new petrological and geochemical data on mid paleozoic island arc volcanics of northern sierra nevada california evidence for a continent based island arc the mid paleozoic volcanics of northern sierra nevada consist of the sierra buttes rhyolites the taylor basalts and andesites and the keddie ridge basalt latite rhyolite suite the sierra buttes calc alkaline rhyolites display strong light rare earth element enrichment and negative end values the taylor basalts and andesites in the northern hough and genesee blocks exhibit calc alkaline affinities ree rare earth element patterns highly enriched in lree whereas in the southern hough block they are tholeiitic flat rare earth element patterns the abundance of silicic lavas the low end values of both the sierra buttes and taylor volcanics and the 18o values of the sierra buttes rhyolite and bowman lake trondjhemite provide evidence that the northern sierra nevada island arc was continent based the keddie ridge differentiated volcanics characterized by high zr y nb k and light rare earth elements are geochemically similar to a shoshonite suite their eruption at the end of the mid paleozoic v

moisture source in the hyblean mountains region south eastern sicily italy evidence from stable isotopes signature abstract here the authors present results of an isotope study on precipitation collected during a 2 a period from a rain gauge network consisting of 6 stations located at different elevations in the hyblean mountains hm region in south eastern sicily the slope of the local meteoric water line d 6 50 18 o 9 87 obtained for the region suggests that precipitation is affected by evaporation during rainfall events the main variations in rainwater isotope composition are due to seasonal effects and elevation an average 2 h excess value of 21 2 was found for precipitation events less affected by evaporation i e when the rainfall was 65 mm month the spatial distribution of o isotope composition of precipitation shows a negative gradient from east and south to the inner areas the depositional rate of cl used as a tracer of the origin of air masses is highest at the coastal rain gauges sr and mrg stations and lowest on the northern flank of the hm region sc station based on these findings a model is proposed for the origin of precipitation in the hm region which assumes that a mediterranean derived component is the main source of moisture in the studied area d h and 18 o 16 o ratios of inferred meteoric recharge waters were also compared with the isotope composition of waters collected from the main local springs and wells the best linear fit of the 18 o vs d relationship for hyblean groundwater is d 4 85 18 o 2 01 the enrichment of heavy isotopes in hyblean groundwater is probably due to evaporation occurring after precipitation events or to a recharging contribution from surface waters lakes or rivers enriched in heavy isotopes

petrography and microanalysis of pennsylvanian coal ball concretions herrin coal illinois basin usa bearing on fossil plant preservation and coal ball origins abstract petrographic analyses of 25 coal balls from well studied paleobotanical profiles in the middle pennsylvanian herrin coal westphalian d illinois basin and five select coal balls from university collections indicate that herrin coal ball peats were permineralized by fibrous and non fibrous carbonates fibrous carbonates occur in fan like to spherulitic arrays in many intracellular within tissue pores and are best developed in relatively open extracellular between plant pore spaces acid etched fibrous carbonates appear white under reflected light and possess a microcrystalline texture attributable to abundant microdolomite scanning electron microscopy x ray diffraction and electron microprobe analysis demonstrate that individual fibers have a distinct trigonal prism morphology and are notable for their magnesium content 9 15 mol mgco 3 non fibrous carbonates fill intercrystalline spaces among fibers and pores within the peat as primary precipitates and neomorphic replacements in the immediate vicinity of plant cell walls non fibrous carbonates cut across fibrous carbonates as a secondary neomorphic phase attributed to coalification of plant cell walls dolomite occurs as diagenetic microdolomite associated with the fibrous carbonate phase as sparite replacements and as void filling cement maximum dolomite 50 59 wt is in the top of seam coal ball zone at the sahara mine which is overlain by the marine anna shale coal ball formation in the herrin coal began with the precipitation of fibrous high magnesium calcite the trigonal prism morphology of the carbonate fibers suggests rapid precipitation from super saturated meteoric pore waters carbonate precipitation from marine waters is discounted on the basis of stratigraphic paleobotanical and stable isotopic evidence most non fibrous carbonate is attributable to later diagenetic events including void fill replacements recrystallization and post depositional fracture fills evidence suggests that co 2 degassing was important in coal ball formation in the herrin coal which mainly occurred sequentially upward with peat accumulation in the sites studied

relationships among macerals minerals miospores and paleoecology in a column of redstone coal upper pennsylvanian from north central west virginia u s a abstract two distinct paleoenvironments are represented in vertical succession in a column of redstone coal in north central west virginia as indicated by a study of 37 consecutive 3 cm 0 1 ft increments analyzed for ash yield petrographic composition low temperature ash mineralogy and palynomorph abundances abundance profiles were constructed for ash 12 petrographic components 3 minerals and 5 miospore assemblages the profiles and calculated correlation coefficients show close relationships between several constituents components that increased in abundance upward in the coal bed were a collinite type 50 microns in thickness cutinite and miospores affiliated with calamites herbaceous lycopods cordaites and herbaceous ferns components that decreased in abundance upward were a collinite type 50 m in thickness cutinite calamite and cordaite miospores and kaolinite significant correlations occurred between ash yield and the collinite types 50 and

ecological changes in pennsylvanian asturian and early cantabrian coal floras inferred from lycophyte microspore abundances abstract the distribution and relative amounts of six genera of lycophyte microspores lycospora densosporites crassispora cirratriradites endosporites and cadiospora are compared in the pennsylvanian coals from the dobrudzha and forest of dean coalfields clastic sediments from the glace bay borehole in the cape breton coalfield and the southern crop of the south wales coalfield inverse relationships are shown between lycospora and densosporites and between lycospora and crassispora in samples from all of the coalfields the changes in microspore assemblages suggest there were at least five different communities of lycophyte plants growing in the pennsylvanian swamps changes in microspore assemblages at the asturian cantabrian boundary mirror the previously described macrofloral changes at this time

