the prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models the accuracy of the predictions of distributed hydrological models must depend in part on the proper specification of flow pathways this paper examines some of the problems of deriving flow pathways from raster digital terrain data in the context of hydrological predictions using topmodel distributed moisture status is predicted in topmodel on the basis of spatial indices that depend on flow path definition the sensitivity of this index to flow path algorithm and grid size is examined for the case where the surface topography is a good indicator of local hydraulic gradients a strategy for the case where downslope subsurface flow pathways may deviate from those indicated by the surface topography is described with an example application

calibrating the end permian mass extinction the end permian mass extinction was the most severe biodiversity crisis in earth history to better constrain the timing and ultimately the causes of this event we collected a suite of geochronologic isotopic and biostratigraphic data on several well preserved sedimentary sections in south china high precision u pb dating reveals that the extinction peak occurred just before 252 28 0 08 million years ago after a decline of 2 per mil in 13c over 90 000 years and coincided with a 13c excursion of 5 that is estimated to have lasted 20 000 years the extinction interval was less than 200 000 years and synchronous in marine and terrestrial realms associated charcoal rich and soot bearing layers indicate widespread wildfires on land a massive release of thermogenic carbon dioxide and or methane may have caused the catastrophic extinction

climate warming in the latest permian and the permian triassic mass extinction high resolution oxygen isotope records document the timing and magnitude of global warming across the permian triassic p tr boundary oxygen isotope ratios measured on phosphate bound oxygen in conodont apatite from the meishan and shangsi sections south china decrease by 2 in the latest permian translating into low latitude surface water warming of 8 c the oxygen isotope shift coincides with the negative shift in carbon isotope ratios of carbonates suggesting that the addition of isotopically light carbon to the ocean atmosphere system by siberian traps volcanism and related processes resulted in higher greenhouse gas levels and global warming the major temperature rise started immediately before the main extinction phase with maximum and harmful temperatures documented in the latest permian meishan bed 27 the coincidence of climate warming and the main pulse of extinction suggest that global warming was one of the causes of the collapse of the marine and terrestrial ecosystems in addition very warm climate conditions in the early triassic may have played a major role in the delayed recovery in the aftermath of the permian triassic crisis

87sr 86sr stratigraphy from the early triassic of zal iran linking temperature to weathering rates and the tempo of ecosystem recovery recovery from the late permian mass extinction was slowed by continued environmental perturbations during the early triassic rapid fluctuations of the early triassic marine carbonate carbon isotope record indicate instability in the global carbon cycle and recent 18 o apatite studies link elevated temperatures to the prolonged biotic recovery high temperatures potentially caused enhanced continental weathering that was detrimental to marine ecosystems but linking weathering rates to temperature has proven difficult one proxy for weathering is the 87 sr 86 sr of marine carbonate we present here an 87 sr 86 sr record from an upper permian lower triassic succession near zal iran that is coupled to a 13 c carbonate record an increase in the rate of 87 sr 86 sr rise from the dienerian to the smithian may be linked to elevated continental weathering rates caused by warming during the smithian

the end permian mass extinction a rapid volcanic co2 and ch4 climatic catastrophe abstract the end of the permian was a time of crisis that culminated in the earth s greatest mass extinction there is much speculation as to the cause for this catastrophe here we provide a full suite of high resolution and coeval geochemical results trace and rare earth elements carbon oxygen strontium and clumped isotopes reflecting ambient seawater chemistry and water quality parameters leading up to the end permian crisis preserved brachiopod low mg calcite based seawater chemistry supplemented by data from various localities documents a sequence of interrelated primary events such as coeval flows of siberian trap continental flood basalts and emission of carbon dioxide leading to warm and extreme greenhouse conditions with sea surface temperatures sst of 36 c for the late permian although anoxia has been advanced as a cause for the mass extinction most biotic and geochemical evidence suggest that it was briefly relevant during the early phase of the event and only in areas of upwelling but not a general cause instead we suggest that renewed and increased end permian siberian trap volcanic activity about 2000 years prior to the extinction event released massive amounts of carbon dioxide and coupled with thermogenic methane emissions triggered extreme global warming and increased continental weathering eventually these rapidly discharged greenhouse gas emissions less than 1000 years before the event ushered in a global hothouse period leading to extreme tropical ssts of 39 c and higher based on these sea surface temperatures atmospheric co 2 concentrations were about 1400 ppmv and 3000 ppmv for the late and end permian respectively leading up to the mass extinction there was a brief interruption of the global warming trend when sst dropped concurrent with a slight but significant recovery in biodiversity in the western tethys it is possible that emission of volcanic sulfate aerosols resulted in brief cooling just after the onset of intensified warming during the end of the permian after aerosol deposition global warming resumed and the biotic decline proceeded and was accompanied by suboxia in places of the surface ocean which culminated in the greatest mass extinction in earth history

contribution to the seismotectonics of eastern turkey from moderate and small size events an edited version of this paper was published by the american geophysical union agu copyright 2003 agu see also http www agu org pubs crossref 2003 2003gl018258 shtml http atlas geo cornell edu turkey publications orgulu et al 2003 htm

earliest triassic claystone breccias and soil erosion crisis abstract chemostratigraphic methods 13corg for pinpointing the permian triassic boundary in nonmarine rocks of antarctica australia and south africa have drawn attention to unusual claystone breccias at this horizon of the greatest extinction in the history of life on earth these rocks differ from other breccias in having a high proportion of clasts with birefringence microfabrics sepic plasmic fabrics characteristic of soils and can be called sepic pedoliths in the terminology of soil science at many localities earliest triassic sepic pedoliths are thin 5 15 cm beds but some fill shallow paleochannels and pinch out laterally other non marine breccias at the permian triassic boundary are dominated by fragments of coal pedogenic carbonate nodules and deeply weathered volcanic rock fragments earliest triassic sepic pedoliths record an unusually severe and widespread episode of soil erosion associated with forest dieback at the permian triassic boundary comparable sepic pedoliths are found in debris flows after clear cutting of forests in western oregon today studies of these modern deposits show that sepic soil peds do not withstand weathering for more than a few months such clayey clasts are held together mainly by roots and fungi which decay rapidly in soils and streams these modern analogs demonstrate that terminal permian soil erosion was rapid and profound sepic pedoliths are also known at other times of mass extinction such as the triassic jurassic boundary but are not yet known before the devonian advent of trees and forested clayey soils

petrographic and geochemical investigations of the late prehistoric ceramics from sos hoyuk erzurum eastern anatolia abstract ceramics from the late prehistoric periods at sos hoyuk in eastern anatolia located along a thoroughfare that connects the trans caucasus iran and central anatolia were subjected to petrographic and x ray fluorescence analysis in order to characterise the clay groups with a view to determining provenance and production patterns dominated by kura araxes ware the data from the sequence at sos hoyuk were compared with the previous studies from the neighbouring regions to understand commonalities in pottery production the analyses reveal a local production of vessels most probably for household use although sos hoyuk potters shared similarities in the procurement pattern of raw clays and production technique with their neighbours differences can be also recognized

long term cycles of triassic climate change a new δ18o record from conodont apatite jat and isw gratefully acknowledge financial support from the australian research council dp1096252 mr is grateful for financial support from progetto d ateneo 2009 cpda090175 09 and 2012 cpda 121100 and prin 2008 2008bef5z7 005

global coal gap between permian triassic extinction and middle triassic recovery of peat forming plants early triassic coals are unknown and middle triassic coals are rare and thin the early triassic coal gap began with extinction of peat forming plants at the end of the permian ca 250 ma with no coal known anywhere until middle triassic 243 ma permian levels of plant diversity and peat thickness were not recovered until late triassic 230 ma tectonic and climatic explanations for the coal gap fail because deposits of fluctuating sea levels and sedimentary facies and paleosols commonly found in coal bearing sequences are present also in early triassic rocks nor do we favor explanations involving evolutionary advances in the effectiveness of fungal decomposers insects or tetrapod herbivores which became cosmopolitan and much reduced in diversity across the permian triassic boundary instead we favor explanations involving extinction of peat forming plants at the permian triassic boundary followed by a hiatus of some 10 m y until newly evolved peat forming plants developed tolerance to the acidic dysaerobic conditions of wetlands this view is compatible not only with the paleobotanical record of extinction of swamp plants but also with indications of a terminal permian productivity crash from delta sup 13 c sub org and total organic carbon of both nonmarine and shallow marine shales 205 refs 3 figs more 3 tabs less

pliocene palaeoclimates past climates as possible analogues of mid twenty first century climate abstract as a result of summarizing the data over 18 regional sections on the continents and those of deep sea drilling a preliminary chronological scale of global climatic events of the late miocene pliocene has been developed thirty superclimathems are determined which are the phases of mean global temperature varying with an amplitude of not less than 4 5 c and duration of 100 000 300 000 years the warm intervals thermochrons can be considered as palaeoanalogues of the possible future climatic conditions according to the widely suggested drastic warming of the world climates that may be impending due to carbon dioxide increase thus the climate of the warm interval of the pliocene the so called climatic optimum brunssum kamyshburunian 4 3 3 3 m y is taken as the palaeoanalogue of the mid twenty first century climate when doubling of the co2 content of the atmosphere might occur reconstruction of the temperature field of the northern hemisphere for july august and january february has been carried out for that time interval the mean annual temperature of the northern hemisphere at that time seems to have been 3 8 c higher than at present which coincides with calculations of manabe and wetherald based on their general circulation model for doubling the co2 concentration by the year 2050

