silica diagenesis in eocene shallow water platform carbonates southern pyrenees spectacularly developed lower eocene chert in the corones platform carbonates of the spanish pyrenees is concentrated within a restricted brackish water laminated ostracod rich facies which also contains abundant sponge spicules the chert occurs as nodular bedded and mottled varieties and four petrographic types of quartz are developed microquartz length fast lf chalcedony megaquartz and microspheres 18o values of chert range from 29 6 to 30 9 smow which correspond to a broad isotope rank common for biogenic and diagenetic replacement cherts calcian dolomite crystals with high fe and na are disseminated within the microquartz and lf chalcedony but are absent from the megaquartz and host carbonate the chert is closely associated with desiccation cracks and with interstratal dewatering structures load casts are silicified and laminae rich in sponge spicules are convoluted early cracks related to dewatering are filled by microquartz and quartz cements ostracod shells within chert are locally fractured those in the host carbonate are commonly flattened late fractures are filled by lf chalcedony and megaquartz there is much evidence for the dissolution of sponge spicules and their calcitization in the carbonate host rock silica for the corones cherts was derived from sponges during early diagenesis and shallow burial early mechanical compaction and sediment dewatering played a major role in sponge spicule dissolution migration of silica rich fluids and the consequent precipitation of chert quartz cements continued to be precipitated into the burial environment

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

quantitative high resolution winter jja precipitation reconstruction from varved sediments of lago plomo 47 s patagonian andes ad 1530 2002 high resolution climate reconstructions from a range of natural archives across the world are fundamental to place current climate change into perspective paleoclimate records for the southern hemisphere are scarce and only a few quantitative high resolution reconstructions exist for the past millennium we present a record of annually laminated sediments of lago plomo 46 59 s 72 52 w 203 m a s l located east of the northern patagonian ice field npi radiometric dating 210pb 137cs 14c ams is consistent with counts of millimetre scale laminae confirming the annual nature of the laminae couplets with a light summer and a dark winter layer the varves were analyzed for thickness mass accumulation rate mar scanning x ray fluorescence xrf and scanning reflectance spectroscopy in the visible range vis rs mar data were calibrated against austral winter jja precipitation data cru ts 3 0 for the period ad 1930 2002 r 0 67 p aut 0 05 using a linear inverse regression model we reconstructed winter precipitation for lago plomo back to ad 1530 the root mean squared error of prediction rmsep is small 13 3 mm month 12 of the average precipitation compared with the pronounced decadal and multidecadal variability suggesting that most of the reconstructed variability is significant wetter phases reference ad 1930 2002 were observed around ad 1600 ad 1630 1690 and ad 1780 1850 and a prolonged drier period ad 1690 1780 with a multidecadal minimum centered on ad 1770 the spatial correlation for south america suggests that the jja precipitation record from lago plomo is representative for large areas in the southwest between c 41 s and 51 s

crystallographic and structural transformations of sedimentary chalcedony in flint upon heat treatment the early occurrence of intentional heat treatment of silica rocks has recently become a key element in the discussion about the cultural modernity of prehistoric populations lithic vestiges are the only sources that remain of this process and the understanding of the material s properties and transformations are essential for reconstructing the conditions and parameters applied during heat treatment several models of the structural transformations upon heating have been proposed in the current literature these models are often contradictory and do not account for the most recent structural and mineralogical data on chalcedony in order to propose a new model we elaborated an experimental procedure and applied different techniques involving infrared spectroscopy solid state nmr x ray diffraction and electron microscopy the results show that the major transformation to happen is the loss of silanole sioh and the creation of new si o si bonds according to the reaction si oh ho si si o si h2o this reaction starts between 200 degrees c and 300 degrees c and causes an increase in the hardness of the rocks the maximal annealing temperature and the ramp rate are the functions of the ability of the structure to evacuate newly created h2o and depend on the size of the specimen and the volume of its porosity these results also show that the annealing duration at maximum temperature can be relatively short 50 min for a sufficiently large amount of transformation to be accomplished

raw material quality and oldowan hominin toolstone preferences evidence from kanjera south kenya the role of raw material quality in oldowan technology has not been fully explored there are numerous studies suggesting oldowan hominins preferred certain types of stone for artifact manufacture previous studies of the artifact assemblage from the early pliocene oldowan locality of kanjera south south rachuonyo district kenya show that raw material selection and transport was an important aspect of late pliocene hominin adaptations yet the exact properties of stones that hominins were selecting remain enigmatic two potentially important features of artifact raw material are durability and fracture predictability we investigate fracture predictability through mechanical tests of stone and investigations of the affect of stone properties on fracture patterns in archaeological collections we investigate stone durability with actualistic studies of edge attrition combined with further mechanical tests of various lithologies oldowan hominins at kanjera appear to have selected raw materials based on their durability the ability for a stone to fracture consistently does not appear to be as important in hominin toolstone preference as previously assumed hominins that produced the assemblages at kanjera south appear to have incorporated an extensive understanding of various attributes of raw material in the transport and production of stone artifacts when combined with previous research on the transport patterns at kanjera the results of this study provide evidence for a more complex raw material acquisition strategy than has previously been suggested for late pliocene oldowan hominins

middle oxfordian lower kimmeridgian chert nodules in the holy cross mountains south central poland abstract this report presents the results of field and laboratory micropaleontologic petrographic mineralogical chemical and isotopic study of middle oxfordian lower kimmeridgian chert nodules from the holy cross mountains south central poland the chert host facies represent low energy environments characteristic of changing basinal depths with subordinate influxes of coated carbonate grains derived from a prograding platform the optical microscopic and sem studies indicate that the chert nodules consist of cryptocrystalline quartz with subordinate microcrystalline quartz fills and lf chalcedony sponge spicules no opal a and opal ct precursors of the crypto and microquartz have been found these cherts formed as a result of an episodic influx of sio 2 rich fluids and multistage processes of direct precipitation of cryptoquartz dissolution etching reprecipitation cementation and recrystallisation of sponge spicules composed of metastable amorphous opal a of the different genetic models of chert formation the sea floor hydrothermal activity linked to the mid polish rift and extentional tectonics in the carpathian area seems to be a possible hypothesis

a distributed temperature index ice and snowmelt model including potential direct solar radiation hourly melt and discharge of storglaciaren a small glacier in sweden were computed for two melt seasons applying temperature index methods to a 30 m resolution grid for the melt component the classical degree day method yielded a good simulation of the seasonal patient of discharge but the pronounced melt induced daily discharge cycles were not captured modelled degree day factors calculated for every hour and each gridcell from melt obtained from a distributed energy balance model varied substantially both diurnally and spatially a new distributed temperature index model is suggested attempting to capture both the pronounced diurnal melt cycles and the spatial variations in melt due to the effects of surrounding topography this is accomplished by including a radiation index in terms of potential clear sky direct solar radiation and thus without the need for other data besides air temperature this approach improved considerably the simulation of diurnal discharge fluctuations and yielded a more realistic spatial distribution of melt rates the incorporation of measured global radiation to account for the reduction in direct solar radiation due to cloudiness did not lead to additional improvement in model performance

periglacial cirque analogs elevation trends of cryoplanation terraces in eastern beringia abstract cryoplanation terraces are large erosional landforms common in cold unglaciated mountainous environments terrace sequences are composed of alternating slope segments with gently sloping treads and steep rubble covered risers and culminate in extensive summit flats many unglaciated upland landscapes in eastern beringia are dominated by these landforms indirect evidence indicates that they evolve through locally intensified weathering and mass movement processes associated with late lying snowcover geospatial analysis involving nearly 700 cryoplanation terraces in eastern beringia demonstrates that their elevation rises from 175 to 350 masl on bering sea islands to median values 1200 m near the alaska canada border the regional trends of cryoplanation terrace elevation are nearly identical to those of wisconsinan cirques on several transects across alaska the consistency in the elevation trends of glacial cirques and cryoplanation terraces indicates close genetic links between the two classes of feature involving topographic position continentality gradients and the mass balance of localized snow accumulations cryoplanation terraces can be considered the periglacial analogs of glacial cirques and have greater potential as sources of paleoclimatic information than smaller periglacial features more sensitive to short term climate variations process oriented studies age determinations and high resolution mapping are needed before the paleoenvironmental potential of these landforms can be realized fully

