the modern accumulation rate that long term 500 1000 years averaged accumulation rate and temperature have been inversely correlated during the most recent 7 millennia of the holocene and that the greenland ice sheet probably thickened during the deglacial transition the inverse correlation of accumulation rate and temperature in the mid and late holocene suggests that the greenland ice sheet is more prone to volume reduction in a warmed climate than previously thought and demonstrates that accumulation rate is not a reliable proxy for temperature the elevation history of the ice sheet is poorly constrained by the model and independent evidence is needed we also present a simple estimate of the response time for thinning of the interior region of an ice sheet due to retreat of its margins this was approximately 1900 years for central greenland during deglaciation

changes in atmospheric circulation and ocean ice cover over the north atlantic during the last 41 000 years high resolution continuous multivariate chemical records from a central greenland ice core provide a sensitive measure of climate change and chemical composition of the atmosphere over the last 41 000 years these chemical series reveal a record of change in the relative size and intensity of the circulation system that transported air masses to greenland defined here as the polar circulation index pci and in the extent of ocean ice cover massive iceberg discharge events previously defined from the marine record are correlated with notable expansions of ocean ice cover and increases in pci during stadials without discharge events ocean ice cover appears to reach some common maximum level the massive aerosol loadings and dramatic variations in ocean ice cover documented in ice cores should be included in climate modeling

combined tide and wave influence on sedimentation of lower gondwana coal measures of central india barakar formation permian satpura basin the coal bearing barakar succession of the satpura basin is typical of the gondwanan coal basins of peninsular india in that it has previously been interpreted as continental in origin the succession comprises three main facies associations which are documented within this paper medium to fine grained muddy sandstone deposits of 5 75 m thickness are reinterpreted as tidally influenced delta deposits mudstone deposits of 3 20 m thickness with subordinate sandstones coals and carbonaceous shales are reinterpreted as delta top deposits and medium to coarse sandstones of 3 38 m thickness are interpreted as braided delta top channels the evidence for tidal influence arises from documentation of bidirectional cross strata tidal bundles tidal rhythmites and periodic variation in foreset thickness the recognition of tidal deposits indicates marine depositional conditions and significantly changes existing palaeogeographical models this in turn has important implications for our understanding of the depositional setting and distribution of the permian coals that occur across much of the southern supercontinent furthermore to the best of the authors9 knowledge coal bearing tidal delta deposits have not previously been described from continental interior basins

first ice core records of no3 stable isotopes from lomonosovfonna svalbard samples from two ice cores drilled at lomonosovfonna svalbard covering the period 1957 2009 and 1650 1995 respectively were analyzed for no 3 concentrations and no3 stable isotopes n 15

continental biogenic species in the greenland ice core project ice core tracing back the biomass history of the north american continent ammonium nitrate and organic acid records from the greenland ice core project deep ice core are discussed all species have a continental biogenic source that is situated predominantly on the north american continent for species deposited in summit central greenland the record therefore can be used to trace back the biomass history of the north american continent difficulty in the interpretation of these records arises from their unknown transfer behavior in a more alkaline atmosphere which characterizes glacial time periods compared to interglacial stadials this may have implications not only for weak acids such as formate and acetate but also possibly for the transport and incorporation of hno3 into aerosols whereas ammonium is probably not affected by the alkalinity change of the atmosphere our approach is to compare samples with similar h concentrations throughout the record from the records we infer several significant fluctuations in the extent of the laurentide ice sheet during the last glaciation we find evidence against the occurrence of an extensive younger dryas event in north america