a systematic comparison of obsidian hydration measurements the first application of micro image with secondary ion mass spectrometry to the prehistoric obsidian abstract archaeologists have long used obsidian hydration dating method to give chronometric dates for obsidian artifacts models using these equations independently employ different measurement systems which are based on rim thicknesses determined by optical microscope and hydrogen depths measured by secondary ion mass spectrometry sims respectively although the inconsistency of both measurements has been reported firstly this paper describes a systematic comparison that was done on optical rim thicknesses and hydrogen depths by means of an isotope microscope which provides micro imaging with sims depth profiles of hydrogen were precisely obtained from the spots where optical measurements were taken on the archaeological obsidian flakes from two distinctive cultural horizons older upper paleolithic younger initial jomon in the stratified open air site of jozuka in southern kyushu japan secondarily using the measurements of hydrogen depths that are the most consistent to the measurements of optical thicknesses the estimated hydration rate of the holocene initial jomon is slower than that of the late pleistocene upper paleolithic implying that the difference in hydration rates was due to the difference of intrinsic water content of obsidian and or obsidian geochemistry an application of micro imaging with sims to measure hydrogen depths on obsidian shows promise as a tool for improving the practice of hydration dating and evaluating local climatic condition

sources and occurrence of c12c22n alkane distributions with even carbon number preference in sedimentary environments abstract the occurrence of c12 c22n alkanes with a strong even carbon number preference is reported in recent and miocene sediments encompassing marine and freshwater systems deposited under oxic and anoxic conditions it is therefore shown that these n alkanes can be found in a wider type of sedimentary environment than those previously described the occurrence in some cases of a parallel distribution of c14 c20n alk 1 enes is also illustrated a variety of biological sources including both marine and freshwater bacteria as well as fungi and yeast species is suggested to account for such distributions

obsidian hydration dating accuracy and resolution limitations imposed by intrinsic water variability obsidian hydration dating typically yields a range of ages for a single chronometric measurement even after controlling for source chemistry and effective hydration temperature previously published data suggest that this range is due to hydration rate variations caused by variability in the concentration of intrinsic water and specifically hydroxyl ions in the obsidian such variability exists within any given obsidian source and even within any particular specimen this paper analyzes the effect on age estimates of intrinsic water variability and concludes that if a controlled sample of obsidian yields a range of ages there is no way to tell whether the range is due to long site use or to variations in hydroxyl concentration at present there is no robust and cost effective protocol for measuring hydroxyl concentration suggested guidelines for obsidian hydration dating are developed using a case study these findings do not invalidate obsidian hydration as a chronometric technique but they do suggest limits to the temporal resolution achievable

tectonic evolution of the japanese island arc system abstract growth of the japanese arc system which has mainly taken place along the continental margin of asia since the permian is the result of subduction of the ancient pacific ocean floor backarc basin formation in the tertiary shaped the present day arc configuration the neotectonic regime which is characterized by strong east west compression has been triggered by the eastward motion of the amur plate in the quaternary the tectonic evolution of the japanese arc system includes formation of rock assemblages common in most orogenic belts because the origin and present day tectonics of these assemblages are better defined in the case of the japanese arc system study of the system provides useful insight into orogenesis and continental crust evolution

obsidian hydration at high elevation archaic quarrying at the chivay source southern peru we examine obsidian hydration as a means to date archaeological sites at high elevation in the central andes and in particular quarry sites that are difficult to date by radiocarbon means the chivay obsidian source lies in a volcanic depression above the colca valley in arequipa peru 71 5355 s 15 6423 e at 4950 masl we compare obsidian hydration readings from one quarry and two workshop locations ninety one flakes from the quarry pit and 61 and 33 flakes from the workshops were analyzed for hydration bands of these 68 from the quarry and 54 and 33 respectively from the workshops produced at least one culturally meaningful hydration band as expected obsidian appears to hydrate slowly at this high elevation yet variation in hydration readings is low within stratigraphic contexts suggesting relatively narrow windows of knapping activities in each excavation level a small number of radiocarbon dates allow us to develop a preliminary hydration rate for chivay obsidian in this high elevation location hydration data indicate that intensive quarrying began by 3800 cal bc and stopped ca 2300 cal bc by contrast the two workshops appear to have been deposited 2900 and 1200 cal bc and 2700 and 2400 cal bc the data are consistent with an uptick in obsidian use by at least the terminal archaic period 2011 elsevier ltd all rights reserved

