hierarchal genetic stratigraphy a framework for paleoceanography a detailed genetic stratigraphic framework for paleoceanographic studies can be derived by describing correlating interpreting and predicting stratigraphic sequences relative to a hierarchy of their constituent time stratigraphic transgressive regressive units t r units t r unit hierarchies are defined and correlated using lithostratigraphic and paleoecologic data but correlations can be enhanced or checked tested to confirm or deny with objective biostratigraphic magnetostratigraphic or chemostratigraphic data such chronostratigraphies can then be bracketed by radiometric ages so that average periodicities for t r units can be calculated and a hierarchal geochronology derived t r units are inferred to be the net depositional result of eustatic cycles of sea level change and can be differentiated from autocyclic deepening shallowing units because the latter are noncorrelative intrabasinally boundaries between t r units are conformable or unconformable genetic surfaces of two types transgressive surfaces and climate change surfaces the latter are useful for correlating minor transgressive phases through nonmarine intervals thereby deriving information linking paleoclimatic and paleoceanographic processes permo carboniferous sequences can be analyzed relative to a hierarchy of six scales of genetic t r units having periodicities of 225 300 m y first order 20 90 m y second order 7 13 m y third order 0 6 3 6 m y fourth order 300 500 10 years fifth order and 50 130 10 years or less sixth order paleogeographic maps for the time of maximum transgression transgressive apex of successive fifth order t r units 5 25 m thick in the glenshaw formation upper pennsylvanian northern appalachian basin delineate delta lobes embayments islands and linear seaways relative extent of marine inundation on the fifth order maps was used to delineate fourth order t r units and the fourth order t r units constitute the transgressive half of a third order t r unit this third fourth and fifth order hierarchy is correlated more than 1200 km 750 miles to the western interior basin and is confirmed with limited objective biostratigraphy

pennsylvanian uplands were forested by giant cordaitalean trees the precise timing of when upland terrains first became forested is highly controversial pennsylvanian palynoflora and megaflora transported into marine highstand deposits imply that emergent topographic highs may have supported cordaitalean forests the discovery of a new pennsylvanian bolsovian plant assemblage in southwest newfoundland confirms this hypothesis and allows the architecture of these upland trees to be reconstructed in detail the assemblage includes several hundred calcareously permineralized stumps trunks and branches and represents the remains of shallowly rooted cordaitalean trees that were 48 5 m high when mature the fossils occur in alluvial conglomerates that constitute a 10 km diameter outlier on the margins of the paleoequatorial variscan foreland the paleogeographic setting together with plant taphonomic inferences strongly indicate that these giant trees were transported from nearby upland alluvial plains and deposited in an elevated intermontane basin this interpretation is supported by analysis of rootstock morphology which implies tree growth in thin soils consistent with an alluvial gravel substrate this improved understanding of pennsylvanian upland forests has important implications for geochemical modeling of the global carbon cycle

incised channel fills containing conifers indicate that seasonally dry vegetation dominated pennsylvanian tropical lowlands the idea that the pennsylvanian tropical lowlands were temporally dominated by rainforest i e the coal forest is deeply ingrained in the literature here we challenge two centuries of research by suggesting that this concept is based on a taphonomic artifact and that seasonally dry vegetation dominated instead this controversial finding arises from the discovery of a new middle pennsylvanian moscovian fossil plant assemblage in southeast illinois united states the assemblage which contains xerophytic walchian conifers occurs in channels incised into a calcic vertisol below the baker coal these plants grew on seasonally dry tropical lowlands inferred to have developed during a glacial phase this xerophytic flora differs markedly from that of the typical clubmoss dominated coal forest developed during deglaciation events although preserved only very rarely we argue that such xerophytic floras were temporally as dominant and perhaps more dominant than the iconic coal forests which are overrepresented in the fossil record due to taphonomic megabias these findings require the iconography of pennsylvanian tropical lowlands to be redrawn

surface mass balance observations and automatic weather station data along a transect near kangerlussuaq west greenland surface mass balance data from the kangerlussuaq transect k transect located on the western part of the greenland ice sheet near 678n are presented the series covers the period 1990 2003 and is the longest series of surface mass balance measurements in greenland the surface mass balance measurements cover an altitude range of 390 1850m and show a linear increase of the specific mass balance with a mass balance gradient of 3 7 10 3 mm 1 and a mean equilibrium line altitude of 1535ma s l interannual variability shows a weak 4yearly periodicity in addition to the surface mass balance data automatic weather station data at an elevation of approximately 1010m are available for the period 1997 2002 these data are used to explain observed surface mass balance anomalies over the same 5years it is shown that variations in shortwave radiation dominate interannual variability the mean annual cycle of temperature is characterized by a maximum in summer around the melting point leading to a mean summer outgoing longwave radiation of approximately 314wm 2 the mean annual cycle in wind speed shows a maximum in winter on average around 8ms 1 and a minimum in summer on average around 5ms 1 which is characteristic for a katabatic forcing during summer the net radiation is on average about 61wm 2 which is used for ice melting at a rate of typically 2cmw e d 1 net radiation contributes 84 of the total energy used for summer melting averaged over the 5years

