mineralogical evidence for eolian contribution to soils of late quaternary moraines wind river mountains wyoming usa abstract volcanic heavy minerals are found in the a and b horizons of soils on moraines of the western wind river mountains of wyoming volcanic minerals do not occur in the underlying moraine sediments derived from plutonic and metamorphic bedrock sources of the volcanics are the sedimentary rocks of the green river basin the presence of volcanic minerals in the green river basin and their patterns of distribution in the moraine soils indicate eolian sedimentation is an important factor of soil genesis in this region moraines affected by eolian sediments include the pinedale and temple lake indian basin type localities the presence of eolian sediments in both pinedale and holocene deposits suggests eolian addition is not simply a late glacial phenomenon but continues throughout postglacial time relations between eolian sediments and soil development must be accounted for when comparing soil development on moraine chronosequences in this and possibly all alpine regions of western north america

properties of modern dust accumulating in the uinta mountains utah usa and implications for the regional dust system of the rocky mountains a growing body of work is illuminating the importance of dust as a component of soil development and biogeochemical cycling in alpine environments of the rocky mountains nonetheless important questions remain about the dust system in this region due to a paucity of focused studies and direct measurements this project involved deployment of modified marble dust traps in the alpine zone of the uinta mountains of utah to trap modern atmospheric dust over a two year period results indicate that dust accumulation rates are similar to values previously reported for the wind river range of wyoming but less than values for south western colorado suggesting a south to north decrease in regional dust flux the overall mean grain size of uinta dust is similar to values reported by prior studies in colorado indicating a general uniformity in grain size distribution uinta dust is dominated by quartz plagioclase k feldspar and illite with trace amounts of kaolinite chlorite and amphibole in contrast only quartz and k feldspar are present in the uinta bedrock confirming an exotic origin for the dust arriving in the alpine zone exotic mineralogies have also been reported in dust from other mountain ranges in the western united states indicating that eolian delivery of allochthonous minerals is a widespread process geochemical analysis reveals that bi na p zn sn cu cd ba ni w sb pb and tl in uinta dust are elevated 10 to 80 times above their abundances in local bedrock these results support reports of anthropogenic elemental enrichment in lake sediments from colorado and utah patterns of elemental loading suggest that certain elements are delivered by winds arriving from different directions raising the possibility that some elements could be associated with unique source areas copyright 2014 john wiley sons ltd

size variation of conodonts during the smithian spathian early triassic global warming event the early triassic smithian spathian boundary ssb crisis coincided with an episode of extreme warmth a high resolution stratigraphic framework comprising six conodont zones is provided in the jiarong section nanpanjiang basin in south china detailed size measurements of 441 conodont elements of the closely related genera neospathodus triassospathodus and novispathodus show for the first time that this clade suffered a temporary but significant size reduction during the ssb crisis the size reduction of conodonts was probably caused by an episode of global warming

u pb zircon chronology geochemistry and isotopes of the changyi banded iron formation in the eastern shandong province constraints on bif genesis and implications for paleoproterozoic tectonic evolution of the north china craton abstract the changyi banded iron formation bif in the eastern north china craton ncc occurs within the paleoproterozoic fenzishan group the bif shows alternating quartz rich light and magnetite rich dark bands with magnetite 15 65 vol quartz 25 65 vol and amphibole 15 30 vol constituting the major minerals minor garnet epidote chlorite calcite biotite and pyrite occur locally the bif bands are interlayered with amphibolite hornblende gneiss biotite quartz schist garnet biotite schist biotite gneiss and leptynite and are intruded by granites la icp ms u pb dating on zircons separated from the bif bands and the wallrocks constrains the depositional age as 2240 2193 ma and metamorphic age as 1864 ma the dominant composition of sio 2 fe 2 o 3 t average value of 92 3 wt of the bif bands suggests their formation mainly through chemical precipitation however the widely varying contents of major elements such as al 2 o 3 0 58 6 99 wt mgo 1 00 3 86 wt cao 0 22 4 19 wt and trace elements such as rb 2 06 40 4 ppm sr 9 36 42 5 ppm zr 0 91 23 6 ppm hf 0 04 0 75 ppm cr 89 1 341 ppm co 2 94 30 4 ppm and ni 1 43 52 0 ppm clearly indicate the incorporation of clastics especially continental felsic clastics as also confirmed by the presence of ancient detrital zircons in the bif bands when normalized against post archean average shale paas the seawater like signatures of ree distribution patterns such as lree depletion positive la and y anomalies and superchondritic y ho ratios average value of 36 3 support the deposition in seawater strong positive eu anomalies eu eu paas 1 14 2 86 also suggest the participation of hydrothermal fluids in addition the sympathetic correlation between cr co and ni as well as the co ni cu vs ree and the al 2 o 3 vs sio 2 relations further indicates that the iron and silica mainly originated from hydrothermal fluids combined with regional geological investigation and protolith restoration of the wallrocks a continental rift environment is suggested for the changyi bif deposition the appearance of negative ce paas anomalies might suggest the influence of the great oxidation event at the time of deposition the changyi bif witnessed the major paleoproterozoic rifting collision events in the ncc and their unique distribution in the ncc contrasts with other examples elsewhere in the world

the triassic isotope record a variety of stable isotope measurements have been found useful in studying processes of environmental change measurements of d 13 c d 18 o d 34 s and 87 sr 86 sr all can provide infor mation about the conditions of the water column in which sediment deposition occurred but the most widely applied of these is d 13 c the carbon isotope record for the triassic system is a complex one a pronounced negative excursion begins below the base of the triassic system and continues into the basal triassic the succeeding 4 to 6 ma lower triassic interval is marked by isotopic instability with positive and negative excursions continuing through the basal middle triassic in contrast to the lower triassic most of the middle and upper triassic display relative isotopic stability with rising values of d 13 c likely reflecting environmental recov ery and increasing storage of organic carbon in terrestrial environments the uppermost triassic is marked by a pronounced negative excursion near the system boundary that has been linked to significant biotic turnover the causes of the various excursions remain under investigation particularly those at the system boundaries with outgassing during volcanic activity changes in productivity ocean anoxia and seafloor methane releases all suggested as mechanisms both for perturbing the global carbon cycle and for forcing biotic extinction