hydrothermal petroleum genesis migration and deposition in guaymas basin gulf of california hydrothermal activity and seabed mounds have been explored in guaymas basin by the deep sea drilling project dsdp piston coring dredging and diving with the deep submersible research vessel dsrv alvin sedimentary organic matter derived primarily from immature degraded microbial detritus is easily converted to petroleum under the hydrothermal regime these petroleums are mature and migrate in the fluids and by diffusion to the seabed the fluid migration is aided by near critical aqueous solution and supercritical carbon dioxide and hydrocarbons petroleum compositions vary from condensates to naphthenic to waxy all with significant amounts of asphaltenes and hydrothermal products such as olefins and toxic polynuclear aromatic hydrocarbons pah the heavy ends condense at the seabed depositing mainly as a cement with the sulfides and other minerals and to a lesser extent as entrapped oil and crystalline wax in vugs and conduits of the mounds the pah are high temperature resynthesis aromatiza

terminal proterozoic mid shelf benthic microbial mats in the centralian superbasin and their environmental significance abstract a combined sedimentological and biogeochemical study has been conducted on several terminal proterozoic mid shelf microbial mat facies from the centralian super basin isotopic and organic geochemical analysis of the bitumen and kerogen indicated that two sources of organic matter from planktonic and benthic microbial mat populations contributed to the sediment the planktonic source provided a suite of n alkanes with c20 whereas the benthic source contributed an overlay of n alkanes c20 with a strong even preference together with mid chain methyl alkanes kerogen and biomarkers derived from the microbial mat were found to be depleted in 13c relative to planktonic material pyrite in the micorbial mats was also found to be depleted in 34s compared to surrounding facies the combination of these observations suggested that the mats may have been at least partly composed of sulfide oxidising bacteria these organisms have specific environmental tolerances that set limits on palaeo environment their requirement for oxygen indicates that the water column above the mid shelf could not have been anoxic accordingly from the results and age determinations reported here it would appear that mid shelf environments of the centralian superbasin of australia were seeing significant levels of oxygen through the ediacarian

saturated hydrocarbon biomarkers in oils of late precambrian age from eastern siberia abstract large quantities of petroleum derived from source rocks of late precambrian early cambrian age have been discovered in the lena tunguska region of eastern siberia over the last twenty five years we have examined three oils with presumed late precambrian vendian source rocks from this region for c 15 saturated hydrocarbon biomarkers using gas chromatography gc and gas chromatography mass spectrometry gc ms our results show these oils to have many characteristics in common with other oils of similar age from eastern siberia and oman amongst the compounds detected in the three oils analyzed were 1 n alkanes which show a marine derived distribution 2 centrally branched monomethyl alkanes 3 acyclic isoprenoids pr ph 1 4 tricyclic and tetracyclic terpanes 5 hopanes 6 c 29 unrearranged steranes and 7 c 30 nuclear steranes all of these compounds with the exception of the 4 methylsteranes which on current biochemical knowledge are unexpected in oils of this age can be assigned a prokaryotic source this and other evidence such as the lack of diasteranes suggest microorganism were the major contributors to organic matter deposited as part of a carbonate source rock

unusual normal alkane distributions in offshore new zealand sediments the occurrence of unique even carbon dominated normal alkanes in sediment extracts was confirmed in sediments from the eastern continental shelf offshore of north island new zealand in hawke bay the range in carbon chain lengths was from n c16 to least n c36 extending distributions well beyond the previously reported 24 carbons stable isotope analysis of individual alkanes suggest an independent origin for the odd and even n alkanes it is suggested that sedimentary even number n alkane predominances are more widespread than previously thought but go unrecognized due to substantial overprinting by terrestrial derived odd carbon number n alkanes

