landform regolith mapping in the west african context abstract in this paper we present an integrated landform regolith mapping protocol chart for west africa developed using a case from central burkina faso the chart accounts for i the specificities of the ubiquitous duricrust capped remnants of the regional paleolandsurfaces particularly the residual or detrital character of the fe duricrusts and ii the diversity of the remaining non duricrusted portions of the landscape with an emphasis on the pitfalls encountered in determining the in situ or transported character of the regolith the paper also provides field identification criteria and illustrations of the typical west african landform regolith associations the landform regolith mapping chart is integrated into a prospectivity chart which is used to define exploration guides i defining sampling strategies ii interpreting potential geochemical anomalies and iii targeting lateral extensions of known bedrock mineralizations the mapping protocol further allows for the definition of a class of landform regolith association propitious to supergene mineral concentrations the mapping protocol is shown to be transposable to wetter contexts and more generally to other tropical shield provinces

behavior of rare earth elements in a paleoweathering profile on granodiorite in the front range colorado usa abstract a paleoweathering profile on the boulder granodiorite in northern colorado provides an opportunity to trace the behavior of rees from parent rock through a weathering profile into unconformably overlying permian sediments with progressive upward weathering of the granodiorite na2o cao sio2 ta hf co th cr sc cr th zr hf la sc zr y and la th decrease al2o3 and fe2o3t increase and tio2 mgo k2o p2o5 rb zr sc cr co hf nb ta y th u ree ti nb and zr nb increase to maximum values and then either level off or decrease lree enrichment is less in the weathering profile than in the parent granodiorite and although the parent does not have an eu anomaly or only a slight positive anomaly all samples from the weathering profile and overlying sediments have significant negative eu anomalies this observation is especially important in that it shows conclusively that a negative eu anomaly can be produced during chemical weathering of granitoids we suggest these eu anomalies are due to relative enrichment of the other rees and partial loss of eu during the breakdown of plagioclase the boulder weathering profile also has a very minor negative ce anomaly that is within error of a ce anomaly in the parent in the unweathered parent 50 of the ree are contained in sphene and in the case of la also in allanite from 10 20 of the ree are contained in apatite and biotite hornblende and from 7 10 of the hrees are in zircon with exception of eu for which feldspars contribute about 8 negligible amounts of rees occur in the feldspars in weathered samples 75 of the rees are contained in clay minerals the crossover between sphene and clay control of rees occurs over a distance of 1 m near the contact with fresh rock except for their small negative eu anomalies the clay minerals have ree patterns very similar to those of the parent rock isocon plots suggest apparent enrichments of many elements in the boulder weathering profile result from losses of na ca and si during plagioclase weathering in addition variable amounts of sr eu ta nb p and ba were lost during weathering although th u zr y th sc zr hf lu hf and ti zr may have been transferred relatively unchanged from granodiorite parent to the bulk weathering profile most other element ratios and ree distributions were significantly changed during weathering this observation implies that caution needs to be exercised when using ree patterns and element ratios to trace sediment provenance the fact that most element ratios and ree distributions also differ between fountain sediments and the bulk weathering profile may be related to one or a combination of four factors listed in order of probable decreasing importance contribution of other sources to the fountain sediments sorting of minerals during sediment deposition remobilization of elements during diagenesis and leaching of elements by water flow through the upper meter of the weathering profile

geochemistry of laterites stability of al goethite al hematite and fe super 3 kaolinite in bauxites and ferricretes an approach to the mechanism of concretion formation

relief inversion in the geomorphological evolution of sub saharan west africa abstract the geomorphology of much of sub saharan west africa is dominated by the presence of plateaux and plains with ferruginous and locally aluminous bauxitic duricrusts the plateaux occur at different elevations and have been correlated as two or more palaeosurfaces across much of the region the duricrusts have generally been considered to be residual formed by conformable erosion and chemical wasting of immediately underlying bedrock this concept has been central to interpretations as diverse as the formation and evolution of the landscape and the development of geochemical exploration models recent regolith landform mapping field observations and experience from mineral exploration in southern mali and burkina faso however demonstrate that the duricrusts are mainly ferricretes i e fe oxide cemented sediments these observations require a re interpretation of the geomorphological evolution of the region during the cenozoic the landscape has evolved by several cycles of weathering and erosion deposition triggered by climatic tectonic or other environmental changes it is proposed that an initial bauxitic lateritic regolith was partly eroded following uplift and or a change to a more arid climate and that the detritus rather than being removed was deposited on slopes and valleys during a subsequent humid period of lateritic weathering fe oxide cementation of this detritus formed ferricrete dehydration and hardening of the ferricrete after further uplift or aridity increased its resistance to erosion resulting in relief inversion with the detritus in turn being deposited downslope this too has been weathered and cemented to form a younger ferricrete the occurrence of ferricrete landforms in adjacent countries noted by field observation and inferred from satellite imagery demonstrates that relief inversion is a very widespread and important phenomenon in southern mali burkina faso and adjacent countries in semi arid west africa

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

chemistry of modern soils as a guide to interpreting precambrian paleosols precambrian paleosols are potentially one of our best sources of information about the composition of the atmosphere early in earth s history to be used this way however an alteration profile must be shown to be an in situ product of vadose processes data from modern soils show that the ratios of less mobile elements such as zr ti and al can be used as a preliminary screen to test for the in situ nature of a profile if the ti zr ratio departs from that of the host rock by more than 40 or the ti al ratio departs by more than 50 for moderate degrees of weathering then a significant allochthonous contribution to the profile is indicated this technique correctly separates in place from allochthonous horizons when applied to independent data from two modern profiles a review of published precambrian profiles identifies two often cited examples denison and pronto as suspect based on these criteria in the interpretation of paleoatmospheres it is also necessary to show that fe is controlled not b

analysis of thickness changes and the associated driving factors on a debris covered glacier in the tienshan mountain abstract supraglacial debris complicates the melting state of debris covered glaciers and whether debris increases or decreases the rate of glacier melt is ambiguous according to different observations in this paper we aim to determine the potential factors that influence changes in thickness of debris covered glaciers first we present the thickness changes of a large debris covered glacier in the tienshan mountain using high resolution digital elevation model dem data from three periods in 2000 2009 and 2013 it is shown that the thickness changes differ greatly over the debris covered portions of the glacier these debris covered regions can be divided into three parts along the glacier axis according to the rate of thickness change specifically these parts include the zone of minimal change the zone of heavy thinning and the zone of slight thinning detailed information on the closely related factors including the debris thickness which was measured across the whole glacier during our field work and the presence of ice cliffs and supraglacial lakes detected on high resolution satellite images are combined to determine the reasons for the differences in melting state among the three zones the results show that the thickness changes of the debris covered glacier are jointly influenced by debris thickness and the presence of ice cliffs and supraglacial lakes moreover the dominant factor differs among the different zones the critical debris thickness which mostly appears in the minimal change zone and accelerates glacier melting as confirmed through field observations is not associated with glacier thinning because its location is close to the accumulation zone the regions where the rates of thinning are greatest coincide with the regions where the ice cliffs are densest where the debris is thicker than 1 m on average the glacier is still thinning slightly due to the presence of ice cliffs and lakes it is proven that the quantity and area of the ice cliffs and supraglacial lakes is the key to understanding the melting rate of debris covered glacier

late holocene variability in pelagic fish scales and dinoflagellate cysts along the west coast of vancouver island ne pacific ocean fish stocks and dinoflagellates are essential components of the marine food chain sediment cores from a predominantly anoxic basin in effingham inlet vancouver island british columbia archive a late holocene 500 5300 years bp record of paleoproductivity in the north american coastal upwelling domain cud we present evidence that late holocene changes in the dinoflagellate cyst assemblages sedimentary record and fish stocks in the northeastern pacific ocean fluctuated at least partially in accordance with regional and global climate cycles principal components analysis pca and trend wavelet and spectral analyses were used to identify relationships cycles and trends in sediment grey scale values and the abundances of fish scales and dinoflagellate cysts on centennial to millennial time scales most observed cycles fluctuated in intensity over time particularly following transition of the regional climate to a higher rainfall phase that impacted coastal oceanic dynamics 3400f150 years ago correlation of the marine paleoproductivity records observed in effingham inlet with solar influenced climate proxy cycles observed in the north atlantic region indicates that solar forcing at different scales might have influenced the climate in the northeast pacific as well in particular an 1100 to 1400 year cycle in regional climate is well represented in the fish productivity proxy and sedimentological record it was also observed that colder water high productivity selenopemphix nephroides and anchovydominated banchovy regimeq ecosystems alternate with warmer water herring dominated bherring regimeq ecosystems at millennial time scales the fish scale record preserved in effingham inlet indicates that the ne pacific is now in transition from an danchovy t to a dherringt dominated regime d 2005 elsevier b v all rights reserved

