a re evaluation of the mid cretaceous sauropod hiatus and the impact of uneven sampling of the fossil record on patterns of regional dinosaur extinction the mid cretaceous of north america and europe has long been noted for the absence of sauropod dinosaurs leading several authors to suggest that this depauperate interval is a consequence of an end albian sauropod extinction this time period has become known as the mid cretaceous sauropod hiatus with the subsequent presence of titanosaurian sauropods in the latest cretaceous of north america and europe interpreted as the result of dispersal of taxa from south america and africa respectively however several lines of evidence indicate that this hiatus is probably a sampling artefact new fossil and tracicway discoveries have considerably shortened the hiatus reducing it to the turonian early campanian in north america and to just two short intervals in the late cenomanian early turonian and late coniacian santonian of europe palaeoenvironmental analyses of sauropods demonstrate an inland terrestrial preference for titanosaurs the dominant late cretaceous sauropods however during the hiatus there was a decline in inland deposits and increase in coastal sediments in europe and north america which would have greatly reduced the probability of preserving titanosaurs neither the decline in inland deposits nor the sauropod hiatus occurred elsewhere in the world statistical comparisons also demonstrate a significant positive correlation between fluctuations in inland deposits and sauropod occurrences during the mid late cretaceous in europe and north and south america lastly cladistic analyses do not place latest cretaceous north american and european titanosaurs within south american and african clades contradicting the predictions of the austral immigrant hypothesis the latter hypothesis also receives little support from biogeographical analysis of dispersal among titanosaurs thus the sauropod hiatus of north america and europe is most plausibly interpreted as the product of a sampling bias pertaining to the rarity of inland sediments and dominance of coastal deposits preserved in these two regions during the mid cretaceous the presence of titanosaurs in these areas during the latest cretaceous can be explained by dispersal from southern hemisphere continents but this is no more probable than descent from early cretaceous incumbent faunas or dispersal from asia c 2010 elsevier b v all rights reserved

a possible genetic relationship between orogenic gold mineralization and post collisional magmatism in the eastern kunlun orogen western china abstract controversies in orogenic gold deposits remain especially regarding the relative contribution of magmatic fluids to the mineralization the shuizhadonggou huanglonggou gold deposit in the wulonggou gold field of the eastern kunlun orogen western china consists mainly of sulfide disseminations in hydrothermally altered rocks with minor amounts of quartz sulfide veins coeval to or overprinting the disseminated ores gold mineralization is hosted in diverse lithologies i e early palaeozoic metamorphic rocks late silurian syenogranite and late triassic porphyritic granodiorite and quartz diorite and is structurally controlled by a second order nw trending sinistral normal ductile shear zone and its subsidiary structures along the first order central kunlun fault gold related hydrothermal alteration formed chlorite sericite quartz and calcite with associated sulfide minerals dominated by pyrite arsenopyrite lollingite and pyrrhotite two types of hydrothermal sericite separates from a gold mineralized syenogranite yielded two 40 ar 39 ar ages of 237 0 2 0 ma and 230 8 1 7 ma respectively which postdated the early triassic regional metamorphism and ductile deformation by 13 m y field relationships suggest that gold mineralization also overprinted 220 ma porphyritic granodiorites and quartz diorites these data indicate three gold mineralization events in the late triassic overlapped with post collisional magmatism in the orogen gold bearing sulfides have 34 s values mostly in the range of 2 0 5 5 consistent with a magmatic source of sulfur quartz from quartz pyrite sericite veins has calculated 18 o h2o values of 1 8 6 1 and d h2o of 63 to 107 the stable isotopic and geochronological data suggest a magmatic origin for the ore forming fluids therefore the shuizhadonggou huanglonggou and other gold deposits in the eastern kunlun orogen share many features of orogenic gold deposits e g multiple order ore controlling structures hydrothermal alteration mineralization styles close association between mineralization and magmatism and h o s stable isotope compositions and are genetically related to late triassic post collisional magmatism

comparative quality and fidelity of deep sea and land based nannofossil records variation in sampling intensity of the geological record has long been suspected to distort our view of the history of life when the taxonomic diversity of the same widespread group of marine nannoplankton coccolithophorids is estimated conventionally and separately from published land and deep sea fossil records the two curves are very different they track sampling intensities from their respective rock records more closely than they do each other however when sampling intensity is corrected for using two recently developed independent techniques a common underlying signal emerges from the two records this shows diversity rising steadily throughout the mesozoic with a marked drop after the cretaceous 64 58 ma and a long term decline beginning in the late eocene and extending to the early miocene we conclude that the observable fossil record is strongly shaped by sampling bias and that this is a significant confounding factor for biodiversity analysis furthermore based on currently available sources we find that the raw deep sea record is a worse estimator of diversity than the land based record

re os dating of pyrite from the tuolugou stratabound co au deposit eastern kunlun orogenic belt northwestern china abstract the tuolugou cobalt gold deposit in the northeastern margin of the qinghai tibetan plateau and central part of the eastern kunlun orogenic belt is the most recently discovered large cobalt gold discovery in qinghai province nw china exploration to date has identified a cobalt resource of greater than 20 000 t co with significant potential for expansion mineralization is largely confined to an e w striking volcano sedimentary sequence consisting of four lithological units that underwent extensive greenschist facies metamorphism and deformation all orebodies occur in stratiform or lenticular bodies within quartz albitite and sericite quartz schists and are concordant with lithological contacts the ores contain various amounts of pyrite the dominant ore mineral and display massive 80 pyrite banded 30 to 50 pyrite and disseminated re os dating shows that pyrite from different ore types has very low re and os concentrations in the range of 0 122 8 988 ppb and 0 003 0 054 ppb respectively isotope data on seven pyrite samples yield an isochron age of 429 29 ma 2 with an initial 187 os 188 os ratio of 0 2 mean square weighted deviates 7 9 on the 187 re 188 os 187 os 188 os plot which are close to the age of the host strata suggesting that primary cobalt mineralization in the tuolugou deposit may have formed from syngenetic exhalative processes in addition our results not only provide new evidence for plate rifting and mineralization taking place during the early silurian in the eastern kunlun orogenic belt but also suggest that the age of the regionally widespread nachitai group is early paleozoic

pterosaur diversity untangling the influence of sampling biases lagerstatten and genuine biodiversity signals abstract pterosaurs were a diverse and successful group of mesozoic reptiles with an evolutionary history that extended for approximately 145 myr recent attempts to understand species richness trajectories for pterosaurs have led to them becoming a focal group for ongoing debate about the importance of sampling biases in determining observed species richness patterns in the vertebrate fossil record here we reanalyse pterosaur species richness through time and make statistical comparisons to proxies for pterosaur fossil record sampling and global terrestrial tetrapod sampling using several approaches including generalised least squares multiple regression models moreover we make quantitative comparisons between species richness and morphological diversity disparity sampling of the pterosaur fossil record shows substantial temporal heterogeneity with cretaceous pterosaur records more commonly recovered from terrestrial environments and with sampling proxies for cretaceous pterosaurs closely tracking global sampling proxies for terrestrial tetrapods the similarities between pterosaur based and global sampling proxies for cretaceous data call into question the hypothesis that observed correlations between pterosaur sampling proxies and pterosaur species richness result from mere redundancy multiple regression modelling supports the hypothesis that much of the variation present in pterosaur palaeobiodiversity curves results from a combination of the presence or absence of lagerstatten sites of exceptional preservation and a background sampling signal that may reflect temporal variation in fossiliferous sedimentary rock despite these evident strong biases in the pterosaur record it seems plausible that both species richness and disparity peaked relatively late in the evolutionary history of pterosaurs during the late jurassic early cretaceous although an absence of pterosaur bearing terrestrial lagerstatten in the late triassic early jurassic fossil record means that caution is required it is possible that a late peak in diversity may reflect the ecological radiation of pterodactyloid pterosaurs from the late jurassic onwards which has been linked to increased terrestrial locomotory abilities and ecological niche occupancy and relaxed constraints upon body size evolution