mesozoic evolution of exotic terranes and marginal seas western north america abstract regional terrane analysis has been combined with a global evaluation of plate kinematics to produce a new tectonic model for the mesozoic evolution of western north america and its associated marginal seas the model employs a two tiered data reliability ranking system to resolve conflicts within data sets the lower tier of the ranking system involves the assignment of a numerical rank to paleomagnetic and or paleobiogeographic data based on each data set s reliability the upper tier of the ranking system places the paleomagnetic and paleobiogeographic data in perspective by assigning a relative order of importance to different types of data the most reliable data are considered to be departure rift and arrival collision times that are tightly constrained by independent data sets evidence of subduction and or strike slip motion also ranks high in the master ranking system paleomagnetic and vertebrate paleobiogeographic data come next in the hierarchy followed by invertebrate and floral paleobiogeographic data application of this approach to a case study the baja british columbia controversy has resulted in a coherent model for the entire region results derived from the application of this modelling approach to the problem of the mesozoic assembly of western north america suggest that its evolution may be modeled using a minimum of 57 large terranes oblique convergence may have been the dominant tectonic process along the western north american margin during the mesozoic causing large scale latitudinal transport of many exotic terranes the motions of the terranes produced a number of marginal seas yukonia etc that were short lived but important components of western margin tectonics a combination of collision events side swiping episodes and changes in plate kinematics led to the initiation of several regional tectonic upheavals including the nevadan and sevier orogenies

isotopic features of precipitation and groundwater from the eastern alps of italy results from the mt tinisa hydrogeological system this study analyses water stable isotopes data collected from precipitation one rain gauge and groundwater outlets seven occurrences and two springs at mt tinisa in the eastern alps of italy limestones and dolostones outcrop in the mountain relief making up a single aquifer which feeds the monitored outlets with almost steady discharges lack of runoff in the streambeds throughout the whole year means that all meteoric water can be considered as recharging the aquifer sampling was undertaken during the periods 2005 2010 precipitation and 2014 2015 groundwater via monthly and two three monthly field activities respectively which allowed a total of 138 water samples to be gathered and analysed results highlighted the presence of apparent isotopic anomalies in groundwater in comparison with meteoric water the study demonstrates that the assessment of groundwater residence time and estimates of the mean monthly isotopic content in rainwater have been necessary to correctly compare the two isotopic datasets and relate the anomaly to the recharge time window occurring in the late autumn

the upper pennsylvanian duquesne coal of ohio usa evidence for a dynamic peat accumulating swamp community abstract an outcrop of the duquesne coal conemaugh cyclothem has the only significant occurrence of coal balls in upper pennsylvanian stephanian b equivalent sediments of the appalachian basin excellent preservation of plant debris within autochthonous peat has permitted a more refined reconstruction of the source plant community than reported in published studies of other coals coal balls were quantitatively sampled for whole plant species and mineralogical content shoot root ratios were extremely high compared with values reported for other coals the samples were analyzed using cluster analyses and non metric multidimensional scaling mds in order to differentiate microhabitats and stages of ecological succession within the general flora cluster analysis produced 5 stable clusters which agreed with the sequence of ecological succession as determined in a previous study and with microhabitat differentiation in contemporaneous seral stages three dimensions of the mds analysis provided the best fit to the data the dimensions are interpreted as representing 1 ecological time or succession 2 increasing dominance of psaronius tree ferns in the plant community and 3 an increase in microtopological variation probably hummock formation the initial stages of succession oldest layers of permineralized peat are characterized by aerial debris from mesoxylon sigillaria and calamites followed by an assemblage dominated by chaloneria this was succeeded by more species diverse assemblage dominated by neuropteris seed ferns and psaronius tree ferns with numerous subcanopy plants including lianas epiphytes and ground herbs late seral stages youngest layers of permineralized peat were dominated by psaronius tree ferns

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

chemical and isotopic indicators of point source recharge to a karst aquifer south australia abstract several hundred sinkholes swamps and open drainage boreholes throughout the semi arid to sub humid areas of the southeast of south australia are potential recharge sites to the upper part of the gambier limestone aquifer this paper presents the results from a hydrochemical cl and carbonate chemistry and isotopic 2 h s 18 o and 36 cl study used to estimate the importance of localised recharge from these point source features to the karstic groundwater system results show that water recharging the groundwater via point source features is detectable only on a local scale chemical and isotopic compositions of groundwaters more than 150 m from the larger of the point source features are indistinguishable from regional groundwater compositions chloride concentrations carbonate chemistry and isotope data show that annual input of water via point sources contributes less than 10 of total recharge with diffuse recharge providing the remainder to the study area as a whole point source recharge is generally intermittent and was observed to occur only for a few days at a time and only after a threshold of sustained rainfall had been exceeded i e greater than 2 5 mm day 1 for more than 3 days the stable isotopic composition of waters recharging via sinkholes tends to be enriched in 2 h and 18 o relative to regional groundwater and local precipitation this is probably caused by a small degree of evaporation less than 596 of water falling within the catchment occurring during winter at high relative humidity greater than 9596 before recharge 36 cl from weapons testing is detectable in groundwaters near sinkholes and indicates significant retardation of cl within soils of the respective sub drainage systems recharge has therefore occurred within the past 30 years but cannot be quantified with any reliable precision from the 36 cl data

