quaternary tectonic response to intensified glacial erosion in an orogenic wedge active orogens are thought to behave as internally deforming critical taper wedges that are in rough long term equilibrium with tectonic influx and erosional outflux spatial and temporal variations in climate are therefore hypothesized to have a significant influence on denudation topography and deformation of orogens thereby affecting wedge taper however the impact of the most severe transition in northern hemisphere climate during the cenozoic era the onset of glaciation has hitherto not been empirically documented here we analyse the spatial patterns of denudation and deformation and their temporal variations in the heavily glaciated st elias orogen in southern alaska low temperature thermochronometry thermokinematic modelling and offshore seismic reflection and borehole data suggest that the global scale intensification of glaciation in the middle pleistocene epoch enhanced glacier growth and caused ice streams to advance to the edge of the continental shelf this led to focused denudation across the subaerial reaches of the orogen and burial of the actively deforming wedge toe by the eroded sediment we propose that this climatically driven mass redistribution forced a structural reorganization of the orogen to maintain critical taper our empirical results thus support decades of numerical model predictions of orogenesis and provide compelling field evidence for the significant impact of climate change on tectonics intense glaciation during the middle pleistocene epoch led to focused denudation and mass redistribution within the st elias orogen in southern alaska and resulted in structural reorganization of the orogen the tectonic response of this orogen to climate change is consistent with predictions of numerical models

third millennium b c climate change in syria highlighted by carbon stable isotope analysis of 14c ams dated plant remains from ebla abstract we use ams accelerator mass spectrometry techniques for the simultaneous analysis of carbon stable isotopic values and 14c dating on charred plant remains found in the archaeological site in ebla syria and propose the diachronic variation in 13c plant values as a possible palaeoclimatic tool both anthracological and carpological remains usually employed in palaeoenvironmental palaeoagricultural palaeonutritional and palaeoeconomical reconstructions are used to study stable carbon isotopic variations in a chronological framework defined through radiocarbon ams measurements the results obtained from the samples of the ebla archaeological site show a chronological correspondence with other climatic reconstructions based on various proxy data available for the near east and shed new light on the aridity crisis of the iii millennium b c

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

sourcing geochemically identical obsidian multiscalar magnetic variations in the gutansar volcanic complex and implications for palaeolithic research in armenia abstract in obsidian rich armenia one of the most archaeologically significant obsidian resources is the gutansar volcanic complex gvc numerous palaeolithic sites across armenia consist of little more than deposits of obsidian tools and debris and within the hrazdan gorge the vast majority of artifacts is crafted from gvc obsidian for example about 93 of the lithic assemblages from the lower palaeolithic site of nor geghi 1 and the middle palaeolithic site of lusakert cave 1 are gvc obsidian although erupted from multiple volcanic centers gvc obsidians are geochemically identical and cover an area more than 70 km2 for studies seeking to reconstruct movements of palaeolithic hunter gatherers throughout the local landscape the expansive gvc is problematic geochemically identical obsidians dominate the foraging territories of sites within and near the complex here we explore the potential of obsidian magnetic properties to reveal hitherto unobservable patterns in gvc obsidian utilization with the ultimate goal of elucidating palaeolithic behavioral patterns our results show that magnetic properties vary over multiple scales within the gvc allowing obsidian sourcing to become multiscalar these measurements are rapid inexpensive and entirely nondestructive for small artifacts measuring a few basic magnetic properties enables us to distinguish geochemically identical obsidians from three eruptive centers and potentially to attribute artifacts to specific quarrying sites recognize changes in provisioning strategy and estimate a minimum number of cores represented by a lithic scatter

geochronologic studies in central new england ii post acadian hinged and differential uplift sup 40 ar sup 39 ar analyses of muscovite biotite and k feldspar from central new england reveal a remarkable pattern of mineral ages the ages are progressively younger from central to western new hampshire and rise sharply near the vermont border to ages more typical of post acadian cooling this distribution is attributed to differential uplift via isostatic rebound of an anomalously thickened crust at the bronson hill anticlinorium this explanation requires that between 6 and 8 km of normal fault motion has occurred on structures in western new hampshire not previously recognized to have accommodated this kind or magnitude of displacement this hinged differential uplift occurred from approximately 360 170 ma and is consistent with a time constant for rebound of approximately 80 m y

evidence of lateglacial and holocene climatic change and human impact in eastern anatolia high resolution pollen charcoal isotopic and geochemical records from the laminated sediments of lake van turkey annually laminated sediments from lake van spanning about 13000 varve years were sampled for stable isotopic geochemical pollen and charcoal analyses in order to find evidence of past regional climatic changes and human impact in the semi arid region of eastern anatolia turkey the lateglacial period was cold and dry with steppe vegetation and saline lake water during the younger dryas the lake level dropped dramatically and the vegetation turned to a semi desert geochemical and isotopic records indicate a strong increase in moisture at the onset of the holocene and artemisia chenopod steppes were partly replaced by grass steppe and pistachio scrub a delay of about 3000 years in the expansion of deciduous oak woodlands and high steppe fire frequencies suggest dry spring and summer weather during the early holocene at 8200 yr bp a shift in the regional climate regime facilitated the transport of more moisture into the interior areas of the taurus mountains and caused a change in the seasonal distribution of precipitation the steppe forests dominated by quercus advanced and reached their maximum extention at about 6200 yr bp all the proxy data indicate optimum climatic conditions low water salinity and high lake level between 6200 and 4000 yr bp after 4000 yr bp aridity increased again and the modern climatic situation was established human impact in the catchment of lake van started at 3800 yr bp and was intensified during the last 600 years

stratigraphy and ductile structure of the presidential range new hampshire tectonic implications for the acadian orogeny the presidential range of new hampshire with its unique high relief contains exceptionally well exposed rocks of the acadian orogenic hinterland these rocks are within the central maine terrane a belt of complexly metamorphosed and deformed silurian and devonian metasedimentary rocks the presidential range lies between regions to the south dominated by refolded nappes and synkinematic high grade regional metamorphism and regions to the northeast dominated by overlapping multiple deformation and contact metamorphism produced by late and post acadian plutons to better understand these complex tectonic variations and in particular to clearly and accurately determine the effects of the devonian acadian orogeny in a well exposed region the bedrock geology in the alpine zone of the presidential range was mapped in great detail the results of the stratigraphic and ductile structural analyses are presented here five metasedimentary formations have been recognized and constitute a conformable stratigraphy which from oldest to youngest are the silurian rangeley perry mountain smalls falls and madrid formations and the devonian littleton formation the littleton formation has been subdivided into fifteen different members and three submembers based on variations in bedding style of the schists and quartzites and other lithologic peculiarities the madrid smalls falls and perry mountains formations are extremely thin consistent with their deposition near the silurian tectonic hinge the rangeley formation is interpreted as an olistostromal melange and has been subdivided into three different members and six submembers on the basis of lithologic variations in the gneiss and subordinate units the presidential range preserves three phases of ductile folding f1 f2 and f3 and a single phase of thrust faulting t1 well constrained southeast east or northeast facing directions and consistent asymmetry of f1 nappe limbs suggest that nappe vergence was easterly severe refolding of some nappes resulted during f2 collapse of the nappe pile the west vergent greenough spring thrust fault truncated f1 and f2 structures and juxtaposed nonmigmatized and migmatized rocks f3 east vergent folding dominates the alpine zone and represents the final tightening of acadian structures which occurred after early granitic plutonism and prior to the emplacement of postkinematic granitic sheets the structural and sedimentological evidence supports the existence of a subduction system that was active beginning in the early silurian on the east flank of the bronson hill anticlinorium with a west dipping subducting slab geometry this system persisted throughout the acadian

effects of bedrock landslides on cosmogenically determined erosion rates abstract the successful quantification of long term erosion rates underpins our understanding of landscape formation the topographic evolution of mountain ranges and the mass balance within active orogens the measurement of in situ produced cosmogenic radionuclides crns in fluvial and alluvial sediments is perhaps the method with the greatest ability to provide such long term erosion rates although deep seated bedrock landsliding is an important erosional process in active orogens its effect on crn derived erosion rates is largely unquantified we present a numerical simulation of cosmogenic nuclide production and distribution in landslide dominated catchments to address the effect of bedrock landsliding on erosion rates results of the simulation indicate that the temporal stability of erosion rates determined from crn concentrations in sediment decreases with increased ratios of landsliding to bedrock weathering rates within a given catchment area and that as the frequency of landsliding increases larger catchment areas must be sampled in order to accurately evaluate long term erosion rates in addition results of this simulation suggest that sediment sampling for crns is the appropriate method for determining long term erosion rates in regions dominated by mass wasting processes whereas bedrock surface sampling for crns may generally underestimate long term erosion rates response times of crn concentrations to changes in erosion rate indicate that climatically driven cycles of erosion may be detected but that complete equilibration of crn concentrations to new erosional conditions may take tens of thousands of years comparison of simulated crn derived erosion rates with a new data set of such rates from the nepalese himalaya underscore the conclusions drawn from the model results