warming glacier melt and surface energy budget from weather station observations in the melville bay region of northwest greenland the glaciers in the melville bay region of northwest greenland have shown a mean retreat since the earliest observations at the beginning of the 20th century the largest steenstrup gletscher has retreated 20 km partly during the period of atmospheric cooling 1940 80 melville bay air temperature observations starting in 1981 indicate a regional change of 0 208 ca 1 this exceeds the warming on the east coast of greenland confirming the west coast to be a region of relatively large change also in a global perspective the largest temperature increase is observed in the winter months 0 3 0 48 ca 1 results from a 4 year 2004 08 net ablation record obtained by an automatic weather station aws near the calving front of steenstrup gletscher show an ablation rate that is relatively low for a low elevation position on the greenland ice sheet 2 4 m ice equivalent per year a first order estimate from positive degree day totals suggests that net ablation has roughly doubled since the 1980s a surface energy and mass balance model is applied to the steenstrup aws data to quantify the energy flux contributions to surface melt solar radiation is the main source for melt energy but due to shortwave radiation penetration into the ice only one third of the melt takes place at the glacier surface nearly two thirds occurs within the upper ice layers

effects of clouds on surface melting of laohugou glacier no 12 western qilian mountains china we analyzed a 2 year time series of meteorological data january 2011 december 2012 from three automatic weather stations on laohugou glacier no 12 western qilian mountains china air temperature humidity and incoming radiation were significantly correlated between the three sites while wind speed and direction were not in this work we focus on the effects of clouds on other meteorological parameters and on glacier melt on an average 18 of top of atmosphere shortwave radiation was attenuated by the clear sky atmosphere and clouds attenuated a further 12 most of the time the monthly average increases in net longwave radiation caused by clouds were larger than decreases in net shortwave radiation but there was a tendency to lose energy during the daytime when melting was most intense air temperature and wind speed related to turbulent heat flux were found to suppress glacier melt during cloudy periods while increased water vapor pressure during cloudy days could enhance glacier melt by reducing energy loss by latent heat from these results we have increased the physical understanding of the significance of cloud effects on continental glaciers

paleoclimate controls on late paleozoic sedimentation and peat formation in the central appalachian basin u s a abstract in the central appalachian basin at least two major climate changes affected sedimentation during the late paleozoic stratigraphically these two changes are indicated by the distribution of coal beds the variation in coal quality and the variation in rock lithologies in latest mississippian or earliest pennsylvanian time the climate changed from dry seasonal tropical to ever wet equable tropical the equable climate prevailed into the middle pennsylvanian influencing the morphology and geochemistry in peat forming environments many of the peat deposits which formed under the equable climate were probably domed raised bogs low concentrations of dissolved solids in peat formation water resulted in low buffering capacity organic acids caused acidic ph another climate change occurred in late middle pennsylvanian time when evapopation periodically exceeded rainfall resulting in an increase of both dissolved solids and ph 4 to 7 in surface and near surface water throughout the remainder of the pennsylvanian the surfaces of peat deposits were probably planar not domed water in peat forming and other depositional environments became more nearly neutral the coal beds derived from these peats are highly variable in both ash and sulfur contents drier or more seasonal climates are also indicated by sequences of 1 calcareous sandstone and shale 2 nonmarine limestone that shows shallow water and subaerial exposure features and 3 calcareous paleosols that have caliche characteristics our data and observations indicate that physical depositional environment models for the origin of coal do not adequately explain variations in mineral matter content and composition in commercial quality coal beds in the central appalachian basin stratigraphic variation in mineral matter in coal beds and in syngenetic and early diagenetic minerals in rocks associated with the coal beds appears to be better explained by changes in geochemical conditions of nonmarine sedimentation paleoclimate was a principle control on these geochemical conditions

response of the longwave radiation over melting snow and ice to atmospheric warming parameterizing the incoming longwave radiation l in terms of the fourth power of the absolute temperature at the reference height is used in glaciology for several purposes in this paper the validity ofthis kind ofparameterization is investigated for the greenland ice sheet both by observations and by numerical simulation with a meso scale model it is found that such a parameterization severely underestimates the increase of l in response to large scale warming in an area where surface melting is important this is explained by the systematic influence that is exerted on the shape of the temperature profiles by surface melting

the ablation zone in northeast greenland ice types albedos and impurities ice types albedos and impurity content are characterized for the ablation zone of the greenland ice sheet in kronprinz christians land 80 n 24 w along this ice margin the width of the ablation zone is only about 8 km the emergence and melting of old ice in the ablation zone creates a surface layer of dust that was originally deposited with snowfall high on the ice sheet this debris cover is augmented by locally derived wind blown sediment subsequently the surface dust particles often aggregate together to form centimetre scale clumps that melt into the ice creating cryoconite holes the debris in the cryoconite holes becomes hidden from sunlight raising the area averaged albedo relative to surfaces with uniform debris cover spectral and broadband albedos were obtained for snow ice hummocks debris covered ice cryoconite studded ice and barren tundra surfaces broadband ice albedos varied from 0 2 for ice with heavy loading of uniform debris to 0 6 for ice hummocks with cryoconite holes the cryoconite material itself has albedo 0 1 when wet areal distribution of the major surface types was estimated visually from a transect video as a function of distance from the ice edge 330 m a s l ablation rates were measured along a transect from the ice margin to the slush zone 8 km from the margin 550 m a s l traversing both pleistocene and holocene ice ablation rates in early august averaged 2 cm d 1 impurity concentrations were typically 4 3 mg l 1 in the subsurface ice surface concentrations were about 16 g m 2 on surfaces with low impurity loading and heavily loaded surfaces had concentrations as high as 1 4 kg m 2 the mineralogical composition of the cryoconite material is comparable with that of the surrounding soils and with dust on a snowdrift in front of the ice margin implying that much of the material is derived from local sources a fine mode clay is present in the oldest ice but not in the nearby soil suggesting that its origin is from wind deposition during pleistocene glaciation