comparison between two palaeozoic island arc terranes in northern california eastern klamath and northern sierra nevada geodynamic constraints abstract the palaeozoic geodynamic environment of northern california is considered to be one of offshore island arcs bounded by marginal seas the petrological and geochemical features of the eastern klamath and northern sierra nevada island arc sequences are important indicators of the geodynamic evolution of the cordillera the eastern klamath pre early devonian island arc sequence consists of pillowed basalts andesites and boninites overlain by low k rhyolites both suites erupted in a submarine environment these volcanics characterized by almost flat ree patterns and high nd represent a primitive intraoceanic island arc the mid palaeozoic volcanic succession of northern sierra nevada is formed of calc alkaline rhyolites conformably overlain by either calc alkaline in the north or low k tholeiite in the south basalts and andesites the volcanic episode ended in the early carboniferous with a differentiated shoshonitic suite all the massive or pillowed flows are interbedded with volcaniclastic sediments suggesting that they were erupted partly in a shallow water environment the geochemical features of the volcanics moderate to high lree enrichment and low nd values are evidence for the involvement of a crustal component in the magma genesis the mid palaeozoic volcanic sequence therefore represents a continent based island arc this microcontinent could be the sonomia microplate excluding the eastern klamath plate thus these two northern californian palaeozoic sequences cannot be considered as lateral counterparts but could represent the remnants of oceanic and continental island arcs as observed in the present day east pacific areas along the eurasiatic margin

mapping eastern north american vegetation change of the past 18 ka no analogs and the future the method of modern analogs and an extensive data base of modern and fossil pollen data were used to generate a new series of paleovegetation maps for eastern north america spanning the past 18 ka the maps illustrate the continuous nature of climate induced vegetation change and the development after about 10 ka of modern regional vegetation patterns before the holocene vegetation biomes without modern analogs were widespread in response to climate conditions without modern analogs and to a lesser extent to the rapidity of climate change over the last glacial interglacial transition this geological perspective suggests that possible future climate changes could force similarly complex changes in natural vegetation including the development of biomes without modern analogs

geodynamic implications of devonian silicic arc magmatism in the sierra nevada and klamath mountains california most proposed geodynamic models integrate the northern sierra nevada and eastern klamath mountains in a single island arc system new petrological and geochemical data show that the upper devonian sierra buttes formation of the northern sierra nevada displays important differences from the lower devonian balaklala formation of the eastern klamath mountains the cale alkalic affinity of the sierra buttes rhyolites light rare earth element ree enriched low e nd suggests that they were erupted in a continent based island arc in contrast the lower devonian balaklala low k tholeiitic rhyolites light ree depleted high e nd are considered to be part of an intraoceanic island arc sequence moreover the paleozoic tectogenesis of these two island arc sequences is different the lower devonian balaklala rhyolites were affected by the late devonian early carboniferous orogeny whereas the sierra buttes formation is on basement already affected by a pre late devonian deformation therefore at least after carboniferous time and before late triassic time the eastern klamath and northeastern sierra nevada island arcs cannot be considered lateral counterparts

oxygen isotope composition of natural waters in the mt etna area oxygen isotopes of both rainwater and groundwater samples from mt etna were used to obtain information on recharge areas flow paths and the origin of wet air masses oxygen isotope composition was determined in rainwater samples collected for a period of 3 years october 1997 october 2000 in 11 rain gauges distributed along the flanks of mt etna from sea level to 2900 m of altitude values ranged from 213 8 to 1 9 the lowest values being measured at higher altitudes and or during cooler periods for rain gauges located from sea level up to 1000 m altitude volume weighted values defined an isotopic gradient of 22 7 km which is in the range observed in the mediterranean area higher altitude gauges yielded a much lower gradient 2 0 6 km probably due to the fact that vapour condensing at higher altitudes was mixed with an 18 o rich volcanic component deriving from the huge vapour output of the summit craters the oxygen isotope composition of about 210 groundwater samples collected all around the volcano ranged from 2 9 3 to 2 5 0 the higher values measured on the eastern flank indicated that recharge occurs at lower altitudes on this flank the low variability 0 30 0 65 of the monthly values gathered from 14 groundwater sampling points over a period of 2 years indicates that the groundwater system is isotopically well mixed some long term trends may be explained by variations in annual recharge due to the prevalent isotope composition of wet air masses q 2004 elsevier b v 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

the groundwater resources and sustainable yield of cheju volcanic island korea hydrogeologic data of 455 water wells comprising geologic logs water qualities and aquifer test results are analyzed to determine hydrogeological characteristics water quality and sustainable yield of the groundwater resources of cheju volcanic island the groundwater of the island occurs in unconsolidated pyroclastic deposits and clinkers interbedded in highly jointed basaltic and andesitic rocks as high level basal and parabasal groundwater under unconfined conditions the total storage of groundwater is estimated at about 44 billion m3 the average transmissivity and specific yield of the aquifer are at about 0 34 m2 s 1 29300 m2 day 1 and 0 12 respectively the average annual precipitation is about 3 39 billion m3 of which 1 49 billion m3 equivalent to 44 0 of the total annual precipitation is recharged into aquifers with 0 638 billion m3 year 1 of runoff and 1 26 billion m3 year 1 of evapotranspiration based on a groundwater budget analysis the sustainable yield is estimated at about 0 62 billion m3 year 1 equivalent to 41 6 of annual recharge a low permeability marine sedimentary formation sehwari formation composed of loosely cemented sandy silt was recently found to be situated at 120 68 m below mean sea level if the said marine sediment is distributed as a basal formation of the freshwater zone of the island most of its groundwater will be of parabasal type so the marine sediment is one of the most important hydrogeological boundaries and groundwater occurrences in the area

the plant fossil record reflects just two great extinction events five great taxonomic extinctions the so called big five mass extinctions are widely recognized in life history at the end of the ordovician frasnian late devonian permian triassic and cretaceous all of them were originally identified in the marine fossil record and have been interpreted as the result of abrupt global environmental changes previous evidence has suggested that terrestrial biota were also subjected to ecological disruption during these events but it is unknown whether they suffered the same level of large scale taxonomic disruption as marine organisms here we show that the plant fossil record in fact only provides evidence of two mass taxonomic extinction events one through the carboniferous permian transition the other during middle late permian times this differs significantly from the mass extinctions recognized in the marine realm and suggests that vascular plants have a special capacity for surviving abrupt environmental changes