thermal history of the rio muni west africa ne brazil margins during continental breakup abstract we document the thermal record of breakup of the conjugate rio muni west africa and ne brazil margins using apatite fission track analysis vitrinite reflectance data and stratigraphic observations from both margins these results permit determination of the timing of four cooling episodes and the temperature of samples at the onset of each episode all samples are interpreted to have experienced higher temperatures in the geological past due to i elevated basal heatflow palaeogeothermal gradient in rio muni 1 well decaying from 58 c km during the mid cretaceous to 21 5 c km in the late cenozoic and ii progressive exhumation from formerly greater burial depth a well constrained history of changing palaeogeothermal gradient allows for much more precise quantification of the thickness of eroded section exhumation than if a constant heatflow is assumed cooling episodes identified from the palaeotemperature data at 110 95 ma both margins and 85 70 ma rio muni only coincide with major unconformities signifying respectively the cessation of rifting breakup and compressional shortening that affected the african continent following the establishment of post rift sedimentation drift the interval between these separate unconformities is occupied by allochthonous rafts of shallow water carbonates recording gravitational collapse of a marginal platform the rift shoulder uplift that triggered this collapse was enhanced by local transpression associated with the obliquely divergent ascension fracture zone and thermal doming due to the coeval st helena and ascension plumes the data also reveal a c 45 35 ma cooling episode attributed to deep sea erosion at the onset of eo oligocene ice growth and a c 15 10 ma episode interpreted as the record of miocene exhumation of the west african continental margin related to continent wide plume development integration of thermal history methods with traditional seismic and stratigraphy based observations yields a dynamic picture of kilometre scale fluctuations in base level through the breakup and early drift phases of development of these margins major unconformities at ocean margins are likely to represent composite surfaces recording not only eustasy but also regional plate margin generated deformation local intra basinal reorganization and the amplifying effect of negative feedbacks between these processes

environment and collapse eastern anatolian obsidians at urkesh tell mozan syria and the third millennium mesopotamian urban crisis the early to middle bronze age transition in northern mesopotamia has received great attention for the apparent concurrence of aridification deurbanisation and the end of the akkadian empire around 2200 bce our understanding of the crisis has been almost exclusively shaped by ceramics demography and subsistence exchange and the associated social networks have been largely neglected here we report our sourcing results for 97 obsidian artefacts from urkesh a large urban settlement inhabited throughout the crisis before the crisis six obsidian sources located in eastern anatolia are represented among the artefacts such a diversity of eastern anatolian obsidians at one site is hitherto unknown in mesopotamia it implies urkesh was a cosmopolitan city with diverse visitors or visitors with diverse itineraries during this crisis however obsidians came from only two of the closest sources two to three centuries passed before varied obsidians reappeared even when an obsidian source reappears the raw material seems to have come from a different collection spot we discuss the likely exchange mechanisms and related social networks responsible for the arrival of obsidians at urkesh and how they might have changed in response to climatic perturbations and regional government collapse

rates and timing of earth surface processes from in situ produced cosmogenic be 10 beryllium 10 is the longest lived of the seven known unstable isotopes of be it results mostly from the interaction of cosmic radiation primarily neutrons with a variety of target atoms by spallation the splitting of nuclei lal 1988 it can also be produced at very low levels by radio disintegration of u and th sharma and middleton 1989 although all radioactive be isotopes are produced in the atmosphere via cosmic ray reactions arnold 1956 lal and peters 1967 morris et al chapter 5 this volume in this paper we are most interested in 10be produced in rock which we refer to as in situ produced such in situ produced 10be is a cosmic ray dosimeter functioning as a quantitative monitor of near surface residence time in some geologic situations 10be can be used as a chronometer allowing one to estimate the duration of surface exposure in other settings 10be can be used as a tracer allowing one to estimate the rate distribution and behavior of earth surface processes rates of 10be production are very low in rocks exposed at earth s surface 102 atoms g 1 y 1 resulting in typical in situ produced 10be concentrations termed activities of 103 to 107 atoms g 1 the development of accelerator mass spectrometry ams in the 1980s allowed routine measurement of 10be at levels typical of rocks exposed near earth s surface elmore and phillips 1987 analytical refinements in the 1990s lowered detection limits by an order of magnitude allowing dating of exposure periods 103 years in favorable geologic and geographic situations simple exposure histories at high altitude and latitude most in situ 10be is measured in quartz mineral separates where the primary spallation target is o lal and arnold 1985

glacial and periglacial erosion of the appalachians abstract the marine 18 o record indicates that the first ice advance into the appalachians equivalent to that of the late wisconsin occurred in the pliocene at about 2 4 ma only periodic localized glacial and periglacial activity occurred in the northern appalachians from 2 33 to 0 85 ma after 0 85 ma middle to late pleistocene eight out of ten glaciations covered the northern appalachians and brought periglacial conditions to the southern appalachians during the last 850 000 years glaciation extended to the late wisconsin limit within the appalachians for 15 of the time and extended to the early wisconsin limit just north of the appalachians for 25 of the time pleistocene glacial erosion of the appalachians of 120 200 m is necessary to account for the estimated volume of pleistocene ocean sediment derived from the appalachians and the estimated volume of pliocene pleistocene glaciogenic ocean sediment derived from the entire laurentide ice sheet this amount of glacial erosion occurring over the maximum expectable duration of pliocene pleistocene ice cover of 247 000 years yields glacial erosion rates from 0 5 0 8 m ka 1 such depths of erosion by thick warm based ice streams were localized in the lowlands and estuaries of the northern appalachians in the maritimes the presence of thin cold based ice caused minimal erosion of uplands periglacial landforms and tundra boreal forest were distributed throughout the appalachian highlands and the northern coastal plain during the glacial maxima periglacial erosion of 0 15 0 30 m ka 1 near the ice in pennsylvania decline to 0 1 0 2 m ka 1 in the southern piedmont each cold period almost completely renewed the regolith by eroding slopes and filling valleys the cumulative effect of the eight to ten major cold events could have produced as much as a few ten s of meters of periglacial ridge top lowering during the pleistocene both estimated glacial and periglacial erosion rates greatly exceed estimated current fluvial erosion rates therefore glacial and periglacial processes should be considered the dominant processes in shaping the present appalachian landscape the northern appalachians may be evolving towards a form where the landscape provides just the shape necessary to permit the least work conveyance of the ice across the region during glacial maxima the southern appalachians may be evolving towards a form where the landscape provides just the hillslope form necessary to transport the debris provided by periglacial conditions

the role that plate tectonics inferred stress changes and stratigraphic unconformities have on the evolution of the west and central african rift system and the atlantic continental margins the muglad rift basin of sudan is a good example of polyphase rifting with at least three major phases of basin development each phase has resulted in the generation of source rock reservoir and seal geology with structural traps often closely linked to basement highs in this paper we investigate on a regional scale the tectonic processes that have contributed to rift basin development on a regional scale the evolution of the africa wide mesozoic rift system is intimately linked to relative movements of african sub plates and to global plate tectonic processes and plate interactions changes in plate interactions are observed in the oceanic crust as azimuth changes of fracture zone geometries and by inference have caused significant modifications to both the orientation and magnitude of the motions of the african sub plates such plate motion processes have controlled the polyphase development of the west and central african rift system on the basinal scale changes of sub plate motions have resulted in changes in the stress field which have had a clear impact on the deformation and fault geometries of rift basins and on the resulting stratigraphy the construction of the first unified stratigraphic chart for the west and central african rift system shows a close correlation in the timing of the major unconformities with the timing of changes in relative plate motion as observed in the changes of the azimuthal geometry of the oceanic fracture zones in the central atlantic since similarly timed unconformities exist along the continental margins of africa and south america we propose that the causative mechanism is change in relative plate motion which leads to an increase or decrease in the tension on the plate and thus controls the strength or effective elastic thickness te of the crust plate beneath the margins this results in a focused change in isostatic response of the margin during short period changes in relative plate motion i e more tension will mean that loads are not compensated locally resulting in local uplift of the margin

distinguishing nemrut dag and bingol a obsidians geochemical and landscape differences and the archaeological implications abstract distinguishing the geochemically similar bingol a and nemrut dag peralkaline obsidians is a major challenge in near eastern obsidian sourcing despite abundant claims in the literature otherwise this study reveals that bingol a and nemrut dag obsidians are distinguishable with adequate source sampling and highly accurate and repeatable data for geochemically important elements earlier research has endeavored to link a simple geochemical trend peralkalinity to specific locations at nemrut dag but existing schemes to distinguish bingol a and nemrut dag obsidians cannot validly link compositional clusters to the landscape this study demonstrates that additional elements are required to attribute artifacts to specific obsidian bearing lava flows at the volcano limitations of this newly analyzed collection of geo referenced nemrut dag and bingol specimens suggests caution is still warranted in sourcing peralkaline obsidians but a few archaeological implications are clear new sourcing results from tell mozan in northeastern syria refute a widespread assumption that one can use maximal efficiency to deduce whether peralkaline obsidian artifacts originated from nemrut dag or bingol a the ability to discern among these sources also enables inquiries into issues of cultural and technological preferences regarding these obsidians