early pleistocene uplift of the northeastern tibetan plateau evidence from the dunhuang basin nw china abstract the cenozoic uplift of the tibetan plateau plays an important role in global climate change basin mountain geomorphology formation and desertification in western china as an important component the early pleistocene uplift process and its influence on the northeastern tibetan plateau has been controversial for many years quaternary synorogenic sediments within the dunhuang basin on the northeastern tibetan plateau record the details of plateau uplift detailed grain size analysis rock magnetic properties mudstone 36cl dating and 40ar 39ar detrital mica dating were conducted on the quaternary alluvial fluvial lacustrine aeolian sediments of the dunhuang basin the aksay section in the southern dunhuang basin is dominated by conglomerate sandstone siltstone and mudstone detrital mica 40ar 39ar ages show major age populations of 200 160 ma 400 200 ma and 510 430 ma from the northeastern altyn mountains the results of 36cl ages and rock magnetic properties show that the altyn mountains rapidly uplifted at 1 16 ma from 1 16 to 0 80 ma the sedimentary environment was stable with two small scale uplift pulses at ca 1 03 ma and 0 98 ma after 0 80 ma the climate became arid and the kumtag desert formed in the dunhuang basin these multistage uplifts are also widely found in the northeastern tibetan plateau the early pleistocene uplift of the altyn mountains corresponding to the kunhuang movement resulted in the northeastern margin of the tibetan plateau reaching its present height and climate changeing towards drought in this region

no gap in the middle permian record of terrestrial vertebrates during the permian tetrapods showed a major transition from basal synapsid dominated faunas in the first half to therapsid dominated faunas in the second the transition was significant in marking the beginning of richer and more complex communities a precursor to modern terrestrial ecosystems this changeover may have been gradual or abrupt but its study has been complicated by the postulated occurrence of a substantial hiatus in the fossil record termed olson9s gap which obscured the nature of the turnover new evidence from redating of key tetrapod bearing units of the american southwest and european russia confirms that there is no gap in the fossil record of permian tetrapods indeed evidence for substantial sampling bias in the permian tetrapod fossil record as a whole is queried

mayum an orogenic gold deposit in tibet china abstract located in western tibet china the mayum orogenic gold deposit was discovered in 2002 with estimated resources of 80 tonnes gold the gold mineralization is hosted by neoproterozoic cambrian schists and is controlled by nearly parallel e w trending bedding concordant fracture zones the au orebodies are composed of auriferous quartz veins and altered rocks with the au grades ranging from 2 23 g t to 69 56 g t and containing the 34s values of 18 separates of sulfides from auriferous quartz veins show a large variation from 0 2 to 16 8 the lead isotope compositions of sulfides from the gold ore are characterized by highly radiogenic values and very wide ranges of ratios 18 324 to 20 819 for 206pb 204pb 15 679 to 15 856 for 207pb 204pb and 38 401 to 41 204 for 208pb 204pb these data indicate that lead and sulfur in the quartz veins have multiple sources and were derived from the different wall rocks as the fluid flowed through them fluid inclusions indicate that the ore fluid was co2 rich with salinities mainly between 1 and 6 wt nacl equiv and homogenization temperatures predominantly ranging from 260 to 280 c the 18o values for quartz from auriferous veins range from 13 7 to 16 3 and the calculated 18oh2o values in equilibrium with quartz vary from 5 54 to 9 48 it suggests that the ore fluid may be derived from deep metamorphic deep crustal gold transporting fluids although a contribution from magmatic source cannot be ruled out 40ar 39ar age dating on the sericite from the alteration associated with the auriferous quartz veins in the mayum gold deposit gives a plateau like age of 59 34 0 62 ma later than the onset of the indo asian collision it is believed the gold mineralization was related to the indo asian collision and was formed during the early stage of orogenesis

a survey of palaeontological sampling biases in fishes based on the phanerozoic record of great britain fishes represent more than half of all living vertebrate species but patterns of fish diversity remain little explored in the fossil record a compendium of fossil occurrences from great britain was assembled in order to address a series of questions concerning the palaeontological record of fishes there are broad similarities between british richness trajectories and those compiled from global data including an initial peak in the mid palaeozoic devonian or carboniferous depending on the compilation with a late palaeozoic trough followed by a sharp rise in diversity in the late cretaceous and paleogene the british dataset is too small to reveal any significant differences in richness between time bins using subsampling but a modelling approach based on sampling and geological proxies consistently shows lower than predicted richness in the silurian devonian and higher than predicted richness in the late cretaceous and eocene this positive excursion is robust to the exclusion of data from the early eocene london clay lagerstatte chondrichthyans sharks rays and ratfishes and osteichthyans ray finned and lobe finned fishes show contrasting relationships with geological and sampling proxies possibly reflecting different taphonomic profiles or idiosyncratic variation in the relative proportion of freshwater and marine deposits over the british phanerozoic

chemical weathering in two adirondack watersheds past and present day rates rates of chemical weathering in two forested adirondack watersheds were determined from mineral and elemental depletion trends in soil profiles and from input output budgets based on precipitation and surface water chemistry long term rates of weathering have averaged about 500 to 600 eq ha yr for both watersheds since the glaciers retreated from the region about 14 000 yr ago present day denudation rates average 1679 eq ha yr in the panther lake watershed and only 198 eq ha yr in the woods lake watershed mineral weathering reactions in both watersheds involve primarily the dissolution of plagioclase potassium feldspar and hornblende mass balance calculations however indicate that hornblende weathers in disproportionately large amounts in the panther lake watershed relative to its abundance in soils and till cation exchange in the glacial till mantling the panther lake watershed may also play an important role in controlling surface water chemistry in the basin in the panther lake watershed the current rate of weathering which is about a factor of 3 greater than the long term average may reflect a recent adjustment for higher hydrogen ion fluxes brought about by acid deposition the capacity of the thick till deposits in the panther lake watershed to neutralize acidity is ultimately reflected by the circum neutrality of panther lake in the woods lake watershed the soils and thin till deposits cannot effectively neutralize current acid loadings and therefore woods lake is acidic with a ph below 5

geological and anthropogenic controls on the sampling of the terrestrial fossil record a case study from the dinosauria dinosaurs provide excellent opportunities to examine the impact of sampling biases on the palaeodiversity of terrestrial organisms the stratigraphical and geographical ranges of 847 dinosaurian species are analysed for palaeodiversity patterns and compared to several sampling metrics the observed diversity of dinosaurs theropoda sauropodomorpha and ornithischia are positively correlated with sampling at global and regional scales sampling metrics for the same region correlate with each other suggesting that different metrics often capture the same signal regional sampling metrics perform well as explanations for regional diversity patterns but correlations with global diversity are weaker residual diversity estimates indicate that sauropodomorphs diversified during the late triassic but major increases in the diversity of theropods and ornithischians did not occur until the early jurassic diversity increased during the jurassic but many groups underwent extinction during the late jurassic or at the jurassic cretaceous boundary although a recovery occurred during the cretaceous only sauropodomorphs display a long term upward trend the campanian maastrichtian diversity peak is largely a sampling artefact there is little evidence for a gradualistic decrease in diversity prior to the end cretaceous mass extinction except for ornithischians and when such decreases do occur they are small relative to those experienced earlier in dinosaur evolution the geological society of london 2011