periodicity of climate conditions and solar variability derived from dendrochronological and other palaeoclimatic data in high latitudes abstract the periodicity of climatic processes in the barents sea region and along the arctic ocean coast during several hundred years has been studied by analyzing the tree ring chronologies for the regions close to the northern timberline in the barents sea region cyclicities of climatic processes with periods of around 90 30 35 22 23 18 and 11 12 years have been established by spectral analysis of the data for the kola peninsula wavelet analysis of annual series of conifer tree rings generalized for 10 regions along the northern timberline from the kola peninsula to chukotka for the period 1458 1975 has revealed the same periodicities for the vast areas of northern russia climatic cyclicity with a period of about 35 years is known as the bruckner cycle climatic cycles with periods of around 90 22 23 and 11 12 years correlate well with the corresponding solar activity cycles a possible solar forcing of periodic climatic processes and its nonlinear influence on the atmosphere ocean continental system are discussed

mineralogy and geochemistry of tropical rain forest soils ashanti ghana abstract a detailed study of the pedology mineralogy and geochemistry of soils and underlying saprolite has been made in the ashanti area of southwest ghana the soils in the area are kaolinite muscovite ferrasols and vary in thickness from 1 to 10 m depending on saprolite lithology topography and drainage porosity and eh decrease with depth in the soil profile while ph and grain density increased the dominant minerals are kaolinite muscovite goethite and this is reflected in the major element chemistry which is essentially sio 2 al 2 o 3 fe 2 o 3 h 2 o with minor amounts of k 2 o and tio 2 similar geochemical dispersion patterns are present for most elements in the lower or b soil horizons as in the saprolite with a similar correlation between the elements however these patterns are greatly modified in the surface or a soil horizon and the correlation is lost elements such as se mo as cd sb and pb appear to be naturally concentrated by soil processes in the a horizon while other elements such as th y and zr appear concentrated in the b horizon consideration of the trace element distribution patterns indicates that the present weathering profile appears to represent a truncated mature lateritic profile capped by a thin recent organic rich surface soil

rhenium and osmium isotope and elemental behaviour accompanying laterite formation in the deccan region of india this study presents major trace element and re os isotope data for two laterite profiles from the deccan region in india the first profile from bidar developed upon deccan basalt itself the second from goa formed on an archean greywacke both profiles show the typical changes in mineralogy and chemistry accompanying laterite formation from little altered parent rock at depth to altered saprolite depleted in mobile elements to a highly altered si depleted fe rich laterite capped by an iron rich crust at the surface rhenium and os concentrations show a systematic enrichment with increasing degree of alteration where the highest concentrations are found in the fe rich laterite crust the level of os enrichment is greater than that of re and as a consequence 187re 188os ratios are lower in the laterite than the parent rock with time this leads to the development of 187os 188os ratios that are also less radiogenic than the parent rock and this relationship holds irrespective of rock type or age or the time of laterite formation the marked enrichment of both re and os and the patterns of change above and below the paleowatertable indicates that both elements are highly mobile high eh and low ph conditions facilitate re and os dissolution and redistribution occurs via groundwaters whereas with increasing ph higher in the profile both elements are scavenged out of solution and precipitate either as pge rich alloys or are strongly partitioned into oxides or oxyhydroxides nevertheless the isotope and elemental data for both profiles suggests that at least some of the re and os must be externally derived either from aeolian deposition or from the lateral movement of solute laden groundwaters given the high levels of os in laterites their extensive geographical coverage of the continents and their active role in the surface water cycle it seems likely that they will exert a significant influence on the continental flux of os to the oceans that will in turn be sensitive to tectonic or climatic change

high resolution holocene vegetation history and climate from hole 1034b odp leg 169s saanich inlet canada abstract high resolution pollen analysis of laminated marine sediments from odp hole 1034b in saanich inlet british columbia reveals changes in vegetation and inferred climate during the holocene four main pollen zones are discerned using constrained cluster analysis although the timing of major vegetation changes at the saanich inlet is similar to other study sites in the pacific northwest the composition of pollen assemblage zones is different from the mainland sites vegetation assemblages reconstructed from the pollen and spore record include a douglas fir pseudotsuga menziesii parkland with abundant grass poaceae and bracken pteridium between 11 450 and 8300 bp all ages are calibrated calendar years oak quercus savanna or parkland with high grass and bracken 8300 7040 bp a mixed deciduous coniferous forest with oak western hemlock tsuga heterophylla and douglas fir 7040 5750 bp and the development of modern coastal temperate forest with the marked expansion of cedar cupressaceae western hemlock spruce picea and douglas fir 5750 1050 bp climatic periods inferred from the cores include an early holocene warm dry interval 11 450 8300 bp a warm period with mild winters 8300 7040 bp a period of transitional mid holocene climate 7040 5750 bp and the advent of a relatively cool wet neoglacial climate after 5750 bp modern conifer forests and oak savannas became established by about 3800 bp the saanich inlet pollen record indicates that vegetation and inferred climate change was particularly rapid between 8700 and 8300 bp when grass and bracken abruptly decrease and oak becomes a significant component of the paleovegetation because neoglacial conditions have prevailed from 3800 years to present in the pacific northwest factors other than climate such as anthropogenic modification of the landscape may be responsible for the persistence of oak savannas

climate change and decadal to centennial scale periodicities recorded in a late holocene ne pacific marine record examining the role of solar forcing abstract we present a decadal scale late holocene climate record based on diatoms biogenic silica and grain size from a 12 m sediment core vec02a04 obtained from frederick sound in the seymour belize inlet complex of british columbia canada sediments are characterized by graded massive and laminated intervals laminated intervals are most common between c 2948 2708 cal yr bp and c 1992 1727 cal yr bp increased preservation of laminated sediments and diatom assemblage changes at this time suggest that climate became moderately drier and cooler relative to the preceding and succeeding intervals spectral and wavelet analyses are used to test for statistically significant periodicities in time series of proxies of primary production total diatom abundance biogenic silica and hydrology grain size preserved in the frederick sound record periodicities of c 42 53 60 70 82 89 241 243 and 380 yrs are present results are compared to reconstructed sunspot number data of solanki et al 2004 using cross wavelet transform to evaluate the role of solar forcing on ne pacific climate significant common power of periodicities between c 42 60 70 89 241 243 and of 380 yrs occur suggesting that celestial forcing impacted late holocene climate at frederick sound replication of the c 241 243 yr periodicity in sunspot time series is most pronounced between c 2900 cal yr bp and c 2000 cal yr bp broadly correlative to the timing of maximum preservation of laminated sedimentary successions and diatom assemblage changes high solar activity at the suess de vries band may have been manifested as a prolonged westward shift and or weakening of the aleutian low in the mid late holocene which would have diverted fewer north pacific storms and resulted in the relatively dry conditions reconstructed for the seymour belize inlet complex

a basis for geochemical exploration models for tropical terrains abstract the principles and mechanisms of geochemical dispersion and the formation of anomalies govern the effective use of exploration geochemistry in any terrain the dispersion characteristics can be summarized in the form of geochemical exploration models that illustrate the nature of the surface expression of mineralization and that in turn should aid the planning execution and interpretation of future surveys in much of the tropics and sub tropics and in some areas in higher latitudes evidence of weathering under former seasonal tropical conditions is preserved these regions have similarities in landforms deeply weathered regoliths and hence geochemical dispersion patterns relating to such weathering conditions geochemical models can be based on these common features and their subsequent modification under different climatic regimes two model systems are described one in which the deeply weathered profile is preserved and the other in which the profile has been partially truncated these models can be used to compare and contrast the surface expression of mineralization under present day arid savanna and equatorial rainforest environments thereby in effect extending the data base for exploration of such areas

north atlantic oscillation dynamics recorded in greenland ice cores carefully selected ice core data from greenland can be used to reconstruct an annual proxy north atlantic oscillation nao index this index for the past 350 years indicates that the nao is an intermittent climate oscillation with temporally active coherent and passive incoherent phases no indication for a single persistent multiannual nao frequency is found in active phases most of the energy is located in the frequency band with periods less than about 15 years in addition variability on time scales of 80 to 90 years has been observed since the mid 19th century

changes of six selected glaciers in the tomor region tian shan central asia over the past 50 years using high resolution remote sensing images and field surveying as the major water resource of the tarim river glaciers in the tomor region have suffered major losses of ice in the last several decades based on topographic maps high resolution remote sensing image field survey data and previous studies changes of the six selected glaciers in the tomor region qingbingtan glacier no 72 qingbingtan glacier no 74 keqikekuzibayi glacier tomor glacier keqikar glacier and qiongtailan glacier over the past similar to 50 years were analyzed in this study analysis shows that all of the six glaciers showed continuous shrinkage the reduction rate of glacier no 72 terminus retreat of 41 m a 1 and area loss of 21 5 during 1964 2009 was higher than the others with a dramatically increased rate this dramatic ice thinning related glacier front retreat and area loss of the six glaciers suggests that glaciers in the tomor region might currently be suffering negative mass balance in response to the ongoing temperature rise differences in changes of the six glaciers are influenced by debris cover and other topographical factors c 2013 elsevier ltd and inqua all rights reserved