exhumation along the fairweather fault southeastern alaska based on low temperature thermochronometry 1 the southern alaskan syntaxis marks the spectacular junction between the 1000 km long pacific north america transform margin and the chugach st elias belt where subduction and terrane accretion drive rapid convergent deformation and rock uplift new low temperature thermochronometry reveals that intense orogenic deformation is not restricted to one side of the syntaxis but extends nearly 300 km south along the dextral fairweather fault apatite and zircon u th he ages as young as 0 9 and 2 0 ma suggest maximum exhumation rates of nearly 2 mm a in close proximity 0 5 mm a along the entire plate margin we estimate that long term rock uplift accommodates 3 mm a of fault normal convergence in this area this suggests that the fairweather fault is slightly transpressive and highly partitioned analogous to the central san andreas fault this convergence only accounts for 1 5 of the obliquity between pacific plate motion and the continental margin however implying the deficit is taken up by 1 2 cm a thrust sinistral motion along the offshore transition fault additionally thermochronometry shows a marked increase in bedrock cooling coincident with onset of heavy glaciation similar to what has been observed in other parts of the pacific northwest the tectonically active fairweather corridor is distinguished however by the magnitude of the acceleration and the depth of exhumation since pliocene climate change

from flow to quarry magnetic properties of obsidian and changing the scale of archaeological sourcing abstract previous studies have endeavored to use petrophysical traits of obsidian particularly its magnetic properties as an alternative to conventional geochemical sourcing one of the greatest successes in archaeological science magnetic approaches however have not seen widespread application due to their mixed successes in a time when geochemical analyses can be conducted non destructively in the field and in a minute or two magnetic measurements of obsidian must offer novel archaeological insights to be worthwhile not merely act as a less successful version of geochemistry to this end we report the findings of our large scale study of obsidian magnetism which includes 734 geological obsidian specimens and 97 artifacts measured for six simple magnetic parameters based on our results we propose rather than using magnetic properties to source artifacts to a particular obsidian flow inter flow sourcing these properties are best used to differentiate quarrying sites within an individual flow intra flow sourcing our results also demonstrate that certain magnetic properties are highly affected by ancient knappers material selection criteria furthermore depending on the spatial scales of variation which likely vary from flow to flow we envision several potential applications of this approach including integration into minimum analytical nodule analysis mana magnetic data appear to shift the scale of obsidian sourcing from flows to quarries and in turn enable new insights into raw material procurement strategies group mobility lithic technology and the organization of space and production

macusani obsidian from southern peru a characterization of its elemental composition with a demonstration of its ancient use transparent obsidian artifacts have been reported for the northern lake titicaca basin based on instrumental neutron activation analysis inaa of these artifacts a distinct chemical group was identified yet the location of the source of transparent obsidian in the southern andes remained unreported in the archaeological literature this paper reports on the chemical composition and geographic location of a source of transparent obsidian from the macusani region of peru through the use of inaa and portable x ray fluorescence pxrf we demonstrate that macusani obsidian or macusanite comprises at least two chemical groups one of these groups was used for making artifacts during the archaic period artifacts made of this obsidian were found more than 120 km from the source and yet one third of the obsidian artifacts encountered at macusani were from the non local source of chivay which is 215 km to the southwest

tongan and samoan volcanic glass pxrf analysis and implications for constructs of ancestral polynesian society a provenance study of volcanic glass specimens from 12 archaeological sites in the kingdom of tonga is carried out employing pxrf portable x ray fluorescence analysis to accomplish this volcanic glass samples from previously identified sources in northern tonga and the adjacent islands of samoa are analyzed results indicate inter island voyaging and interaction over a 600 km linear distance along the tongan island chain from first lapita settlement ca 2900 bp throughout later prehistory tongan volcanic glass however is not found in samoa and with the exception of one late prehistoric specimen samoan volcanic glass is not present in tonga this distribution challenges current concepts of an integrated ancestral society and homeland common to tonga and samoa from the lapita period onward

turkish occurrences of obsidian and use by prehistoric peoples in the near east from 14 000 to 6000 bp obsidian was widely used as a raw material for making tools and luxury objects by prehistoric peoples of the near and middle east to identify the origin of archaeological obsidians and the volcanic complexes which produced the blocks from which they were knapped the different methods of mineralogy chemistry or dating are used in this paper we develop the geochemical identification of turkish obsidian sources from the volcano to the artefacts introducing the use of spidergrams and argon geochronology as useful tools this leads to a reevaluation of the possible obsidian sources to the identification of new sources and to wider archaeological conclusions analyses carried out on a selection of samples of turkish geological obsidians and obsidian artefacts from near east sites demonstrate that this obsidian came essentially from central and south eastern anatolia however although there are numerous sources in these regions at the present time only some of the deposits are known to have been exploited in cappadocia gollu dagi eastern flank and nenezi dagi in eastern anatolia the deposits of bingol and nemrut dagi as well as a source on the northern shore of lake van meydan dagi ziyaret dagi the obsidian from cappadocia was widely used in central anatolia its use spread westward to the sea of marmara and eastward to the middle euphrates then along the mediterranean coast to the negev the obsidian of lake van was diffused through the basins of the tigris and euphrates to the shores of the persian gulf even reaching arabia to the west it penetrated the valleys of the orontes and jordan rivers as far as the dead sea

vegetation development in the middle euphrates and upper jazirah syria turkey during the bronze age vegetation changes are reconstructed based on more than 51 000 charcoal fragments of more than 380 samples from nine bronze age sites in northern syria and southern turkey in addition to fragment proportions special attention was paid to the frequency of pistacia relative to quercus and populus salix relative to tamarix fruit tree ubiquity and riverine diversity in order to gain an improved understanding of the human versus climatic impact on the vegetation the results indicate that human impacts first took place within the riverine forest this phase was followed by land clearing within the woodland steppe especially in the northern portion of the study area in the south near emar the woodland steppe probably disappeared by the late bronze age it is uncertain whether this was caused by aridification and or human clearing the northward shift of the pistacia woodland steppe is very likely a result of climatic drying that occurred throughout the entire period under investigation although increased deforestation is evident through time the small proportions of imported wood indicate that local resources were still available

refining the archaeomagnetic dating curve for the near east new intensity data from bronze age ceramics at tell mozan syria abstract uncertainty in radiocarbon dates for the near east caused by a bimodal distribution of ages due to the natural fluctuations of 14 c in the atmosphere has demonstrated the need for an alternative absolute dating technique to aid in the construction of site chronologies here we present a new archaeointensity reference curve model for the first three millennia bce for the levant syria israel jordan for use in archaeomagnetic dating and contribute twelve new intensity results to an increasingly dense geomagnetic field record for the period between 2400 and 1200 bce in the near east archaeomagnetic analysis was conducted on ceramic samples i e pottery sherds from seven sequential and well constrained occupational layers at the site of tell mozan bronze age urkesh in northeastern syria resulting in a 90 success rate by specimen n 42 for archaeointensity determination and an 86 correspondence between the model and the archaeologically derived dates within one standard deviation 1 age standard deviations as low as 24 years were obtained after integration with stratigraphic constraints we also outline the techniques and sampling procedures of archaeomagnetic dating in a manner suitable for the non paleomagnetist while detailing methodology for archaeomagnetic researchers

presence of a long term lithospheric thermal anomaly evidence from apatite fission track analysis in northern new england abstract apatite fission track aft ages from 56 samples of paleozoic and mesozoic crystalline rocks in new hampshire northeastern vermont and western maine range from 70 to 140 ma and reflect widespread early to late cretaceous cooling the regional aft age distributions determined in this study suggest that reactivation of preexisting orogen parallel faults and the presence of a long lived thermal anomaly in the lithospheric mantle controlled the late unroofing history of this part of the northern appalachians a northeast trending zone of young dominantly late cretaceous aft ages 70 118 ma extends from southwestern new hampshire through the central white mountain region and continues into northern new hampshire northeastern vermont and western maine providing evidence for regional nw se extension and cooling at this time significantly older aft ages 125 140 ma in the region bounded by the bill little ammonoosuc and northey hill faults in northwestern new hampshire suggest a normal sense r