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

persistence of late carboniferous tropical vegetation during glacially driven climatic and sea level fluctuations abstract the late carboniferous glaciation reached its peak during the latter part of the westphalian late desmoinesian in the tropical illinois basin this was the time of deposition of the carbondale and lower modesto formations characterized by the cyclic repetition of major coal deposits black shales limestones gray shales and sandstones these lithological changes evidence repeated major fluctuations in climate and sealevel fossil floras from the tropical ever wet to seasonally wet terrestrial lithofacies coals and shales above coals remain compositionally similar throughout the 1 1 5 m y time interval floras from coals known from coal balls and palynology characteristically were composed of three major plant communities the wettest sites were dominated by monocarpic lycopsids intermediate sites were dominated by polycarpic lycopsids and areas subject to fires and intermittent flooding were dominated by medullosans and the small lycopsid paralycopodites clastic substrate environments were dominated by ferns and pteridosperms and conform to a single biozone indicating their compositional unity and distinctness from earlier and later assemblages the composition of lowland floras is poorly known from times between the deposition of coals and associated terrestrial rocks intervals during which most of the lowlands were flooded and marine rocks were being deposited consequently the temporally intermittent recurrence of lowland floras despite repeated widespread environmental disruption may be explained either by vegetational persistence and migration of floras or repeated disruption and reassembly several lines of evidence suggest persistence as a likely explanation

δ18o and δd systematics in the surficial waters of the gaula river catchment area kumaun himalaya india abstract the 18 o and d measurements of surface waters streams springs lakes and precipitation from the gaula river catchment area of kumaun himalaya are reported the d and 18 o values are positively correlated as has been the case with waters from several other regions the lake waters are found to be enriched in 18 o and d compared with the neighbouring regions owing to evaporation estimates of mean total evaporation during the dry season range from 10 to 25 spring water samples collected from various altitudes from 915 m to 2150 m display variations in values showing an altitude effect of 0 1491 per 100m elevation

using h and o isotopic data for estimating the relative contributions of rainy and dry season precipitation to groundwater example from cheju island korea abstract a comparison of deuterium excess or d values of precipitation and groundwater at cheju island korea indicates that unlike in many temperate climates precipitation during the whole year contributes to groundwater recharge this in turn suggests that evapotranspiration effects are minimal consistent with the fact that the island contains highly permeable volcanic rocks overlain by thin soils this hypothesis is contrary to current water budget models that ascribe a significant role to evapotranspiration processes three coastal springs and several streams and ponds throughout the island have enriched 18 o and d values that plot off the local meteoric water line and have relatively high cl concentrations this relationship is suggestive of seawater mixing for the coastal springs and evaporation for the streams and ponds this database thus provides a useful means for evaluation of groundwater resources of the island

isotope hydrology study of areas in eastern macedonia and thrace northern greece abstract sampling of springs for which the mean elevation of recharge could be estimated provided an estimate of 0 44 100 m 1 for the groundwater altitude effect on the 18o value in eastern macedonia and 0 21 in thrace a slight difference in both the slope and the intercept of the lines expressing the regression of elevation against 18o values in the continental part of thrace and the island of thassos is also observed as case studies the isotopic composition of surface water and groundwater was used to investigate the mechanism of recharge of groundwater in the areas of lekani mountains and thassos island as a result the contribution of water leaking from the river nestos to the recharge of the springs of paradissos near to the river bed kastro filippon and aghios athanassios at a distance of over 25 km from the river bed as well as of the aquifers tapped by boreholes in the plain between kastro filippon and aghios athanassios was indicated the estimate is 54 12 for the contribution of the river water to the spring yield in the case of aghios athanassios and 43 10 in the case of the springs of paradissos as another result the hydraulic connection between the marbles of profitis ilias and the marbles and dolomites of potamia series in the case of thassos island was confirmed finally the extent of the carbonate rocks and the amount of precipitation effective in recharge to the main springs as well as to the aquifers tapped by boreholes in the different plains of the areas under investigation were estimated

uplands lowlands and climate taphonomic megabiases and the apparent rise of a xeromorphic drought tolerant flora during the pennsylvanian permian transition abstract the late mississippian and pennsylvanian have been referred to as the coal age due to enormous paleotropical peat accumulations coal beds numerous fossil floras have been collected from these coals and their associated seat earth paleosols and roof shales over more than two centuries leading to the inference of vast swampy wetlands covering the pangean tropics during the pennsylvanian in contrast the permian tropics are characterized as more arid with sparser and more heterogeneous vegetation than inferred for the pennsylvanian in the tropics the pennsylvanian to permian transition has been described as a changeover from a pteridophyte dominated paleophytic flora to a seed plant dominated mesophytic flora this view notwithstanding floras dominated by xeromorphic seed plants also are well known from the pennsylvanian tropics some authors have characterized these plants as being occupants of uplands subsequently transported into basinal lowland preservational environments in this model uplands are well drained causing areas of drought under otherwise everwet climates in this paper we present an alternative interpretation that the apparent transition in pennsylvanian permian tropical vegetation reflects two types of taphonomic megabias first is a preservational megabias strongly favoring the vegetation of humid climates over that of seasonally dry climates accordingly tropical plant preservational potential fluctuated in concert with late paleozoic ice age glacial interglacial oscillations and contemporaneous sea level and climatic changes second is an analytical megabias strongly favoring the discovery and collection of the wetland biome from pennsylvanian strata overlooking the less frequently and more poorly preserved drought tolerant biome by permian times vast wetlands and their fossil record had largely disappeared from central pangea although continuing in cathaysia making drought tolerant vegetation more visible to searchers without changing its preservational circumstances we demonstrate that the upland model is untenable being inconsistent with the principles of plant biogeography and with geological aspects of the fossil record

