apatite fission track thermochronology of the southern appalachian basin maryland west virginia and virginia apatite fission track apparent ages 246 pm 37 to 95 pm 18 ma for 26 samples of upper devonian hampshire and chemung formations and middle devonian age tioga ash bed from the southern appalachian basin of maryland virginia and west virginia along with confined track length distributions for 13 of these samples suggest that uplift was contemporaneous with triassic jurassic extension along the atlantic continental margin uplift as measured by apatite fission track analysis began earliest in the northwestern section on the cumberland plateau at sim225 pm 25 ma this area probably required the least amount of erosional unroofing 3 1 km samples from the valley and ridge province of northern west virginia virginia and maryland yield progressively younger apatite fission track apparent ages to the east ranging from 163 pm 10 to 95 pm 18 ma this is consistent with deeper burial in the eastern appalachian basin as indicated by increasing cai indices and geodynamic modeling t

changing tectonic controls on the long term carbon cycle from mesozoic to present tectonic drivers of degassing and weathering processes are key long term controls on atmospheric co2 however there is considerable debate over the changing relative importance of different carbon sources and sinks existing geochemical models have tended to rely on indirect methods to derive tectonic drivers such as inversion of the seawater 87sr 86sr curve to estimate uplift or continental basalt area here we use improving geologic data to update the representation of tectonic drivers in the copse biogeochemical model the resulting model distinguishes co2 sinks from terrestrial granite weathering total basalt weathering and seafloor alteration it also distinguishes co2 sources from subduction zone metamorphism and from igneous intrusions we reconstruct terrestrial basaltic area from data on the extent of large igneous provinces and use their volume to estimate their contribution to degassing we adopt a recently published reconstruction of subduction related degassing and relate seafloor weathering to ocean crust creation rate revised degassing alone tends to produce unrealistically high co2 but this is counteracted by the inclusion of seafloor alteration and global basalt weathering producing a good overall fit to mesozoic cenozoic proxy co2 estimates and a good fit to 87sr 86sr data the model predicts that seafloor alteration and terrestrial weathering made similar contributions to co2 removal through the triassic and jurassic after which terrestrial weathering increased and seafloor weathering declined we predict that basalts made a greater contribution to silicate weathering than granites through the mesozoic before the contribution of basalt weathering declined over the cenozoic due to decreasing global basaltic area

erosion rates in and around shenandoah national park virginia determined using analysis of cosmogenic 10be we use cosmogenic 10be analysis of fluvial sediments and bedrock to estimate erosion rates 104 105 year timescale and to infer the distribution of post orogenic geomorphic processes in the blue ridge province in and around shenandoah national park virginia our sampling plan was designed to investigate relationships between erosion rate and lithology mean basin slope basin area and sediment grain size fifty nine samples were collected from a variety of basin sizes inferred erosion rates for the medium sand fraction of all fluvial samples from all lithologies range from 3 0 to 21 m my the area weighted mean erosion rate for single lithology basins in the park is 12 2 m my single lithology erosion rate ranges for fluvial samples are granite 7 0 to 20 m my metabasalt 3 8 to 21 m my quartzite 3 8 to 15 m my and siliciclastic rocks 5 2 to 15 m my multilithology basins erode at rates between 3 0 16 m my the shenandoah river basin 3305 km2 is eroding at 6 6 m my bedrock erosion rates range from 1 8 to 11 m my across all lithologies with a mean of 6 5 4 3 m my grain size specific 10be analysis of four samples showed no consistent trend of concentration with grain size cosmogenic analysis of bedrock and sediment from the shenandoah national park area allows us to speculate about why some parts of the appalachian mountains erode more slowly and some more rapidly overall it appears that steep drainage basins erode more rapidly than gently sloped basins climate and lithology may also influence basin scale rates of erosion as suggested by the difference in average erosion rates east and west of the divide and the difference between the erosion rates of quartzite and granite dominated basins data are conflicting in regards to the evolution of relief over time analyses made of exposed bedrock along ridgelines suggest that such rock is eroding either more slowly than adjacent drainage basins susquehanna river shenandoah national park region or at similar rates great smoky mountains providing a mechanism for growing relief at the scale of individual ridgelines however considering relief on a landscape or physiographic province scale by comparing erosion rates of the highlands versus the lowlands suggests that relief of the range as a whole is either steady or very slowly decreasing over multi millennial timescales the presence of significant erosion rate slope relationships negates a broad hackian view of the landscape because there is not uniform erosion across this landscape the aspect erosion rate and slope erosion rate relationships present in the shenandoah area suggest that the landscape is not fully adjusted to rock strength

heat flow and thermal conductivity measurements in the northeastern pennsylvania appalachian basin depocenter the northern appalachian basin depocenter of pennsylvania represents one of the most economically important hydrocarbon producing areas in the united states yet the thermal conditions that promoted hydrocarbon formation within the basin are only marginally constrained the prolific coal oil and natural gas fields of pennsylvania are the direct result of thermal maturation of once deeply buried organic rich sediment understanding how why and where thermal maturation occurred in the appalachian basin requires high quality heat flow and thermal conductivity measurements as well as paleotemperature estimates and basin modeling to improve the understanding of heat flow we present to our knowledge the first direct measurements of 1 thermal conductivity on devonian core samples and 2 equilibrium temperature versus depth logs for the northern appalachian basin depocenter results from three well sites demonstrate that heat flow is conductive and nearly uniform averaging 34 2 5 mw m2 with an average thermal gradient of 29 4 c km the new heat flow measurements are significantly lower 30 50 less than previously published estimates that used nonequilibrium bottomhole temperature values and empirically derived thermal conductivity estimates our analysis indicates that previous studies correctly estimated the regional thermal gradient using bottomhole temperatures but overestimated heat flow in this region by as much as 50 because of inaccurate extrapolation of thermal conductivity the results highlight the importance of directly measuring thermal conductivity to accurately quantify heat flow in deep sedimentary basins ultimately additional paleotemperature data are necessary to improve our understanding of appalachian basin thermal evolution

a modeling case for high atmospheric oxygen concentrations during the mesozoic and cenozoic changes in atmospheric oxygen concentration over earth history are commonly related to the evolution of animals and plants but there is no direct geochemical proxy for o2 levels meaning that estimations rely heavily on modeling approaches the results of such studies differ greatly to the extent that today s atmospheric mixing ratio of 21 might be either the highest or lowest level during the past 200 m y long term oxygen sources such as the burial in sediments of reduced carbon and sulfur species are calculated in models by representation of nutrient cycling and estimation of productivity or by isotope mass balance imb a technique in which burial rates are inferred in order to match known isotope records studies utilizing these different techniques produce conflicting estimates for paleoatmospheric o2 with nutrient weathering models estimating concentrations close to or above that of the present day and imb models estimating low o2 especially during the mesozoic here we re assess the imb technique using the copse biogeochemical model imb modelling is confirmed to be highly sensitive to assumed carbonate 13c and when this input is defined following recent compilations predicted o2 is significantly higher and in reasonable agreement with that of non imb techniques we conclude that there is no model based support for low atmospheric oxygen concentrations during the past 200 m y high mesozoic o2 is consistent with wildfire records and the development of plant fire adaptions but links between o2 and mammal evolution appear more tenuous

post paleocene cooling in the southern canadian atlantic region evidence from apatite fission track models the traditional view of the geomorphic evolution of the southern canadian atlantic margin is one of gradual exhumation and peneplanation following triassic jurassic rifting thermal modelling of apatite fission track data from pre carboniferous granitic basement in nova scotia and from permian and triassic sandstones from nova scotia new brunswick and prince edward island suggest a more complex thermal evolution of the onshore part of the margin models clearly indicate significantly elevated regional paleotemperatures during jurassic time and as much as 30 c of post paleocene cooling model predicted paleogeothermal gradients for granitic samples from the digby d 1 well are normal ranging from 15 to 20 c km post paleocene cooling may be attributable to the combined effects of 13 c of exhumational cooling from erosion of approximately 700 m of post aptian sediments caused by decreased eustatic sea levels and 8 17 c of cooling from the propagation to depth of a 10 20 c decrease in paleo mean ann

pleistocene holocene transition in benelux in benelux belgium the netherlands and luxembourg considerable progress in late glacial and early postglacial archaeological and environmental research has been made during the last decade a substantial part of this paper discusses new evidence on the chronology of the industries which occupied the southern part of benelux dating the occupations from the sandy north is still problematic long after the glacial maximum during which the area remained uninhabited the south of benelux was visited by magdalenian hunter gatherers while hamburgian settlements were present in the north the significance of the continental creswellian is debated during the allerod interstadial federmesser groups occupied most of the area abandoning it with the onset of the younger dryas the presence of the ahrensburgian during that stadial may have been punctuated new elements were introduced and were maintained during the development of the preboreal early mesolithic which eventually colonised the entire region throughout this sequence changes in material culture and related subsistence activities are evident in view of the major problems concerning the quality of the chrono ecological data this paper can only suggest provisional explanations in terms of human reactions to changing environmental conditions

phanerozoic atmospheric oxygen new results using the geocarbsulf model modifications of the geocarbsulf model for phanerozoic atmospheric oxygen have been made to account for new carbon isotopic data reconsideration of the fractionation of carbon isotopes between carbonate and organic matter deposited in sediments and different rates of weathering of volcanic rocks versus granitic rocks results indicate distinctly higher o2 values than geocarbsulf for the mesozoic and cenozoic lack of an appreciable drop in o2 below 15 percent at any time and a small late cenozoic decline of o2 to the present