variations of ablation albedo and energy balance at the margin of the greenland ice sheet kronprins christian land eastern north greenland a meteorological and glaciological experiment was carried out in july 1993 at the margin of the greenland ice sheet in kronprins christian land eastern north greenland within a small area about 100 m 2 daily measurements were made on ten ablation stakes fixed in light and dark ice and were compared to each other simultaneously the components of the energy balance including net radiation sensible heat flux latent heat flux and conductive heat flux in the ice were determined global radiation longwave incoming radiation and albedo were measured and longwave outgoing radiation was calculated by assuming that the glacier surface was melting sensible and latent heat fluxes were calculated from air temperature humidity and wind speed conductive heat flux in the ice was estimated by temperature profile measurements in the uppermost ice layer net radiation is the major source of ablation energy and turbulent fluxes are smaller energy sources by about three times while heat flux into the ice is a substantial heat sink reducing energy available for ice melt albedo varies from 0 42 to 0 56 within the experimental site and causes relatively large differences in ablation at stakes close to each other small scale albedo variations should therefore be carefully sampled for large scale energy balance calculations

glacial eustatic base level climatic model for late middle to late pennsylvanian coal bed formation in the appalachian basin abstract late middle late pennsylvanian middle allegheny and lower conemaugh marine units in the appalachian basin represent the distal edges of glacial eustatic marine incursions of the midcontinent sea onto the detrital apron of the appalachian highlands because these marine units typically overlie coal beds the main environment of formation of this type of coal bed appears to have been that of a coastal swamp migrating ahead of transgression as base level rose the water table continually rose and the swamp was further nourished and surrounding vegetation kept thick enough to inhibit detrital influx by rainfall from the expanding nearby source of moisture even in parts of the appalachian cyclic succession with no marine units upper allegheny monongahela dunkard the coal beds rep esent the wettest part of the climate cycle of cecil 1990 sandwiched between detrital units representing seasonal wet dry climates when sediment was most readily mobilized and antipodal to nonmarine limestones representing the driest climates throughout this time the appalachian basin was in the center of the tropical zone of a nearly accreted megacontinent quite distant 4000 km from permanent oceanic sources of moisture climate modeling without considering inland seas or orographic effects on winds shows that the tropical zone of such a large land mass would have suffered from a severe deficit in rainfall and soil moisture although further modeling shows that the appalachian orogenic highlands would have drawn in moisture to ncrease rainfall in their vicinity they also may have impeded the normal westward flow of moisture laden easterly winds the western source for enough moisture to form coal beds was most likely the north american midcontinent sea during major highstand this sea would have covered about 2 million km2 and provided both high base level and abundant nearby moisture for enough continual rainfall to keep the coastal peat swamps widespread fresh and relatively detritus free in the appalachian basin in contrast during major lowstand it would have covered only about 200 000 km2 with its shoreline about 1500 km away and it apparently provided less consistent moisture to the appalachian basin then because most nonmarine limestones and paleosols formed there during the e times contain evidence of drier climates therefore upper allegheny monongahela and dunkard coal beds most probably formed when the midcontinent sea was approaching highstand and stood just west of the presently preserved outcrop thus they likely represent the coastal lowland equivalent of a marine unit at highstand farther west this constrained time of peat formation and preservation in a variety of coastal environments prior to and during marine highstand is responsible for the discrete and widespread nature of the coal bed interval in a typical depositional cycle or cyclothem a pattern that stands in contrast to the complicated relations of overlying and underlying detrital units which reflect the segregation of sand and mud into a complex mosaic of local deltaic and ter estrial subenvironments that developed when sea level rainfall and the water table were lower

surface radiation balance in the ablation zone of the west greenland ice sheet 1 we present 4 years of radiation observations and derived cloud properties from the ablation zone of the west greenland ice sheet 67 n data were collected using three automatic weather stations located at 6 38 and 88 km from the ice sheet margin at elevations of 490 1020 and 1520 m asl this part of greenland is characterized by a 150 km wide tundra a 100 km wide ablation zone and an average equilibrium line altitude of 1500 m asl at the lowest station snow is redistributed by the wind in crevasses and gullies leading to very little measured winter accumulation as a result glacier ice albedo 0 55 is at the surface throughout the melting season at 1020 m asl the winter snow cover typically disappears in mid to end june at 1520 m asl superimposed ice briefly reaches the surface at the end of the ablation season the combined effect of decreasing surface albedo and increasing cloud optical thickness as summer progresses causes absorbed shortwave radiation to peak in june at low elevations but progressively later at higher elevations incoming longwave radiation peaks in august in response to increased cloud optical thickness and heating of the atmosphere over the snow and ice free surroundings the ice sheet margin experiences continuous melting in june july and august this limits the emission of longwave radiation causing net longwave radiation to peak in august further enhancing melt the sum of these effects is that summer net radiation increases sharply toward the ice sheet margin to resolve this correctly requires high resolution climate models in the order of 10 km or better

greenland ice sheet contribution to 21st century sea level rise as simulated by the coupled cesm2 1 cism2 1 the greenland ice sheet gris mass balance is examined with an earth system ice sheet model that interactively couples the gris to the broader earth system the simulation runs from 1850 to 2100 with historical and ssp5 8 5 forcing by the mid 21st century the cumulative gris contribution to global mean sea level rise slr is 23 mm during the second half of the 21st century the surface mass balance becomes negative in all drainage basins with an additional slr contribution of 86 mm the annual mean gris mass loss in the last two decades is 2 7 mm sea level equivalent sle year 1 the increased slr contribution from the surface mass balance 3 1 mm sle year 1 is partly offset by reduced ice discharge from thinning and retreat of outlet glaciers the southern gris drainage basins contribute 73 of the mass loss in mid century but 55 by 2100 as surface runoff increases in the northern basins

