moderate temperature zeolitic alteration in a cooling pyroclastic deposit abstract the locally zeolitized topopah spring member of the paintbrush tuff 13 myr yucca mountain nevada u s a is part of a thick sequence of zeolitized pyroclastic units most of the zeolitized units are nonwelded tuffs that were altered during low temperature diagenesis but the distribution and textural setting of zeolite heulandite clinoptilolite and smectite in the densely welded topopah spring tuff suggest that these hydrous minerals formed while the tuff was still cooling after pyroclastic emplacement and welding the hydrous minerals are concentrated within a transition zone between devitrified tuff in the central part of the unit and underlying vitrophyre movement of liquid and convected heat along fractures from the devitrified tuff to the ritrophyre caused local devitrification and hydrous mineral crystallization oxygen isotope geothermometry of cogenetic quartz confirms the nondiagenetic moderate temperature origin of the hydrous minerals at temperatures of 40 100 c assuming a meteoric water source the topopah spring tuff is under consideration for emplacement of a high level nuclear waste repository the natural rock alteration of the cooling pyroclastic deposit may be a good natural analog for repository induced hydrothermal alteration as a result of repository thermal loading temperatures in the topopah spring vitrophyre may rise sufficiently to duplicate the inferred temperatures of natural zeolitic alteration heated water moving downward from the repository into the vitrophyre may contribute to new zeolitic alteration

a search for basaltic to intermediate glasses on mars assessing martian crustal mineralogy multiple datasets have demonstrated that the crust of mars is fundamentally basaltic however spectral libraries used to interrogate thermal infrared spectra of martian dark regions through spectral deconvolution have heretofore lacked mafic glasses despite the importance of amorphous phases or phases with amorphous like spectral signatures in martian mineralogy to establish the presence and importance of basaltic to intermediate glasses in martian lithologies we created five such glasses obtained their thermal infrared spectra and included the spectra in a library used to deconvolve nine regional thermal emission spectrometer spectra from mars we employed the nonnegative least squares nnls deconvolution method which yields deconvolved phase abundances and the uncertainties associated with those abundances the basaltic to intermediate glasses do not appear in the deconvolution solutions indicating they are not globally or regionally important phases because martian igneous or impact processes are capable of basaltic to intermediate glass formation the lack of such glasses in the deconvolved mineralogies suggests either the glasses did not form in detectable quantities or they or their signatures have been removed the masking or replacement of basaltic to intermediate glasses through alteration is supported by the appearance in the deconvolution solutions of amorphous phases e g silica rich glasses opal or phases with amorphous like spectral signatures e g clays zeolites that commonly form through aqueous alteration of mafic glasses the glasses may still be important to local scale thermal infrared studies given the basaltic nature of mars and the variety of local scale lithologies detected by various missions the regional mineralogies derived from the nnls deconvolution analysis divide into five statistically separable groups which provide insight into regional trends in mineralogy

zeolitic diagenesis of late quaternary fluviolacustrine sediments and associated calcrete formation in the lake bogoria basin kenya rift valley late quaternary fluviolacustrine siltstones mudstones and claystones loboi silts on the northern margins of the saline alkaline lake bogoria in the kenya rift valley contain up to c 40 authigenic analcime and minor natrolite the zeolitic sediments are reddish brown and up to 1 m thick the amount of analcime increases upward in the profile but decreases with distance from the lake the altered sediments show many pedogenic features including zeolitic root mats rootmarks concretions and carbonate rhizoliths residual patches of calcrete locally cap the zeolitic rocks the profile is interpreted as an exhumed palaeosol and land surface on the former margins of the lake the analcime occurs as submicroscopic 0 5 2 5 m subhedral and euhedral crystals which have an average si a 1 ratio of 2 33 as determined by x ray microanalysis or 2 18 d value of 639 analcime peak the analcime formed in lake marginal sediments soils by reaction of silicate detritus with na2co3 rich pore waters concentrated close to the land surface by evaporative pumping and evapotranspiration poorly ordered clay minerals were probably the main reactants authigenic illite may have been a by product of the reactions chemical analyses suggest that pore waters supplied some of na and possibly k and sio2 the associated calcrete and rhizoliths were formed during or shortly after the main period of zeolitic alteration the ca2 may have originated from infiltrating dilute runoff and groundwater authigenic smectite was precipitated in open porosity following analcime formation the zeolitic alteration at lake bogoria provides a relatively recent analogue for lake marginal zeolites found in many ancient saline alkaline lake sediments

a 3d morphometric analysis of surface geometry in levallois cores patterns of stability and variability across regions and their implications levallois cores and products were manufactured by hominin populations distributed across wide regions of africa and eurasia levallois technology remains an important focus for research in palaeolithic archaeology yet quantitative morphological comparisons of levallois core morphology from different regions remain rare here utilizing levallois cores from africa the near east europe and the indian subcontinent patterns of morphological variability in the shape of the levallois flaking surface and core outline margin shape were examined for patterns of variability and stability across regions using 3d geometric morphometrics the multivariate statistical shape analyses undertaken revealed a clear pattern that is the greatest levels of shape variability in levallois cores is evident in the form of their outline planform shape conversely the geometrical relationship between the margin of the levallois cores and their topological surface morphology was relatively uniform this pattern of variability was evident in terms of variation both across regions and between cores from the same locality these results indicate that the outline form of such cores was a less important variable than the geometric topological properties of the surface morphology and in particular the relationship between the margin of the core and those variables these results have implications for why it has been reported that replicating such cores in modern experiments is a particularly difficult task the specific interrelationship between the geometric properties of the core and the core margin provide further evidence that levallois core technology would be unlikely to emerge from the context of opportunistic migrating platform reduction strategies such as those seen in many mode 1 industries if as is widely suggested levallois cores were deliberate products in pleistocene contexts these results also hint that relatively sophisticated means of social transmission i e teaching may have been required to sustain their production over time and space

the effect of raw material on inter analyst variation and analyst accuracy for lithic analysis a case study from olduvai gorge this study aims to understand what effect in terms of inter analysis variation and analyst accuracy different raw material types have on modern technological analyses of lithic assemblages this is done through a series of blind analysis tests undertaken on experimentally derived assemblages of cores and flakes novelties of our approach include the introduction of refit studies as a method to assess analyst s accuracy and the use of statistical tests specifically designed to address inter analyst variability common in other disciplines but rarely used in archaeology the experimental assemblages were produced from raw materials collected at olduvai gorge an archaeological sequence that has been a source for studies of early human technology for several decades and where re analyses of the same assemblages have usually offered different interpretations the results of the blind analyses are compared to the true technological values obtained through full refit analysis of the experimental material and suggest that there is a significant difference in terms of inter analyst variability as well as accuracy related to different raw materials our paper highlights the interpretative problems posed by difficult to analyse raw materials such as quartzite and stresses subjectivity present in stone tool technological studies which may contribute to explain differences in the interpretation of early stone age lithic assemblages