new constraints on the late cenozoic incision history of the new river virginia abstract the new river crosses three physiogeologic provinces of the ancient tectonically quiescent appalachian orogen and is ideally situated to record variability in fluvial erosion rates over the late cenozoic active erosion features on resistant bedrock that floors the river at prominent knickpoints demonstrate that the river is currently incising toward base level however thick sequences of alluvial fill and fluvial terraces cut into this fill record an incision history for the river that includes several periods of stalled downcutting and aggradation we used cosmogenic 10be exposure dating aided by mapping and sedimentological examination of terrace deposits to constrain the timing of events in this history 10be concentration depth profiles were used to help account for variables such as cosmogenic inheritance and terrace bioturbation fill cut and strath terraces at elevations 10 20 and 50 m above the modern river yield model cosmogenic exposure ages of 130 600 and 600 950 ka respectively but uncertainties on these ages are not well constrained these results provide the first direct constraint on the history of alluvial aggradation and incision events recorded by new river terrace deposits the exposure ages yield a long term average incision rate of 43 m my which is comparable to rates measured elsewhere in the appalachians during specific intervals over the last 1 ma however the new river s incision rate reached 100 m my modern erosion rates on bedrock at a prominent knickpoint are between 28 and 87 m my in good agreement with rates calculated between terrace abandonment events and significantly faster than 2 m my rates of surface erosion from ancient terrace remnants fluctuations between aggradation and rapid incision operate on timescales of 104 105 year similar to those of late cenozoic climate variations though uncertainties in model ages preclude direct correlation of these fluctuations to specific climate change events these second order fluctuations appear within a longer term signal of dominant aggradation until 2 ma followed by dominant incision a similar signal is observed on other appalachian rivers and may be the result of sediment supply fluctuations driven by the increased frequency of climate changes in the late cenozoic

dating transcurrent terrane accretion an example from the meguma and avalon composite terranes in the northern appalachians the polygenetic minas geofracture separates the meguma and avalon composite terranes of the maritime appalachians dynamically recrystallized muscovite and biotite occur within d3 shear zones which developed during dextral movement along the geofracture these record 40ar 39ar plateau ages between circa 360 and 370 ma comparable plateau ages are recorded by micas within undeformed portions of granitic plutons and their low pressure contact metamorphic aureoles these are similar to u pb ages previously reported for igneous monazite therefore indicating relatively rapid postmagmatic cooling at shallow crustal levels the d3 fabrics were superimposed on earlier s1 structures which formed during initial amalgamation of the meguma and avalon composite terranes whole rock slate phyllite samples collected outside high temperature portions of the plutonic contact aureoles yield 40ar 39ar plateau ages which correspond to groupings of circa 400 395 ma 390 385 ma and 380 375 ma these are interpreted to date diachronous formation of the s1 fabrics and concomitant low grade regional metamorphism in the circa 25 ma between initial amalgamation and granitic plutonism it is inferred that there was a slow rise of isotherms through the crust as a result of overthrust tectonic thickening this led to crustal melting and the production of widespread granitic magmas which were emplaced immediately prior to d3 dextral shearing

stable carbon isotopes of c3 plant resins and ambers record changes in atmospheric oxygen since the triassic estimating the partial pressure of atmospheric oxygen po2 in the geological past has been challenging because of the lack of reliable proxies here we develop a technique to estimate paleo po2 using the stable carbon isotope composition d 13 c of plant resins including amber copal and resinite from a wide range of localities and ages triassic to modern plant resins are particularly suitable as proxies because their highly cross linked terpenoid structures allow the preservation of pristine d 13 cs ignatures over geological timescales the distribution of d 13 c values of modern resins n 126 indicates that a resin producing plant families generally have a similar fractionation behavior during resin biosynthesis and b the fractionation observed in resins is similar to that of bulk plant matter resins exhibit a natural variability in d 13 c of around 8 d 13 cr ange 31 to 23 m ean 27 which is caused by local environmental and ecological factors e g water availability water composition light exposure temperature nutrient availability to minimize the effects of local conditions and to determine long term changes in the d 13 co f resins we used mean d 13 c values d 13 c resin for each geological resin deposit fossil resins n 412 are generally enriched in 13 c compared to their modern counterparts with shifts in d 13 c resin of up to 6 these isotopic shifts follow distinctive trends through time which are unrelated to post depositional processes including polymerization and diagenesis the most enriched fossil resin samples with a d 13 c resin between 22 and 21 formed during the triassic the mid cretaceous and the early eocene experimental evidence and theoretical considerations suggest that neither change in pco2 nor in the d 13 c of atmospheric co2 can account for the observed shifts in d 13 c resin the fractionation of 13 c in resin producing plants d 13 c instead is primarily influenced by atmospheric po2 with more fractionation occurring at higher po2 the enriched d 13 c resin values suggest that atmospheric po2 during most of the mesozoic and cenozoic was considerably lower po2 10 20 than today po2 21 in addition a correlation between the d 13 c resin and the marine d 18 o record implies that po2 pco2 and global temperatures were inversely linked which suggests that intervals of low po2 were generally accompanied by high pco2 and elevated global temperatures intervals with the lowest inferred po2 including the mid cretaceous and the early eocene were preceded by large scale volcanism during the emplacement of large igneous provinces lips this suggests that the influx of mantle derived volcanic co2 triggered an initial phase of warming which led to an increase in oxidative weathering thereby further increasing greenhouse forcing this process resulted in the rapid decline of atmospheric po2 during the mid cretaceous and the early eocene greenhouse periods after the cessation in lip volcanism and the decrease in oxidative weathering rates atmospheric po2 levels continuously increased over tens of millions of years whereas co2 levels and temperatures continuously declined these findings suggest that atmospheric po2 had a considerable impact on the evolution of the climate on earth and that the d 13 c of fossil resins can be used as a novel tool to assess the changes of atmospheric compositions since the emergence of resin producing plants in the paleozoic

geologic history of seawater a magic approach to carbon chemistry and ocean ventilation abstract we explore the relationship between atmospheric o 2 and co 2 evolution and seawater chemistry with particular focus on the co 2 carbonic acid system and ocean ventilation over the phanerozoic eon using a coupled biogeochemical earth system model magic this model describes the biogeochemical cycles involving the major components of seawater ca mg na k cl so 4 co 2 hco 3 co 3 as well as components o 2 fe p organic c reduced s central to long term ecosystem productivity the magic calculations show that the first order input fluxes from weathering of continental rocks of ca mg and dissolved inorganic carbon dic to the ocean varied in a cyclical manner over the phanerozoic the cyclicity is mainly the result of the impact of changing atmospheric co 2 levels and hence temperature and runoff on these fluxes reflecting the nature of hothouse greenhouse high co 2 and warm versus icehouse low co 2 cool and continental glaciation conditions during the phanerozoic uptake of dic by seafloor basalt seawater reactions also varied in a corresponding fashion to the weathering fluxes the fluxes of ca mg dic and other seawater constituents removed in oceanic sinks were also calculated and hence with calculated inputs and outputs of seawater constituents the changes in seawater chemistry through phanerozoic time could be obtained seawater ph increased irregularly during the phanerozoic from just above 7 in the cambrian period approaching modern average values in the most recent several millions of years calcite saturation state also increased with decreasing age both ph and calcite saturation state trends exhibited a cyclic overprint of hothouse and icehouse environmental conditions dissolved sulfate changed in a cyclical manner reflecting mainly variations in weathering and accretion rates and redox conditions whereas dissolved potassium exhibited little variation in concentration using our standard model results for the chemistry of seawater and changes in atmospheric co 2 and o 2 as the basis for a series of sensitivity experiments we vary the ventilation rate of the global ocean and quantify the resulting changes in terms of processes such as net primary production organic carbon burial and oxidation pyrite weathering and sulfate reduction we use these preliminary results to discuss how changes in ocean ventilation affect atmospheric co 2 and o 2 and in turn exert changes in the sulfur organic carbon and inorganic carbon systems we postulate that periods of slow plate accretion rates associated with lower atmospheric co 2 vigorous deep water formation cooler drier climatic conditions and greater poleward temperature gradients are more likely to be associated with a strong thermohaline circulation and thus enhanced global ocean mixing conversely periods of higher accretion rates higher co 2 higher average global temperatures with more equable poleward gradients and higher sea levels resulting in extensive continental inundation would be more likely to be coincident with times of reduced mixing of the global ocean it is important to recognize that the scale of these changes depends on how major tectonic cycles controlling chemical weathering co 2 and temperature in turn affect nutrient supply global ocean productivity and global ocean thermohaline circulation the key to elucidating these changes lies in an understanding of the relationship between long term tectonic evolution which leads to changes in climate sea level and the global distribution of continental landmasses and the sedimentary environments they host and the circulation of the global ocean

apatite fission track thermochronology of the pennsylvania appalachian basin thirty four apatite fission track apparent ages and twenty four track length distributions for ash bed samples from the valley and ridge province and upper devonian to upper pennsylvania sedimentary samples from the allegheny front and allegheny plateau of pennsylvania suggest that these regions represent different thermal uplift regimes as well as different structural provinces the valley and ridge province tioga and kalkberg ash bed samples yield apatite fission track apparent ages and track length distributions that indicate early post alleghanian 285 270 ma cooling and unroofing that began at 250 ma assuming a geothermal gradient of 25 c km 1 a burial depth of at least 3 4 km can be estimated for all the pennsylvania samples at the allegheny structural front and on the western allegheny plateau the apatite fission track apparent ages 150 ma and track length measurements indicate a late jurassic early cretaceous thermal event for these samples possibly resulting from a higher geothermal gradient coinciding with kimberlite intrusion at this time along the greene potter fault zone in northeast pennsylvania on the allegheny plateau the upper paleozoic sedimentary samples yield apatite fission track apparent ages 180 ma narrow track length distributions with long mean lengths 13 14 m and small standard deviations 1 3 m suggest rapid cooling from temperatures 110 c during the middle jurassic early cretaceous for this part of pennsylvania this is consistent with the suggested uplift history of the catskill mountain region in adjacent new york state

error analysis of co2 and o2 estimates from the long term geochemical model geocarbsulf long term carbon and sulfur cycle models have helped shape our understanding of the phanerozoic history of atmospheric co 2 and o2 but error analyses have been largely limited to testing only a subset of input parameters singly as a result the full ranges of probable co2 and o 2 are not quantitatively known here we investigate how variation in all 68 input parameters of the geocarbsulf model both singly and in combination affect estimated co 2 and o 2 we improve formula tions for land area runoff and continental temperature the latter of which now excludes land area not experiencing chemical weathering we find our resampled model co 2 and o2 estimates are well bounded and provide high confidence for a double hump in co2 during the phanerozoic with high values during the early paleozoic and mesozoic and low values during the late paleozoic and late mesozoic to cenozoic our analyses also support a distinct atmospheric o2 peak during the late paleozoic 30 followed by low values near the triassic jurassic boundary 10 most of the spread in co2 is contributed by three factors climate sensitivity to co 2 doubling and the plant assisted chemical weathering factors life and gym c o2 estimates during the paleozoic to early mesozoic are highly concordant with indepen dent records from proxies but are offset to lower values during the globally warm late mesozoic to early cenozoic the model proxy mismatch for the late mesozoic can be eliminated with a change in gym within its plausible range but no change within plausible ranges can resolve the early cenozoic mismatch either the true value for one or more input parameters during this interval is outside our sampled range or the model is missing one or more key processes

