syrtis major a low relief volcanic shield viking orbiter images and earth based radar elevation data have been used to document the volcanic geology of syrtis major and to reevaluate its physiographic setting these data indicate that syrtis major is actually a very low relief simple shield with a central caldera complex arcuate segments of concentric grabens at the shield summit define the limits of a 280 km diameter depression that is thought to have been created by foundering of a magma chamber lava flows with well defined scarps are associated with two summit calderas fissures and lava tubes are recognized on the shield flanks the lava flows were deposited on volcanic ridged plains that do not display flow scarps compressional stresses acting on the shield were apparently greatest following the deposition of the ridged plains unit but continued at a somewhat reduced rate after deposition of the younger lavas the extremely low relief shield of the syrtis major as well as other volcanic plains of intermediate age in the eastern hemisphere of mars is in striking contrast to the giant shields of tharsis montes such different types of volcanic landforms may result from changes with times in the composition differentiation history eruption rates and eruption temperatures of surface igneous rocks thus directly reflecting the thermal and chemical evolution of the interior the low relief on the shields may also reflect a substantially thinner crust in these regions relative to tharsis the physiographic evidence and radar elevation data confirm the fact that syrtis major is a planum plateau rather than a planitia low plain as published maps of mars now portray the feature in addition present evidence does not support an earlier suggestion that an impact basin predated volcanism at syrtis major

mars near infrared comparative spectroscopy during the 1986 opposition abstract near infrared 0 7 2 5 m spectral observations of mars during the 1986 opposition were carried out at the mauna kea observatory utilizing the university of hawaii 2 2 m telescope spectra were obtained of several martian locations using a continuously variable filter cvf spectrometer with a resolution of 1 25 during two separate runs in june and august approximately 60 distinct spots between 354 w and 163 w and 32 n and 53 s were observed at an angular resolution of 0 5 to 1 5 arcsec corresponding to a spatial resolution on mars of 200 to 460 km varying with nightly seeing conditions these different spots fall roughly into a set of eight distinct geologic regions volcanic regions ridged plains ridged volcanic plains scoured plains impact basins channels and canyons densely cratered regions and layered terrain and ice the spectra exhibit typical noise related or weather induced errors of less than 4 of the full scale signal to analyze these spectral data spot to spot ratios or relative reflectance spectra were produced between spectra taken in different geologic regions spectral features observed in these ratios can act as indicators of mineralogic differences between areas under consideration perhaps the most striking result obtained from the many ratios taken close in time and under similar viewing geometries was the consistent lack of noticeable differences between spectra taken of areas which in geologic maps and viking orbiter images appear to have very different morphologies this observation leads to several possible conclusions a the spectral feature differences are below the detection limit of these measurements b the spatial resolution of spots observed on mars was not high enough to merit comparison with medium to high resolution viking orbiter images and geologic maps i e the local morphology varies significantly within the aperture region and a mixing or averaging effect operates to reduce the spectral feature differences c all of these regions are the same spectrally in the near infrared it is likely that all three of these effects operate to some degree to prevent spectral features from being observed among the areas measured possibility c may best explain these results as it is consistent with several previous studies indicating a grossly uniform mantle of global dust over much of the observed surface the message to mars orbiting spectroscopy experiments such as mars observer vims is that the spectral differences are small only a few percent of the continuum or nonexistent among many areas on mars on the scale of several hundred kilometers

paleoecological studies of a holocene lacustrine record from the kangerlussuaq sondre stromfjord region of west greenland abstract a lacustrine sediment record from the kangerlussuaq region west greenland has resulted in a pollen macrofossil and sediment stratigraphy that encompasses the last 5000 14 c yr deglaciation of the area and subsequent development of a nearby floodplain occurred before 5000 yr b p since that time eolian sand and silt deposition appear to have been continuous with a significant increase ca 1000 14 c yr b p pollen analysis shows little change in the character of the vegetation throughout the record fluctuations in herb pollen taxa indicate changes in the extent and development of eolian sand sheets the oldest pollen zone records relatively little pollen accumulation and low taxa diversity this is followed by a zone of high pollen accumulation presumably a phase of highest vegetation density from 4400 to 3400 14 c yr b p thereafter declining pollen accumulation rates reveal a gradual environmental deterioration macrofossil analyses record significant limnological changes with an early eutrophic phase followed by a masotrophic phase and a reversal to more eutrophic conditions in the final phase the preserved record illustrates the interactions of deglaciation eolian activity regional vegetation and limnological change

the carboniferous permian transition on the north china microcontinent oceanic climate in the tropics abstract the north china microcontinent was surrounded by tropical oceans during the carboniferous permian transition and experienced a wet tropical climate on this microcontinent vegetation represented the cathaysian floral realm that had taxa in common with the tropical euramerican floral realm but was characterized by endemic taxa and those that had already become extirpated in euramerica large parts of the north china microcontinent were covered by a cratonic basin in which marine paralic and entirely terrestrial beds were deposited that have been described as the taiyuan formation floras from the taiyuan formation indicate that this formation is time transgressive

origins of marslike spectral and magnetic properties of a hawaiian palagonitic soil a palagonitic soil hwmk1 from mauna kea hawaii has marslike spectral and magnetic properties reflectivity spectra of 20 m size separates resemble spectra for martian bright regions and reflectivity spectra of coarser size separates have some spectral characteristics in common with spectra for martian dark regions the bulk soil is magnetic with a saturation magnetization of 0 98 a m2 kg of sample 10 a m2 kg of fe at 296 k petrographic observations show that the soil contains separate populations of black and orange tephra particles which are relatively unaltered fragments of tachylite merocrystalline basalt and extensively weathered palagonitized fragments of sideromelane clear brown basalt glass respectively although both types of particles contain plagioclase and olivine microphenocrysts their iron oxide mineralogies are substantially different as documented by mossbauer and static magnetic measurements a strongly magnetic opaque iron oxide titanomagnetite is associated with black particles and is responsible for the magnetic nature of the soil a relatively weakly magnetic superparamagnetic ferric oxide and minor hematite are associated with orange particles and are responsible for the color the more highly weathered state higher state of oxidation of orange particles is a consequence of the faster weathering palagonitization rate for their sideromelane precursors than for tachylite increasing state of oxidation decreasing saturation magnetization and increasing near ir reflectivity with decreasing particle diameter of bulk soil are manifestations of the increasing proportions of palagonitic material as particle diameter decreases

spatial and temporal variability of lake ontogeny in south western greenland abstract holocene palaeolimnological records of diatoms and carotene a proxy for aquatic production from four lakes in the low arctic region of south western greenland were used to investigate the role of climate on lake ontogeny two of the lakes are located in the maritime coastal region near sisimiut and two inland close to the head of kangerlussuaq fjord where there is a more continental climate diatom records from the four lakes at1 at4 ss1381 ss8 had similar long term ontogeny trends independent of climatic setting and the changes are interpreted as responses to first order weathering controls on catchment lake chemistry short term excursions from these broad trends occurred in one coastal site at4 caused by intense erosion of the steep catchment and at inland sites where temporary hydrological closure and lake level decline occurred during the mid holocene 8000 5000 cal a bp algal production as carotene was more closely and consistently correlated with climatic changes it peaked during the mid holocene the warmest period of the holocene at all sites and there were transient increases in production in inland lakes during the medieval climate anomaly and little ice age because of fertilization through increased aeolian dust deposition a synthesis of seven palaeolimnological records from this region identified that only the mid holocene was correlated with diatom stratigraphic zones and there was considerable among site variability in later holocene lake response to climate forcing in this area comparable long term trends in species assemblage turnover dca ca axis 1 scores clearly demonstrate that lakes have predictable ontogeny trends in this region characterised by maximum alkalinity and nutrient availability in the first few millennia followed by progressive oligotrophication and alkalinity loss however individual lake and catchment characteristics lake morphology catchment geomorphology when modified by climatic change vegetation cover erosion weathering rates aeolian dust deposition lake level can diverge from this ontogeny template leading to complex ecological transitions in lakes from this region