flake morphologies and patterns of core configuration at the abric romani rock shelter a geometric morphometric approach abstract the current debate about mousterian core technologies mainly focuses on the issues of flake predetermination and the morphological similarities of blanks in discoid and centripetal recurrent levallois methods to date the arguments presented have either been based on qualitative analyses of the cores or on the use of ratios of linear measurements to infer the shape of the detached flakes this paper presents the results of applying 2d geometric morphometric analysis to the flake assemblages in the archaeological collections from the o and m levels of the abric romani rock shelter and from materials produced by experimental knapping the results reveal a pattern of core configuration in the levallois artefacts from level o and a high level of morphological correspondence between the core edge flake outlines in discoid and levallois recurrent centripetal technologies this evidence reinforces the hypothesis that the discoid and the levallois recurrent centripetal methods share some techno morphological features the knappers ability and the purposes of the reduction sequences play important roles in metrically differentiating between them otherwise the differences between the two methods would be even smaller the use of geometric morphometric analysis of flake assemblages can enhance discussions of flaking technologies in lithic studies and quantitatively improve our understanding of the patterns of core configuration and the skills of the prehistoric knappers

geochemical and physical characterization of lithic raw materials in the olduvai basin tanzania abstract the invention and proliferation of stone tool technology in the early stone age esa marks a watershed in human evolution patterns of lithic procurement manufacture use and discard have much to tell us about esa hominin cognition and land use however these issues cannot be fully explored outside the context of the physical attributes and spatio temporal availability of the lithic raw materials themselves the olduvai basin of northern tanzania which is home to both a wide variety of potential toolstones and a rich collection of esa archaeological sites provides an excellent opportunity to investigate the relationship between lithic technology and raw material characteristics here we examine two attributes of the basin s igneous and metamorphic rocks spatial location and fracture predictability a total of 244 geological specimens were analyzed with non destructive portable xrf pxrf to determine the geochemical distinctiveness of five primary and secondary sources while 110 geological specimens were subjected to schmidt rebound hardness tests to measure fracture predictability element concentrations derived via pxrf show significant differences between sources and multivariate predictive models classify geological specimens with 75 80 accuracy the predictive models identify naibor soit as the most likely source for a small sample of three lithic artifacts from bed ii which supports the idea that this inselberg served as a source of toolstone during the early pleistocene clear patterns in fracture predictability exist within and between both sources and rock types fine grained volcanics show high rebound values associated with high fracture predictability while finer grained metamorphics and coarse grained gneisses show intermediate and low rebound values respectively artifact data from bed i and ii suggest that fracture predictability played a role in raw material selection at some sites but other attributes like durability expediency and nodule size and shape were more significant

u pb geochronology of the mazinaw terrane an imbricate segment of the central metasedimentary belt grenville province ontario the mazinaw terrane in the central metasedimentary belt of the grenville province comprises volcanic sedimentary and plutonic rocks that were intensely folded and faulted and metamorphosed to as high as upper amphibolite facies u pb geochronology establishes an early period of magmatism and sedimentation at about 1280 1240 ma probably in a marginal basin setting and a multistage rhetamorphic evolution in the period between 1100 and 980 ma which was probably related to crustal thickening by imbrication during compression and wedging of the terrane some of the earliest magmatism formed calc alkalic volcanic rocks of kashwakamak formation at 1276 2 ma an associated sedimentary assemblage was intruded by the helena trondhjemite stock at 1267 5 ma a younger succession formed between 1250 and 1240 ma includes the bimodal volcanic mazinaw lake formation alaskitic granites of the norway lake and abinger plutons and a granodioritic gneiss phase of the cross lake pluton these units were covered

geochronology and geochemistry of precambrian gneisses metabasites and pegmatite from the tobacco root mountains northwestern wyoming craton montanathis article is one of a series of papers published in this special issue on the theme of geochronology in honour of tom krogh t e krogh deceased april 2008 the middle mountain metamorphic domain of the montana metasedimentary terrane northwestern wyoming craton within the northwestern tobacco root mountains mainly comprises migmatized tonalitic gneiss interlayered with amphibolitic hornblende gneiss both of which are cut by metamorphosed mafic rocks together these gneisses are defined as middle mountain gneiss archean tonalitic gneiss from west of and amphibolitic gneiss from east of the bismark fault give from chemically and air abraded zircon grains u pb id tims ages of 3325 5 1 7 and 3340 ma respectively these results reflect primary magmatic ages and show that the middle mountain gneiss extends into the northern area of the central fault block between the bismark and mammoth faults older crustal processes in the tonalitic gneiss are evidenced by inherited grains the oldest of which is 3460 ma a metabasite hosted in tonalitic gneiss in the bismark fault selvage zone yields a zircon age of 2468 ma which is interpreted as the time of

a comparative analysis of bipolar and freehand experimental knapping products from olduvai gorge tanzania abstract this study aims to investigate the quantitative and qualitative differences between freehand and bipolar experimental knapping products of quartzite from olduvai gorge tanzania a series of blind analyses are undertaken in order to better understand the effect that olduvai quartzite may have on both inter analyst variation and analyst accuracy in the identification of bipolar knapping products this is followed by a comprehensive analysis of the morphology of experimental freehand and bipolar flakes and cores incorporating both traditional linear measurements as well as 2d geometric morphometric analysis additionally the validity of qualitative bipolar attributes are assessed in the differentiation between knapping techniques the results of this study highlight the analytical difficulties and the high levels of analyst subjectivity in identifying bipolar knapping in olduvai quartzite assemblages additionally it is noted that the majority of morphometric measures of bipolar and freehand knapped products do not differ significantly and should not be used in isolation for recognition of these knapping techniques instead conservative analysis of qualitative bipolar traits on cores may offer better results in the identification of knapping technique