nature origin and production characteristics of the lower silurian regional oil and gas accumulation central appalachian basin united states low permeability sandstones of the lower silurian regional oil and gas accumulation cover about 45 000 mi2 117 000 km2 of the appalachian basin and may contain as much as 30 tcf of recoverable gas resources major reservoirs consist of the clinton sandstone and medina group sandstones the stratigraphically equivalent tuscarora sandstone increases the area of the lower silurian regional accumulation lsra by another 30 000 mi2 78 000 km2 approximately 8 7 tcf of gas and 400 million bbl of oil have been produced from the clinton medina reservoirs since 1880 the eastern predominantly gas bearing part of the lsra is a basin center gas accumulation whereas the western part is a conventional oil and gas accumulation with hybrid features of a basin center accumulation the basin center accumulations have pervasive gas saturation water near irreducible saturation and generally low fluid pressures in contrast the hybrid conventional accumulations have less pervasive oil and gas saturation higher mobile water saturation and both normal and abnormally low fluid pressures high mobile water saturation in the hybrid conventional reservoirs form the updip trap for the basin center gas creating a broad transition zone tens of miles wide that has characteristics of both end member accumulation types although the tuscarora sandstone part of the basin center gas accumulation is pervasively saturated with gas most of its constituent sandstone beds have low porosity and permeability commercial gas fields in the tuscarora sandstone are trapped in naturally fractured faulted anticlines the origin of the lsra includes 1 generation of oil and gas from ordovician black shales 2 vertical migration through an overlying 1000 ft 305 m thick ordovician shale 3 abnormally high fluid pressure created by oil to gas transformation 4 updip displacement of mobile pore water by overpressured gas 5 entrapment of pervasive gas in the basin center 6 postorogenic uplift and erosion causing gas leakage and a marked reduction in fluid pressure most future natural gas production in the clinton medina sandstones is anticipated to come from the basin center accumulation the tuscarora sandstone has additional gas resources but typically low reservoir porosity and permeability and the likelihood of low energy in british thermal units gas reduce the incentive to explore for it

biotic enhancement of weathering atmospheric oxygen and carbon dioxide in the neoproterozoic 1 it has been suggested that biological colonization of the land surface began in the neoproterozoic 1000 544 million years ago ma we hypothesize that this colonization involved selective weathering of p from rocks as well as an amplification of overall weathering rates we show that two recent models despite differences in the feedback mechanisms represented predict that an increase in the weathering flux of p to the ocean would have caused a rise in atmospheric o2 in the neoproterozoic this in turn may have provided a necessary condition for the evolution of animals with hard skeletons seen in the cambrian explosion increased weathering of silicate rocks would also have caused a decline in atmospheric co2 which could have been a causal factor in the neoproterozoic glaciations

evidence for differential unroofing in the adirondack mountains new york state determined by apatite fission track thermochronology abstract apatite fission track ages of 168 83 ma for 39 samples of proterozoic crystalline rocks three samples of cambrian potsdam sandstone and one cretaceous lamprophyre dike from the adirondack mountains in new york state indicate that unroofing in this region occurred from late jurassic through early cretaceous samples from the high peaks section of the adirondack massif yielded the oldest apatite fission track ages 168 135 ma indicating that it was exhumed first unroofing along the northern northwestern and southwestern margins of the adirondacks began slightly later as shown by younger apatite fission track ages 146 114 ma determined for these rocks this delay in exhumation may have resulted from burial of the peripheral regions by sediment shed from the high peaks apatite fission track ages for samples from the southeastern adirondacks are distinctly younger 112 83 ma than those determined for the rest of the adirondack region these younger apatite fission track ages are from a sec

distribution of maximum burial temperatures across northern appalachian basin and implications for carboniferous sedimentation patterns clay mineral diagenesis and apatite fission track age data indicate that the maximum burial temperatures to which the middle devonian tioga metabentonite was exposed rise abruptly from low values in western new york state to higher values in the east the highest temperatures which approach 175 sup 0 c were reached just west of syracuse neither the pattern nor the magnitude of burial temperatures can be explained solely by burial of the metabentonite beneath upper devonian sediments although spatial variations in the geothermal gradient could have produced the observed pattern of burial temperatures it is more likely that carboniferous sediments no longer preserved in the area were responsible for the indicated burial the inferred presence of thick carboniferous sequences in western new york state suggests that the allegheny orogeny had a stronger influence on sedimentation in the northern appalachian basin than has been previously recognized 25 references 2 figures 2 tables

phanerozoic concentrations of atmospheric oxygen reconstructed from sedimentary charcoal varying concentrations of atmospheric oxygen have affected the development of animals and the role of wildfire in ecosystems reconstructions of past oxygen concentrations from fossil charcoal constrain atmospheric oxygenation over the past 400 million years variations of the earth s atmospheric oxygen concentration po2 are thought to be closely tied to the evolution of life with strong feedbacks between uni and multicellular life and oxygen1 2 on the geologic timescale po2 is regulated by the burial of organic carbon and sulphur as well as by weathering3 reconstructions of atmospheric o2 for the past 400 million years have therefore been based on geochemical models of carbon and sulphur cycling4 5 6 however these reconstructions vary widely4 5 6 7 8 9 10 particularly for the mesozoic and early cenozoic eras here we show that the abundance of charcoal in mire settings is controlled by po2 and use this proxy to reconstruct the concentration of atmospheric oxygen for the past 400 million years we estimate that po2 was continuously above 26 during the carboniferous and permian periods and that it declined abruptly around the time of the permian triassic mass extinction during the triassic and jurassic periods po2 fluctuated cyclically with amplitudes up to 10 and a frequency of 20 30 million years atmospheric oxygen concentrations have declined steadily from the middle of the cretaceous period to present day values of about 21 we conclude however that variation in po2 was not the main driver of the loss of faunal diversity during the permo triassic and triassic jurassic mass extinction events

sedimentary corg p ratios paleocean ventilation and phanerozoic atmospheric po2 the corg p ratios of organic rich facies tocn1 exhibit considerable variation through the phanerozoic from b10 1 in the permian phosphoria formation to n1000 1 in some devonian black shales relative to the composition of phytoplankton c p 106 1 which provide the bulk of organic c and p to organic rich marine sediments the range of phanerozoic sedimentary corg p ratios largely reflects the influence of benthic redox conditions on diagenetic pathways of c and p remobilization enhanced preservationoforganiccatlowerredoxpotentials combinedwithenhancedsedimentaryretentionofremineralizedorganicpathigher redox potentials results in a strong relationship between benthic redox conditions and sedimentary corg p ratios the strong secular coherence of the phanerozoic corg p record i e limited variation within narrow time slices suggests that these ratios are controlled primarily by factors influencing benthic redox conditions on a global scale such as atmospheric po2 inversion and scaling of the phanerozoic corg p record yields a new atmospheric po2 model that has strong similarities to existing models based on elemental and isotopic mass balances yet differs in some potentially significant respects in particular the new model suggests that atmospheric po2 wasmarkedlylowerduringtheearlytomiddlepaleozoicthanpreviouslyinferred duringmostofthedevonian atmospherico2levels mayhavebeensufficientlylow b13 astopreventthesustainedcombustionofplantmaterial thisfeatureofthemodelmayaccount for ananomalous gapinthefossilcharcoalrecordduringthedevonian theredox dependentburialofpintheoceanresults inpositive and negative feedback mechanisms that tend to stabilize atmospheric oxygen concentrations on geologic timescales temporal variations in the burial of p relative to c suggest that the strength of these feedback mechanisms varied over the phanerozoic 2007 elsevier b v all rights reserved

changes in mid and far field human landscape use following the laacher see eruption c 13 000 bp abstract around 13 000 years ago the laacher see volcano east eifel volcanic field rhenish shield erupted cataclysmically the thick tephra blanket in the eruption s near field covered and thereby preserved a large number of archaeological sites ranging from very small to some of the largest and richest sites known from the late glacial in this proximal region there is a striking contrast in the number of sites prior to the eruption and the almost complete lack of sites dating to the period after the event i e to greenland interstadial 1a the preservative function of the tephra cover itself may explain this near field pattern but it is shown here that similar stratigraphic observations can also be made in the laacher see eruption s mid field towards the west and in particular to the north east the aim of this paper is to review the stratigraphic relations of known archaeological sites outside the near field of the laacher see event with a particular focus on the german federal state of hesse and adjacent areas of lower saxony and the thuringian basin here a number of archaeological sites are known where strata of laacher see tephra cap human occupation most often these sites are not reoccupied until much later in prehistory suggesting that the eruption may have led either to a complete or a near complete abandonment of the affected regions or at the very least to a major reorganisation of landscape use

diamonds from the iridium rich k t boundary layer at arroyo el mimbral tamaulipas mexico diamonds up to 30 m in size were found in the iridium rich layer from the k t boundary site at arroyo el mimbral and the spherule bed from arroyo el penon northeastern mexico stepped heating experiments indicate two or more isotopically distinct diamond components with carbon isotopic compositions characteristic of a mixture of carbon sources the diamonds crystal form is cubic not the hexagonal polymorph of diamond lonsdaleite which has been used previously to infer formation due to shock transformation of graphite the size crystallography and mineralogic associations of k t diamonds are similar to those of impact produced diamonds from the ries crater in germany where both shock transformation of graphite and a mode of formation by condensation from a vapor plume have been inferred the discovery of impact produced diamonds in association with high ir contents for these sediments supports their impact origin k t age and the inference that their source was from the buried impact crater of chicxulub on the yucatan peninsula mexico

thermal history of rocks in southern san joaquin valley california evidence from fission track analysis the theory of the fission track method and its application to sedimentary basin analysis is illustrated by a case study in the southern san joaquin valley california fission tracks provide a powerful tool for studying the thermal history of sedimentary basins because the two minerals most commonly used in fission track studies apatite and zircon occur as detrital constituents in many sedimentary rocks and their annealing temperatures span the main temperature range for oil generation fission tracks also provide information on the sedimentation record and provenance of rocks in a basin we have used fission track analysis to study the thermal and depositional history of the subsurface tertiary sedimentary rocks on both sides of the active white wolf reverse fault in the southern san joaquin valley the distinctly different thermal histories of the rocks in the two structural blocks are clearly reflected in the apatite fission track data which suggest that rocks in the rapidly subsiding basin northwest of the fault have been near their present temperature for only about 1 m y compared with about 10 m y for rocks southeast of the fault these estimates of heating time agree with previous estimates for these rocks zircon fission track data indicate that the tertiary sediments were derived from parent rocks of more than one age however from at least the eocene to late miocene or pliocene the major sediment source was rocks related to the youngest sierra nevada mesozoic intrusive complexes which are presently exposed east and south of the southern san joaquin valley