radiation and extinction patterns in permian floras from north china as indicators for environmental and climate change abstract permian continental sequences from north china contain previously unrecognized episodes of plant radiation and elevated extinction the earliest extinction in the lower shihhotse formation roadian guadalupian records a 45 floral species loss and is tentatively correlated with global extinctions amongst dinocephalian reptiles two younger extinctions are dated by correlating the illawara reversal and palaeomagnetic polarity sequences from shanxi province against global palaeomagnetic history missing data from the shanxi sequence are evaluated using a novel approach estimating likely maximum and minimum sequence changes that provide age estimates for post illawara events in north china the second extinction in the middle upper shihhotse formation is more significant and is dated to the mid capitanian with a loss of 56 of plant species coinciding with two phases of volcanism of the emeishan large igneous province in south china previously linked to the mid capitanian marine mass extinction the youngest extinction in the upper upper shihhotse formation late capitanian to mid wuchapingian is catastrophic and represents the end of range in the sequence changes in sedimentary facies suggest it to be related to global climatic warming and drying other viable causal mechanisms for the extinction episodes include plate motion and collision global climate change volcanism and biological competition

palaeoecological studies of holocene lake sediments from west greenland abstract colonisation by plants and animals and subsequent biotic development in west greenland was studied by analyses of macrofossils in four holocene lake sequences one of the lake basins located near the outer coast was deglaciated shortly after the transition from the last glacial stage to the holocene and a basal date of 12 100 11 300 cal years bp was obtained two of the lake basins located near the margin of the greenland ice sheet were deglaciated several millennia later the oldest sediments contain low diversity floras and faunas some of the first immigrants were chironomidae and daphnia pulex soon followed by other insects crustaceans and other invertebrates water mosses ranunculus confervoides hippuris vulgaris and potamogeton filiformis were among the first plants that colonised the lakes the earliest holocene terrestrial flora in west greenland was probably entirely herbaceous with salix herbacea and empetrum nigrum being some of the first woody plants to arrive a number of invertebrates are new to the fossil fauna of greenland and the ostracod ilyocypris bradyi that was found in one sequence from 7000 to 6500 cal years bp has not been recorded from greenland before

foraminiferal reconstruction of mid to late holocene ocean circulation and climate variability in disko bugt west greenland benthic foraminifera from two cores collected from disko bugt a large marine embayment in west greenland are used to investigate hydrographic changes during the mid to late holocene the records document fluctuations in the west greenland current wgc linked to large scale changes in north atlantic circulation and for one core impacts of local climate changes in particular changes in the cold east greenland current egc and the warm more saline irminger current ic influence the wgc and propagate into disko bugt the cores record subsurface warming associated with the holocene thermal maximum htm from c 6 to 5 ka cal bp gradual cooling of wgc from 5 ka cal bp was interrupted by an abrupt warm interval from 3 9 to 3 5 ka cal bp before cooling became more prominent from 3 5 to 2 ka cal bp this cold period corresponds to the well documented northern hemisphere cooling of the neoglacial and we interpret it as reflecting enhanced flux from the egc and reduced ic flux to the wgc in disko b

the recession of the inland ice margin during the holocene climatic optimum in the jakobshavn isfjord area of west greenland recent subsurface mapping of parts of the greenland inland ice margin in the region of jakobshavn isbrae indicates that the fjord system in the period of at least 2700 4700 calendar yr b p was more ice free than at present and that the front of the glacier was at least 15 km behind the present position the 14c datings of subfossils brought to the present ice margin fit with the climatic records from ice cores and confirm the favourable conditions for greenland s first settlers the sarqaq people who arrived in the region about 4000 yr ago to find hunting grounds 10 20 larger than the present

permian vegetational pompeii from inner mongolia and its implications for landscape paleoecology and paleobiogeography of cathaysia plant communities of the geologic past can be reconstructed with high fidelity only if they were preserved in place in an instant in time here we report such a flora from an early permian ca 298 ma ash fall tuff in inner mongolia a time interval and area where such information is filling a large gap of knowledge about 1 000 m2 of forest growing on peat could be reconstructed based on the actual location of individual plants tree ferns formed a lower canopy and either cordaites a coniferophyte or sigillaria a lycopsid were present as taller trees noeggerathiales an enigmatic and extinct spore bearing plant group of small trees is represented by three species that have been found as nearly complete specimens and are presented in reconstructions in their plant community landscape heterogenity is apparent including one site where noeggerathiales are dominant this peat forming flora is also taxonomically distinct from those growing on clastic soils in the same area and during the same time interval this permian flora demonstrates both similarities and differences to floras of the same age in europe and north america and confirms the distinct character of the cathaysian floral realm therefore this flora will serve as a baseline for the study of other fossil floras in east asia and the early permian globally that will be needed for a better understanding of paleoclimate evolution through time

pyroxene spectroscopy revisited spectral compositional correlations and relationship to geothermometry the authors wish to thank the various agencies which have provided the necessary support for this project including grants in aid of research from sigma xi the scientific research society to e a c the geological society of america grant 3741 87 to e a c and nasa planetary geology and geophysics grant nagw 642 to m j g

reconstructing millennial scale regional paleoclimates of boreal canada during the holocene abstract regional paleoclimate reconstructions for northern canada quantify holocene climate variability on orbital and millennial time scales and provide a context to better understand the current global warming the reconstructions are based on available pollen diagrams from the boreal and low arctic zones of canada and use the modern analog technique mat four regional reconstructions document the space time evolution of the climate during the holocene highest summer and winter temperatures anomalies are found in central canada during the early holocene eastern canada was relatively cool in the early holocene whereas central canada was warmest at that time labrador was relatively dry in the early to mid holocene during which time western canada was relatively moist millennial scale temperature variations especially the medieval warm period and little ice age are seen across the continent with some suggestion of time transgressive changes from west to east at the millennial scale precipitatio

late holocene relative sea level rise and the neoglacial history of the greenland ice sheet in west greenland early and mid holocene relative sea level rsl fall was replaced by late holocene rsl rise during the neoglacial after 4 3 cal ka bp thousand calibrated years before present here we present the results of an isolation basin rsl study completed near to the coastal town of sisimiut in central west greenland rsl fell from 14 m above sea level at 5 7 cal ka bp to reach a lowstand of 4 0 m at 2 3 1 2 cal ka bp before rising by an equivalent amount to present differences in the timing and magnitude of the rsl lowstand between this and other sites in west and south greenland record the varied interplay of local and non greenland rsl processes notably the reloading of the earth s crust caused by a neoglacial expansion of the greenland ice sheet gis and the subsidence associated with the collapse of the laurentide ice sheet forebulge this means that the timing of the sea level lowstand cannot be used to infer directly when the gis advanced during the neoglacial the rise in late holocene rsl is contrary to recently reported bedrock uplift in the sisimiut area based on repeat gps surveys this indicates that a belt of peripheral subsidence around the current ice sheet margin was more extensive in the late holocene and that there has been a switch from subsidence to uplift at some point in the last thousand years or so

