hummocky cross stratification and megaripples a geological double standard abstract hummocky cross stratification in ancient sedimentary deposits is considered to be diagnostic of inner shelf storm deposits the geometry of the cross strata sets implies a low relief oval bedform of a few meters spacing orientation is poorly defined or random hummocky cross strata sets have been attributed to the action of strong storm wave surges megaripples of 2 5 m spacing are typical responses of the inner atlantic shelf of north america to storm flows side scan sonar records have shown that megaripples on the inner shelf are commonly hummocky oval to circular in plan view and lack asymmetry box cores and vibracores reveal gently inclined to horizontal lamination as the characteristic primary structure the megaripples am produced by combined flow storm currents these are alongcoast geostrophic flows with a mean flow component of 20 60 cm sec 1 a high frequency wave orbital current of similar or weaker intensity is present but its role in megaripple formation is subordinate to that of the mean flow the high velocity coastal margin of the flow is often jetlike and downwelling in nature and is characterize by a down current decrease in sand flux and rapid deposition of sand the bottom boundary layer of such flows is characterized by dense sediment suspensions 40 60 mgl 1 and is highly turbulent due to the interaction of the mean flow and wave orbital current components eddy diffusivity up to 200 cm2 sect at 40 cm above the bed sand transport in this coastal boundary zone is obliquely offshore but neither the density of the sediment suspension nor storm surge ebb appear to be important driving forces it is difficult to account for either modern hummocky megaripples or ancient hummocky cross stratification as responses to purely oscillatory flows combined flow currents are the typical response of mostmodern shelves and epicontinental seas to storms and presumably were so in the past hummocky cross stratified beds are generally too thick 20 80 cm to be accounted for by in situ resuspension they are more likely to have been despoited by combined flow currents in areas where these currents were experiencing a downstream velocity decrease and sediment deposition throughout much of the storm s duration evidence for strong scour in swales between hummocks and the smoothly rounded surface of the hummocks suggests a transitionlike bed regime measurements on the atlantic shelf likewi e suggest a transitionlike regime whose boundary layer is characterized by lower velocity than the transitional regime of unidirectional flow in flumes but more intense turbulence and a higher suspended sand concentration the lack of normal cross bedding in bothmodern and ancient hummocky bedforms indicates that these features did not migrate this characteristic may be a consequence of the complex trajectories followed by near bottom water particles in response to combined flow currents

gzhelian asselian palaeoaplysina microencruster reef community in the taishaku and akiyoshi limestones sw japan implications for late paleozoic reef evolution on mid panthalassan atolls abstract a palaeoaplysina microencruster reef community is recognized in the gzhelian asselian interval of the taishaku and akiyoshi limestones in sw japan which represent accreted panthalassan atoll carbonates in a reef core area of the atoll the alga palaeoaplysina acted as a framebuilder and was associated with various binders e g tubiphytes archaeolithoporella cystoporate bryozoans and microbialites and sediment bafflers such as fenestrate and cryptostomate bryozoans and phylloid algae in a subtidal environment of the back reef area palaeoaplysina and phylloid algae flourished as sediment bafflers a microbial community including tubiphytes and sessile foraminifers was predominant in a very shallow peritidal environment of the back reef area palaeoaplysina was distributed mainly along the northern margin of pangea and is regarded as a boreal element during gzhelian asselian time its distribution extended to the tropical or subtropical panthalassa ocean due to global cooling on the akiyoshi atolls the palaeoaplysina microencruster community was succeeded by a sponge microencruster community in the late early permian the timing of this biotic turnover is similar to that of a change in climate from icehouse to greenhouse conditions and coincides with superplume activity beneath the mid panthalassa ocean

variability of unsaturated bromide fluxes as measured through a layered volcanic vadose zone in new zealand the measured drainage fluxes through a layered volcanic vadose zone exhibited high spatial variability as a consequence of heterogeneous flow conditions the drainage flux variability was quantified using automated equilibrium tension lysimeters installed in close proximity and resulted in high variability in the br masses recovered from a conservative tracer experiment the primary cause of the heterogeneous flow was attributed to textural changes occurring at the interface between volcanic layers resulting in development of funnel flow patterns and further enhanced by the existence of hydrophobic conditions the br recoveries in individual automated equilibrium tension lysimeters were used to determine the corresponding variable sizes of the surface areas contributing drainage to the lysimeters the tracer experiment confirmed the existence of unsaturated lateral transport occurring at the sloping interface of the coarse taupo ignimbrite material with the silty palaeosol layer at approximately 4 2 m depth this study demonstrates that measurements of both flux and solute concentrations at multiple locations are essential when heterogeneous flow is suspected to be present to be able to determine reliable estimates of contaminant leaching through the vadose zone at the plot scale copyright 2013 john wiley sons ltd