first indications of the formation of kerogen amorphous fractions by selective preservation role of non hydrolysable macromolecular constituents of eubacterial cell walls abstract two marine kerogens supposed to contain an important bacterial component were analysed and their spectroscopic and pyrolytic features compared with those of the amorphous non hydrolysable macromolecular materials bacterans isolated from extent bacteria examination by transmissio electron microscopy revealed that dontrien lower toarcian shales paris basin is essentially composed of amorphous organic matter and osb3 marl slate formation n e england is exclusively amorphous the formation upon kerogen pyrolysis of series of products 3 methylalkanes dimethylalkanes ethylesters and alcohols characteristic of bacteran pyrolysates is consistent with the contribution of bacterans to the formation of these two kerogens the nature and distribution of the acids of the pyrolysates indicate that bacterial biomass was implicated in osb3 and dontrien kerogen formation via two pathways bacteran selective preservation and incorporation of partly degraded lipids comparison between dontrien and osb3 indicates a weaker contribution of the selective preservation pathway to osb3 kerogen whereas bacteria lipid incorporation may have been more significant in osb3 kerogen the selective preservation pathway was so far considered as restricted to the formation of kerogens having retained some of the morphological features of the source organisms an important point derived from this study is therefore the ability of this pathway to also contribute to the formation of amorphous kerogens

origin of free and bound mid chain methyl alkanes in oils bitumens and kerogens of the marine infracambrian huqf formation oman the huqf oil from oman and other time equivalent oils are characterized by relatively large contents of mid chain branched monomethyl alkanes the huqf oil the saturated hydrocarbon fractions the desulfurized polar fractions of the bitumens and the kerogen pyrolysates of three potential source rocks from the huqf formation oman were analyzed in order to resolve the origin of these mid chain branched monomethyl alkanes using off line pyrolysis and chemical degradation in combination with compound specific carbon isotope analysis it was assessed that the mid chain branched monomethyl alkanes are not rearrangement products but are derived from a biological source probably from lipids with c28 carbon skeletons and methyl branching at the 12 or 13 position these compounds were incorporated in the kerogen through reactions of sulfur with functional groups at different positions in the precursor lipid s

reasserting the utility of obsidian hydration dating a temperature dependent empirical approach to practical temporal resolution with archaeological obsidians in a recent paper in this journal anovitz et al 1999 identify potentially serious flaws in the measurement and modelling of obsidian hydration for dating archaeological obsidians this critique follows other recent papers highlighting potential problems with the method e g ridings 1996 stevenson mazer scheetz 1998 contrary to this latest critique the current paper offers evidence for the apparent efficacy of a quadratic model for obsidian hydration dating of archaeological obsidians using empirical results from archaeological projects throughout the western united states it is posited that this model is sufficient in part due to limits of commonly used methods of hydration analysis which also provide a cost effective means for large scale sampling given apparent support for quadratic modelling and hence the diffusion theory underlying it an empirical approach to obsidian hydration rate formulation that incorporates field temperature data is explored although evaluation of the resulting rate formula for casa diablo obsidian is somewhat equivocal the results are relatively robust when compared to other posited rates as such the approach appears to hold promise within the limits of temporal resolution necessary for many regional research strategies while also serving as a potential check of laboratory based strategies