late paleozoic macrofloral assemblages from weibei coalfield with reference to vegetational change through the late paleozoic ice age in the north china block abstract based on investigations of seven stratigraphic sections in the weibei coalfield a typical coal basin in the north china block the succession of late paleozoic plant macrofossil assemblages from the benxi or penchi in old spelling taiyuan shanxi lower shihhotse and upper shihhotse formations were redefined these zones are the paripteris spp linopteris spp conchophyllum richthofenii assemblage benxi fm neuropteris pseudovata lepidodendron posthumii assemblage taiyuan and lower shanxi fms emplectopteridium alatum emplectopteris triangularis cathaysiopteris whitei assemblage upper shanxi and lower shihhotse fms gigantonoclea lagrelii fascipteris hallei lobatannularia heianensis assemblage upper shihhotse fm as a result of this biostratigraphic reanalysis it has become clear that biostratigraphic boundaries do not exactly correlate to lithostratigraphic boundaries as has been thought the biostratigraphy of the terrestrial deposits in the north china block were correlated to the iugs global chronostratigraphy the more precise chronostratigraphic constraints that were obtained as a result of this study make it possible to more precisely correlate the vegetational successions to the concurrent waxing and waning of the late paleozoic ice sheets

abrupt holocene climate change as an important factor for human migration in west greenland west greenland has had multiple episodes of human colonization and cultural transitions over the past 4 500 y however the explanations for these large scale human migrations are varied including climatic factors resistance to adaptation economic marginalization mercantile exploration and hostile neighborhood interactions evaluating the potential role of climate change is complicated by the lack of quantitative paleoclimate reconstructions near settlement areas and by the relative stability of holocene temperature derived from ice cores atop the greenland ice sheet here we present high resolution records of temperature over the past 5 600 y based on alkenone unsaturation in sediments of two lakes in west greenland we find that major temperature changes in the past 4 500 y occurred abruptly within decades and were coeval in timing with the archaeological records of settlement and abandonment of the saqqaq dorset and norse cultures which suggests that abrupt temperature changes profoundly impacted human civilization in the region temperature variations in west greenland display an antiphased relationship to temperature changes in ireland over centennial to millennial timescales resembling the interannual to multidecadal temperature seesaw associated with the north atlantic oscillation

results from the ism experiment the imaging spectrometer ism operating in the near infrared is the first ever flown in space for planetary observation with a spectral range of 0 76 3 14 m its main goals were to obtain information on the mineralogical composition of the surfaces of mars and phobos and on the composition spatial and temporal variations of the martian atmosphere the infrared imaging spectrometer ism acquired 40 000 spectra of mars and phobos here we present the first results on the surface mineralogy of mars and phobos and the atmospheric composition of mars

holocene records of effective precipitation in west greenland holocene changes in effective precipitation precipitation evaporation p e were reconstructed for the sondre stromfjord region of southwest greenland using the sediment records of two neighbourin

the holocene sedimentary history of the kangerlussuaq fjord valley fill west greenland abstract west greenland has been intensively studied to reconstruct and better understand past relative sea level changes and deglacial history this study extends these efforts by linking sea level and deglacial history to the sedimentary infill successions of kangerlussuaq fjord and associated landward valleys based on published and new land and sea based geophysical data radiocarbon dates and geological observations we have characterized the infill and reconstructed the sedimentation history during the holocene based on a revised sea level curve and data presented in this paper we defined three depositional phases phase i 7000 yr bp is represented by dominant glaciomarine deposition associated with a tide water glacier system as the greenland ice sheet gis continued to retreat it became land based during phase ii 7000 1500 yr bp two separate depocenters formed keglen delta depocenter arose from a temporary stabilization phase of the gis and prograded rapidly over the glaciomarine deposits of phase i further inland proglacial lake formation and subsequent sedimentary infill associated with the ongoing gis retreat is represents the second depocenter the watson river connected both depocenters by a flood plain which transferred sediment from the gis to the keglen delta ongoing sea level fall due to glacio isostastic uplift combined with a gradually cooler and dryer climate resulted in terrace formation along the watson river flood plain around 4000 yr bp the gis margin reached its most landward location and began to advance to its present location the final phase phase iii

palaeohydrology of kangerlussuaq sondre stromfjord west greenland during the last 8000 years major fluctuations of hydroclimate in west greenland are recorded in paleoshoreline terraces that encircle several lakes near kangerlussuaq greenland 67 01 n 50 40 w geomorphic and stratigraphic analyses were used to construct a lake level curve for hunde so a large closed basin lake in this region changes in lake volume associated with lake level fluctuations were cal culated and a water balance model was used to determine the primary factors influencing lake volume and the changes in those factors necessary to affect reconstructed lake level change sensitivity tests suggest that mean annual precipitation and the relative proportion of summer versus winter precipitation are the primary climate drivers of lake level change temperature effects are less important unless coupled with changes in one of the other variables two pluvial periods occurred centered around 4600 and 2000 cal yr bp with mean annual precipitation estimated at 130 mm and 70 mm higher than modern respectively in contrast a low stand prior to 6070 cal yr bp with water levels as much as 18 m below modern was a result of summer temperatures 2 3 above modern coupled with a 14 day increase in the length of the iceoff period and a reduction in mean annual precipitation of 80 mm relative to modern

implications for deglaciation chronology from new ams age determinations in central west greenland abstract new evidence has been obtained for the age of the umivit keglen and orkendalen moraine systems close to the present ice sheet margin in central west greenland the umivit keglen moraine system is dated at 7500 to 6500 14 c yr b p which is older than the previously assumed date of 7300 to 6000 14 c yr b p the orkendalen system is now dated at 6200 to 5600 14 c yr b p against earlier estimates of 300 to 700 14 c yr b p the new age is based on ams radiocarbon dated organic material within depressions between morainic ridges belonging to the orkendalen system a major implication of the new age is that ice margin positions prevailed for about 6000 years behind the present ice sheet margin the retreat behind the present margin could be substantial and in the light of deglaciation rates prior to the orkendalen phase may be ca 10 s of kilometers rather than kilometers circumstantial evidence is found for the retreat of the ice sheet margin behind its present position during the holocene climatic optimum the results placed into a time frame of deglaciation since the last glacial maximum enable comparison with greenland ice sheet models and ice core records

permian stratigraphy and correlation of northeast china a review palaeontological lithostratigraphical data from the permian strata and correlation of the permian successions for different tectonic units in northeast china are reviewed and summarized in this paper permian strata in northeast china are dominated by brachiopods fusulinoideans and land plants with limited ammonoids conodonts and bivalves the cisuralian early permian in the northern margin of the north china block and in the manchuride belt is composed mostly of marine massive limestone with the characteristic pseudoschwagerina zone in the asselian and sakmarian and the misellina claudiae zone in the kungurian the cisuralian in the xing an block and the northeastern part of inner mongolia is dominated by huge terrestrial deposits with fossil plants the guadalupian middle permian in the manchuride altaid and yanbian belts are characterized by bi temperate roadian or early wordian monodiexodina fauna and the late wordian capitanian codonofusiella schwagerina or neoschwagerina yabeina faunas the mixed brachiopod faunas between the boreal antitropical and the palaeoequatorial cathaysian forms the roadian or early wordian solitary coral faunas and the late wordian capitanian compound waagenophyllum wentzelella fauna the nadanhada terrane contains some exotic limestone blocks with a typical cathaysian neoschwagerina yabeina fauna in a late jurassic early cretaceous melange which is related to mesozoic subduction in the western circum pacific region the lopingian late permian in northeast china is mostly characterized by terrestrial molasse deposits with a mixed flora between the boreal angaran and the palaeoequatorial cathaysian provinces indicating the final closure of the palaeo asian ocean c 2005 elsevier ltd all rights reserved