recognition of supraglacial debris in the tianshan mountains on polarimetric sar images abstract debris cover is widely present in the ablation areas of mountain glaciers such debris plays an important role in glacier mass balance but it complicates the glacier boundary and area estimation when using remotely sensed images automatic recognition of the debris is much more difficult than recognizing bare ice on optical remotely sensed images because the debris has almost the same spectral characteristics of the surrounding terrain in this paper the scattering characteristics of the debris on the c and l band polarimetric sar images are presented and analyzed to study the possibility of recognizing debris thickness and extent the koxkar glacier in the central tianshan mountain range was selected as the study area it was found that debris is distinct from bare ice in cross polarization hv of both the l and c bands the l band volume scattering component acquired from target decomposition increases with debris thickness when the debris is less than 25 cm deep but the volume scattering does not increases if the debris is thicker than 25 cm in contrast the c band sar data does not appear to be sensitive to debris thickness this difference may be caused by different radar penetration depth of the debris on the basis of the polarimetric property analysis two methods were developed to determine the extent of the debris in the first method the simple threshold to distinguish debris from non debris areas is presented using this threshold approximately 90 of the debris can be recognized in the second method by combining more polarimetric features and support vector machines recognition of debris reaches an accuracy greater than 95

the mineralogy and geochemistry of the cerro matoso s a ni laterite deposit montelibano colombia the cerro matoso s a ni laterite deposit in northwest colombia is an important producer of ferronickel expanded production of ferronickel is planned to be 55 000 mt by mid 2004 the deposit is developed over a peridotitic protolith that is exposed in the form of an elongated hill the deposit s weathering profile is variable both vertically and laterally and 10 distinct lithostratigraphic units have been characterized two typical sections through the weathering profile were sampled from an area of the mine with high pit 1 and lower pit 2 ni grades bench mapping has shown that pits 1 and 2 have distinctly different weathering profiles from bottom to top the profile in pit 1 is weakly serpentinized peridotitic protolith saprolitized peridotite green saprolite main ore horizon tachylite used by mine geologists to describe an enigmatic fe oxide horizon black saprolite yellow laterite red laterite the sequence is then capped by a magnetic to nonmagnetic ferricrete known locally as canga the succession in pit 2 is from serpentinized peridotite saprolitized peridotite brown saprolite yellow laterite red laterite and lacks the green saprolite ore horizon all the units in pit 2 have currently uneconomic ni grades the thickness of the units is highly variable but most of the major horizons have maximum thicknesses of the order of tens of meters both pits contain abundant fault and joint related silicate veins sometimes in stockworks in the lower part of the sequence these veins contain the distinctive green mineral known as garnierite actually pimelite a form of nickeliferous talc as well as quartz and chalcedony and they can have a ni content of up to 30 to 40 wt percent the bulk geochemistry in most units of both profiles shows a fairly typical ni laterite pattern in which mgo and sio2 are depleted toward the top of the sequence whereas feo increases mineralogic studies confirm that the protolith in both pits is a partly up to 50 serpentinized harzburgite and that in pit 1 the main ni bearing phases in the weathering profile are ni sepiolite ni serpentines and other hydrous silicates the garnierites in cerro matoso have been identified as pimelite in which various amounts of ni have substituted for mg the upper part of the sequence is dominated by amorphous and crystalline fe oxide phases the magnetic canga is composed mainly of maghemite that may have been produced by oxidation of magnetite rich units the mineral content of pit 2 is dominated by poorly structured fe oxides or goethite and by subordinate clay minerals and quartz the geochemistry and mineral content of the deposit suggest that as in many other ni laterite deposits ore genesis is strongly controlled by local climate topography and drainage mass balance calculations indicate that the profiles in pits 1 and 2 had different weathering histories because the degree of profile collapse and residual enrichment in pit 1 is far more extreme than that in pit 2 this difference may be the result of different degrees of serpentinization of the protolith in the two pits and potential dilution of the ore in pit 2 by input from an exotic unit ni in the deposit has also undergone supergene enrichment resulting from the leaching of ni from the upper part of the lateritic profile and its transport to the green saprolite unit where the ni was fixed in silicate minerals

influence of the pacific decadal oscillation el nino southern oscillation and solar forcing on climate and primary productivity changes in the northeast pacific evidence of 11 year schwabe solar sunspot cycles el nino southern oscillation enso and the pacific decadal oscillation pdo were detected in an annual record of diatomaceous laminated sediments from anoxic effingham inlet vancouver island british columbia radiometric dating and counting of annual varves dates the sediments from ad 1947e1993 intact sediment slabs were x rayed for sediment structure lamina thickness and composition based on gray scale and subsamples were examined for diatom abundances and for grain size wavelet analysis reveals the presence of w2e3 w4 5 w 7a ndw9e12 year cycles in the diatom record and an w11e13 year record in the sedimentary varve thickness record these cycle lengths suggest that both enso and the sunspot cycle had an influence on primary productivity and sedimentation patterns sediment grain size could not be correlated to the sunspot cycle although a peak in the grain size data centered around the mid1970s may be related to the 1976e1977 pacific climate shift which occurred when the pdo index shifted from negative cool conditions to positive warm conditions additional evidence of the pdo regime shift is found in wavelet and cross wavelet results for skeletonema costatum a weakly silicified variant of s costatum annual precipitation and april to june precipitation higher spring april may values of the north pacific high pressure index during sunspot minima suggest that during this time increased cloud cover and concomitant suppression of the aleutian low al pressure system led to strengthened coastal upwelling and enhanced diatom production earlier in the year these results suggest that the 11 year solar cycle amplified by cloud cover and upwelling changes as well as enso exert significant influence on marine primary productivity in the northeast pacific the expression of these cyclic phenomena in the sedimentary record were in turn modulated by the phase of pdo as indicated by the change in period of enso and suppression of the solar signal in the record after the 1976e1977 regime shift

isolation basin records of late quaternary sea level change central mainland british columbia canada isolation basin records from the seymour belize inlet complex a remote area of central mainland british columbia canada are used to constrain post glacial sea level changes and provide a preliminary basis for testing geophysical model predictions of relative sea level rsl change sedimentological and diatom data from three low lying 4 m elevation basins record falling rsls in late glacial times and isolation from the sea by 11 800 11 200 14c bp a subsequent rsl rise during the early holocene 8000 14c bp breached the 2 13 m sill of the lowest basin woods lake but the two more elevated basins sill elevations of 3 6 m remained isolated at 2400 14c bp rsl stood at 1 49 0 34 m above present mtl falling rsls in the late holocene led to the final emergence of the woods lake basin by 1604 36 14c bp model predictions generated using the ice 5g model partnered with a small number of different earth viscosity models generally show poor agreement with the observational data indicating that the ice model and or earth models considered can be improved upon the best data model fits were achieved with relatively low values of upper mantle viscosity 5 1019 pa s which is consistent with previous modelling results from the region the rsl data align more closely with observational records from the southeast of the region eastern vancouver island central strait of georgia than the immediate north bella bella bella coola and prince rupert kitimat and areas to the north west queen charlotte sound hecate strait underlining the complexity of the regional response to glacio isostatic recovery

element distribution patterns in laterites of southern mali consequence for geochemical prospecting and mineral exploration abstract in areas of tropical weathering the development of a thick extensive mantle is a major obstacle in the application of geochemical exploration methods using media such as soil or stream sediments the combined effects of deep lateritic weathering and differential erosion processes lead to a great variety of materials exposed at the land surface consequently depending on the nature and degree of evolution of the facies sampled the geochemical signal reflecting characteristic features of parent rocks and mineralization may be altered in different ways in this paper the results of a detailed multielement geochemical survey near the village of dagadamou southern mali are presented as an example of exploration in tropical terrain about 1000 samples were collected over an area of 25 km 2 on a regular sampling grid of 100 200 m and analyzed by plasma emission spectrometry for major and trace elements the main geochemical differentiation trend corresponds to the opposite variation of sio 2 and fe al contents and reflects the nature of the sampled material this factor also reflects the relative amounts of quartz kaolinite gibbsite goethite and hematite estimated after normative calculations ferricrete samples with high al and fe contents are also enriched in trace elements p v cr as mo nb and cu which are retained in the weathering profile bound on secondary fe oxihydroxide minerals on the other hand silt clay soils developed on flat areas are mainly composed of quartz and kaolinite extracted from deeper zones of the weathering profile by termite activity and further accumulated in the topographic depressions such soils also contain concentrations of heavy minerals characterized by high zr ti y and ce contents further leaching of clay particles is marked by a quartz and zr rich halo at the footslope of the ferricrete plateau gritty layer derived from the dismantling of ferricrete which normally occurs on slopes have intermediate compositions and are relatively enriched in al kaolinite and k 2 o cu ni and ba compared to ferricrete with similar fe content this example provides a model of element dispersion during the evolution of a lateritic landscape which can be used as a basis for interpreting geochemical exploration data in tropical terrains