hydrogeologic control on zeolitic diagenesis of the white river sequence smectite opal ct and clinoptilolite are common alteration products in the white river sequence a mid tertiary unit in the great plains and northern rocky mountains the white river sequence is largely made up of fine grained tuffaceous material that is rich in unaltered rhyolitic glass smectite is ubiquitous and it or a precursor phase was present during white river soil formation but also formed after burial smectite fe from 5 to 7 fe 2 o 3 and ti from 0 4 to 0 8 tio 2 concentrations in mud rocks suggest formation from dacitic to latitic glass rhyotitic glass however was the primary source for opal ct and clinoptilolite opal ct and clinoptilolite have a highly variable distribution over macroscopic to regional scales of observation stable isotopic compositions of smectite 18 o smow 11 8 to 13 3 opal ct 18 o smow 19 9 to 24 3 and late diagenetic calcite 18 o smow 10 3 2 0 suggest that burial diagenetic reactions took place at temperatures ranging from 27 to 55 c clinoptilolite apparently formed in areas with high contact times between paleoground water and vitroclastic material in white river rocks of wyoming clinoptilolite occurs only in localities that are interpreted as lying within paleo ground water discharge zones in the great plains clinoptilolite is rare in eastern colorado and southern nebraska but progressively increases in abundance to the north reflecting a northward decrease in permeability zeolitic alteration near douglas wyoming changed the hydrologic role of tuffs from aquifers to aquitards tuffs were originally aquifers because of their high permeability 30 md relative to interbedded mud rocks 10 4 to 1 md signigicant thicknesses 0 5 to 2 m presentday and lateral continuity tuff alteration however decreased permeability by 4 orders of magnitude relative to glass rich portions similar diagenetic effects on mud rock permeabilities are likely mass flux into altered tuffs at douglas is indicated by an increase in bulk rock density from 1 3 g cm 3 for glass rich tuff to 1 7 and 2 0 g cm 3 respectively for zeolitic and siliceous counterparts local silica redistribution accouts for the bulk of the density increases a systematic increase in ba content of clinoptilolite over a 150 m vertical section from 0 1 to 6 6 mol of the exchangeable cations suggests that it was derived from underlying units

authigenic silicates and silica polymorphs in the miocene saline alkaline deposits of the karlovassi basin samos greece the lower neogene unit of the karlovassi basin samos island greece was deposited in a continental basin during miocene times and consists of four successions overlying a basal conglomerate the four successions are from the base upward carbonates tuffaceous rocks claystones and porcelanites volcanic glass was originally abundant in the tuffaceous succession but is now represented by its diagenetic products including boron bearing k feldspar the zeolites clinoptilolite analcite and mordenite smectite opal disordered tridymite cristobalite cristobalite and minor amounts of the zeolites erionite phillipsite and chabasite and tridymite evaporite minerals such as gypsum celestite and thenardite are present along with authigenic silicates in tuffaceous intervals into the claystone succession authigenic silica polymorphs represented by opal and chalcedony were identified in the uppermost succession of porcelaneous limestones to chert five irregular concentric zones related to the presence and kind of zeolites and k feldspar are recognized in the lower neogene unit 1 a marginal zone of carbonate and detrital silicate minerals nonauthigenic silicates 2 a clinoptilolite zone 3 a mixed clinoptilolite analcite zone 4 an analcite zone and 5 a central boron bearing k feldspar zone the general pattern of zonation and distribution of authigenic silicates as well as their chemical characteristics indicates the presence of a saline alkaline lake during miocene times this lake is analogous to those of the same age which existed in southern yugoslavia and western turkey where borate sulfate and double carbonate deposits were formed along with authigenic silicates it is possible that a large continental area in the eastern mediterranean underwent large scale dessication which took place during the miocene messinian salinity crisis resulting in the development of highly saline alkaline lacustrine environments

genesis of poikilotopic zeolite in aeolianites an example from the parnaiba basin ne brazil abstract zeolite cement is one of the main components of the jurassic to lower cretaceous fluvial aeolian succession in the parnaiba basin northeastern brazil core and outcrop based stratigraphic analyses permitted the paleo environmental and diagenetic interpretation of aeolian sandstone and showed the influence of the volcanic substrate in the origin of the zeolite cement the substrate is represented by an extensive volcanic plain developed in the last stages of the central atlantic magmatic province camp in west gondwana the siliciclastic deposits consist of dune field sand sheet and wadi deposit facies associations the zeolite cement of the aeolian succession forms poikilotopic crystals with anomalous up to 50 modal content x ray diffraction and sem eds cl analyses showed laumontite and ca stilbite exhibiting respectively massive and radial textures during eodiagenesis the main processes included clay infiltration linked to water table fluctuations and flash flood events producing clay coatings and displacive stilbite cementation massive laumontite cementation and smectite chlorite conversion occurred in the mesodiagenesis while in the final stages the zeolite was partially replaced by calcite cement telodiagenesis is recorded by iron exsudation and the corrosion of clay films several processes can be inferred to explain the origin of the zeolite cement in the jurassic lower cretaceous sandstone of the parnaiba basin after the first magmatic pulse triassic magmatism the zeolite bearing basalts were submitted to chemical weathering causing cation leaching afterwards the deposition of aeolian sands related to a wet desert system occurred above this weathered substrate fractured basaltic substrate favored the release of ions to the surface with fluids enriched in sodium and calcium that percolated the permeable aeolian sandstone beds during the diagenesis furthermore zeolite cement is geographically associated with the volcanic substrate in the western parnaiba basin however it is absent in the eastern part where the aeolianites overlie sedimentary rocks we suggest that the system was thermally reactivated by the last thermal camp phase with basalt emplacement in the eastern parnaiba basin linked to the opening of the equatorial atlantic ocean cretaceous magmatism the progressive heating towards the western part of the basin triggered fluids convection and the enrichment in ions such as ca2 si4 na al3 hco 3 and so42 promoting optimal conditions for zeolite crystal growth 100 c 300 c sandstone textural aspects as well as extensional faults and fractures allowed fluids migration resulting in the massive poikilotopic zeolite cementation characterizing one of the most singular features of the diagenetic history of the west gondwana record

age and origin of the jan lake complex a glimpse at the buried archean craton of the trans hudson orogen the largely buried sask craton is a continental fragment or microcontinent that collided with and underthrust the paleoproterozoic flin flon glennie protocontinent along the pelican decollement zone at 1840 1830 ma rocks of the sask craton are exposed in three tectonic windows those of the pelican window have been named the jan lake complex and comprise 2960 ma arc derived leucocratic orthogneisses migmatitic paragneisses and a tholeiitic within plate igneous suite comprising 2488 ma dioritic to gabbroic rocks and 2450 ma enderbitic and charnockitic rocks including the sahli granite ages of ca 2450 ma are also common from the other two tectonic windows to the sask craton suggesting that emplacement of the igneous suite was widespread and perhaps part of the coeval matachewan igneous event the absence of rocks in the 2960 and ca 2450 ma age ranges on both the adjacent superior and rae hearne cratonic margins makes it improbable that the sask craton was derived by simple fragmentation without large scale tectonic transport the overthrust paleoproterozoic rocks represent a high grade northwestern extension of the flin flon volcanic belt and include 1856 ma leucotonalite and 1843 ma quartz monzodiorite an 1830 ma suite of homogeneous calc alkaline enderbitic rocks which intrude burntwood semipelitic migmatites throughout the kisseynew domain has also been emplaced in mylonites of the pelican decollement zone zircon and monazite ages in the 1812 1803 ma range record a high grade metamorphic event that resulted from collision between the sask craton and flin flon glennie complex