alkaline permanganate oxidation of kerogens from cretaceous black shales thermally altered by diabase intrusions and laboratory simulations abstract potassium permanganate oxidative degradations were conducted for kerogens isolated from cretaceous black shales dsdp leg 41 site 368 thermally altered during the miocene by diabase intrusions and from unaltered samples heated under laboratory conditions 250 500 c degradation products of less altered kerogens are dominated by normal c 4 c 15 dicarboxylic acids with lesser amounts of n c 16 and n c 18 monocarboxylic acids and benzene mono to tetracarboxylic acids on the other hand thermally altered kerogens show benzene di to tetracarboxylic acids as dominant degradation products with lesser or no amounts variable depending on the degree of thermal alteration of dicarboxylic acids essentially no differences between the oxidative degradation products of naturally and artificially altered kerogens are observed as a result of this study five indices of aromatization total aromatic acids kerogen apparent aromaticity benzenetetracarboxylic acids total aromatic acids benzene 1 2 dicarboxylic acid benzenedicarboxylic acids benzene 1 2 3 tricarboxylic acid benzenetricarboxylic acids and two indices of aliphatic character total aliphatic acids kerogen aliphaticity are proposed to characterize the degree of thermal alteration of kerogens furthermore a good correlation is observed between apparent aromaticity estimated by the present kmno 4 oxidation method and that from the 13 c nmr method dennis et al 1982

hydrothermal petroleum in mineralized mounds at the seabed of guaymas basin petroleum has been dredged from an active hydrothermal mound area in the southern rift of guaymas basin gulf of california this organic matter is composed of gasoline range aliphatic and aromatic hydrocarbons and predominantly residual polar asphaltic material the aliphatic hydrocarbons of two bitumen samples have very different boiling range and composition both samples contain polynuclear aromatic hydrocarbons and olefins which indicate formation at pyrolytic temperatures the overall compositional data indicate an origin from biological detritus by thermal alteration and rapid quenching by hydrothermal removal followed by condensation at the seabed

hydrocarbon biomarkers from ordovician sediments and the fossil alga gloeocapsomorpha prisca zalessky 1917 numerous ordovician oils worldwide are known to show unusual and distinctive distributions of hydrocarbons which it has been suggested are derived from a unique benthonic mat forming non photosynthetic prokaryotic organism gloeocapsomorpha prisca zalessky 1917 which is the major contributor of organic matter organic matter rich sediments from the canning and amadeus basins of australia known to contain g prisca fossils and to have the characteristic predominance of odd carbon number c13 c19 n alkanes were investigated to determine other hydrocarbon distributions sediments from both basins contained abundant n alkylcyclohexanes with odd carbon number predominance c13 c19 and methyl n alkylcyclohexanes c14 c20 which in immature sediments showed an even carbon number predominance the isomer distribution of these latter compounds was determined by direct comparison with synthetic standards the sediments from both basins also contained very similar distributions of steranes and pentacyclic triterpanes and the derived kerogens had a characteristically light carbon isotope signature pyrolysis of a g prisca rich kerogen yielded a hydrocarbon mixture with a similar composition to the sediment extract except that there was a marked increase in the relative abundance of pristane phytane alkylcyclohexanes steranes and hopanes relative to n alkanes we argue on the basis of the geological geochemical and palynological data that g prisca was probably planktonic photosynthetic and very possibly eukaryotic and that the striking character of ordovician oils and sediments derive from bacterial and other diagenetic imprints superimposed on the primary signature of this organism

field data validation of an algorithm for computing obsidian effective hydration temperature this paper describes an analysis to validate the effective hydration temperature eht algorithm for obsidian rogers a k 2007 effective hydration temperature of obsidian a diffusion theory analysis of time dependent hydration rates j arch sci 34 656 665 using hourly temperature data from the amargosa desert research site near beatty nv these data were used as input to a numerical model of the temperature dependent diffusion process and eht was calculated yearly and for the aggregate the same temperature data were processed to extract input parameters for the climatic model reported and used as input for eht computation eht as computed from recorded hourly data was found to be within 1 c of that computed from the climatic model it is also shown that computed eht differences between sites are not sensitive to whether air or surface temperature data are used as long as they are used consistently however surface temperature data must be used if depth corrections are to be made