high resolution clay mineral and major elemental characterization of a permian triassic terrestrial succession in southwestern china diagenetic and paleoclimatic paleoenvironmental significance abstract relatively high resolution clay mineralogical and chemical index of alteration cia analyses were conducted on the terrestrial lubei section in southwestern china to gain a better understanding of the paleoclimatic paleoenvironmental evolution on land during the permian triassic transition p tr transition clay mineral species include illite smectite mixed layers i s illite irregular chlorite expandable mixed layers c e chlorite kaolinite vermiculite hydroxyl interlayered mineral him and corrensite cia values are as high as approaching 100 in the permian and show a gradual and subtle decrease towards the lowermost triassic where a sudden decrease to persistently

landform oriented flow routing algorithm for the dual structure loess terrain based on digital elevation models the loess landform in the loess plateau of china is with typical dual structure namely the upper smooth positive terrain and the lower cliffy negative terrain p n terrain for short obvious differences in their morphological feature geomorphological mechanism and hydrological process could be found in the both areas based on the differences a flow routing algorithm that separately addresses the dual structure terrain would be necessary to encompass this spatial variation in their hydrological behaviour this paper proposes a mixed flow routing algorithm to address aforementioned problems first the loess landform surface is divided into p n terrains based on digital elevation models then specific catchment area is calculated with the new algorithm to simulate the water flows in both positive and negative terrain areas the mixed algorithm consists of the multiple flow routing algorithm multiple flow direction for positive areas and the d8 algorithm for negative areas respectively the approach is validated in two typical geomorphologic areas with low hills and dense gullies in the northern shaanxi loess plateau four indices are used to examine the results which show that the new algorithm is more suitable for loess terrain in simulating the spatial distribution of water accumulation as well as in modeling the flow characteristics of the true surface by considering the morphological structures of the terrain copyright 2013 john wiley sons ltd

coevolution of nonlinear trends in vegetation soils and topography with elevation and slope aspect a case study in the sky islands of southern arizona 1 feedbacks among vegetation dynamics pedogenesis and topographic development affect the critical zone the living filter for earth s hydrologic biogeochemical and rock sediment cycles assessing the importance of such feedbacks which may be particularly pronounced in water limited systems remains a fundamental interdisciplinary challenge the sky islands of southern arizona offer an unusually well defined natural experiment involving such feedbacks because mean annual precipitation varies by a factor of five over distances of approximately 10 km in areas of similar rock type granite and tectonic history here we compile high resolution spatially distributed data for effective energy and mass transfer eemt the energy available to drive bedrock weathering above ground biomass soil thickness hillslope scale topographic relief and drainage density in two such mountain ranges santa catalina scm pinaleno pm strong correlations exist among vegetation soil topography variables which vary nonlinearly with elevation such that warm dry low elevation portions of these ranges are characterized by relatively low above ground biomass thin soils minimal soil organic matter steep slopes and high drainage densities conversely cooler wetter higher elevations have systematically higher biomass thicker organic rich soils gentler slopes and lower drainage densities to test if eco pedo geomorphic feedbacks drive this pattern we developed a landscape evolution model that couples pedogenesis and topographic development over geologic time scales with rates explicitly dependent on vegetation density the model self organizes into states similar to those observed in scm and pm our results highlight the potential importance of eco pedo geomorphic feedbacks mediated by soil thickness in water limited systems

intensified oceanic circulation during early carboniferous cooling events evidence from carbon and nitrogen isotopes abstract the early carboniferous was a climatic transition interval from a mid paleozoic greenhouse world into the late paleozoic ice age it was marked by a long term cooling trend that was punctuated by short glaciations in the tournaisian and visean early to mid early carboniferous here we generated organic carbon and nitrogen isotope profiles for two widely separated lower carboniferous sections arrow canyon range nevada and namur dinant basin belgium in order to assess the global nature and timing of changes in the carbon nitrogen cycles linked to oceanic productivity and redox conditions during this climatic transition interval the carbon and nitrogen isotope profiles of both study sections record major perturbations during the mid tournaisian and visean a mid tournaisian event tice is marked by increases in 13ccarb 13corg and 15nbulk at arrow canyon from 0 6 to 7 0 25 2 to 23 7 and 0 6 to 8 9 respectively and namur dinant from 0 3 to 4 7 27 9 to 22 2 and 5 7 to 5 2 respectively an early visean event vice named herein is marked by increases in 13ccarb 13corg and 15nbulk at arrow canyon from 0 6 to 3 1 28 4 to 23 6 and 1 4 to 9 4 respectively and namur dinant from 2 1 to 4 3 26 7 to 25 0 and 1 4 to 3 3 respectively the positive excursions in all three isotopic records during these events are consistent with increased fractional burial of organic carbon and enhanced denitrification implying intensification of marine productivity and expansion of hypoxia in the global ocean given that each event coincided with lowering of sea surface temperatures and increased glaciation as documented from published conodont 18o and sea level records we hypothesize that global cooling led to intensified oceanic circulation and upwelling on continental margins triggering increased marine productivity and attendant redox changes within the affected upwelling zones our results provide new insights into changes in early carboniferous oceanic conditions in response to the initial stages of cooling leading into the late paleozoic ice age

geomorphological evidence for a changing tectonic regime pasinler basin turkey the pasinler basin in the east anatolian contractional province features a suite of geomorphological zones visible in the field air photographs and landsat and shuttle radar topography mission srtm digital elevation model imagery these zones reflect past and current tectonically influenced processes relicts of the erzurum kars plateau representing mio pliocene volcanism associated with transtensional tectonics have been modified by two stages of drainage development an earlier shallow valley network which was modified following uplift and tilting to form the present system characterized by deep narrow valleys that supply alluvial fan complexes these fans discharge onto the present aggradation dominated basin floor initial normal faulting induced massive slope failures on the basin9s northern margin this extensional phase within the basin was reversed by the late pleistocene with thrust faults modifying and producing landforms and affecting sediment sequences along both its northern and southern margins the shift from a transtensional regime and the associated volcanism to normal faulting in the pliocene to early pleistocene and then to the present regime of compression induced thrusting appears to correspond to a regional tectonic shift resulting from the collision of the eurasian and arabian plates and the subsequent westwards movement of the anatolian microplate

environmental instability prior to end permian mass extinction reflected in biotic and facies changes on shallow carbonate platforms of the nanpanjiang basin south china abstract shallow carbonate platforms exhibit major changes in faunal composition and facies types during the latest permian and earliest triassic although the microbialites that developed following the latest permian mass extinction lpme have attracted wide attention temporal variations in shallow platform facies and faunas prior to the lpme have been less thoroughly studied here we analyze diversity patterns and variation in skeletal composition in three upper permian sections from isolated carbonate platforms of the nanpanjiang basin in addition to the well known transition from fossil rich upper permian limestones to fossil poor permian triassic boundary ptb microbialites these sections exhibit several distinct changes that predate the lpme first foram faunas show a shift from non fusulinid dominated to fusulinid dominated communities in the

controls on valley spacing in landscapes subject to rapid base level fall what controls the architecture of drainage networks is a fundamental question in geomorphology recent work has elucidated the mechanisms of drainage network development in steadily uplifting landscapes but the controls on drainage network morphology in transient landscapes are relatively unknown in this paper we exploit natural experiments in drainage network development in incised plio quaternary alluvial fan surfaces in order to understand and quantify drainage network development in highly transient landscapes i e initially unincised low relief surfaces that experience a pulse of rapid base level drop followed by relative base level stasis parallel drainage networks formed on incised alluvial fan surfaces tend to have a drainage spacing that is approximately proportional to the magnitude of the base level drop numerical experiments suggest that this observed relationship between the magnitude of base level drop and mean drainage spacing is the result of feedbacks among the depth of valley incision mass wasting and nonlinear increases in the rate of colluvial sediment transport with slope gradient on steep valley side slopes that lead to increasingly wide valleys in cases of larger base level drop we identify a threshold magnitude of base level drop above which side slopes lengthen sufficiently to promote increases in contributing area and fluvial incision rates that lead to branching and encourage drainage networks to transition from systems of first order valleys to systems of higher order branching valleys the headward growth of these branching tributaries prevents the development of adjacent ephemeral drainages and promotes a higher mean valley spacing relative to cases in which tributaries do not form model results offer additional insights into the response of initially unincised landscapes to rapid base level drop and provide a preliminary basis for understanding how varying amounts of base level change influence valley network morphology copyright 2015 john wiley sons ltd

simulating permian triassic oceanic anoxia distribution implications for species extinction and recovery the biggest mass extinction in the phanerozoic at the end of the permian has been associ ated with oceanic changes but the exact dynamics are still debated intensifi ed stratifi cation widespread anoxia chemocline excursions and large scale ocean overturn events have all been invoked as contributors to the extinction in this study the effects of possible changes in environmental conditions such as an increase in nutrient input or dust fl uxes into the ocean or an intensifi cation of the biological pump on permian triassic ocean chemistry are inves tigated series of sensitivity experiments were performed with a fully coupled climate carbon cycle model none of the forcings alone generates extensive low oxygen conditions in the deep sea these are only simulated by an intense eutrophication in combination with an enhanced biological pump but still confi ned to the central panthalassic tethys and the eastern boreal oceans our fi ndings support the conclusions from a recent geochemical study of a japanese deep panthalassa section that around the permian triassic boundary the oxygen minimum zone expanded considerably while the deep panthalassa remained ventilated the warming induced increase in low oxygen conditions within the water column aggravated adverse exist ing conditions and likely contributed to the extinction peak upwelling of toxic water was probably regionally confi ned and hence not the main cause for the end permian marine and terrestrial mass extinction widespread deep sea anoxia generated by a strong increase in weathering and the related enhanced nutrient input into the oceans is probably closely linked to the delayed recovery of species in the early triassic