soil development along an elevational gradient in the southeastern uinta mountains utah usa abstract a silt mantle enriched in ca is important in buffering soils on quartzitic terrane in the southeastern uinta mountains we examined 32 pedons along an elevational gradient on the south slope of the eastern uintas to determine the amount of the silt and its importance to pedogenesis the pedons were in the upper montane forest 2700 3000 m subalpine forest 3000 3400 m and alpine tundra 3400 3850 m on stable sites there were no significant differences in silt cap thickness or in profile quantities of silt upper 100 cm by ecoclimatic zone similar soils were found in all three ecoclimatic zones including eutrocryepts dystrocryepts haplocryalfs cryorthents and haplocryolls in descending order of abundance profile quantities of clay exchangeable cations and extractable al and solum thickness are greatest in the alpine zone probably because the soils there are older than those at lower elevations and soil formation proceeds more rapidly base cycling is enhanced in alpine communities dominated by acomastylis geum rossii as evidenced by large profile quantities and high tissue concentrations of ca profile quantities of total n and organic c are significantly greater p 0 05 in the alpine zone reflecting greater below ground production and lower rates of organic matter turnover than in soils at lower elevations

transient global cooling at the onset of early aptian oceanic anoxic event oae 1a the onset of the early aptian oceanic anoxic event oae 1a ca 120 ma coincided with a major perturbation of the carbon cycle which is reflected in the sedimentary carbon isotope record triggering mechanisms duration and climatic repercussions of this episode of accelerated organic matter burial remain poorly constrained here we present millennial scale bulk rock carbon and oxygen isotope data from a marly subtropical intrashelf basin la bedoule southeast france with unusually high sedimentation rates which track the onset of oae1a in unprecedented resolution our record reveals that the negative low amplitude delta 13 c excursion preceding oae1a lasted 100 k y implying that enhanced volcanic co 2 emission and or pulsed methane dissociation over a prolonged time span were instrumental in triggering oae1a the main positive carbon isotope shift at the onset of oae1a previously regarded as continuous occurred stepwise over an extended period of 300 k y transient climate cooling during the initial delta 13 c increase probably reflects ephemeral high latitude glaciation triggered by changes in radiative forcing and drawdown of atmospheric co 2

a lacustrine sedimentary record of holocene periglacial activity from the uinta mountains utah u s a abstract a lake sediment core from the uinta mountains of northern utah was analyzed to constrain the timing of late holocene periglacial activity records of numerous physical properties were converted to time series spanning the past 5300 years using a depth age model based on four ams 14 c dates long term decreases in organic content and increases in bulk density attest to increasing inputs of clastic sediment abundance of mineral p signaling physical bedrock weathering reaches maximum values ca 2900 2150 and 1400 cal yr bp coincident with finer median grain size and a shift toward darker red sediment these peaks interpreted as signals of periglacial activity align with pulses of rock glacier activity in colorado determined from lichenometry the youngest peak coincides with lichenometric ages previously determined for periglacial deposits upstream from the lake a pulse of renewed periglacial activity ca 400 cal yr bp represents the little ice age the late 20th century witnessed extremely high values of organic matter and biogenic silica and unprecedented low values of c n reflecting greatly enhanced in lake productivity likely due to disturbance in the watershed

end permian mass extinction in the oceans an ancient analog for the twenty first century the greatest loss of biodiversity in the history of animal life occurred at the end of the permian period 252 million years ago this biotic catastrophe coincided with an interval of widespread ocean anoxia and the eruption of one of earth s largest continental flood basalt provinces the siberian traps volatile release from basaltic magma and sedimentary strata during emplacement of the siberian traps can account for most end permian paleontological and geochemical observations climate change and perhaps destruction of the ozone layer can explain extinctions on land whereas changes in ocean oxygen levels co2 ph and temperature can account for extinction selectivity across marine animals these emerging insights from geology geochemistry and paleobiology suggest that the end permian extinction may serve as an important ancient analog for twenty first century oceans

record of the end permian extinction and triassic biotic recovery in the chongzuo pingguo platform southern nanpanjiang basin guangxi south china abstract the chongzuo pingguo platform is a vast isolated platform 180 km across in the southern part of the nanpanjiang basin the end permian extinction is recorded in conformable sections in the northern part of the platform pingguo area upper permian skeletal packstone contains diverse open marine fossils including nankinella and sphaerulina it is overlain by a 4 6 m thick horizon of calcimicrobial framestone constructed by globular calcified microbial framework similar to renalcis the ptb event horizon is interpreted to occur at the top of the packstone coincident with the abrupt change to calcimicrobial framestone lacking permian macrofossils the transition from hindeodus latidentatus to h parvus occurs 1 m above the base of the calcimicrobial framestone marking the conformable biostratigraphic boundary during the early triassic the platform developed as a low relief bank rimmed with oolite shoals but was bordered by a high relief fault controlled escarpment along its southern margin platform interior facies of the majiaoling and beisi formations are 900 m thick and consist of thin bedded lime mudstone oolite and dolostone with restricted marine biota in four shallowing upward packages that define depositional sequences in the chongzuo area the platform was terminated at the end of the early triassic by burial with up to 1600 m of felsic pyroclastic volcanics and lava flows transgression and shallow marine carbonate sedimentation resumed early in the middle triassic followed by drowning in the bithynian as indicated by a shift to deep marine carbonate and clastic deposition in the pingguo area volcanic deposits are much thinner and only briefly interrupted carbonate accumulation here the platform interior drowned during a major back step early in the middle triassic anisian bithynian smaller pinnacle platforms of the guohua fm up to 1700 m thick continued to accumulate above the early triassic platform margin and were eventually drowned by the late pelsonian in the anisian the pinnacle platforms shifted to sharply defined reef rimmed margins with tubiphytes reefs the shift coincides with accelerated metazoan biotic recovery in the anisian however the reefs lack metazoan frameworks and are composed almost entirely of tubiphytes reinforced by large volumes of marine cement these observations indicate that controls beyond the recovery of framework building metazoans governed the re establishment platform margin reefs in the middle triassic