chemical weathering in granitic environments abstract factors controlling chemical weathering in granitic environments are deduced using an extensive database from the literature based on a transition state theory model we evaluated the effects on chemical weathering of runoff temperature and ph the dependence between temperature and runoff and chemical weathering is complicated by other factors such as the presence depth of soil cover soil cover favors chemical weathering when it is thin and rich in weatherable minerals in contrast it reduces chemical weathering when is thick and poor in primary minerals processes that increase the contact time and the surface of the water rock interactions such as physical denudation increase chemical weathering rates in granitic environments the effect of temperature can be quantified assuming an apparent activation energy value of 48 7 kj mol to describe chemical weathering of silica in granitic crystalline environment under high runoff conditions

uplift of the central andean plateau and bending of the bolivian orocline the topography of the central andes can be considered the primary tectonic signal of late cenozoic mountain building in an arid region where the effects of uplift and magmatism are little obscured by denudation the spatial coverage of the topographic signal is more complete than that for sparsely sampled geological and geophysical data a color coded image of digitized topography between 12 s and 37 s highlights the altiplano puna one of the world s most remarkable plateaus and reveals important physiographic clues about the formation of that major feature the topographic data combined with information on structure magmatism seismicity and paleomagnetism support a simple kinematical model for the late cenozoic evolution of the central andes the model does not require collisional effects or enormous volumes of intrusive additions to the crust but instead calls upon plausible amounts of crustal shortening and lithospheric thinning the model interrelates andean uplift a changing geometry of the subducted nazca plate and a changing outline in map view of the leading edge of the south american plate crustal shortening has accommodated convergence between the chilean peruvian forearc and the south american foreland the altiplano puna plateau can be constructed by a combination of crustal shortening and thickening and lithospheric thinning above a shallow dipping 20 30 subducted plate the seawardly concave bend of western south america the bolivian orocline was enhanced but not completely produced by an along strike variation in the amount of late cenozoic shortening maximum shortening in bolivia both produced the widest part of the plateau and increased the seaward concavity of the bolivian orocline the along strike variations of shortening are hypothesized to result from corresponding along strike variations in the width of a weakened zone in the overriding plate weakening occurs above the wedge of asthenosphere located between the subducted and overriding plates hence the width of the zone of weakening depends upon the dip of the subducted plate two types of shortening are recognized 1 a widespread basin and range laramide like shortening that characterizes modem activity in the sierras pampeanas and late miocene deformation of the altiplano puna and 2 on the eastern side of the cordilleras and plateau an east verging foreland fold thrust belt in which the underthrust foreland compresses and thickens the ductile lower crust and produces a plateau uplift of the upper crust the second type of shortening can be applied to plio quaternary deformations throughout the central andes but with a substantial narrowing of the region of plateau uplift in peru and south of 28 s a proposed monoclinal flexure of the upper crust on the western side of the plateau uplift explains the remarkably simple and regular morphology of the main western slope of the central andes the monocline is located above the tip of the asthenospheric wedge between the converging plates it is postulated to occur above the western limit of lower crustal thickening in the regions of horizontal subduction the monocline can be associated with a late miocene asthenospheric wedge tip

successive approximations of diversity curves ten more years in the library traditional paleontological diversity curves are based on tallies of all taxa appearing in formally defined time units these tallies are thought to be robust to further data collection thus they supposedly do not reflect nuisance factors like variable time unit lengths and sampling intensity biases a comparison of a decade old north american cenozoic mammal diversity curve and a newer database shows major differences at least three major factors differentiate the two use of shorter fixed length time intervals restriction of counts to taxa that cross boundaries between intervals and correction for variation in sampling intensity the difference between genus and species level data also was examined but appears to be minor by comparison because at best only one pattern can be close to the true historical trajectory the analyses suggest that the new data and protocols together have yielded a curve that is converging on an accurate signal

vertebrate diversity across the end permian mass extinction separating biological and geological signals abstract this study examines regional diversity patterns of permian triassic terrestrial vertebrates of the south african karoo basin and the russian fore ural region previous studies clearly established that the diversity patterns of synapsids the dominant terrestrial tetrapods of their time are significantly biased by heterogeneity in the permian triassic terrestrial rock record this conclusion was based on a positive correlation between taxonomic diversity estimates tdes and varying sampling proxies 1 number of formations and 2 outcrop area recently these proxies have been criticized to be non independent variables or problematic for other reasons and 3 number of localities or 4 number of specimens have been suggest as more reliable proxies in the present study i test the relevance of the latter proxies 2 4 with respect to vertebrate diversity in south africa and russia on these regional scales log transformed and generalized differenced tdes of vertebrates at varying taxonomic levels are with few exceptions not significantly correlated with the various sampling proxies 2 4 for the complete time series after eliminating the impact of the end permian extinction event by excluding the earliest triassic time intervals selected vertebrate tdes in south africa and russia show statistically significant strong positive correlations with outcrop area number of localities and number of specimens diversity residuals resulting from modeled diversity estimates exhibit clade specific patterns with little support for a mid permian end guadalupian event but strong support for a severe end permian extinction the results imply that although vertebrate diversity patterns in south africa and russia are at least partially biased by the permian triassic terrestrial rock record they still preserve genuine biological signals finally it is important to note that outcrop area represents a valid and useful sampling proxy at the regional scale of the south african karoo basin and that it should be used in concert with other sampling proxies such as the number of localities and specimens that accurately capture various aspects of sampling in a given study area as it has been performed in the present study

diversity and climate change in the middle late wasatchian early eocene willwood formation central bighorn basin wyoming abstract densely distributed mammal samples from the willwood formation in the central part of wyoming s bighorn basin span episodes of major climate change previous work has focused on dramatic short term 0 5 myr during a 1 myr period of relatively static cool temperatures and a subsequent 1 myr period of warming that begins with the biohorizon b event and ends with the early eocene climatic optimum eeco in which the earth reached the hottest temperatures of the cenozoic geographic information systems is used to create spatially constrained subsamples to limit and explore the effects of the species area relationship on multiple aspects of diversity including the alpha average locality and beta locality differentiation components of species richness and the evenness and relative dominance of species abundance distributions results demonstrate previously unrecognized spatial bias in the upper levels of the section that complicate the interpretation of faunal response to the eeco evenness is strongly related to alpha richness whereas beta richness and dominance vary independently evenness increases significantly and richness becomes significantly more variable during warming richness also increases but the rise in alpha richness is not significant and the rise in beta richness is equivocal the dominance of the fauna by two abundant lineages escalates consistently regardless of changes in temperature diversity is not obviously affected across the biohorizon b event indicating that further study is necessary

mass extinctions and sea level changes abstract review of sea level changes during the big five mass extinctions and several lesser extinction events reveals that the majority coincide with large eustatic inflexions the degree of certainty with which these eustatic oscillations are known varies considerably thus the late ordovician and end cretaceous extinctions are associated with unequivocal major regressions demonstrated from numerous widespread regions in contrast the multiple high frequency sea level changes reported for the frasnian famennian crisis based on the supposed depth preferences of conodont taxa have little support from sequence stratigraphic analyses which reveals the interval to be one of highstand the end permian mass extinction has long been related to a severe first order lowstand of sea level newell n d 1967 revolutions in the history of life geol soc am spec pap 89 63 91 based primarily on the widespread absence of latest permian ammonoid markers but field evidence reveals that the interval coincides with a major transgression newell s hypothesis that marine extinctions are related to shelf habitat loss during severe regression remains tenable for the end guadalupian and end triassic extinction events but not for other crises rapid high amplitude regressive transgressive couplets are the most frequently observed eustatic changes at times of mass extinction with the majority of extinctions occurring during the transgressive pulse when anoxic bottom waters often became extensive the ultimate cause of the sea level changes is generally unclear a glacioeustatic driving mechanism can only be convincingly demonstrated for the end ordovician and end devonian events at other times it is speculated that they may relate to the widespread regional doming and subsequent collapse caused by the impingement of superplumes and ultimate eruption on the base of the lithosphere