radiocarbon dating and the old wood problem the case of the hohokam chronology abstract many archaeological chronologies including that of the hohokam in southern arizona are based on a series of radiocarbon dates on wood this paper argues that because of variability in rates of wood decay processes in the environment and in systemic context such archaeological chronologies are potentially biased towards excessive antiquity by an old wood problem and must be reassessed following the theoretical insights of dean 1978 this paper sets forth principles and procedures for relating radiocarbon dates to cultural events emphasis is placed on identifying and taking into account the formation processes of 1 the dated specimens and 2 the deposits that yielded them this methodological framework is applied to hohokam radiocarbon dates and a chronology much shorter than the original gladwin haury formulation is supported

biogeochemistry of the 1640 ma mcarthur river hyc lead zinc ore and host sediments northern territory australia abstract the formation of the mcarthur river lead zinc deposit involves thermogenic or biologic oxidation of sedimentary organic matter the products of which generated a massive stratiform sulfide ore body and secondary carbonate and silica precipitates formed within the sediment pile down the flow pathway and above the reaction zone the fine grained texture of the mineralization indicates that primary ore texture is preserved and coupled with the regional thermal maturity indicate that this deposit is an ideal location to study organic matter signals related to ore formation and the sedimentary environment biomarker data point to a marine environment of deposition and are consistent with data previously collected from the host barney creek formation in the adjacent glyde subbasin an unusual biomarker distribution found in some samples from within two orebody is considered to be related to the presence of sulfide oxidizing bacteria these organisms flourished after turbidite deposition when oxygen in the upper part of the water column was mixed down to the sediment water interface the biomarker data are supported by micropalaeontologic observations from the same samples and are consistent with intermittent oxygenation of the water column to the sediment water interface this observation suggests an extension of the known occurrence of sulfide oxidizing bacteria back in time by 800 million years to 1640 ma

is obsidian hydration dating affected by relative humidity experiments carried out under temperatures and relative humidities that approximate ambient conditions show that the rate of hydration of obsidian is a function of the relative humidity as well as of previously established variables of temperature and obsidian chemical composition measurements of the relative humidity of soil at 25 sites and at depths of between 0 01 and 2 m below ground show that in most soil environments at depths below about 0 25 m the relative humidity is constant at 100 we have found that the thickness of the hydrated layer developed on obsidian outcrops exposed to the sun and to relative humidities of 30 90 is similar to that formed on other portions of the outcrop that were shielded from the sun and exposed to a relative humidity of approximately 100 surface samples of obsidian exposed to solar heating should hydrate more rapidly than samples buried in the ground however the effect of the lower mean relative humidity experiences by surface samples tends to compensate for the elevated temperature which may explain why obsidian hydration ages of surface samples usually approximate those derived from buried samples

possible origin of n alkanes with a remarkable even to odd predominance in recent marine sediments abstract n alkane distributions with a remarkable even to odd predominance c16 c24 were found in marine surface sediments the previously proposed diagenetic reduction of the corresponding n fatty acids could not be considered as a source for these n alkane based on a comparison of compositional features of n alkane n fatty acid and n alcohol distributions carbon isotope analyses and other geochemical parameters the data indicate that the even predominant n alkanes were derived directly from marine bacteria

formal subdivision of the holocene series epoch a discussion paper by a working group of intimate integration of ice core marine and terrestrial records and the subcommission on quaternary stratigraphy international commission on stratigraphy this discussion paper by a working group of intimate integration of ice core marine and terrestrial records and the subcommision on quaternary stratigraphy sqs of the international commission on stratigraphy ics considers the prospects for a formal subdivision of the holocene series epoch although previous attempts to subdivide the holocene have proved inconclusive recent developments in quaternary stratigraphy notably the definition of the pleistocene holocene boundary and the emergence of formal subdivisions of the pleistocene series epoch mean that it may be timely to revisit this matter the quaternary literature reveals a widespread but variable informal usage of a tripartite division of the holocene early middle or mid and late and we argue that this de facto subdivision should now be formalized to ensure consistency in stratigraphic terminology we propose an early middle holocene boundary at 8200 a bp and a middle late holocene boundary at 4200 a bp each of which is linked to a global stratotype section and point gssp should the proposal find a broad measure of support from the quaternary community a submission will be made to the international union of geological sciences iugs via the sqs and the ics for formal ratification of this subdivision of the holocene series epoch copyright 2012 john wiley sons ltd