glacier meltwater and runoff modelling keqicar baqi glacier southwestern tien shan china meltwater and runoff from keqicar baqi glacier a large glacier in the southwestern tien shan northwestern china are simulated using a modified degree day model including potential clear sky direct solar radiation coupled with a linear reservoir model for the period 1 july to 12 september 2003 there is good agreement between modelled and measured meltwater at ablation stakes and between simulated and observed runoff at the glacier terminus a reconstruction of glacier meltwater and runoff from an assumed debris free surface during the study period shows that the effect of the debris layer on glacier meltwater generation crucially affects glacier runoff the model is also used to calculate glacier runoff given the climate scenario resulting from a doubling of co2 as projected by the recm2 regional climate model the projected changes in temperature and precipitation vary from 0 to 2 78c and from 0 to 25 respectively results indicate that glacier runoff increases linearly with temperature over these ranges whether or not the debris layer is taken into consideration the effect of change in temperature is much more noticeable than that for change in precipitation due to the debris layer predominantly covering and insulating the ablation area the response of glacier runoff is less sensitive to temperature increase with a debris covered surface than with a debris free surface glacier runoff is also markedly reduced when a reduced glacier area is prescribed in the 2 78c scenario

archaeomagnetism of burnt cherts and hearths from middle palaeolithic amud cave israel tools for reconstructing site formation processes and occupation history abstract apart from magnetostratigraphy archaeomagnetism is rarely used in middle and late pleistocene sites here we present detailed palaeomagnetic analyses of cemented hearths and burnt chert items from amud cave israel 68 55 ka two types of materials common in levantine middle palaeolithic cave sites both materials are shown to be recorders of the geomagnetic field and were used to reconstruct either the ancient field direction for cemented hearths or intensity palaeointensity for chert at the time of the last burning or shortly after we test the utility of palaeomagnetic data to further our understanding of temporal aspects of occupations in the cave by comparing the dispersion of the palaeomagnetic data to the known characteristics of geomagnetic secular variation in the holocene we show that divergent palaeointensities can help identify diachronic burning events suggesting different activity patterns in two areas of the cave additionally we used palaeomagnetic directional vectors to distinguish between a well preserved hearth and one that had been mixed prior to cementation using rock magnetic investigations we demonstrate that magnetic methods can be used as a relatively fast and inexpensive method to identify burning of cherts in antiquity above 500 c the palaeomagnetic results are in agreement with results of previous studies at amud cave obtained by other independent methods this study shows that palaeomagnetic methods can serve as a powerful tool in the study of palaeolithic sites

silica diagenesis ii general mechanisms abstract amorphous silica phases opal a precipitate in nature due to the formation of dense colloids in supersaturated alkaline aqueous solutions with low relative concentrations of other ions opal a dissolves and yields solutions of still relatively high silica content in pore waters containing abundant cations open framework polymers form which flocculate to yield opal ct opal ct becomes increasingly ordered primarily due to preferential growth of cristobalite relative to tridymite and crystal size increase opal ct dissolves to yield pore waters of low silica concentration which allows slow growth of quartz crystals from monomeric solution the quartz crystals then slowly increase in size and crystallinity carbonates appear to enhance opal ct formation possibly due to the activity of positively charged hydroxyl complexes hence polymerization in relatively pure systems is involved in opal a formation and polymerization in impure systems is involved in opal ct formation and slow growth from monomeric low silica concentration solutions is involved in precipitation of quartz in sedimentary realms

cosmogenic nuclides and the dating of lateglacial and early holocene glacier variations the alpine perspective abstract based on cosmogenic 10 be data from four sites in the alps we discuss geological uncertainties associated with the dating of former cirque and small valley glacier margins at the early lateglacial gschnitz site trins austria a 3000 yr spread in 10 be exposure ages points to prolonged boulder instability three out of seven ages are not included in the mean age calculation which yielded 15 400 1000 yr indistinguishable from the oldest boulder age of 16 130 1040 yr as a result of the distinctive morphology at julier pass switzerland site we are able to exposure date the early 12 300 1300 yr and the late 11 300 600 yr egesen stadial glacier advances younger dryas equivalent not just final retreat at the kromer site austria 10 be exposure ages from five clast supported boulders are indistinguishable within the analytical uncertainties mean age 8400 500 yr in addition to moraine age key factors that may lead to too young ages include degree of matrix vs clast support of the boulders post depositional periglacial activity and tree coverage at the nagelisgratli bedrock site near grimsel pass switzerland exposure ages of 10 760 11 720 yr are consistent with early holocene cirque glacier retreat and underline the marked lack of nuclide inheritance in bedrock exposures in the alps

heat treatment in the south african middle stone age temperature induced transformations of silcrete and their technological implications abstract it was recently found that silcrete raw material was heat treated during the south african middle stone age msa for altering its flaking properties this finding led to hypotheses about the implications for the msa hunter gatherers such as the cost of thermal treatment in terms of investment and firewood to date these hypotheses lack a solid basis for data on the thermal transformations of south african silcrete and hence the necessary heating procedure and heating environment is missing in order to produce such data we conducted an experimental study within the framework of the diepkloof project this work is based on the petrographic mineralogical and structural analysis of south african silcrete from the west coast and its thermal transformations our results shed light on the nature of these transformations the ideal heating temperatures and the tolerated heating speed the processes occurring in silcrete are comparable to flint i e the loss of chemically bound water and the formation of new si o si bonds but their intensity is less pronounced effective heating temperatures are significantly higher than for flint and the heating speed tolerated by south african silcrete is relatively fast these findings imply that silcrete heat treatment cannot be directly compared with flint heat treatment unlike flint heating silcrete does not require the setup of a dedicated heating environment and may have been performed in the same time as other fire related activities this would represent only a minor supplementary investment in time and firewood these results have broad implications for the discussion about technological evolution and the acquisition of specialised knowledge in the msa

sandstone chert and laminated chert black shale couplets cretaceous uhangri formation southwest korea depositional events in alkaline lake environments abstract the cretaceous uhangri formation southwest korea is a lacustrine sequence surrounded by acidic volcanic terrain and comprises sandstone chert and laminated chert black shale couplets in the upper part in both cases the uhangri chert is composed mainly of sio 2 74 81 al 2 o 3 10 12 and k 2 o 6 7 its impure nature is largely due to the presence of feldspar grains and clays within a microcrystalline quartz matrix the uhangri chert is characterized by common soft sediment deformation in situ brecciation slumping and no organic traces which collectively indicate its inorganic origin the sandstone chert couplets are alternations of massive graded crudely stratified rippled or ripple cross laminated sandstone layers and generally homogeneous chert layers the laminated chert black shale couplets consist of alternating light and dark coloured laminae of chert and overlying black shale these couplets were most likely deposited by episodic riverine inflows into a silica rich alkaline lake the freshwater input could trigger direct inorganic silica precipitation through an abrupt decrease in lake water ph the sandstone chert couplets would be deposited by high density underflows whereas the laminated chert black shale couplets by fine sediment dominant overflows

lithic economy and territory of epipaleolithic hunter gatherers in the middle tagus the case of pena d agua portugal abstract in central portugal westernmost eurasia the transition from the traditional pleistocene hunter gatherer societies to the complex mesolithic societies of the holocene has been debated for decades while some argue that these differences were a progressive phenomenon that started with the shift from the pleistocene to the holocene others defend that the late pleistocene patterns were fairly similar to those of the epipaleolithic and that the major shift was rapid dramatic and triggered by the necessary adaptation to the 8 2 ka cal bp 8 09 8 25 ka cal bp climatic event the study of lithic raw material provenance might be useful for this discussion since it has been suggested that the magdalenian and epipaleolithic populations from this region were collecting this resources within a close range territory whereas the mesolithic populations were acquiring them at longer distances in this paper we present the results from p xrf vp sem eds and xrd analysis done on the epipaleolithic lithic assemblage from pena d agua rockshelter and in some geological samples from secondary sources located 14 km from this site this layer is of major relevance for this debate since it is dated from 8 19 ka cal bp if the transition was gradual it would be expected that this assemblage would show some traits of higher complexity seen in the mesolithic namely of longer distance acquisition however our results indicate correspondence between the archaeological chert types and some of the geological sources the differences seen between the archaeological specimens and geological samples are mostly present in traits that can be related with manufacture handling and post depositional phenomena the results suggest that in what concerns to the economy of abiotic resources the epipaleolithic populations living at the time of the dramatic 8 2 ka cal bp cold event were performing a short range acquisition of lithic raw materials which reinforces the idea of continuity from the late pleistocene to the 8 2 ka cal bp event and an abrupt and dramatic shift soon after this phenomena