how flakes shatter a critical evaluation of quartz fracture analysis despite its worldwide use as a stone tool raw material quartz is known to be a difficult material for archaeologists the main reason for this is the tendency of quartz flakes to fragment during detachment which complicates the use of traditional lithic analyses in this article we present an experimental study of quartz flake fragmentation we evaluate the method called fracture analysis that has been developed and used explicitly for the study of quartz assemblages the method assumes high predictability of quartz flake fragmentation but our experiments show that there is significant variation in fragmentation that fracture analysis does not take into account our results indicate that this variation is partly explained by indenter hardness the relative thickness of the detached flake as well as individual knapper related factors these results undermine the applicability of quartz fracture analysis in its current form in addition we discuss the effects of flake fragmentation on the technological organisation of prehistoric quartz users and suggest that it has affected reduction strategies as well as blank and tool dimensions we also suggest that there should be mobility related differences in archaeological assemblages in terms of the quality of the quartz raw material and that the curation of quartz should be low in relation to better quality raw materials used parallel with it

vein quartz in lithic traditions an analysis based on experimental archaeology abstract worldwide vein quartz was a commonly used raw material for stone tools but this material has proved difficult for archaeologists to analyse because many quartz assemblages appear to be comprised of amorphous pieces not easily recognised as humanly modified or forming tools this paper discusses the analysis of the debitage focusing on the debitage fragmentation rate the debitage break and fragment types and the quantitative analysis of the complete flakes resulting from experimental knapping of quartz which formed part of a project which investigated the use of quartz in irish prehistoric lithic traditions the results have highlighted the complexity involved in analysing quartz assemblages and the significant differences between the debitage products of quartz and chert knapping assemblages while bipolar knapping is generally easy to differentiate from direct percussion it is harder to differentiate between soft and hard hammer percussion

paleovegetation changes accompanying the evolution of a riverine system at the bk paleoanthropological site upper bed ii olduvai gorge tanzania abstract paleovegetation studies are essential to ecologically frame hominin evolution the analysis of the phytolith content of 22 paleosol samples collected along the vertical sequence of the channel containing the bk bell s korongo archaeological levels provided evidence of the paleovegetation that accompanied the evolution of the riverine system that formed this site 1 353 million years ago when climate was particularly arid the analysis reveals the abundance of forest indicator phytoliths 46 to 92 of the assemblages rare grass silica short cells and sedges phytoliths up to 15 of assemblages and palms up to 10 of the phytolith assemblages the vegetation of the bk fluvial system was therefore characterized by abundant woody plants it did not vary significantly diachronically in the period of time under scrutiny the alluvial paleovegetation corresponds well to the fluvial dynamic that formed bk including the presence of sterile samples recovered in areas where the water traction changed the soils frequently this spot of dense paleovegetation together with the fluvial watercourse in a paleolandscape likely dominated by sparse open vegetation could have been attractive seasonally for animals and hominins

occurrence composition and origin of analcime in sedimentary rocks of non marine petroliferous basins in china abstract natural analcime a highly brittle aluminosilicate mineral that dissolves easily during diagenesis occurs in the sedimentary rocks of eight main non marine petroliferous basins in china this mineral has been well documented for the past 30 years and has proved to be significant for the formation of high quality hydrocarbon reservoirs the present study fully reviews analcime occurrences chemical compositions si al ratios origin and controlling factors and influence on the hydrocarbon reservoir quality in permian to paleogene sedimentary rocks previous research has shown that analcime is commonly distributed within argillaceous laminae l type occurs as intergranular cement c type replacement r type and crack filling f type forms or is closely intergrown with other authigenic exhalative minerals a type analcime in lacustrine basins is slightly al rich and na poor and its si al ratios range from 1 95 to 2 80 the geochemical compositions of the analcime and ankerite bearing exhalites are characterised by enrichment in light rare earth elements and 13c and depletion in heavy rare earth elements and 18o with negative eu and positive ce anomalies diagenetic analcime forms by the alteration of volcanic glass clays or zeolite precursors in saline alkaline lakes or during buried diagenetic stages in sedimentary rocks in addition it coexists with other authigenic zeolite carbonate and clay minerals as well as albite hydrothermal analcime presumably precipitates from hydrothermal fluids and is not dependent on a local precursor mineral or volcanic glass this type is commonly related to exhalative mineralisation of hydrothermal springs the formation of natural analcime is controlled by various factors such as the composition of the parent material temperature prevalent during crystallisation chemistry of the fluid phase and thermodynamic characteristics of the geological environment as zeolites are formed in alkaline fluid phases they become unstable in acidic pore water secondary pores created by analcime mineral dissolution and intercrystalline micropores among analcime minerals are highly significant in hydrocarbon reservoirs analcime bearing mudstone siltstone dolostone and exhalite are favourable lithofacies for unconventional hydrocarbon accumulation owing to its high brittleness and selective dissolution of analcime and other associated minerals

experimental protocols for the study of battered stone anvils from olduvai gorge tanzania abstract percussive activities are highly relevant in the economy of modern hunter gatherer societies and other primates and are likely to have been equally important during the palaeolithic despite the potential relevance of percussive activities in the early stone age attempts to study battered artefacts are still rare in order to establish protocols of analysis of battered tools this paper pursues an interdisciplinary approach combining techno typological refit use wear and gis studies of experimental anvils from olduvai gorge tanzania the main aim is to classify types of damage on battered artefacts according to the percussive task performed and hence identify patterns that can be used to interpret the oldowan and acheulean evidence our results indicate that abrasion marks on anvil surfaces are typical of nut cracking while bone breaking leaves characteristic scars and abrasion marks on the edges of anvils pounding of soft materials such as meat and plants also causes battering of anvils producing morphological and spatial patterns that can be discerned from the heavy breakage of anvils during bipolar flaking by integrating macroscopic microscopic and spatial analyses of experimental stone tools this paper contributes to create a referential framework in which early stone age battered artefacts can be interpreted

pinwarian 1 50 ga volcanism and hydrothermal activity at the eastern margin of the wakeham group grenville province quebec volcanic belts developed along the southeastern continental margin of laurentia between 1 70 and 1 30 ga and subsequently metamorphosed at high grade are today largely concealed among gneiss complexes of the grenville province at the eastern end of the wakeham group and in the la romaine supracrustal belt to the east four 1 50 ga volcanic centres were found among gneissic synvolcanic intrusions typical of the 1 52 1 46 ga pinwarian continental magmatic arc upper amphibolite to granulite facies rhyolitic to dacitic lavas and coarse lapillistone overlie or are intimately associated with arenites typical of the wakeham group garnetite ironstone carbonate rock calc silicate rock and sillimanite bearing nodules veins and gneiss locally preserving lapilli are also present the distribution paragenesis and modes of most of these latter units differ from those of normal metasediments but are diagnostic of metamorphosed exhalites and hydrothermal alteration zones in the la romaine supracrustal belt