character of the alleghanian orogeny in the southern appalachians part iii regional tectonic relations geological and geochronological studies in the eastern piedmont of the southern appalachians have documented a polyphase late paleozoic deformational chronology d 2 d 4 that is contemporaneous with the alleghanian orogeny recorded in the western appalachian foreland the scale and vergence of d 3 anticlinoria in the eastern piedmont are similar to those of anticlinoria in the western appalachians which are related to ramping of underlying thrust surfaces we suggest that the appalachian decollement extends southeastward beneath the entire piedmont province and that all of the piedmont rocks were displaced at least 175 km northwestward relative to north america during the alleghanian orogeny late paleozoic deformational effects in the eastern piedmont thus are considered cogenetic with alleghanian foreland deformation we interpret the alleghanian orogeny to be the result of oblique dextral convergence and collision of gondwana and laurentia

time temperature burial significance of devonian anthracite implies former great 6 5 km depth of burial of catskill mountains new york specimens of coalified plant debris in tully correlative strata of the gilboa formation uppermost middle devonian within the eastern catskill mountains of new york state have been converted to anthracite having a vitrinite reflectance of 2 5 this implies a level of organic metamorphism lom of 16 the specimens are about 350 m y old if 200 m y is taken as the duration of the time of exposure to the maximum geothermal temperature then the lom of 16 and other thermal indicators imply a maximum temperature of 190 sup 0 c using a geothermal gradient of 26 sup 0 c km sup 1 17 sup 0 f 1 000 ft sup 1 a former depth of burial of 6 5 km is implied such former deep burial is not usually inferred for the catskills but it is consistent with the idea that the thick about 6 4 km or 21 000 ft carboniferous strata of northeastern pennsylvania formerly extended northeast far enough to bury the catskills the lack of metamorphism of the paleozoic strata lying about 4 5 km beneath the tully correlative rocks and exposed in the adjacent hudson valley places low limits on the former geothermal gradient this supports the concept of great depth of former burial of the catskills for example 6 5 km of former burialmore and a geothermal gradient of 26 sup 0 c km sup 1 imply a temperature of 307 sup 0 c for the base of the paleozoic by contrast only 1 km of former burial requires a geothermal gradient of 170 sup 0 c km sup 1 which would have subjected the base of the paleozoic to a temperature of 955 sup 0 gamma which is far higher than the 600 to 650 sup 0 c recently inferred for the acadian age metamorphism of the taconic allochthon in southwestern massachusetts and adjoining areas less

biological overprint of the geological carbon cycle the oxidation of earth s atmosphere is coupled to the net sequestration of organic matter which is related to the relative fractions of organic carbon forg and carbonate fcarb buried in marine sediments these fractions can be inferred from carbon isotope data we present bulk sediment d 13 c records of carbonate d 13 ccarb and organic carbon d 13 corg with a compilation of evolutionary trajectories of major eucaryotic phytoplankton for the past 205 million years our analysis indicates that changes in phytoplankton community structure coupled with the opening of the atlantic ocean basin and global sea level rise increased the efficiency of organic carbon burial beginning in the early jurassic in turn this organic carbon burial increased the oxidation state of earth s surface while drawing down atmospheric co2 levels assuming no substantial negative feedbacks the net oxidation and co2 drawdown appear to be related to the opening phase of the current wilson cycle where the newly formed passive plate margins store organic matter for hundreds of millions of years this process should reverse during the closing phase of the wilson cycle when the continents reassemble and the atlantic ocean basin closes the associated oxidation and storage of organic matter have contributed to the long term depletion of co2 which was a key factor that selected c4 photosynthetic pathways in marine and terrestrial ecosystems in the latter part of the cenozoic these pathways increasingly influenced d 13 corg and ultimately contributed to the reversal of the long term trend in d 13 ccarb

the effect of long term atmospheric changes on the macroevolution of birds abstract atmospheric conditions are critical for a range of biological functions locomotion among others and long term changes in these conditions have been identified as causal for different macroevolutionary patterns here we examine the influence of variations in atmospheric o2 concentration aoc temperature tair and air density air on the power efficiency as it relates to locomotion during the evolutionary history of birds specifically our study centers on four key evolutionary events 1 the body mass reduction of non avian theropods prior to the rise of birds 2 the emergence of flapping flight in the earliest birds 3 the divergence of basal pygostylians and 4 the diversification of modern birds our results suggest that a marked increase in aoc and air during the middle jurassic coeval with a trend in miniaturization improved the power efficiency of the dinosaurian predecessors of birds likewise an increase in these conditions is hypothesized as having played a major role in the diversification of early pygostylians during the early cretaceous however our analyses do not identify any significant paleoatmospheric effects on either the emergence of flapping flight or the early cladogenesis of modern birds extinct birds flew within the range of atmospheric conditions in which modern birds fly but varying past conditions influenced their flight performance our study thus highlights the importance of considering paleoatmospheric conditions when reconstructing the flight efficiency of the forerunners of modern birds

low rates of bedrock outcrop erosion in the central appalachian mountains inferred from in situ 10be bedrock outcrops are common on central appalachian mountain ridgelines because these ridgelines define watersheds the rate at which they erode influences the pace of landscape evolution to estimate ridgeline erosion rates we sampled 72 quartz bearing outcrops from the potomac and susquehanna river basins and measured in situ produced 10 be ridgeline erosion rates average 9 1 m m y 1 median 6 m m y 1 similar to 10 be derived rates previously reported for the region the range of erosion rates we calculated reflects the wide distribution of samples we collected and the likely inclusion of outcrops affected by episodic loss of thick slabs and periglacial activity outcrops on main ridgelines erode slower than those on mountainside spur ridges because ridgelines are less likely to be covered by soil which reduces the production rate of 10 be and increases the erosion rate of rock ridgeline outcrops erode slower than drainage basins in the susquehanna and potomac river watersheds suggesting a landscape in disequilibrium erosion rates are more similar for outcrops meters to tens of meters apart than those at greater distances yet semivariogram analysis suggests that outcrop erosion rates in the same physiographic province are similar even though they are hundreds of kilometers apart this similarity may reflect underlying lithological and or structural properties common to each physiographic province average 10 be derived outcrop erosion rates are similar to denudation rates determined by other means sediment flux fission track thermochronology u th he dating indicating that the pace of landscape evolution in the central appalachian mountains is slow and has been since post triassic rifting events

the murray springs clovis site pleistocene extinction and the question of extraterrestrial impact some of the evidence for the recent hypothesis of an extraterrestrial impact that caused late pleistocene megafaunal extinctions firestone et al 2007 proc natl acad sci usa 104 16016 16021 was based upon samples collected at murray springs a clovis archaeological site in southeastern arizona here we describe sampling and analyses of magnetic separates from within above and below the lower younger dryas boundary lydb black mat at murray springs as well as radiation measurements from the lydb at murray springs and two other well stratified clovis sites the main magnetic fraction at murray springs is maghemite magnetic microspherules have terrestrial origins but also occur as cosmic dust particles we failed to find iridium or radiation anomalies the evidence for massive biomass burning at murray springs is addressed and found to be lacking we could not substantiate some of the claims by firestone and others but our findings do not preclude a terminal pleistocene cosmic event

wildfire and abrupt ecosystem disruption on california s northern channel islands at the allerod younger dryas boundary 13 0 12 9 ka abstract sedimentary records from california s northern channel islands and the adjacent santa barbara basin sbb indicate intense regional biomass burning wildfire at the allerod younger dryas boundary 13 0 12 9 ka all age ranges in this paper are expressed in thousands of calendar years before present ka radiocarbon ages will be identified and clearly marked 14c years multiproxy records in sbb ocean drilling project odp site 893 indicate that these wildfires coincided with the onset of regional cooling and an abrupt vegetational shift from closed montane forest to more open habitats abrupt ecosystem disruption is evident on the northern channel islands at the allerod younger dryas boundary with the onset of biomass burning and resulting mass sediment wasting of the landscape these wildfires coincide with the extinction of mammuthus exilis pygmy mammoth the earliest evidence for human presence on these islands at 13 1 12 9 ka 11 000 10 900 14c years is followed by an apparent 600 800 year gap in the archaeological record which is followed by indications of a larger scale colonization after 12 2 ka although a number of processes could have contributed to a post 18 ka decline in m exilis populations e g reduction of habitat due to sea level rise and human exploitation of limited insular populations we argue that the ultimate demise of m exilis was more likely a result of continental scale ecosystem disruption that registered across north america at the onset of the younger dryas cooling episode contemporaneous with the extinction of other megafaunal taxa evidence for ecosystem disruption at 13 12 9 ka on these offshore islands is consistent with the younger dryas boundary cosmic impact hypothesis firestone r b west a kennett j p becker l bunch t e revay z s schultz p h belgya t kennett d j erlandson j m dickenson o j goodyear a a harris r s howard g a kloosterman j b lechler p mayewski p a montgomery j poreda r darrah t que hee s s smith a r stich a topping w wittke j h wolbach w s 2007 evidence for an extraterrestrial impact 12 900 years ago that contributed to the megafaunal extinctions and younger dryas cooling proceedings of the national academy of sciences 104 16016 16021