intermonthly variability of cyclone tracks in the mediterranean abstract objective calculated monthly cyclonic tracks in the mediterranean are presented the intermonthly variations within each season are shown to be quite significant and an particularly notable for december january april may and june july we suggest that composite seasonal pictures are not faithful representations of the cyclonic routes over a complex terrain region like the mediterranean

are coal balls rare a cyclostratigraphic analysis of coal ball occurrence in north america abstract from the perspective of phanerozoic time coal balls are rare apparently limited to a 24 m y interval 323 299 ma in the pennsylvanian and earliest permian yet within this interval coal balls occur in many coals approximately 82 transgressive regressive sedimentary cycles have been described for the midcontinent illinois and appalachian basins of north america during the mid to late pennsylvanian one third 27 82 have coal balls including 57 of major cycles 36 of intermediate cycles and 16 of minor cycles coal ball occurrence in the donets basin is similar over an interval of about 4 m y 315 311 ma latest bashkirian to mid moscovian 39 11 28 of transgressive regressive cycles have coal balls as north american paleoclimate became drier tree ferns replaced lycopsids as the dominant plant in peat swamps at the desmoinesian missourian boundary and coal ball occurrence declined overall 47 of cycles 19 40 with lycopsid or cordaitean dominance have coal balls whereas 19 8 42 of cycles with tree fern dominance have coal balls p this pattern may reflect the relative abundance of coal in the late pennsylvanian with drier paleotropical climates in the missourian virgilian leading to less paleotropical coal fewer mines and a lower probability of discovering missourian and virgilian coal balls however average cycle duration decreased from 150 kyr in the desmoinesian to 100 kyr in the missourian and virgilian and faster rates of relative sea level rise could have affected coal ball abundance particularly if coal balls formed in marine swamps with more rapid transgression leading to thinner coals or to freshwater coals directly overlain by marine sediments rygel et al 2008 suggested that missourian virgilian cycles recorded more erosional relief than desmoinesian cycles consistent with increased amplitude and rates of sea level rise during each glacial eustatic cycle changes in missourian virgilian cycles may have been augmented by stratigraphic attenuation as sediment filled the antecedent topography

changes in dominance patterns in upper carboniferous plant fossil assemblages upper carboniferous pennsylvanian terrestrial clastic rocks from north america and europe contain compression impression plant fossil assemblages that represent the remains of plant communities that grew on floodplains levees and other clastic facies of fluvial and deltaic lowlands quantitative analysis of 66 plant fossil assemblages spanning the entire late carboniferous demonstrates that before the middle of the westphalian d stage the majority of plant fossil assemblages are dominated by pteridosperms and sphenopsids lycopods and cordaites dominate only a few assemblages counted ferns do not dominate any assemblages these findings contrast sharply with the dominance of lycopods reported by others from coal swamps of the same time interval above the middle of the westphalian d however one third of the compression impression assemblages counted are dominated by ferns the change in dominance pattern in compression impression plant fossil assemblages occurs half a stage earlier than the previously reported change from lycopod dominated to fern dominated assemblages at the westphalian stephanian boundary in coal swamps a trend toward dryer climate during westphalian d apparently influenced plants growing on better drained alluvial soils earlier than those growing on water logged soils of contemporaneous coal swamps

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

vegetational zonation in a swamp forest middle pennsylvanian illinois basin u s a indicates niche differentiation in a wetland plant community abstract a rich fossil flora occurs in the roof shale of the middle pennsylvanian moscovian age springfield coal flanking the galatia channel a river deposit approximately 1 km in width and 150 km long partially contemporaneous with the springfield peat swamp siltstone and sandstone 30 m thick were deposited in the channel during the final estuarine phase the river formed under seasonal subhumid climate during early deglaciation as marine waters retreated from the land surface it existed continuously through glacial maximum under increasingly humid climate as a low sediment or black water river with peat along its flanks during early deglaciation under subhumid climate and sea level rise the river became a sediment laden estuary drowning the peat swamp and burying vegetation in place under extensive mudflats this buried flora was studied in three underground mines in southern illinois permitting vegetation to be characterized spatially three transects comprising 100 sites a total linear distance of 12 km reveal distinct zonation perpendicular to the channel margin an innermost belt 0 5 to 2 5 km wide consists almost exclusively of the pteridosperm neuropteris flexuosa north of a river bend three belts succeed the n flexuosa zone mixed pteridosperms and marattialean tree ferns mixed arborescent lycopsids and marattialians lycopsids with rare marattialians south and inside the same bend n flexuosa is succeeded by mixed lycopsids particularly sigillaria and marattialean ferns within the transects marattialian ferns have wider distribution than other groups suggesting broader environmental tolerances neuropteris flexuosa channel margin mono dominance may reflect high sedimentation rates elevated nutrient conditions or floating seed dispersal lycopsid dominance in interior areas conforms with tolerance of deep standing water the spatial scale examined affects our perception of community assembly overall distinct vegetational zonation suggests niche assembly however within vegetational bands there is considerable small scale spatial variation suggesting stochastic properties