evidence for recurrent changes in lower triassic oceanic circulation of the tethys the δ13c record from marine sections in iran abstract stable carbon isotope curves derived from lower triassic carbonate rocks from three iranian sections are established to investigate changes in the carbon cycle during the early triassic in this area the sections are located in the south center abadeh north amol and northwest zal of iran all three curves show a similar pattern starting out with high 13 c values in the uppermost permian decreasing across the permian triassic boundary an increase toward more positive values during the griesbachian that slowly increase further up during the dienerian followed by a positive excursion to values as high as 8 near the dienerian smithian boundary during the smithian values return to below 0 whereas second positive excursion to values higher than 3 is recorded at the smithian spathian boundary again followed by a drop in 13 c into the spathian and a final excursion to positive values at the spathian anisian boundary the results from these iranian sections are consistent with previous studies from italy and china thus strongly suggesting that the recorded 13 c variability represents at least tethys wide geochemical signals moreover the new curves reveal evidence of high amplitude frequent oscillations pointing toward rapid and profound changes in the global carbon cycle during the lower triassic stratification of the ocean interrupted by episodic overturning transporting deep water to the ocean surface is a viable mechanism to account for the recorded isotope variations provided that the 13 c curve is representative of the global lower triassic ocean it has high potential for accurately dating sedimentary successions via chemostratigraphy

litho bio and chemostratigraphy across the cenomanian turonian boundary oae 2 in the vocontian basin of southeastern france the oceanic anoxic event 2 oae 2 was one of at least two large oceanic anoxic events during the cretaceous period and it is characterized in the stratigraphic record by double positive peaks in the 13c curves of carbonate and organic carbon since the positive 13c shift is believed to have resulted from massive burial of isotopically depleted organic carbon generated globally in anoxic oceanic environments the positive 13c shift tend to coincide with widespread deposition of organic rich sediments in the case of oae 2 however the organic rich horizons do not accord exactly with the two intervals with positive 13c shifts at many sites such as pueblo tarfaya eastbourne and gubbio e g tsikos h jenkyns h c walsworth bell b petrizzo m r forster a kolonic s erba e premoli silva i baas m wagner t sinninghe dameste j s 2004 carbon isotope stratigraphy recorded by the cenomanian turonian oceanic anoxic event correlation and implications based on three key localities journal of the geological society london 161 711 719 the thomel level of the cenomanian turonian c t boundary in the vocontian basin southeastern france accumulated during the oae 2 and it is marked by frequent intercalations of black shale and organic rich marl detailed litho bio and chemostratigraphy analyses across the c t boundary in the vocontian basin indicate that the 13ccarbonate profile fluctuation across the thomel level corresponds well with changes in lithofacies total organic carbon toc and calcium carbonate caco3 abundance positive 13c excursions within the oae 2 correlate with basal and middle parts of the thomel level that are characterized by high toc low caco3 and predominantly contain organic rich sediments such as black shale and dark gray marl on the other hand negative 13c intervals within the oae 2 correspond with lower and upper parts of the thomel level that consist of marly limestone and limy marl with low toc and high caco3 values since the fluctuation of redox conditions during thomel level deposition in the vocontian basin coincides well with the global carbon burial rate indicated by its 13c profile the thomel level could be an ideal candidate for the reference section of the oae 2

carbon isotopic excursions and detailed ammonoid and conodont biostratigraphies around smithian spathian boundary in the bac thuy formation vietnam abstract the smithian spathian boundary is indicated by the first occurrence of the ammonoid tirolites cf cassianus in the olenekian bac thuy formation northeastern vietnam the boundary is intercalated within organic rich dark gray mudstone that accumulated under anoxic to dysoxic conditions in the an chau and nanpanjiang basins on the south china block in lang son area three conodont zones novispathodus ex gr waageni novispathodus ex gr pingdingshanensis and icriospathodus collinsoni are recognized in the formation the smithian spathian boundary is intercalated within n ex gr pingdingshanensis conodont zone the positive excursion in 13c with values increasing from around 2 3 to 5 7 was recorded in the uppermost smithian xenoceltites variocostatus ammonoid beds and n ex gr pingdingshanensis conodont zone the 13c values decrease across the smithian spathian boundary these 13c isotopic patterns are correlated with well known positive excursions around the smithian spathian boundary globally

conodont diversity and evolution through the latest permian and early triassic upheavals abstract a study of latest permian and early triassic multielement conodonts identifies eight steps in their evolutionary history during an interval when earth s biosphere was highly stressed these steps are 1 gradual decline of families and genera through the changhsingian up to the late griesbachian 2 conodont biofacies change and extinction of tethyan endemic species close to the permian triassic boundary ptb 3 faunal turnover with extinction and origination in the late griesbachian 4 initial radiation in gondolellids and diversification in apparatuses during the dienerian 5 explosive radiation in the early middle smithian 6 major extinction in the late smithian 7 major radiation early in the spathian 8 gradual turnover and decline in the late spathian through early anisian conodontophorids were reduced from five families at the beginning of the changhsingian to three by the ptb and to two late in the griesbachian from the changhsingian to the late griesbachian there was a single multielement apparatus represented in the gondolellidae whereas by the olenekian there were at least twelve given absolute age constraints the conodont recovery in the aftermath of the ptb was extraordinary conodont evolution during the dienerian remains obscure but was very significant in terms of changes in multielement apparatuses in spite of induan extinctions generic diversity generally increased from the ptb up to the late smithian in terms of species genera and multielement apparatuses the acme of triassic conodonts was in the middle smithian and the biggest extinction was in the late smithian after this extinction generic and apparatus diversity quickly returned to high levels marking a significant spathian recovery gradual decline characterized the late spathian and persisted into the early anisian a synthetic summary of the temporal distribution and proposed relationships amongst all known lower triassic conodonts provide an improved foundation for biostratigraphic and biochronologic studies extinction and radiation trends correlate well with sea level changes and sequence boundaries faunal turnovers correspond to lowstands in the late griesbachian late smithian and late spathian and radiations correspond to transgressions in the early griesbachian early smithian and early spathian the trends also correlate with perturbations in the carbon cycle with lower triassic 13c minima corresponding to extinction and faunal turnover and positive values generally occurring during radiations however middle triassic recovery of marine benthos follows a positive maxima and an overall decline in conodont diversity new taxa borinella chowadensis b megacuspa neogondolella griesbachensis and n mongeri are described

eolian deposition in the alpine zone of the uinta mountains utah usa abstract field and laboratory investigations were conducted to determine the origin of a ubiquitous layer of silt that caps soil profiles in the alpine zone of the uinta mountains utah usa fine sediment isolated from snowbanks was studied to constrain the fraction of this material derived from allochthonous eolian additions lake sediments representing deposition over the past few centuries were analyzed to determine whether dust deposition in the uintas has been a long term process and if properties of the modern dust differ from dust which accumulated prior to european settlement results indicate that alpine soils have been strongly influenced by long term eolian deposition the loess cap in these soil profiles averages 18 cm thick and physical and chemical properties of soil horizons derived from the eolian parent material are significantly different than those of the subsurface horizons derived from in situ produced congelifractate fine sediment observed at the surface of snowbanks in the early summer is a mixture of silty exotic eolian material and sandy locally derived sediment snowbanks on ridgecrests and on slopes of blocky scree tend to accumulate the maximum amount of exotic dust with the minimum amount of local material the grain size distribution mineralogy and geochemistry of lake sediments indicate that dust has been accumulating in the uintas for at least the last few centuries modern lake sediments are significantly enriched in elements indicative of upwind mining and agricultural activity recording an anthropogenic change in dust composition following settlement of the surrounding lowland basins