channel changes in badlands stripping of the vegetation and soil from a 13 hectare site in virginia underlain by coastal plain sediments created a rapidly evolving badland topography two types of channels developed 1 sand bed alluvial channels were graded to transport the bed material load supplied from slope erosion with available runoff but they also generally eroded their beds slowly and 2 steeper bedrock floored channels incised rapidly in bedrock channels the erosion rate was proportional to the 4 9ths power of drainage area and the 2 3rds power of gradient these exponents are consistent with a model in which the erosion rate is proportional to the bed shear during high flows due to rapid mass wasting and reduced runoff the alluvial channels became as much as 50 steeper during the winter than the summer with an attendant yearly cycle of winter aggradation and summer entrenchment the gradients their seasonal variability and their downstream hydraulic geometry were consistent with the predictions of total load transport formulas for sand beds and high loads the hydraulic geometry of alluvial channels in the virginia badlands were similar to that on the morrison formation in the western united states

magma generation by slab steepening and breakoff beneath a subduction accretion complex an alternative model for collision related volcanism in eastern anatolia turkey 1 eastern anatolia is regarded as one of the best examples of continental collision represented by a 2 km high plateau it displays shallow and diffuse seismicity indicating that the crust is still being actively deformed perhaps the most striking aspect of eastern anatolia is the volume and compositional variability of collision related volcanic products erupted during the neogene and quaternary time a number of models have been proposed for the genesis of this volcanism in the region however recent geophysical studies have revealed that a mantle lithosphere is almost completely absent beneath a greater portion of the region which makes us question the validity of the previous models in this paper we propose a new model for magma genesis slab steepening and breakoff beneath a large subduction accretion complex this model holds that a northward subducting oceanic lithosphere beneath the eastern anatolia accretionary prism gets steepened and eventually detached from the continental lithosphere of the bitlis poturge massif following the continent accretionary complex collision this brings the asthenospheric mantle in contact with the accretionary complex at shallow depths e g around 50 km resulting in rapid regional uplift and extensive melting which leads to collisional volcanism

lower triassic deep sea carbonate precipitates from south tibet china abstract sea floor carbonate precipitates scps commonly seen in pre cambrian strata were widely developed during the permian triassic mass extinction and the early triassic recovery interval most scps are found in shallow water facies with few scps reported from deep sea settings here we document lower triassic deep sea scps from turbidite deposits exposed at the xiukang section south tibet china the scps only occur within thin bedded silty limestones that are embedded in dark grey shale parallel aligned mud cobbles rounded micritic intraclasts and micro erosional surfaces are commonly seen in these planar laminated limestones that contain abundant radiolarians and thin shelled bivalves indicating deposition in a deep basin via turbidity currents the deep sea scps which are comprised of bladed calcite crystals display a weak vertical 13c variation with the overlying matrix and a uniform element distribution and consequently have a homogenous cathodoluminescence pattern suggesting rapid precipitation in the open ocean followed by a quick burial which led to minimal diagenetic effects on the scps we propose a new hypothesis that rapid carbonate precipitation resulted from mixing driven by the turbidity current that introduced shallow seawater to the deep seawaters with a high alkalinity based on this model the turbidity currents during the early triassic might serve as a potential role in the connection between the oxic surface oceans and the euxinic deep oceans

strontium isotope stratigraphy in the late cretaceous numerical calibration of the sr isotope curve and intercontinental correlation for the campanian the white chalk exposed in quarries at lagerdorf and kronsmoor northwestern germany provides a standard section for the european upper cretaceous the sr 87 sr 86 values of nannofossil chalk and belemnite calcite increase upward through 330 m of section from less than or equal to 0 70746 in the upper santonian to greater than or equal to 0 70777 in the lower maastrichtian the data define three linear trends separated by major points of inflection at stratigraphic heights in the section of 162 m 75 5 ma in the upper campanian galerites vulgaris zone and at 6 m 82 9 ma just above the base of the campanian in the inoceramus lingua goniateuthis quadrata zone the temporal rate of change of sr 87 sr 86 was constant through each of the linear segments of our isotope curve when viewed at the resolution of our average sampling interval 0 15 m y fine structure if rear may record brief 100 kyr excursions of srsr sr 87 sr 86 from values expected from the overall trends in lagerdorf the boundary between the santonian and campanian stages taken here as the level of first occurrence of the belemnite gonioteuthis granulataquadrata has an sr 87 sr 86 of 0 707473 5 this is within error of the values of 0 707457 16 for this boundary in the u s western interior base of the scaphites leei iii zone and 0 707479 9 for this boundary in the english chalk top of the marsupites testudinarius zone in kronsmoor the boundary between the campanian and maastrichtian stages taken here as the level of first occurrence of the belemnite belemnella lanceolata has an sr 87 sr 86 of 0 707723 4 this is within error of the values of 0 707725 20 for this boundary in the u s western interior base of the baculites eliasi zone and 0 707728 5 for this boundary in the english chalk defined as in germany

the timing and extent of the eruption of the siberian traps large igneous province implications for the end permian environmental crisis we present new high precision 40ar 39ar ages on feldspar and biotite separates to establish the age duration and extent of the larger siberian traps volcanic province samples include basalts and gabbros from noril sk the lower tunguska area on the siberian craton the taimyr peninsula the kuznetsk basin vorkuta in the polar urals and from chelyabinsk in the southern urals most of the ages except for those from chelyabinsk are indistinguishable from those found at noril sk cessation of activity at noril sk is constrained by a 40ar 39ar age of 250 3 1 1 ma for the uppermost kumginsky suite the new 40ar 39ar data confirm that the bulk of siberian volcanism occurred at 250 ma during a period of less than 2 ma extending over an area of up to 5 million km2 the resolution of the data allows us to confidently conclude that the main stage of volcanism either immediately predates or is synchronous with the end permian mass extinction further strengthening an association between volcanism and the end permian crisis a sanidine age of 249 25 0 14 ma from bed 28 tuff at the global section and stratotype at meishan china allows us to bracket the p tr boundary to 0 58 0 21 myr and enables a direct comparison between the 40ar 39ar age of the traps and the permo triassic boundary section younger ages 243 ma obtained for basalts from chelyabinsk indicate that volcanism in at least the southern part of the province continued into the triassic

active faulting and natural hazards in armenia eastern turkey and northwestern iran active fault zones of armenia se turkey and nw iran present a diverse set of interrelated natural hazards three regional case studies in this cross border zone are examined to show how earthquakes interact with other hazards to increase the risk of natural disaster in northern armenia a combination of several natural and man made phenomena earthquakes landslides and unstable dams with toxic wastes along the pambak sevan sunik fault pssf zone lowers from 0 4 to 0 2 0 3g the maximum permissible level mpl of seismic hazard that may induce disastrous destruction and loss of life in the adjacent vanadzor depression in the ararat depression a large active fault bounded pull apart basin at the junction of borders of armenia turkey iran and azerbaijan an earthquake in 1840 was accompanied by an eruption of ararat volcano lahars landslides floods soil subsidence and liquefaction the case study demonstrates that natural hazards that are secondary with respect to earthquakes may considerably increase the damage and the casualties and increase the risk associated with the seismic impact the north tabriz gailatu fault system poses a high seismic hazard to the border areas of nw iran eastern turkey nakhichevan azerbaijan and southern armenia right lateral strike slip motions along the north tabriz fault have given rise to strong earthquakes which threaten the city of tabriz with its population of 1 2 million the examples illustrate how the concentration of natural hazards in active fault zones increases the risk associated with strong earthquakes in armenia eastern turkey and nw iran this generally occurs across the junctions of international borders hence the transboundary character of active faults requires transboundary cooperation in the study and mitigation of the natural risk

palaeotethys seawater temperature rise and an intensified hydrological cycle following the end permian mass extinction abstract the end permian mass extinction has been associated with severe global warming main stage volcanism of the siberian traps occurred at or near the extinction interval and has been proposed as a likely greenhouse catalyst in this study a high resolution 18o record is established using diagenetically resistant apatite of conodonts and low mg calcite of brachiopods from stratigraphically well constrained permian triassic p tr boundary successions in northwestern iran a new evaluation is made for previously published conodont 18o values from south china and revised palaeotemperatures are presented together with new data from wuchiapingian to griesbachian sections in iran 18o data from p tr sections in iran document tropical sea surface temperatures sst of 27 33 c during the changhsingian with a negative shift in 18o starting at the extinction horizon translating into a warming of ssts to over 35 c the results are consistent with re calculated ssts of the south chinese sections warming was associated with an enhanced hydrological cycle involving increased tropical precipitation and monsoonal activity in the tethys sea global warming intensification of the hydrological cycle and associated processes vertical water column stratification eutrophication and subsequent local anoxia may all have facilitated an extinction event

recovery tempo and pattern of marine ecosystems after the end permian mass extinction high resolution sampling of more than 10 000 microfossils from seven late permian middle triassic paleoequatorial sections in south china refutes claims for a 5 m y recovery delay after the end permian mass extinction we show that level bottom seafloor diversity began to recover in the early smithian little more than 1 m y after the mass extinction while recovery of reef building metazoans began 4 m y later in the anisian a further mass extinction in the late smithian identified in the pelagic fossil record is weakly manifest as a temporary pause in diversification among benthic communities in the early triassic of south china the offshore diversity increase began before then in shallower settings the recovery from the end permian mass extinction in south china was therefore significantly more rapid and environmentally more complex than hitherto known