post 10 ma uplift and exhumation of the northern coast mountains british columbia apatite u th he ages reveal three distinct periods in the exhumation history of the northern coast mountains 54 n a well developed helium partial retention zone indicates little or no exhumation between ca 30 and 10 ma beginning at 10 ma and extending to at least 4 ma the range underwent steady but slow exhumation of 0 22 mm yr after which the exhumation rate increased by at least 70 an 85 km long he age traverse across the orogen at sea level shows that vertical offsets on post 10 ma faults are minor furthermore the sea level he ages 14 2 8 ma inversely correlate with local mean elevation along the traverse these data suggest that the coast mountains first appeared as a significant topographic feature only within the past few million years this history is not consistent with suggestions that uplift of the range resulted from formation of the queen charlotte basin in early middle miocene time we speculate that intense erosion by alpine and continental glaciation after 2 5 ma triggered isostatic uplift and creation of the modern topography of the coast mountains

moving sources a preliminary study of volcanic glass artifact distributions in northeast china using pxrf recent studies have highlighted the long distance transport of obsidian from the paektusan tianchi or baitoushan in chinese volcano on the border between china and north korea to eastern russia and korea but little is known about the role of the local population in the production and movement or exchange of this important raw material this paper addresses this data lacuna by presenting sourcing results of 440 artifacts from 18 late paleolithic sites located in northeast china a portable xrf enabled rapid non destructive characterization of samples the results show that although paektusan obsidian was widely transported throughout northeast asia material from at least three other sources was also used in particular we highlight the significance of basaltic glass artifacts with the same geochemistry as sources found in the primorye region of far east russia in sites from northeast china this result indicates a two way movement of volcanic glass artifacts between primorye and the northeast of china rather than a unidirectional long distance exchange system originating from paektusan volcano

tectonics of the acadian orogeny in new england and adjacent canada paleogeographic analysis of post taconian rocks in new england and adjacent parts of canada has revealed the existence of two volcanic arcs which shut off at the time of the acadian orogeny one was built on arc basement previously accreted to north america during the taconic orogeny the other on precambrian continental basement of avalonia in the intervening merrimack fredericton trough metamorphosed and poly deformed turbidites and black shales record deep water conditions in silurian following mckerrow and ziegler 1971 this tract is interpreted as the site of an ocean which closed in siluro devonian by simultaneous subduction beneath both continental margins in the molucca sea in indonesia a comparable arc arc collision is in an early stage of development moore et al 1982 suggested that an accretionary prism built against one arc is overthrusting its counterpart which developed on the other side of the ocean an identical geometry with an avalonian accretionary prism overriding the conve

using meteoric 10be to track fluvial sand through the waipaoa river basin new zealand we use meteoric 10 be measured in 24 fluvial sand samples collected along the mainstem and from prominent tributaries within the tectonically active waipaoa river basin new zealand to identify sediment sources and monitor the mixing of sediment as it travels from headwater basins to the sea deforestation for agriculture beginning in the early 1900s resulted in severe but nonuniformly distributed erosion tributaries in the northern headwaters where large amphitheater gullies that continually feed prodigious amounts of deeply sourced sediment to the mainstem are prevalent yield exceptionally low concentrations of meteoric 10 be 1 5 10 6 atoms g 1 in the more stable eastern and western tributaries concentrations of meteoric 10 be are nearly an order of magnitude greater 14 10 6 atoms g 1 meteoric 10 be concentrations in samples collected along the mainstem above and below tributary confluences steadily and regularly increase downstream r 2 0 92 as large amounts of low concentration gully derived sediments are augmented with higher concentration sediment from more stable tributaries providing strong evidence that meteoric 10 be concentrations reflect sediment sourcing in this fluvial network a two component mixing model indicates that the gullied northern region of the waipaoa basin produces sediment at a rate 20 times that of the eastern and western regions these results suggest that meteoric 10 be in contrast to the widely applied in situ technique that is limited by the availability and distribution of quartz is an effective tool for the rapid assessment of sediment dynamics and movement within a wide range of fluvial networks

diversity in obsidian use in the prehistoric and early historic middle east abstract the presence of obsidian in the near east has always evoked a response about its exotic nature and origins it was not until 1960s however that this was put onto a scientific footing when colin renfrew and his collaborators began to explore obsidian in turkey and the mediterranean their characterisation of the sources allowed them to attribute artefacts to different sources and suggest models of dispersal and distribution since then considerably more artefacts have been attributed to sources although mostly only small numbers from individual sites this has led to various interpretations of how obsidian was obtained and used new studies have considered least cost path analysis network analysis and agent based modelling increasingly new methods of provenancing of artefacts have also meant that large number of artefacts can be analysed relatively speedily and efficiently portable instruments allow data to be collected outside laboratories avoiding restrictions imposed by export licenses or simplifying work on museum collections here we employ richness and diversity indexes to elucidate some of the patterns in obsidian source use and argue that there are several reasons why the provenancing of large proportions of assemblages will be critical in exploiting the true potential of obsidian studies in the near east even though the initial haphazard small sample approach has been quite effective in sketching out the big picture

glaciation as a destructive and constructive control on mountain building glacial erosion is thought to have an important role in controlling mountain height a common perception is that glaciers are powerful erosive agents inhibiting the ability of active mountains to rise significantly above the elevation of permanent glaciation through a process known as the glacial buzzsaw but now a study of erosion patterns and climate data from the late cenozoic in the glaciated patagonian andes suggests that glaciation can also have the reverse effect in effect making mountains higher at these polar latitudes glaciation acts as a protective layer preserving the uplifting mountains from erosion and allowing them to reach heights well above those predicted had a glacial buzzsaw been active it has been suggested that glacial erosion has an important role in controlling mountain height here spatial and temporal patterns of erosion in the glaciated patagonian andes have been assessed with the help of a low temperature thermochronologic data set the results show that between 38 s and 49 s accelerated erosion at the onset of widespread glaciation limits mountain height but at higher latitudes glaciation protects the landscape from erosion and leads to growth in mountain height and width theoretical analysis predicts that enhanced erosion related to late cenozoic global cooling can act as a first order influence on the internal dynamics of mountain building leading to a reduction in orogen width and height1 2 3 the strongest response is predicted in orogens dominated by highly efficient alpine glacial erosion producing a characteristic pattern of enhanced erosion on the windward flank of the orogen and maximum elevation controlled by glacier equilibrium line altitude3 4 where long term glacier mass gain equals mass loss however acquiring definitive field evidence of an active tectonic response to global climate cooling has been elusive5 here we present an extensive new low temperature thermochronologic data set from the patagonian andes a high latitude active orogen with a well documented late cenozoic tectonic climatic and glacial history data from 38 s to 49 s record a marked acceleration in erosion 7 to 5 myr ago coeval with the onset of major patagonian glaciation6 and retreat of deformation from the easternmost thrust front7 the highest rates and magnitudes of erosion are restricted to the glacial equilibrium line altitude on the windward western flank of the orogen as predicted in models of glaciated critical taper orogens where erosion rate is a function of ice sliding velocity3 8 in contrast towards higher latitudes 49 s to 56 s a transition to older bedrock cooling ages signifies much reduced late cenozoic erosion despite dominantly glacial conditions here since the latest miocene6 the increased height of the orogenic divide at these latitudes well above the equilibrium line altitude leads us to conclude that the southernmost patagonian andes represent the first recognized example of regional glacial protection of an active orogen from erosion leading to constructive growth in orogen height and width

networks and neolithisation sourcing obsidian from kortik tepe se anatolia abstract this paper details the use of obsidian sourcing to reconstruct networks of interaction or communities of practice amongst populations of south eastern anatolia and the near east in the context of neolithisation during the late 11th early 10th millennia bc edxrf was used to elementally characterise 120 artefacts of epi palaeolithic pre pottery neolithic a date from kortik tepe in south eastern anatolia four eastern anatolian sources are represented mainly bingol a b and nemrut dag plus the first evidence for the use of mus obsidian when the source data is integrated with the artefacts techno typological attributes it is possible to locate the assemblage within an upper tigris tradition with some interesting local differences which stands in stark contrast to contemporary practices in northern mesopotamia and the levant these local and regional distinctions support recent views of the neolithic being much more heterogeneous with a mosaic of community specific local traditions of subsistence practices raw material choices and lithic technologies during the younger dryas early holocene

felsenmeer persistence under non erosive ice in the torngat and kaumajet mountains quebec and labrador as determined by soil weathering and cosmogenic nuclide exposure dating soil analyses and terrestrial cosmogenic nuclide exposure dating are combined and a conceptual model proposed to explain altitudinal weathering contrasts in high latitude highlands we show that summits in the torngat and kaumajet mountains were covered by ice during the last glacial maximum and that their felsenmeer cover probably survived multiple glaciation events for similar lithologies soils on felsenmeer covered summits are signigicantly more weathered than those below the felsenmeer limit displaying higher concentrations of crystalline iron amorphous aluminium and silicium extracted with oxalate secondary minerals such as gibbsite and kaolinite occur in felsenmeer soils whereas those formed in till lacked these secondary minerals 10be and 26al exposure ages for nine of ten samples from high elevation tors and autochthonous felsenmeer blocks range from 73 6 to 157 15 ka by contrast ages of 11 4 1 0 and 11 7 1 0 ka are measured for bedrock in the much lower saglek zone indicating extensive 3 m glacial erosion of this zone during late wisconsinan glaciation 26al 10be ratios demonstrate that exposure of the high elevation surfaces was interrupted during at least one cosmic ray shielding event by either ice or till cover in either case late wisconsinan glaciers could not have extensively eroded these surfaces five erratics dated above the saglek zone including one in the felsenmeer zone have exposure ages ranging from 11 6 1 0 to 13 6 0 7 ka this indicates that valley and high elevation ice persisted through the younger dryas chron and provides further evidence that the highlands were not nunataks during the late wisconsinan period