scaling in turbidite deposition abstract we propose that the distribution of layer thicknesses of turbidite deposits that show minimal erosional truncation and amalgamation should obey the power law n h h b where n h is the number of layers of thickness greater than h and b 1 we support this proposal with two sets of observations one from formation microscanner images obtained in offshore wells that penetrate tertiary fore arc turbidites hiscott et al 1992 and the other from our own field measurements of turbidites in the neoproterozoic kingston peak formation deposited in a glacially influenced rift basin both sets of observations show roughly the same power law distribution above a small h cutoff otivated by the possible generality of these results and given strong geological and sedimentological contrasts between the two data sets we consider the available theoretical and experimental evidence that could support or deny these observations we tentatively conclude that the power law is generic in data sets characterized by minimal erosional truncation and amalgamation but emphasize that further study is required for a definitive statement proceeding from the assumption that the scaling law is valid for arbitrarily thin layers we derive an upper bound for b we then detail simple and plausible assumptions that provide a theoretical estimate of b we discuss possible ramifications of this analysis for the interpretation of further data

dendroglaciological investigations of mid to late holocene glacial activity in the mt waddington area british columbia coast mountains canada dendroglaciological investigations near mt waddington in the central british columbia coast mountains provide an enhanced perspective of holocene glacial activity field investigations at confederation franklin and jambeau glaciers led to the discovery of subfossil wood mats encased in glacial deposits and glacially sheared stumps buried beneath till radiocarbon dated wood collected from valley bottom and lateral moraine sites at confederation glacier suggest that an early holocene advance occurred at c 5665 cal yr bp followed by succeeding intervals of glacier expansion at c 3700 and 3500 cal yr bp at jambeau glacier detrital wood mats buried close to the contemporary lateral moraine crests document glacier expansion at c 3000 cal yr bp detrital subfossil wood buried in lateral moraines at the confluence of confederation and franklin glaciers records distinct episodes of little ice age glacier expansion as early as c 1212 cal yr ad and suggests the glacier surface continued to thicken u

the role of global and local factors in determining the middle to late holocene environmental history of the south kurile and komandar islands northwestern pacific abstract the study of holocene deposits from northwestern pacific islands is very important for understanding the natural development of the area in the context of oceanic climate strong microclimate variability and the influence of contrasting marine currents holocene sections from bering island record the following events cooling at about 4600 4500 yr bp warming at about 3500 3400 yr bp cooling at about 3000 yr bp sea level rise up to 1 5 m at about 2700 bp cooling at about 1800 1400 yr bp and sea level rise at about 1000 yr bp on the south kuriles a dry and cool climate changed to warm and moist about 7000 6500 yr bp later than on hokkaido island at this time the kuroshio current system became more active and birch assemblages were replaced by cool temperate broadleaf forests and mixed coniferous broadleaf forests at the holocene optimum about 6000 yr bp temperate broadleaf forest occupied almost all of kunashir and the okhotsk side of iturup and the climate was warmer than present the highest sea level position reached was 2 5 3 m above present level about 6500 6300 yr bp during the cooling about 4700 4500 yr bp island vegetation changed slightly due to the influence of warm currents major sea level regression during this period led to the formation of extensive coastal dune fields the warming at the beginning of the late holocene was almost as great as that of the holocene optimum two minor transgressions are recorded the vegetation changes and climatic deterioration that took place in the second half of the late holocene resulted in either a disappearance of thermophylous taxa or in a southward shift of their natural habitats during the cooling from 1700 to 1300 yr bp the isthmus area increased coastal wetlands with lakes and coastal dunes with paleosols were formed and grassland and swamp landscapes developed late holocene warming was not intensive volcanic impact on environments led to changes in vegetation assemblage swamping of the area and thick soil profile formation

glacier branch lines and glacier ice thickness estimation for debris covered glaciers in the central tien shan information about the ice volume stored in glaciers is of high importance for sustainable water management in many arid regions of central asia several methods to estimate the ice volume exist however none of them take the specific characteristics of flat terminus debris covered glaciers into account we present a method for deriving spatially distributed ice thickness for debris covered dendritic glaciers which are common not only in central tien shan but also in several other mountain ranges in high asia the method relies on automatically generated branch lines observed surface velocities and surface topographic parameters as basic input branch lines were generated using thiessen polygons and dijkstra s path algorithm ice thicknesses for four debris covered glaciers south inylchek kaindy tomur and koxkar glaciers have been estimated along the branch line network solving the equation of laminar flow for koxkar and south inylchek glaciers respectively maximum thicknesses of 250 and 380 m were estimated these results differ by 50 m compared with gpr measurements with an uncertainty for the debris covered parts of 40 based on geodetic mass balances we estimate that the investigated glaciers lost between 6 and 28 of their volume from 1975 to the early 2000s

a fast and easy method to derive highest resolution time series datasets from drillcores and rock samples abstract we present a fast method to obtain highest resolution greyvalue datasets from digital core images these datasets are processed using a software package developed by us artificially introduced trends in the datasets are corrected disturbances i e cracks voids are eliminated to reduce the high level noise in data we have developed a vector filter that effectively removes such noise application of the method to odp drillcores from the santa barbara basin allowed exact correlation of two drillcores from the same basin the influence of the termination of the last glacial cold period on the flux rates in the basin are reflected in the greyvalue datasets we found a transitional period of about 3000 yr between the end of the last glacial cold period and the onset of post glacial climatic oscillation in the basin fourier analyses show that the high resolution greyvalue time series record climatic cycles with frequencies as high as 1 cycle yr varves

early 21st century glacier thickness changes in the central tien shan abstract although studies based on satellite gravimetry 2003 2010 and laser altimetry 2003 2009 measurements have achieved region wide glacier mass change for the tien shan the dynamic process of glacier yet to be closely monitored and understood so that its impact can be assessed accurately in this study we investigated region wide glacier thickness change in the central tien shan cts during 2000 2012 by differencing the shuttle radar topographic mission srtm digital elevation model dem with a newly constructed dem from 27 tandem x images for a total glacier area of 7239 8 527 2 km 2 an average glacier thickness change rate of 0 24 0 22 m a was derived this result agrees well with the result based on satellite laser altimetry measurements reported earlier 0 31 0 41 m a with temporal synchronization a fine spatial resolution and wide coverage our measurements are able to reveal abundant glacier change features and dependencies in the cts firstly the lower mountains have seen a more severe glacier decline and the glaciers facing the prevailing wind westerlies have experienced a greater decline because of the stronger evaporation furthermore those glaciers lying along the extremely high meridian mountain range have obviously gained mass in their upper reaches because the air current from the west is blocked and lifted by the meridian mountain range secondly for the entire glacier body the theoretical hyperbolic dependence between debris thickness and ice decline was very difficult to establish some huge glaciers covered by heavy debris have still experienced a severe decline however even though the heavy debris did not prevent the ablation its attenuating effects were considerable thirdly for the glaciers that surged before 2000 the mass gain in the restoring zones has not been enough to cover the mass loss in ablation zones some large glaciers surged again during 2000 2012 however with much lower magnitudes than in previous surges in general the surge glaciers have experienced a greater decline than the non surge glaciers fourthly due to the ice front calving and subglacial thermal erosion glaciers connected to proglacial lakes have receded and thinned much more rapidly than the land terminated glaciers overall the glaciers in the cts are more stable than those in other parts of the tien shan however the glacier state there is still alarming a moderate average thinning rate was derived because the drastic thinning in the ablation zones was balanced by the slight thinning in the broad accumulation zones

gold and pathfinder elements in ferricrete gold deposits of the yilgarn craton of western australia a review with new concepts abstract secondary mineral deposits have played an important role in the global mineral resource economy for over 50 years with lateritic au al fe and ni deposits having a significant input to global metal production and reserves in the yilgarn craton of western australia a deeply weathered mantle is commonly capped with 2 10 m of lateritic residuum residual lateritic gravels and duricrust and or ferricrete fe oxide cemented sediment which formed under seasonally humid tropical and sub tropical climates during the cenozoic the principal constituents of these units are goethite hematite maghemite kaolinite and quartz they are commonly overlain by younger 2 10 m thick transported cover deposited under later semi arid conditions both ferricrete and lateritic residuum may host exploitable secondary gold deposits typically small

study on the change of keqikaer glacier during the last 30 years mt tuomuer western china using radio echo sounder ice thickness of keqikaer glacier tongue was measured in 1981 and 2004 data obtained by comparing topographical maps aerial and satellite photographs at different times illustrates changes of the thickness and advance retreat of keqikaer glacier keqikaer glacier has been in intensive retreat since the 1990s and become thinner since the 1980s measured thickness of the ice tongue indicates reducing with a speed of 0 5 1 5 m a 1 since 1981 the shrinkage of the glacier terminus is less than 2 of the total length during the last 30 years however the retreat of terminus position and the thinning of the ice thickness provides significant information that these glaciers on the south slope of mt tuomuer are in an intensively decreasing phase in recent time