evidence for post 1200 ma pre grenvillian supracrustal rocks in the pinware terrane eastern grenville province at battle harbour labradorthis article is one of a series of papers published in this special issue on the theme of geochronology in honour of tom krogh u pb zircon geochronological investigations at battle harbour in the pinware terrane eastern grenville province show that a cross bedded psammitic rock from battle island was deposited after 1200 ma and prior to grenvillian orogenesis as part of a package of psammitic semi pelitic and calc silicate rocks this represents a major finding as no previous data had indicated any supracrustal rock deposition after ca 1500 ma in the interior eastern grenville province the age is comparable to that obtained from supracrustal units of minor extent elsewhere in the interior grenville province indicating that change in crustal level in these regions was modest during grenvillian orogenesis grenvillian metamorphism at amphibolite facies occurred at 1030 4 ma based on evidence from a concordant mafic rock within the supracrustal assemblage that is interpreted to be a sill grenvillian orogenesis at battle harbour was accompanied by abundant pegmatite injection over an extended period as indicated by cross

alteration processes of the roque nublo ignimbrites gran canaria canary islands abstract the non welded lithic rich ignimbrites of roque nublo are the most characteristic deposits of the second magmatic cycle pliocene in age on gran canaria they are very heterogeneous with 35 55 by volume of lithic clasts 15 30 of moderately vesiculated pumice 5 7 of crystals and 20 30 of ash matrix the juvenile components pumice fragments and ash matrix are largely altered the mineral assemblage that originated by the alteration of vitric components consists mainly of zeolites chabazite phillipsite and analcime and subordinate smectites the alteration does not show any lateral or vertical gradation in the deposits and does not change in intensity with respect to the distance from the emission center these alteration processes affect only the roque nublo ignimbrites their associated fall and surge deposits remain unaltered a geo autoclave mechanism is proposed to explain the alteration processes which devitrified the juvenile components of the roque nublo ignimbrites and gave the rocks their characteristic strong induration this implies that the eruptions which led to the formation of the roque nublo ignimbrites had an important phreatomagmatic component and that the resulting pyroclastic flows were too dense and too poorly expanded to permit the water vapour to be separated from the vitric fragments during transport the alteration took place in situ and immediately after the deposition of the deposits when they were still hot by the reaction between the vitric components and the condensed vapour and cannot be attributed to late diagenesis or weathering

microporosity development in shallow marine sediments from the nankai trough abstract i characterized microporosity by performing low pressure nitrogen adsorption measurements on 13 shallow marine mudstone samples from the nankai trough offshore japan the samples were from two reference sites on the incoming philippine sea plate and one site above the accretionary prism i determined pore size distributions using the barrett joyner hallenda bjh model and merged these with existing mercury injection capillary pressure micp measurements to construct a full distribution covering micro to macropores i found that overall pore sizes decrease with consolidation and that microporosity content pores ca 2 sr si show inconsistent relationships with microporosity development and cannot confirm or deny the role of ash alteration in this process the strongest correlation observed at the three sites was between microporosity volume and clay mineral fraction this suggests that microporosity content is determined mainly by detrital clay abundance and development of clay as an ash alteration product with some contribution from amorphous silica cement precipitated in the zones of anomalous high porosity

proterozoic southward accretion and grenvillian orogenesis in the interior grenville province in eastern labrador evidence from u pb geochronological investigations abstract this study is a fascinating example from the eastern grenville province of unraveling the triple challenges inherent in the geochronological investigation of any multi orogenic region namely inheritance emplacement and subsequent metamorphism the existence of hitherto unknown pre labradorian crust within allochthonous grenvillian terranes is demonstrated formerly unrecognized spatial relations between labradorian and pinwarian crust are outlined and a new perception of mid grenvillian magmatic and metamorphic events is presented the pre labradorian crust has an age range of 1800 1770 ma and consists of calc alkaline plutonic rocks intruding earlier supracrustal assemblages containing archean and early paleoproterozoic inherited zircons evidence is provided from dated enclaves and inheritance in younger rocks that similar aged pre labradorian crust once existed farther south the geochronologically defined geographic extent of early labradorian crust having a 1680 1655 ma age range is expanded this crust is intruded by the mid labradorian mealy mountains intrusive suite for which new results confirm its 1650 1630 ma time of emplacement pinwarian orthogneiss dated between 1513 and 1496 ma and previously unknown in the region is now recognized to be common sufficient data exist to define for the first time a boundary between labradorian and pinwarian orthogneiss cryptic in the field establishing the presence of pinwarian aged crust to the southwest lacking labradorian inheritance except close to the boundary a belt of layered mafic anorthositic and monzogranitic intrusions is situated close to the boundary current data favour a pinwarian age for emplacement of these rocks mid grenvillian plutonism is demonstrated by 1043 ma ages from two k feldspar megacrystic granodiorite bodies they are situated on either flank of a crustal scale northeast trending northeast closing fold the fold which is 40 km wide and at least 160 km long and exposes pinwarian orthogneiss in its core post dates emplacement of the 1043 ma intrusions the fold probably formed at the peak of grenvillian tectonism in the region between 1030 and 1015 ma and certainly before intrusion of weakly deformed granitoid rocks at 992 ma final activity included the emplacement of late to post grenvillian granitoid plutons between 964 and 951 ma a pluton having a 951 ma age is the youngest known in the eastern grenville province cooling and stabilization was completed by ca 940 ma broader implications of the results in conjunction with existing data are that i the northeasternmost part of the eastern grenville province was only peripherally affected by grenvillian orogenesis ii an east northeast offshore extrapolation of the grenville front as a major tectonic feature does not exist iii high grade metamorphic mineral assemblages in the groswater bay and hawke river terranes are pre grenvillian rather than an eastward expression of a grenvillian high pressure belt and iv the north shore of the eastern st lawrence estuary represents across orogen exposure rather than orogen parallel as previously supposed

great salt lake and precursors utah the last 30 000 years sediment cores up to 6 5 m in length from the south arm of great salt lake utah have been correlated radiocarbon ages and volcanic tephra layers indicate a record of greater than 30 000 years a variety of approaches have been employed to collect data used in stratigraphic correlation and lake elevation interpretation these include acoustic stratigraphy sedimentologic analyses mineralogy geochemistry major element c o and s isotopes and organics paleontology and pollen the results indicate that prior to 32 000 year b p an ephemeral saline lake playa system was present in the basin the perennial lake which has occupied the basin since this time rose in a series of three major steps the freshest water conditions and presumably highest altitude was reached at about 17 000 year b p the lake remained fresh for a brief period followed by a rapid increase in salinity and sharp lowering in elevation to levels below that of the present great salt lake the lake remained at low elevations and divided at times into a north and south basin until about 8 000 year b p since that time with the exception of two short rises to about 1290 m the lake level has remained near the present elevation of 1280 m