coupled δ44 40ca δ88 86sr and 87sr 86sr geochemistry across the end permian mass extinction event abstract we report high resolution high precision 44 40ca 88 86sr and 87sr 86sr records spanning the permian triassic boundary ptb from the meishan and dajiang carbonate successions in south china the goal of the study was to understand the behavior of ca and sr isotopes during a time period in earth history characterized by severe biological and environmental perturbations including a major mass extinction flood basalt volcanism ocean acidification and sea level fluctuations dajiang displays negative 44 40ca and 88 86sr excursions and invariant 87sr 86sr ratios in the

late cenozoic stress evolution along the karasu valley se turkey abstract this study defines the mio pliocene to present day stress regime acting at the northeastern corner of the eastern mediterranean region along the karasu valley i e the amanos range taking in the antakya osmaniye and kahramanmaras provinces the inversion slip vectors measured on fault planes and chronologies between striations indicate that the stress regime varied from transpressional initially to transtensional having consistent nw and ne trending hmax 1 and hmin 3 axes respectively there are significantly different mean stress ratio rm values however the older mean stress state is characterized by n151 11 e trending 1 and n59 12 e trending 3 axes and by a mean arithmetic rm value of 0 76 indicating that the regional stress regime is transpressional the younger stress regime is characterized by n154 8 e trending 1 and n243 8 e trending 3 axes and by a mean arithmetic rm value of 0 17 indicating a transtensional character for this regional stress regime the low r values of the stress deviators related to the recent stress state reflect normal component slips the earthquake focal mechanism inversions confirm that the younger stress regime continues into the recent the inversion identifies a transtensional stress regime representing strike slip and an extensional stress state with a consistent ne trending hmin 3 axis these stress states are characterized by n66 e and n249 e trending 3 axes respectively both significant regional stress regimes induce left lateral displacement along the southern part of the east anatolian fault eaf or amanos fault the temporal change probably in quaternary time within the regional stress regime from transpression to transtension resulted from the coeval influences of subduction processes in the west southwest i e along the cyprus arc continental collision in the east and westward escape of the anatolian block

how long is a hillslope hillslope length is a fundamental attribute of landscapes intrinsically linked to drainage density landslide hazard biogeochemical cycling and hillslope sediment transport existing methods to estimate catchment average hillslope lengths include inversion of drainage density or identification of a break in slope area scaling where the hillslope domain transitions into the fluvial domain here we implement a technique which models flow from point sources on hilltops across pixels in a digital elevation model dem based on flow directions calculated using pixel aspect until reaching the channel network defined using recently developed channel extraction algorithms through comparisons between these measurement techniques we show that estimating hillslope length from plots of topographic slope versus drainage area or by inverting measures of drainage density systematically underestimates hillslope length in addition hillslope lengths estimated by slope area scaling breaks show large variations between catchments of similar morphology and area we then use hillslope length relief structure of landscapes to explore nature of sediment flux operating on a landscape distinct topographic forms are predicted for end member sediment flux laws which constrain sediment transport on hillslopes as being linearly or nonlinearly dependent on hillslope gradient because our method extracts hillslope profiles originating from every ridgetop pixel in a dem we show that the resulting population of hillslope length relief measurements can be used to differentiate between linear and nonlinear sediment transport laws in soil mantled landscapes we find that across a broad range of sites across the continental united states topography is consistent with a sediment flux law in which transport is nonlinearly proportional to topographic gradient

large perturbations of the carbon cycle during recovery from the end permian extinction high resolution carbon isotope measurements of multiple stratigraphic sections in south china demonstrate that the pronounced carbon isotopic excursion at the permian triassic boundary was not an isolated event but the first in a series of large fluctuations that continued throughout the early triassic before ending abruptly early in the middle triassic the unusual behavior of the carbon cycle coincides with the delayed recovery from end permian extinction recorded by fossils suggesting a direct relationship between earth system function and biological rediversification in the aftermath of earth s most devastating mass extinction

fluvial stratigraphy and palaeoenvironments in the pasinler basin eastern turkey valley floor sediments from the pasinler basin eastern turkey provide evidence for pleistocene and holocene floodplain conditions three terrace surfaces are present evidence for tectonic processes active during the late neogene is widespread within the basin but tectonic processes do not appear to have substantially influenced the details of the holocene palaeoenvironmental record significant changes in hydrology are recorded with more stable floodplain conditions occurring at around 9000 5500 and 4000 cal yr bp incision occurred sometime after approximately 4000 bp probably as a response to dual climatic and human controls comparisons with key sites in the anatolian region and beyond suggest these changes are part of a regional climatic pattern perhaps influenced by changes in the east african monsoon differences in the details of the records across the region reflect the characteristics of the local environment which increasingly in the latter holocene includes human activity

altered river morphology in south africa related to the permian triassic extinction the permian triassic transition in the karoo basin of south africa was characterized by a rapid and apparently basin wide change from meandering to braided river systems as evidenced by preserved sedimentary facies this radical changeover in river morphology is consistent with geomorphic consequences stemming from a rapid and major die off of rooted plant life in the basin evidence from correlative nonmarine strata elsewhere in the world containing fluvial permian triassic boundary sections suggests that a catastrophic terrestrial die off of vegetation was a global event producing a marked increase in sediment yield as well as contributing to the global 13 c excursion across the permian triassic boundary

permian ice volume and palaeoclimate history oxygen isotope proxies revisited abstract a high resolution oxygen isotope record based on 356 measurements of conodont apatite from several low latitudinal sections in south china usa and iran was composed in order to unravel permian palaeotemperature and ice volume history the conodont apatite 18 o record is compared to published brachiopod calcite 18 o records brachiopods and conodonts from different palaeocontinents show significantly different 18 o values suggesting differences in local climatic conditions e g evaporation precipitation ratio as a consequence secular changes in palaeotemperature and oxygen isotope composition of permian sea water cannot be reconstructed from records combined from different areas but have to be based on records from a specific area oxygen isotope analyses of different conodont taxa suggest that streptognathodus and hindeodus lived in near surface seawater and recorded surface water temperature whereas the habitat of gondolellid genera was variable depending on sea level with both near surface and deeper waters as potential life habitat the oxygen isotope record measured on conodonts from south china exhibits relative high values between 22 and 23 vsmow during the glaciated early permian translating into warm seawater temperature between 26 and 30 c assuming that the late palaeozoic ice volumes were comparable to the pleistocene glacial maxima in contrast to the earlier view that the late palaeozoic ice age lpia terminated in the late sakmarian the south china conodont apatite oxygen isotope record suggests waning of the ice sheets in the kungurian ice melting is indicated by a pronounced decrease in 18 o of 2 vsmow which is interpreted as reflecting the combined effect of climatic warming and glacial ice melting significant temperature fluctuations 4 c warming succeeded by 6 to 8 c cooling are observed during the guadalupian lopingian transition interpreted as combined climate changes induced by emeishan volcanism and changes in habitat depth of gondolellid conodonts oxygen isotope values increase to 22 vsmow in the changhsingian which suggests climate cooling and clarkina moving to deeper waters because of the changhsingian sea level rise across the permian triassic boundary 18 o values decrease from 22 to 19 vsmow parallel to the significant negative carbon isotope excursion and the eruption of the siberian traps the latter is pointing to a cause effect relationship as a consequence of the massive release of volcanic greenhouse gases derived from the siberian volcanism and related processes

87sr 86sr record of permian seawater abstract a population of 169 permian articulate brachiopod shells was analysed for their 87 sr 86 sr ratios 51 of these characterised as well preserved and stratigraphically well defined are utilized for delineation of the permian seawater strontium isotope trend the 87 sr 86 sr curve shows values of about 0 7080 in the lowermost permian asselian followed by a gradual decline to 0 70685 in the capitanian and a minor rise in the dzhulfian and lower dorashamian to values of 0 70715 just below the permian triassic boundary the early permian decrease in the strontium isotope curve that commences in the early sakmarian is coincident with the advancing deglaciation of the gondwana and with the increased aridity in large parts of the pangaea these factors may have led to a reduced continental weathering of rb rich silicate rocks and thus to the decline in seawater 87 sr 86 sr starting with the artinskian the opening of the neotethys and the associated widespread basaltic volcanism supplied low radiogenic strontium to seawater from an enhanced hydrothermal flux in the capitanian basaltic volcanism in the entire palaeotethys ceased and this may have been the reason for a slightly more radiogenic seawater isotopic composition during the lopingian higher input of riverine sr due to expansion of humid areas may have been a contributory factor

the relationship between drainage density erosion rate and hilltop curvature implications for sediment transport processes drainage density is a fundamental landscape metric describing the extent of the fluvial network we compare the relationship between drainage density dd and erosion rate e using the channel hillslope integrated landscape development child numerical model we find that varying the channel slope exponent n in detachment limited fluvial incision models controls the relationship between dd and e with n 1 resulting in increasing dd with e if all other parameters are held constant this result is consistent when modeling both linear and nonlinear hillslope sediment flux we also test the relationship between dd and e in five soil mantled landscapes throughout the usa feather river ca san gabriel mountains ca boulder creek co guadalupe mountains nm and bitterroot national forest id for two of these field sites we compare dd to cosmogenic radionuclide crn derived erosion rates and for each site we use mean hilltop curvature as a proxy for erosion rate where crn derived erosion rates are not available we find that there is a significant positive relationship between dd e and hilltop curvature across every site with the exception of the san gabriel mountains ca this relationship is consistent with an n exponent greater than 1 suggesting that at higher erosion rates the transition between advective and diffusive processes occurs at smaller contributing areas in soil mantled landscapes