the relationship between euramerican and cathaysian tropical floras in the late palaeozoic palaeobiogeographical and palaeogeographical implications abstract wetland plant communities persisted though much of the pennsylvanian in euramerica and are the dominant coal forming vegetation in this region distribution of these floras show a dramatic decline at the end of the carboniferous with many of the plant genera and species becoming extinct by the onset of the permian this has been correlated with climate change and in particular aridification associated with northwards plate motion and euramerica moving into the doldrums but is also associated with the variscan orogeny and forefront destroying large areas of formerly lowland basinal settings other factors may include pennsylvanian glaciations as evidenced by cyclothem and rhythmical deposition in lowlying wetland settings and change in eustatic base level evidence from euramerica demonstrates extinction of this kind of wetland biota by the earliest permian and the development of drier floras including conifer dominated assemblages however new data from other parts of the world most notably north china confirm this model and highlight the presence of similar coal swamps ranging from the late pennsylvanian through the permian in this paper we summarise and synthesize recent taxonomic and systematic investigations undertaken on the plant fossils from the pennsylvanian benxi formation the oldest recognised wetland plant community in china and the early permian taiyuan formation the best preserved wetland plant community from china results indicate a remarkable similarity of the pennsylvanian early permian floras of north china with the older assemblages in the pennsylvanian of euramerica and the presence of typical euramerican coal swamp plant families genera and in some cases species in china conclusions include the presence of the ameriosinian phytogeographical realm uniting euramerica and northern cathaysia at this time coal swamps in the permian of north china evolving from a euramerican origin and the dramatic floral turnover at the end of the carboniferous representing a regional event rather than a global extinction episode patterns of plant distribution through this interval have profound implications on established palaeogeographical models and support continental connection between euramerica and cathaysia before the end of the carboniferous contradicting ideas of cathaysian island biogeography and biotic distinction continental connection appears to be related to glacial eustatic low stand and previously shallow marine environments becoming vegetated also important is the fact that in both euramerica and north china the pattern of floristic demise within wetland plant communities are similar to each other implying the same causal mechanisms with plants occupying waterlogged positions being the most severely devastated however ecosystem demise occurred at the end of the carboniferous in euramerica and in the middle permian in north china but in both cases the primary cause was climate change

geochronology and geochemistry of the fossil flora bearing wuda tuff in north china craton and its tectonic implications abstract the wuda tuff flora in the north china craton ncc is a vegetational pompeii and one of the most completely preserved marsh ecosystems of the late paleozoic northern hemisphere however the precise age geochemistry and petrogenesis of the thick tuff containing this peat forming flora have not been established we conducted a comprehensive petrographic mineralogical whole rock geochemical and zircon u pb and hf o isotopic investigation of five samples from a vertical section through the tuff bed our results confirm that the material that buried the flora is a volcanic tuff bed that has undergone intensive post deposition alteration whole rock al2o3 tio2 ratios 65 8 103 5 and negative eu eu values 0 27 0 38 further suggest a felsic volcanic origin secondary ion mass spectrometry zircon u pb dating of the altered tuff bed yielded a weighted mean 206pb 238u age of 295 9 1 4 ma 1 mswd 0 94 n 39 constraining the age of the wuda tuff flora to the earliest permian depletions of nb and ta in both the whole rock and zircon compositions indicate an arc related setting for the volcanism the positive ehf t values 0 0 to 5 0 and 18o values 5 05 6 17 of zircon grains from the wuda tuff suggest a juvenile crust origin of the volcanic magma geochemical comparisons with contemporaneous igneous rocks suggest that the volcanic eruption that led to the formation of the wuda tuff and associated vegetational pompeii was most probably caused by arc volcanism along the western margin of the ncc related to subduction of paleo asian ocean oceanic crust implying that the alxa terrane had not yet amalgamated with the ncc during the early permian

observational evidence of crystalline iron oxides on mars visible to near ir 0 4 1 0 mu m spectral reflectance observations of mars during the 1988 opposition were performed at mauna kea observatory using a circular variable filter spectrometer at a spectral resolution r lambda delta lambda approx 80 on august 13 and 14 1988 ut 41 regions 500 600 km in diameter were observed on mars the data have been reduced both to reflectance relative to solar analog mars 16 cyg b and to relative reflectance spot spot the spectra show the strong near uv reflectance dropoff characteristic of mars as well as absorptions at 0 62 0 72 mu m and 0 81 0 94 mu m both seen here clearly for the first time these absorption features are interpreted as fe sup 3 electronic transition bands that indicate the presence of crystalline ferric oxide or hydroxide minerals on the martian surface comparison of these data with laboratory spectra obtained by other workers supports the conclusion that a single iron oxide phase most likely hematite could account for all of the observed spectral behavior of the martian surface soils and airborne dust in the 0 4 1 0 mu m region this possibility must be reconciled with data from other possible spectral analogs and other wavelength regions as well as geochemical and mineral stability considerations to arrive at amore more complete understanding of the role of ferric minerals in martian surface mineralogy and weathering less

subglacial permafrost evidencing re advance of the greenland ice sheet over frozen ground abstract greenland ice sheet gris covers an area of 1 7 million km2 it has been an important source of climate information and the air temperature history of greenland is well known however the thermal history and temperature conditions of the greenland bedrock are poorly known there are only few records on the temperature of the proglacial bedrock and no records on bedrock temperature underneath the ice sheet the greenland analogue project gap recently investigated hydrological hydrogeological and geochemical processes in kangerlussuaq west greenland because permafrost has a major hydrological impact in arctic regions the cryogenic structure of the bedrock was an important research topic from previous studies it was already known that kangerlussuaq is located within the zone of continuous permafrost temperature profiling in a new research borehole extending horizontally 30 m underneath the ice sheet revealed that permafrost is 350 m deep at the ice margin this result raised the question how far the permafrost extends under the ice sheet in order to investigate the thermal properties we made a series of electromagnetic em soundings at the ice margin area on proglacial area and on the ice sheet and detected that subglacial permafrost extends at least 2 km from the ice margin to inland we also observed a patchy unfrozen sediment layer between the ice and the frozen bedrock possible existence of subglacial sediments and their role in ice dynamics has been debated in many recent papers our successful campaign shows that geophysics can be used for bedrock investigations through thick ice which is known to be challenging for electromagnetic methods our results provide the first direct evidence supporting the proposed holocene ice re advance over frozen ground and contribute to the discussion on the rapid climate changes in past to the future of the ice sheet under warming climate and hydrogeology at the ice margin

permo carboniferous climate early pennsylvanian to late permian climate development of central europe in a regional and global context a well justified stratigraphical correlation of continental successions and new palaeogeographic reconstruction of pangaea reveal new insights into the northern pangaean climate development influenced by palaeogeography palaeotopography glacio eustatic sealevel changes and ocean currents the overall permo carboniferous aridization trend was interrupted by five wet phases these are linked to the gondwana icecap the aridization and weakening of wet phases over time were not only caused by the drift of northern pangaea to the arid climatic belt but also by the successive closure of the rheic ocean which caused the expansion of arid semi arid environments in the lower middle permian the end of the gondwana glaciation rearranged ocean circulation leading to a cold coast parallel ocean current west of northern pangaea blocking moisture coming with westerly winds the maximum of aridity was reached during the roadian wordian the trans pangaean mountain belt was non existent its single diachronous parts never exceeded an average elevation of 2000 m the maximum elevation shifted during time from east to west the hercynian orogen never acted as an orographic east west barrier and the inter tropical convergence zone was widely displaced causing four seasons dry summer winter wet spring autumn at the equator and a strong monsoon system the climate history of the european realm during the late carboniferous pennsylvanian and permian is stored in many solitary basins fig 1 within the hercynian orogen and the foreland basin the story of westphalian climate is well known because of the numerous investigations of the coal bearing variscan foredeep the younger westphalian is characterized by a slight aridization abbink van kronijnenburgvan cittert 2003 oplustil 2004 which was accompanied by an increase of seasonality nevertheless the environment was strongly influenced by the ocean and epi continental seas with multiple transgression events the last extensive marine ingression was the aegir mansfield band westphalian b c the post westphalian climate development is more differentiated and