changing patterns of pennsylvanian coal swamp vegetation and implications of climatic control on coal occurrence abstract improved regional and interregional stratigraphic correlations of pennsylvanian strata permit comparisons of vegetational changes in euramerican coal swamps the coal swamp vegetation is known directly from in situ coal ball peat deposits from more than 65 coals in the united states and europe interpretations of coal swamp floras on the basis of coal ball peat studies are extended to broader regional and stratigraphic patterns by use of coal palynology objectives of the quantitative analyses of the vegetation in relation to coal are to determine the botanical constituents at the peat stage and their environmental implications for plant growth and peat accumulation morphological and paleoecological analyses provide a basis for deducing freshwater regimes of coal swamps changes in composition of pennsylvanian coal swamp vegetation are quire similar from one paralic coal region to another and show synchrony that is attributable to climate paleobotany and paleogeography of the euramerican province indicate a moist tropical paleoclimate rainfall runoff and evapotranspiration were the variable climatic controls in the distribution of coal swamp vegetation peat accumulation and coal resources in relative terms of climatic wetness the pennsylvanian period is divisible into five intervals which include two relatively drier intervals that developed during the lower middle and middle upper pennsylvanian transitions the climate during early pennsylvanian time was moderately wet and the median in moisture availability early middle pennsylvanian was drier probably seasonally dry wet late middle pennsylvanian was the wettest in the midcontinent early late pennsylvanian was the driest and late late pennsylvanian was probably the wettest in the dunkard basin the five climatic intervals represent a general means of dividing coal resources within each region into groups with similar botanical constituents and environments of peat accumulation regional differences in basinal geology and climate were significant variables but the synchronous control of paleoclimate was of primary importance

pennsylvanian tropical rain forests responded to glacial interglacial rhythms pennsylvanian tropical rain forests flourished during an icehouse climate mode although it is well established that milankovitch band glacial interglacial rhythms caused marked synchronous changes in pennsylvanian tropical climate and sea level little is known of vegetation response to orbital forcing this knowledge gap has now been addressed through sequence stratigraphic analysis of megafloral and palynofloral assemblages within the westphalian d cantabrian sydney mines formation of eastern canada this succession was deposited in a low accommodation setting where sequences can be attributed confidently to glacio eustasy results show that long lived low diversity peat mires dominated by lycopsids were initiated during deglaciation events but were mostly drowned by rising sea level at maximum interglacial conditions only upland coniferopsid forests survived flooding without significant disturbance mid to late interglacial phases witnessed delta plain progradation and establishment of high diversity mineral substrate rain forests containing lycopsids sphenopsids pteridosperms cordaites and tree ferns renewed glaciation resulted in sea level fall paleovalley incision and the onset of climatic aridity glacial vegetation was dominated by cordaites pteridosperms and tree ferns hydrophilic lycopsids and sphenopsids survived in paleovalley refugia findings clearly demonstrate the dynamic nature of pennsylvanian tropical ecosystems and are timely given current debates about the impact of quaternary glacial interglacial rhythms on the biogeography of tropical rain forest

walchian conifers from the mid late pennsylvanian conemaugh group in the appalachian basin stratigraphic and depositional context and paleoclimatic significance abstract walchian conifers are indicators of seasonally dry habitats of the euramerican subtropics and tropics and are of considerable value in tracking both short term and long term pennsylvanian permian paleoclimatic changes in central pangea walchian conifer macrofossils first appeared in north america during the middle pennsylvanian but are rare in central pangean coal basins until the permian an abrupt climate change occurred near the desmoinesian missourian boundary that was characterized by global warming stronger seasonality and shorter wet phases this change coincided with the regional extinction of most tree lycopsids and the appearance of widespread high chroma calcic vertisols and aridisols only four occurrences of walchia have been reported from the pennsylvanian of the appalachian basin 1 7 11 mine of eastern ohio 2 rennersville in southwest pennsylvania and 3 charleston and 4 cedar run both in southern west virginia this paper uses recently acquired outcrop data to more fully document and reevaluate the depositional and stratigraphic context of the west virginia assemblages and their paleoclimatic and paleogeographic implications the cedar run walchia assemblage occurs in olive mudshale of an abandoned fluvial channel fill 15 8 16 9 m above the base of the ames limestone indicating an early virgilian age it consists of compressions and impressions of branches and branchlets of walchia lepidophylloides cordaites and rare neuropteroid pinnules the channel fill at this location is a component of the grafton sandstone incised valley fill previously described from the study area correlation of paleosol bounded marine cored cyclothems in the study area with their nonmarine cyclothem equivalents at charleston west virginia indicates the walchia previously reported at the mahoning coal horizon occurs between the brush creek and bakerstown coals and is therefore missourian not late desmoinesian and similar to the revised age for the 7 11 mine walchia reported from eastern ohio late pennsylvanian upland or dryland conifer communities were comprised of walchia cordaites and sigillaria which produced a forest with seed ferns as an understory the cedar run assemblage was probably transported into the valley from adjacent well drained coastal plain uplands formed during valley incision and deposited within the early transgressive systems tract it is also possible that walchia expanded into the valleys when drainage became ephemeral during more arid climatic phases the revised correlations of appalachian basin walchia horizons indicate their appearance closely followed rather than predated the abrupt climate change and extinctions at the desmoinesian missourian boundary