possible solar forcing of century scale drought frequency in the northern great plains a 2100 yr decadal resolution salinity and aridity proxy record of lacustrine ostracode shell mg ca ratios from a closed basin lake in the northern great plains shows statistically significant periodicities of 400 200 130 and 100 yr these periodicities are similar to the three principal solar oscillation periods 420 218 143 yr as inferred from the atmospheric radiocarbon record suggesting strong solar forcing of century scale drought frequency with a fundamental 400 yr period and its 2nd 3rd and 4th harmonics our proxy record correlates visually and statistically cross spectral analysis with the atmospheric 14 c record solar proxy and the gisp2 greenland ice sheet project two 18 o record climate proxy showing that solar minima are in phase with drought periods in the northern great plains and cold periods in greenland this spectral similarity together with phase correlation indicates a possible teleconnection of century scale global climate fluctuations through common solar forcing

climate cyclicity in late holocene anoxic marine sediments from the seymour belize inlet complex british columbia abstract an 8 72 m late holocene sediment core vec02a07 obtained from alison sound in the belize seymour inlet complex of central british columbia canada was deposited between 3500 1000 yr bp under primarily anoxic marine conditions this core contains a detailed cyclic record of land sea interactions as evidenced by significant fluctuations in marine primary productivity and changes in the supply of terrigenous material that can be related to long term variation in the relative influence of the aleutian low al and north pacific high nph sedimentologically the core is characterized by alternating intervals of fine grained massive intervals 70 laminated intervals 23 turbidites 5 and graded silt clay layers 2 the laminated intervals are comprised of couplets that vary between light coloured diatom rich layers deposited primarily during the summer months and dark coloured mineral rich layers deposited during winter laminated couplets are most common in portions of the core deposited between 3150 and 2700 yr bp which corresponds to an episode of regional neoglaciation time series analysis was carried out on high resolution particle size measurements obtained from core sub samples and on sediment grey scale colour variability derived from x ray scans of the core non linear time series analyses revealed that the succession of massive and laminated sedimentation displayed characteristics of self organization following a power law relationship for core length segments of 13 cm 50 years of deposition contained evidence of sedimentary depositional cycles of 70 96 135 155 and 250 330 years that reflect changes in al and nph mediated regional precipitation patterns that can in turn be related to larger scale climate drivers such as the pacific decadal oscillation pdo or solar irradiance cyclicity

climate shift at 4400 years bp evidence from high resolution diatom stratigraphy effingham inlet british columbia canada abstract diatom paleoecology and climatic interpretations were assessed from a 15 cm long laminated sediment slab extracted from an anoxic fjord in southwest british columbia the slab spans at least 62 years of deposition determined from counting varves and is dated at approximately 4400 years bp the slab shows a sedimentation pattern where thick diatom rich varves at the bottom become thinner and more silty toward the top thin section analysis reveals that the thicker varves contain a distinct succession of diatoms representing seasonal deposition throughout each year annual scale subsampling shows that the abundance of coastal marine diatoms namely a weakly silicified form of skeletonema costatum decreased over the 62 year period while benthic and brackish water diatoms such as planothidium delicatulum and achnanthes minutissima increased with the concomitant increase in silt the increase in such benthic species and silt along with the presence of 1 cm thick nonlaminated intervals is interpreted to represent deposition during progressively increasing precipitation over time these sedimentation patterns and changes in diatom assemblages may signify a change in the relative intensities of the aleutian low al and north pacific high nph atmospheric pressure systems thicker diatomaceous varves at the bottom of the slab reflect a stronger nph system with associated coastal upwelling and enhanced diatom production the thinner silty varves at the top of the slab suggest that the al system was prevalent resulting in greater amounts of precipitation and reduced upwelling the findings of this study show that significant natural environmental change can occur within a twenty year time frame and can provide a basis for the study of modern change in the ocean atmosphere system over the northeast pacific ocean

symmetries in geology and geophysics symmetries have played an important role in a variety of problems in geology and geophysics a large fraction of studies in mineralogy are devoted to the symmetry properties of crystals in this paper however the emphasis will be on scale invariant fractal symmetries the earth s topography is an example of both statistically self similar and self affine fractals landforms are also associated with drainage networks which are statistical fractal trees a universal feature of drainage networks and other growth networks is side branching deterministic space filling networks with side branching symmetries are illustrated it is shown that naturally occurring drainage networks have symmetries similar to diffusion limited aggregation clusters

late holocene sedimentary response to solar and cosmic ray activity influenced climate variability in the ne pacific marine laminated sediments along the ne pacific coast effingham inlet vancouver island provide an archive of climate variability at annual to millennial scales a 7 75 m portion of piston core tul99b 03 was deposited during a 3045 year interval 1440 4485 years before present ybp under primarily anoxic conditions darker clay laminae were deposited under higher precipitation conditions in winter and diatom dominated laminae were laid down when marine productivity was higher in the spring through autumn wavelet transform and other time series analysis methods were applied to sediment color i e gray scale values line scans obtained from x ray images and compared with global records of cosmogenic nuclides 14 c and 10 be as well as the ice drift index hematite stained grains record to detect cycles trends and nonstationarities in the climate and sedimentary pattern our results show that the marine sedimentary record in the ne pacific responded to abrupt changes and long term variability in climate that can be linked to external forcing e g solar and cosmic irradiance specifically a strong cooling in the ne pacific at 3550f160 ybp can be correlated to a weakening of high frequency 50 150 years pulses in sun activity at the gleissberg cycle band similar to what occurred at the onset of the dlittle ice aget at 1630 ad three intervals of unusually low sun activity at 2350 2750 and 3350 ybp are characterized by thick clay rich annual sedimentation that we interpret as representative of unusually wet conditions these intervals of higher precipitation conditions may have been related to a regional intensification of the aleutian low al caused by an eastward migration of the center of action coa of the al which occurs during intervals of solar minima dryer conditions in the region occur when the coa of al migrates westward and the coa of the north pacific high nph migrates northward during intervals of solar maxima a cyclicity of 50 85 33 36 and 22 29 years in the sediment color record lamination thickness and 14 c cosmogenic nuclide characterized the relatively warm interval from 3550 to 4485 ybp this record is similar to that of present day low and highfrequency variants of the pacific decadal oscillation and aleutian low d 2004 elsevier b v all rights reserved

local environmental changes recorded by clay minerals in a karst deposit during mis 3 la chauverie sw france abstract the four stratigraphic units of the late pleistocene mis 3 clay rich deposit of la chauverie charente sw france have been characterized for mineral composition the lower part of this 75 cm thick karst deposit preserves a mammal fauna typical of temperate climate followed by an assemblage pointing to a colder phase the clay fraction of both horizons mostly results from mineral transformations of the clays contained in the sediments of the paleogene formation surrounding the cave because clay mineral properties and changes intimately depend on the physico chemical conditions and reaction kinetics prevailing at a given time in the soils they are highly temperature related notably changes are rapid under temperate conditions but slow in tundra like cold contexts as shown by the altered inherited mica illite as well as by the increase of crystallinity of kaolinite particles at la chauverie these transformations were marked in the stratigraphically lower part of the deposit formed under temperate conditions conversely as reflected by the reduction of the kaolinite smectite ratio characterizing the sediments of the upper horizon the pedological evolution was limited during the subsequent cold phase here both illite smectite and kaolinite smectite mixed layers become smectite richer than their equivalent in the paleogene the parallelism between paleontological evidence and mineral signature in recording a relatively rapid millennial scale shift towards colder conditions suggests that clay mineral assemblages from cave deposits can be used to assess paleoclimatic and paleoenvironmental dynamics at local scale nonetheless future research should test this potential tool in more appropriate thicker deposits investigated using other independent paleobiological and geochemical indicators

investigating mountain glacier motion with the method of sar intensity tracking removal of topographic effects and analysis of the dynamic patterns abstract accurate knowledge of glacier motion variations can provide critical information for assessing glacier mass balance changes for fast flowing high mountain glaciers sar intensity tracking may be the most appropriate technique to measure their motions however due to the slant range imaging mode topographic relief can give rise to pixel disalignments in sar image and then bring errors to sar intensity tracking as a result the application of sar intensity tracking has been limited to sar pairs with short baselines because the use of image pairs with long baselines would suffer significant topographic effects over mountainous regions this paper presents an improvement to sar intensity tracking by adding an explicit procedure of topographic correction such correction will not only significantly increase the accuracy of the sar pairs with shorter baselines but also allow the image pairs with longer baselines to be taken advantage of instead of letting them to be dismissed otherwise using the improved sar intensity tracking technique we derive the highly precise motion variation patterns of 11 giant glaciers in tuomuer khan tengri mountain ranges one of the largest glacial centers in tien shan the results manifest that most glaciers there saw flow deceleration during the observation interval 6 january 2007 4 march 2011 except the northern and southern inylchek glacier regarding the glacier motion mechanism ice thermal character and climate features there we deduce that the flow acceleration and deceleration should be the sign of glacier mass gain and loss respectively and the sharp and slight flow decelerations should correspond to remarkable and mild mass loss respectively we confirm these deductions by exploring the close link between the long term motion variations and the dynamic patterns of these glaciers the obvious diversities of the dynamic patterns among the studied glaciers are ascribed to the discrepancies of the glaciers location and scale longer observations are still needed to confirm or redefine these findings in the future though provided that the precipitation keeps increasing whether the glaciers in tuomuer khan tengri mountain ranges will regain mass or not has not been determined yet