reconstructing early permian tropical climates from chemical weathering indices this study was financially supported by the national natural science foundation of china grants 41302083 41572078 the national basic research program of china grant 2011cb808800 and the fundamental research funds for the central universities grant cugl140402 china university of geosciences wuhan p a cawood acknowledges support from nerc grant ne j021822 1

a revised chronology for aeolian activity in subarctic fennoscandia during the holocene detailed sedimentological studies and parallel sampling for 14c and infra red stimulated luminescence age assays were undertaken at six sites lying beyond and below the tree line with the objective of establishing the historical development of aeolian landforms in lapland the main issues were a the timing of dune activity and processes of stabilization b the specific processes responsible for the past and contemporary activity new data indicate that many of the primary dunes were active for several millennia after deglaciation diachronous stabilization at both local and regional scales appears likely initial stabilization occurred in local interdune areas and where regional dune fields were colonized by pine generally before 7 ka local large dunes and some regional dunefields only became stable around 4 3 ka when the regional groundwater table rose and late pine colonization was possible the latest episode of aeolian activity dates from ad 1100 1650 across the area a unique deflation trigg

mars paleostratigraphic restoration of buried surfaces in tharsis montes volcanism in the tharsis province of mars occurred in several different areas and was generally continuous without large time intervals between eruptive episodes major lava flow units are numerous and extensive but relatively thin in many places impact craters on buried surfaces project above younger flows that overlie them a new application of crater dating methods has been developed to aid in the identification of these buried surfaces and to determine their lateral extent the technique is especially adaptable to the tharsis region where the stratigraphic succession of major flow units has been established by detailed geologic mapping knowledge of the overall stratigraphy allows correlations to be made between known and unknown surfaces by comparing their crater frequencies at diameters large enough to insure their recognition on the buried unit the method has been applied to aid in the restoration of buried rock units and to construct a series of paleostratigraphic maps showing the sequence of major eruptive events in the tharsis region

permo carboniferous paleogeography and coal accumulation and their tectonic control in the north and south china continental plates abstract permo carboniferous strata in north china and south china were essentially controlled by paleogeography paleoclimate and plate tectonics during that time north china and south china were separate microcontinents located on opposite sides of the equator thus the characteristics of their coal deposits differ substantially in north china the coal seams were initially deposited on a north sloping epicontinental basin during the middle carboniferous by the middle of the late permian the locus of coal formation had shifted from the north to the south as a result of the uplift of the northern margin due to continental collision with the siberian plate as the paleoplate was situated in the low northern latitudes moist tropical climate and favorable geographic setting allowed the extensive development of late carboniferous and earliest permian peat swamps on the northern alluvial fluvial plain and central paralic regimes more significantly two thick coal sequences were formed in the transition belt between the alluvial apron and fluvial plain and the shoreline area where high groundwatertable fed by both rainwater and groundwater favored the formation of thick peat in swamps with northward drift the paleoplate entered the subtropic semiarid and arid climatic belt between the late early permian and early late permian coal formation was restricted to the paralic delta plain where locally oceanic wet climate and high groundwatertable prevailed following this the subduction of the paleo tethys beneath the southern margin of north china led to the upwarp of the southern margin and kept the delta system growing vertically for a considerable period so that it kept pace with shoreline fluctuations on the southern area the result was that multicycle deltaic coals were well developed at this stage in south china coal was formed in the coastal zone of an epeiric and shelf sea which connected the marinal basins the basins were frequently influenced by plate marginal tectonic movements and continental rifting related to back arc extension as a result coal formation was often interrupted by sea level fluctuations early carboniferous coal was deposited during the short regressions during the widespread transgression mainly on the restricted marine paralic plain where clastic deposition was active in the middle and late carboniferous no coal was formed because the paleoplate had drifted into a subtropic arid belt early permian coal accumulated at first in the northeast and later in the southwest due to tectonic influences in the late permian relatively thick and extensive coal was formed even though it was during a transgressive period in both the western and eastern margins under the equatorial hot humid conditions in general the seam geometry and quality particularly ash and sulfur of the coal was directly controlled by the geography and the changes in the depositional environments however the fluctuation in coal formation and the migration of thicker coal zones was indirectly controlled by paleoclimate and the sea level fluctuations in response to plate tectonic influences

early permian asselian vegetation from a seasonally dry coast in western equatorial pangea paleoecology and evolutionary significance abstract the pennsylvanian permian transition has been inferred to be a time of significant glaciation in the southern hemisphere the effects of which were manifested throughout the world in the equatorial regions of pangea the response of terrestrial ecosystems was highly variable geographically reflecting the interactions of polar ice and geographic patterns on atmospheric circulation in general however there was a drying trend throughout most of the western and central equatorial belt in western pangea the climate proved to be considerably more seasonally dry and with much lower mean annual rainfall than in areas in the more central and easterly portions of the supercontinent here we describe lower permian upper asselian fossil plant assemblages from the community pit formation in prehistoric trackways national monument near las cruces south central new mexico u s a the fossils occur in sediments within a 140 m wide channel that was incised into indurated marine carbonates the channel filling can be divided into three phases a basal channel limestone conglomerate facies contains allochthonous trunks of walchian conifers a middle channel fill is composed of micritic limestone beds containing a brackish to marine fauna with carbon oxygen and strontium isotopic composition that provide independent support for salinity inferences the middle limestone also contains a par autochthonous adpressed megaflora co dominated by voltzian conifers and the callipterid lodevia oxydata the upper portions of the channel are filled with muddy gypsiferous limestone that lacks plant fossils this is the geologically oldest occurrence of voltzian conifers it also is the westernmost occurrence of l oxydata a rare callipterid known only from the pennsylvanian permian transition in poland the appalachian basin and new mexico the presence of in situ fine roots within these channel fill limestone beds and the taphonomic constraints on the incorporation of aerial plant remains into a lime mudstone indicate that the channel sediments were periodically colonized by plants which suggests that these species were tolerant of salinity making these plants one of if not the earliest unambiguous mangroves

a diatom based sea ice reconstruction for the vaigat strait disko bugt west greenland over the last 5000 yr abstract a diatom based sea ice concentration sic transfer function was developed by using 72 surface samples from west of greenland and around iceland and validated against associated modern sic canonical correspondence analysis on surface sediment diatoms and monthly average of sic indicated that april sic is the most important environmental factor controlling the distribution of diatoms in the area justifying the development of a diatom based sic transfer function the agreement between reconstructed sic based on diatoms from west greenland and the satellite and modelled sea ice data during the last 75 yr suggests that the diatom based sic reconstruction is reliable for studying the palaeoceanography off west greenland relatively warm conditions with a strong influence of the irminger current ic were indicated for the early part of the record 5000 3860 cal yr bp corresponding in time to the latest part of the holocene thermal maximum between 3860 and 1510 cal yr bp april sic oscillated around the mean value 55 and during the time interval 1510 1120 cal yr bp and after 650 cal yr bp was above the mean indicating more extensive sea ice cover in disko bugt agreement between reconstructed april sic and changes in the diatom species suggests that the sea ice condition in disko bugt was strongly influenced by variations in the relative strength of two components of the west greenland current i e the cold east greenland current and the relatively warm ic further analysis of the reconstructed sic record suggests that solar radiation may be an important forcing mechanism behind the historic sea ice changes