record of glacial eustatic sea level fluctuations in complex middle to late pennsylvanian facies in the northern appalachian basin and relation to similar events in the midcontinent basin abstract pennsylvanian cycles in the northern appalachian basin nab were historically considered to result from delta lobe switching and more recently from sea level fluctuation with sandy deltas prograding during highstand these interpretations are revised using new data from cores and outcrop exposures thick 5 m channel deposits with a marked erosion surface at their base cutting down across previous cycles are re interpreted as incised valley fill ivf deposits in paleovalleys because the basal erosion surfaces are widespread and thus reflect a record of lowstand most common are simple paleovalleys that contain mainly sandy fluvial deposits compound paleovalleys with sequence boundaries above the basal erosion surface contain terrestrial estuarine and marine deposits early to late highstand deposits in interfluvial parts of the cycles are dominated by shale and mudstone with paleosols coals and local non marine limestone which reflect floodbasin to lacustrine conditions these reinterpretations are applied to previously and newly recognized cycles in ascending order upper kittanning lower freeport upper freeport leader new upper freeport piedmont new mahoning mason interval locally includes upper new galilee in the north and brush creek across a 300 km arc in the northern appalachian basin these deposits accumulated in a high shelf setting that experienced fewer marine transgressions and were interrupted by more frequent exposure and downcutting in contrast to the thicker and more complete succession with more numerous marine units in the midcontinent magnitudes of highstand transgressions into this basin deduced from the up dip extent of marine and brackish fossil assemblages were greatest for the brush creek less so for the upper kittanning and mahoning and least for the lower freeport upper freeport leader piedmont and mason the anomalous basin wide fresh water roofshales and equivalents of the upper freeport coal may reflect ponding of fresh water to the north by an elevated area that prevented marine encroachment at the southern opening of the basin along the kentucky ohio border maximum thicknesses of ivf deposits in each cycle are used as a proxy for estimating the minimum depth of lowstand incision preceding transgression while the thickness of ivf deposits in most cycles ranges from 6 to 20 m the two thickest are 30 m thick one associated with the pre mahoning paleovalley and the other with the immediately post mahoning paleovalley the extent of transgression of each cycle in the nab is roughly equivalent to those of their age correlative major marine cyclothems pawnee through swope in the midcontinent moreover the amount of incision between them is also roughly equivalent to the amount of regression between each of the roughly coeval cyclothems in the midcontinent with the deepest incisions in the nab pre mahoning and post mahoning corresponding to the greatest southward withdrawals of the sea in the midcontinent memorial and seminole hepler during this same interval

surface melt induced acceleration of greenland ice sheet flow ice flow at a location in the equilibrium zone of the west central greenland ice sheet accelerates above the midwinter average rate during periods of summer melting the near coincidence of the ice acceleration with the duration of surface melting followed by deceleration after the melting ceases indicates that glacial sliding is enhanced by rapid migration of surface meltwater to the ice bedrock interface interannual variations in the ice acceleration are correlated with variations in the intensity of the surface melting with larger increases accompanying higher amounts of summer melting the indicated coupling between surface melting and ice sheet flow provides a mechanism for rapid large scale dynamic responses of ice sheets to climate warming

high precision u pb zircon age calibration of the global carboniferous time scale and milankovitch band cyclicity in the donets basin eastern ukraine 1 high precision id tims u pb zircon ages for 12 interstratified tuffs and tonsteins are used to radiometrically calibrate the detailed lithostratigraphic cyclostratigraphic and biostratigraphic framework of the carboniferous donets basin of eastern europe chemical abrasion of zircons use of the internationally calibrated earthtime mixed u pb isotope dilution tracer and improved mass spectrometry guided by detailed error analysis have resulted in an age resolution of 0 05 or 100 ka for these carboniferous volcanics this precision allows the resolution of time in the milankovitch band and confirms the long standing hypothesis that individual high frequency pennsylvanian cyclothems and bundles of cyclothems into fourth order sequences are the eustatic response to orbital eccentricity 100 and 400 ka forcing tuning of the fourth order sequences in the donets basin to the long period eccentricity cycle results in a continuous age model for the middle to late pennsylvanian moscovian kasimovian ghzelian strata of the basin and their record of biological and climatic changes through the latter portion of the late paleozoic ice age detailed fusulinid and conodont zonations allow the export of this age model to sections throughout euramerica additional ages for mississippian strata provide among the first robust radiometric calibration points within this subperiod and result in variable lowering of the base ages of its constituent stages compared to recent global time scale compilations

a new high resolution digital elevation model of greenland fully validated with airborne laser altimeter data a new digital elevation model of the greenland ice sheet and surrounding rock outcrops has been produced at 1 km postings from a comprehensive suite of satellite remote sensing and cartographic data sets height data over the ice sheet were mainly from ers 1 and geosat radar altimetry these data were corrected for a slope dependent bias that had been identified in a previous study the radar altimetry was supplemented with stereophotogrammetric data sets synthetic aperture radar interferometry and digitized cartographic maps over regions of bare rock and where gaps in the satellite altimeter coverage existed the data were interpolated onto a regular grid with a spacing of 1 km the accuracy of the resultant digital elevation model over the ice sheet was assessed using independent and spatially extensive measurements from an airborne laser altimeter that had an accuracy of between 10 and 12 cm in a comparison with the laser altimetry the digital elevation model was found to have a slope dependent accuracy ranging from 1 04 1 98 m to 0 06 14 33 m over the ice sheet for a slope range of 0 0 1 0 the mean accuracy over the whole ice sheet was 0 33 6 97 m over the bare rock areas the accuracy ranged from 20 to 200 m dependent on the data source available the new digital elevation model was used as an input data set for a positive degree day model of ablation the new elevation model was found to reduce ablation by only 2 compared with using an older 2 5 km resolution model which suggests that resolution induced errors in estimating ablation are no longer important