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

origin of glossic horizons in cryalfs of the eastern rocky mountains usa abstract cryalfs are the predominant suborder along the eastern front of the rocky mountains from northern nm through mt and into alberta approximately 50 of the cryalfs in the western usa contain a glossic horizon defined as a degraded argillic horizon containing properties of both an e and a bt horizon using the nrcs database we examined 257 cryalf soil series 79 of which contain a glossic horizon the glossic horizon occurs at an average depth of 32 cm and averages 24 cm thick the glossic horizon is most commonly an e bt with textures similar to the e above and bt below waxy or glossy argillans are common as well as clay enriched nodules and seams laboratory data are available for only 10 cryalf pedons containing a glossic horizon based on these data the glossic horizon contains an average of 24 clay 1 0 clay cec7 0 6 organic c a cation exchange capacity of 19 cmolc kg soil 85 base saturation and a ph of 5 6 several theories for the origin of the glossic horizon were considered from a weight of evidence approach the glossic horizon in cryalfs of the rocky mountains may be attributed to an input of eolian silt which creates a lithologic discontinuity and a mid holocene 5000 yr bp to present lowering of treeline containing the strongly podzolizing species picea engelmannii and abies lasiocarpa although glossic horizons are common in upper montane soils now containing lodgepole pine pinus contorta they are uncommon in lower montane soils supporting lodgepole and ponderosa pinus ponderosa pines

weak influences of climate and mineral supply rates on chemical erosion rates measurements along two altitudinal transects in the idaho batholith 1 chemical weathering promotes regolith production physical erosion nutrient supply and drawdown of atmospheric co2 although mineral dissolution rates show dependences on temperature and moisture in theoretical models and laboratory experiments effects of climate on chemical erosion rates in nature remain uncertain in part because variations in physical erosion rates and lithology can obscure climatic signals in chemical erosion rate measurements here we present new estimates of millennial scale chemical and physical erosion rates along two altitudinal transects in the idaho batholith our measurements suggest that chemical erosion rates and the extent of regolith chemical alteration are insensitive to mean annual regolith temperature even though the study sites span a wide range in temperatures 4 8 c 10 9 c these data also suggest that rates of chemical erosion and the extent of regolith chemical alteration are weakly correlated with the annual duration of high regolith moisture conditions lastly our measurements show that the sampled regoliths tend to grow more chemically weathered with increasing regolith residence time implying that weathering at these sites is primarily limited by mineral dissolution kinetics rather than mineral supply rates to the regolith the lack of strong control by mineral supply means that chemical erosion rates at these sites could potentially vary in response to climatic factors such climatically driven variation in chemical erosion rates is not obvious in our data however instead our measurements suggest that chemical erosion rates at these sites are insensitive to mean annual regolith temperature and only weakly dependent on the length of the wet season

parent material and chemical weathering in alpine soils on mt mansfield vermont usa we compared the elemental composition of soil and bedrock samples to determine the extent of chemical weathering and the nature of the soil parent material in alpine soils on vermont s highest summit previously it was unclear whether these soils formed through weathering of bedrock glacial till or eolian sediment or solely through the accumulation of organic matter in eighteen profiles no evidence was found to indicate that soils have developed in glacial till despite evidence that the mountain was completely inundated by the laurentide ice sheet in contrast results strongly support the theory that pedogenesis in this environment involves in situ bedrock weathering under a thickening blanket of acidic organic litter weathering indices reveal an increase in weathering intensity upwards from the bedrock and trends of normalized rare earth elements demonstrate a strong similarity between bedrock and soil samples leaching has concentrated less mobile elements such as al cr la p pb and ti in soil horizons and removed mobile elements such as co fe k mg mn si and zn x ray diffraction reveals that chlorite which is present in all bedrock samples and some saprolites has weathered completely from upper soil horizons and that hydrobiotite vermiculite kaolinite gibbsite and goethite have formed in the soil ratios of immobile elements ce cr nb ta ti y and zr in soil and bedrock samples are however notably different furthermore the moderately mobile trace elements cu mo and sr are actually more abundant in soil than in bedrock and soil concentrations of zr are up to an order of magnitude greater than in bedrock samples together these data argue for at least a modest eolian influx which may have arrived during the regression of lake vermont during the latest pleistocene or from an outwash source in the immediate post glacial period similarly increased ca and na concentrations in soil samples may signify modern deposition of dust bearing ca from agricultural fields and na from roads

lower triassic conodont sequence in chaohu anhui province china and its global correlation abstract the early triassic paleogeographical setting of the chaohu section in china was in a deep part of the yangtze platform and this has resulted in a rather complete lower triassic sequence with rich ammonoid and conodont successions three lower triassic sections west pingdingshan north pingdingshan and south majiashan have been sampled in detail for a systematic conodont study eight conodont zones are recognized in ascending order these are the zones of hindeodus typicalis neogondolella krystyni neospathodus kummeli neospathodus dieneri neospathodus waageni neospathodus pingdingshanensis neospathodus homeri and neospathodus anhuinensis these are correlated with the sequences in north america and other areas of the world the succession provides a good basis for the definition of the global stratotype of the induan olenekian boundary gssp which has been proposed at the base of the neospathodus waageni zone in west pingdingshan seven new species are introduced neospathodus chaohuensis n chii n concavus n eotriangularis n pingdingshanensis n posterolongatus n tongi a new subspecies n waageni eowaageni and three morphotypes of n dieneri