high resolution reflectance spectra of mars in the 2 3 μm region evidence for the mineral scapolite spatially resolved reflectance spectra of mars in the 2 2 to 2 4 m spectral region were obtained in august 1988 using the nasa 3 m infrared telescope facility the spectra show weak absorption features due to martian atmospheric carbon monoxide and a surface mineral both co and the mineral absorptions are composed of overlapping narrow features but in many locations such as hellas chryse eden and moab the mineral absorptions are quite strong at least 3 times stronger than at the most absorbing wavelengths of co near 2 33 m therefore co complicates the analysis of the surface mineral but does not always overwhelm its signature model removal of the martian atmospheric co has been performed and the remaining absorption bands are identified as scapolite relatively strong absorptions that match bands in the spectrum of scapolite and have little or no co absorption interference are seen near 2 41 2 39 and 2 29 m absorption also occurs at the scapolite bands at 2 36 and 2 33 m but the analysis is complicated by uncertainty in the atmospheric co removal at these wavelengths weaker scapolite bands are seen at 2 44 and 2 23 m where there is virtually no atmospheric interference the scapolite bands observed on mars are due to hco3 and hso4 ions in the scapolite structure the bicarbonate and bisulfate contents appear to vary with location the scapolite in hellas is more bisulfate rich relative to that in the chryse moab eden area other locations contain little arabia syrtis major hellespontica and isidis or no scapolite e g margaritifer ausonia and erythraeum the calculated abundances are unconstrained because the amounts of hco3 and hso4 in the martian scapolites as well as their grain sizes are not known if the scapolites contain about 3 wt of each near the maximum possible the scapolite abundances probably range from about 5 wt scapolite at eden and hellas 3 5 at chryse moab and oxia palus 2 3 at arabia syrtis major and isidis to less than 2 at hellespontica syrtis minor and margaritifer assuming a relatively large grain size of 50 100 m if the characteristic grain sizes are smaller or the hco3 and hso4 contents are lower the scapolite abundances required to match the observed band depths would be higher the mineral bands are apparent in many of the mars spectra measured so it appears to be widely but not uniformly distributed the newly observed fine structure also varies greatly in both depth and spectral detail with location on mars thus there appears to be regional variations in composition the mineral phases appear to reflect local or regional geology and are not primarily contained in the homogeneous globally redistributed aeolian dust higher spectral resolution martian spectra in the 2 3 m region as well as at 3 9 m are needed to confirm the scapolite identification and to constrain its abundance

a continuous record of holocene eolian activity in west greenland eolian landforms are widespread alongside proglacial valley sandurs in west greenland and comprise low relief sand sheets climbing dunes and upland loess sedimentary facies mainly reflect distance to outwash source zones and the influence of vegetation cover the sediments show stratification types typical for poorly to moderately vegetated sand sheets alternately laminated silt peat sequences and unstratified loess twenty five accelerator mass spectrometry 14c dates provide the basis for the chronostratigraphy of the inland eolian deposits 14c dates from interstratified sand sheets suggest that the bulk of eolian sands were deposited prior to 3400 cal yr b p and after 550 cal yr b p this two phase formation for the inland dunes most likely reflects local changes in proglacial floodplain development and meltwater rerouting associated with a significant recession of the greenland ice sheet during the mid holocene climate optimum subsequent floodplain regeneration and renewed sand sheet formation after 550 cal yr b p followed when the ice margin readvanced to its present position in contrast atmospheric deposition of regionally derived silt in upland peat mires has been continuous since at least 4750 cal yr b p silt influx data demonstrate a strongly episodic history of the intensity of eolian activity over the past five millennia which tentatively reflects alternating periods of winter aridity associated with the variable incursion of maritime air masses over the interior ice free areas of west greenland

holocene thermal maximum in the western arctic 0 180 w the spatio temporal pattern of peak holocene warmth holocene thermal maximum htm is traced over 140 sites across the western hemisphere of the arctic 0 180 w north of 60 n paleoclimate inferences based on a wide variety of proxy indicators provide clear evidence for warmer than present conditions at 120 of these sites at the 16 terrestrial sites where quantitative estimates have been obtained local htm temperatures primarily summer estimates were on average 1 6 0 8 c higher than present approximate average of the 20th century but the warming was time transgressive across the western arctic as the precession driven summer insolation anomaly peaked 12 10 ka thousands of calendar years ago warming was concentrated in northwest north america while cool conditions lingered in the northeast alaska and northwest canada experienced the htm between ca 11 and 9 ka about 4000 yr prior to the htm in northeast canada the delayed warming in quebec and labrador was linked to the residual laurentide ice sheet which chilled the region through its impact on surface energy balance and ocean circulation the lingering ice also attests to the inherent asymmetry of atmospheric and oceanic circulation that predisposes the region to glaciation and modulates the pattern of climatic change the spatial asymmetry of warming during the htm resembles the pattern of warming observed in the arctic over the last several decades although the two warmings are described at different temporal scales and the htm was additionally affected by the residual laurentide ice the similarities suggest there might be a preferred mode of variability in the atmospheric circulation that generates a recurrent pattern of warming under positive radiative forcing unlike the htm however future warming will not be counterbalanced by the cooling effect of a residual north american ice sheet

contemporary glacigenic inputs to the dust cycle the importance of glacigenic dust in the earth s system during glacial periods is widely acknowledged under contemporary conditions the world s largest dust sources are in low lying hot arid regions and this is where most aeolian research is focused however the processes of dust production and emissions are still operating in cold climate regions particularly in proglacial areas this paper assesses current understanding of the relationship between glacierised landscapes and dust emissions and inputs to the global dust cycle it focuses on how elements in the glacial and aeolian geomorphic sub systems interact to determine the magnitude frequency and timing of aeolian dust emissions and on feedback mechanisms between the systems where they have been measured dust emission intensity and deposition rates in glacierised catchments are very high in some cases far exceeding those in lower latitudes however few studies span long time scales the impact of future glacier retreat on the balance between sediment supply availability and aeolian transport capacity and implications for glacigenic dust emissions is also considered this balance depends on relative spatial and temporal changes in meltwater suspended sediment concentration and wind strengths which promote dust emissions and patterns and rates of soil development and vegetation succession on recently deglaciated terrain which protect sediments from deflation retreat of the antarctic ice sheet could mean that in future glacigenic contributions to the dust cycle exceed those of non glacigenic sources in the southern hemisphere copyright 2012 john wiley sons ltd

crater size frequency distributions and a revised martian relative chronology a revised martian relative chronology is determined which dates geologic units with respect to the end of the period of heavy bombardment this analysis differs from previous studies by using viking 1 2m photomosaics to map all 25 826 craters 8km diameter which postdate the lithologic units making up the martian surface the relative plotting technique is used because it shows changes in the shape and density of the crater size frequency distribution curves more clearly than cumulative plots the changes in shapes of the distribution curves are interpreted to be due to two different impacting populations one dominating during the heavy bombardment period and the other emplaced during the post heavy bombardment period the 8 km diameter limit was chosen to exclude the majority of secondary craters and to minimize obliteration effects acting over the age of the planet the results obtained are average ages valid for units with typical thicknesses between about 1 and 3 km and extending over an area of about 105 km2 the shapes and densities of the crater distribution curves indicate that approximately 60 of the martian lithologic units in which these craters occur formed during the period of heavy bombardment many of the small volcanoes those generally less than 200 km diameter including most in the tharsis and elysium regions date from this period the hellas and argyre impacts bracket the average age of the intercrater plains in the highlands the ridged plains distribution curves indicate formation during the period of heavy bombardment but their lower crater density indicates that they are the last geologic unit to retain the scars from this population of impactors they therefore likely formed near the end of heavy bombardment the remaining 40 of martian terrain units show distribution curves indicative of emplacement since the end of heavy bombardment the wide range in crater densities among different regions of plains indicate a range in formation ages although the general view of martian geologic evolution does not differ significantly from previous studies the present analysis explicitly states the relationship of numerous geologic units to the period of heavy bombardment and has revised the relative ages of localized regions across mars