carbon sulfur oxygen and strontium isotope records organic geochemistry and biostratigraphy across the permian triassic boundary in abadeh iran pelagic deposits at abadeh represent a complete biostratigraphic record across the permian triassic boundary ptb the presumed water depth during deposition of these sediments was between 60 and 90 m similar to other permian triassic boundary sections the succession at abadeh is characterised by a negative carbon isotope shift of approximately 4 the values start to decrease in the lower c changxingensis c deflecta s l zone reach 0 12 v pdb in the uppermost permian just below the ptb remain low to the early i isarcica zone 0 32 and increase subsequently in the upper i isarcica zone for the time interval of the ptb negative carbon isotope excursion between the c iranica and the i isarcica zones no correlation exists between the 13ccarb and the 18ocarb the above observations argue against the conclusion of heydari et al 2001 that the carbon isotope event at the p t transition is an alteration artefact and not a global signal the decrease in 13ccarb is accompanied by a 5 and potentially up to 10 increase in 34ssss together these features are thought to reflect a complex global event notably the development of widespread anoxic oceans with anoxic bottom layers rising onto the shelves for the carbon isotope drop other factors such as the collapse of ocean primary productivity may also have played a role the 87sr 86sr ratios of dzhulfian seawater show only a minor increase from 0 70705 to 0 70710 reaching 0 70720 in the dorashamian the increase becomes steeper in the early triassic reaching 0 70754 in the n dieneri zone the rise of the strontium isotope values is thought to be related to enhanced continental weathering under humid climatic conditions in the uppermost permian c meishanensis h praeparvus zone and the lack of a dense land vegetation in the early triassic prior to the spathian upper olenekian

geochemical evidence from bio apatite for multiple oceanic anoxic events during permian triassic transition and the link with end permian extinction and recovery abstract a detailed 20 myr redox history of permian to triassic oceans changhsingian to carnian stages has been constructed using ce anomaly ce and th u ratios from conodont albid crown apatite material the results show that the well established phenomenon of intense ocean anoxia coincident with the end permian mass extinction is faithfully recorded in conodont ce and th u data extending this conodont redox record shows that end permian anoxia persisted possibly into the earliest dienerian stage and that two intense oceanic anoxic events also occurred later in the early triassic earliest smithian earliest spathian and middle spathian followed by a weaker manifestation of anoxia in the anisian stage seen in ce data marine benthic radiation following the end permian mass extinction began after the smithian earliest spathian anoxic event suggesting a suppression of evolution prior to this due to these inimical conditions the failure of the middle spathian anoxic event to retard the evolutionary rebound implies shallow shelf seas remained well ventilated at this time even if the oceans did not other attributes of the early triassic record also closely coincide with redox fluctuations phases of anoxia intensification saw the proliferation of microbial carbonates and major negative carbon isotope swings that can be attributed to chemocline shallowing causing alkalinity pulses and enrichment in light remineralised carbon and or indicate a trigger meachnaims related to increased fluxes of light c from siberian volcanic sources

methodology for estimating the topographic factor ls of rusle3d and usped using gis abstract in the rusle3d revised universal soil loss equation 3d and usped unit stream power based erosion deposition models the effects of topography on soil loss are represented by the combined factor ls where l is the slope length factor and s the slope gradient factor the problems with measuring slope gradient and length over large areas are i they are not always estimated correctly and ii different ways are used for their calculation gis geographical information systems software has several algorithms for estimating topographic parameters included in the equations of ls the objective of this research was developing a methodology for ls calculation using gis in order to define the most accurate algorithm for each parameter for the estimation of s and upslope contribution area l the zevenbergen and thorne algorithm and the deterministic infinity algorithm respectively were selected

massive volcanism at the permian triassic boundary and its impact on the isotopic composition of the ocean and atmosphere abstract bulk carbonate and conodonts from three permian triassic p t boundary sections at guryul ravine kashmir abadeh central iran and pufels bula bulla italy were investigated for 13 c and 18 o carbon isotope data highlight environmental changes across the p t boundary and show the following features 1 a gradual decrease of 4 to more than 7 starting in the late permian changhsingian c bachmanni zone with two superimposed transient positive excursions in the c meishanensis h praeparvus and the m ultima s mostleri zones 2 two 13 c minima the first at the p t boundary and a higher occasionally double minimum in the lower i isarcica zone it is unlikely that the short lived phenomena such as a breakdown in biological productivity due to catastrophic mass extinction a sudden release of oceanic methane hydrates or meteorite impact s could have been the main control on the latest permian carbon isotope curve because of its prolonged 0 5 ma duration gradual decrease and the existence of a 1 positive shift at the main extinction horizon the p t boundary 13 c trend matches in time and magnitude the eruption of the siberian traps and other contemporaneous volcanism suggesting that volcanogenic effects such as outgassed co 2 from volcanism and even more thermal metamorphism of organic rich sediments as the likely cause of the negative trend

synsedimentary to early diagenetic rejuvenation of barite sulfides ore deposits example of the triassic intrakarstic mineralization in the lodeve basin france the exhumed lodeve basin herault france provides a rich suite of outcrops showing diagenetic ba pb fe cu fronts trapped in karst system in cambrian dolomites during the triassic post rift exhumation of the basin the sedimentological analysis on 10 sites in the basin reveals that barites sulfides fronts formed during humid arid climate fluctuations and the emplacement of a shallow lake environment the fabric of ore deposits the microthermometry of fluid inclusions entrapped within barites and the strontium sulfur isotopic compositions of barite sulfides associations indicate two distinct groups of mineralizations type i and type ii which are contemporaneous but resulting from different processes the synsedimentary mineralization of the type i the presence of only primary single phase liquid fluid inclusions within barite crystals and the gradual increase of 34s for both barites and chalcopyrites with depth from 7 to 18 9 v cdt suggest ore precipitation close to the vadose zone under bacterial sulfate reduction bsr in a confined sulfate rich playa lake aquifer the similar 87sr 86s ratios between barites and the overlying triassic evaporites indicate that the barium and strontium derived directly from the overlying sulfate rich lake for the type ii the high homogenization temperature of fluid inclusions entrapped within barite modal th between 60 and 80 c and the association with hydrocarbon markers confirm the participation of deeper basinal brines in addition to downward percolating sulfates derived from the lake environment the high positive values of 34s for both barites and sulfides are typical of a precipitation linked to the combined action between anaerobic oxidation of methane and sulfate reduction aom sr at the sulfate methane transition zone smtz during hydrocarbon migration similar 87sr 86sr ratios between middle triassic barites and previous late permian barites confirm that the source of metals precipitated at the smtz originated from the dissolution of anterior ore deposits located in the sulfate depleted zone this study links very shallow metallogenesis processes to reworking of mvt ore deposits by the action of sulfate reducing bacteria around hydrocarbon seeps in a karstic environment

carbonate thermoluminescence and its implication for marine productivity change during the permian triassic transition abstract the permian triassic p tr crisis was the largest mass extinction of the phanerozoic and eliminated over 90 of marine species however the nature of marine productivity changes during the crisis is a matter of on going debate here thermoluminescence tl measurements from 144 bulk carbonate samples from meishan south china show two levels of variation in tl peak intensities at 270 c the first order variation is characterized by a rapid nearly three fold increase a secondary variation is interpreted to record periodic fluctuations on a milankovitch scale 20 kyr rhythm the periodic variations of tl are negatively correlated with mn concentrations suggesting primary productivity is a key factor controlling the tl peak intensity by photo reduction of particulate mn in the presence of organic matter therefore the periodic fluctuations of tl were likely controlled by primary productivity changes on orbital timescales a significant rise of tl peak intensities across the p tr boundary represents the rapid increase of dissolved mn associated with enhanced marine productivity and or oceanic anoxia

geochemistry and secular trends in the middle late permian karst bauxite deposits northwestern iran abstract this study focuses on the middle late permian bauxite deposits found within karstic depressions and sinkholes of carbonates of the ruteh and nessen formations northwestern iran data concerning five karst bauxite deposits each related to a different stratigraphic position within the bedrock were selected to address the chemical distribution and inter elemental relationships especially for critical elements factors that control bauxite formation and the parental affinity the analyzed samples mainly clayey bauxite and bauxitic clay are characterized by large compositional fluctuations involving both major and trace elements the major element composition is dominated by sio2 tio2 al2o3 and fe2o3 among the critical elements compositional fluctuations induce the occurrence of outliers for co nb ta lree and hree similar to other trace elements such as ba sr cr u and zr elemental mobility indicates that most of elements are generally depleted among the critical elements co is enriched only in several samples of the older deposits and ree are enriched in some samples of the younger deposits factor analysis suggests that due to the observed al ga covariance fairly acidic conditions were never attained during bauxitization and that detrital resistant minerals concentrated during a bauxitization stage promoting al ti accumulation furthermore the u co variance with low soluble elements nb ta and th suggests that u was mostly conservative during the formation of deposits cobalt co varies with cr and these elements accumulated during later bauxitization stages when the massive leaching of silica occurred the cia ciw and pia paleo weathering proxies indicate an upward weathering increase which suggests a trend toward more extreme weathering conditions in a wetter and warmer climate according to the permian global warming this is consistent with an upward increasing ba sr ratio and the inspection of the a cn k plot where the younger deposits fall close to the a k edge involving a clayey precursor requires a rainfall increase interestingly the upward trend toward a warmer and wetter climate was also coupled with paleo redox conditions promoting cerium oxidation as depicted by the ce ce values finally the eu anomaly and the sm nd ratio indicate that the studied bauxite deposits were mainly derived from a mafic protolith that formed in the middle late permian as a consequence of the volcanism that affected the entire iranian platform a cluster of karst bauxites however has eu eu values lower than the average standard deviation range of the mafic rocks suggesting a possible contribution of a more differentiated and less mafic protolith similarly the u th ratio at large supports the hypothesis of a mafic protolith for the middle late permian bauxite deposits although some samples show the u th values well above the average standard deviation range of the mafic rocks likely indicating that processes promoting the accumulation of resistant minerals with high u th ratios cannot be excluded this means that in this case the u th ratio does not necessarily reflect the protolith of karst bauxites and that more in general this proxy needs to be carefully interpreted when used to assess the parental affinity of residual rocks