the role of climate and vegetation in weathering and clay mineral formation in late quaternary soils of the swiss and italian alps nteractions between climate and soil remain ambiguous particularly when silicate weathering and clay mineral formation and transformation rates are considered in relation to global climate changes recent studies suggest that climate affects weathering rates much less than previously thought here we show that the climate in the central european alps has a significant but indirect influence on the weathering of soils through vegetation the pattern of element leaching and mineral transformations is not only due to precipitation and temperature element leaching was greatest in subalpine forests near the timberline weathering is lessened at higher and lower altitudes vegetation therefore contributes significantly to weathering processes the highest accumulation of organic matter was found in climatically cooler sites subalpine range where the production of organic ligands which enhance weathering is greatest patterns of smectite formation and distribution had strong similarities to that of the elemental losses of fe and al r 0 69 p 0 01 or base cations r 0 58 p 0 05 higher precipitation rates and the production of organic chelating compounds in the soil promoted the appearance of smectites the relationship between climate element leaching fe al ca mg k na and smectite formation is strongly nonlinear and driven by the podzolisation process which is more pronounced near the timberline because of the bioclimatic constellation climate warming will probably in the future lead to a decrease in som stocks in the subalpine to alpine range because of more favourable conditions for biodegradation that would also affect weathering processes

reconstruction of early triassic ocean redox conditions based on framboidal pyrite from the nanpanjiang basin south china abstract widespread oceanic anoxia has been implicated as an important factor in the ptb permian triassic boundary mass extinction and the delayed recovery of early triassic marine ecosystems an investigation of framboidal pyrite in the bianyang section nanpanjiang basin south china suggests that euxinia dysoxia peaked during the induan late smithian to earliest spathian and late spathian these anoxic episodes show a relationship albeit imperfect to major episodes of climatic warming during the early triassic that were associated with intensified oceanic stratification reduced marine productivity and organic carbon sinking fluxes as well as diminished burial fluxes of organic carbon and reduced sulfur in contrast intervals of better oxygenated marine conditions were associated with episodes of relative climatic cooling during the early to middle smithian and mid spathian the degree of ventilation of the thermocline region in particular had a profound effect on marine biotas with intervals of improved ventilation resulting in increased global diversity among ammonoids and conodonts and increased local abundance of foraminifera in the nanpanjiang basin these observations suggest that oceanic redox fluctuations played an important role in the delayed recovery of early triassic marine ecosystems and specifically that episodic expansion of oceanic oxygen minimum zones omzs resulted in repeated setbacks to the recovery process a pattern that persisted until the late spathian

smithian spathian boundary event evidence for global climatic change in the wake of the end permian biotic crisis one of the most important carbon cycle perturbations following the end permian mass extinction event straddles the smithian spathian boundary ssb olenekian early triassic this anomaly is characterized by a prominent positive carbon isotope excursion known from tethyan marine rocks its global signifi cance is established here by a new high paleolatitude record spitsbergen paleontological evidence such as boreal palynological data barents sea norway and global patterns of ammonoid distribution indicates a synchronous major change in terrestrial and marine ecosystems near the ssb the reestablishment of highly diverse plant ecosystems including the rise of woody gymnosperms and decline of the formerly dominating lycopods is interpreted as an effect of a major climate change this hypothesis is supported by modeling of ammonoid paleobiogeography the distribution patterns of which are interpreted as a proxy for sea surface temperatures sst the latest smithian thus appears to have been a time of a warm and equable climate as expressed by an almost fl at pole to equator sst gradient in contrast the steep spathian sst gradient suggests latitudinally differentiated climatic conditions we propose that this drastic climate change and the global carbon cycle perturbation were triggered by a massive end smithian co2 injection the ssb event could therefore represent one of the causes for stepwise and delayed recovery of marine and terrestrial biotas in the wake of the end permian biotic crisis

weathering mineralogical evolution and soil organic matter along a holocene soil toposequence developed on carbonate rich materials a toposequence of holocene soils located between 1100 2400 m asl in the italian alps served as the basis for the following analyses the weathering of limestone and dolomite the calculation of mass balances understanding the formation of pedogenic fe and al the determination of soil mineral and clay mineral reactions and transformation and the measurement of accumulation and stabilisation mechanisms of soil organic matter leaching of carbonates is most intense at the lower elevations although calcite and dolomite have a higher solubility at low temperatures the pco2 in the soil is higher at lower elevations and weathering is driven mainly by carbonic acids at higher elevations organic acids appear to determine the mineral transformations and weathering reactions to a greater extent this suggests that two very different weathering regimes carbonic and organic acid weathering exist along the toposequence the transformation of mica into vermiculite is the main process in both the clay and fine earth fraction weathering of silicate minerals started even before the carbonates had been completely removed from the soils the transformation mechanisms of silicate minerals in the a and o horizon at higher elevations was at least as intensive as that at the climatically warmer sites the neoformation of pedogenetic clays at climatically cooler sites was slightly greater than that at the warmer sites however the formation rate of secondary fe and al phases was more pronounced at lower elevation which means that this process seemed to be driven dominantly by carbonic acid weathering of primary minerals soil organic matter som abundance in the mineral soil is nearly 15 kg m2 at all sites and surprisingly no climate driven effect could be detected in general the preservation and stabilisation of som was due to poorly crystalline al and fe phases and vermiculite regardless of some variations in the composition of the parent material varying calcite dolomite ratio

high amplitude redox changes in the late early triassic of south china and the smithian spathian extinction abstract the early triassic was a time of remarkably high temperatures large carbon cycle perturbations and episodes of widespread ocean anoxia the sediments in the nanpanjiang basin of south china provide superb opportunities to examine the sedimentary response to these extreme conditions especially during the crisis interval at the smithian spathian s s boundary we have investigated a deep water section at jiarong and a shallower water section at mingtang these contain a range of facies including black shales micritic limestone units and rudaceous carbonate event beds that include flat pebble conglomerates and breccia debrites that bear similarities to the hybrid event beds seen in clastic turbidite successions redox proxies pyrite framboids and trace metals reveal that widespread anoxia in the late smithian persisted into the novispathodus pingdingshanensis zone of the early spathian before a sharp transition to highly oxygenated griotte facies red marine strata in the icriospathodus collinsoni zone that records an oxic rebound benthic faunas are locally common but of low diversity and dominated by thin shelled bivalves and ostracodes with small foraminifers and exceptionally rare fish remains bioturbation was intense only in the early middle spathian i collinsoni conodont zone griotte facies anoxia and extremely high temperatures probably played a role in severely restricting the abundance of fish and the small sizes of marine invertebrates at this time the presence of ooids and seafloor fan cements in our study sections indicates highly saturated conditions rather than acidification at the end of the smithian