determinants of extinction in the fossil record the causes of mass extinctions and the nature of biological selectivity at extinction events are central questions in palaeobiology it has long been recognized however that the amount of sedimentary rock available for sampling may bias perceptions of biodiversity1 2 3 4 5 6 7 and estimates of taxonomic rates of evolution5 6 7 8 this problem has been particularly noted with respect to the principal mass extinctions5 6 7 8 9 10 11 12 here we use a new compilation of the amount of exposed marine sedimentary rock to predict how the observed fossil record of extinction would appear if the time series of true extinction rates were in fact smooth many features of the highly variable record of apparent extinction rates within marine animals can be predicted on the basis of temporal variation in the amount of exposed rock although this result is consistent with the possibility that a common geological cause determines both true extinction rates and the amount of exposed rock it also supports the hypothesis that much of the observed short term volatility in extinction rates is an artefact of variability in the stratigraphic record

ar ar dating of orogenic gold deposits in northern margin of qaidam and east kunlun mountains and its geological significance the region of northern qaidam margin and east kunlun mountains located in western qinghai province is a typical multiple orogenic belt in western china the multiple orogenic belt originally consisted of three microplates oulongbuluke qaidam and central kunlun together with some micro oceans and or aulacogens of different stages located respectively on the southern and northern sides of the microplates during early paleozoic north qaidam north kunlun and south kunlun extended into aulacogens and or micro oceans which were closed at the end of caledonian stage due to their soft collision with the contiguous microplates the microplates were combined with eurasia into one body in late paleozoic and shifted northward meanwhile the southern side of these microplates developed into the animaqing carboniferous permian micro ocean belonging to paleo tethys which was closed during middle late permian early middle triassic foreland deposits were formed on the southern side of the microplates and late variscan indosinian collisional granite and large scale shear zones were produced in the inner part of the microplates at the same time the sea ocean shifted southward and lower triassic deposits of passive continental margin were developed in northern bayan har on the southernmost side of the region which experienced collision and orogenic movement during middle late triassic thirteen orogenic gold deposits were discovered in the region of northern qaidam margin and east kunlun mountains all of which were formed in the multiple orogenic movement sericite samples selected from gold ores of six representative gold deposits were used to conduct ar ar dating and their ore forming ages are as follows 425 5 2 1 ma saibagou 409 4 2 3 ma qinglonggou 284 04 2 95 ma tanjianshan 246 3 ma yeluotuoquan 236 5 0 5 ma wulonggou and 218 6 3 2 ma dachang these age data show that the gold deposits were formed in late early paleozoic and late late paleozoic triassic and were products of the multiple orogeny in the region during caledonian and late variscan yindosinian they belong to typical orogenic gold deposits and were mainly formed in the late stage of collisional orogeny the gradual decrease in ages of the deposits from north to south is coincident with the spatial temporal tectonic shift of the multiple orogeny in this region

estimating the rock volume bias in paleobiodiversity studies to interpret changes in biodiversity through geological time it is necessary first to correct for biases in sampling effort related to variations in the exposure of rocks and recovery of fossils with age data from new zealand indicate that outcrop area is likely to be a reliable proxy of rock volume in both stable cratonic regions where the paleobiodiversity record is strongly correlated with relative sea level and on tectonically active margins in contrast another potential proxy the number of rock formations is a poor predictor of outcrop area or sampling effort in the new zealand case

geochemistry of surface waters and weathering effects in the upper catchment of the ctalamochita river cordoba s sierras pampeanas central argentina the chemical compositions of waters from the upper basin of the ctalamochita river draining the cordoba pampean ranges were analyzed to determine the chemical signature related to different forcings geochemical processes and solutes sources the catchment has four sub basins santa rosa river grande river quillinzo river and de los sauces river most of the riverine chemical compositions are dominated by the hco3 ca2 type to ca2 na mg2 the specific conductivity is higher in the santa rosa and de los sauces rivers 347 59 and 409 00 s cm respectively than in the grande and quillinzo rivers 125 56 and 87 54 s cm respectively mineral hydrolysis of andesine and oligoclase and the dissolution of calco magnesian limestone are the main dissolved solids contributors to the river waters higher contribution of bicarbonate ions is associated to those sub basin having quarry mining activity saturation indexes show that the santa rosa and de los sauces rivers are saturated with calcite dolomite and talc

weathering assessment in the achala batholith of the sierra de comechingones cordoba central argentina ii major hydrochemical characteristics and carbon dynamics la trucha is a granitic second order catchment 1 9 km2 average slope 5 placed at 1400 m elevation in the sierra de comechingones argentina 31 54 s 64 45 w 31 53 64 44 w the main geochemical characteristics were studied during a hydrological year march 2005 february 2006 attending mainly seasonal and spatial variability and weathering induced carbon consumption subjected to a weathering limited denudation regime the catchment is representative of hundreds of the second order streams that dissect the achala batholith water chemistry is typical of streams draining f rich granites high discharges austral summer determine the dilution of na ca2 mg2 hco3 so42 and f conversely high summer rainfall increases cl concentrations the rainfall induced mobilization of k is likely masked by its affinity for adsorption onto fine grained particles and that of sio2 by its biological consumption la trucha s upper catchment shows that steep slopes and a shallow regolith layer result in a more diluted water flow chemically closer to rainfall subsurface flow increases the downriver positive rate of la trucha s electrical conductivity twice as much in winter 6 7 s cm 1 per 1000 m than during wet summer 3 9 s cm 1 per 1000 m phreeqc allowed the calculation of free co2 and the likelihood of its evasion in different seasons and areas of the catchment a mean carbon efflux of 180 mg c m 2 year 1 has been estimated for la trucha catchment the first and second order streams which occupy 62 5 km2 of the achala batholith s surface area are significant sources in the sierra de comechingones carbon cycle