applications of low temperature thermochronometry to quantification of recent exhumation in mountain belts exhumation is a primary phenomenon used to characterize geomorphic and tectonic histories the motion of rock with respect to the earth s surface is produced by erosion and tectonic denudation unroofing by erosion redistributes crustal mass and is a major accommodator of shortening in orogenic belts brandon et al 1998 zeitler et al 2001 willett et al 2003 tectonic denudation typically associated with crustal extension brings rocks to the surface at rapid rates from significant crustal depths hodges et al 1998 hacker et al 2003 vanderhaeghe et al 2003 quantifying exhumation using thermochronology is thus an important element in investigations of long term crustal scale geomorphic and tectonic processes the thermochronometers most appropriate for estimating exhumation related to landscape or neotectonic history are apatite u th he and fission track dating given their low closure temperatures and the typical geothermal gradient of the continents these cooling ages generally record exhumation from 1 4 km depths farley 2002 ehlers and farley 2003 naeser 1979 gleadow et al 1986 the accuracy of the exhumation history inferred from these data is limited by how well the spatially and temporally variant geothermal gradient is known or modeled mancktelow and grasemann 1997 ehlers and farley 2003 beyond these limitations thermochronology is often hindered by what the rocks in a given study area record cooling ages may be too old and predate the tectonic or erosional history of interest or topography accessibility bedrock lithology and exposure may hinder collection of a robust sample set in many studies experimental design is determined by logistics available funding and time and prior analytical training of the investigator thus some studies may not obtain the optimal results to address a given question although many papers deal with technical aspects of thermochronometry the purpose of this paper is to explore

three dimensional 3 d finite strain at the central andean orocline and implications for grain scale shortening in orogens three dimensional 3 d finite strain analyses from across the central andes are used to document the contribution of grain scale strain in quartzites and sandstones to the total shortening budget the results are compared to thermal stratigraphic and strain data from other fold and thrust belts to determine the influence of lithologic strength and deformation temperature on strain accommodation during orogenic evolution in the central andes 3 d best fit ellipsoids are inconsistently oriented relative to structural trends have short axes at high angles to bedding z mean plunge 78 21 and have bedding parallel long axes x mean plunge 6 24 ellipsoid shapes are dominantly oblate x y z indicate low natural octahedral shear strains e s 0 03 0 19 and have axial ratios that range from 1 02 1 0 81 e s 0 19 to 1 02 1 0 97 e s 0 03 highly variable r f data r f 1 0 5 0 fluctuations exceeding 100 indicate detrital grain shapes may overwhelm any measurable tectonic strain fabric recorded by grain geometry the best fit ellipsoids may reflect either weak compaction strain or they may be related to a depositional fabric at a minimum granular strain was insufficient to reset the detrital grain fabric and therefore grain scale strain in quartzites and sandstones is not a significant factor in deformation we suggest that the nonstrained nature of these stiffer lithologies indicates a lack of regional penetrative strain in the central andes like that quantified in similar lithologies in other orogens the regional lack of strain may be due to deformation temperatures

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

black shale source rocks and oil generation in the cambrian and ordovician of the central appalachian basin usa nearly 600 million bbl of oil mmbo and 1 to 1 5 trillion ft3 tcf of gas have been produced from cambrian and ordovician reservoirs carbonate and sandstone in the ohio part of the appalachian basin and on adjoining arches in ohio indiana and ontario canada most of the oil and gas is concentrated in the giant lima indiana field on the findlay and kankakee arches and in small fields distributed along the knox unconformity based on new geochemical analyses of oils potential source rocks bitumen extracts and previously published geochemical data we conclude that the oils in both groups of fields originated from middle and upper ordovician black shale utica and antes shales in the appalachian basin moreover we suggest that approximately 300 mmbo and many trillions of cubic feet of gas in the lower silurian clinton sands of eastern ohio originated in these same source rocks oils from the cambrian and ordovician reservoirs have similar saturated hydrocarbon compositions biomarker distributions and carbon isotope signatures regional variations in the oils are attributed to differences in thermal maturation rather than to differences in source total organic carbon content genetic potential regional extent and bitumen extract geochemistry identify the black shale of the utica and antes shales as the most plausible source of the oils other cambrian and ordovician shale and carbonate units such as the wells creek formation which rests on the knox unconformity and the rome formation and conasauga group in the rome trough are considered to be only local petroleum sources tmax cai and pyrolysis yields from drill hole cuttings and core indicate that the utica shale in eastern and central ohio is mature with respect to oil generation burial thermal and hydrocarbon generation history models suggest that much of the oil was generated from the utica antes source in the late paleozoic during the alleghanian orogeny a pervasive fracture network controlled by basement tectonics aided in the distribution of oil from the source to the trap this fracture network permitted oil to move laterally and stratigraphically downsection through eastward dipping impermeable carbonate sequences to carrier zones such as the middle ordovician knox unconformity and to reservoirs such as porous dolomite in the middle ordovician trenton limestone in the lima indiana field some of the oil and gas from the utica antes source escaped vertically through a partially fractured leaky upper ordovician shale seal into widespread lower silurian sandstone reservoirs

local controls on carbon cycling in the ordovician midcontinent region of north america with implications for carbon isotope secular curves abstract the carbon isotope record from ancient epicontinental seas may contain much more of a local scale carbon cycling signal than is generally appreciated a unique opportunity exists to examine this issue in the case of the late ordovician mohawkian sea of eastern laurentia where the millbrig k bentonite stratigraphic framework has been used to delineate a time slice at 454 ma extending over 1 500 000 km2 of the eastern united states across the time slice carbonate and organic carbon 13c vary by 4 5 and 7 5 respectively a spatial variation that is as large as temporal secular changes in epeiric sea 13c that have been reported in the past these new data are considered in the context of geographic variations in lithological biological and other geochemical sediment characteristics collectively these sediment properties distinguish regions of the mohawkian sea which likely differed in terms of the nature and relative importance of carbon cycling processes water column depth and structure and barriers to free exchange of water across the mohawkian sea may have been overarching factors in the development of these regions raising the possibility that changes in circulation patterns such as those caused by sea level change played a role in driving secular carbon isotope excursions by changing the rate of exchange of dissolved inorganic carbon between water masses if the observed effects of local carbon cycling on the distribution of mohawkian sea 13c were commonplace in ancient epicontinental marine environments it would imply that local scale carbon cycling may have left a nontrivial imprint on epeiric sea records of secular variations in 13c in addition to the imprint left by changes in the global carbon cycle this may have contributed to the broad scatter in 13c values observed in the paleozoic portion of the global carbon isotope secular curve

evidence of transient topographic disequilibrium in a landward passive margin river system knickpoints and paleo landscapes of the new river basin southern appalachians the upper new river basin of the southern appalachian mountains a major tributary of the modern ohio river represents the unglaciated headwaters of the tertiary teays river system of eastern north america dating of relict fluvial gravels have suggested that new river incision may be outpacing lowering of the surrounding uplands but physical evidence of transient topographic disequilibrium has yet to be identified we use focused topographic analysis of the upper new river basin to delineate a perched low relief paleo landscape that is experiencing transgressive dissection due to incision by the new river and its tributaries accelerated incision has decoupled hillslopes from the drainage network generating knickpoints which represent the boundary between remnants of the paleo landscape and actively adjusting topography downstream steepening of hillslopes downstream of knickpoints suggests dynamic headward migration which along with knickpoint occurrence throughout the drainage network is inconsistent with the development of fixed stream profile convexities atop strike extensive geologic contacts in the absence of tectonic forcing we favor a climatically forced drop in external base level as driver of the incision pattern we observe plio pleistocene glacial damming and diversion of the teays river to form the modern ohio river lowered regional base level for the study area potentially forcing the paleo landscape developed during the teays era to adjust to the modern drainage pattern the upper new river may therefore represent the potential for glacially driven drainage rearrangement to drive transient topographic evolution hundreds of kilometers away from the ice margin long after the disappearance of ice sheets copyright 2013 john wiley sons ltd

deep burial diagenesis its implications for vertical movements of the crust uplift of the lithosphere and isostatic unroofing a review abstract various techniques of study of strata exposed at the surface in undeformed areas of the appalachian basin and ozark done imply that these strata have been heated to temperatures that suggest a former great depth of burial the data reveal that the strata have been much more deeply buried than previously thought if such former deep burial has taken place then subsequent uplift and erosion must also have taken place to bring these formerly deeply buried strata to the present land surface unexpectedly large amounts of uplift and erosion ranging from 4 3 to 7 km have re exposed these formerly deeply buried rocks this leads to the surprising conclusion that isostatic unroofing has stripped off thick sections of strata whose presence was previously unsuspected therefore the lithosphere in its isostatic unroofing of thick sequences of sedimentary strata has undergone much larger vertical motions than many geologists had previously estimated case histories in this review include strata of the silurian of the northern appalachian basin and of the ordovician of the ozark dome which reached interpreted maximum burial depths of 5 and 4 3 km respectively devonian strata in the catskill mountains of new york imply a former depth of burial of 6 5 km lower ordovician carbonate sequences of the northern appalachian basin imply a depth of burial in excess of 7 km middle ordovician strata from the same basin signify a depth of burial of approximately 5 km and devonian strata a paleodepth of 4 5 5 km such former great depths of burial of undeformed strata which are now exposed at the surface reflect large scale vertical movements of the crust and uplift of the lithosphere these drastic changes represent isostatic unroofing with widespread implications for paleogeography of a kind unrecognized at present

hunter gatherer responses to the changing environment of the moervaart palaeolake nw belgium during the late glacial and early holocene abstract this paper presents new geo archaeological perspectives on the late glacial and early holocene human occupation around a large palaeolake the moervaart palaeolake 25 km 2 intensive fieldwork using invasive and non invasive survey techniques combined with modelling of the palaeotopography and palaeogroundwater and multi proxy palaeoecological analyses have resulted in a detailed reconstruction of the landscape during the final palaeolithic and early mesolithic occupation of the area a major shift in the occupation from the federmesser culture to the early mesolithic was contemporaneous with a sudden and drastic change in the palaeohydrology of the area between ca 13 300 and 13 000 cal bp end of allerod which coincided with a short but abrupt cooling event known as the intra allerod cold period iacp gi 1b it is assumed that this event triggered the sudden drying up of the moervaart palaeolake and surrounding ponds which until then had provided federmesser hunter gatherers with extensive and fertile grounds for hunting gathering and drinking water the population decline which followed this hydrological event was reinforced by the prevailing cold and harsh conditions of the younger dryas and probably lasted until the pre boreal hunter gatherers returned to the area in the boreal now settling along the proximal floodplain regions of a meandering channel which was connected with the southern scheldt river