clay mineral assemblages and analcime formation in a palaeogene fluvial lacustrine sequence maiz gordo formation palaeogen from northwestern argentina abstract the palaeogene maiz gordo formation is one of the main lacustrine events recorded in northwestern argentina it consists of sandstone mudstone and limestone beds 200 m thick deposited in a brackish alkaline lake and braided alluvial systems the maiz gordo lake evolved mainly as a closed system with brief periods as an open one x ray diffraction xrd and scanning electron microscopy sem were used to study samples from seven sites corresponding respectively to proximal intermediate and transitional positions of the fluvial environment and marginal and inner lake environment focusing on the clay mineralogy and analcime formation the basinward zonation of diagenetic minerals identified in the maiz gordo lake was mordenite analcime k feldspar although not a typical zonation of saline alkaline lakes it does indicate an increase in salinity and alkalinity towards the centre in proximal fluvial settings smectite predominates at the base of the sequence with scarce kaolinite towards the top a striking increase in kaolinite content suggests a change from a relatively arid climate with alternating humid and dry seasons towards a warm and humid climate kaolinite content clearly decreases in a basinward direction such a variation is attributable to changes in hydro geochemistry denoting the progressive influence of the brackish and alkaline lake water on interstitial pores sem images of intermediate fluvial samples reveal authigenesis of illite at the expense of kaolinite booklets in littoral and inner lake settings the clay fraction is composed of muscovite sometimes with subordinate smectite analcime occurs in variable amounts in all sedimentary facies in rock pores or filling veins it forms subhedral square to hexagonal or anhedral rounded crystals denoting that they coarsened at low to moderate degrees of supersaturation although the mordenite identified in a fluvial level would have been the precursor of analcime in the maiz gordo basin no textural evidence of analcime formation through replacement of mordenite or other precursor zeolite was found hence it is more probable that analcime formation took place by direct authigenic precipitation or through the reaction between interstitial brines and clay minerals or plagioclase

climatic signals in lacustrine deposits of the upper yacoraite formation western argentina evidence from clay minerals analcime dolomite and fibrous calcite

hydrothermal alteration associated with the chicxulub impact crater upper peak ring breccias abstract the 66 ma 180 km chicxulub impact structure in the northern yucatan peninsula and southern gulf of mexico is the best preserved large impact crater on earth with a well developed peak ring the most recent drilling campaign took place offshore during the joint international ocean discovery program international continental scientific drilling program iodp icdp expedition 364 at site m0077a 21 45 n 89 95 w and recovered 830 m of continuous core initial examination revealed that the peak ring comprises four main lithological units from the base upwards crystalline basement granitoid rocks unit 4 a thin layer of impact melt rocks units 3a and b melt bearing breccias units 2a c and post impact sedimentary rocks unit 1 preliminary analysis of the drill core indicated that hydrothermal alteration has affected all lithologies and is especially pervasive in the melt bearing breccias of unit 2 721 6 to 617 33 meters below sea floor mbsf here we present the first detailed investigation of hydrothermal alteration within the melt bearing breccias alteration phases are predominantly fe mg clay minerals zeolites alkali feldspars calcite and minor sulfides sulfates opal and fe ti oxides alteration is especially intense proximal to lithologic contacts particularly at the base of subunit 2b where there is an abrupt increase in host rock porosity 30 m above the impact melt rocks the pervasiveness of clay minerals and zeolites is attributed to the high amounts of devitrified silicate glass throughout unit 2 the phases preserved here are consistent with the findings of previous hydrothermal studies in other areas of the chicxulub structure and suggest an evolving water rock system that was alkaline saline comparable to seawater volcanic glass alteration

jurassic lake t oo dichi a large alkaline saline lake morrison formation eastern colorado plateau a large alkaline saline lake lake t9oo9dichi9 occupied the entire eastern part of the colorado plateau region during deposition of the brushy basin member of the upper jurassic morrison formation the lake extended from near the site of albuquerque new mexico to near the site of grand junction colorado and occupied a region that encompassed the san juan and ancestral paradox basins making it the largest ancient alkaline saline lake known the lake was typically shallow and frequently evaporated to dryness although the water table was probably never far beneath the surface intermittent streams carried detritus from source areas to the west and southwest far out into the lake basin a reflection of a low depositional gradient and the ephemeral nature of the lake prevailing westerly winds carried silicic volcanic ash to the lake basin from an arc region to the west and southwest a lateral hydrogeochemical gradient characterized by increasing salinity and alkalinity from the margin of the lake to the center developed in pore waters of the lacustrine sediments and resulted in alteration of the ash to a variety of authigenic minerals that define concentric zones within the lake basin the basinward progression of diagenetic mineral zones is smectite clinoptilolite analcime potassium feldspar albite a concomitant lateral zonation of mixed layer illite smectite developed from highly smectitic in the outermost zones to highly illitic in the central zone authigenic albite and illitic mixed layer clay minerals previously thought to require elevated temperatures for formation crystallized during early diagenesis at syndepositional temperatures in the lacus trine sediments of lake t9oo9dichi9 this study presents evidence for a syndepositional origin for both of these minerals these findings have important implications in terms of limiting the use of these minerals as geothermometers recognition of alkaline saline lake deposits in the morrison formation significantly alters interpretations of depositional environments of this formation and it also has important implications for paleoclimatic interpretation late jurassic climate was apparently much more and than had previously been thought in fact sedimentologic evidence suggests that the lake basin was typically dry for extended periods and enjoyed only brief wet intervals this conclusion has important consequences for environmental interpretation of the habitat that was favorable for large herbivorous dinosaurs which thrived in the late jurassic

original sediment composition of the lower cretaceous lacustrine tight oil mudstone and influences on diagenesis and organic matter content the erennaoer sag in erlian basin ne china abstract the original sediment composition is of great value to providing an understanding of depositional environment and hydrocarbon generation potential but it is easily altered by diagenesis and difficult to recognize in this study we examine carbonate rich tight oil mudstones of the lower cretaceous arshan formation in the erennaoer sag of the erlian basin as an example based on analyses of mineralogy stable carbon and oxygen isotopes and trace rare earth elements the original composition of the arshan mudstones has been reconstructed results show that the original arshan mudstone composition was mainly siliciclastic detritus tuffaceous and clay matrix which has a major impact on diagenesis and organic matter content the erupted volcanic ashes were beneficial to the introduction of nutrients an increase in biomass and an associated increase in to the preservation of organic matter which has been suggested by an improvement of toc of arshan tuffaceous mudstones with average contents of 2 82 the volcanic ashes in the studied mudstones had also enhanced methanogensis during the shallow burial additionally the early alteration products of authigenic minerals include analcime or zeolite most of which is entirely altered to analcime and chlorite the formation of major eogenetic carbonate cements include early dolomite and calcite which were related to volcanic materials and methanogenesis at shallow depths