an experimental assessment of the influences on edge damage to lithic artifacts a consideration of edge angle substrate grain size raw material properties and exposed face functional analyses of stone tool assemblages face a number of methodological challenges aside from determining specific uses it can be difficult to know which artifacts in an assemblage were used at all typically retouch is taken as a proxy for indicating past use but ignoring unretouched flakes means excluding the overwhelming majority of most assemblages assessing whether an unretouched flake has been used is complicated edge damage on flakes can be caused by use or by taphonomic processes one of the more important of these processes is trampling experiments have shown that trampling can create damage mimicking retouch and unlike some other taphonomic processes trampling is otherwise difficult to detect one possible solution is to look for patterning in the placement left vs right ventral vs dorsal proximal vs distal of edge damage and recent studies using gis based approaches have shown the utility of this method at an assemblage level here we trampled a set of experimental flakes made from two raw materials on two substrate types and analyzed the edge damage patterns using a newly developed image analysis program that is similar to previous gis based approaches we found that a previously unquantified variable edge angle is strongly correlated with the likelihood of damage thus in circumstances where edge angles are non randomly distributed across flake types trampling damage will be patterned these results have implications for previously published edge damage studies and further indicate that basic flake mechanics need to be considered in studies where function is inferred from edge damage patterns approaches to the archaeological record that employs assemblage level assessments of edge damage must consider a range of factors when inferring behaviors from these patterns

a 2000 year record of solar forcing on varved lake sediment in eastern finland abstract a high resolution study was performed on varved sediments from lake lehmilampi in eastern finland varve data was collected by digital image analysis using standard 1 8 mm thick samples impregnated in epoxy and x rayed climatic variability is imprinted on varve properties varve thickness and accumulation of mineral and organic matter during the last 2000 years the cumulative counting error of the varve record is estimated as 2 3 qualitative comparison of varve parameters and residual 14c constructed from tree rings revealed close correspondence between the two records suggesting solar forcing on lake sedimentation classical climatic periods of the last millennia medieval climate anomaly 1060 1280 in the varve record and little ice age cooler phases culminating in 1340 1465 1545 1680 1850 and also in 1930 in the varve record are clearly evident in the varve record at present the physical link between solar activity levels and lake sedimentation has not been established

effect of heat treatment on siliceous rocks used in prehistoric lithic technology stone tool manufacture by many prehistoric and recent societies was characterized by deliberate heating of fine grained siliceous rocks to improve their flaking properties extensive mechanical testing of heated and unheated cryptocrystalline and macrocrystalline quartz lithologies has shown that thermal treatment causes a consistent marked reduction in fracture toughness this mechanical property can be used as an objective measurement of the flaking qualities of stone materials and a reliable criterion for the recognition of intentionally heated artefacts in the archaeological record x ray diffraction studies and scanning electron microscopy have demonstrated that the change in fracture toughness with heating is the result of recrystallization the poorly ordered strongly interlocking cryptocrystalline fabric of the unheated samples becomes more equigranular and better crystallized with thermal treatment as a consequence fractures propagate more readily in heated samples accounting for their better flaking properties

origin of spheroidal chert nodules drunka formation lower eocene egypt chert nodules of the drunka formation lower eocene are mostly spherical have diameters from 40 to 120 cm are quasi uniformly spaced 2 3 m apart in the plane of bedding have concentric internal structure and except for rare small 6 cm solid chert nodules are less than 85 chertified nodules formed after moderate alteration of limestone by meteoric water 18ocalcite 4 to 8 at shallow 100 m burial depths more extensive alteration of limestone 18o 10 to 16 by meteoric water followed nodule growth chertification was by low temperature meteoric water 18oquartz 18 in margins to 22 in nuclei at shallow burial depths meteoric water may have invaded the drunka formation in association with shelf progradation during the early eocene or during the development of a middle eocene unconformity replacement of carbonate mud by microcrystalline quartz was the dominant chertification process but fossils were replaced in part by fine grained equant megaquartz quartzine and chalcedony the last of these occurs in places as beekite opal a secreting marine organisms are the inferred source of silica but none are preserved there is no compelling evidence of an opal ct precursor so quartz may have formed by direct precipitation self organization processes of enigmatic character established the spacing pattern of the nodules and also the liesegang banded internal structure of the chert nodules nodules grew chiefly by diffusive supply of silica although one locality has elongate nodules that grew when there was some porewater advection chertification patterns and 18o values of both calcite and quartz indicate that nodule growth was complex and variable some nodules probably grew from the centre outwards many nodules however initially grew simultaneously across the entire nodule but late stage growth was predominantly at the outer margins or at selective internal sites

modern spectral climate patterns in rhythmically deposited argillites of the gowganda formation early proterozoic southern ontario canada abstract rhythmically deposited argillites of the gowganda formation ca 2 0 2 5 ga probably formed in a glacial setting drop stones and layered sedimentary couplets in the rock presumably indicate formation in a lacustrine environment with repeating freeze thaw cycles it is plausible that temporal variations in the thickness of sedimentary layers are related to interannual climatic variability e g average seasonal temperature could have influenced melting and the amount of sediment source material carried to the lake a sequence of layer couplet thickness measurements was made from high resolution digitized photographs taken at an outcrop in southern ontario canada the frequency spectrum of thickness measurements displays patterns that resemble some aspects of modern climate coherent periodic modes in the thickness spectrum appear at 9 9 10 7 layer couplets and at 14 3 layer couplets it is unlikely that these coherent modes result from random processes modern instrument records of regional temperature and rainfall display similar spectral patterns with some datasets showing significant modes near 14 yr in both parameters rainfall and temperature could have affected sedimentary layering in the gowganda argillite sequence and climate modulation of couplet thickness emerges as the most likely explanation of the observed layering pattern if this interpretation is correct the layer couplets represent predominantly annual accumulations of sediment i e they are varves and the thickness spectrum provides a glimpse of early proterozoic climatic variability the presence of interannual climate patterns is not unanticipated but field evidence presented here may be of some value in developing a climate theory for the early proterozoic

detecting heat treatment on silcrete experiments with methods abstract we describe experiments aimed at detecting heat treatment of silcrete a siliceous rock of inhomogeneous lithology widely used in prehistoric australia our samples n 66 come from eastern new south wales two methods widely used on other materials are found to be inadequate scanning electron microscope sem analyses allow conflicting interpretations of the same piece of material while colour changes are too variable to be a reliable indicator two other methods are more reliable increase in lustre is rare but clearly indicates heat treatment when its thermal origin is certain palaeomagnetism assessments of modern n 18 and archaeological n 23 samples show that while the method does not give false positives it indicates heating and not necessarily heat treatment a combination of palaeomagnetism and lustre assessments is recommended

a record of climate over the last millennium based on varved lake sediments from the canadian high arctic a varved sediment record that extends back over the last millennium was recovered from lower murray lake northern ellesmere island nunavut canada 81 20 n 69 30 w flatbed scan images and back scattered electron images were analysed to provide varve thickness and other quantitative sedimentary indices on an annual basis in many studies of lakes from the high arctic varve thickness is a good proxy for summer temperature and we interpret the lower murray lake varves in this way on that basis the lower murray lake varve thickness record suggests that summer temperatures in recent decades were among the warmest of the last millennium comparable with conditions that last occurred in the early twelfth and late thirteenth centuries but estimates based on the sediment accumulation rate do not show such a recent increase the coldest conditions of the little ice age were experienced from ad 1700 to the mid nineteenth century when extensive ice cover on the lake led to widespread anoxic conditions in the deepest parts of the lake basin an overall decline in median grain size over the last 1000 years indicates a reduction in the energy available to transport sediment to the lake many of these features of the record are also observed in other palaeoclimatic records from the north american arctic the very recent appearance of the diatom campylodiscus which was not observed through out the record of the last millennium suggests that a new threshold in the ontogenetic development of the lake has now been passed