conditions favouring catastrophic landslides on tenerife canary islands catastrophic failures of volcano flanks represent one of the most hazardous geological phenomena these immense mass movements originate either by increasing the destabilizing forces driving forces or by reducing the strength of the materials involved or both the study of large volcanic landslides on tenerife suggests that the presence of weak residual soils palaeosols in combination with the pre existence of deep narrow canyons created by fluvial erosion have played a fundamental role in the initiation of large scale sector collapses of the volcanic edifice regardless of the triggering mechanism considered residual soils strongly reduce the material strength during undrained loading while pre existing canyons control the lateral limits of the landslide the existence of a wet climate in some sectors of the island favours these circumstances

relationships between volcanic patterns and neotectonics in eastern anatolia from analysis of satellite images and dem the late neogene to quaternary volcanism in eastern anatolia is related to the arabia eurasia convergence but a clear deformation pattern has not yet been established in this region we have used the distribution and shape of volcanoes and fault geometry as indicators of the tectonic regime volcanic edifices and related faults were analyzed in vertical view using sar ers spot images and a digital elevation model dem in several places adjacent volcanoes that form linear clusters or elongated volcanoes are clearly rooted on vertical tension fractures these are compatible with horizontal 3 striking 90 n associated with 1 horizontal strike slip regime or vertical extensional regime we mapped the recent faults that are directly associated to volcanoes volcanic vents are related to tail crack horsetail or releasing bend structures in this work it has been possible to define the ese striking 270 km long tutak hamur caldiran fault that forms a releasing bend testifying to right lateral motion extension is well documented for few places but no recent fold has been observed since 8 ma the tectonic system is principally strike slip most of the tension fractures being 2 to 10 km in length so we infer that they affect only part of the crust most strike slip fault zones are of several tens to a few hundred kilometers long and thus not of lithospheric scale therefore the channels used by the magma to reach the surface are crustal structures

recent topographic evolution and erosion of the deglaciated washington cascades inferred from a stochastic landscape evolution model in this study we model postglacial surface processes and examine the evolution of the topography and denudation rates within the deglaciated washington cascades to understand the controls on and time scales of landscape response to changes in the surface process regime after deglaciation the postglacial adjustment of this landscape is modeled using a geomorphic transport law based numerical model that includes processes of river incision hillslope diffusion and stochastic landslides the surface lowering due to landslides is parameterized using a physically based slope stability model coupled to a stochastic model of the generation of landslides the model parameters of river incision and stochastic landslides are calibrated based on the rates and distribution of thousand year time scale denudation rates measured from cosmogenic 10be isotopes the probability distributions of those model parameters calculated based on a bayesian inversion scheme show comparable ranges from previous studies in similar rock types and climatic conditions the magnitude of landslide denudation rates is determined by failure density similar to landslide frequency whereas precipitation and slopes affect the spatial variation in landslide denudation rates simulation results show that postglacial denudation rates decay over time and take longer than 100 kyr to reach time invariant rates over time the landslides in the model consume the steep slopes characteristic of deglaciated landscapes this response time scale is on the order of or longer than glacial interglacial cycles suggesting that frequent climatic perturbations during the quaternary may produce a significant and prolonged impact on denudation and topography

inverting topography for landscape evolution model process representation 3 determining parameter ranges for select mature geomorphic transport laws and connecting changes in fluvial erodibility to changes in climate

controls on the spacing of first order valleys 1 many landscapes are composed of ridges and valleys that are uniformly spaced even where valley locations are not controlled by bedrock structure models of long term landscape evolution have reproduced this phenomenon yet the process by which uniformly spaced valleys develop is not well understood and there is no quantitative framework for predicting valley spacing here we use a numerical landscape evolution model to investigate the development of uniform valley spacing we find that evenly spaced valleys arise from a competition between adjacent drainage basins for drainage area a proxy for water flux and that the spacing becomes more uniform as the landscape approaches a topographic equilibrium valley spacing is most sensitive to the relative rates of advective erosion processes such as stream incision and diffusion like mass transport such as soil creep and less sensitive to the magnitude of a threshold that limits the spatial extent of stream incision analysis of a large number of numerical solutions reveals that valley spacing scales with a ratio of characteristic diffusion and advection timescales that is analogous to a peclet number we use this result to derive expressions for equilibrium valley spacing and drainage basin relief as a function of the rates of advective and diffusive processes and the spatial extent of the landscape the observed scaling relationships also provide insight into the cause of transitions from rill like drainage networks to branching networks the spatial scale of first order drainage basins the contributing area at which hillslopes transition into valleys and the narrow range of width to length ratios of first order basins

fluvial and slope wash erosion of soil mantled landscapes detachment or transport limited many numerical landform evolution models assume that soil erosion by flowing water is either purely detachment limited i e erosion rate is related to the shear stress power or velocity of the flow or purely transport limited i e erosion deposition rate is related to the divergence of shear stress power or velocity this paper reviews available data on the relative importance of detachment limited versus transport limited erosion by flowing water on soil mantled hillslopes and low order valleys field measurements indicate that fluvial and slope wash modification of soil mantled landscapes is best represented by a combination of transport limited and detachment limited conditions with the relative importance of each approximately equal to the ratio of sand and rock fragments to silt and clay in the eroding soil available data also indicate that detachment entrainment thresholds are highly variable in space and time in many landscapes with local threshold values dependent on vegetation cover rock fragment armoring surface roughness soil texture and cohesion this heterogeneity is significant for determining the form of the fluvial slope wash erosion or transport law because spatial and or temporal variations in detachment entrainment thresholds can effectively increase the nonlinearity of the relationship between sediment transport and stream power results from landform evolution modeling also suggest that aside from the presence of distributary channel networks and autogenic cut and fill cycles in non steady state transport limited landscapes it is difficult to infer the relative importance of transport limited versus detachment limited conditions using topography alone copyright 2011 john wiley sons ltd

sr and nd isotopes at the prmian triassic boundary a record of climate change abstract we present a detailed curve of seawater 87sr 86sr for the middle permian to triassic based on analyses of conodonts from overlapping sections in the u s a pakistan correlated using conodont biostratigraphy the isotope ratio decreased in the middle permian at an average rate of 0 000062 ma 1 reached a minimum in the capitanian 257 258 ma and increased in the late permian at an average rate of 0 000097 ma 1 the late permian rate of increase was roughly two and a half times greater than the average increase over the past 40 ma and approximately equal to the highest cenozoic rates which occurred over much shorter time intervals modeling results suggest that decreasing middle permian 87sr 86sr ratios were driven by changes in the riverine sr flux to the oceans while increasing ratios in the late permian triassic are attributed to both increased riverine 87sr 86sr and flux the reduced middle permian riverine flux coincides with extreme continental aridity associated with the formation of pangea and recorded by massive evaporite deposits in addition mountains in the equatorial region of pangea may have created a rain shadow thereby minimizing precipitation in regions that currently contribute the bulk of chemical weathering products to the ocean increasing riverine 87sr 86sr in the late permian is suggested by the observation that 143nd 144nd values decrease at the same time however the source of radiogenic sr is not known frequently cited mechanisms for increasing 87sr 86sr in runoff such as glaciations and continent to continent collisions coincide instead with decreasing seawater 87sr 86sr in the middle permian one possible source may have been deep erosion into older orogens associated with a dramatic increase in chemical weathering in the late permian the cause of enhanced weathering appears to have been increased levels of atmospheric co2 with associated global warming and increased humidity proposed sources of co2 include dissociation of gas hydrates and oxidation of organic matter during extreme sea level regression as well as volcanic emissions from siberian traps eruptions continental floral and faunal distributions are consistent with this interpretation as are oceanic 13c patterns and variations in shallow water sediment lithologies

the end permian regression in south china and its implication on mass extinction abstract records of more than 20 permian triassic boundary ptb sections from south china show that widespread end permian regression took place in whole south china timing of the low ebb of this regression was pinpointed to the clarkina meishanensis and hindeodus changxingensis zones biostratigraphic and paleogeographic studies at conodont zonation level reveal that the yangtze carbonate platform and isolated small carbonate platforms in the hunan guizhou guangxi hgg basin experienced sedimentary hiatus during these two zones which lasted about 50 100 kya meanwhile the basinal areas namely the northern marginal basin of yangtze platform and the hunan guizhou guangxi basin have continuous conodont zonation with silicious and ashbed deposits the basinal areas show two negative 13c shifts during the ptb interval from clarkina yini zone to isarcicella isarcica zone while on the platforms there is usually only one negative shift because the early shift at c meishanensis zone was lost during hiatus the end permian regression and successive rapid transgression taking place at the ptb casted important effects to the pattern and process of the ptb mass extinction the depositional hiatus hitherto underestimated will necessitate reassessment of some interpretations on the causes and results of that extinction