occurrence of analcime in the middle jurassic coal from the dongsheng coalfield northeastern ordos basin china abstract this paper describes the occurrence of significant authigenic analcime naalsi2o6 h2o in the middle jurassic coal from the northeastern ordos basin and discusses its origin twelve coal samples from borehole zk31 19 in the dongsheng coalfield were collected and analyzed the coals are characterized by a low medium ash yield high volatile matter and low sulfur contents the major element oxides in the studied coals are mostly at similar or much lower concentrations compared to the averages for chinese coals similarly most trace elements are depleted or in concentrations close to the respective averages for world low rank coals based on seredin dai s classification the rey rare earth elements and y in the coal mainly display n and h type distribution patterns with no ce and eu anomalies coal sample zk31 19 12 from the lower zhiluo formation contains analcime up to 23 wt with a high na2o concentration of 1 23 both on a whole coal basis the analcime occurs as lath as subhedral granular crystals in fissures or pores and as anhedral crystals in the organic matrix furthermore significant analcime has also been observed by sem in coal from the upper yan an formation sample zk31 19 10 which mainly occurrs as anhedral crystals no evidence of analcime forming from precursors of volcaniclastic material alkali zeolites or other silicates was detected therefore it is deduced that the analcime in the studied coals formed by authigenic precipitation the na2o content in the studied coal seams displays a vertical variation different from that of the ash yield ad and those of the detrital dominated elements such as sio2 al2o3 tio2 zr nb and th indicating a different origin of na compared with other detrital materials of terrigenous origin combined with the evidence of the obvious na peak in authigenic amorphous material and gypsum mineral by sem it can be inferred that the source of na may derive from the fluids the paleoclimatic change from subtropical warm and humid to semi arid and arid hot during the deposition period of the yan an to the zhiluo formation may provide favorable conditions for analcime authigenesis leading to its abundant precipitation in the lower zhiluo formation and its limited occurrence in the upper yan an formation such paleoclimatic change is also significant for the u mineralization in the lower zhiluo formation

zeolites in closed hydrologic systems zeolites were first described from vugs and fissures in basaltic flows in the mid eighteenth century cronstedt 1756 and they are now known to be widespread in a variety of geological environments more zeolite species occur in vesicles and fractures of basaltic rocks than in any other geologic setting however zeolites from sedimentary rocks in particular represent the most important occurrences both in terms of aerial extent of deposits and in terms of the abundance of certain zeolite species the introduction of new analytical techniques in the latter part of the 20th century provided a significant stimulus to zeolite research these techniques allowed identification of large quantities of zeolites in widespread deposits of sedimentary rocks and in particular in sediments from saline alkaline lakes of the western united states sheppard and gude 1968 1969a 1973 based on geological and hydrologic environments zeolite occurrences in sedimentary rocks can be classified in the following framework a saline alkaline lakes b alkaline soils and land surfaces c deep sea sediments d open hydrologic systems e as products of hydrothermal alteration and f burial diagenetic or low metamorphic environments from a broader perspective zeolite deposits can be classified into two main groups namely closed hydrologic systems and open hydrologic systems the work of sheppard and gude 1968 1969a 1973 and later surdam 1977 discussing not only the mineralogy of the deposits but also the geology hydrology and chemistry of the depositional basins represent milestones in the study of closed hydrologic system formation of zeolites surdam 1977 considered closed hydrologic basins in two different tectonic settings a block faulted regions in arid and semiarid regions and b trough valleys associated with rifting examples of the first setting are the closed lakes of the basin and range province of the western united states whereas the

lithic raw material quality of middle pleistocene artefacts from the han river danjiangkou reservoir region central china abstract the east asian acheulean is often considered distinct from african and european acheulean technologies as large cutting tools lcts are thicker and heavier on average this distinction is generally true but exceptions occur particularly in thickness as more chinese sites are reported it has been suggested that the raw materials available in east asia have played a part in determining this dissimilarity extensive raw material studies on east asian technologies have not yet been done to determine if this is indeed the case it is thus important to investigate the impact of raw materials quality on the east asian acheulean this paper focuses on raw material attributes for lcts from the danjiangkou reservoir region central china drr with specific focus on middle pleistocene artefacts from terrace 3 of the han river extensive experimental studies were done to determine raw material attributes and how those attributes affect the knapping process in the creation of lcts a set of variables was recorded for the experimental tools and compared with a sample of archaeological lcts the variables recorded included the impurity encounter rates of various raw materials their weathering states grain sizes and shapes the results indicated that hominids occupying the drr exhibited selective behaviours for the raw materials they used to make lcts despite not having a wide variety of materials from which to select it is also evident that they showed adaptability and made strategic decisions with regards to the selected raw materials for manufacture of lcts to meet their needs

hydrothermal minerals and alteration rates at surtsey volcano iceland the volcanic island surtsey off the south coast of iceland was created by volcanic activity in 1963 1967 core from a 181 m deep hole extending 123 m below sea level shows the results of 12 yr of hydrothermal alteration of basaltic tephra the primary cause of heating of the tephra and of development of the hydrothermal system was the intrusion of dikes below sea level at present the hottest part of the hole at a maximum temperature of 150 c is cooling at 0 9 c per year palagonitization of sideromelane glass a dominant constituent of the tephra is an important alteration process that is strongly temperature dependent the rate doubling for every 12 c increase at 60 c 90 is palagonitized above 120 c olivine crystals are replaced on their edges by nontronite the thickness of clay doubles for each 8 c increase ten hydrothermal minerals have crystallized in the tephra at 25 to 150 c the dominant species are smectite nontronite analcite phillipsite and tobermorite the primary clay species of palagonite is probably nontronite other minerals are halite opal calcite chabazite xonotlite anhydrite and gypsum no major differences in mineral occurrence are noted above and below sea level but phillipsite and tobermorite tend to grow larger below sea level even at the same temperature analcite appears at lower temperature 55 c above sea level than below sea level 75 c anhydrite is most abundant deep in the hole where inflowing cool sea water precipitated sulfate due to reduced sulfate solubility at higher temperatures

diatom paleolimnology of late pliocene baringo basin kenya paleolakes abstract kenya s baringo tugen hills barsemoi drill site is one of six localities across kenya and ethiopia from which the hominin sites and paleolakes drilling project has obtained sediment cores in an effort to investigate the role of environmental forcing in shaping human evolution the baringo basin site features extensive exposures of the chemeron formation which contains 100 fossil vertebrate localities including five hominin sites the 228 m drill core dating from 3 29 to 2 56 ma is characterized by fluvio lacustrine sediments including multiple diatomites with evidence of variable degrees of later pedogenic modification in the lower part of the core 3 29 3 04 ma diatoms were preserved only in very low abundance consistent with predominantly fluvial or lake marginal environments in contrast five diatomites and two additional diatom rich intervals were deposited after 3 04 ma reflecting a major shift in the basin hydrology planktonic freshwater species dominated these diatom rich intervals whereas periphytic taxa were present in proportions less than 2 suggesting that these intervals represent open water deposition during lake highstands littoral or saline assemblages are largely absent throughout the core instead we observed a pattern of increasing diatom frustule dissolution at the tops and bottoms of diatomite units indicating increased alkalinity during the transgressive regressive phases a na bearing zeolite analcime indicative of saline waters precipitated in clastic dominated intervals between diatomites suggesting extreme environmental variability between lake highstands and lowstands diatom assemblages were consistently dominated by a few species belonging to the genera aulacoseira and stephanodiscus which were at times co dominant we infer that assemblages dominated by aulacoseira represent a well mixed lake with abundant supply of silica when stephanodiscus was dominant which occurred more frequently in the later freshwater phases we infer incomplete mixing and reduced silica flux to the epilimnion upper water layer