suspended sediment from the gangotri glacier quantification variability and associations with discharge and air temperature abstract to understand the sediment delivery variation for a himalayan glacier gangotri glacier garhwal himalayas and to determine its relationship with discharge and air temperature suspended sediment samples and discharge data were collected near the glacier snout 4000 m for four melt seasons during the period 2000 2003 these data were used to estimate suspended sediment concentration ssc suspended sediment load ssl sediment yield and erosion rate in the glacier melt stream bhagirathi the monthly distribution of suspended sediment and its variability from year to year have been examined mean monthly ssc for may june july august september and october were found to be 1942 2063 3658 2551 734 and 136 mg l 1 respectively maximum ssc in meltwater was observed in july followed by august it was found that the cumulative percentage delivery of ssc precedes discharge throughout the melt season mean monthly total ssl for may june july august september and october during the study period was found to be 149 423 1220 746 143 and 5 10 3 ton respectively the strong variability is found in ssl c v 1 1 than ssc c v 0 8 because computation of ssl includes both discharge c v 0 6 and ssc delivery response of ssl in terms of percentage of total load is less in the early part of the melt season than in the later stage in comparison to that of discharge this may be due to the fact that in the beginning of the melt season low melt rate conditions prevails and thus the low discharge velocity could not flush out stored glacial sediment it has been observed that 59 64 of the sediment passed through the channel by the time 50 of the total discharge passed the average suspended sediment yield for the whole melt season from the study area was estimated to be about 4834 ton km 2 and corresponding erosion rate was 1 8 mm the relationship between mean monthly ssc and discharge r 2 0 99 is much better than the daily ssc and discharge r 2 0 40 because variability of both parameters is averaged out on monthly scale mean monthly ssc and mean monthly ssl provide a good exponential relationship with mean monthly air temperature these results are relevant for planning and management of water resources in the high altitude areas and for designing hydropower projects

too young or too old evaluating cosmogenic exposure dating based on an analysis of compiled boulder exposure ages cosmogenic exposure dating has greatly enhanced our ability to define glacial chronologies spanning several global cold periods and glacial boulder exposure ages are now routinely used to constrai

the black layer of middle palaeolithic combustion structures interpretation and archaeostratigraphic implications certain aspects of the formation processes of simple flat archaeological combustion structures such as those present in the middle palaeolithic record remain unexplained such kind of combustion structures are commonly affected by postdepositional agents and often their only distinct well preserved component is a thin black lens on the ground hence understanding the nature of this black lens is essential towards archaeological interpretation from an interdisciplinary microstratigraphic approach we present a case study in which for an entire experimental series of flat combustion structures the black layer represents the fire altered topsoil on which the fire was made parallel analysis of archaeological middle palaeolithic combustion structures from the site of el salt alicante spain reveal similar patterns leading to significant implications for archaeological interpretation in the light of these results special attention must be paid to the formation processes of flat middle palaeolithic combustion features as black layers and the material contained in them are not necessarily linked with combustion but with preceding activities or events in such cases black layers represent intact remnants of occupation surfaces concealing significant behavioural and palaeoenvironmental information relevant to the reconstruction of middle palaeolithic societies

a millennial long record of warm season precipitation and flood frequency for the north western alps inferred from varved lake sediments implications for the future abstract the recent warming of the global climate is well recognized however does a warmer climate also mean a moister climate does dry get drier and wet get wetter there are important questions as they relate to changes in the water cycle and impacts the water resources as well as the frequency and intensity of storms and floods in the near future in europe regional climate models do not show consistent and robust results for future hydroclimatic changes and how extreme events will evolve in response to future climate change paleo hydroclimatic data from natural archives are one of the few means to assess such changes in the longer context here we present an annually resolved record of warm season mjja precipitation and summer flood frequency from the varved annually laminated sediments of proglacial lake oeschinen 46 30 n 7 44 e 1580 m nw swiss alps back to ad 884 these data sets are inferred from the thickness of annual sediment deposits and the occurrence of flood event layers in the sediments the chronology of the sediment record is based on multiple varve counts and validated with historical floods chronicled in written documents back to the 14th century and 14c ams dates the precipitation record shows pronounced interannual to centennial variability with humid warm season phases between ad 920 950 ad 1100 1180 ad 1300 1400 ad 1590 1650 ad 1700 1790 ad 1820 1880 and ad 1960 2008 driest conditions are reconstructed for ad 960 1080 ad 1250 1300 and for ad 1880 1900 our precipitation record is consistent with the few multi centennial warm season precipitation records available for europe we did not find a persistent relationship between warm season precipitation and temperature in contrast results show that the relation between precipitation and temperature has oscillated between positive correlations warmer gets wetter cooler gets drier and negative correlations warmer gets drier cooler gets wetter with a highly significant 2 99 multidecadal 60 70 yrs periodicity over the last millennium possible explanations for this phenomenon are changes in the weather type statistics or the within weather type variability which influence the combinations between precipitation and temperature over continental central europe and operate at multidecadal scales such multidecadal effects might also be important for precipitation scenarios in the alpine area under future warming our record of flood frequency suggests more frequent floods under cool and humid climate during the warm seasons this picture is consistent with other studies from small and medium size catchments at mid and high elevations in the alpine area however the 13th century reveals a period with high flood frequency during warm and moderately dry average precipitation conditions this anomalous situation is currently not understood nonetheless this is also one out of several possible scenarios for the future from the different combinations found in our record we conclude that the relation between floods precipitation and temperature and in consequence future projections remain poorly constrained

precipitation of silica and formation of chert mudstone peat association in miocene coastal environments at the opening of the sea of japan abstract a sedimentary sequence of layered chert alternating with mudstone and associated peat is present at yachi japan these deposits were accumulated in a local lacustrine to brackish water environment along a coastal setting during the early to middle miocene the basement of the sedimentary sequence is rhyolite erupted just before the chert precipitation and its weathered derivatives the chert and the mudstone lack coarse detrital grains on the other hand associated peat contains abundant plant leaves and debris that are compressed and deformed post depositionally uncompressed leaf fragments and broken twiggy trunks in the chert suggest rapid chert precipitation and early lithification four quartz fabrics are recognized chalcedony microquartz megaquartz and euhedral quartz these types vary from colorless to pale brown microscopic sem and xrd observations reveal a paragenetic sequence of silica crystallization chalcedony microquartz and megaquartz was precipitated and consolidated rapidly then euhedral quartz was crystallized in voids there is neither evidence indicating opal a and opal ct precursors of these quartz nor evidence showing that the chert is a post depositional silicification product of volcanic ashes petrographic observation indicates that the initial silica mineral phase was quartz and chalcedony silica was interpreted to have precipitated as a result of influx of low ph water and mixing with silica concentrated solution in the coastal depressions the petrography and depositional environment of the chert are compared with those of other chert types the chert mudstone peat association found at the yachi seems to represent brackish water sediments deposited during continental rifting of the sea of japan type

cosmogenic exposure dating of late pleistocene moraine stabilization in alaska seventy three new 1 0 be 2 6 al ages from 57 moraine boulders and 2 tors together with 43 previously published cosmogenic exposure ages from 41 moraine boulders allow us to critique the use of cosmogenic exposure ce dating of moraine boulders in alaska boulder exhumation during moraine degradation likely gives rise to the largest uncertainty in constraining the timing of initial moraine stabilization following ice retreat isotopic inheritance appears to be most important for moraines deposited close to their cirque headwalls boulder surface bedrock erosion rate can be roughly constrained and leads to a range in moraine stabilization ages snow cover history is difficult to constrain but its effect is thought to be minor for the tall boulders sampled despite these complications the ce ages provide important new information regarding the timing of the last and penultimate glaciations in alaska three penultimate moraines yielded ce ages that overlap with marine isotope stage mis 4 early mis 3 45 65 ka rather than mis 6 ca 140 ka based on a combination of our new ce chronologies and existing 1 4 c ages from six study areas glaciers retreated from their local late wisconsin maxima ca 24 27 ka kokrines hills west interior alaska ca 24 26 ka northeastern brooks range ne alaska ca 21 23 ka yukon tanana upland east interior alaska ca 22 ka ahklun mountains sw alaska ca 20 ka western alaska range central alaska ca 16 18 ka chuilnuk mountains sw alaska overall glacier retreat was concurrent with the peak of the last global glacial maximum probably in response to limited moisture availability

antiphase hydrogen and oxygen isotope periodicity in chert nodules abstract oxygen and hydrogen isotope analyses were made of jurassic age chert nodules from the holy cross mountains se poland along radial transects at high spatial resolution there is a radial sigmoidal periodicity for both isotope ratios but the two are out of phase with high d values corresponding to low 18 o values periodicity for a 100 to 120 mm diameter nodule is approximately 16 mm increasing slightly toward the rim with amplitudes approaching 20 and 3 0 for hydrogen and oxygen respectively the combined hydrogen oxygen isotope data for one nodule fall on a published curve for chert forming in equilibrium with seawater knauth and epstein 1976 the range of delta values corresponds to temperature variations of 10 c data for a second chert fall on a subparallel d 18 o line with d values that are almost 50 lower the d 18 o patterns for the nodules cannot be explained by periodic mixing of meteoric and ocean water because the hydrogen and oxygen isotope data are out of phase two possible explanations for the antiphase periodicity are a cyclical temperature variations perhaps related to an unstable convection system e g bolton et al 1999 and b self organizing catalytic precipitation e g wang and merino 1990 the systematic isotopic variations are difficult to explain by diagenesis and strongly suggest that primary isotopic compositions are preserved the isotopic data provide important information on the thermal history of the sedimentary basin if temperature variations are the cause of the isotopic periodicity