comparison of single and multiple flow direction algorithms for computing topographic parameters in topmodel single flow direction sfd and multiple flow direction mfd algorithms were used to compute the spatial and statistical distributions of the topographic index used in the watershed model topmodel an sfd algorithm assumes that subsurface flow occurs only in the steepest downslope direction from any given point an mfd algorithm assumes that subsurface flow occurs in all downslope directions from any given point the topographic index in topmodel is in a tan 3 where in is the napierian logarithm a is the upslope area per unit contour length and tan 3 is the slope gradient the in a tan 3 distributions were computed from digital elevation model dem data for locations with diverse topography in arizona colorado louisiana nebraska north carolina oregon pennsylvania tennessee vermont and virginia the means of the in a tan 3 distributions were higher when the mfd algorithm was used for computation compared to when the sfd algorithm was used the variances and skews of the distributions were lower for the mfd algorithm compared to the sfd algorithm the differences between the mfd and sfd algorithms in the mean variance and skew of the in a tan 3 distribution were almost identical for the various dems and were not affected by dem resolution or watershed size topmodel model efficiency and simulated flow paths were affected only slightly when the in a tan 3 distribution was computed with the sfd algorithm instead of the mfd algorithm any difference in the model efficiency and simulated flow paths between the sfd and mfd algorithms essentially disappeared when the model was calibrated by adjusting subsurface hydraulic parameters

mixed continental marine biotas following the permian triassic mass extinction in south and north china abstract correlation between marine and continental permian triassic p tr strata is crucial for full understanding of the nature of this global extinction event but it has proved difficult to achieve here we show that two sections in south china and north china record similar mixed continental marine biota in the post extinction stratigraphic interval including conchostracans plants insects marine bivalves and lingulid brachiopods in addition the continental p tr mass extinction was represented by a sharp decrease in the diversity and abundance of the gigantopteris flora in south china but eliminated the palaeozoic type conifer flora and herbivorous pareiasaurs in north china these mixed continental marine biota provide the biological evidence for stratigraphic correlation between marine and continental p tr transitional beds in south china and north china especially the co occurrence of the pteria towapteria eumorphotis bivalve assemblage and the euestheria gutta bearing conchostracan fauna or euestheria gutta magniestheria mangaliensis palaeolimnadiopsis vilujensis conchostracan assemblage we propose that these specific marine bivalve and continental conchostracan assemblages could be considered as markers of p tr transitional beds in marine continental siliciclastic settings

inclusion of the weathering of volcanic rocks in the geocarbsulf model the carbon cycle model geocarbsulf is extended by dividing the weathering of silicates into volcanic and non volcanic rocks the proportion of volcanic weathering is calculated as a function of time from the oceanic record of 87sr 86sr the volcanic proportion is then used to modify the equations for calculating atmospheric co2 by the addition of a new non dimensional volcanic weathering factor the effect of uplift and physical erosion on weathering is also modified by using only the distribution over time of the abundance of sandstones and shales and not sr isotopic data that had been used previously results indicate moderate change from geocarbsulf in the distribution of atmospheric co2 over phanerozoic time this includes an increased minimum in co2 during the late ordovician in agreement with the presence of a continental glaciation at that time and a shift of maximum mesozoic values from the jurassic to the early cretaceous

new sedimentological and structural data from the ecemis fault zone southern turkey implications for its timing and offset and the cenozoic tectonic escape of anatolia fig 1 map of the cukurba abg demirkazik area adapted from cetin 2000 fig 6 tcu is the

three dimensional landscape process modelling the effect of dem resolution many landscape models have been developed over the past decades however relatively little is known about handling the effects of changing spatial and temporal resolutions therefore resolution effects remain a factor of uncertainty in many hydrological and geomorphological modelling approaches in this paper we present an experimental multi scale study of landscape process modelling emphasis was laid on quantifying the effect of changing the spatial resolution upon modelling the processes of erosion and sedimentation a simple single process model was constructed and equal boundary conditions were created using artificial digital elevation models dems eliminated effects of landscape representation the only variable factors were dem resolution and the method of flow routing both steepest descent and multiple flow directions our experiments revealed an important dependency of modelled erosion and sedimentation rates on these main variables the general trend is an increase of erosion predictions with coarser resolutions an artificial mathematical overestimation of erosion and a realistic natural modelling effect of underestimating resedimentation cause this increasing the spatial extent eliminates the artificial effect while at the same time the realistic effect is enhanced both effects can be quantified and are expected to increase within natural landscapes the modelling of landscape processes will benefit from integrating these types of results at different resolutions

catastrophic soil erosion during the end permian biotic crisis organic geochemical analyses of sedimentary organic matter from a marine permian triassic transition sequence in northeastern italy reveal a significant influx of land derived diagenetic products of polysaccharides this unique event reflects massive soil erosion resulting from destruction of land vegetation due to volcanogenic disturbance of atmospheric chemistry the excessive supply of soil materials to the oceans provides a direct link between terrestrial and marine ecological crises suggesting that ecosystem collapse on land could have contributed to the end permian marine extinctions

strontium isotope evolution of late permian and triassic seawater the 87sr 86sr values based on brachiopods and conodonts define a nearly continuous record for the late permian and triassic intervals minor gaps in measurements exist only for the uppermost brahmanian lower part of the upper olenekian and middle norian and only sparse data are available for the late permian these 219 measurements include 67 brachiopods and 114 conodont samples from the tethyan realm as well as 37 brachiopods and one conodont sample from the mid european middle triassic muschelkalk sea the late permian lower triassic interval is characterized by a steep 1 3 10 3 rise from 0 7070 at the base of the dzhulfian to 0 7082 in the late olenekian a rate of change comparable to that in the cenozoic in the mid triassic anisian and ladinian the isotope values fall to 0 7075 followed again by a rise to 0 7081 in the middle late norian the 87sr 86sr values decline again in the late norian sevatian and rhaetian to 0 7076 the sharp rise in the 87sr 86sr values during the late permian early triassic was coincident with widespread clastic sedimentation because of the paucity of tectonic uplifts the enhanced erosion may have been due to intermittent humid phases during mainly an arid interval coupled with the absence of a dense protective land plant cover following the mass extinction during the latest permian the apex of the 87sr 86sr curve at the olenekian anisian boundary coincides with cessation of the large scale clastic sedimentation and also marks the final recovery of land vegetation as indicated by the renewed onset of coal formation in the middle triassic the rising 87sr 86sr values from the middle carnian to the late norian coincide with the uplift and erosion of the cimmeride indosinian orogens marking the closure of the palaeotethys the subsequent rhaetian decline that continues into jurassic pliensbachian toarcian boundary on the other hand coincides with the opening of the vardar ocean and its eastern continuation in the izmir ankara ophiolitic belt samples from the upper muschelkalk are more radiogenic than the global trend this may reflect separation of the basin from the open ocean due to strong meteoric influx from a large land mass in the north the germanic basin became increasing brackish up section in the north and east but because of the high evaporation rates the salt content was not much reduced in the southern and central basin where a rich but increasingly endemic marine fauna survived

geologic constraints on bedrock river incision using the stream power law denudation rate in unextended terranes is limited by the rate of bedrock channel incision often modeled as work rate on the channel bed by water and sediment or stream power the latter can be generalized as ka m s n where k represents the channel bed s resistance to lowenng whose variation with lithology is unknown a is drainage area a surrogate for discharge s is local slope and m and n are exponents whose values are debated we address these uncertainties by simulating the lowering of ancient river profiles using the finite difference method we vary m n and k to match the evolved profile as closely as possible to the corresponding modern river profile over a time period constrained by the age of the mapped paleoprofiles we find at least two end member incision laws ka 0 3 0 5 s for australian rivers with stable base levels and k f a 0 1 0 2 s n for rivers in kauai subject to abrupt base level change the long term lowering rate on the latter expression is a function of the frequency and magnitude of knickpoint erosion characterized by k f incision patterns from japan and california could follow either expression if they follow the first expression with m 0 4 k varies from 10 7 10 6 m 0 2 yr for granite and metamorphic rocks to 10 5 10 4 m 0 2 yr for volcaniclastic rocks and 10 4 10 2 m 0 2 yr for mudstones this potentially large variation in k with lithology could drive strong variability in the rate of long term landscape change including denudation rate and sediment yield

minimizing the grid resolution dependence of flow routing algorithms for geomorphic applications the results of flow routing methods currently used in the geomorphic literature depend on grid resolution this poses a problem for landscape evolution models which must be independent of grid resolution to the greatest extent possible here i illustrate a refinement of currently used flow routing algorithms that yields unit contributing areas i e contributing areas per unit width of flow with minimal grid resolution effects i illustrate the application of this method in idealized topography in high resolution digital elevation models dems of real world topography and by integration into a landscape evolution model for ridge and valley topography the landscape evolution model produces grid resolution independent results in a more straightforward way than previous models for this type of landscape

two pulses of extinction during the permian triassic crisis over 90 of marine species were lost during the end permian extinction fossil data show that the crisis in china was marked by two distinct phases of marine extinction separated by a 180 000 year recovery period

palaeoseismology in steep terrain the big bend of the san andreas fault transverse ranges california transpressional tectonics are typically associated with restraining bends on major active strike slip faults resulting in uplift and steep terrain this produces dynamic erosional and depositional conditions and difficulties for established lines of palaeoseismological investigation consequently in these areas data are lacking to determine tectonic behaviour and future hazard potential along these important fault segments the big bend of the san andreas fault in the transverse ranges of southern california exemplifies these problems however landslides probably seismically triggered are widespread in the rugged terrain of the big bend fluvial reworking of these deposits rapidly produces geomorphic planes and lines that are markers for subsequent fault slip the most useful are offset and abandoned stream channels for these are relatively high precision markers for identifying individual faulting events palaeoseismological studies from the central big bend involving 14c ages of charcoal fragments from trench exposures illustrate these points and indicate that the past three faulting events including the great 1857 earthquake were relatively similar in scale each producing offsets of about 7 7 5 m the mean recurrence interval is 140 220 years the pre 1857 event here may be the 1812 event documented south of the big bend or an event which took place probably between 1630 and 1690 ground breakage in both events extended south of the big bend unlike the 1857 event where rupture was skewed to the north the preceding faulting event ruptured both to the north and south of the big bend and probably occurred between 1465 and 1495 all these events centred on the big bend and may be typical for this fault segment suggesting that models of uniform long term slip rates may not be applicable to the south central san andreas a slip rate estimate of 34 51 mm a 1 for the central big bend although uncertain may also imply higher slip in the big bend and highlights difficulties in correlating slip rates between sites with different tectonic settings slip rates on the san andreas may increase within the broad compressional tectonics zone of the big bend compared to the north and south where the plate boundary is a relatively linear and sub parallel series of dominantly strike slip faults partitioning slip within the big bend is inherently uncertain and insufficient suitably comparable data are available to sustain a uniform slip model although such models are a common working assumption