mesozoic hotspot epeirogeny in eastern north america geologic data especially conodont paleotemperatures imply that southeastern canada and new england have been elevated at least 4 km relative to the central appalachian region apatite fission track ages suggest that the uplift and consequent erosion occurred in cretaceous early tertiary time consistent with the formation of a broad swell as north america moved northwestward over the great meteor hotspot

hotspot tracks and the early rifting of the atlantic abstract many hotspot tracks appear to become the locus of later rifting as though the heat of the hotspot weakens the lithosphere and tens of millions of years later the continents are split along these weakened lines examples are the west coast of greenland east coast of labrador madeira hotspot the south coast of mexico north coast of honduras guyana hotspot and the south coast of west africa north coast of brazil st helena hotspot a modern day analog of a possible future rift is the snake river plain where the north american continent is being pre weakened by the yellowstone hotspot track this conclusion is based on reconstructions of the motions of the continents over hotspots for the past 200 million years the relative motions of the plates are determined from magnetic anomaly isochrons in the oceans and the motion of one plate is chosen ad hoc to best fit the motions of the plates over the hotspots however once the motion of this one plate is chosen the motions of all the other plates are prescribed by the relative motion constraints in addition to the correlation between the predicted tracks and sites of later continental breakup exposed continental shields correlate with the tracks their exposure may be the result of hotspot induced uplift which has led to erosion of their former platform sediment cover

a cost surface model of volcanic glass quarrying and exchange in hawai i abstract the spatial distribution of artifacts from the pu u wa awa a volcanic glass source north kona district hawai i island shows a pattern of direct access by those living in the immediately vicinity of the source with subsequent down the line exchange most quarrying and exchanges likely occurred within a single day s travel from sites where artifacts were deposited the exception to this is the discovery of non local direct access evident in assemblages from the extreme southern end of hawai i island these visits may have involved voyages by canoe while people did not often travel far for volcanic glass they nonetheless appear to have had unfettered accessed to source material and freely conducted inter community exchanges this implies volcanic glass was treated as a common pooled resource and the existence of informal exchange relationships

cosmogenic nuclide ages for new england coastal moraines martha s vineyard and cape cod massachusetts usa abstract cosmogenic nuclide exposure ages for 13 glacially transported boulders atop the martha s vineyard moraine ma usa indicate that the southeastern margin of the laurentide ice sheet reached its maximum extent during the last glaciation 23 200 500 yr ago another 10 age determinations from the younger buzzards bay moraine near woods hole ma indicate that this moraine complex was formed 18 800 400 yr ago these ages correlate approximately with the terminations of cooling cycles recorded in greenland ice cores and coeval ice rafting events suggesting that the marginal position of this sector of the ice sheet was tightly coupled to north atlantic climate during the last glacial maximum

slow late paleozoic exhumation in the presidential range of new hampshire as determined by the 40ar 39ar relief method 40 ar 39 ar mineral ages from muscovite were used to determine exhumation rates in the multiply deformed and metamorphosed silurian and devonian metasedimentary rocks exposed on mount washington new hampshire the muscovite ages increase progressively from the bottom to the top of the mountain the oldest mount washington summit elevation 6200 ft 1900 m is 304 3 ma and the youngest route 16 elevation 1350 ft 410 ml is 274 3 ma the age and elevation data yield an exhumation rate of 0 04 mm yr the exhumation rate indicates that 1 the middle pennsylvanian through early permian was a period of very slow exhumation 2 rapid uplift associated with the acadian orogeny must have terminated by at least 305 ma 3 sometime after 274 ma renewed uplift created the present topography of the mount washington massif and 4 the relief method can be used successfully in older more deeply eroded orogenic belts if the topographic relief is adequate and cooling was slow

characterization of new zealand obsidian using pxrf abstract new zealand has some of the most active areas of rhyolitic volcanism in the world and this has produced numerous obsidian sources in the northern half of the north island in total archaeologists have recognized 27 named locations from which obsidian can be obtained scattered across 4 geological source regions shortly after colonization in the late 13th century ad polynesian settlers began transporting this material some thousands of kilometers throughout the country and across the sea in small quantities to distant neighbors in the kermadecs and chatham islands although considerable research has been conducted on obsidian sourcing in new zealand the complexity of geochemical source discrimination and the lack of a practical method of non destructive geochemical analysis has hindered progress we present the results of our use of pxrf to provide geochemical data on new zealand obsidian sources and to compare the use of discriminant analysis and classification tree analysis to discriminate among sources and attribute archaeological samples to sources our research suggests that classification tree analysis is superior to discriminant analysis in sourcing studies a large case study using an important settlement phase site s11 20 from the auckland region demonstrates the utility of the methods and the results support a model of high degrees of mobility and interaction during the early settlement of new zealand

modeling of the temperature sensitivity of the apatite u th he thermochronometer apatite u th he apparent ages will generally reflect residence for extended periods at temperatures where helium is neither quantitatively retained nor lost by diffusion to characterize the response of apatite he ages to thermal histories involving partial he retention we explored solutions to the he production diffusion equation under thermally static conditions the analytical solution to this equation coupled with published diffusivity data demonstrates that the zone of partial he retention extends from about 40 c to 85 c this zone lies at temperatures 35 c cooler than the analogous fission track partial annealing zone he ages within the partial retention zone ultimately achieve a balance between he production and loss yielding a steady state age both the ultimate age and the time it takes to achieve this age are temperature dependent for example an apatite held at 75 c equilibrates to an age of 2 ma after 17 myr regardless of whether equilibrium is approached from a higher or a lower initial he age for representative dynamic thermal histories we evaluated apatite he ages using a numerical solution to the ingrowth diffusion equation the results illustrate the sensitivity of he ages to various geologic histories and are useful for understanding he age elevation relationships and for testing time temperature paths derived from apatite fission track length distributions in addition although he diffuses rapidly from apatite at shallow crustal temperatures modeling of ambient temperature fluctuations indicates that he ages are nearly unaffected by surficial processes

tracing the impact of glacial interglacial climate variability on erosion of the southern andes sediment accumulation rates of well dated primarily terrigenous marine sediments collected along the chilean continental margin were used to infer erosion rates of the southern andes and the adjacent coastal cordillera compared to the holocene sediment supply to the margin and thus erosion were substantially enhanced during the last glacial when continental rainfall in the region was higher major changes in precipitation forcing to the southern andes on such glacial interglacial time scales appear to be transferred to offshore sedimentation rates by a fixed relation these data show that marine archives can make it possible to trace variability in erosion at adjacent continents on time scales to 10 3 yr a much better resolution than provided by commonly used methods such as thermochronometry or seismic studies

fluvial environmental contexts for archaeological sites in the upper khabur basin northeastern syria today the eastern tributaries of the upper khabur run dry during the summer and the landscape is devoid of trees this picture is misleading when we try to understand archaeological sites within their former environmental context interdisciplinary geomorphological archaeobotanical and ostracod research on a sequence from the wadi jaghjagh indicates that relatively stable perennial flow velocities occurred during the mid 4th to mid 3rd millennium bc evidence was found for a gallery forest and swamp belt along the jaghjagh during the mid 4th millennium bc oak park woodland was present within the region in the 3rd millennium bc and probably up to at least the 3rd century ad shortly after 2500 bc jaghjagh stream velocities probably decreased or the stream bed had changed its location later deposits possibly dating to the 5th century bc indicate similar rather stable flow of the jaghjagh more recently however about ca ad 900 or afterwards a flashflood like regime occurred which may relate to deforestation the wadi khanzir sediment archives reflect the flashy intermittent regime of this stream like it still is today with flashflood evidence dating to the first half of the holocene and probably dating to approximately ad 400 or later along the jarrah topsoil was eroded and redeposited by the wadi sometime between 1300 and 600 bc this may have been caused by the intensive resettlement program of this region around 800 bc between about 600 and 300 bc 1 5 m of clay was deposited on the plain