enhanced boulder weathering under late lying snowpatches a schmidt test hammer was employed to assess the aggregate surface hardness of samples of boulders dug out from under late lying snowpatches at sites in switzerland scotland and norway the results were compared with an equivalent set of readings made on boulders at nearby snow free control sites the results in every case reveal that the aggregate surface hardness of boulders buried by late lying snow is significantly less at the 0 001 level than that of boulders at the corresponding control sites this result indicates that late lying snow significantly enhances rock weathering probably because boulder and rock surfaces are exposed to prolonged wetting by percolating meltwater under late lying snowbeds

first evidence of heat treatment during the early neolithic in northeastern italy the site of la vela sector vii trentino alto adige italy provides one of the few complete stratigraphic sequences ranging from the mesolithic to the middle neolithic in northwestern italy the site is located in the adige valley a way of communication between the po plan and the alps this research focuses on the early neolithic lithics ascribable to the gaban facies dated to 5000 4700 cal bc different rocks coming from local exposures have been exploited the goal of the reduction sequence was the production of blades by pressure knapping technique the technological study of the assemblage raised a particular interest for the presence of flint artifacts suggesting the usage of controlled heat treatment the presence of this technique has been tested by an experimental approach based on fourier transform infrared ft ir spectroscopy complementary microstructural and analytical characterizations with low vacuum scanning electron microscopy lvsem observations combined with energy dispersive x ray spectroscopy edxs have been performed the analyses confirm the presence of artifacts intentionally heat treated the thermal treatment achieved in order to increase the quality of the blade production is the first evidence of this technique in northeastern italy during the early neolithic

testing for the presence of thermal pretreatment of flint in the mesolithic and neolithic of sweden abstract through ethnographic accounts the method of heat treatment of silica materials to improve the flaking qualities is shown to have been known almost worldwide some mesolithic and neolithic flint artifacts from southern sweden were examined in order to determine if they too were heat treated from several methods proving or indicating thermal alteration of flint analysis using scanning electron microscopy was chosen two samples were taken from each artifact one being examined unaltered the other being heat treated no two samples from the same artifact had the same kind of surface appearance thus these analyses prove that the artifacts examined had not been heat treated

a 750 yr record of autumn snowfall and temperature variability and winter storminess recorded in the varved sediments of bear lake devon island arctic canada abstract the varve record from high arctic proglacial bear lake reveals a regionally coherent hydroclimatic signal as well as complexities due to changing hydroclimatic and limnologic conditions varve formation is strongly dependent on underflows that exhibit variability in strength during the past 750 yr periods with reduced underflow sedimentation and accumulation rates fail to produce varves in the distal part of the lake isolated coarse silt and sand grains occur in 80 of the varves and are interpreted to be niveo aeolian in origin coarse 500 m sand grains deposited on the lake ice by strong winter winds are notably less common since a d 1850 likely due to reduced storminess regression of the varve thickness record with meteorological records indicates high correlations with autumn september and october temperatures and total monthly snowfall these correlations are best at times when underflow activity is sufficiently strong to produce varves throughout the lake the close association with warmer temperatures and snow bearing synoptic systems moving north in baffin bay suggests that the primary climate signal in the varves is varying autumn snow pack that controls nival discharge in the following year the similarity between the other records of melt season temperature and sea ice cover and the bear lake record suggests that summer and autumn conditions were generally similar across the baffin bay region through much of the last millennium

characteristics of sedimentary varve chronologies a review abstract we constructed a varve data base vdb to study the worldwide distribution of varved sediment records and the fidelity of their varve chronologies clusters of lakes with varved sediments exist in central north america in the canadian arctic and in northern and central europe among the 108 sites included in the vdb varved records are typically 200 500 cm long and cover a period of 1000 2000 years their varve chronologies are often based on counting of annual layers from fresh sediment surfaces and photographs or from epoxy embedded sediment blocks and thin sections the vdb indicates that chronological errors associated with counting sedimentary varves fall generally between 1 and 3 but only 57 of published records are providing quantitative error estimations for their chronologies with a careful documentation of varves and by applying radiometric dating methods to surface sediments as well as using historical events as time markers there is the potential of having centennial long varved records with a very precise age depth control however it is unrealistic to expect errors significantly below 1 from several millennia long sections we found no indication that varve chronologies would have been substantially more accurate and precise in some parts of the world than in others or statistically dependent on varve thickness or temporal extension of a varved sequence according to the vdb close to 90 of the published varve chronologies have been cross checked with some independent dating methods

varves in lake sediments a review abstract downcore counting of laminations in varved sediments offers a direct and incremental dating technique for high resolution climatic and environmental archives with at least annual and sometimes even seasonal resolution the pioneering definition of varves by de geer 1912 had been restricted to rhythmically deposited proglacial clays one century later the meaning of varve has been expanded to include all annually deposited laminae in terrestrial and marine settings under favourable basin configurations and environmental conditions limnic varves are formed due to seasonality of depositional processes from the lake s water column and or transport from the catchment area subsequent to deposition of topmost laminae the physical preservation of the accumulating varved sequence requires the sustained absence of sediment mixing for example via wave action or macrobenthic bioturbation individual sub laminae in varved lake sediments typically express contrasting colours always differ in terms of their organic chemical and or mineralogical compositions and often also differ with regard to grain size various predominating climatic and depositional conditions may result in clastic biogenic or endogenic incl evaporitic varved sediments and their mixtures to reliably establish a varve chronology the annual character of laminations needs to be determined and verified in a multidisciplinary fashion sources and influences of possible errors in varve chronologies are best determined and constrained by repeated varve counts and by including radioisotopes and correlation with historically documented events a well established varve chronology greatly enhances the scientific value of laminated limnic archives by securely anchoring the wealth of multi proxy palaeoenvironmental information in the form of time series for multidisciplinary investigations applications of varved records are discussed with special reference to advances since the 1980s these span fields like calibrating radiometric dating methods reconstructing past changes of the earth s magnetic field or detecting fluctuations in solar forcing once a varve chronology is established it can be applied to precisely date events like volcanic ash layers earthquakes or human impact as well as short and long term climate temperature precipitation wind hydroclimatic conditions or flooding and environmental changes eutrophication pollution due to their exceptional high temporal resolution and in combination with their robust and accurate internal time scale in calendar years annually laminated sediments can be regarded as one of the most precious environmental archives on the continents these records are necessary to extend temporally limited instrumental records back in time as such they have societal relevance with regard to risk assessments related to natural hazards arising from e g flooding or volcanic eruptions

thermal curved fragments a method for identifying anthropogenic fire in the archaeological record abstract the archaeology of fire is a developing field one challenge centers on equifinality distinguishing the affects of wildfire versus anthropogenic fire especially where evidence for control of fire by humans in the early pleistocene remains debated there is little consensus regarding what constitutes clear evidence of human control another concern is preservation bias which reduces clearly identifiable archaeological signatures of fire in this paper we argue that a peculiar lithic angular fragment termed thermal curved fragment tcf exhibits statistically distinct quantitative evidence of the confluence of human knapped stone tools and exposure to a high energy long duration ground level fire i e campfires experimental tcfs are described and compared to unfired knapping debitage natural exfoliations and suspected archaeological tcfs the provenance of these archaeological specimens has previously been argued to infer hominin controlled fire at 1 5 1 6 ma at the koobi fora formation we also present data from experiments exposing stone flakes arranged as scatters of similar raw materials to those found in the koobi fora formation to usda prescribed burns in a variety of conditions approximating landscape fires results indicate that tcfs are formed specifically where previously knapped stone is exposed to high energy ground level fires similar to those seen in ethnographic campfires our analysis indicates that tcfs can be used in conjunction with other lines of evidence indicating the presence of anthropogenic fire in the archaeological record

age and development of active cryoplanation terraces in the alpine permafrost zone at svartkampan jotunheimen southern norway schmidt hammer exposure age dating shd of boulders on cryoplanation terrace treads and associated bedrock cliff faces revealed holocene ages ranging from 0 825 to 8890 1185 yr the cliffs were significantly younger than the inner treads which tended to be younger than the outer treads radiocarbon dates from the regolith of 3854 to 4821 cal yr bp 2 range indicated maximum rates of cliff recession of 0 1 mm year which suggests the onset of terrace formation prior to the last glacial maximum age angularity and size of clasts together with planation across bedrock structures and the seepage of groundwater from the cliff foot all support a process based conceptual model of cryoplanation terrace development in which frost weathering leads to parallel cliff recession and hence terrace extension the availability of groundwater during autumn freeze back is viewed as critical for frost wedging and or the growth of segregation ice during prolonged winter frost penetration permafrost promotes cryoplanation by providing an impermeable frost table beneath the active layer focusing groundwater flow and supplying water for sediment transport by solifluction across the tread snowbeds are considered an effect rather than a cause of cryoplanation terraces and cryoplanation is seen as distinct from nivation