dating ductile deformation using u pb geochronology examples from the gilbert river belt grenville province labrador canada the gilbert river belt in the grenville province in southeastern labrador is a distinctive west northwest trending zone of locally intense deformation and voluminous granitoid plutonism up to 30 km in width in an attempt to directly quantify the timing of deformation in ductile shear zones within the belt rocks interpreted as having been intruded synchronously with ongoing deformation were sampled for u pb isotopic analysis three of these samples are 2 m wide granitic veins that have sharp intrusive contacts that truncate ductile deformation fabrics but are themselves deformed at metamorphic conditions similar to their host rocks and are therefore interpreted as having intruded after the initiation of deformation and fabric development but prior to cessation of this deformation the first vein is syntectonic with respect to amphibolite facies deformation and yielded a zircon age of the second vein intruded synchronously with the development of a zone of amphibolite facies straight gneisses wh

composition and thermal inertia of the mawrth vallis region of mars from tes and themis data abstract clay mineral bearing deposits previously discovered on mars with near infrared 0 3 5 m remote sensing data are of major significance for understanding the aqueous history geological evolution and past habitability of mars in this study we analyzed the thermal infrared 6 35 m surface properties of the most extensive phyllosilicate deposit on mars the mawrth vallis area clay mineral bearing units which in visible images appear to be relatively light toned layered bedrock have thermal inertia values ranging from 150 to 460 j m 2 k 1 s 1 2 this suggests the deposits are composed of a mixture of rock with sand and dust at 100 meter scales dark toned materials that mantle the clay bearing surfaces have thermal inertia values ranging from 150 to 800 indicating variable degrees of rockiness or induration of this younger sedimentary or pyroclastic unit thermal emission spectrometer tes spectra of the light toned rocks were analyzed with a number of techniques but none of the results shows a large phyllosilicate component as has been detected in the same surfaces with near infrared data instead tes spectra of light toned surfaces are best modeled by a combination of plagioclase feldspar high silica materials similar to impure opaline silica or felsic glass and zeolites we propose three hypotheses for why the clay minerals are not apparent in thermal infrared data including effects due to surface roughness sub pixel mixing of multiple surface temperatures and low absolute mineral abundances combined with differences in spatial sampling between instruments zeolites modeled in tes spectra could be a previously unrecognized component of the alteration assemblage in the phyllosilicate bearing rocks of the mawrth vallis area tes spectral index mapping suggests that fe mg clays detected with near infrared data correspond to trioctahedral fe2 clay minerals rather than nontronite like clays the average mineralogy and geologic context of these complex interbedded deposits suggests they are either aqueous sedimentary rocks altered pyroclastic deposits or a combination of both

lower paleolithic bipolar reduction and hominin selection of quartz at olduvai gorge tanzania what s the connection abstract numerous researchers have noted that at lower paleolithic sites in east africa hominins largely exploited quartz toolstone with the bipolar reduction technique the choice to pursue bipolar knapping on quartz is often attributed to raw material constraints thus at some east african lower paleolithic sites the abundance of bipolar knapping may have simply constituted a response to the local absence of lithic resources other than small quartz pebbles however at olduvai gorge tanzania where a variety of other stone raw materials were available the hominin use of bipolar reduction is still predominately tied to quartz while quartz raw material constraints may explain the use of bipolar reduction on quartz at olduvai what they do not explain is the virtual absence of bipolar reduction on non quartz toolstones thus we ask here two separate but related questions 1 why did hominins use bipolar on quartz and 2 why did hominins avoid bipolar on non quartz to begin to understand this tight technology toolstone connection we formulated two simple hypotheses which we tested via experimental stone tool replication 1 quartz bipolar reduction produces flakes that possess superior functional characteristics to those produced via non quartz bipolar reduction 2 bipolar reduction is more expedient on quartz than on non quartz toolstones our experimental tests indicated that while quartz and basalt bipolar reduction yield flakes with similar attributes bipolar reduction on quartz is significantly more expedient than it is on basalt as such the close technology toolstone association between quartz and bipolar can be explained by constraints and advantages of both quartz and basalt alike bipolar reduction is already widely acknowledged to be an expedient technology requiring little to no skill by applying bipolar reduction exclusively to quartz hominins at olduvai appear to have only enhanced this reduction strategy s features overall our experimental results are consistent with the widely held notion that lower paleolithic hominins recognized the differences in the physical properties of different types of raw material and that it is the interplay between raw material and reduction strategy that governed hominin association between bipolar reduction and quartz at olduvai

occurrence of zeolites in sedimentary rocks an overview zeolites have been known since the mid 1750s but prior to the early 1950s most reported occurrences of zeolites were in fracture fillings and amygdules in igneous rocks particularly basaltic lava flows indeed most of the large attractive zeolite specimens in museum collections were obtained from lavas in recent years zeolites have been recognized as important rock forming constituents in low grade metamorphic rocks and in a variety of sedimentary rocks most zeolites in sedimentary rocks are finely crystalline that is they occur as microscopic or submicroscopic crystals and they are therefore of little appeal to mineral collectors however deposits of this type are voluminous and have great geologic significance and economic potential zeolites are among the most common authigenic silicate minerals that occur in sedimentary rocks and they form in sedimentary rocks of diverse lithology age and depositional environment about twenty species of zeolites have been reported from sedimentary rocks but only eight zeolites commonly make up the major part of zeolitic rocks these are analcime chabazite clinoptilolite erionite heulandite laumontite mordenite and phillipsite this chapter will consider chiefly the zeolites in sedimentary rocks with emphasis on volcaniclastic deposits which contain the largest concentrations of zeolites the occurrence of zeolites in lava flows is mentioned only briefly journal articles on the occurrence and origin of natural zeolites have multiplied at a rapid rate since the mineralogy and geology of natural zeolites was first published in 1977 as volume 4 of the mineralogical society of america s reviews in mineralogy the present review will highlight areas of more recent research on the occurrence and origin of zeolites and some of the coexisting minerals a wide variety of zeolites has been identified in sedimentary deposits with the most common being clinoptilolite analcime heulandite laumontite and phillipsite less abundant zeolites include chabazite erionite mordenite natrolite