paleoecology of the late pennsylvanian age calhoun coal bed and implications for long term dynamics of wetland ecosystems quantitative plant assemblage data from coal balls miospores megaspores and compression floras from the calhoun coal bed missourian of the illinois basin usa are used to interpret spatial and temporal changes in plant communities in the paleo peat swamp coal ball and miospore floras from the calhoun coal bed are dominated strongly by tree ferns and pteridosperms and sigillarian lycopsids are subdominant depending on geographic location within the coal bed although the overall composition of calhoun peat swamp assemblages is consistent both temporally and spatially site to site differences and short term shifts in species dominance indicate local topographic and hydrologic control on species composition within the broader context of the swamp statistical comparison of the calhoun miospore assemblages with those from other late pennsylvanian coal beds suggests that the same basic species pool was represented in each peat swamp landscape and that the relative patterns of dominance and diversity were persistent from site to site therefore it appears that the relative patterns of proportional dominance stayed roughly the same from one coal bed to the next during late pennsylvanian glacially driven climatic oscillations

rainfall recharge relationships within a karstic terrain in the eastern mediterranean semi arid region israel δ 18o and δd characteristics annual rainfall variations and processes in the upper vadose zone exert a profound influence on the chemical and isotopic compositions of waters of carbonate aquifers in semi arid climatic zones in order to define these processes we have studied the surface temperatures during rainfall events the isotopic composition of rain infiltrating and groundwaters this study was carried out within a karstic terrain soreq cave israel located in cenomanian dolomitic rocks approximately 40 km inland of the mediterranean sea and 400 m above sea level the climate is typical of the eastern mediterranean semi arid conditions with a rainy winter and dry summer and the average annual rainfall in the area is 500 mm close monitoring indicates that the d and 18o values of individual rainstorm events decrease with increasing rainfall annual average isotopic values of years with rainfall of 500 600 mm do not vary systematically years with extreme rainfall values define a negative covariation between the 18o and rainfall the d 18o relationship of all rain events of more than 20 mm fall on the mediterranean meteoric water line mmwl with a slope of 8 and d excesses of 20 30 these rain events occur when mid winter surface temperatures are 5 to 10 c rainfall events of less than 20 mm mainly occurring at above 10 c have slopes of less than 8 and smaller d excess as a consequence of evaporation processes beneath the clouds two main water types infiltrating into the cave are recognized slow and fast drip slow drip occurs from the tips of stalactites and takes place throughout the year these waters represent seepage water that remains in the upper vadose zone for up to several decades fast drip emanates from fissures in the cave roof during the winter seasons these waters represent vadose flow with a short residence time of less than 1 year the infiltration of the fast drip water into the cave depends on the fracture system of the rock cover and on the intensity of the rainstorms in the inner parts of the cave where the rock cover is thick fast drip starts only after several massive 20 mm rainstorms whereas below a thin roof the response time of fast drip is a few hours to a few days after intensive rainstorms both fast and slow drip water fall on the mmwl indicating that they are derived mainly from the relatively intensive rainstorms that compose about 23 of the annual rainfall although fast dri water represents massive rainstorms their 18o and d values are nonetheless higher by 1 and 10 respectively relative to the average rainwater compisition this indicates that the fast drip water consists predominantly of water derived from intensive rainstorms admixed with a minor component of isotopically 18o and d enriched water which is represented by the slow drip waters the fast drip waters are derived mainly from massive rain events at surface temperatures of 5 to 10 c which thermally equilibrate with the host rock and upon reaching the cave they have already acquired the mean temperature 20 c of the cave

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

late pennsylvanian aridification on the southwestern margin of gondwana paganzo basin nw argentina a regional expression of a global climate perturbation abstract paleosols of the paganzo group preserve a shift from the cool climate of the glaciated high latitudes of gondwana to a long term aridification punctuated by shorter term fluctuations in moisture regime in the late carboniferous a quantitative reconstruction of paleoclimate inferred from the major element chemistry of paleosol horizons and the stable isotope geochemistry of soil formed minerals and organic matter indicates that the climate varied substantially during deglaciation along the southwestern margin of gondwana in the middle pennsylvanian including two geologically abrupt shifts to notably drier conditions this dynamic climate terminates in a dry subhumid moisture regime characterized by steppe dry scrub floral provinces quantitative estimates of net primary production during the post glacial interval inferred from paleosol major element geochemistry are consistent with a mesic soil temperature regime in agreement with paleotemperatures inferred from pedogenic goethite d and 18 o contemporaneous aridification is well expressed in paleotropical continental records with middle to late pennsylvanian aridification coincident with an abrupt evolutionary change in many marine and terrestrial species the synchrony of aridification between the high and low paleo latitudes and concomitant major restructuring of some ecosystems suggests that a paleoclimate change of global nature occurred during the moscovian and kasimovian

stable isotope ratios in meteoric recharge and groundwater at mt vulture volcano southern italy summary a rain gauge network consisting of five sites located at different altitudes ranging from 320 to 1285 m a s l was installed at mt vulture volcano southern italy rain water samples were collected monthly over a two year period and their isotopic composition 18o and d was analyzed during the same period circulating groundwater was sampled from 24 springs and wells distributed throughout the study area monthly isotopic composition values were used to determine the local meteoric water line lmwl its slope is slightly lower than the relationship defined by longinelli and selmo longinelli a selmo e 2003 isotopic composition of precipitation in italy a first overall map j hydrol 270 75 88 for southern italy the groundwater samples analyzed were distributed essentially along the lmwl the weighted local meteoric water line wlmwl defined through the mean values weighted by the rainfall amount however may define in a short range the meteoric end member in the local hydrological cycle more precisely since most of the groundwater sampling locations do not show seasonal variations in their stable isotope values the flow system appears to be relatively homogeneous the mean altitude of the recharge by rainfall infiltration was estimated on the basis of the local vertical isotopic gradient 18o a few springs which show anomalous isotopic values reveal more regional circulation systems associated with tectonic structures responsible for the ascent of deeper water