non destructive pxrf analysis of museum curated obsidian from the near east abstract non destructive pxrf has the potential to expand sample populations of archaeological provenancing studies by facilitating access to museum collections of artefacts in this study we use museum curated obsidian for the sites of tell brak mersin yumuktepe and tell arpachiyah and geological obsidian samples from central turkey to demonstrate that non destructive pxrf is comparable to other techniques in differentiating between near eastern obsidian sources secondly we use multivariate analysis to evaluate whether non destructive pxrf is sufficiently accurate and precise to enable comparison with legacy datasets from previous analysis using pixe and icp ms multivariate analyses show that instrumental offsets between the results from pxrf and other analytic techniques are less than source to source variation typical for most anatolian obsidian outcrops and pxrf identified geochemical groups are directly comparable to legacy datasets non destructive pxrf analysis indicates that during the chalcolithic east gollu dag and nenezi dag continued to be the major sources of obsidian to communities in central anatolia and the bingol range and mountains surrounding lake van supplied sites east of the levant variations in the analysed assemblages suggest a number of obsidian exchange networks existed during this period

glacial deposits at wylfa head anglesey north wales evidence for late devensian deposition in a non marine environment the nature and origin of glacial sediments at wylfa head are described and their significance with regard to sedimentary environments during late devensian deglaciation of the irish sea basin is discussed recent models of deglaciation under glaciomarine conditions are challenged the quaternary sequence at wylfa consists of eroded and glaciotectonically deformed bedrock locally derived lodgement till calcareous silt rich lodgement till containing northern erratics discontinuous units of orange brown silty sand of possible aeolian origin and grey laminated freshwater silts filling a small kettle hole the till units thicken to the south where the surface is drumlinised it is concluded that the landforms and deposits result from a warm based irish sea glacier which moved towards the southwest spatial variation in basal water pressure resulted from localised drainage through zones of more heavily jointed bedrock rapid glacial erosion occurred in areas where subglacial water pressure was relatively high while deposition of the resulting basal sediment took place where water pressures were reduced the glacier also carried basal calcareous silty till onshore which was deposited by lodgement processes none of the deposits at wylfa are interpreted as glaciomarine in origin and there is no evidence at this site for an isostatically induced marine transgression prior to deglaciation

testing the accuracy of portable x ray fluorescence to study aztec and colonial obsidian supply at xaltocan mexico abstract this article demonstrates the accuracy of non destructive portable x ray fluorescence p xrf for the study of obsidian in central mexico obsidian sources were identified for a sample of 103 artifacts from the site of xaltocan which spanned the rise and fall of the aztec empire and the first centuries of spanish colonial rule ad 900 1700 sources were assigned by comparing p xrf measurements with previously published source data and were verified using the standard techniques of laboratory xrf l xrf and instrumental neutron activation analysis inaa additional tests of potentially confounding factors show that neither length of read time presence of surface residue nor incomplete detector coverage due to small artifact size compromised our ability to attribute sources to artifacts concave surfaces did decrease the accuracy of readings because of the greater distance between the artifact and the detector our results provide new insight into the stability of supply networks and markets well into the colonial period as well as the homogenizing tendencies of the aztec market system

using in situ cosmogenic 10be to identify the source of sediment leaving greenland we use the concentration of in situ 10be in quartz isolated from fluvial and morainal sand to trace sediment sources and to determine the relative contribution of glacerized and deglaciated terrain to greenland s sediment budget we sampled along the western eastern and southern margins of the greenland ice sheet and collected sediment sourced from glacerized n 19 and non glacerized terrain n 10 from channels where sediment from glacerized and non glacerized terrain is mixed n 28 from holocene glacial fluvial terraces n 4 and from one sand dune in situ 10be concentrations in sediment range from 1600 to 34 000 atoms g 1 the concentration of in situ 10be in sediment sourced from non glacerized terrain is significantly higher than in sediment sourced from glacerized areas in mixed channel sediment and in terrace sediment that was deposited during the holocene to constrain the timing of landscape exposure for the deglaciated portion of the narsarsuaq field area in southern greenland we measured in situ 10be concentration in bedrock n 5 and boulder n 6 samples paired bedrock and boulder ages are indistinguishable at 1 uncertainty and indicate rapid exposure of the upland slopes at 10 5 ka the isotope concentration in sediment sourced from non glacerized terrain is higher than in sediment sourced from glacerized terrain because the non glacerized landscape has been exposed to cosmic radiation since early holocene deglaciation sediment from glacerized areas contains a low but measurable concentration of 10be that probably accumulated at depth during a prolonged period of exposure probably before the establishment of the greenland ice sheet the concentration of 10be in mixed fluvial sediment and in terrace sediment is low and similar to the concentration in sediment from glacerized areas which indicates that the greenland ice sheet is the dominant source of sediment moving through the landscape outside the glacial margin in the areas we sampled copyright 2014 john wiley sons ltd

effect of alpine glaciation on thermochronometer age elevation profiles 1 low temperature thermochronometers are widely used to quantify exhumation histories typically by interpreting sample cooling age elevation relationships however the effects of specific geomorphic processes on age elevation profiles are seldom considered we integrate apatite u th he ahe apatite fission track and zircon u th he thermochronometry with numerical modeling to determine the effect of glacial erosion on an age elevation profile from the heavily glaciated southern coast mountains british columbia ahe data show a distinct break in slope in ageelevation between 1900 2100 m we interpret this break in slope as an acceleration of erosion associated with the onset ofalpineglaciation weusea3 dthermo kinematic modelto constrain pre and synglacial erosion rates results indicate a preglacial erosion rate of 0 4 mm yr that accelerated by a factor of 2 since 6 ma we propose that glacial valley widening and deepening are responsible for the observed nonlinear ahe age elevation profile citation densmore m s t a ehlers and g j woodsworth 2007 effect of alpine glaciation on thermochronometer age elevation profiles geophys res lett 34 l02502 doi 10 1029 2006gl028371

long term stratigraphic evolution of atlantic type passive margins a numerical approach of interactions between surface processes flexural isostasy and 3d thermal subsidence the thermal and flexural evolution of passive margins is impacted by the un loading effects of erosion sedimentation processes which in turn affect their relief and sediment accumulation these complex couplings are recorded by the stratigraphic trend of the associated sedimentary basins which is controlled by the balance between sediment accumulation subsidence and eustasy our objective is to constrain the relative contribution of the factors controlling the mechanical response of the lithosphere and the efficiency of the surface processes on parameters such as the denudation accumulation and uplift subsidence history and long termstratigraphic trends the novel aspect of our approach is to integrate the evolution of both domains in erosion and in sedimentation using state of the art modeling of the flexure of the lithosphere including the surface processes erosion sedimentation and the thermal evolution as well as concepts in sequence stratigraphy we investigated numerically the post rift evolution of passive margins testing the influence of the lithosphere s initial geometries thermal states and stretching profiles as well as the efficiency of the surface processes in all simulations the initial flexural rift shoulder is eroded away within 10 to 20 myr in the following stages the sedimentary supply and the evolution of the margin are mostly controlled by the flexural response to the thermal relaxation of the isotherms by cooling and the un loading mass transfer at the surface both the sediment accumulation controlled by relief relaxation and the subsidence rates decrease exponentially with time the evolution of their relative values forms a regressive transgressive sequence we show that variations in the efficiency of the surface processes may impact the uplift subsidence histories and the long term stratigraphic trend within the same range of magnitude as lithospheric parameters such as pre rift crust thickness or depth dependency of stretching the initial crustal thickness is then determinant in the denudation accumulation history whereas the margin width will impact the uplift subsidence history the second most depth of necking and effective elastic thickness are critical mostly during the initial phase of the margin history syn and immediate post rift whereas bulk sediment density and lithosphere thickness become critical in the late post rift

a stratigraphical basis for the last glacial maximum lgm abstract the last glacial maximum lgm is widely used to refer to the episode when global ice volume last reached its maximum and associated sea levels were at their lowest however the boundaries of the interval are ill defined and the term and acronym have no formal stratigraphical basis this is despite a previous proposal to define it as a chronozone in the marine records on the basis of oxygen isotopes and sea levels spanning the interval 23 19 or 24 18 ka and centred on 21 ka in terrestrial records the lgm is poorly represented since many sequences show a diachronous response to global climate changes during the last glacial cycle for example glaciers and ice sheets reached their maximum extents at widely differing times in different places in fact most terrestrial records display spatial variation in response to global climate fluctuations and changes recorded on land are often diachronous asynchronous or both leading to difficulties in global correlation however variations in the global hydrological system during glacial cycles are recorded by atmospheric dust flux and this provides a signal of terrestrial changes whilst regional dust accumulation is recorded in loess deposits global dust flux is best recorded in high resolution polar ice core records providing an opportunity to define the lgm on land and establish a clear stratigraphical basis for its definition on this basis one option is to define the global lgm as an event between the top end of greenland interstadial 3 and the base onset of greenland interstadial 2 spanning the interval 27 540 23 340 ka greenland stadial 3 this corresponds closely to the peak dust concentration in both the greenland and antarctic ice cores and to records of the global sea level minima this suggests that this definition includes not just the coldest and driest part of the last glacial cycle but also the peak in global ice volume the later part of the lgm event is marked by heinrich event 2 which reflects the onset of the collapse of the laurentide at c 24 ka together with other ice sheets in the north atlantic region a longer and later span for the lgm may be desirable although defining this in chronostratigraphical terms is problematic whichever formal definition is chosen this requires the contribution of the wider quaternary community