the middle pleistocene site of la cansaladeta tarragona spain stratigraphic and archaeological succession abstract la cansaladeta is a site located in a narrow passage dug out by the francoli river in the pre littoral catalan range ne iberia the archaeological deposit lies on top of a 45 50 m fluvial terrace and contains a rich middle pleistocene stratigraphic succession in which 10 archaeological layers have been identified here we present the description of the sedimentary succession of the site the available chronological framework including tl tt osl and esr u series ages as well as biostratigraphical information the characteristics of the lithotechnical and faunal assemblages as well as the first interpretation of the human occupations at the site three main occupation phases have been differentiated the oldest archaeological layers are embedded in a palaeosol formed on a clayey layer that contains limestone fragments detached from the shelter s wall and roof during the second phase low energy fluvial sediments coming from lateral river floods were deposited and sealed the archaeological layers after a transitional phase the upper layers appear to be derived from slope sediments numerical dating yielded internally consistent dates of 380 400 ka for the sequence however the study of the fossil assemblages potentially suggest a tentative early middle pleistocene age for the lowermost horizons the rich technological record is made up of several local raw materials especially chert but also schist quartzite quartz and other minor rocks knapping sequences seem to be autochthonous as all the elements and size categories of the reduction sequence are present and refits are common techno typological features observed along the sequence are not very diagnostic however the lower layers include some acheulean forms among the large shaped tools restricted variability among the small retouched tools mostly denticulates and a virtually absence of prepared cores the faunal assemblage is scarce and appears strongly altered only the lower layers have provided fruitful information although neither combustion areas nor structures related to fire use have been documented to date heat damage has been repeatedly recorded on both lithic and faunal remains this may point to systematic fire use within the archaeological sequence the data provided by the ongoing excavations at la cansaladeta provide new insight into the early human settlement history of northeast iberia to be reconstructed combining these data with those coming from the close site of barranc de la boella enable us to better reconstruct the timing nature and context of early human occupation in the region

solar activity expressed in a modern varve thickness sequence annually laminated sediments varves form in particular depositional settings e g where seasonal climate produces fluctuations in runoff volume variations in runoff affect the amount and type

holocene sediments from a coastal lake on northern devon island nunavut canada sediment cores from lake dv09 northern devon island nunavut canada 75 34 34 n 89 18 55 w were studied to reconstruct the lake ontogeny through analysis and interpretation of the sediment stratigraphy the lake was uplifted from marine inundation 7600 cal bp after a millennium of rapid sediment accumulation which coincided with the holocene thermal maximum in the region accumulation rates decreased over the past 6000 years as the arctic became colder this resulted in the deposition of very fine laminae that were interpreted as varves the uppermost laminated sediments provided a 1600 year history of annual sediment transport and deposition into the lake during periods of warmer temperatures such as between 6000 and 7500 cal bp and during the medieval climate anomaly 950 1300 ce ce christian era hydroclimatic and permafrost slope processes increased sedimentation rates into the basin

glacial and periglacial buzzsaws fitting mechanisms to metaphors the buzzsaw hypothesis refers to the potential for glacial and periglacial processes to rapidly denude mountains at and above glacier equilibrium line altitudes elas irrespective of uplift rates rock type or pre existing topography here the appropriateness of the buzzsaw metaphor is examined alongside questions of the links between glacial erosion and elas and whether the glacial system can produce low relief surfaces or limit summit heights plateau fragments in mountains on both active orogens and passive margins that have been cited as products of glacial and periglacial buzzsaw erosion instead generally represent dissected remnants of largely inherited pre glacial relief summit heights may correlate with elas but no causal link need be implied as summit erosion rates are low cirque headwalls may not directly abut summits and on passive margins cirques are cut into pre existing mountain topography any simple links between elas and glacial erosion break down on passive margins due to topographic forcing of ice sheet growth and to the km scale vertical swaths through which elas have shifted through the quaternary glaciers destroy rather than create low relief rock surfaces through the innate tendency for ice flow to be faster thicker and warmer along valleys the glacial buzzsaw cuts down

heat treated stone artifacts at shuidonggou northwest china and their archaeological implications artifacts from the shuidonggou sdg site complex in ningxia province provide extensive information and insights regarding the activities of early modern humans in china based on a series of experiments and physical analyses it appears that the stone artifacts from sdg locality 2 and locality 12 have undergone heat treatment that enhanced the utilization ratio and knapping properties of the lithic raw material from which they were made in order to investigate the mechanisms involved compression tests and xrd x ray diffraction examinations were conducted on lithic raw materials collected surround the sdg sites the results indicate that the heated stones present lower compression strength and better ductility and the raw material becomes more homogeneous as well the process of crack propagation also becomes easier to control thereby reducing knapping difficulties the application of heat treatment technology at sdg reflects the production capacities and risk management strategies of the sdg inhabitants and provides evidence for the level of understanding associated with early modern human behavior this discovery confirms the appearance of this technology in the east asia around 32 ka bp which lasts to 11 ka bp providing new evidence for the spread and distribution of heat treatment technology

mechanical characterization of raw material quality and its implication for early upper palaeolithic moravia abstract raw material mechanical tests were conducted to answer the question whether differences in raw material procurement among early upper palaeolithic populations in moravia czech republic may have been driven by different mechanical properties of those materials characterization of mechanical properties of erratic flints and krumlovsk les i type chert show that the relatively finer grained erratic flints preferred by local aurignacian populations are more easily and probably also predictably knapped at higher speeds such as reached with soft antler wood percussors whereas cherts of krumlovsk les i type exploited by both szeletian and aurignacian populations are more resistant to fracture propagation this implies the suitability of the former material for fine blade and bladelet production and of the latter to projectile e g szeletian leaf points manufacture and possibly explains the export of leaf points from szeletian areas the krumlov forest to bohunician and aurignacian sites within moravia exploitation of erratic flints was easier as regards aurignacian and probably entire upper palaeolithic knapping technology certain tasks however were better met with other raw materials thus reflecting the relativity of chipped stone raw material quality perception in the palaeolithic

heat treatment of polish flints abstract in poland three types of flint chocolate spotted and banded were intensively mined from the terminal palaeolithic to the early bronze age although heating of flint to improve its flaking properties was practised across the world from 110 000 years ago to the recent particularly in southwestern europe heat treatment of flint in poland is known from only two sites experimental studies showed that controlled heat treatment of polish flints causes subtle variable changes in colour but a consistent marked increase in lustre on fractured surfaces which should make heat treated artefacts easy to recognise in the polish archaeological record heat treatment also causes a substantial reduction in the fracture toughness of all tested polish flint types and a concomitant increase in flakeability the effect is greatest for banded flint due to its initially higher fracture toughness the decrease in fracture toughness is caused by recrystallisation allowing fractures to propagate more easily in banded flint the average crystal size increases and within chocolate and spotted flint the fibrous chalcedony patches become more granular although the flaking properties of banded flint are improved markedly by heat treatment the procedure was applied only occasionally by prehistoric flintknappers to this material banded flint was preferentially used for completely polished axes and only rarely for blades because chocolate and spotted flints are available close to the banded flint mines these flint types have far superior flaking properties and were extensively used for blade manufacture spotted flint is generally less suitable for heat treatment it is subject to explosive thermal spalling due to its abundant calcite inclusions although heat treatment improves the flaking properties of chocolate flint heated chocolate flint is rare in the polish archaeological record probably because high quality flint was so abundant in poland

solar signature in sedimentary cycles from the late precambrian elatina formation australia climatic cyclicity is recorded by regular variations in the thickness of varves in the elatina formation a late precambrian periglacial lake deposit in south australia earlier conclusions that the climatic cycles reflect solar variability are strongly supported by a complexity of periods revealed through study of drill cores of the varved sequence the new data promise to contribute significantly to our understanding of solar processes