preliminary 10be chronology for the last deglaciation of the western margin of the greenland ice sheet the now acknowledged thinning of the greenland ice sheet raises concerns about its potential contribution to future sea level rise in order to appreciate the full extent of its contribution to sea level rise reconstruction of the ice sheet s most recent last deglaciation could provide key information on the timing and the height of the ice sheet at a time of rapid climate readjustment we measured 10be concentrations in 12 samples collected along longitudinal and altitudinal transects from sisimiut to within 10 km of the isunguata sermia glacier ice margin on the western coast of greenland along the longitudinal transect we collected three perched boulders and two bedrocks in addition we sampled seven perched boulders along a vertical transect in a valley within 10 km of the isunguata sermia glacier ice margin our pilot dataset constrains the height of the ice sheet during the last glacial maximum lgm between 500 m and 840 m including the 120 m relative sea level depression at the time of the lgm 21 ka bp from the transect we estimate the thinning of the ice sheet at the end of the deglaciation between 12 3 1 5 10be ka n 2 and 8 3 1 2 10be ka n 3 to be 6 cm a 1 over this time period direct dating of the retreat of the western margin of the greenland ice sheet has the potential to better constrain the retreat rate of the ice margin the thickness of the former ice sheet as well as its response to climate change copyright 2008 john wiley sons ltd

ancient and modern cold climate aeolian sand deposition a review although partly active aeolian sand sheets and dunes cover large areas in the zones of dis continuous permafrost little precise information is available about the influence of cold climate conditions on modern aeolian processes this means that palaeoenvironmental reconstructions in the stabilised mainly late pleistocene dune fields and cover sand regions in the sand belts of the european lowlands and the northern great plains of the usa and canada are necessarily still based on ancient evidence cold climate wind deposits are typically derived from areas of abundant sediment supply like unvegetated flood plains glacial outwash plains till plains and lake shores the common parabolic and transverse dune forms resemble those observed in temperate regions although a variety of periglacial features has been identified in late pleistocene dune and cover sands none of them indicate that permafrost is crucial to aeolian activity specific structures in aeolian strata permit tentative interpretation of the moisture content of depositional sand surfaces the nature of annual sedimentation cycles and the processes by which strata were deposited and or contorted but surprisingly little is known about the role of vegetation in the process of sand accumulation dunes are most informative with respect to reconstructions of past wind regimes which offer important data for verification of palaeoclimatic simulations

the surface of syrtis major composition of the volcanic substrate and mixing with altered dust and soil syrtis major is an old low relief volcanic plateau near the equatorial regions of mars it is a persistent low albedo feature on the planet and is thought to contain a high abundance of exposed bedrock and or locally derived surface material and debris spatially resolved variations in surface spectral properties and therefore composition are investigated with data from the imaging spectrometer for mars ism instrument ism obtained 128 wavelength channel spectra from 0 76 to 3 16 m for contiguous pixels approximately 22 22 km in size across much of the plateau the value and spatial distribution of four primary spectral variables albedo continuum slope wavelength of the ferric ferrous band minimum area of the ferric ferrous absorption are mapped and coregistered to viking digital photomosaics analysis of these maps shows that although there is a high degree of overall spectral variability on the plateau the key indicators of mafic mineralogy are relatively homogeneous detailed examination of reflectance spectra from representative areas across the plateau indicate the volcanic surface is dominated by augite bearing basalts and the pyroxene composition in the basalts is estimated to be 0 275 0 075 ca ca fe mg and 0 3 0 1 fe fe ca mg additional mineral components may include olivine feldspar and glass most of the spectral variability on the plateau is interpreted to result from mixing of volcanic bedrock and or locally derived surface material and debris with highly altered dust and soil in western syrtis major the altered material is a transient component on the surface or occurs in large spatially coherent patches e g crater rims in eastern syrtis major it is apparent that the dust components are firmly fixed to the basaltic substrate as a stable oxide rind or coating

large shifts in vegetation and climate during the early weichselian mis 5d c inferred from multi proxy evidence at sokli northern finland abstract for decades detailed studies on early weichselian deposits have been made in central europe in contrast these studies are rare in fennoscandia in northern europe we here integrate an extensive multi proxy data set obtained on sediments of mis 5d c age that form part of a long sediment record preserved at sokli in northern finland we make a detailed interpretation of the vegetation and depositional history for mis 5d c using pollen macrofossils diatoms and other siliceous microfossils insect remains and sediment characteristics and combine these data with recently published estimates on july temperatures based on chironomids and selected plant indicator species in order to make inferences of paleo climate regimes the fossil record obtained on the seven meter thick mis 5d c deposit at sokli is exceptionally rich in species due to the large variety of habitats associated with an overall fluvial depositional environment a braided river system flanked by steppe tundra vegetation is inferred for mis 5d mean july temperatures of at least 12 14 c are indicated by chironomids and plant indicator species and are in agreement with the presence of conifers and birch trees as recorded by macrofossils the reconstructed environmental conditions suggest strong continental climate conditions at sokli during mis 5d the gradual infilling of an oxbow lake and subsequent return to stream channel deposition is traced in great detail in the overlying gyttja and gravelly sediment of mis 5c age the terrestrial pollen and plant macrofossil record from the gyttja shows the establishment of birch forest followed by the spread of pine and then spruce rich plant indicator species assemblages indicate that the boreal environment at sokli during mis 5c experienced july temperatures several degrees higher than the present day value of 13 c the high summer temperatures and presence of larch suggest more continental conditions more open vegetation returned at sokli during late mis 5c and was followed by glaciation by the fennoscandian ice sheet mis 5b despite the major differences in zonal vegetation types during mis 5d c differences in reconstructed july temperatures are minor and suggest that winter temperatures combined with precipitation values mostly determined the stadial interstadial climate variability the most compelling conclusion from our study is that forest development during mis 5c was remarkably similar to that recorded for the eemian mis 5e and holocene interglacials at the high latitude site sokli and also to that inferred from mis 5c sediments on the northern european mainland our results question the definition of mis 5c in the terrestrial record of europe as an interstadial interval of the last glacial cycle and suggest inclusion of mis 5c together with the eemian mis 5e in an interglacial complex

age and depositional environment of the xiaheyan insect fauna embedded in marine black shales early pennsylvanian china abstract the early pennsylvanian xiaheyan entomofauna ningxia china is among the earliest assemblages of winged insects known so far and therefore provides an essential input on deciphering the early diversification of this group despite its evolutionary significance both the age and depositional environment remained poorly constrained here we present high resolution documentation of litho and biofacies biostratigraphy and geochronology of the up to 100 m thick type section accordingly the insect bearing strata are of latest bashkirian latest duckmantian to middle moscovian bolsovian age the sediments lithostratigraphically assigned to the yanghugou fm represent a regressional marine sequence formed at the southern margin of the qilian inland sea intercalations of crevasse channels and splays that laterally interlock with marine black shales and bioclastic limestones point to deposition in an interdelta bay ground touching waves provoked the erosion of muds at shallow depths leading to mass mortalities among mollusc communities due to rising anoxia turbidity and water turbulence in addition bottom currents transported mud intraclasts towards the basin where sinking insects that reached the bay via winds and surface currents were buried sub contemporaneously with bivalves below the storm wave base observed differences in insect preservation and assemblage composition across the sequence are found to correlate with lithology and are best explained by distance from land and the action of events inducing insect carcasses to sink such as storms the proposed taphonomic model represents a new fossilization pathway from land to sea and provides new directions for prospecting paleozoic deposits in the search for insects