a new model for atmospheric oxygen over phanerozoic time a mathematical model has been constructed that enables calculation of the level of atmospheric o2 over the past 570 my from rates of burial and weathering of organic carbon c and pyrite sulfur s burial rates as a function of time are calculated from an assumed constant worldwide clastic sedimentation rate and the relative abundance and c and s contents of the three rock types marine sandstones and shales coal basin sediments and other non marine clastics red beds arkoses by our model values of o2 versus time using a constant total sedimentation rate agree with those for variable sedimentation derived from present day rock abundances and estimates of erosional losses since deposition this agreement is the result of our reliance on the idea that any increase in total worldwide sediment burial with consequently faster burial of c and s and greater o2 production must be accompanied by a corresponding increase in erosion and increased exposure of c and s on the continents to o2 consumption via weathering it is the redistribution of sediment between the three different rock types and not total sedimentation rate that is important in o2 control to add stability to the system negative feedback against excessive o2 fluctuation was provided in the modeling by the geologically reasonable assignment of higher weathering rates to younger rocks resulting in rapid recycling of c and s we did not use direct o2 negative feedback on either weathering of c and s or burial of c because weathering rates are assumed to be limited by uplift and erosion and the burial rate of c limited by the rate of sediment deposition the latter assumption is the result of modern sediment studies which show that marine organic matter burial occurs mainly in oxygenated shallow water and is limited by the rate of supply of nutrients to the oceans by rivers results of the modeling indicate that atmospheric o2 probably has varied appreciably over phanerozoic time during the late carboniferous and permian periods o2 was higher than previously because of the rise of vascular land plants and the widespread burial of organic matter in vast coal swamps a large decrease in o2 during the late permian was due probably to the drying up of the coal swamps and deposition of a large proportion of total sediment in c and s free continental red beds sensitivity study shows that major parameters affecting results are the mean c concentration in coal basins and the relative sizes of the reservoirs of young rapidly recycled versus old rocks less sensitivity was found for changes over time in total land area undergoing weathering and the use of direct o2 negative feedback on marine carbon burial good agreement for rates of c burial calculated via our model and via independent models which are based on the use of stable carbon isotopes indicates that the dominant factor that has brought about changes in atmospheric o2 level and the isotopic composition of dissolved inorganic carbon in seawater over phanerozoic time is sedimentation and not weathering or higher temperature phenomena such as basalt seawater reaction

fungus not comet or catastrophe accounts for carbonaceous spherules in the younger dryas impact layer 1 a claim attributes the onset of the younger dryas climate interval and a range of other effects 12 900 years ago to a comet airburst and or impact event one key aspect of this claim centers on the origin of carbonaceous spherules that purportedly formed during intense impact ignited wildfires samples from pleistocene holocene sedimentary sequences in the california channel islands and other sites show that carbon spherules and elongate forms are common in samples dating to before during and well after the 12 900 year time horizon including from modern samples microscopic studies show that carbon spherules have morphologies and internal structures identical to fungal sclerotia such as sclerotium and cenococcum experimental charring of fungal sclerotia shows that their reflectance increases with temperature reflectance measurements of modern and late pleistocene spherules show that the latter indicate at most low intensity burning these data cast further doubt upon the evidence suggesting a catastrophic younger dryas impact event

character of the alleghanian orogeny in the southern appalachians part ii geochronological constraints on the tectonothermal evolution of the eastern piedmont in south carolina a nearly concordant u pb zircon age of 550 4 ma is interpreted to closely date crystallization of the epizonal little mountain metatonalite in the southeastern part of the charlotte belt in south carolina this confirms field studies which indicate that the charlotte belt contains a plutonic metaigneous complex that developed as a sub volcanic arc infrastructure contemporaneous with vulcanism manifested in the carolina slate belt both paleontological and geochronological controls indicate that the south carolina slate belt is mostly younger than 570 ma cambrian whereas the slate belt in north carolina and virginia is mostly of late proterozoic age a regionally significant mid paleozoic ca 340 360 ma thermal event is suggested by discordant 40ar 39ar whole rock age spectra of slate phyllite in the northwestern carolina slate belt and from hornblende in the southeastern charlotte belt it is uncertain if this event was associated with deformation in the eastern piedmont however mid paleozoic deformation has been previously documented elsewhere in the western piedmont a slightly disconcordant u pb zircon age of 317 4 ma is interpreted to closely date initial crystallization of the deformed edge field granite and confirms a record of late paleozoic penetrative deformation in the kiokee belt of south carolina u pb isotope data for the lake murray orthogneiss and clouds creek granite are discordant and suggest that the magmas of these plutons were derived by partial melting of a sialic precam brian source and then emplaced in the eastern piedmont at ca 315 ma prior to or during the early stages of the alleghanian orogeny the thermal maximum of alleghanian regional metamorphism amphibolite facies in the kiokee belt greenschist facies in the southeastern part of the carolina slate belt occurred during ca 295 315 ma during the late carboniferous and early permian the eastern piedmont experienced differential uplift erosion and relatively rapid postmeta morphic cooling isothermal surfaces were folded into an antiform synform antiform configuration corresponding to the kiokee carolina slate and charlotte belts respectively the geochronological data provide the following calibration for the late paleozoic deformational chronology recorded in the kiokee and carolina slate belts d2 lake murray deformation ca 295 315 ma d3 clarks hill deformation ca 285 295 ma and d4 irmo deformation ca 268 290 ma

calcite and quartz microstructural geothermometry of low grade metasedimentary rocks northern range trinidad abstract the northern range of trinidad is a mountainous exposure of deformed metasedimentary rocks with mesozoic depositional ages and tertiary metamorphic ages located in the caribbean south american plate boundary zone these rocks lack precise mineralogical indicators of metamorphic grade using temperature sensitive quartz and calcite microstructures and fission track data we identify describe quantify and map a nearly continuous spectrum of relatively low l50 c to relatively high 250 400 c deformation temperatures from east to west across the range average estimated rock exhumation rates also increase systematically along this trend the analysis illuminates a sharp east west trending major thermal discontinuity i e a fault along the southern boundary of the range kinematic analysis of faults and shear bands adjacent to this boundary and modeling indicate that the fault probably dips southward at 80 85 and accommodated normal dip slip at rates that decreased from west to east earlier experimental studies at high strain rates illustrated a strong strain rate dependency for quartz microstructural transitions our work indicates a possible strong temperature control for quartz microstructural transitions at natural strain rates

character of the alleghanian orogeny in the southern appalachians part i alleghanian deformation in the eastern piedmont of south carolina the eastern piedmont province in south carolina contains a sequence of cambrian volcanic and sedimentary rocks that was penetratively deformed d1 and regionally metamorphosed m1 to the greenschist facies during the early and or middle paleozoic the eastern piedmont was subsequently affected by late paleozoic alleghanian polyphase deformation d2 d4 and regional metamorphism the earliest alleghanian event d2 is associated with amphibolite facies regional metamorphism and felsic plutonism in a mid crustal infrastructure at ca 295 315 ma the gradational interface between infrastructure and overlying suprastructure contained a steep m2 metamorphic gradient between amphibolite facies below and greenschist facies above numerous sheets of felsic orthogneiss and a deformation front marking the upper limit of intense d2 penetrative deformation d3 is represented by northwestward vergent folding of s1 and s2 foliations and m2 isothermal surfaces the kiokee belt in south carolina is interpreted as a d2 infrastructure exposed within the core of a d3 antiform this interpretation suggests that an alleghanian infrastructure may be present in the subsurface beneath much of the piedmont and coastal plain the polygenetic modoc zone forms the northwest boundary of the kiokee belt it is interpreted to represent an interface between d2 infrastructure and suprastructure which was rotated into a steep northwest dipping attitude during development of the kiokee belt antiform between ca 267 and 290 ma portions of the kiokee belt modoz zone and carolina slate belt were overprinted by ductile deformation d4 along steeply dipping northeast trending dextral shear zones

low marine sulfate concentrations and the isolation of the european epicontinental sea during the early jurassic two records of seawater sulfate isotope composition from the early jurassic demonstrate that large isotopic gradients existed between the european epicontinental sea and the open tethys ocean these differences can be explained by the modification of open ocean sulfate isotopic compositions by water mass isolation sea level rise and the effects of changing regional weathering and pyrite burial fluxes during a time of rapid environmental change both records contain large positive isotopic excursions in the section from europe yorkshire uk a 6 excursion begins in the early exaratum subzone of the toarcian in the middle of the organic rich shale representing a well known oceanic anoxic event an open tethyan margin record from tibet records a much larger 19 excursion but the section is less well dated two age interpretations are possible sparse biostratigraphic evidence places this excursion in the aalenian but we suggest that it may correlate with the positive excursion in yorkshire hence these records may document both a toarcian event and an aalenian sulfur isotope event or the early toarcian anoxic event alone conservative estimates of the rate of isotopic change with time based on the tibetan section suggest that early jurassic seawater sulfate concentrations were between 1 and 5 mm much lower than previously thought

evidence of widespread wildfires in coal seams from the middle jurassic of northwest china and its impact on paleoclimate abstract today wildfire is an important disturbance in many continental ecosystems and it is assumed that with ongoing climate changes the frequencies and impacts of wildfires will increase in many regions one way to obtain information about the potential long term influences of wildfires on ecosystems and the climate system itself is to study palaeo wildfires a total of 140 jurassic samples including 122 coal samples and 18 rock samples from roof and floor of coal seams were collected from 4 coalfields in northwestern china the samples were analyzed by macropetrography microscopy scanning electron microscopy gas chromatography and gas chromatography mass spectrometry to study the evidences of wildfires and their impact on the paleoclimate high contents of pyrogenic inertinites charcoal natural char and natural coke particles observed in the samples which indicate that widespread wildfire events occurred in the early middle jurassic in all over northwestern china additionally high molecular weight polycyclic aromatic hydrocarbons were detected in the coal samples these aromatic compounds were formed under high temperature and provide further evidence of wildfires according to a carbon emission model for modern forest fires the total carbon and gas emissions from wildfires in peat swamps of the middle jurassic in northwest china were calculated by the data from 21 575 coal samples of number of 1567 drill core samples the total carbon released from peat swamp forest wildfires was at least 1207 gt corresponding to emissions of co2 co and ch4 of 1926 gt 163 gt and 8 8 gt respectively the huge amount of co2 released by forest fires in the peat swamp systems of the middle jurassic in northwestern china alone was equivalent to 64 20 of the total co2 in the atmosphere at present 3000gt the large amounts of greenhouse gases released by wildfires must have led to long term changes in the atmospheric composition and have caused global warming which could have the reason of affected the paleoclimate