cosmogenic 10be and 36cl geochronology of cryoplanation terraces in the alaskan yukon tanana upland cryoplanation terraces are prominent but enigmatic landforms found in present and past periglacial environments geomorphologists have debated for more than a century over processes involved in the formation of these elevated step like bedrock features presented here are the first numerical surface exposure ages and scarp retreat rates from cryoplanation terraces in the yukon tanana upland ytu in alaska part of unglaciated eastern beringia obtained from terrestrial cosmogenic nuclides tcn in surface boulders ages comprise six 10be tcn ages from two terrace treads near eagle summit and six 36 cl ages from two treads on mt fairplay based on these exposure ages scarps at both locations were last actively eroding from 49 to 22 4 ka both locations exhibit time transgressive development particularly near scarp tread junctions boulder exposure ages and distances between sampled boulder locations were used to estimate scarp retreat rates of 0 11 to 0 56 cm yr these numerical exposure ages presented here demonstrate that the cryoplanation terraces in the ytu are diachronous surfaces actively eroding during multiple cold intervals with these results hypotheses for cryoplanation terrace formation are discussed and evaluated for the ytu including those based on geologic structure nivation and the influence of permafrost

experimental sourcing of edwards plateau chert using la icp ms abstract sourcing artifacts is a key method for addressing anthropological issues of mobility and interaction although chert was one the most common toolstones used in prehistory sourcing chert artifacts remains problematic in this study an approach for sourcing chert is introduced that links a specific sampling protocol laser ablation inductively coupled plasma mass spectrometry la icp ms and multivariate statistical analysis the effectiveness of this approach is demonstrated through a controlled experiment examining intersource and intrasource variability at four different scales of analysis the statistical analysis at four spatial scales allows determination of the spatial resolution of the chemical matching procedure outlined here in this experiment geologic chert samples from the edwards plateau of texas of known provenience are chemically evaluated allowing comparison of their expected origin against their known origin this experiment used edwards plateau chert as it is a high quality material and was a major lithic source across the southern high plains and was often transported great distances macroscopic identification of edwards plateau chert can be problematic and at its best is unable to effectively discern from where within the 120 000 km 2 of the region cherts originated an understanding of the geological formation processes of chert provides a useful framework for addressing this issue this study shows that through an effective methodology edwards plateau chert can be sourced to a finer spatial scale than previous studies

silica diagenesis origin of inorganic and replacement cherts abstract silicification of originally non siliceous sediments affects a wide variety of rock types and materials and ranges from minor to pervasive partial and minor chertification occur mostly in phanerozoic carbonates carbonate bearing sandstones evaporites and fossil wood the source of the silica is predominantly biogenic in petrified wood the silicification mechanism is a permeation or void filling process not a replacement in this example the sequence of silica phase transformation is the same as that in deep sea siliceous sediments in many silicified rocks particularly in certain carbonates the transformation sequence is different from that in radiolarites or diatomites the chemical environment and conditions of early diagenetic chert formation in shallow water carbonates are delineated by the general mixing model of knauth 1979 but remain unknown for most other types an exception are the flint nodules and bands of the english chalk a detailed geochemical study of the paramoudra flint structures by clayton 1986 provided remarkable insight into the replacement process seven different recurring silica fabrics have been recognized in chert replaced carbonates including equigranular microcrystalline quartz or microquartz and megaquartz and fibrous types chalcedony quartzine or length slow chalcedony lutecite zebraic chalcedony and microflamboyant quartz among the latter quartzine and microflamboyant quartz are common in but by no means restricted to chert replaced evaporites for which milliken 1979 recognized a sequence of seven quartz fabrics as a single criterion only anhydrite inclusions in megaquartz quartzine or microflamboyant quartz provide unequivocal evidence for an evaporite precursor the relative timing between silicification and well established diagenetic carbonate reactions shows that virtually all theoretically possible sequences occur chertification of carbonate host sediment thus may take place during early intermediate or late diagenesis and even during anchimetamorphism pervasive to complete silicification has been described in lacustrine pedogenic and hydrothermal volcanogenic rocks and occurs on the scale of individual beds members or entire formations it may affect some of the aforementioned rock types too for example carbonates the source of the silica is predominantly inorganic chert formation in these environments includes direct chemical silica precipitation from solution through a gel stage magadi type cherts result from the conversion of the hydrous sodium silicate magadiite into microcrystalline quartz which has occurred in east african rift valley lakes such as lake magadi in late pleistocene time they are closely related to directly precipitated inorganic cherts which have been observed in alkaline environments of playa lakes silcretes originate from weathering and soil forming processes under climatic and environmental conditions conducive to the formation of duricrusts and laterites in more humid climates however non weathering profile silcretes occur which have been distinguished from weathering profile silcretes four to five different silcrete fabric types have been established including the 1 grain supported or quartzitic 2 floating terrazzo 3 matrix albertinia and opaline and 4 conglomeratic types in volcanic edifices silicification related to hydrothermal activity occurs 1 along the ascent routes of the fluids vents within the volcanic complexes 2 in isolated ponds and depressions on the sea floor where the fluids discharge mostly in the median rift valley of mid ocean ridges and 3 in geothermal areas on land associated with spreading lineaments volcanic islands arcs transform faults or continental hot spots attention has focussed on the associated base metal concentrations and less on the silicification and accompanying iron enrichment processes the precambrian banded iron formations may be indirectly or directly related to hydrothermal volcanic processes the origin of these cherty iron formations certainly requires more than one genetic model and at present remains a major unresolved problem despite massive efforts to tackle it

spectral albedos of sea ice and incident solar irradiance in the southern beaufort sea spectral albedos and incident spectral irradiances have been measured over the wavelength range 400 to 2400 nm on the sea ice near the naval arctic research laboratory narl at pt barrow alaska the observation interval extended from mid may when the ice was still relatively cold until mid june when summer melting was fully established the temporal dependence of albedo for the available surface types was obtained over this time interval showing a general decrease from snow and snow covered ice to blue ice and melt ponds data were also obtained for glacier ice on the athabasca glacier for melting lake ice and for certain other nonice surfaces in the vicinity of narl snow and ice albedos are characteristically highest at visible wavelengths decreasing strongly in the infrared because of the increase in absorption by ice and water local maxima in the spectra correspond to minima in the ice and water absorption variations in albedo are due primarily to differences in the vapor bubble density crystal structure and free water content of the upper layers of the ice incident spectral shortwave radiation was measured as a function of cloudiness and the optical thickness of arctic clouds is significantly less than the thickest clouds at lower latitudes the decrease of the infrared component relatiave to the visible portion of the irradiance with increasing cloud cover is determined this can give rise to an increase in wavelength integrated albedos of as much as 15 using the present data a graphical method is outlined by which visible near infrared satellite imagery can be used to distinguish among melt ponds open leads and other spring and summer sea ice surface types

nodular chert from the arbuckle group slick hills sw oklahoma a combined field petrographic and isotopic study nodular chert from the middle and upper arbuckle group early ordovician in the slick hills sw oklahoma was formed by selective replacement of grainstones burrow fillings algal structures and evaporite nodules chert nodules are dominantly microquartz with minor fibrous quartz both quartzine and chalcedony megaquartz and microflamboyant quartz lepisphere textures of an opal ct precursor are preserved in many especially in finely crystalline chert nodules the 18o values of microquartz chert range from 23 4 to 28 80 00 smow significantly lower than those of cenozoic and mesozoic microquartz chert formed both in the deep sea and from near surface sea water the 18o values of chert decrease with increasing quartz crystal size silicification in the arbuckle group occurred during early diagenesis with the timing constrained by the relative temporal relationships among silicification burial compaction and early dolomite stabilization silica for initial chert nucleation may have been derived from both dissolution of sponge spicules and silica enriched sea water chert nucleation appears to have been controlled by the porosity permeability and organic matter content of precursor sediments this conclusion is based on the fact that chert selectively replaced both porous grainstones and burrows and algal structures enriched in organic matter growth of chert probably occurred by a maturation process from opal a to opal ct to quartz as indicated by the presence of opal ct precursor textures in many chert nodules although field and petrographic evidence argues for an early marine origin for chert in the arbuckle group the light 18o values are inconsistent with this origin meteoric resetting of the 18o values of the chert during exposure of the carbonate platform best explains the light 18o values because i the 18o values of chert nodules decrease with decreasing 18o values of host limestones and ii chert nodules from early dolomite which underwent more extensive meteoric modification than associated limestones have lighter 18o values than chert nodules from limestones increasing recrystallization of chert nodules by meteoric water resulted in progressive 18o depletion and quartz crystal enlargement