the ties linking rock and fossil records and why they are important for palaeobiodiversity studies a correlation exists between the quality of the rock record and the diversity of fossils recorded from that rock record but what drives that correlation and how consistent that correlation is across different environments remain to be determined palaeontologists wishing to investigate past diversity patterns need to first address issues of geological bias in their data the fossil record provides the only empirical evidence of how life has diversified over geological time but it needs to be interpreted with caution for many years the history of diversity was estimated simply by summing up the numbers of taxa species genera families palaeontologists have recorded from successive geological time intervals or extrapolated from their first and last occurrences in the geological record this time series approach led to what is now a classic view of how diversity has changed over time sepkoski et al 1981 benton 1995 sepkoski 1997 such counts take the fossil record at face value or assume that biases or errors are randomly distributed in such a way that the overall effect is negligible we now realize that this is only a first crude approximation that may be subject to a number of strong biases that arise because of the nature of the sedimentary rock record time series analysis requires that sampling be carefully controlled for best results ideally data should be collected so that sampling from each time interval is uniform or at least sampled fairly using the shareholder quorum subsampling method alroy 2010 otherwise apparent changes in diversity may arise for spurious reasons for example because a a time intervals being sampled are of variable duration longer time intervals 1 4 more recorded diversity or b a time interval has been more intensively sampled more localities specimens habitats formations sampled 1 4 more recorded diversity while for a biological survey it is easy to plan a sampling strategy that will give approximately equal effort and coverage for observations palaeontologists are faced with a much more difficult task firstly the time bins they work with are irregular and highly variable in their duration for example the durations of one of the most widely used time scales has intervals spanning two orders of magnitude gradstein et al 2004 secondly and much more critically palaeontologists are collecting from an already incomplete and highly biased set of rocks which in turn skew the range of taxa and habitats that can be sampled zuschin et al 2011 bluntly put we cannot sample what is not preserved in the rock record although phylogenetic and molecular approaches can attempt to compensate pol norrell 2006 bininda emonds et al 2007 wills 2007 o connor et al 2011 so while it may be possible to standardize for sampling effort from the rock record that remains those rocks might provide a far from uniform sample of the sediments and palaeoenvironments that were originally present palaeontologists cannot therefore assume uniform sampling of the fossil record and must try to assess how the rock record they have to work with has affected their ability to sample evenly and then develop methods that compensate appropriately for this variation in recent years therefore palaeobiodiversity studies have become more probabilistic in their approach concerned with establishing confidence limits around estimates that try to correct for uneven sampling alroy et al 2001 2008 and testing empirical patterns against model predictions foote 2001 smith mcgowan 2007 mcgowan smith 2008 if we are to improve our estimates of biodiversity over time then sampling parameters need to be better quantified and we need to better understand the complex interrelationship between rock and fossil records this is no simple task and requires a more systematic approach to recording culture as well as better documentation of the variables benton et al 2011 figure 1 summarizes the problem as we see it palaeontologists estimate past diversity from remains preserved in the rock record as with any from mcgowan a j smith a b eds comparing the geological and fossil records implications for biodiversity studies geological society london special publications 358 1 7 doi 10 1144 sp358 1 0305 8719 11 15 00 the geological society of london 2011 biological survey variation of sampling effort of the surviving rock record needs to be factored out but this rock record has already passed through a geological filter that has altered and distorted not only the rock area that survives to sample but also the proportions of facies and the preservational quality of its fossil record were this geological filter to remain approximately constant over time there would be little problem of interpreting the biological signal however it is far from uniform with amounts of rock to sample proportions of facies represented by those rocks and preservation potential all varying from one time interval to the next to interpret observed changes in sampled biodiversity estimates correctly we must therefore first understand the role of the geological filter variability of the rock and fossil records

the first half of tetrapod evolution sampling proxies and fossil record quality abstract the first half of tetrapod evolution witnessed substantial diversification of the clade and several major turnovers and mass extinctions in the time since their origin more than 380 myr ago to the beginning of the middle jurassic 175 myr ago tetrapods apparently diversified fitfully reaching their highest level in the middle permian and showing major diversity declines in the late moscovian early permian wordian lower wuchiapingian end permian lower anisian lower ladinian late triassic lower norian to upper rhaetian end triassic and early jurassic upper sinemurian lower pliensbachian of these diversity drops only the end permian and end triassic correspond to recognised mass extinctions and the late moscovian and early norian drops to other previously identified environmental crises the remainder could be real extinction or turnover events or partially artefacts of biased sampling there are strong correlations between formation counts and tetrapod palaeodiversity suggesting a sampling component in the raw data but the covariation is not uniform through the whole time span being poor from devonian to middle permian and better from late permian to early jurassic there is limited evidence for covariation between the tetrapod palaeodiversity time series and other putative sampling metrics such as specimen completeness numbers of publications map areas gap bounded sedimentary units rock volumes formations and fossil collections modelling by multiple correlations shows that formation count is generally the best explanatory model either on its own or combined with other sampling time series however it is not clear that formation count is independent of the palaeodiversity time series because rises and falls in both signals could reflect variations in original diversity or in preservation or in sampling

the role of trace minerals in chemical weathering in a high elevation granitic watershed estibere france chemical and mineralogical evidence we investigated chemical weathering in a high elevation granitic environment in three selected watersheds located in the pyrenees france the sites were located on glacial deposits derived from similar hercynian 300 ma granites characterized by the occurrence of zoned plagioclases and trace calcic phases epidote prehnite sphene apatite the surface waters at those sites show high ca na molar ratios 1 which could not be explained by the dissolution of the major plagioclase oligoclase present in the rocks the coupled approach of investigating stream water chemistry and the mineralogy and chemistry of rocks and soils allowed us to explore the role of the weathering of trace calcic minerals in calcium export at the watershed scale the weathering of the trace calcic minerals which represent 1 of the total rock volume are responsible for more than 90 of the calcium export at the sites annual cationic fluxes 23 104 eq km2 yr calculated for the estibere watershed are among the highest reported for high elevation systems draining granitic rocks and 80 of this annual cationic flux can be attributed to the weathering of trace calcic phases calculations based on isotopic values 87sr 86sr go in the same direction except apatite the trace calcic phases appear to be mainly silicates thus the type of chemical weathering observed in the estibere watershed may have an influence on atmospheric co2 consumption by granite weathering however comparison with other watersheds draining granitic environments worldwide and with the two other sites in the pyrenees indicate that the role of trace calcic phases is important in most young environments exposed to chemical weathering e g high elevation catchments on glacial deposits other factors such as the date of glacial retreat the physical denudation rate the hydrological functioning of the watershed and the nature and structure of the soil cover are also important

the ciw index a new chemical index of weathering abstract a new chemical index of weathering that can be applied to modern soils and precambrian paleosis is proposed ciw al2o3 the value of this index increases as the degree of weathering increases and the difference between ciw index values of the silicate parent rock and soil or sediment reflects the amount of weathering experienced by the weathered material

multiple episodes of gold mineralization in the east kunlun orogen western central orogenic belt china constraints from re os sulfide geochronology abstract the gouli goldfield 110 t au located in the east kunlun orogen western central orogenic belt of china is one of the most important goldfields in this area in the last decade a number of orogenic gold deposits e g guoluolongwa and annage have been shown to be hosted by rock units of different lithology and ages rhenium osmium re os geochronology of sulfides from gold bearing veins was performed to define the chronologic relationships between gold mineralization present in the metamorphic rocks proterozoic and silurian of the east kunlun orogen sulfides pyrite and chalcopyrite from pyrite quartz vein and polymetallic sulfides quartz vein in the guoluolongwa gold deposit yield re os isochron dates of 374 15 ma mswd 4 6 initial 187os 188os ratio osi 0 06 0 22 and 354 7 ma mswd 0 18 osi 0 13 0 01 respectively similar ages are also revealed by the pyrite mineral separates from the annage gold deposit 383 8 ma and 349 6 ma these ages are interpreted to record the timings of the formation of the two vein types in these deposits which are nominally separated by 20 ma the new re os ages presented here identify the first two late paleozoic devonian and early carboniferous gold mineralizing events in the east kunlun orogen and thus indicate at least two mineralization epochs in this area given ages late triassic of other gold systems and field observations considering the geological background and temporal distribution of gold deposits in adjacent areas western qinling and qaidam qilian we suggest that gold deposits in the western central orogenic belt were formed in collisional post collisional settings being controlled by common tectonic magmatic activities related to the evolution of both the prototethys ocean proterozoic paleozoic and paleotethys ocean paleozoic early cenozoic further the initial os osi obtained from the re os isochron suggest that for the two vein types in the guoluolongwa gold deposit the os and by inference the ore metal au were derived from a mantle like source osi values 0 12 0 13 which should be related to the contemporaneous mantle like magmatism in contrast the pyrite quartz vein in the annage gold deposit possesses a significantly radiogenic osi value 3 65 0 51 given the similar timing of mineralization between the guoluolongwa and annage deposits it is considered that the ore metal likely has a similar origin i e a mantle like source however at annage the hydrothermal fluid interacted with the proterozoic metamorphic host rocks and leached radiogenic os that masks any evidence of a mantle like source