place vs time and vegetational persistence a comparison of four tropical mires from the illinois basin during the height of the pennsylvanian ice age abstract coal balls were collected from four coal beds in the southeastern part of the illinois basin collections were made from the springfield herrin and baker coals in western kentucky and from the danville coal in southwestern indiana these four coal beds are among the principal mineable coals of the illinois basin and belong to the carbondale and shelburn formations of late middle pennsylvanian age vegetational composition was analyzed quantitatively coal ball samples from the springfield herrin and baker are dominated by the lycopsid tree lepidophloios with lesser numbers of psaronius tree ferns medullosan pteridosperms and the lycopsid trees synchysidendron and diaphorodendron this vegetation is similar to that found in the springfield and herrin coals elsewhere in the illinois basin as reported in previous studies the danville coal sample which is considerably smaller than the others is dominated by psaronius with the lycopsids sigillaria and synchysidendron as subdominants coal balls from the springfield coal were collected in zones directly from the coal bed and their zone by zone composition indicates three to four distinct plant assemblages the other coals were analyzed as whole seam random samples averaging the landscape composition of the parent mire environments this analysis indicates that these coals separated from each other by marine and terrestrial clastic deposits have essentially the same floristic composition and thus appear to represent a common species pool that persisted throughout the late middle pennsylvanian despite changes in baselevel and climate attendant the glacial interglacial cyclicity of the pennsylvanian ice age patterns of species abundance and diversity are much the same for the springfield herrin and baker although each coal both in the local area sampled and regionally has its own paleobotanical peculiarities despite minor differences these coals indicate a high degree of recurrence of assemblage and landscape organization the danville departs dramatically from the dominance diversity composition of the older coals presaging patterns of tree fern and sigillaria dominance of late pennsylvanian coals of the eastern united states but nonetheless built on a species pool shared with the older coals

vegetation heterogeneity on a late pennsylvanian braided river plain draining the variscan mountains la magdalena coalfield northwestern spain article the spatial heterogeneity and community ecology is reconstructed for late pennsylvanian stephanian b sensu lato vegetation preserved in la magdalena coalfield northwestern spain the 1500 m thick basin fill accumulated rapidly along the margin of the variscan mountains and the principal sedimentary facies comprise the deposits of large braided streams that dissected extensive wetlands containing large lakes quadrat analysis of 93 mostly par autochthonous megafloral assemblages indicates that pteridosperms and ferns dominated communities with three taxa pecopteris spp callipteridium pteridium and neuropteris ovata accounting for 58 of all plant remains sphenopsids and lycopsids were less common but widespread and cordaitaleans were rare at the local scale laterally exposed bedding planes reveal that communities comprised a complex and heterogeneous mosaic of species at the landscape scale ecological gradients are evident from multivariate analyses of quadrats in a facies context pteridosperms dominated marginal wetlands adjacent to steep basin margins a greater proportion of ferns occurred in or adjacent to

common ground between two british pennsylvanian wetland floras using large first hand datasets to assess utility of historical museum collections abstract studies on the macrofloral record of the pennsylvanian palaeotropical peat forming wetlands coal swamps depend heavily on historical collections in museums this paper examines the robustness of such collections for macrofloral studies 110 000 individually recorded specimens from south wales field collected by david davies during the early 20th century were compared with the 6500 museum voucher specimens derived from them eventually intended for a representative teaching collection this showed that the voucher collections accurately reflect the order of abundances of the plant groups as documented in the field records but not their actual numerical abundances these welsh data were then compared with the available museum collections for similar aged macrofloras in the nearby bristol somerset coalfield cluster analyses and detrended correspondence analyses were performed 1 on the raw data recorded on the museum labels 2 on standardised data that were updated to reflect the currently accepted taxonomy for these fossils and 3 on standardised data in which single occurrences of taxa have been removed the results suggest that unstandardised museum collection data can reveal meaningful biostratigraphical and biogeographical patterns but that these become clearer with the standardised data the effect of removing the singleton taxa was less clear although it did provide a slightly enhanced resolution with cluster analysis whilst previous studies have considered these to be separate basins with the bristol somerset coalfield being proximal to south wales on the mid pennsylvanian variscan front results show an overall consistency between the two basins and suggest a common gene pool and vegetational physiognomy as well as a general stasis through time based on relatively stable environmental and growth conditions the study confirms that even unrevised historical collections can provide some data to help understand the dynamics of these systems however it also underlines the importance of taxonomy in such studies as it helps improve both the biostratigraphical and biogeographical resolution

stable isotopic composition of precipitation in the semi arid north central portion of the us great plains abstract where data are available hydrologic studies may use stable oxygen and hydrogen isotopes to investigate groundwater surface water interaction groundwater recharge and advective diffusive transport to estimate groundwater ages or to unravel paleohydrology such studies require that the isotopic composition of precipitation be known as precipitation is a major input to groundwater and surface water systems oxygen 18 18 o and deuterium 2 h data for precipitation are lacking for the semi arid portion of the north central great plains of the us and thus there is need to establish additional meteoric water lines as isotope input functions across the region as well as to develop better understanding of the isotopic climate linkages that control oxygen and hydrogen isotope ratios in precipitation this study examines the 18 o and 2 h composition of precipitation for a representative site near north platte nebraska in the semi arid north central great plains during the years 1989 through 1994 oxygen 18 values range from 30 5 to 1 7 deuterium values range from 228 to 11 yearly arithmetic mean values for the north platte station are 9 8 and 71 respectively weighted yearly means for 18 o and 2 h over the 6 year period were 9 6 and 69 respectively north platte values show a strong isotopic enrichment between winter and summer precipitation and a strong 18 o t correlation r 2 0 845 for mean monthly values of 0 54 per degree celsius the local meteoric water line for the site is 2 h 7 66 18 o 4 96