climatic limits on landscape development in the northwestern himalaya the interaction between tectonism and erosion produces rugged landscapes in actively deforming regions in the northwestern himalaya the form of the landscape was found to be largely independent of exhumation rates but regional trends in mean and modal elevations hypsometry frequency distribution of altitude and slope distributions were correlated with the extent of glaciation these observations imply that in mountain belts that intersect the snowline glacial and periglacial processes place an upper limit on altitude relief and the development of topography irrespective of the rate of tectonic processes operating

a frost buzzsaw mechanism for erosion of the eastern southern alps new zealand article in the southern alps new zealand large gradients in precipitation b 1t o 12 m year 1 and rock uplift b 1t o 10 mm year 1 produce distinct post glacial geomorphic domains in which landslide driven sediment production dominates in the wet rapid uplift western region and rockfall controls erosion in the drier low uplift eastern region because the western region accounts for b25 of the active orogen the dynamics of erosion in the extensive eastern region are of equal importance in estimating the relative balance of uplift and erosion across the southern alps here we assess the efficacy of frost cracking as the primary rockfall mechanism in the eastern southern alps using air photo and topographic analysis of scree slopes cosmogenic radionuclide dating of headwalls paleo climate data and a numerical model of headwall temperature currently active scree slopes occur at a relatively uniform mean elevation 1450 m and their distribution is independent of hillslope aspect and rock type consistent with the notion that frost cracking which is maximized between 3 and 8 c may control rockfall erosion headwall erosion rates of 0 3 to 0 9 mm year 1 measured using in situ 10 be and 26 al in the cragieburn range confirm that rockfall erosion is active in the late holocene at rates that roughly balance rock uplift models of the predicted depth of frost activity are consistent with the scale of fractures and scree blocks in our field sites also vegetated paleo scree slopes are ubiquitous at elevations lower than active scree slopes consistent with the notion that lower temperatures during the last glacial advance induced pervasive rockfall erosion due to frost cracking our modeling suggests temporally averaged peak frost cracking intensity occurs at 2300 m a s l the approximate elevation of the highest peaks in the central southern alps suggesting that the height of these peaks may be limited by a frost buzzsaw

heating of flint debitage from upper palaeolithic contexts at manot cave israel changes in atomic organization due to heating using infrared spectroscopy abstract the heat treatment of flint is known to change its mechanical properties and improve its fracture behaviour during knapping here we examine 20 flint artifacts from upper paleolithic contexts from manot cave israel using fourier transform infrared spectroscopy and compare them to geogenic flint beds from the walls inside the cave and from outcrops just above the cave we show that the 512 and 467 cm 1 peaks are broader in most of the flint debitage pieces as compared to the geogenic flint and that broadening of these peaks occurs when geogenic flint from the cave wall is heated we also present an empirical simple method to monitor these changes

a 3000 year varved record of glacier activity and climate change from the proglacial lake hvitarvatn iceland a suite of environmental proxies in annually laminated sediments from hvitarvatn a proglacial lake in the central highlands of iceland are used to reconstruct regional climate variability and glacial activity for the past 3000 years sedimentological analysis is supported by tephrostratigraphy to confirm the continuous annual nature of the laminae and a master varve chronology places proxies from multiple lake cores in a secure geochronology varve thickness is controlled by the rate of glacial erosion and efficiency of subglacial discharge from the adjacent langjokull ice cap the continuous presence of glacially derived clastic varves in the sediment fill confirms that the ice cap has occupied the lake catchment for the duration of the record varve thickness varve thickness variance ice rafted debris total organic carbon mass flux and bulk concentration and c n of sedimentary organic matter reveal a dynamic late holocene climate with abrupt and large scale changes in ice cap size and landscape stability a first order trend toward cooler summers and ice cap expansion is punctuated by notable periods of rapid ice cap growth and or landscape instability at ca 1000 bc 600 bc 550 ad and 1250 ad the largest perturbation began ca 1250 ad signaling the onset of the little ice age and the termination of three centuries of relative warmth during medieval times consistent deposition of ice rafted debris in hvitarvatn is restricted to the last 250 years demonstrating that langjokull only advanced into hvitarvatn during the coldest centuries of the little ice age beginning in the mid eighteenth century this advance represents the glacial maximum for at least the last 3 ka and likely since regional deglaciation 10 ka the multi centennial response of biological proxies to the hekla 3 tephra deposition illustrates the significant impact of large explosive eruptions on local environments and catchment sensitivity to perturbations

holocene archeointensities from mid european ceramics slags burned sediments and cherts abstract the earth s geomagnetic field intensity in the past can be determined from archeological artifacts these archeointensity data are important inputs for geomagnetic field models and local reference curves of earth s magnetic field although archeointensities have been measured on materials for more than half a century ago data are still scarce before 1000 bc and for the alpine area in general this investigation presents new absolute archeointensity data from a time period of 5000 700 bc from italy and switzerland the archeological materials that were studied are ceramics copper slag and burned sediments from fireplaces in addition we investigated archeointensities from burned cherts in order to uncover if they are a suitable material for paleomagnetism rock magnetic properties of all samples indicate magnetite and small amounts of maghemite and hematite in the pseudosingle domain range as the ferromagnetic carriers the izzi protocol was used for 96 specimens to obtain absolute intensities 23 ceramics slags and burned cherts passed the threshold criteria which we applied the choice of the threshold values allowed us to obtain the linear part in the arai diagram which corresponds to the characteristic remanent magnetization burned sediments did not pass the threshold criteria most probably because they acquired a thermochemical remanent magnetization during their formation we demonstrate that magnetic susceptibility and saturation isothermal remanent magnetization can be used to select cherts that are suitable for paleointensity determinations after applying anisotropy and cooling rate corrections the new archeointensity values are lower for some samples but fit well with available models and other archeomagnetic data

the still bay points of blombos cave south africa we present the results of a technological and morphometric analysis of all the still bay points n 371 recovered from the 1993 to 2004 excavations at blombos cave we have been able to reconstruct the manufacturing sequence of the bifacial points from initial shaping by direct internal percussion to finished morphology by direct marginal percussion identifications of impact fractures and manufacturing breaks are based on comparisons with experimental and archaeological bifacial points of verified function i e paleoindian points from bison kill sites replicates of solutrean points mounted as spear heads or arrowheads and shot into adult cattle and experimental replication on local raw materials our analysis shows that a only a minority of the points are finished forms and that a large number of pieces are production failures a situation known at bifacial point production sites of later ages b morphometric and impact scar analyses should take into account this process and distinguish finished points from preforms and unfinished points c there were at least three different kinds of raw material sources and that there is a marked increase in the frequencies of silcrete with respect to the m2 and m3 phases at blombos d three kinds of evidence prove that some of the points were hafted axially and used as spear tips e production of bifacial points was a primary activity at the site but the hypothesis of intergroup exchange of still bay points cannot be sustained on the basis of present evidence and f the still bay phase appears to initiate a trend to relatively rapid changes in specialized hunting weaponry and that this innovation is congruent with other innovations such as bone tools shell beads and engraved ochre of the m1 and m2 phases at blombos

cosmogenic chlorine 36 from calcium spallation calcium is a major target element for cosmogenic 36cl production consequently 36cl rapidly reaches detectable levels in minerals such as calcite and calcium feldspar exposed at the earth s surface spallation of calcium isotopes typically accounts for 80 90 of 36cl production in these minerals with subsidiary contributions from negative muon capture by 40ca and thermal neutron capture by 35cl to provide a basis for surface exposure dating we have calibrated cosmogenic 36cl production in calcium feldspar from the 17 300 year old tabernacle hill basalt at an altitude of 1445 m and an effective geomagnetic latitude of 40 9 the calcium spallation rate is 152 11 atoms g ca 1 a 1 the corresponding rate at sea level and high latitude is estimated at 48 8 3 4 atoms g ca 1 a 1 the muon capture rate used to derive these values is 8 8 2 2 atoms g ca 1 a 1 at the tabernacle hill site scaled from a value of 4 8 1 2 atoms g ca 1 a 1 at sea level and high latitude the calcium spallation rate determined in this study is in excellent agreement with previous whole rock calibration measurements at tabernacle hill when these are recalculated with respect to the absolute timescale the calibration of 36c1 production from calcium underpins development of an exposure dating technique for calcite due to its high calcium content the 36cl production rate in calcite is higher than in any other common rock forming mineral measurement of 36cl in calcite with an accelerator mass spectrometric detection limit of 5 103 atoms per gram allows dating of limestone surfaces exposed for periods ranging from 102 106 years alternatively erosion rates from less than 1 to greater than 1000 m per year can be determined in the case of eroding karst surfaces though the 36cl production rate is lower in calcium feldspar than in calcite measurements on this mineral will provide a useful means of dating young basalt lavas