terrestrial marine teleconnections in the collapse and rebuilding of early triassic marine ecosystems abstract the latest permian mass extinction lpe just prior to the permian triassic boundary at 252 ma resulted in the disappearance of 90 of skeletonized marine taxa and the replacement of the paleozoic fauna by the modern fauna in the immediate aftermath of the extinction shallow marine ecosystems were dominated by microbial communities and diminutive disaster taxa lilliput faunas and the post crisis period in general was characterized by high abundance low diversity marine communities occupying a reduced ecological space the recovery of marine ecosystems was a protracted process lasting throughout the 5 myr long early triassic some clades failed to recover and subsequently went extinct dead clades walking while others recovered only to suffer secondary crises during the early triassic profound environmental changes accompanied these biotic developments deep oceans experienced sustained hypoxia or anoxia for at least several million years following the boundary event anoxia was also widespread in shallow marine areas especially at the time of the lpe but it was more episodic and abated more rapidly than in the deep ocean making it an unlikely factor in the delayed recovery of early triassic marine ecosystems the development of anoxia was due at least in part to a sharp temperature rise following the lpe but may have been stimulated by changes in marine nutrient inventories and productivity rates as well these conditions may have been the result of a concurrent increase in subaerial weathering rates that was sustained into the early triassic in addition to increasing nutrient fluxes to marine areas rapid weathering caused a massive influx of sediment to shallow marine systems subjecting marine biotas to siltation stress this scenario implies close teleconnections between terrestrial and marine environments during the permian triassic boundary crisis with perturbations of the terrestrial realm contributing to the marine crisis

effects of slope orientation on pedogenesis of altimontane soils from the brazilian semi arid region baturite massif ceara given the importance of climate conditions for the development of soils studies on climosequences are a valuable tool to predict the influence of climate change on weathering rates and on soil formation processes the baturite massif a humid enclave located in the brazilian semi arid region has unique characteristics that cause a disproportional distribution of rainfall the eastern and northern slopes receive more than 1 600 mm year of rainfall whereas the southern and western slopes have semi arid characteristics with rainfall of less than 600 mm year eight soil profiles were selected to investigate the influence of these distinct climates on soil formation to achieve this physical chemical morphological mineralogical and micromorphological data were determined and analyzed in the humid slope predominate soil processes include melanization brunification intense leaching acidification and alitization with intensified weathering in higher altitudes in contrast the environment in the dry slope favored the occurrence of soils with a higher base status high activity clays low al saturation and bisialitization processes coexisting with monosialitization mainly in the soils located at lower altitudes micromorphological data indicate that clay illuviation is not the main process responsible for the enrichment of clay in the subsurface horizons the contrasting environmental conditions with different mineralogical composition seem to be an important indicator of weathering intensity and pedoenvironmental conditions

weathering rates as a function of climate results from a climosequence of the val genova trentino italian alps a soil sequence in northern italy along an elevational gradient ranging from moderate 950 m a s l to high alpine 2440 m a s l climate zones was investigated with respect to element losses ca mg k na fe al si mn and the development of clay minerals element losses were derived from mass balance calculations that are based on enrichment depletion factors using immobile element contents ti mass balance calculations indicated that extensive mineral weathering resulted in significant leaching losses of major base cations with losses up to 80 of the initial content in the parent material al particularly from upper horizons and si element denudation was greatest in subalpine forests near the timberline weathering rates decreased with both higher and lower altitudes the pattern of smectite distribution along the climosequence has strong similarities to the al si na and k losses while an inverse trend could be detected for clay minerals with a high amount of interlayered al highest smectite contents with up to 30 of the clay fraction and also highest weathering rates were found at sites in subalpine forest near the timberline higher precipitation rates and the production of chelating compounds in the soil are believed to promote the appearance of smectites weathering rates of na and k were additionally modelled as a function of precipitation and temperature the relationship between climate and element weathering is strongly nonlinear and is thought to be overshadowed by the pronounced podzolisation effect near the timberline

triassic ammonoid biostratigraphy an overview abstract the triassic chronostratigraphic scale was built on two centuries of research on ammonoid biostratigraphy and biochronology two triassic stage bases and all of the triassic substages are currently defined by ammonoid bioevents the study of triassic ammonoids began during the late 1700s and in 1895 edmund von mojsisovics wilhelm waagen and carl diener published an essentially complete triassic chronostratigraphic scale based on ammonoid biostratigraphy this scale introduced many of the triassic stage and substage names still used today and all terminology of stages and substages subsequently introduced has been based on ammonoid biostratigraphy early triassic ammonoids show a trend from cosmopolitanism induan to latitudinal differentiation olenekian and the four lower triassic substage griesbachian dinerian smithian and spathian boundaries are globally correlated by widespread ammonoid biotic events middle triassic ammonoids have provinciality similar to that of the olenekian and provide a basis for recognizing six middle triassic substages late triassic ammonoids provide a basis for recognizing three stages divided into five substages the main uncertainty for the future of triassic ammonoid biostratigraphy is not the decline of the ammonoids as a tool for dating and correlation of triassic strata but rather the dramatic decrease in the number of specialists due to the lack of replacement of experienced palaeontologists who started their activity in the 1950s and 1960s

quantifying the contribution of dust to alpine soils in the periglacial zone of the uinta mountains utah usa abstract profiles of alpine soils in the uinta mountains utah usa were investigated to determine how long term dust deposition has influenced soil properties in this environment field studies were focused on four above treeline sites all of which were apparently beyond the reach of erosive glacial ice during the pleistocene modern dust soil a and b horizons and local bedrock were compared in terms of major and trace element geochemistry along with sr and nd isotope compositions in all cases soil samples are a mixture of dust and local bedrock end members with a horizons more closely resembling dust and b horizons more similar to bedrock calculations estimate that these soil profiles contain 50 to 80 dust which is effectively mixed downward into the solum by cryoturbation because these landscape positions were not glaciated the total amount of dust contained within soil profiles is large relative to sites at lower elevation within the glacial limit in addition to altering physical properties of these soil profiles including horizonation and texture deposition of dust rich in base cations positively influences soil fertility