speculative reconstruction of the mojave snow lake fault implications for paleozoic and mesozoic orogenesis in the western united states available evidence suggests that the mojave snow lake fault a major early cretaceous dextral fault with up to 400 km displacement formerly existed in what is now the axial part of the sierra nevada batholith regional relations suggest that the fault formerly continued in western nevada the mojave desert and in rocks now exposed in the salinian block restoration of 400 km of early cretaceous dextral displacement on the mojave snow lake fault leads to speculative but testable reconstructions of mesozoic and paleozoic tectonic features of california and nevada insights derived from these reconstructions include the following 1 two regionally extensive jurassic thrust belts of opposed vergence appear to have intersected in the northern sierra nevada the eastern east vergent thrust belt which includes the fencemaker and liming thrusts in western nevada and several east vergent thrusts in the northern sierra may be a contractional belt along which an early jurassic interarc or marginal basin was closed in middle to late jurassic time the western west vergent thrust belt is part of the classic nevadan orogen of the western klamath mountains and the western sierra metamorphic belt in which collisions and or thrusting of various island arc terranes occurred during middle and late jurassic time 2 the early mesozoic continental arc included paired belts of triassic jurassic blueschist and melange and igneous rocks including late triassic and younger plutons and volcanic rocks this conclusion is not new but the reconstruction provides a slightly different geometry than previously thought 3 sonomia the late paleozoic island arc terrane of the western u s may have formed a relatively narrow belt extending from northwestern nevada to the latitude of the western mojave desert the geologic development of the paleozoic basement complex of sonomia was very different from that of the cordilleran miogeocline in death valley and the mojave desert requiring that a continuation of the sonoma suture belt or golconda thrust must have extended southward through the sierra nevada batholith to the mojave region 4 a heterogeneous belt of permian to triassic or triassic deformation in the mojave and eastern sierra nevada together with the golconda allochthon in nevada may represent the protracted response to the collision of sonomia with the western margin of north america the contractional deformation continued during the evolution of the early mesozoic continental arc 5 several predictions can be made about the nature of concealed basement within the sierra nevada batholith and within western nevada the reconstruction suggests that elements of the antler and sonoma orogenic belts should underlie areas of the batholith and western nevada as a result of northward displacement along the mojave snow lake fault from the western mojave and southern sierra nevada

isotopic composition of precipitation in italy a first overall map abstract composite monthly samples of atmospheric precipitation were collected over different periods of time ranging from one to seven years at 77 different locations throughout italy these samples were measured for their oxygen and hydrogen isotopic composition to obtain basic information for hydrological and meteorological studies in this area on the basis of the results obtained a first map of the isotopic composition of precipitations in italy has been drawn up the main features of this map are the following 1 no isotopic latitudinal gradient has been found along the tyrrhenian coast from sicily to the italian french border despite the considerable range of latitude 2 a minor latitudinal gradient is found in the southeasternmost section of the country apulia partially favored by the local morphology 3 a marked shadow effect of the apennines is apparent along the southern section of the po valley and along the central section of the adriatic coast 4 the contribution of water vapor from the northernmost section of the adriatic sea affects the eastern and central sections of the po plain 5 the shadow effect of the alps is considerably smaller than expected 6 the isotopic vertical gradients calculated in nine different areas and based on groups of two to five different stations vary but are essentially close to about 0 2 100 m 7 when mean monthly temperature values were available their relationship with the isotopic composition of precipitation was found to be on average very poor 8 the relationship between mean 18o and mean d calculated for the collection locations shows shifts of both the slope and the deuterium excess when compared to the global meteoric water line these shifts are different for northern central and southern italy 9 in a few cases anomalously low monthly values suggest the existence of pronounced amount effects

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

effects of a beaver pond on runoff processes comparison of two headwater catchments abstract natural variations in concentrations of 18 o d and h 4 sio 4 in two tributary catchments of woods lake in the west central adirondack mountains of new york were measured during 1989 1991 to examine runoff processes and their implications for the neutralization of acidic precipitation by calcium carbonate treatment the two catchments are similar except that one contained a 1 3 ha beaver pond evaporation from the beaver pond caused a seasonal decrease in the slope of the meteoric water line in stream water from the catchment with a beaver pond wo2 no corresponding change in slope of the meteoric water line was evident in stream water from the other catchment wo4 nor in ground water nor soil water from either catchment indicating that evaporative fractionation was not significant application of a best fit sine curve to 18 o data indicated that base flow in both catchments had a residence time of about 100 days ground water from a well finished in thick till had the longest residence time 160 days soil water from the o horizon and b horizon had residence times of 63 and 80 days respectively water previously stored within each catchment pre event water was the predominant component of streamflow during spring snowmelt and during spring and autumn rainfall events but the proportion of streamflow that consisted of pre event water differed significantly in the two catchments the proportion of event water rain and snowmelt in wo2 was smaller than at wo4 early in the spring snowmelt of march 13 17 1990 but the proportions of source water components for the two catchments were almost indistinguishable by the peak flow on the third day of the melt the event water was further separated into surface water and subsurface water components by utilizing measured changes in h 4 sio 4 concentrations in stream water during the snowmelt results indicated that subsurface flow was the dominant pathway by which event water reached the stream except during the peak flow of a rain on snow event on the last day of the melt streamflow from a spring rain storm with dry antecendent conditions two months later may 16 18 1990 was less than 5 event water at peak flow in wo2 and 26 in wo4 this change from the runoff pattern in march is attributed to retention of event water in the beaver pond favored by relatively low pre event storage and isothermal nonstratified conditions in the pond that allowed mixing streamflow during several autumn storms was about 15 25 event water at peak flow in wo4 the highest values for event water were associated with wet antecedent moisture conditions these results indicate that a beaver pond can significantly affect the downstream delivery of event water through evaporation and mixing but provides minimal retention during large runoff events such as snowmelt beaver ponds are expected to provide greater opportunity for neutralization of acidic waters during most of the year in catchments treated with calcium carbonate but little neutralization effect during snowmelt