the absolute age of the eifelian tioga ash bed pennsylvania the tioga ash bed bed b of the zeigler pit union county pennsylvania lies in the polygnathus costatus costatus zone of the eifelian stage of the middle devonian series the 27 5 cm thick bed contains igneous zircon and monazite crystals that have been dated by precise u pb techniques zircons are characterized by inherited pb that occurs as barely perceptible interior regions enriched in inclusions the zircons are discordant and do not reveal the igneous age of the bed in contrast high quality monazite crystals lack any evidence of inheritance or loss of pb and multiple analyses have overlapping 207 pb 235 u ages of 390 0 pm 0 5 ma the monazite analyses are concordant or very slightly reversely discordant the consistency of the monazite data provides a new precise estimate of age for the lower eifelian

evidence from central mexico supporting the younger dryas extraterrestrial impact hypothesis we report the discovery in lake cuitzeo in central mexico of a black carbon rich lacustrine layer containing nanodiamonds microspherules and other unusual materials that date to the early younger dryas and are interpreted to result from an extraterrestrial impact these proxies were found in a 27 m long core as part of an interdisciplinary effort to extract a paleoclimate record back through the previous interglacial our attention focused early on an anomalous 10 cm thick carbon rich layer at a depth of 2 8 m that dates to 12 9 ka and coincides with a suite of anomalous coeval environmental and biotic changes independently recognized in other regional lake sequences collectively these changes have produced the most distinctive boundary layer in the late quaternary record this layer contains a diverse abundant assemblage of impact related markers including nanodiamonds carbon spherules and magnetic spherules with rapid melting quenching textures all reaching synchronous peaks immediately beneath a layer containing the largest peak of charcoal in the core analyses by multiple methods demonstrate the presence of three allotropes of nanodiamond n diamond i carbon and hexagonal nanodiamond lonsdaleite in order of estimated relative abundance this nanodiamond rich layer is consistent with the younger dryas boundary layer found at numerous sites across north america greenland and western europe we have examined multiple hypotheses to account for these observations and find the evidence cannot be explained by any known terrestrial mechanism it is however consistent with the younger dryas boundary impact hypothesis postulating a major extraterrestrial impact involving multiple airburst s and and or ground impact s at 12 9 ka

nanodiamonds and wildfire evidence in the usselo horizon postdate the allerod younger dryas boundary the controversial younger dryas impact hypothesis suggests that at the onset of the younger dryas an extraterrestrial impact over north america caused a global catastrophe the main evidence for this impact after the other markers proved to be neither reproducible nor consistent with an impact is the alleged occurrence of several nanodiamond polymorphs including the proposed presence of lonsdaleite a shock polymorph of diamond we examined the usselo soil horizon at geldrop aalsterhut the netherlands which formed during the allerod early younger dryas and would have captured such impact material our accelerator mass spectrometry radiocarbon dates of 14 individual charcoal particles are internally consistent and show that wildfires occurred well after the proposed impact in addition we present evidence for the occurrence of cubic diamond in glass like carbon no lonsdaleite was found the relation of the cubic nanodiamonds to glass like carbon which is produced during wildfires suggests that these nanodiamonds might have formed after rather than at the onset of the younger dryas our analysis thus provides no support for the younger dryas impact hypothesis

popigai crater origin and distribution of diamond bearing impactites about three decades ago a formerly unknown genetic type of natural diamonds was discovered in impact craters impact diamonds are currently known from a number of impact structures in europe asia and north america and it s likely that the number of finds will increase with time the popigai crater northern siberia where impact diamonds were first found was specifically investigated in terms of geology geophysics petrography and mineralogy large resources of industrial impact diamonds were discovered and these minerals were studied in detail authigenic impact diamonds occur in situ in shocked graphite bearing gneisses that are found as inclusions in impact melt rocks tagamites and suevites according to the observed transformation of coexisting minerals the lower estimated pressure of the coherent martensite transition of graphite to diamonds is 35 gpa impact diamonds inherit the original shape of graphite crystals and are composed of a polycrystalline structured aggregate of cubic and probably hexagonal carbon microcrystals 1 5 m across numerous properties of diamonds depend on the high density of defects in the crystal lattice allothigenic impact diamonds occur in rocks produced by the homogenization and solidification of impact melt which originated from the complete fusion of graphite bearing precursor gneisses these diamonds usually reflect the influence of the hot melt and are strongly corroded diamond bearing tagamites and suevites in the popigai crater interior occur as extended lens and sheets bodies and also as irregular small bodies diamond distribution depends on the original abundance of precursor graphite in the target rocks on the superimposed shock metamorphic zonation and on the character of the ejection of shocked and melted material along different trajectories and azimuths this has resulted in radial and concentric inhomogeneities in diamond distribution in the crater interior on a second order the distribution depends on the scale of melt contamination by clasts and fragments and by the duration of cooling of certain melt bodies and their constituents enrichment in diamonds at the margins of thick tagamite sheets is the result of rapid cooling which prevents combustion of diamonds a positive correlation between diamond content and the amount of phosphorus pentoxide in impactites indicates links to c and p probably in organic matter of the primary sedimentary rocks which were subjected to granulitic metamorphism 2 4 ga ago and melted at the time of impact 35 7 ma ago

paleomagnetism and 40ar 39ar ages from the carolina slate belt albemarle north carolina implications for terrane amalgamation with north america paleomagnetic and sup 40 ar sup 39 ar dating studies of late proterozoic metamorphic rocks from the carolina slate belt were undertaken to gain insight into the history of this suspect lithostratigraphic terrane geochronological data suggest a peak metamorphic age of ca 455 ma and a later thermal overprint at ca 185 ma thermal demagnetization indicates two magnetization components a low temperature component yields a pole close to 180 190 ma segments of the north american apparent polar wander path a high temperature component postdates folding and is inferred to have been acquired at ca 455 ma corresponding paleomagnetic pole is lat 20 sup 0 n long 80 sup 0 e although paleomagnetic data from the carolina slate belt remain too ambiguous for construction of a unique polar wander path consideration of available paleolatitudes suggests that the terrane may have been proximal to cratonic north america after ca 455 ma this result contrasts markedly with high southerly ordovician paleolatitudes inferred from paleomagnetic studies within central and northern appalachian terranes

a sealed flint knapping site from the younger dryas in the scheldt valley belgium bridging the gap in human occupation at the pleistocene holocene transition in w europe based on the evidence of a recently excavated sealed site situated at ruien rosalinde in the belgian scheldt valley the response of hunter gatherers to changing climate at the transition from the temperate allerod to the cold younger dryas is discussed radiocarbon dated to the end of the allerod or the very beginning of the younger dryas the site of ruien provides the earliest evidence of a refined lithic technology characterized by the use of a soft stone hammer and the production of straight and regular blade let s from intensively prepared cores with two opposite platforms and sharp striking angles in the course of the younger dryas and early pre boreal this knapping method will become standard all over europe from the tanged point technocomplex in the north to the epi laborian in the south it contrasts sharply with the knapping style of previous lithic traditions such as the late federmesser azilian and bromme technocomplexes which was much less elaborated and mainly oriented towards the knapping of short irregular blades with a hard stone hammer this apparently abrupt technological change was also accompanied by increased raw material procurement networks extending over up to 250 km and a marked microlithisation of the hunting equipment finally the site of ruien is also important as it demonstrates the limited archaeological visibility of younger dryas sites explaining the scarcity of such sites within western europe

geologic controls on bedrock channel width in large slowly eroding catchments case study of the new river in eastern north america abstract we have investigated the geologic controls on hydraulic geometry of bedrock rivers using a single large catchment the new river from a stable tectonic setting with variable resistant lithology but spatially stable climate our survey of channel width at 0 5 km spacing along 572 km of the river shows major variation that only roughly fits the expected scaling relationships between width drainage area and slope considerable variations in width including steps in trends and large spikes relate to physiogeologic boundaries that the river passes through a large fraction 15 of the river s length classifies as bedrock reach showing that it behaves more like a bedrock river than an alluvial river unlike established trends the channel is wider in bedrock than in alluvium field observations show that aspect ratio width to depth is not constant but fluctuates systematically with width from wide shallow reaches to narrower deeper reaches our observations of bedrock properties suggest that susceptibility to fluvial plucking versus abrasion may control this anomalous channel morphology one end member form with aspect ratio as high as 500 which we term the incision plain is associated with very closely spaced discontinuities 10 cm in otherwise hard rock we propose that the closely spaced discontinuities enable efficient plucking that leads to widening by lateral erosion this morphology locally occurs in other passive margin rivers and may be a fundamental fluvial form that is similar to but the inverse of slot canyons the other end member which we term channel neck is narrower and deeper with complex flow paths through blocky bedrock this form occurs where discontinuity spacing is longer 0 5 m and erosion is abrasion dominated these results imply that changes in channel width do not necessarily reflect variations in uplift rate but instead may result from complex response to bedrock properties

fault gouge dating in the southern appalachians usa illite age analysis iaa the method of comparing radiometric ages of successive size fractions with varying percentages of detrital illite has been successfully applied to several rock types including fault gouge shales and argillaceous limestones iaa results are presented for fi ve fault rocks including four clay gouges and one cataclasite from the exhumed southern appalachian foreland fold thrust belt eastern united states determining detrital versus authigenic illite is now an established procedure utilizing x ray analysis to quantify illite polytypes less established however is how to interpret 40 ar 39 ar ages as a function of diagenetic grade both a total gas age incorporating the recoiled argon fraction after irradiation and a retention age omitting the recoiled fraction are obtained for a sample we relate their respective use to diagenetic grade and specifi cally the crystallite thickness of illite when measured crystallite sizes are equal to or smaller than that calculated from ar recoil we use total gas ages here 5 nm while for crystallites greater than 10 nm we use retention ages the four clay gouge ages are all the same within error and much younger than that of the cataclasite we conclude that a major period of frontal appalachian fault activity occurred during the early permian cisuralian 276 280 ma and that these foreland faults were active simultaneously as part of an internally deforming regional thrust wedge