landscape preservation under fennoscandian ice sheets determined from in situ produced 10be and 26al some areas within ice sheet boundaries retain pre existing landforms and thus either remained as ice free islands nunataks during glaciation or were preserved under ice differentiating between these alternatives has significant implications for paleoenvironment ice sheet surface elevation and ice volume reconstructions in the northern swedish mountains in situ cosmogenic 10be and 26al concentrations from glacial erratics on relict surfaces as well as glacially eroded bedrock adjacent to these surfaces provide consistent last deglaciation exposure ages 8 13 kyr confirming ice sheet overriding as opposed to ice free conditions however these ages contrast with exposure ages of 34 61 kyr on bedrock surfaces in these same relict areas demonstrating that relict areas were preserved with little erosion through multiple glacial cycles based on the difference in radioactive decay between 26al and 10be the measured nuclide concentration in one of these bedrock surfaces suggests that it remained largely unmodified for a minimum period of 845 418 461 kyr these results indicate that relict areas need to be accounted for as frozen bed patches in basal boundary conditions for ice sheet models and in landscape development models subglacial preservation also implies that source areas for glacial sediments in ocean cores are considerably smaller than the total area covered by ice sheets these relict areas also have significance as potential long term subglacial biologic refugia

regional scale mid jurassic to late cretaceous unroofing from the adirondack mountains through central new england based on apatite fission track and u th he thermochronology abstract apatite fission track aft ages of 178 to 70 ma for 108 samples from the adirondack mountains and eastern new york state vermont western massachusetts and connecticut and western new hampshire indicate that widespread unroofing occurred throughout the region during the middle jurassic to late cretaceous additionally u th he ages of 167 to 85 ma were determined on nine of those samples and support cooling rates of 1 8 2 2 c m yr from 100 to 65 c during the middle jurassic to late cretaceous assuming a geothermal gradient of 25 c km unroofing rates for the region were estimated to be on average 0 07 0 08 km m yr the aft age discontinuities between the high peaks region and the fault dissected southeastern adirondack mountains and along the ammonoosuc fault in the connecticut river valley between vermont and new hampshire suggest differential unroofing that may have been accommodated by fault reactivation syn post late cretaceous time after the youngest aft ages 82 and 70 ma resp

local holocene environmental indicators in upper mesopotamia pedogenic carbonate record vs archaeobotanical data and archaeoclimatological models abstract it has been suggested that pedogenic carbonate coatings on stones in archaeological sites can be used to reconstruct late quaternary environmental changes in the area of the fertile crescent this research compares a pedogenic carbonate record from southeastern turkey with three other local or regional sources of palaeoenvironmental information in order to evaluate the correlation of this new proxy with other independent data from the area 1 ancient plant macroremains from archaeological sites as ecological indicators 2 stable carbon isotope composition of ancient plant macroremains available in the literature and from our own investigations in six mid holocene archaeological sites and 3 modelled holocene precipitation and temperature changes in the northern fertile crescent comparison involved selected palynological and isotopic data from lacustrine sediments as well as speleothem isotopic records in near eastern locations available in the literature although the data show a certain amount of variation of proxy records on the regional scale for the northern fertile crescent upper mesopotamia they suggest three pronounced features of the holocene environmental history 1 a trend toward warmer temperatures may have affected the area during the early holocene between ca 10 000 6000 cal bp 2 increased moisture availability and relatively high temperatures in the mid holocene ca between 5000 and 4000 cal bp and 3 a significant decrease in moisture availability around 4000 cal bp further research is needed to enhance the chronological resolution of both pedogenic carbonate and plant macrofossil records this study stresses the complexity of the holocene palaeogeography of the near east and underlines the need for careful analysis of local sources of palaeonvironmental information in the region

holocene climate and cultural evolution in late prehistoric early historic west asia abstract the precipitation climatology and the underlying climate mechanisms of the eastern mediterranean west asia and the indian subcontinent are reviewed with emphasis on upper and middle tropospheric flow in the subtropics and its steering of precipitation holocene climate change of the region is summarized from proxy records the indian monsoon weakened during the holocene over its northernmost region the ganges and indus catchments and the western arabian sea southern regions the indian peninsula do not show a reduction but an increase of summer monsoon rain across the holocene the long term trend towards drier conditions in the eastern mediterranean can be linked to a regionally complex monsoon evolution abrupt climate change events such as the widespread droughts around 8200 5200 and 4200 cal yr bp are suggested to be the result of altered subtropical upper level flow over the eastern mediterranean and asia the abrupt climate change events of the holocene radically altered precipitation fundamental for cereal agriculture across the expanse of late prehistoric early historic cultures known from the archaeological record in these regions social adaptations to reduced agro production in both dry farming and irrigation agriculture regions are visible in the archaeological record during each abrupt climate change event in west asia chronological refinement in both the paleoclimate and archaeological records and transfer functions for both precipitation and agro production are needed to understand precisely the evident causal linkages

late cretaceous reactivation of major crustal shear zones in northern namibia constraints from apatite fission track analysis abstract namibia s passive continental margin records a long history of tectonic activity since the proterozoic the orogenic belt produced during the collision of the congo and kalahari cratons in the early proterozoic led to a zone of crustal weakness which became the preferred location for tectonism during the phanerozoic the pan african damara mobile belt forms this intraplate boundary in namibia and its tectonostratigraphic zones are defined by ductile shear zones where the most prominent is described as the omaruru lineament waterberg thrust oml wt the prominance of the continental margin escarpment is diminished in the area of the central and northern zone of the damara belt where the shear zones are located this area has been targeted with a set of 66 outcrop samples over a 550 km long 60 km broad coast parallel transect from the top of the escarpment in the south across the damara sector to the kamanjab inlier in the north apatite fission track age and length data from all samples reveal a regionally consistent cooling event thermal histories derived by forward modelling bracket this phase of accelerated cooling in the late cretaceous maximum palaeotemperatures immediately prior to the onset of cooling range from ca 120 to ca 60 c with the maximum occurring directly south of the omaruru lineament because different palaeotemperatures indicate different burial depth at a given time the amount of denudation can be estimated and used to constrain vertical displacements of the continental crust we interpret this cooling pattern as the geomorphic response to reactivation of basement structures caused by a change in spreading geometry in the south atlantic and south west indian oceans

assessing the applicability of portable x ray fluorescence spectrometry for obsidian provenance research in the maya lowlands recent innovations in portable energy dispersive x ray fluorescence pxrf spectrometry have increased its utility for the geochemical characterization of obsidian artifacts for archaeological provenance research however concerns over the utility of pxrf instrumental analyses have been raised focused on the validity and reliability of the geochemical data produced here we adopt the framework of richard hughes on reliability validity and scale in obsidian sourcing research 1998 whereby reliability addresses instrument stability and issues of measurement while validity pertains to an instrument s ability to discern geochemical source provenance this is done in order to test the utility of pxrf instruments for archaeological provenance research k means cluster analysis was used to test the accuracy of pxrf through statistical comparison of data acquired via laboratory and portable energy dispersive xrf instruments multivariate analysis was employed to demonstrate obsidian source representation at two classic maya archaeological sites in southern belize uxbenka and ek xux and to test the validity of data obtained from a pxrf instrument in answering archaeological research questions pertaining to regional interactions between lowland maya polities results suggest that portable xrf instruments produce internally consistent results however data acquired from a pxrf instrument are not statistically equivalent to other xrf instruments this is to say that while pxrf is not a reliable technique it is valid for questions pertaining to geochemical source representation

denudation rates determined from the accumulation of in situ produced 10be in the luquillo experimental forest puerto rico we present a simple method for estimation of long term mean denudation rates using in situ produced cosmogenic 10be in fluvial sediments procedures are discussed to account for the effects of soil bioturbation mass wasting and attenuation of cosmic rays by biomass and by local topography our analyses of 10be in quartz from bedrock outcrops soils mass wasting sites and riverine sediment from the icacos river basin in the luquillo experimental forest puerto rico are used to characterize denudation for major landform elements in that basin the 10be concentration of a discharge weighted average of size classes of river sediment corresponds to a long term average denudation of 43 m ma 1 consistent with mass balance results