time constraints on the tectonic evolution of the eastern sierras pampeanas central argentina the application of the shrimp u pb dating technique to zircon and monazite of different rock types of the sierras de cordoba provides an important insight into the metamorphic history of the basement domains additional constraints on the pampean metamorphic episode were gained by pb pb stepwise leaching pbsl experiments on two titanite and garnet separates results indicate that the metamorphic history recorded by crd free gneisses m2 started in the latest neoproterozoic earliest cambrian 553 and 543 ma followed by the m4 metamorphism at 530 ma that is documented in the diatexites zircon ages of 492 ma in the san carlos massif correlate partly with rather low th u ratios 0 1 suggesting their growth by metamorphic fluids this age is even younger than the pbsl titanite ages of 506 ma it is suggested that the fluid alteration relates to the beginning of the famatinien metamorphic cycle in the neighbouring sierra de san luis and has not affected the titanite ages the ptt evolution can be correlated with the plate tectonic processes responsible for the formation of the pampean orogene i e the accretion of the pampean basement to the rio de la plata craton m2 and the later collision of the western pampean basement with the pampean basement

zircon u pb dating and sulfide re os isotopes of the xiarihamu cu ni sulfide deposit in qinghai province northwestern china the xiarihamu cu ni sulfide deposit is the second largest cu ni deposit in china located in the eastern kunlun orogenic belt however despite previous study the formation and evolution of this d

diversity trends in the establishment of terrestrial vertebrate ecosystems interactions between spatial and temporal sampling biases analyses of how fossil record sampling influences detection of past biodiversity change and geographic patterns of animal diversity are central to understanding macroevolution deep time macroecology and interactions between the rock and fossil records the diversification and establishment of complex trophic structure among terrestrial vertebrates tetrapods and three hypothesized mass extinctions occurred in the permian 299 0 252 3 ma during a predominantly icehouse global climate regime prominent short lived features of permian species diversity curves such as a possible end guadalupian mass extinction are robust to sampling biases however multivariate and time series approaches show that longer term trends in the accumulation of terrestrial biodiversity are more sensitive olson s extinction believed to have occurred at the end of the early permian might be an artifact of the abrupt geographic shift from predominant sampling of lower permian amphibian rich paleotropical everwet biome in north america to more tetrapod depauperate middle late permian cool paleotemperate biomes in russia and south america thus geographic heterogeneity in fossil record sampling superimposed on a prominent icehouse latitudinal biodiversity gradient might have created an artifactual macroevolutionary event this apparent event remains even after correcting data for uneven temporal sampling thus a complex interplay between spatial and temporal biodiversity trends and geographic and temporal sampling factors is responsible for generating observed past biodiversity patterns

the role of disseminated calcite in the chemical weathering of granitoid rocks accessory calcite present at concentrations between 300 and 3000 mg kg 1 occurs in fresh granitoid rocks sampled from the merced watershed in yosemite national park ca usa loch vale in rocky mountain national park co usa the panola watershed ga usa and the rio icacos puerto rico calcite occurs as fillings in microfractures as disseminated grains within the silicate matrix and as replacement of calcic cores in plagioclase flow through column experiments using de ionized water saturated with 0 05 atm co2 produced effluents from the fresh granitoid rocks that were dominated by ca and bicarbonate and thermodynamically saturated with calcite during reactions up to 1 7 yr calcite dissolution progressively decreased and was superceded by steady state dissolution of silicates principally biotite mass balance calculations indicate that most calcite had been removed during this time and accounted for 57 98 of the total ca released from these rocks experimental effluents from surfically weathered granitoids from the same watersheds were consistently dominated by silicate dissolution the lack of excess ca and alkalinity indicated that calcite had been previously removed by natural weathering the extent of ca enrichment in watershed discharge fluxes corresponds to the amounts of calcite exposed in granitoid rocks high ca na ratios relative to plagioclase stoichiometries indicate excess ca in the yosemite loch vale and other alpine watersheds in the sierra nevada and rocky mountains of the western united states this ca enrichment correlates with strong preferential weathering of calcite relative to plagioclase in exfoliated granitoids in glaciated terrains in contrast ca na flux ratios are comparable to or less than the ca na ratios for plagioclase in the subtropical panola and tropical rio icacos watersheds in which deeply weathered regoliths exhibit concurrent losses of calcite and much larger masses of plagioclase during transport limited weathering these results indicate that the weathering of accessory calcite may strongly influence ca and alkalinity fluxes from silicate rocks during and following periods of glaciation and tectonism but is much less important for older stable geomorphic surfaces

terrestrial and fluvial carbon fluxes in a tropical watershed nyong basin cameroon abstract the nyong watershed with an area of 27 800 km2 and a mean annual discharge of 390 m3 s 1 is the second largest river in cameroon the nyong watershed serves as an outstanding study area for the examination of carbon fluxes in humid tropical environments because of its limited anthropogenic impact and homogeneous silicate bedrock between april 2005 and april 2007 we sampled water at seven stations from the small watershed of the mengong 0 6 km2 to the nyong at edea 24 500 km2 and monitored temperature ph dissolved inorganic carbon dic and dissolved organic carbon doc contents as well as the isotopic composition of dic 13cdic and doc 13cdoc we estimated terrestrial net ecosystem productivity in the nyong river watershed and measured fluvial fluxes of carbon to the ocean and the atmosphere the nyong river basin sequesters significant amounts of carbon on an annual basis 7 920 000 t c year 1 300 g c m 2 year 1 the combined dissolved organic dissolved inorganic and atmospheric fluxes of carbon from the nyong river only export 3 of this flux from the basin on an annual basis this includes a minimum co2 outgassing of 1487 g c m 2 year 1 comparable to 115 of the annual flux of doc and four times greater than the flux of dic

the deep sea microfossil record of macroevolutionary change in plankton and its study the deep sea planktonic microfossil record foraminifera coccolithophores diatoms radiolaria and dinoflagellates provides a unique resource for palaeobiology despite some geographical gaps due to poor regional preservation and intermittant time intervals lost to erosion most time periods for each cenozoic planktonic biogeographical province are preserved vast numbers of specimens and numerous deep sea cores provide abundant material and the opportunity to tightly integrate macroevolutionary and palaeoenvironmental data current documentation of this record is mixed catalogues for foraminifera and coccolithophores offer nearly complete species level clade histories but taxonomy for siliceous microfossils is incomplete published occurrence data is primarily stratigraphic and covers only a fraction of the total preserved diversity age models for some sections are excellent accuracy c 100 kya but for many other sections are still poor taxonomic errors age model errors and reworking displace fossil occurrences in time complicating palaeobiological analysis with additional taxonomic work careful collection of whole fauna floral assemblage occurrence data improved age models and the development of better data filtering and analysis tools to deal with data outliers the deep sea microfossil record can deliver its promise of providing the most complete detailed record of macroevolutionary change available to science

weathering assessment in the achala batholith of the sierra de comechingones cordoba central argentina iii appraising chemical weathering la trucha is a small 1 9 km2 mountainous 1300 m a s l granitic drainage basin demonstrative of hundreds of second order basins in the achala batholith of the sierras pampeanas of cordoba argentina dominated by physical weathering and a weathering limited denudation regime the coarse and fine grained regolith has shown scant geochemical differences with the country rock erosion and sediment transport mainly occurs during torrential rain events austral summer whereas surface waters classify as dilute 750 t 375 eq l 1 or very dilute 375 t 185 eq l 1 water types the dynamics of chemical weathering at la trucha was approached through the use of major dissolved chemical components comparing the performance of different methodologies in its assessment mineral stability diagrams i e chemical equilibria the re chemical weathering index ternary diagrams and phreeqc inverse modeling the latter approach allowed to probe into subtleties of the geochemical processes indicating that besides the morphological dependency on mineral hydrolysis dissolution or precipitation there is a marked seasonal control that promotes or limits the occurrence of geochemical reactions