geocarbsulf a combined model for phanerozoic atmospheric o2 and co2 abstract a model for the combined long term cycles of carbon and sulfur has been constructed which combines all the factors modifying weathering and degassing of the geocarb iii model berner r a kothavala z 2001 geocarb iii a revised model of atmospheric co2 over phanerozoic time am j sci 301 182 204 for co2 with rapid recycling and oxygen dependent carbon and sulfur isotope fractionation of an isotope mass balance model for o2 berner r a 2001 modeling atmospheric o2 over phanerozoic time geochim cosmochim acta 65 685 694 new isotopic data for both carbon and sulfur are used and new feedbacks are created by combining the models sensitivity analysis is done by determining 1 the effect on weathering rates of using rapid recycling rapid recycling treats carbon and sulfur weathering in terms of young rapidly weathering rocks and older more slowly weathering rocks 2 the effect on o2 of using different initial starting conditions 3 the effect on o2 of using different data for carbon isotope fractionation during photosynthesis and alternative values of oceanic 13c for the past 200 million years 4 the effect on sulfur isotope fractionation and on o2 of varying the size of o2 feedback during sedimentary pyrite formation 5 the effect on o2 of varying the dependence of organic matter and pyrite weathering on tectonic uplift plus erosion and the degree of exposure of coastal lands by sea level change 6 the effect on co2 of adding the variability of volcanic rock weathering over time berner r a 2006 inclusion of the weathering of volcanic rocks in the geocarbsulf model am j sci 306 in press results show a similar trend of atmospheric co2 over the phanerozoic to the results of geocarb iii but with some differences during the early paleozoic and for variable volcanic rock weathering lower co2 values during the mesozoic atmospheric oxygen shows a major broad late paleozoic peak with a maximum value of about 30 o2 in the permian a secondary less broad peak centered near the silurian devonian boundary variation between 15 and 20 o2 during the cambrian and ordovician a very sharp drop from 30 to 15 o2 at the permo triassic boundary and a more or less continuous rise in o2 from the late triassic to the present

chemical diagenetic constraints on the timing of cataclasis in deformed sandstone along the pine mountain overthrust eastern kentucky abstract cathodoluminescence imaging reveals that sandstones of the middle pennsylvanian lee formation and breathitt group along the pine mountain overthrust pmo contain inter and intra granular authigenic quartz in proportions that differ markedly between samples of contrasting deformational state fracture surfaces generated during fault movement provided nucleation substrates favorable for the emplacement of substantial amounts of intragranular quartz up to 11 volume percent in the lee formation relatively undeformed sandstones contain cement that is dominantly intergranular whereas sandstones from highly deformed cataclasites along the trace of the pmo contain cement that is dominantly localized within intragranular fractures therefore the chemical diagenetic histories of different samples of breathitt and lee sandstones diverged markedly as a consequence of differing deformational histories and the cementation history thus constitutes a record that is relevant to deciphering the timing of deformation the small quantities of early formed intergranular cement within the cataclasites average 3 7 volume percent show evidence of breakage and accordingly must have largely pre dated the deformation quartz cementation modeling touchstone suggests that emplacement of this pre deformational intergranular cement within these deformed rocks can be bracketed within a period from approximately 280 to 260 ma an interpretation of fault movement that shortly post dates this initial period of quartz cementation is consistent with other estimates for the timing of the alleghanian orogeny because of their protracted period of burial rocks in the vicinity of the pmo remained at temperatures amenable to continued quartz cementation until the middle cenozoic and thus most of the quartz cementation in the cataclasites and also in the surrounding undeformed sandstones post dates movement on the fault

isotopic evaluation of ocean circulation in the late cretaceous north american seaway the role of the north american seaway in creating and maintaining late cretaceous global greenhouse conditions has been unclear an isotopic analysis of marine turtle and fish fossils from western kansas and the mississippi embayment reveals that the inflow of tethyan surface waters to the seaway was limited during the mid and late cretaceous period north america was split by the north south oriented western interior seaway its role in creating and maintaining late cretaceous global greenhouse conditions remains unclear different palaeoceanographic reconstructions portray diverse circulation patterns1 2 3 the southward extent of relatively cool low salinity low 18o surface waters critically distinguishes among these models but past studies of invertebrates could not independently assess water temperature and isotopic compositions here we present oxygen isotopes in biophosphate from coeval marine turtle and fish fossils from western kansas representing the east central seaway and from the mississippi embayment representing the marginal tethys ocean our analyses yield precise seawater isotopic values and geographic temperature differences during the main transition from the coniacian to the early campanian age 87 82 myr and indicate that the seaway oxygen isotope value and salinity were 2 and 3 lower respectively than in the marginal tethys ocean we infer that the influence of northern freshwater probably reached as far south as kansas our revised values imply relatively large temperature differences between the mississippi embayment and central seaway explain the documented regional latitudinal palaeobiogeographic zonation4 5 and support models with relatively little inflow of surface waters from the tethys ocean to the western interior seaway2 3

ocean overturning since the late cretaceous inferences from a new benthic foraminiferal isotope compilation 1 benthic foraminiferal oxygen isotopic d 18 o and carbon isotopic d 13 c trends constructed from compilations of data series from multiple ocean sites provide one of the primary means of reconstructing changes in the ocean interior these records are also widely used as a general climate indicator for comparison with local and more specific marine and terrestrial climate proxy records we present new benthic foraminiferal d 18 o and d 13 c compilations for individual ocean basins that provide a robust estimate of benthic foraminiferal stable isotopic variations to 80ma andtentatively to 110ma first order variations ininterbasinal isotopicgradients delineate transitions from interior ocean heterogeneity during the late cretaceous 65 ma to early paleogene 35 65 ma homogeneity and a return to heterogeneity in the late paleogene early neogene 35 0 ma we propose that these transitions reflect alterations in a first order characteristic of ocean circulation the ability of winds to make water in the deep ocean circulate we document the initiation of large interbasinal d 18 o gradients in the early oligocene and link the variations in interbasinal d 18 o gradients from the middle eocene to oligocene with the increasing influence of wind driven mixing due to the gradual tectonic opening of southern ocean passages and initiation and strengthening of the antarctic circumpolar current the role of wind driven upwelling possibly associated with a tethyan circumequatorial current in controlling late cretaceous interior ocean heterogeneity should be the subject of further research

discovery of a nanodiamond rich layer in the greenland ice sheet we report the discovery in the greenland ice sheet of a discrete layer of free nanodiamonds nds in very high abundances implying most likely either an unprecedented influx of extraterrestrial et material or a cosmic impact event that occurred after the last glacial episode from that layer we extracted n diamonds and hexagonal diamonds lonsdaleite an accepted et impact indicator at abundances of up to about 5 10 6 times background levels in adjacent younger and older ice the nds in the concentrated layer are rounded suggesting they most likely formed during a cosmic impact through some process similar to carbon vapor deposition or high explosive detonation this morphology has not been reported previously in cosmic material but has been observed in terrestrial impact material this is the first highly enriched discrete layer of nds observed in glacial ice anywhere and its presence indicates that ice caps are important archives of et events of varying magnitudes using a preliminary ice chronology based on oxygen isotopes and dust stratigraphy the nd rich layer appears to be coeval with nd abundance peaks reported at numerous north american sites in a sedimentary layer the younger dryas boundary layer ydb dating to 12 9 0 1 ka however more investigation is needed to confirm this association

modeling atmospheric o2 over phanerozoic time a carbon and sulfur isotope mass balance model has been constructed for calculating the variation of atmospheric o2 over phanerozoic time in order to obtain realistic o2 levels rapid sediment recycling and o2 dependent isotope fractionation have been employed by the modelling the dependence of isotope fractionation on o2 is based for carbon on the results of laboratory photosynthesis experiments and for sulfur on the observed relation between oxidation reduction recycling and s isotope fractionation during early diagenetic pyrite formation the range of fractionations used in the modeling agree with measurements of phanerozoic sediments by others results derived from extensive sensitivity analysis suggest that there was a positive excursion of o2 to levels as high as 35 during the permo carboniferous high o2 at this time agrees with independent modeling based on the abundances of organic matter and pyrite in sediments and with the occurrence of giant insects during this period the cause of the excursion is believed to be the rise of vascular land plants and the consequent increased production of o2 by the burial in sediments of lignin rich organic matter that was resistant to biological decomposition

final palaeolithic settlements of the campine region ne belgium in their environmental context optical age constraints abstract the sand sequences exposed at the archaeological sites of arendonk korhaan and lommel maatheide offer a unique means to study the possible relation between human occupation patterns and climatic and environmental changes during the weichselian holocene transition in the campine region ne belgium of particular importance is that at these localities the final palaeolithic and early mesolithic settlement phases are stratigraphically separated optically stimulated luminescence osl dating established a chronology for the evolution of the physical landscape around these sites such a framework is essential when trying to understand settlement dynamics in response to environmental forcing thirty samples in total were dated using quartz sar osl the luminescence ages range from 16 2 1 4 ka to 10 6 0 7 ka they indicate that sand deposition at arendonk and lommel was already going on during the final phase of the late pleniglacial and or the onset of the late glacial at arendonk sediments and soils from the early late glacial until the allerod are missing whereas a single interruption in the aeolian activity during the allerod interstadial is reported for lommel landscape stabilisation during the allerod is also suggested by stratigraphical evidence i e the presence of a bleached horizon both at elevated and low lying flat areas and extensive peat growth in wet depressions the bolling interstadial on the other hand has not been recognised in the lithostratigraphic record this corroborates earlier suggestions that the climatic amelioration during the bolling was not accompanied by a general stabilisation of the land surface in the nw european lowlands the continuation of sand transport and deposition across the late pleniglacial late glacial boundary may explain why human societies did not occupy the campine region until the allerod during this interstadial environmental conditions improved sufficiently to attract final palaeolithic federmessergruppen to settle on higher grounds in the area the climate deteriorated at the onset of the late dryas and as a consequence aeolian activity intensified again at arendonk and lommel with at least 0 5 1 m of sand being deposited in a period of 1 ka this may have caused the federmesser to leave the area at both localities no occupation has been attested for the late dryas period until the early holocene when early mesolithic societies settled in the area this study illustrates how luminescence dating can contribute to an improved understanding of the environmental context around archaeological sites in the campine region

the mysterious onset of the younger dryas abstract the 1300 year long younger dryas cold reversal 12 900 11 600 cal bp is seen most clearly in greenland ice cores contemporaneous changes of climate and environment in more southerly regions were variably expressed the precise timing of the abrupt younger dryas onset is still uncertain it was linked to a sudden increase in 14c manifest as a cliff where 14c dates drop from 11 000 to 10 600 radiocarbon years bp within a century of real time followed by a long plateau changes in ocean and or atmospheric circulation or solar radiation and even a comet impact have been proposed as triggers but the abruptness and severity of yd onset still elude explanation