consistent slow exhumation in a late cenozoic glaciated landscape the presidential and carter ranges of the white mountains in new hampshire usa abstract to investigate the ability of the onset of quaternary glaciations to drive an acceleration in erosion rates we compare short timescale 103 104 yr erosion rates using the in situ terrestrial cosmogenic nuclide tcn 10be to longer time scale exhumation rates 106 107 yr using the apatite u th he method in the presidential and carter ranges of the white mountains in new hampshire usa our results are generally consistent with but refine previous studies using similar techniques resulting u th he ages and thermal modeling from mt washington in the presidential range n 4 91 7 to 117 3 ma suggest that exhumation rates from the late cretaceous to the present were slow

validity of off the shelf handheld portable xrf for sourcing near eastern obsidian chip debris handheld portable xrf hhpxrf has received considerable recent attention in archaeology especially for obsidian sourcing published studies largely suggest a high potential for success hhpxrf though has been met with debate and scepticism concerns fall into three categories 1 low accuracy and precision 2 data correction schemes and calibration and 3 ignorance of fundamental xrf issues such as specimen size limits and morphology effects the result is that archaeological interpretations in hhpxrf based studies are cast into doubt should interpretations be believed if authors did not follow the perceived best practices to address such questions the validity of hhpxrf for near eastern obsidian sourcing was tested under deliberately sub optimal conditions irregular obsidian debitage near the minimum size limits was sourced with a success rate of 94 based on a rank matches to 100 based on a and b rank matches even under conditions chosen to mimic off the shelf operation

dating of raised marine and lacustrine deposits in east greenland using beryllium 10 depth profiles and implications for estimates of subglacial erosion here we combine 10be depth profile techniques applied to late glacial ice contact marine and lacustrine deltas as well as boulder exposure dating of associated features in the scoresby sound region east greenland to determine both the surface age and the magnitude of cosmogenic nuclide inheritance boulder ages from an ice contact delta in northern scoresby sund show scatter typical of polar regions and yield an average age of 12 8 0 5 ka about 2 ka older than both our average profile surface age of 10 9 0 7 ka from three depth profiles and a radiocarbon based estimate on the other hand boulder exposure ages from a set of moraines in southern scoresby sund show excellent internal consistency for polar regions and yield an average age of 11 6 0 2 ka the profile surface age from a corresponding ice contact delta is 8 1 0 9 ka while a second delta yields an age of 10 0 0 4 ka measured 10be inheritance concentrations from all depth profiles are internally consistent and are between 10 and 20 of the surface concentrations suggesting a regional cosmogenic inheritance signal for the scoresby sound landscape based on the profile inheritance concentrations we explore the first order catchment averaged bedrock erosion under the greenland ice sheet yielding estimates of total erosion during the last glacial cycle of the order of 2 30 m copyright 2010 john wiley sons ltd

radiation damage control on apatite u th he dates from the grand canyon region colorado plateau individual detrital apatite grains from the esplanade coconino and moenkopi formations in the grand canyon region of the colorado plateau yield u th he dates from 104 to 5 ma the range of dates within each unit far exceeds analytical uncertainty but correlates with both he concentration he and effective u concentration eu these dates are all signifi cantly younger than the sandstone units indicating partial to complete he loss following deposition recently published laboratory diffusion data suggest that he retentivity in apatite increases with radiation damage forward models predict that the consequences of this effect will be manifested most clearly as a correlation between u th he dates and the he and eu in suites of apatites that 1 are characterized by a large span of eu and 2 had thermal histories in which suffi cient time elapsed for the apatite he diffusion kinetics to diverge prior to reheating and partial resetting apatites in the sedimentary units investigated fi t these cri teria using geologically reasonable deposition burial and unroofi ng histories simulations that include the effect of radiation damage on apatite he retentivity can reproduce the observed distributions of apatite dates and correlations with parent and daughter concentrations these results suggest that a span of u th he dates positively correlated with eu may provide important information regarding a sample s thermal history

u th he dating of phosphates apatite monazite and xenotime the common phosphate minerals apatite ca 5 po 4 3 f oh cl monazite ce la th po 4 and xenotime ypo 4 have found widespread use in geochronology because they incorporate u and th into their structures for example apatite usually has a few tens of ppm of both u and th while monazite and xenotime usually have hundreds of ppm to weight percent levels of these elements as a consequence these phosphates can be dated using several fundamentally different isotopic techniques elsewhere in this volume harrison et al describe phosphate dating using ingrowth of radiogenic pb the final daughter of u and th series decay and gleadow et al describe dating based on damage tracks from the spontaneous fission of 238 u the most recently developed dating technique applied to phosphates described in this chapter uses the accumulation of particles from u and th series decay u th he dating while phosphate u th pb dating is usually used to date high temperature events such as crystallization of igneous rocks and the timing of prograde metamorphism fission track and u th he dating are more commonly used to establish cooling histories through low temperatures for example in the range 110 40 c in the case of apatite dating of minerals using radiogenic he was first explored shortly after the discovery of radioactivity strutt 1908 and was investigated extensively in the 1950s and 1960s mostly on very u and th rich minerals such as zircon and titanite hurley 1952 1954 damon and kulp 1957 damon and green 1963 apatite he dating was first investigated by zeitler et al 1987 who studied the diffusion rate of he from apatite and proposed that apatite he dating might provide a useful thermochronometer recording cooling through about 100 c further studies both in the laboratory lippolt et al 1994 wolf et al 1996b warnock et al 1997 farley 2000 and in the natural setting house et al 1999 stockli et al 2000 have confirmed this idea and the technique has now been applied to a range of tectonic geologic and geomorphologic problems e g house et al 1997 1998 spotila et al 1997 farley et al 2001 stockli et al 2000 monazite and xenotime have only recently come under scrutiny for he geochronology e g pik and marty 1999 and little is yet known of their potential for routine geo or thermochronometry

a precise 40ar 39ar reference age for the durango apatite u th he and fission track dating standard the distinctive durango apatite is widely distributed as a reference material for mineralogy geochemistry and thermochronology the apatite occurs within the cerro de mercado open pit iron mine located in the northern portion of durango city mexico it is largely confined to vugs and open fractures within the lower portion of the ore deposit apatite and iron ore formed in situ and concurrently along with emplacement of small felsic intrusions along the southern margin of the chupaderos caldera complex this activity occurred between eruptions of two major ignimbrites from the caldera complex four single crystal sanidine anorthoclase 40 ar 39 ar ages from these ignimbrites and from a conformable older unit have been used to compute a reference age of 31 44 0 18 ma 2 for the apatite itself four additional multi crystal measurements are in general agreement with this age also in agreement are a set of 24 u th sm he ages recently determined directly on the apatite which have a mean of 31 02 1 01 ma 1 with a standard error s e of 0 22 ma

cosmogenic exposure age evidence for rapid laurentide deglaciation of the katahdin area west central maine usa 16 to 15 ka abstract katahdin the highest peak in maine and part of the second highest mountain range in new england provides an opportunity to assess the timing and style of continental ice sheet surface lowering during deglaciation we collected 14 samples from boulders on the adjacent basin ponds moraine from bedrock and boulders on the upper part of the mountain and from boulders in the surrounding area to estimate the age at which they were exposed by deglaciation of the laurentide ice sheet measurements of in situ produced 10be which are consistent with measurements of 26al indicate that the katahdin edifice became exposed from under ice by 15 3 2 1 ka n 6 an age indistinguishable from the adjacent basin ponds moraine 16 1 1 2 ka n 5 a boulder in the lowlands several km south of the moraine dates to 14 5 0 8 ka and a boulder deposited at pineo ridge about 170 km se of katahdin dates to 17 5 1 1 ka these data show that samples collected over an elevation range of 1 6 km and a distance of 170 km all have exposure ages that are indistinguishable within uncertainties together these data suggest that the laurentide ice sheet surface dropped rapidly and the ice sheet margin retreated quickly across maine between about 16 and 15 ka perhaps influenced by calving of the marine based ice sheet in the st lawrence lowlands to the north and the penobscot basin to the south

asymmetrical erosion and morphological development of the central ladakh range northern india abstract variations in erosion were quantified across the topographically and morphometrically asymmetrical central ladakh range in nw india to elucidate erosion and sediment transfer processes across space and time and to gain insight into how mountains erode and evolve morphometric analysis and 10 be cosmogenic nuclide analysis of 14 fluvial sediment samples from active channels in six catchments conducted across the mountain range constrains 100 ka timescale erosion rates for catchments on the northern side of the mountain range and are between 56 12 and 74 11 m ma while catchments on the southern side of the mountain range to between 20 3 and 39 8 m ma for the last 300 ka maximum elevation from swath analysis across the range shows a strong correlation with the elas of 382 contemporary glaciers the higher erosion rate to the north likely relates to tectonic tilting of the central ladakh range and to active rock uplift on the northern side of the range along the karakoram fault morphometric analysis shows that the maximum and average elevations increase at nearly the same rate on a catchment scale across the central ladakh range with higher elevation on the northern side this suggests that greater erosion on the northern side of the range is not keeping pace with rock uplift moreover long term denudational unloading does not play a significant role in the tectonic tilting of the central ladakh range