foraminiferal zonation of late paleozoic depositional sequences from the later part of the devonian through the permian calcareous foraminifers became abundant and evolved rapidly this rapid evolution of taxa forms the basis of a detailed zonation through the carboniferous and permian comparison of this evolutionary history of foraminifers their biostratigraphic zonation and the depositional sequences in which they occur suggests that sea level events in late paleozoic depositional history contributed significantly in subdividing a fairly continuous evolutionary record into a succession of about 75 identifiable foraminiferal zones during a 100 125 myr time span although variable in terms of duration and vertical occurrences the more completely recorded high stand intervals give brief histories of the foraminiferal evolutionary record and are sandwiched between the poorly recorded or unrecorded low stand intervals many of the individual foraminiferal zones are confined to a single depositional sequence the late paleozoic carbonate foraminiferal fossil record as with the rest of the fossil record is strongly affected by sediment deposition nondeposition as a result of major changes in sea level this incomplete fossil record is the result of repeated depositional breaks because of the way that depositional sequences form it is not possible to ascribe macromutations punctuated evolution or punctuated gradualism as the cause of this evolutionary pattern of the shelf carbonate fossil record this pattern is distinctive and we refer to it as sequence evolution and sequence extinction in the later part of the middle permian and in the late permian the fossil record clearly illustrates that a series of faunal losses through sequence extinctions progressively exceeded faunal replacements and new species through sequence evolution but not a mass extinction as is commonly ascribed to the end of the permian period most permian faunas became extinct in the interval of 8 to 4 million years before the end of the late permian

influence of geomorphological variables on mountainous stream water chemistry sierras pampeanas cordoba argentina abstract the relationship between geomorphological features and water geochemistry was studied for a group of mountainous rivers from 900 to 2200 m a s l with similar geology and climate in the sierras pampeanas of cordoba argentina 31 30 32 00 s and 64 30 65 10 w a multivariate approach was used to identify three morphological domains that describe the set of sampled rivers namely size dominance slope dominance and drainage density dominance the links between physicochemical and geomorphological variables show that size dominance is mostly related to major ions conductivity and ph which tend to increase downstream slope dominance is associated with the total concentration of heavy metal i e high heavy metal concentrations are associated with relatively flat areas with slightly acid to circumneutral ph which promotes desorption the drainage density dominance results in an association between well drained catchments and low cl concentration i e preserving the chemical signature of atmospheric precipitation

shape of mesozoic dinosaur richness the richness of mesozoic dinosauria is examined through the use of a new global database mesozoic dinosaurs show a steadily increasing rate of diversification in part attributable to the development of new innovations driving an increasing variety of behavioral strategies the data do not suggest that dinosaurs were decreasing in richness leading to extinction during the last 10 m y of the cretaceous refinement of the dating of dinosaur fossils rather than the collection of more dinosaurs is the best way to resolve globally the rate of the cretaceous tertiary dinosaur extinction

quantifying the deep sea rock and fossil record bias using coccolithophores while many studies show a correlation between observed taxonomic richness and various measures of geological sampling all have been based on the same record of terrestrial and marine sediments collected from the land here we present the first analyses of how rock and fossil records vary in the deep sea we have developed a novel database of species occurrences of coccolithophores sampled during major drilling programs of the north atlantic including the mediterranean and caribbean our sampling proxy the number of deep sea sites sampled perhaps the most direct measure of sampling used so far shows an exponential rise towards the recent over the same period species richness has grown in an approximately linear fashion but genus level richness shows a sharp initial increase followed by a much slower decline however correlations between both richness measures and sampling are extremely strong and a model assuming true diversity to be constant accurately predicts much of observed richness we conclude that the deep sea fossil record like its land based counterpart bears a rock record bias the geological society of london 2011

weathering assessment in the achala batholith of the sierra de comechingones cordoba central argentina i granite regolith fractionation abstract weathering assessment in a weathering limited environment is a difficult task because a significant proportion of the regolith has been removed by tectonically induced denudation in such an environment the remnants of the altered mineral debris must be studied with care in order to attain a meaningful picture of the rate and intensity of ongoing weathering a monolithologic i e granite small 2 km2 and mountainous 1500 m elevation drainage basin in the sierras de comechingones 31 54 07 s 64 45 28 w 31 53 11 s 64 44 16 w cordoba central argentina was selected as a pilot area to survey the nature of weathering in a weathering limited erosional setting and a semiarid climatic regime a relatively thin layered coarse grained regolith and scattered sediment i e fine grained regolith that had accumulated in valleys and topographic depressions were analyzed the most abundantly identified clay mineral in the regolith is illite followed by kaolinite smectite smectite seems to be the only clay mineral clearly associated with weathering petrographic observations and geochemical analyses supported by statistical tests define chemical weathering as incipient petrography indicates that plagioclase and biotite are the main mineral phases affected by alteration which is more intense in the fine grained regolith coarse and fine grained regoliths are chemically similar among them and with the country rock with statistically significant losses in the fine fraction of mgo mno and p2o5 depletions of trace elements and ree which are best explained by sorting than by actual rock alteration are not statistically significant ternary diagrams reveal that the masses of al2o3 cao na2o and k2o were not significantly altered during weathering and transportation and that regolith samples correspond to a coarse residue relatively enriched in feldspars and quartz where the mud fraction with high clay mineral contents has been removed from the drainage basin by high energy processes

cretaceous tetrapod fossil record sampling and faunal turnover implications for biogeography and the rise of modern clades we use newly compiled data on global occurrences of cretaceous lepidosaurs mammals and crocodylomorphs and existing data on dinosaurs to investigate faunal turnover and fossil record heterogeneity statistically significant relationships between many clade specific fossil record sampling proxies within major continental areas e g european mammal bearing formations suggest that temporal patterns of fossil record sampling intensity of the most abundant tetrapod clades are similar to each other with a few exceptions that might reflect clade specific facies preferences or differences in worker effort especially in poorly sampled regions such as gondwana however the absence of strong statistical relationships between tetrapod sampling proxies from different continental areas suggests that there is no unified global sampling signal for terrestrial tetrapods the cretaceous witnessed substantial faunal turnover and the rise of many advanced clades that today dominate terrestrial faunas despite strong spatiotemporal heterogeneity in sampling of the cretaceous tetrapod record it is clear that this transition occurred in a spatiotemporally staggered fashion thus it cannot be attributed to a temporally localised early late cretaceous cenomanian turonian extinction event many advanced clades including eutherian mammals iguanian and gekkotan squamates and the main cryptodiran turtle crown clades first appeared or first attained high fossil diversities in asia however relatively poor sampling and dating of middle cretaceous terrestrial deposits means that hypotheses of asian rather than laurasian diversifications remain tentative differences between gondwanan and laurasian faunas became progressively greater during the cretaceous and although many gondwanan clades survived the end cretaceous extinction event these only survive to the present as relictual populations with narrow geographic ranges e g monotremes and rhynchocephalians

flat latitudinal gradient in paleocene mammal richness suggests decoupling of climate and biodiversity mammal faunas from western north america exhibit no significant change in species richness with latitude during the torrejonian ca 63 60 ma and tiffanian ca 60 58 ma north american land mammal ages in contrast to a strong richness gradient in modern mammalian faunas of the same region today the latitudinal gradient in oxygen isotope composition of mammalian bioapatite from the paleocene faunas is similar to that of modern meteoric and surface waters suggesting that the temperature gradient in the paleocene was similar to the modern one the flat richness gradient in the middle paleocene indicates either different responses to climatic gradients of faunas dominated by extinct clades of placental mammals or distinct ecological processes during the paleocene diversification of mammals following the end cretaceous mass extinction