modeling surface roughness solar ablation feedback application to small scale surface channels and crevasses of the greenland ice sheet surface roughness enhances the net ablation rate associated with direct solar radiation relative to smooth surfaces because roughness allows solar energy reflected from one part of the surface to be absorbed by another part in this study we examine the feedback between solar radiation driven ablation and growth of surface roughness on the greenland ice sheet using a numerical model of radiative transfer our experiments extend previous work by examining 1 the effects of diurnal and seasonal variation of solar zenith angle and azimuth relative to incipient roughness features 2 the evolution of roughness geometry in response to radiatively driven ablation and 3 the relative solar energy collection efficiencies of various roughness geometries and geographic locations and orientations a notable result of this examination is that the time evolution of the aspect ratio of surface features under solar driven ablation collapses onto a roughly universal curve that depends only on latitude not the detailed shape of the feature the total enhancement of surface melt relative to a smooth surface over a full ablation season varies with this ratio and this dependence suggests a way to parameterize roughness effects in large scale models that cannot treat individual roughness features overall our model results suggest that surface roughness at the latitudes spanned by the greenland ice sheet tends to dissipate as the ablation season progresses

correlation of carboniferous strata using a hierarchy of transgressive regressive units carboniferous strata can be described interpreted and correlated using six scales of allocyclic transgressive regressive t r units these t r units are inferred to be the net result of deposition during cycles of sea level change all pennsylvanian and lower permian strata constitute one second order t r unit or synthem the pennsylvanian system contains third fourth fifth and sixth order t r units that can be correlated across both marine and nonmarine facies in the appalachian basin this permits differentiation of allocyclic t r units from autocyclic t r units or fluvial autocyclic units the hierarchical approach is also useful for predicting the location of marine horizons coals claystones and various types of stratigraphic breaks a hierarchical scheme of allocyclic t r units could be combined with biostratigraphic radiometric and magnetostratigraphic data to form a practical chronostratigraphic framework for the carboniferous

pennsylvanian deposystems and paleoclimates of the appalachians abstract central appalachian basin rocks indicate major changes in source areas base level and climate for late mississipian through late pennsylvanian time through time dominant source areas change from craton and northeastern orogen to southeastern orogenic mountains the mississipian pennsylvanian uncomformity correlates with a worldwide eustatic event early pennsylvanian rocks contrast markedly with underlying mississippian mauch chunk redbeds in composition and texture yet the source areas and alluvial plain setting were similar seas transgressed northeastward during middle and earliest late pennsylvanian time along axes of the pocahontas and dunkard basins while fluvial dominant deltas prograded northwestward this progradation 1 progressively extended the coastal plain 2 provided coastal swamp environments for peat accumulation and 3 eventually cut off the narrow seaway of dunkard basin from the central interior by late pennsylvanian and transformed it into a large shallow freshwater lake redbeds calcium carbonate concretions and gilgai paleosol structures of late mississippian and late pennsylvanian rocks suggest seasonally dry tropical climate whereas the lithologies of the earlier pennsylvanian rocks are indications of everwet tropical climates with their quartz rich fluvial sandstones high quality coals and aluminum rich clay deposits streams change from predominantly bedload to suspended load generally from early to late pennsylvanian in response to changes in paleoslope gradient distance from source area unvegetated highland and change from everwet to intermittently dry tropical climate greater dryness is suggested for increased alkaline conditions observed in paleosols carbonates and coal beds of late pennsylvanian time but sufficiently wet to prevent evaporite deposition

confirmation of carboniferous clastic swamp communities tropical lowlands dominated by arborescent lycophytes are the principal foci for our understanding of carboniferous peat and non peat accumulating coastal swamps1 2 suggested palaeoeco logical interpretations of various lycophytes and accessory vegetation have been based on transported compression assemblages3 4 and palynomorphs5 6 or in situ permineralized peats7 where transported macrodetritus resulting in compression assemblages is used to reconstruct past vegetational patterns taphonomic factors tend to bias the preserved flora8 11 taken alone or out of depositional context the heterogeneity of an assemblage most probably bears little or no relationship to that of the original contributing communities gastaldo9 suggests that reconstructions should be based on the autecology of erect in situ plants because with peats permineralized in situ precise resolution in time of laterally equivalent vegetation is difficult here i document an erect in situ early pennsylvanian lycophyte swamp which provides the first confirmatory evidence for previously hypothetical ecological amplitudes

the surface albedo of the greenland ice sheet satellite derived and in situ measurements in the sondre stromfjord area during the 1991 melt season the temporal and spatial variation in the surface albedo of the greenland ice sheet during the ablation season of 1991 is investigated the study focuses on an area east of sondre stromfjord measuring 200 km by 200 km and centred at 67 5 n 48 13 w the analysis is based on satellite radiance measurements carried out by the advanced very high resolution radiometer avhrr the broad band albedo is estimated from the albedos in channel 1 visible and channel 2 near infrared the results are calibrated with the surface albedo of sea and dry snow satellite derived albedos are compared with gimex ground measurements at three stations there is a high degree of consistency in temporal variation at two of the three stations large systematic differences are attributed to albedo variations on subpixel scale in the course of the ablation season four zones appear each parallel to the ice edge it is proposed that these are in order of increasing altitude i clean and dry ice ii ice with surface water iii superimposed ice and iv snow an extensive description of these zones is given on the basis of the situation on 25 july 1991 zones i iii and iv reveal fairly constant albedos 0 46 0 65 and 0 75 on average whereas zone ii is characterised by an albedo minimum 0 34 survey of the western margin of the greenland ice sheet up to 71 n shows that the zonation occurs between 66 and 70 n