orbital control on cyclical primary productivity and benthic anoxia astronomical tuning of the telychian stage early silurian abstract the identification of milankovitch cycles and the establishment of a high resolution astronomical time scale for the palaeozoic represent a research frontier in cyclostratigraphy and astrochronology a continuous core drilled through the telychian stage llandovery silurian of the paslek formation in the baltic basin poland is characterized by repetitive centimetre scale alternations of homogeneous greenish grey mudstones and faintly laminated dark grey to black mudstones such lithological rhythmicity reflects a cyclical variation in redox conditions at the sediment water interface and therefore was used to construct a floating astronomical time scale ats for the telychian stage the cyclostratigraphic analysis was performed on a 5 mm resolution greyscale scan based upon photographs of the slabbed core with lower values associated with greenish grey mudstones and higher values related to dark grey to black mudstone facies spectral density estimation by means of the multitaper method mtm reveals significant peaks rising above the 95 red noise confidence level that we interpret as the 405 kyr long eccentricity short eccentricity obliquity and precession components the mtm evolutive power spectral analysis epsa shows a gradual increase in the velocity of sedimentation from 5 03 m myr in the lowermost interval to 5 48 m myr towards the uppermost part of the studied sequence we postulate that the observed cycles reflect orbitally driven climatic variations from stable wet conditions to monsoon like high seasonal contrasts that affected weathering intensity runoff and nutrient supply these cyclical variations led to rhythmic variations in organic matter fluxes and benthic anoxic conditions in the analysed record orbital precession influenced the deposition of the greenish grey mudstone and dark grey to black mudstone couplets occurring on average every 10 cm furthermore long eccentricity modulation of precession controlled the relative depositional predominance of one facies over the other observed periodicities resemble those of cenozoic and mesozoic orbitally controlled records thus suggesting that during the silurian the orbital eccentricity forcing on the carbon flux acted in the same way as in the cenozoic and mesozoic the orbital tuning of the studied interval calibrated by means of accurate acritarch biostratigraphy allowed for the estimation of an astronomically calibrated duration for the telychian stage of about 5 46 myr

cyclic variation and solar forcing of holocene climate in the alaskan subarctic high resolution analyses of lake sediment from southwestern alaska reveal cyclic variations in climate and ecosystems during the holocene these variations occurred with periodicities similar to those of solar activity and appear to be coherent with time series of the cosmogenic nuclides 14c and 10be as well as north atlantic drift ice our results imply that small variations in solar irradiance induced pronounced cyclic changes in northern high latitude environments they also provide evidence that centennial scale shifts in the holocene climate were similar between the subpolar regions of the north atlantic and north pacific possibly because of sun ocean climate linkages

thermal regime of a supraglacial lake on the debris covered koxkar glacier southwest tianshan china a supraglacial lake was surveyed on the koxkar glacier in southwest tianshan from july to september 2007 and july to september 2008 and the temperature variation characteristics of the lake debris and debris free ice were analyzed at different depths to determine the thermal regimes in addition the discrepancies of temperature variation characteristics were investigated for different geomorphic units of the ablation zone of the koxkar glacier it was found that daily temperature variation curves for deep water are v shaped because meltwater from the glacier surface at temperatures of around 0 c feeds the lake and mixes with the relatively high temperature surface water during the day as the water temperature rises to approximately 4 c the mixed water sinks and forms a low temperature trough in the deep water of the lake in the middle of the day the vertical lapse rate of the lake water temperature against depth 0 33 c m has a magnitude lower than that of the debris 4 29 c m and that of the debris free ice 0 38 c m in the koxkar glacier s ablation zone the temperature curve for the surface water largely varied between the temperature curves for the debris at depths of 0 2 and 0 5 m the surface thermal condition of the ablation zone is significantly affected by the daily weather and there is a limited influence in debris at a depth of 1 m and in the lake at a depth of 5 m

heterogeneous mass loss of glaciers in the aksu tarim catchment central tien shan revealed by 1976 kh 9 hexagon and 2009 spot 5 stereo imagery the meltwater released by the glaciers in the aksu tarim catchment south of tomur peak central tien shan feeds the tarim river which is the main artery for the oases at the northern margin of the taklamakan desert the correct modeling of the contribution of the glaciers meltwater to the total runoff of the tarim river is hampered by the lack of mass balance data multi temporal digital terrain models dtms allow the determination of volume changes for large samples of glacier here we present the mass changes for 12 glaciers using 1976 kh 9 hexagon 2000 srtm3 and 2009 spot 5 datasets the results show that most of the glaciers have been losing mass since 1976 the largest glaciers koxkar and west qongterang lost 0 27 0 15 m w e a 1 and 0 43 0 15 m w e a 1 between 1976 and 2009 despite thick debris cover however some smaller glaciers show mass gain at their tongues indicating glacier surges using srtm3 data the volume gain of qinbingtan glacier no 74 could be dated to the time period 1999 2009 the overall mass budget of 0 33 0 15 m w e a 1 for 1976 2009 of the investigated glaciers is within the variability range of the global average however in the recent years 1999 2009 a slightly decelerated mass loss of 0 23 0 19 m w e a 1 could be observed c 2012 elsevier inc all rights reserved

holocene tree line and climate change on the queen charlotte islands canada palynological study of two subalpine ponds on the queen charlotte islands reveals changes in tree line and climate during the holocene the findings agree with previous reconstructions from nearby louise pond on the queen charlotte islands that suggest a warmer than present climate and higher than present tree lines in the early holocene ca 9600 660014c yr b p basal ages at sc1 pond and shangri la bog indicate that the basins did not hold permanent water before 720014c yr b p consistent with a warmer and drier early holocene previously inferred from louise pond pollen and plant macrofossils indicate the initial establishment of subalpine conditions by 6090 9014c yr b p similar to the 5790 13014c yr b p age for cooling inferred from louise pond conditions similar to present were established at sc1 pond by 3460 10014c yr b p confirming the previous estimate of 340014c yr b p at louise pond this 340014c yr b p vegetation shift on the queen charlotte islands corresponds with the beginning of the tiedemann glacial advance in the south coastal mountains of british columbia ca 330014c yr b p the peyto and robson glacial advances between 3300 and 280014c yr b p in the rocky mountains and climatic cooling inferred from palynological studies throughout southern british columbia northern washington and southeast alaska these findings confirm that changes in regional climate influenced changes in vegetation in coastal british columbia

dinoflagellate cyst based reconstructions of mid to late holocene winter sea surface temperature and productivity from an anoxic fjord in the ne pacific ocean abstract published contemporary dinoflagellate distributional data from the ne pacific margin and estuarine environments n 136 were re analyzed using canonical correspondence analysis cca and partial canonical correspondence analysis pcca these analyses illustrated the dominant controls of winter temperature and productivity on the distribution of dinoflagellate cysts in this region dinoflagellate cyst based predictive models for winter temperature and productivity were developed from the contemporary distributional data using the modern analogue technique and applied to subfossil data from two mid to late holocene 5500 calendar years before present present cores tul99b03 and tul99b11 collected from effingham inlet a 15 km long anoxic fjord located on the southwest coast of vancouver island that directly opens to the pacific ocean through barkley sound sedimentation within these basins largely comprises annually deposited laminated couplets each made up of a winter deposited terrigenous layer and spring to fall deposited diatomaceous layer the effingham inlet dinoflagellate cyst record provides evidence of a mid holocene gradual decline in winter sst ending with the initiation of neoglacial advances in the region by 3500 cal bp a reconstructed late holocene increase in winter sst was initiated by a weakening of the california current which would have resulted in a warmer central gyre and more el nino like conditions

all age depth models are wrong but how badly the uncertainty and error associated with fitted age depth models were investigated by fitting a range of models to sets of simulated radiocarbon dates based on varved sediments and comparing the modelled relationship with the varve timescale with large numbers of dates cubic smooth splines out perform other models with few dates no model reliably provides a good fit to reality and calculated confidence intervals are over optimistic c 2003 elsevier ltd all rights reserved