early cretaceous bimodal magmatism related epithermal mineralization a case study of the gaosongshan gold deposit in the northern lesser xing an range ne china abstract low sulfidation ls gold mineralization is partially associated with bimodal volcanism in origin sources of ore mineralized fluids and relevant dynamic processes remain poorly understood to better understand these issues a study including deposit geology petrology zircon u pb dating and element and sr nd hf isotope geochemistry of bimodal volcanic rocks at gaosongshan was conducted the bimodal volcanic rocks are composed of andesitic rocks basalt andesite andesite trachyandesite andesitic pyroclastic of the meifeng formation and overlying rhyolite lava of the fuminhe formation cut by equivalent porphyry stocks which contain pyrite bearing granular textured quartz cavity with a sugary appearance with trapped single phase magmatic fluids the andesitic suite formed at approximately 106 108 ma prior to eruption of the younger rhyolitic magmas 105 6 1 7 ma n 13 mswd 1 2 the andesites show calc alkaline affinities which is a subduction related characteristic and show moderate la ybn 7 91 11 36 and weakly negative europium anomalies 0 80 1 02 indicating a source in the asthenospheric mantle with varying contamination by both subduction and continental materials a type rhyolitic rocks are geochemically comparable to the andesitic suite and their higher la ybn 13 01 30 05 and lower eu eu 0 66 0 73 indicate evolved products of andesitic magmas the estimated oxygen fugacity of dry 1 2 water rhyolite lava is fmq 1 87 whereas rhyolite porphyry is more oxidized fmq 0 12 and water rich 2 5 2 8 with probably being water saturated at 2 0 2 4 km depths therefore it is assumed that the essential constraints of bimodal magmatism on epithermal gold mineralization are sequential processes from ascending and gradual differentiation of crustal level mantle derived basaltic magmas to releases of hydrothermal solutions from the silica rich magma reservoir at shallower levels most importantly the oxygen fugacity of and the fluid fluxes from dry rhyolitic melts are critical restricting parameters for the limited reserves at gaosongshan thus this research contributes objective evidence for investigations of deposit genesis and prospecting targets

obsidian hydration dating of a pleistocene age site from the manus islands papua new guinea abstract obsidian hydration dating relies on the precise measurement of the depth of hydration developed over time in the surface of obsidians but the loss of surface by natural dissolution at some archaeological sites can result in erroneous age determinations by focussing the hydration measurement on internal crack surfaces protected from external surface erosion acceptable results have been achieved from a pleistocene age site in papua new guinea measurement of the hydration profile in thin sections of the sampled obsidian by computer imaging results in an improved reading error for the hydration depth by using the system on archaeological obsidians from the pamwak site the relative age results are more consistent with the radiocarbon age determinations than conventional obsidian hydration dating

the chemical structure of a pronounced series of iso alkanes in south oman crudes gas chromatograms of the saturated hydrocarbon fractions of the south oman crudes are characterised by a striking series of peaks called x peaks throughout this paper eluting between the n alkanes mainly in the c20 c26 range a gs ms study combined with optimised gc resolution shows that each peak is a superposition of subpeaks which correspond to a complex series of monomethylalkanes the x20 peak in the chromatogram for instance is found to be composed of virtually co eluting peaks corresponding to 5 6 7 8 9 and 10 methylnonadecane the larger x22 x23 and x24 peaks are superpositions of a similar set of monomethylalkanes and in addition a series of presumably dimethylalkanes of which the structures are only partly solved the large abundance of these iso alkanes is very specific for south oman crudes and may be caused by their pre cambrian origin or a specific source material