palynological correlation of major pennsylvanian middle and upper carboniferous chronostratigraphic boundaries in the illinois and other coal basins

cyclic changes in pennsylvanian paleoclimate and effects on floristic dynamics in tropical pangaea abstract wetland floras narrowly define perceptions of pennsylvanian tropical ecosystems the so called coal age such wetlands reflect humid to perhumid climate leading to characterizations of pennsylvanian tropics as everwet swampy these views are biased by the high preservation potential of wetlands sedimentation patterns paleosols and fossil floras indicate the presence of vegetation tolerant of subhumid to dry subhumid perhaps semi arid climate in basins between peat formation times understanding the significance of this seasonally dry vegetation has suffered from conceptual and terminological confusion a clearer view has emerged as models for framing the data have improved basinal floras typical of seasonally dry conditions relatively low soil moisture regimes are well documented but mainly from isolated deposits some of the earliest dominated by primitive pteridosperms flozfern floras occur in clastic rocks between european early pennsylvanian coal beds later early pennsylvanian fern cordaitalean vegetation different from coal floras is preserved in marine goniatite bullions conifers are first suggested by late mississippian potoniesporites pollen about the same time in north america broadleaf foliage lesleya and megalopteris occur in basin margin settings on drought prone limestone substrates the best known xeromorphic floras found between coal beds appear in the middle through late pennsylvanian containing conifers cordaitaleans and pteridosperms the middle pennsylvanian appearances of this flora are mainly allochthonous though parautochthonous occurrences have been reported parautochthonous assemblages are mostly late pennsylvanian the conifer flora became dominant in western and central pangaean equatorial lowlands in earliest permian location of the humid perhumid wetland flora during periods of relative dryness though rarely discussed is as or more perplexing than the spatial location of seasonally dry floras through time wetland plants had few migratory options and possibly survived in small refugia within and outside of basins coupled oscillations in climate sea level and vegetation were driven most likely by glacial interglacial fluctuations perhaps controlled by orbital cyclicity

stratigraphic and interregional changes in pennsylvanian coal swamp vegetation environmental inferences abstract quantitative analysis of pennsylvanian coal swamp vegetation provides a means of inferring organization and structure of communities distribution of these communities further provides inferences about environmental factors including paleoclimate our observations are based on in situ structurally preserved peat deposits in coal ball concretions from 32 coal seams in the eastern one half of the united states and from several seams in western europe and on spore assemblages from more than 150 seams there were three times of particularly significant and nearly synchronous vegetational changes in the midcontinent and appalachian coal regions during the pennsylvanian period each was different in kind and magnitude the first marked changes occurred during the early part of the middle pennsylvanian with the fluctuating decline in the high level of lycopod dominance the abundance of cordaites increased there was a rise in the occurrences of the lycopod herbs to form intercalated marshlands and an overall increase in floral diversity changes ensuing from this time also include shifts in dominant species of lycopod trees and a sustained rise in abundance and diversity of tree fern spores the next significant time of change was during the middle part of the middle pennsylvanian representing both a culmination of earlier trends and expansions of cordaites in the midcontinent where there was a maximum change in species without net loss of diversity tree ferns and medullosan pteridosperms attained subdominant levels of abundance and diverse lycopod species dominated except in the atokan desmoinesian transition of the midcontinent the third and sharpest break occurred near the middle late pennsylvanian boundary when extinctionsof the dominant coal swamp lycopods allowed development of tree fern dominance the late pennsylvanian coal swamps apparently were colonized or recolonized mainly by species from outside coal swamps rather than by the survivor populations of the middle pennsylvanian swamps paralleling the changes in floras through the pennsylvanian are changes in preservational aspects of the peat these include a decline in shoot root ratios from approximately 1 to

amplified melt and flow of the greenland ice sheet driven by late summer cyclonic rainfall intense rainfall events significantly affect alpine and alaskan glaciers through enhanced melting ice flow acceleration and subglacial sediment erosion yet their impact on the greenland ice sheet has not been assessed here we present measurements of ice velocity subglacial water pressure and meteorological variables from the western margin of the greenland ice sheet during a week of warm wet cyclonic weather in late august and early september 2011 we find that extreme surface runoff from melt and rainfall led to a widespread acceleration in ice flow that extended 140 km into the ice sheet interior we suggest that the late season timing was critical in promoting rapid runoff across an extensive bare ice surface that overwhelmed a subglacial hydrological system in transition to a less efficient winter mode reanalysis data reveal that similar cyclonic weather conditions prevailed across southern and western greenland during this time and we observe a corresponding ice flow response at all land and marine terminating glaciers in these regions for which data are available given that the advection of warm moist air masses and rainfall over greenland is expected to become more frequent in the coming decades our findings portend a previously unforeseen vulnerability of the greenland ice sheet to climate change