preservation and exhumation history of the harizha halongxiuma mining area in the east kunlun range northeastern tibetan plateau china abstract the extent to which ore bodies are preserved in orogenic belts remains a poorly understood area of ore deposit research using zircon and apatite fission track analysis together with apatite u th he dating we constrained the erosion history of the ore bodies in the harizha halongxiuma mining area of the east kunlun range northern tibetan plateau china apatite fission track ages range from 114 8 to 87 6 ma with mean track lengths varying from 11 4 1 9 to 12 9 2 0 m zircon fission track ages vary from 205 14 to 142 7 ma in addition apatite u th he dating yielded ages of 60 56 ma the thermal history of jiapigou was modelled based on the apatite fission track data including ages and track lengths with constraints of zircon fission track ages and u th he ages the exhumation history of the harizha halongxiuma mining area was reconstructed with these age data revealing that since the early mesozoic the area has undergone three cooling stages 1 rapid cooling from 175 30 ma to 100 10 ma with a cooling rate and inferred exhumation of 2 0 0 8 c myr and 4 3 1 7 km respectively 2 a relatively stable stage from 100 10 ma to 40 10 ma with a cooling rate and inferred exhumation of 0 3 0 1 c myr and 0 5 0 2 km respectively and 3 rapid cooling since 40 10 ma with a cooling rate and inferred exhumation of 1 2 0 6 c myr and 1 4 0 4 km respectively this exhumation history is consistent with the subduction process of pacific plate and the strike slip movements of dunmi fault the total exhumation after main mineralization is calculated to be 7 6 3 2 km suggesting that ore bodies in the harizha halongxiuma mining area remain partially preserved

marine diversity in the geological record and its relationship to surviving bedrock area lithofacies diversity and original marine shelf area biological principles suggest that recorded species diversity should increase as sampled area and habitat diversity increase however the interactions between earth system drivers of these physical quantities their representation in the preserved rock record and fossil species counts are debated we tracked marine bedrock area lithofacies diversity and echinoid species diversity through an 80 m y sea level cycle as recorded in the cretaceous of the united kingdom to test these relationships relative completeness of the rock record rises during transgression but drops rapidly at maximum flooding and continues to fall during highstand lithofacies diversity peaks during transgression but drops sharply as maximum flooding is reached whereas bedrock area peaks at maximum flooding then declines progressively through the highstand interval as a result of post cretaceous erosion both bedrock area and number of lithofacies units correlate with species diversity but species diversity is predicted best by the two combined there are no simple relationships between bedrock area and lithofacies diversity or the original area of marine sediments and range of habitats that once existed these variables are strongly shaped by stratigraphic architecture while the geological record left by a major sea level cycle accurately captures the biological evolution of local communities it is incomplete and systematically biased in its coverage of environments and communities erosional truncation of sediment packages and species ranges in the later stages of sea level cycles explains the reported asymmetric relationship between macroevolution and macrostratigraphy

non biotic controls of observed diversity in the paleontologic record an example from the permo triassic karoo basin of south africa paleodiversity trends through geologic time can be affected by a number of geologic taphonomic and anthropogenic biases that obscure or prejudice paleoecological patterns in the fossil record although much work has concentrated on the relationship between geologic exposure sample size and taxonomic richness i e number of taxa few studies have investigated the potential effects of dataset quality and changing taxonomy we use four different specimen level datasets of permo triassic tetrapods from the karoo basin of south africa to investigate how sample size geologic outcrop dataset quality and taxonomic revision all affect observed estimates of generic richness evenness and relative abundance our results indicate that large scale patterns of richness evenness and abundance such as the effects of the end permian mass extinction are generally robust to these potential biases across the four different datasets in contrast absolute values vary significantly as do finer scale patterns in agreement with past studies taxonomic errors revised taxonomy and new taxa have little effect on patterns of richness and evenness instead the addition of large numbers of new specimens to the dataset has the largest effect on these paleodiversity metrics despite application of sample standardization we conclude that although large specimen datasets hundreds to thousands of specimens are robust to various potential biases and can recover large scale paleobiologic trends they are still affected by many non biotic controls and workers should strive to improve dataset quality and understand the underlying reasons for observed paleodiversity patterns

contrasting patterns and connections of rock and biotic diversity in the marine and non marine fossil records of north america abstract macrostratigraphy uses packages of continuous sedimentation that are bound by hiatuses of non deposition erosion or alternations between environments lithologies to characterize spatiotemporal patterns of sedimentation previous work has linked the macrostratigraphy of marine shelf environments to many different macroevolutionary patterns in the marine animal fossil record here we use an improved macrostratigraphic database for north america combined with fossil occurrence data in the paleobiology database to show that macroevolutionary and macrostratigraphic patterns are correlated more strongly in marine environments than in non marine environments we also test the hypothesis that the temporal distribution of lithological diversity measured as evenness similar to ecological evenness based on the number of lithostratigraphic units with a given lithologic type within each time interval has a relationship to genus level taxonomic diversity in both the marine and non marine realms uneven sampling of lithologies and their corresponding depositional environments can bias our perception of taxonomic diversity by causing taxa from poorly sampled environments to be underrepresented in the fossil record our results show a negative correlation between lithologic evenness and marine vertebrate generic richness less even sampling of lithologies corresponds to a higher observed taxonomic richness and no correlation with lithologic evenness and non marine diversity measures this suggests a difference in the relationship between biologic and sedimentary processes at work in the marine and non marine realms and possibly differences in the magnitude of the bias imposed by the rock record on the underlying biologic patterns

sea level variations and the quality of the continental fossil record theoretical and empirical studies suggest that sea level change was a fundamental parameter determining the distribution of fossil marine organisms although a similar relationship is generally assumed for the continental fossil record this intuition remains speculative quantitative evidence reveals no correlation between sea level variations and the distribution of continental tetrapods in the late jurassic eocene interval the quality of the continental fossil record depends on many more factors than just eustatic changes

evidence for taphonomic size bias in the dinosaur park formation campanian alberta a model mesozoic terrestrial alluvial paralic system a study of the distribution of dinosaurian body masses in the dinosaur park formation dpf campanian southern alberta reveals a prominent negative skew a pattern distinct from those of modern terrestrial faunas we find a direct and robust correlation between taxon size estimated live body mass and known completeness there is a clear dichotomy between large and small bodied taxa at around 60 kg in which taxa less than 60 kg are significantly less complete mean completeness 7 6 than those with an estimated mass of 60 kg or greater mean 78 2 along with completeness there is also a strong association of body size and taphonomic mode with small taxa known largely from isolated and occasionally associated remains and large taxa known from articulated skeletons in addition there is a significant correlation between taxon body mass and both date of discovery and of description with taxa 60 kg the rates of both cumulative discovery and description for large taxa are best described by a logarithmic curve nearing an asymptote whereas small taxa show either a linear or power increase through time this suggests that our current knowledge of the large bodied dinosaur assemblage is reasonably representative of the true biological fauna with few discoveries likely to be made in the future however small taxa are greatly underestimated in both their diversity and abundance with many more potential discoveries to be made given that 1 the sedimentary deposits and fossil assemblages in the dpf together represent one of the best studied examples of a mesozoic alluvial paralic terrestrial palaeoecosystem and 2 similar patterns have been suggested but not documented for other mesozoic terrestrial ecosystems in the western interior of north america we suggest that this pattern of size bias may typify vertebrate fossil assemblages in terrestrial mesozoic systems if so such biases must be considered before patterns of diversity in dinosaur communities through time can be considered accurate or used to compare and interpret mesozoic palaeoecosystems