a high resolution marine palynological record from the central mainland coast of british columbia canada evidence for a mid late holocene dry climate interval abstract sediments collected in a 12 m long core vec02a04 obtained from frederick sound in the seymour belize inlet complex of british columbia were deposited between ca 4540 cal yr bp and ca 1090 cal yr bp in primarily dysoxic conditions the sediments are characterized by alternating intervals of fine grained massive and laminated units laminated sediments consist of light coloured diatom rich layers deposited during summer and dark coloured mineral rich layers deposited during winter laminated sediments are most common in portions of the core deposited between ca 2840 cal yr bp and ca 1820 cal yr bp and correspond to a decline in the relative abundance and pollen accumulation rate of cupressaceae pollen between ca 3190 cal yr bp and ca 2250 cal yr bp the preservation of laminated units and decline of cupressaceae pollen at this time suggest that a drier and possibly cooler climate punctuated otherwise wet and temperate late holocene conditions in the seymour belize inlet complex we correlate the occurrence of the mid late holocene dry climate interval documented in frederick sound to dynamics in the relative position and intensity of the aleutian low pressure system and suggest that climate change associated with dynamics of this semi permanent air mass affected primary productivity and vegetation of the seymour belize inlet complex

allochthonous surface alteration of ni laterites abstract lateritic weathering sections over ultramafic rocks in burma puerto rico venezuela malagasy and brazil display anomalous chemical variations in their upper parts these variations are not due to weathering of ultramafics but to the addition of varying amounts of weathered material from other rocks this contribution can cause a considerable increase in si al ti and zr and decrease in fe cr and ni in the surficial parts of the limonite zone in other occurrences the admixture of foreign material can only be recognized by strongly elevated ti and zr amounts in surface layers which is atypical for ultramafic rocks and their weathering products in most of the occurrences the foreign material was probably transported by colluvial alluvial processes but an eolian derivation is also possible sedimentary processes may cause large amounts of foreign material to be mixed with ni limonite smaller amounts of foreign clayey material can also be washed downwards into clearly autochthonous limonite the ni laterite deposit on the tagaung taung burma which has been explored in detail by drill holes provides an excellent example for the processes discussed above which can also influence the composition of the weathering mantle above other parent rocks

estimation of supraglacial debris thickness using a novel target decomposition on l band polarimetric sar images in the tianshan mountains debris is widely distributed in the ablation zones of mountain glaciers in the tianshan mountains supraglacial debris can accelerate or hamper glacier ablation depending on its thickness thus it plays an important role in the mass balance of debris covered glaciers this paper proposes a novel method to estimate supraglacial debris thickness by using l band polarimetric synthetic aperture radar a new model based target decomposition is used to extract the surface scattering double bounce and volume scattering components the surface scatter model uses the extended bragg scatter which considers the depolarization effect for rough surfaces the volume scatter model uses elliptical scatterers which approximate the shape of the solids in the debris the volume scattering power is related to the dielectric properties of the debris the radar wavelength the incidence angle and the elliptical scatter shape once the target decomposition is performed the debris thickness can be inverted from the volume scattering power and other known parameters through comparison with a large number of field measurements the inversion is shown to be reasonable and the accuracy is validated to be 0 12 m based on the inversion map in the study area the debris thicknesses of the koxkar glacier and its neighboring glaciers are presented and analyzed

a 6000 yr varve record of holocene climate in saanich inlet british columbia from digital sediment colour analysis of odp leg 169s cores abstract high resolution grey value time series were extracted from digital images of varved sediments in saanich inlet british columbia odp sites 1033 and 1034 results allowed reconstruction of a 6000 yr long record with annual resolution composite records were compiled for sites 1033 and 1034 by correlation of massive beds which represent gravity flows and of characteristic features in the varve patterns the varve count age scale was calibrated with published radiocarbon ages results demonstrate that the odp leg 169s record is virtually complete saanich inlet varve record has the potential to provide a high resolution climate record temporal variation in varve thickness is interpreted to reflect regional precipitation history with thick varves representing wet conditions long term changes in varve thickness during the past 6000 yr coincide with known changes in global climate but without an obvious one to one correlation between wet dry in saanich inlet and warm cold periods elsewhere varve thickness indicates that the climate around saanich inlet was wet from the start of the varved sequence at 6000 to 3250 yr bp between 2100 and 1750 yr bp roman warm period and from 500 yr bp onward including during little ice age

evidence for an aeolian origin of the holocene lateritic surface cover of gabon central africa abstract field granulometric and geochemical data are reported for a set of twenty one samples collected at six sites spread over gabon in the extensive lateritic clayey to sandy layer cover horizon which constitutes the upper part of the profiles of surficial formations granulometric analyses show that this material of homogeneous aspect is a mixture of two fractions a clay fraction and a medium to coarse grained sandy fraction relative proportions of these two constituents show strong variations from one site to another but are almost constant from the bottom to the top of a given profile the coarse grained fraction includes lithic elements of local provenance irrespective of their underlying basement the samples display many common geochemical features including a lack of ca na and mg their major element compositions may be accounted by the combination of a discrete number of mineralogical phases namely quartz kaolinite gibbsite fe oxides hydroxides and subordinate k minerals micas the normative contents of aluminous and ferrous phases regularly increase with the weight percent of clays conversely the quartz regularly decreases this inverse relationship is consistent with mixing between an al and fe bearing clay fraction and a coarse grained fraction dominated by quartz correlations between most immobile trace elements and the weight percent of clays indicate a control of those elements by al and fe bearing phases the main exception is for zr and hf as those elements are probably associated with zircons in the coarse fraction because of the control of the trace element distribution by secondary phases the geochemical signatures of all samples are clearly distinct from those of the upper continental crust and any basement rocks thus the trace element characteristics of the cover horizon carry no sign of any source material being the sole consequence of mineralogical sorting prior to deposit from field granulometric and geochemical data an aeolian origin appears as the most probable for the cover horizon geochronological constraints including archaeological data and 14 c dating indicate that this aeolian event took place during the holocene and probably occurred in less than 3000 y additional works will be necessary to assess the global context which made possible this very fast and extended event over large areas of central africa

lithodependence of partly transported weathering horizons above a migmatite diabase contact in central bahia state brazil abstract in the semi arid region of central bahia the weathering cover above a concealed migmatite diabase contact consisting of a loose sandy clayey surface layer and an indurated gravelly laterite shows distinct chemical and mineralogical relationships to the underlying parent rocks high concentrations of fe v mn cu co and ni characterize the weathering material above the diabase in the overlying laterite layer a chemical dispersion of most of these elements towards the migmatite can be observed on the other hand the weathering material above the diabase shows abundance of primary quartz zircon and rutile derived from the migmatite the evolution of the weathering cover is believed to be controlled by colluvial intermixing and vertical homogenization of partly transported weathering material being followed by lateral chemical dispersion during laterite formation thus the weathering horizons obliterate the chemical signal of the parent rocks increasingly from the bottom to the top of the profile similar profiles can be expected in most savannah type regions and therefore their identification is relevant for geochemical exploration

varves in marine sediments a review the global compilation of reported marine varved sedimentary records throughout the quaternary contains 52 sites marine varve deposition and preservation typically depend on environmental and sedimentological conditions such as a sufficiently high sedimentation rate severe depletion of dissolved oxygen in bottom water to exclude bioturbation by macrobenthos and a seasonally varying sedimentary input to yield a recognizable rhythmic varve pattern additional oceanographic factors include the strength and depth range of the oxygen minimum zone omz and regional anthropogenic eutrophication from point sources such as large polluted rivers quaternary marine varves are not only found in those parts of the open ocean that comply with these conditions but also in fjords embayments and estuaries with thermohaline density stratification and nearshore marine lakes with strong hydrologic connections to ocean water this review critically describes settings and sedimentological characteristics of marine sites where varves have been reported broader applications of marine varve records are discussed for example in terms of radiocarbon calibration on high resolution time scales constraining paleoceanographic variability and global change teleconnections diagnosing factors affecting modern fish population dynamics based on past performance detailing biogeochemical cycles and deciphering complex factors influencing marine productivity varves in saline water bodies without hydrologic connection to the global ocean are not included in this review and instead pertain to the companion review on lacustrine varves where also general and fundamental principles of varve deposition classification and dating are covered zolitschka et al 2015 the postulated occurrence of varves in pre quaternary rocks is critically discussed in this review with representative examples in the case of non evaporitic laminations in fine grained ancient marine rocks such as banded iron formations and black shales laminations may not be varves but instead may have multiple alternative origins such as event beds or formation via bottom currents that transport and sort silt sized particles clay floccules and organic mineral aggregates in the form of migrating bedload ripples