combining geomorphometry feature extraction techniques and earth surface processes research the way forward abstract in recent years the wealth of technological development revolutionised our ability to collect data in geosciences due to the unprecedented level of detail of these datasets geomorphologists are facing new challenges giving more in depth answers to a broad er range of fundamental questions across the full spectrum of the earth s and planetary processes this contribution builds on the existing literature of geomorphometry the science of quantitative land surface analysis and feature extraction translate land surface parameters into extents of geomorphological elements it provides evidence of critical themes as well as emerging fields of future research in the digital realm supporting the likely effectiveness of geomorphometry and feature extractions as they are advancing the theoretical empirical and applied dimension of geomorphology the review further discusses the role of geomorphometric legacies and scientific reproducibility and how they can be implemented in the hope that this will facilitate action towards improving the transparency and efficiency of scientific research and accelerate discoveries in geomorphology in the current landscape substantial changes in landforms ecosystems land use hydrological routing and direct anthropogenic modifications impact systems across the full spectrum of geomorphological processes although uncertainties in the precise nature and likelihood of changes exist geomorphometry and feature extraction can aid exploring process regimes and landscape responses taken together they can revolutionise geomorphology by opening the doors to improved investigations crossing space and time scales blurring the boundaries between traditional approaches and computer modelling and facilitating cross disciplinary research ultimately the exploitation of the available wealth of digital information can help to translate our understanding of geomorphic processes which is often based on observations of past or current conditions into the rapidly changing future

the influence of surface slope on the shape of river basins comparison between nature and numerical landscape simulations we investigate the influence of initial conditions of slope and surface roughness on the shape length to width aspect ratio of incipient drainage basins in numerical experiments of simple tilted surfaces using the cascade code of landscape evolution comparison with data on the shape of river basins in nature shows that simple rules of the steepest descent routing of water are sufficient to account for a natural range of incipient drainage basin shape independently of the erosion processes at work to produce numerical basins that respect the main aspect ratio of natural drainage basins one must use very low initial regional surface slopes of less than 1 at the scale of the entire drainage basins and a local roughness slope of less than 3 at the scale of local surface irregularities numerical studies addressing real study cases may take advantage of the relation between local roughness and regional slope in order to produce catchment aspect ratios similar to the natural studied cases

integrated sr isotope variations and global environmental changes through the late permian to early late triassic new 87sr 86sr data based on 127 well preserved and well dated conodont samples from south china were measured using a new technique la mc icpms based on single conodont albid crown analysis these reveal a spectacular climb in seawater 87sr 86sr ratios during the early triassic that was the most rapid of the phanerozoic the rapid increase began in bed 25 of the meishan section gssp of the permian triassic boundary ptb and coincided closely with the latest permian extinction modeling results indicate that the accelerated rise of 87sr 86sr ratios can be ascribed to a rapid increase 2 8 of riverine flux of sr caused by intensified weathering this phenomenon could in turn be related to an intensification of warming driven runoff and vegetation die off continued rise of 87sr 86sr ratios in the early triassic indicates that continental weathering rates were enhanced 1 9 times compared to those of the late permian continental weathering rates began to decline in the middle late spathian which may have played a role in the decrease of oceanic anoxia and recovery of marine benthos the 87sr 86sr values decline gradually into the middle triassic to an equilibrium values around 1 2 times those of the late permian level suggesting that vegetation coverage did not attain pre extinction levels thereby allowing higher runoff

permian triassic extinction pattern revealed by foraminifers and geochemical records in the central persian gulf southern iran abstract permian triassic boundary ptb foraminifers are studied from the upper part of the dalan formation and the base of the kangan formation in four wells a b e f on and near the qatar arc persian gulf iran isotope studies including 13c and 18o values from wells b and e and 87sr 86sr ratios in wells b e and f have also been carried out to possibly provide a high resolution extinction pattern of foraminifers in the ptb interval the latter has been thoroughly investigated in iran turkey south china vietnam slovenia carnic alps and bukk mountains kashmir greenland and serbia the distribution of the last appearance of foraminiferal genera from the ptb interval in all of the wells is very similar featuring a stepwise extinction from 3 to 2 m before the boundary and compares to that observed in some of the sections from elsewhere i e south china vietnam slovenia and serbia the 13c value in wells b and e shows a negative shift at the base of a thrombolite unit immediately after the considered ptb and another negative shift at about 11 m below it in well e the thrombolite unit is assumed as earliest triassic but questionable with no supportive conodonts the 18o isotope values in wells b and e demonstrate the same negative upward trend due to dysoxic or anoxic conditions in the end permian oceans the uniform reduction without any sharp incline in the 18o profile suggests concurrent global warming the highest 87sr 86sr ratio fluctuations in wells b e and f coincide with the appearance of thrombolites changes in the profiles of carbon oxygen and strontium isotopes close to the ptb in wells b e and f seem to correspond to lithofacies variations from limestone to dolostone and a reduction in foraminiferal diversity these changes substantiate a clear perturbation in the marine environmental and global geochemistry elements through the ptb interval the 13c 18o and 87sr 86sr values obtained from the studied wells are comparable to those in other ptb stratigraphic sections in the paleo tethyan region

static stress changes induced by the 1924 pasinler m 6 8 and 1983 horasan narman m 6 8 earthquakes northeastern turkey the 1924 pasinler 1983 horasan narman earthquakes which struck the erzurum region occurred on the ne sw trending horasan fault zone about 60 km east of erzurum basin the inversion of teleseismic seismograms the aftershock pattern and the surface faulting of the 30 october 1983 m s 6 8 horasan narman earthquake indicate that it had dominantly left lateral motion one moderately sized aftershock occurred 8 h after the main event and two others a year later on the ne extension of the fault zone the aftershock distribution dominantly overlapped with the horasan fault zone and the aftershocks also migrated from south west to north east within the year following the mainshock the results obtained from modelling of static stress changes caused by the 1983 earthquake are consistent with the spatial distribution of aftershocks macroseismic observations of the 1924 earthquake m s 6 8 indicated that this event occurred on the sw extension of the horasan fault zone static stress modelling of the 1924 earthquake by using the same input parameters of the 1983 event has shown that its occurrence increased the stress in the region of the 1983 rupture zone the static stress changes caused both by the 1924 and the 1983 earthquakes has increased the failure stress at the ne and sw extensions of the horasan fault zone and in narman area furthermore the stress has decreased in the vicinity of the erzurum fault zone east of the city of erzurum the largest city in eastern turkey and in the populated sarikamis area this might delay the occurrence of a future probable damaging earthquake in these areas

recurrent biotic rebounds during the early triassic biostratigraphy and temporal size variation of conodonts from the nanpanjiang basin south china eleven conodont zones are established for the lower triassic of the motianling section in the nanpanjiang basin south china detailed size measurements on 2244 p1 conodont elements demonstrate dynamic size variation patterns during the early triassic that are calibrated to the early triassic timescale and conodont zonation correlation of conodont size variation with various environmental indicators shows that these size changes are primarily controlled by rapidly changing and episodic environmental conditions and ecological recovery in the aftermath of the end permian mass extinction decreasing size trends occur in the early griesbachian late griesbachian and at the smithian spathian boundary episodes of size increase rebounds occur in the middle griesbachian induan olenekian boundary and middle late spathian the observed temporal size variations indicate that conodont animals were significantly affected by rapidly changing environmental conditions mainly temperature and redox conditions during the early triassic and recurrent size increases rebounds occurred during periods of environmental and climatic amelioration climatic cooling and oxygenation demonstrating a complicated recovery history of marine ecosystems in the aftermath of the largest phanerozoic biotic crisis supplementary material data for all species are available at https doi org 10 6084 m9 figshare c 4528616

early cenozoic glaciation antarctic weathering and seawater 87sr 86sr is there a link abstract stable and radiogenic isotopic and sedimentological data from sub antarctic deep sea sediment cores reveal a temporal link between changes in seawater 87 sr 86 sr ratios and major episodes of late eocene early oligocene climate change the 87 sr 86 sr records show two major inflections one at 38 39 ma near the middle late eocene boundary followed by another at 33 4 ma similarly the oxygen isotope ice rafted debris and clay assemblage records indicate two important climatic events the appearance of alpine glaciers and or small ice sheets on antarctica in the late eocene at 38 39 ma followed by a rapid transition to larger and more permanent temperate ice sheets in the early oligocene at 33 4 ma moreover during the early oligocene 30 33 ma three to four inferred peaks in glacial activity appear to coincide with subtle steps in the 87 sr 86 sr record the coupled variations in climate and seawater sr isotope ratios during the eocene oligocene imply a strong causal link between the two either changes in climate directly influenced patterns of continental weathering and hence seawater chemistry and or a tectonic event e g uplift as reflected in weathering and seawater chemistry triggered relatively abrupt changes in global climate