early triassic conodonts of jiarong nanpanjiang basin southern guizhou province south china abstract jiarong huishui county guizhou province south china is a key locality for the study of the early triassic recovery after the end permian mass extinction the size reduction of conodonts at the smithian spathian transition was first documented in jiarong and it is also a locality that contributes to the documentation of the early triassic paleo seawater temperatures in the jiarong sections thirteen conodont zones were identified for the early triassic in ascending order they are hindeodus parvus zone hindeodus sosioensis zone clarkina krystyni zone neoclarkina discreta zone neospathodus cristagalli eurygnathodus costatus assemblage zone novispathodus waageni eowaageni zone novispathodus waageni waageni zone discretella discreta zone pachycladina parachirognathus assemblage zone novispathodus pingdingshanensis zone icriospathodus collinsoni zone triassospathodus homeri zone triassospathodus triangularis zone these conodont zones in the jiarong sections improve the global correlation of early triassic sections and also provide better regional age constraints in an area that is important for studies of recovery from the extinction based on the first appearance of nv waageni eowaageni the induan olenekian boundary is recognized at 3 6 m above the base of the jiarong iii section the dominance of blade shaped segminate conodonts was replaced by gondola shaped segminiplanate conodonts twice the first time was in the late griesbachian and the second time was in the early spathian the dominance of segminiplanate conodonts probably indicates that the deeper seawater environment became more oxygenated during the late griesbachian and early spathian for short time intervals as it is believed that the griesbachian segminiplanate conodonts favored deeper oxygenated water habitats a new genus spathogondolella gen nov and a new species spathogondolella jiarongensis sp nov have been recognized

effect of north and south exposure on weathering rates and clay mineral formation in alpine soils abstract a comparison was made between two soil climosequences on north and south facing slopes in northern italy to determine the influence of slope aspect on soil processes the climosequences span an elevational gradient ranging from moderate 1200 m a s l to high alpine 2420 m a s l climate zones on surfaces having an age of about 15 000 years the soils were investigated with respect to organic c oxalate and dithionite extractable fe al and si elemental losses ca mg k na fe al si mn and clay minerals the stocks of soil org c as well as of oxalate extractable fe and al was greatest in the subalpine zone near the timberline there are no clear differences in organic c content between the soils on north and south facing sites fe oxalate and to a lesser extent alo stocks were however greater on north facing sites indicating that weathering is greater there eluviation and illuviation of al and fe within the soil profile typical for podzolisation was more distinctly expressed on the n slopes the probability of itm imogolite type material formation in the soil seemed to be greater on south facing sites on the north facing sites element leaching was most intense in the subalpine zone close to the timberline while on the south facing sites this was only the case for the base cations the n slopes exhibited higher leaching of elements which generally indicates a higher weathering intensity on south facing sites typical podzolisation processes were measurable only above 2000 m a s l the development of smectites is also a reflection of the weathering intensity smectite was discernible in the surface horizon at all sites on n slopes but the highest amount was detected in the sub alpine climate zone for the south facing sites only in the alpine climate zone could smectite be detected higher temperatures and an increased number of freeze thaw cycles on south facing slopes should theoretically enhance rates of chemical weathering this could however not be confirmed with our measurements the degree of chemical weathering increases from the south to the north facing sites that are characterised by lower temperatures lower evapotranspiration and consequently by a higher humidity although precipitation in alpine regions is abundant the availability and flux of water through the soil is the prime factor in weathering intensity

a new high resolution δ13c record for the early triassic insights from the arabian platform a new carbon isotope record with conodont biostratigraphy is presented for the entire early triassic from the musandam peninsula united arab emirates uae this is a near continuous and exclusively shallow marine carbonate succession that allows analysis of a high resolution primary carbon cycling signature in the absence of significant depth dependent or lithologic controls the musandam carbon isotope record can be broadly correlated with global isotopic events but also resolves additional features including the presence of significant negative events during the previously identified positive excursions at both the dienerian smithian and smithian spathian boundaries a further positive event is revealed during the development of the mid spathian negative excursion a feature not previously reported in any other section these new short lived events are probably related to the occurrence of the more widely recognized early triassic excursions and may represent fluctuations in the driving mechanisms superimposed on the continued instability of the global carbon cycle in the aftermath of the end permian extinction together these features highlight additional complexities to the early triassic carbon cycle perturbations than previously documented

devonian carboniferous transition containing a hangenberg black shale equivalent in the pho han formation on cat ba island northeastern vietnam abstract on cat ba island in northeastern vietnam the devonian to carboniferous d c transition consists mainly of ramp carbonates intercalated with black shale beds beds 1 to 176 in the pho han formation and is one of the few records of the d c transition of the eastern paleotethys the three main facies of the sequence are facies 1 alternations of whitish gray to gray limestone and marl facies 2 calcirudite bed 115b and facies 3 alternations of dark gray limestone and organic carbon rich black shale beds 115c 120 and 126 129 the latest famennian siphonodella praesulcata subzone conodont assemblage of s praesulcata palmatolepis gracilis palmatolepis sigmoidalis and rhodalepis polylophodontiformis was recognized in beds 113 115c beds 105 112 commonly contain palmatolepis expansa p gracilis and p sigmoidalis bed 119 yielded a basal carboniferous index conodont siphonodella sulcata in beds 116 118 solenoporids such as pseudochaetetes elliotti and parachaetetes sp were characteristic species in organic carbon rich dark gray limestone facies 1 is characterized by bioclastic peloidal and intraclastic grainstone and packstone containing massive normal grading and cross laminations and is interpreted to represent deep ramp carbonates above storm wave base facies 2 is represented by typical lag deposits overlying a transgressive surface facies 3 comprises organic carbon rich black shale and minor scour filling bioclastic peloidal and intraclastic packstone and may represent a marginal basin plain environment surrounding a carbonate ramp the alternations of organic carbon rich black shale and dark gray packstone facies 3 show no evidence of bioturbation and have high toc contents 0 18 5 73 wt a minor succession within the transgressive lag deposits from bed 115b of facies 2 to beds 115c 120 in the lower part of facies 3 is equivalent to the hangenberg black shale s l in the middle part of the siphonodella praesulcata to siphonodella sulcata zones because beds 115b 120 characterized by no evidence of bioturbation and high toc contents are interpreted to be accumulated in anoxic to dysoxic conditions

marine triassic faunas of north america their significance for assessing plate and terrane movements the distribution of marine triassic invertebrate faunas in north america is reviewed to recognize forms that may have paleolatitudinal significance