plant taphonomy in incised valleys implications for interpreting paleoclimate from fossil plants paleoclimatic interpretations of the upper triassic chinle formation colorado plateau based on plants conflict with those based on the sedimentary rocks the plants are suggestive of a humid equable climate whereas the rocks are more consistent with deposition under highly seasonal precipitation and ground water conditions fossil plant assemblages are limited to the lower members of the chinle formation which were deposited within incised valleys that were cut into underlying lower to middle triassic and older rocks in contrast the upper members of the formation which were deposited across the fluvial plain after the incised valleys were filled have few preserved fossil plants the taphonomic characteristics of the plant fossil assemblages within the stratigraphic and hydrologic context of the incised valley fill sequence explain the vertical and lateral distribution of these assemblages the depositional hydrological and near surface geochemical conditions were more conducive to preservation of the plants fossil plant assemblages in fully terrestrial incised valley fills should be taphonomically biased toward riparian wetland environments if those assemblages are used to interpret paleoclimate the paleoclimatic interpretations will also be biased the bias may be particularly strong in climates such as those during deposition of the chinle formation when the riparian wetlands may reflect local hydrologic conditions rather than regional climate and should be taken into account when using these types of plant assemblages in paleoclimatic interpretations

a conifer dominated palynological assemblage from pennsylvanian late moscovian alluvial drylands in atlantic canada implications for the vegetation of tropical lowlands during glacial phases abstract new research suggests that pennsylvanian coal forests were commonly replaced by conifer dominated vegetation during seasonally dry glacial phases here we describe palynological assemblages from stacked sequences of the middle pennsylvanian late moscovian sydney mines formation of nova scotia canada which lends some support to this hypothesis one critical sample from a widespread redbed succession below the harbour coal is dominated by conifer pollen 55 together with abundant representatives of cordaitaleans other coniferopsids and rare pteridosperms ferns and lepidodendrids it differs markedly from 13 other samples obtained from coals their roof shale limestone and associated channel bodies which are dominated by lepidodendrids marattialean tree ferns cordaitaleans and or calamiteans the latter beds represent coastal wetlands and are attributed to late transgressive and highstand systems tracts whereas the conifer bearing sample represents a dryland alluvial plain and may be attributed to lowstand or earliest transgressive systems tracts three additional samples from grey shale below a sequence boundary late highstand and between a redbed succession and major coal seam early to mid transgressive deposits contain transitional palynofloras with a high proportion of herbaceous gleicheniaceous and sphenopteroid ferns herbaceous lycopsids and sphenophylls interspersed with cordaitaleans and or lepidodendrids the dominance of conifer pollen within the dryland components of well defined sequences which have been linked to relative sea level change promoted by gondwanan glaciation supports the view that pennsylvanian tropical biomes responded to the beat of glacial interglacial cycles

the divergent environmental characteristics of permanently open seasonally open and normally closed estuaries of south western australia this study has compared the environmental characteristics of the basins and saline lower reaches of the tributaries of eight estuaries on the south coast of western australia which differ in their degree of connectivity with the ocean although four estuaries between 115 1 and 121 8 e along that coast remain permanently open to the ocean the others only become open when the volume of river discharge is sufficient to breach the prominent sand bars at their mouths which occurs annually following heavy winter and early spring rainfall in some estuaries seasonally open and infrequently in others normally closed estuaries to the west of 118 5 e are predominantly permanently open e g oyster harbour or seasonally open e g broke irwin and wilson inlets whereas those further east e g wellstead estuary and hamersley culham and stokes inlets where annual rainfall and thus discharge are much lower only become open after exceptionally heavy discharge in permanently and seasonally open estuaries pronounced haloclines and oxyclines are present in the narrow rivers but not the wide basins where the waters are subjected to wind driven mixing the extent of cyclical seasonal fluctuations in environmental conditions differed markedly among the three seasonally open estuaries and between years in one of those systems these differences reflected variations in the relationship between the volume of fluvial discharge which is determined by a combination of the amount of local rainfall catchment size and extent of clearing of native vegetation and the amount of intrusion by marine waters which is largely controlled by the size and duration of the opening of the estuary mouth the mean seasonal salinities in the basins of the three normally closed estuaries increased over three years of very low rainfall to 64 in the deepest of these estuaries stokes inlet to 145 in hamersley inlet and to 296 in the shallowest estuary culham inlet these results demonstrate that the environmental characteristics of estuaries on the south coast of western australia differ markedly even among those of the same type e g seasonally open estuaries or normally closed estuaries

remote sounding of greenland supraglacial melt lakes implications for subglacial hydraulics a supraglacial lake depth retrieval function is developed based on the correspondence between moderate resolution imaging spectroradiometer modis reflectance and water depth measured during raft surveys individual lake depth area and volume statistics including short term temporal changes for greenland s southwestern ablation region were compiled for 2000 05 the maximum area of an individual lake was found to be 8 9 km 2 the maximum volume 53 0 10 6 m 3 and the maximum depth 12 2 m sampling over 0 0625 km 2 pixel areas the total lake volume reaches 1 km 3 in this region by july each year the importance of melt lake reservoirs to greenland ice sheet flow may be a feedback between abrupt lake drainage events and ice dynamics lake outburst volumes up to 31 5 10 6 m 3 d 1 are capable of providing sufficient water via moulins to hydraulically pressurize the subglacial environment since the overburden pressure at the base of a flooded moulin is greater than that provided by ice lake outburst events seem capable of exerting sufficient upward force to lift the ice sheet locally if water flow in the subglacial environment is constrained laterally considering a moulin with a 10 m 2 cross sectional area basal pressurization can be maintained over lake outburst

paleoclimate controls on stratigraphic repetition of chemical and siliciclastic rocks climate is a primary control on sediment flux from continental sources into sedimentary systems in warm climates siliciclastic input is greatest under highly seasonal rainfall nonseasonal conditions favor formation of end member chemical rocks perennially wet climates are conducive to coal formation whereas dry climates produce carbonates and or evaporites stratigraphic repetition of siliciclastic and chemical rocks therefore appears to be related to paleoclimate cycles as well as to transgressive regressive events and tectonics