hydraulic textural and geochemical characteristics of the ajali formation anambra basin nigeria implication for groundwater quality this study highlights the distribution of hydraulic conductivity k in the regional aquiferous ajali formation of se nigeria on one hand and assesses the possible influences of textural and geochemical characteristics on the hydraulic conductivity on the other hand the investigation approach involved field sampling and collection of 12 sandstone samples from different outcrop locations followed by laboratory studies such as grain size analysis gsa constant head permeameter test and geochemical analysis of major and trace elements using x ray fluorescence method gsa and textural studies show that the sandstones range from fine to medium sands constituting about kbeyer khazen kkozeny carmen kfair hatch with average values of 1 4 10 3 4 4 10 4 3 8 10 4 2 2 10 4 and 8 1 10 5m s respectively these values fall within the range of 10 5 and 10 3m s for fine to medium sands however multivariate factor analysis of the data revealed significant positive dependence of the empirically determined k values on graphic mean grain size and percentage sand content and much less dependence on sorting and total porosity geochemical profiles of the fresh samples are dominated by quartz with corresponding sio2 content of 76 1 98 2 av 89 7 while other major oxides are generally below 1 0wt in the fresh samples however the ferruginized samples exhibited elevated concentrations of al2o3 3 50 11 60wt and fe2o3 1 80 3 60wt which are clear indications of weathering ferruginization processes with attendant trace metal release enrichment 2 5mg l cu 7 5mg l pb 6 5mg l zn 3 9mg l ni and 19 6mg l cr call for concern in respect of the chemical quality of the groundwater system the associated groundwater is generally soft slightly acidic and with low dissolved solids ec 14 134 s cm dominated by silica implying water from clean sandy aquifer devoid of labile and weatherable minerals nonetheless most of the metals with exception of si fe and mn exhibited higher degree of mobility 2 12 folds which can be attributed to reduction of fe mn oxyhydroxides as sinks hosts for trace metals consequently infiltration induced geochemical reactions redox ferruginization and leaching processes signify potential environmental impact in terms of groundwater quality as well as borehole aquifer management especially under humid tropical environment of the study area

holocene environmental and climatic change in the northern great plains as recorded in the geochemistry of sediments in pickerel lake south dakota the sediments in pickerel lake northeastern south dakota provide a continuous record of climatic and environmental change for the last 12000 yr sediments deposited between 12 and 6 ka radiocarbon show extreme variations in composition oxygen and carbon isotopic composition of bulk carbonate carbon isotopic composition of organic matter and magnetic susceptibility these variations re ect changes in sources of moisture regional vegetation types precipitation evaporation balance ground and surface water in ux water residence time erosion lake productivity water level and water temperature the total carbonate content of late pleistocene sediments steadily increased from 20 at the base of the core to as much as 80 in sediments deposited between 11 and 9 ka by about 8 ka the total carbonate content of the sediments had declined to about 40 where it remained with little variation for the past 8 kyr suggesting relatively stable conditions there are marked increases in values of d13c and d18 oi n bulk carbonate and d13c of organic matter in sediments deposited between 10 and 6 ka as evaporation increased and the vegetation in the watershed changed from forest to prairie this shift toward more 18o enriched carbonate may also re ect a change in source or seasonality of precipitation during this early holocene interval the organic carbon oc content of the sediments remained relatively low 2 3 but then increased rapidly to 4 5 between 7 and 6 ka re ecting the rapid transition to a prairie lake the oc content uctuates slightly between 4 and 6 in sediments deposited over the past 6 kyr like oc and total carbonate most variables measured show little variation in the 13 m of sediment deposited over the past 6 kyr particularly when compared with early holocene variations although the magnetic susceptibility of this upper 13 m of sediment is generally low 10 si units the upper six meters of the section is marked by striking 1 m cycles ca 400 500 yr periodicity in susceptibility these cycles are interpreted as being due to variations in the in ux of eolian detrital clastic material century scale cyclic variations in di erent proxy variables for aridity and eolian activity from sediments deposited over the past 2000 yr in other lakes in the northern great plains as well as in sand dune activity suggest that aridity cycles were the dominant feature of late holocene climate of the northern great plains 2000 elsevier

a late archaean palaeoproterozoic 2 6 ga palaeosol on ultramafics in the eastern transvaal south africa abstract this article describes a palaeosol developed on archaean 3 4 ga ultramafics and overlain by sedimentary rocks of the chuniespoort group 2 55 ga the palaeosol is thick mature and complex forming carapaces on palaeohills from base to top it comprises four lithological units 1 carbonated serpentinite 2 black talc rock 3 silcrete dolocrete 4 silcrete breccia in mudstone matrix petrographic and geochemical studies major elements plus v cr ni zn ga y zr nb pge and th indicate that units 1 to 3 represent former saprolites and silicified carbonated saprolites with bedrock textures still preserved unit 4 has been more intensely leached with some admixture of allochthonous sialic material collapse of the original texture and concentration of the immobile elements an irregular ni mineralization in the bottom part of the profiles is described and compared with equivalent modern lateritic deposits a high carbon content suggests the presence of a surficial mat of primitive micro organisms which could have contributed to the stability of the palaeosol on the hilly topography and greatly enhanced the weathering rate the presence of silcrete is indicative of a semi arid climate possibly with alternating wet and dry seasons or of a dry period having succeeded a wet one the absence of fe oxides and the general deficiency of this element in the upper part of the profiles taking into account that the soil was well drained and aerated support the model of an atmospheric o2 level much lower than at present by an order of two magnitudes

southward migration of the intertropical convergence zone through the holocene titanium and iron concentration data from the anoxic cariaco basin off the venezuelan coast can be used to infer variations in the hydrological cycle over northern south america during the past 14 000 years with subdecadal resolution following a dry younger dryas a period of increased precipitation and riverine discharge occurred during the holocene thermal maximum since approximately 5400 years ago a trend toward drier conditions is evident from the data with high amplitude fluctuations and precipitation minima during the time interval 3800 to 2800 years ago and during the little ice age these regional changes in precipitation are best explained by shifts in the mean latitude of the atlantic intertropical convergence zone itcz potentially driven by pacific based climate variability the cariaco basin record exhibits strong correlations with climate records from distant regions including the high latitude northern hemisphere providing evidence for global teleconnections among regional climates

chronology of the palmer deep site antarctic peninsula a holocene palaeoenvironmental reference for the circum antarctic palmer deep sediment cores are used to produce the first high resolution continuous late pleistocene to holocene time series from the antarctic marine system the sedimentary record is dated using accelerator mass spectrometer radiocarbon methods on acid insoluble organic matter and foraminiferal calcite fifty four radiocarbon analyses are utilized in the dating which provides a calibrated timescale back to 13 ka bp reliability of resultant ages on organic matter is assured because duplicates produce a standard deviation from the surface age of less than laboratory error i e 50 years in addition surface organic matter ages at the site are in excellent agreement with living calcite ages at the accepted reservoir age of 1260 years for the antarctic peninsula spectral analyses of the magnetic susceptibility record against the age model reveal unusually strong periodicity in the 400 200 and 50 70 year frequency bands similar to other high resolution records from the holocene but so far unique f

interannual to multidecadal timescale climate variations in the northeast pacific abstract analysis of five long term coastal air temperature records reconstructed from tree ring growth patterns indicate that the climate of the northeast pacific ocean has oscillated at three dominant timescales over the last 400 years the well known 2 8 yr el nino southern oscillation enso timescale a 20 40 yr interdecadal timescale and a 60 80 yr multidecadal timescale the latter oscillation has been the dominant mode of air temperature variability along the west coast of north america over the last 400 years during this period there have been conspicuous temporal modulations of the enso and the interdecadal signals low frequency temperature oscillations at periods greater than 10 years in the northeast pacific have been significantly coherent and in phase from southern california to british columbia however with the exception of the enso signal higher frequency variability has been weakly coherent along the west coast recent work suggests that the interdecadal oscillation is a worldwi

the impact of air mass circulation dynamics on late holocene paleoclimate in northwestern north america paleoclimate records from northern british columbia southwestern yukon and adjacent alaska suggest that late holocene climate may have been influenced by specific air mass circulation dynamics the aleutian lowpressure index alpi is a measure of sea level pressure fluctuations in the pacific northwest associated with the aleutian low al pressure system in this study we show that the al has a strong influence on historical climate change in the study area and explore the relationships between alpi polarity and changes in late holocene paleoclimate records analyses of weather station data in the study area indicate positive correlations r 0 63 between mean wintertime december march temperature and alpi values total wintertime snowfall accumulation and total precipitation show moderate and weak negative correlations respectively a late holocene increase in exotic western hemlock tsuga heterophylla pollen has been observed in regional paleoclimate studies a sustained positive alpi phase during the late holocene is considered as a causative mechanism under such conditions warm maritime air masses would more frequently penetrate inland potentially resulting in eastward pollen transfer enhanced growing conditions at coastal sites and an increase eastwards in the range limit of these species this study indicates that apparent conflicts in the timing and magnitude of late holocene climate change may be the result of a strong regional climate forcing mechanism that exhibits both temporal and geographical variation r 2002 elsevier science ltd and inqua all rights reserved