an archaeologically validated protocol for computing obsidian hydration rates from laboratory data this paper reports the computation of hydration rate for topaz mountain obsidian from laboratory data and a comparison with archaeological data from a well dated site camels back cave in western utah topaz mountain obsidian is found to be slow hydrating with a rate of 0 071 0 021 yr at an effective hydration temperature of 16 01 c this rate agrees with a rate developed from archaeological data from camels back cave within 6 activation energy of topaz mountain obsidian is 10370 544 k and its diffusion constant is 1 87 9 13 1013 2 yr both of which are independent of temperature its intra source variability in hydration rate is very low cv 0 01 implying a low variability in intrinsic water we present a model of chemical erosion which shows why earlier laboratory determined rates were incorrect and discuss the implications of our findings on the determination of experimentally derived rates in obsidian hydration dating

sterane and triterpane biomarkers in the precambrian nonesuch formation north american midcontinent rift abstract molecular fossils and organic matter from microbial communities living around 1 1 ga ago are well preserved in the nonesuch formation of the us midcontinent rift system although some compound classes of biological markers have been recognized repeatedly in previous studies of nonesuch rocks and associated petroleums steranes and triterpanes have not been detected failure to detect these compounds was due primarily to instrumental limitations and the relatively high thermal maturity of samples collected within zones of copper mineralization our analyses of nonesuch samples from the white pine mine and nonmineralized localities in michigan and wisconsin reveal suites of c 26 c 30 steranes and c 27 c 35 pentacyclic triterpanes similar to those found in phanerozoic oils and sedimentary rocks of marine origin stereoisomeric distributions in the nonesuch samples are consistent with moderate thermal maturity except in the mineralized zone near white pine

obsidian hydration dating on the south coast of peru we compare over 230 obsidian hydration readings from 30 individual site components from the southern nasca region snr with independent age estimates based on radiocarbon dates and temporally diagnostic artifacts although there are problems with small sample sizes and readings must be adjusted for elevation a very strong relationship accounting for nearly 90 of the total variation in the data set is found this suggests that obsidian hydration dating ohd works in the snr and is a viable means of independently estimating age residual values from our regression suggest that hydration age estimates are usually within 15 of the radiocarbon estimates finally we present an equation other scholars can use to estimate age for quispisisa obsidian in the snr

accuracy of obsidian hydration dating based on obsidian radiocarbon association and optical microscopy abstract most archaeologists using obsidian hydration dating ohd in the united states develop hydration rates from association of obsidian hydration rims with dates based on radiocarbon subsequently using the rate for chronometric analysis the overall accuracy of the process has never been quantified this paper reports an accuracy analysis in which sources of uncertainty are defined and modeled and their effects quantified a monte carlo simulation is used to quantify errors from rate development while uncertainties in age resulting from chronometric analysis are calculated analytically for typical ranges of error values hydration rate errors of 5 or less are achievable in the absence of systematic errors with errors of chronometric age estimates 20 30 or less

the significance of obsidian hydration dating in assessing the integrity of holocene midden hokkaido northern japan abstract since its novel invention in 1960 obsidian hydration dating is now recognized as the chronometric method to give dates of archaeological sites based on measurements of hydration rim thickness contrary to the increased awareness of various factors that affect hydration rates and reliability in measurements the question whether and the extent to which the validity in the rim thickness measurements corresponds to the interested event has been less discussed here validity of obsidian hydration dates that designate event of human site occupations is discussed in terms of site integrity of the early jomon midden in the holocene site of ocharasenai och hokkaido northern japan expected integrity of the midden evidently left by prehistoric hunter gatherers is tested through a comparison of microscopically measured average rim thicknesses between the primarily extracted specimens and those chosen after assessing the validity no statistical difference in estimated hydration dates between these two groups supports high integrity of the midden the estimated date for the early jomon occupation at the och is 4388 4942 bp fallen into the end of middle holocene results of the present examination indicate that obsidian hydration dating will aid to understand site formation processes