evolution of early triassic outer platform paleoenvironments in the nanpanjiang basin south china and their significance for the biotic recovery detailed microfacies and paleoenvironmental analyses were conducted through the early triassic interval of the outer platform ammonoid rich series of the nanpanjiang basin luolou formation guangxi province south china extensive investigations on outcrops and on thin sections reveal that the widely reported well diversified latest permian fauna dominated by abundant corals calcareous algae calcareous sponges crinoids brachiopods gastropods ostracods and foraminifera is abruptly replaced by decimated early triassic communities essentially composed of low diversity bivalves microgastropods ostracods and rare foraminifera along with this drastic change in faunal assemblages the recolonization of devastated habitats by calcimicrobial frameworks is observed in the aftermath of the end permian mass extinction calcimicrobialites of griesbachian age are followed by mixed ammonoid and conodont rich carbonate siliciclastic series consisting of dark suboxic laminated mudstones intercalated with organic rich shales of dienerian to late smithian age the carbonate siliciclastic series are interrupted by a brief carbonate episode during the early middle smithian massive carbonate production resumes only from the early spathian onward and persists throughout the spathian the initial deposition of both carbonate episodes is coeval with i re establishment of well oxygenated conditions ii a marked early smithian to extreme early spathian ammonoid conodont diversification iii a significant increase in the skeletal grain diversity and abundance and iv peak carbon isotope values a short interval of black organic rich shales precedes the onset of these two distinct carbonate events which are both marked by a positive carbonate carbon isotope excursion known from other tethyan marine localities the comparison between the early triassic stratigraphic evolution of tethyan outer platform paleoenvironments and platform basin margin settings of the nanpanjiang basin suggests a causal connection between large fluctuations of the global carbon cycle climate shifts sea level changes oxygen availability in the oceans and the biological rediversification in the wake of the end permian biotic crisis

climate and vegetation determine soil organic matter status in an alpine inner tropical soil catena in the fan si pan mountain vietnam abstract high mountain ecosystems are generally considered to be particularly sensitive to global climate change studies of pedogenesis associated with altitudinal variation vegetation type and soil carbon content on the same type of parent rock are very limited in inter tropical mountain areas therefore the altitudinal variation of soil pedogenesis through 9 selected profiles from the altitude of 1340 m to 3143 m asl the summit of the fan si pan mountain in the north of vietnam was examined fan si pan mountain is composed of a homogenous alkaline granite rock and is the highest point of the inter tropical continental asia the soil organic matter properties c n 13 c and 15 n contents of the different grain size fractions of the topsoil of 4 selected profiles corresponding to different ecosystems were also examined three zones of different soil forming processes were present acrisols and alisols at lower altitudes in sub montane forest podzols formed in montane and upper montane forest while umbrisols formed at high altitude where the forest vegetation had given way to a shrubby vegetation or a steppe composed of dwarfed bamboo with altitude soils become sandier have higher concentration of sio 2 and are lower in al 2 o 3 the selective fe and al oxalate fe o and al o and pyrophosphate fe p and al p extracts show a clear discrepancy between acrisols or umbrisols with no clear variation with soil depth and podzols with high enrichment in their bs horizon the som status is highly dependent of the organic matter input by the vegetation in acrisols the soc is linked to the fine fraction within the soil profile with rapid turnover and low c n values podzols are formed by the accumulation on soil surface of om enriched in the coarse fraction with depleted 15 n and high c n values the organic matter input is exogenic and probably seasonal from leaves forming the surface litter while in acrisols or umbrisols the soc is mainly linked to the fine fraction and with constant 15 n values at depth in umbrisols the soc origin seems to be linked with endogenic inputs deep in the soil profile mostly produced by the decay of bamboo roots in this tropical mountainous soil catena the soil carbon mineralization depends not only on temperature and organo metallic complexes that stabilize the non labile carbon pool but also is controlled by the pedogenetic process which is linked with the vegetal ecosystem change with altitude

lower middle triassic conodont biostratigraphy of the qingyan section guizhou province southwest china abstract the middle triassic qingyan formation at its type section the qingyan section of guizhou southwest china yields more than 300 species belonging to 17 fossil groups which mark the radiation of benthic organisms following the end permian mass extinction this study intends to establish a primary conodont biostratigraphical succession through the lower and middle triassic sequence at qingyan to provide a time framework for the understanding of the recovery and radiation process from the mass extinction a total of 30 species in 8 conodont genera are stratigraphically significant and assigned to the neospathodus dieneri neospathodus cristagalli neospathodus waageni neospathodus homeri chiosella timorensis and neogondolella cf bulgarica zones in ascending order most conodont zones correlate well with their counterparts recognized from elsewhere in china and even worldwide the first appearance of ns waageni marks the induan olenekian boundary which is placed at the lower middle part of the luolou formation 121 47 m above the permian triassic boundary the olenekian anisian early middle triassic boundary is here defined by the first occurrence of chiosella timorensis at the base of the qingyan formation although no conodonts retrieved from the upper qingyan formation containing the extraordinarily diverse biota i e the qingyan biota stratigraphical correlation with the neighbouring conodont bearing sections in guizhou and the ammonoid zones suggest that the qingyan biota has an age of early late anisian early middle triassic

pedogenesis across a climatic gradient in tropical high mountains cordillera blanca peruvian andes abstract studies in alpine environments have shown that chemical weathering and clay mineral formation are mainly controlled by climate and vegetation however few studies have focused specifically on pedogenesis in tropical high mountains we evaluated pedogenic processes and weathering intensity by physical chemical and mineralogical properties of soils under different vegetation types across a climatic gradient east west in the northern cordillera blanca peru we established 2 catenas and sampled 10 pedons 6 at llanganuco valley east dry and 4 at portachuelo valley west wet pedons from both catenas are formed on colluvial deposits gravelly and weakly developed showing a sequence of o a c and c r horizons lithological discontinuities in all pedons revealed sequences of buried a horizons they also shared the same soil forming processes related to organic matter accumulation such as humification melanization and formation of organometallic complexes the uppermost horizons show high values of total organic carbon and are dark colored in general pedons are acidic to slightly acidic have a low base saturation a high al saturation and low effective and potential cation exchange capacity seven pedons were classified as umbrisols one fluvisol one leptosol and one regosol their similarity is attributed to environmental instability not allowing sufficient time to develop further however pedons at portachuelo valley showed higher weathering intensity revealed by crystalline iron oxide formation and transformation of phyllosilicates minerals among them pedon under polylepis forest showed the highest weathering intensity which favored transformation of chlorite to mixed layered minerals suggesting that combined climate and vegetation control chemical weathering and mineral transformation