yangquanoxylon miscellum gen nov et sp nov a gymnospermous wood from the upper pennsylvanian lower permian taiyuan formation of yangquan city shanxi province with reference to the palaeoclimate in north china a silicified gymnospermous wood yangquanoxylon miscellum gen nov et sp nov is described from the upper pennsylvanian lower permian taiyuan formation yangquan city shanxi province north china the pycnoxylic wood is composed of thick walled tracheids and thin walled rays it is characterized by mixed radial tracheid pits uniseriate and homogeneous rays occurrence of scalariform radial pitting and various types of cross field pitting there are four types of cross field pitting in y miscellum gen nov et sp nov including simple taxodioid phyllocladoid and araucarioid the absence of growth rings within fossil woods described here and reported previously from north china suggests a humid climate with minimal precipitation variations during the late pennsylvanian early permian

visual and infrared observations of wind streaks on mars abstract estimation of surface properties and physical setting of three common martian wind streak types bright dark and splotch related provides constraints on models of the formation and variability of streaks bright streaks form independently of surface properties other than local topography this is consistent with their formation being due to deposition of atmospheric dust in the lee of topographic features although they are widespread on mars dark streaks are noted as variable only in regions near 30 s latitude and elevations between 3 and 7 km and are associated with dark surfaces that have relatively high thermal inertias splotch related streaks occur at elevations between 0 and 6 km and in regions of relatively high thermal inertia splotch related streaks occur near the boundaries of thermally defined regions such as the south polar cap and other areas of either low or high thermal inertia these thermal conditions are responsible for the production of surface winds which form and modify these streaks the source of sidements which form splotch related streaks varies from dunes to well indurated stratified deposits regional studies of the various types in syrtis major syria planum claritas fossae oxia palus mesogea and pettit craters and noachis confirm that the correlations found at the global level occur at regional scales

high resolution pollen analysis of tundra polygons from the north slope of alaska modern and fossil pollen analyses have established the local vegetation succession and landscape evolution along the meade river near atqasuk alaska three data sets were analyzed 1 a 142 cm long peat deposit on the exposed river bluff face 2 a short 13 cm peat monolith from the near surface sediment and 3 a modern data set of surface samples collected along a transect representative of a geomorphic gradient of low center transitional and high center polygons pollen microfossil assemblages changed significantly along this gradient detailed analysis of the short pollen profile shows successional vegetation changes over the last 250 years the long profile a 9400 year record of past vegetation indicates that initially the site was covered by shallow lakes eolian activity had a substantial effect on sediment deposition but a period of rapid peat growth from 8500 to 5000 14c year b p is coincident with increased vegetation cover of mixed grass shrub tundra following this period peat growth slowed and shrub vegetation was replaced by tussock forming sedge vegetation

limnological controls on stable isotope records of late holocene palaeoenvironment change in sw greenland a paired lake study stable isotope records are increasingly being used in palaeoenvironmental studies of arctic lakes here we compare stable isotope and elemental records 13c 15n c n with high resolution xrf derived geochemical and colour data from low arctic lakes ss1220 and ss85 in southwest greenland lake ss1220 sediments are laminated gyttja whereas ss85 consist of homogeneous gyttja both records cover the last c 5000 years 13c and carbon content suggest that organic matter in both lakes is predominantly autochthonous the c n variability ranging between 11 and 15 is interpreted to be a function of nitrogen deficiency which is further supported by 15n values at ss1220 falling close to atmospheric 15natmosphere although some changes in the geochemical stratigraphies presented here can be related to regional environmental change i e hydrology effective precipitation aeolian activity these effects are filtered through the lake catchments these changes alter the nutrient supply and hence lake productivity which appear to be the primary controls on the stable isotope data we suggest that information of past environmental change can only be gained from the stable isotope composition of lake sediments when there is a reasonable understanding of limnological processes and records may be lake specific

early permian coal forming floras preserved as compressions from the wuda district inner mongolia china four different compression impression floras are preserved in only 4 32 m of the geologic section in the early permian shanxi formation of the wuda district of inner mongolia northwestern china these floras represent four different plant communities and landscapes that followed each other in time the oldest flora was rooted in sandy clay and initiated peat accumulation that lead to the formation of the lower coal seam this seam is 230 cm thick and overlain by a 66 cm thick volcanic tuff that preserves a second different flora that grew on the peat at the time of the ash fall standing stems and large plant parts are present the upper part of the tuff is rooted by a single species of lycopsid the third flora again initiating peat accumulation on top of this second seam of 120 cm thickness rests a roof shale deposited as mud in a shallow lake the formation of which was responsible for the cessation of peat deposition this fourth flora represents the plants growing around the lake on clastic substrate four different environments followed each other in this locality over a geologically short time span and each time conditions prevailed to preserve plant macrofossils three of these floras represent peat forming plant communities of essentially the same time interval this demonstrates the great variability of vegetation and landscapes in the tropical cathaysian realm of the late paleozoic

carbonaceous particles reveal that late holocene dust causes the dark region in the western ablation zone of the greenland ice sheet a dark region in the western ablation zone of the greenland ice sheet is caused by outcropping ice layers that contain more dust than the surrounding brighter ice these higher amounts of dust were deposited in the accumulation zone of the ice sheet and travelled with the ice to the ablation zone to deduce the period and the causes of this higher dust deposition carbonaceous particles in ice samples from the dark region and from brighter reference ice were analysed and used for dating samples including ice from directly below the surface contain high amounts of modern organic carbon probably from microorganisms on the ice surface deeper samples reveal low amounts of carbonaceous particles which are originally deposited in the accumulation zone the amount of outcropping carbonaceous particles in the dark region seems significantly higher than in the reference ice one of the samples that contained material initially deposited in the accumulation zone was dated and revealed late holocene ages coinciding with a period of enhanced eolian activity in the nearby tundra therefore variable eolian activity during the holocene effected dust fluxes towards the ice and hence leads to albedo variations in the present ablation zone of the ice sheet

exotic pollen as an indicator of variable atmospheric circulation over the labrador sea region during the mid to late holocene variability in the abundance of exotic non native pollen in sediment cores has long been considered as a potential proxy for changing atmospheric circulation but the difficulty of gaining sufficient total exotic pollen and the incomplete under standing of atmospheric pollen transport patterns has hindered its application in light of recent advances in the study of pollen transport we present an exotic pollen record from two fjord sediment cores taken from the west placentia bay newfoundland and east narsaq sund greenland labrador sea as a basis for studying variations in regional atmospheric circulation the two cores cover the last ca 5500 years and indicate a shift in dominant spring summer air masses at ca 2000 southern greenland and 3000 cal a bp newfoundland transporting reduced concentrations of pollen from southerly and south westerly vegetation zones this may suggest a shift away from more dominantly zonal atmospheric circulation a feature of positive north atlantic oscillation years to more frequent meridional circulation these results support sea ice sea surface temperature proxy reconstructions from newfoundland investigated as part of the same project which also suggest increased winter atmospheric circulation during the early part of the time period studied in this region more positive north atlantic oscillation years and therefore more zonal atmospheric circulation are associated with increased atmospheric circulation in both the winter and the summer seasons copyright 2011 john wiley sons ltd