stratigraphical and δ13c records of permo carboniferous platform carbonates south china responses to late paleozoic icehouse climate and icehouse greenhouse transition abstract little attention has been focused on the stratigraphical imprints of the late paleozoic ice age on the equatorial eastern paleo tethys an integrated study of biostratigraphy microfacies and stable carbon isotope stratigraphy was carried out on pennsylvanian middle guadalupian carbonates of the gongchuan section in the bama platform south china it records seven cooling and two warming pulses in the pre kungurian interval comparing with ice proximal stratigraphical records and far field indirect proxies in lower latitudes a kungurian negative 13 c excursion from 4 4 at the base of the kungurian to 1 6 recorded only in the subequatorial belt is documented here it is followed by a global positive 13 c trend reaching 5 3 near the cisuralian guadalupian boundary seven third order shallowing upward cycles are reported for the first time from the kungurian succession the duration of each cycle is estimated to ca 1 myr these cycles are interpreted as being of glacioeustatic origin and mainly driven by long period modulations of obliquity 1 2 myr under major p co 2 decreasing condition this interpretation is supported by recent climate ice sheet modeling and cenozoic glaciation studies which argue that astronomical forcing will be amplified by large magnitude perturbations in the carbon cycle when only localized ice centers persist our results emphasize the need for integration of sedimentological and paleoclimatological proxies in elucidating the dynamics of the deglacial phases of the late paleozoic ice age

late paleozoic glacial episodes in gondwanaland reflected in transgressive regressive depositional sequences in euramerica the late paleozoic glaciation of gondwanaland comprised two short episodes in the famennian i and visean ii confined to brazil and adjacent northwest africa and a long episode that started in the namurian iiia of eastern australia and bolivia argentina expanded to cover much of gondwanaland in the stephanian asselian iiib and collapsed in the early sakmarian iiic dropstones in eastern australia indicate that small ice centers lingered to the kazanian across the belt of low latitudes north of gondwanaland short ranging fossils in widespread shallow marine and paralic deposits indicate synchronous deposition of transgressive regressive sequences in different parts of euramerica these sequences correlate with glacial events in gondwanaland at three levels a four major regressions in euramerica in the famennian 1 visean 2 namurian 3 stephanian 4 and the tastubian transgression that preceded the sterlitamakian regression 5 also recorded in gondwanaland correlate with glacial episodes i ii and iiia iiib and iiic b the time interval of cyclothemic deposition in euramerica brigantian or latest visean to sterlitamakian correlates with that of glacial episode iii and c the dominant period of the euramerican cyclothems as estimated from the middle and late pennsylvanian deposits of the mid continent of north america and of the thickest known gondwanaland glacigenic sediment the earliest permian lyons group of western australia is 0 4 ma equivalent in turn to the long orbital eccentricity period of the quaternary ice age and the dominant period of fluctuation of the late miocene antarctic ice cap the three levels of correlations confirm wanless and shepard9s 1936 hypothesis that the late paleozoic cyclothems are controlled largely by sea level fluctuations related to the gondwanaland glaciation

hypersaline burial diagenesis delineated by component isotopic analysis late paleozoic limestones west texas abstract pennsylvanian to lower permian cyclic platform carbonates from the southwest andrews area of west texas are now 3 km below the land surface isolated samples of brachiopod shell zones of calcite cement and saddle dolomite from limestone cores of the southwest andrews oilfields have been analyzed isotopically to determine if 1 diagenesis is dominated by early meteoric processes as suggested by bulk rock isotopes 2 whether significant burial diagenesis occurred in hypersaline waters and 3 whether most burial cements are allochthonous or internally derived bulk isotopic analyses of limestones show systematic variation in 13c and 18o according to length of subaerial exposure and stratigraphic position chemically zoned calcite cements show four growth stages stage 1 and 2 cements have average 13c values of 4 6o oo and average 18o of 5 0o oo and most are interpreted to have precipitated during subaerial exposure in meteoric water a few stage 1 cements with average 13c values of 4 7o oo and 18o of 1 4o oo apparently precipitated below the sediment surface from modified seawater in a sulfate reduction zone stage 3 and 4 calcite cements precipitated after compaction and compose up to 25 of the total rock volume they have 13c values 0 2o oo to 4 4o oo that vary according to stratigraphic position and are similar to bulk rock samples of the host limestone the 13c values indicate local derivation by dissolution of adjacent rock the 18o values of stage 3 and 4 cement 5 5o oo to 3 5o oo are indistinguishable from stages 1 and 2 cements precipitated from meteoric water the decrease in 18o expected from elevated temperatures during burial present formation temperature of 55 c is negated by precipitation from a late permian brine with 18o values of 5o oo stages 3 and 4 calcite and saddle dolomite cements have 87sr 86sr values that are lower than 87sr 86sr values for contemporaneous marine carbonate 0 70830 this is probably due to incorporation of sr with low 87sr 86sr values 0 70672 to 0 70682 also from the late permian hypersaline brine the southwest andrews area has several diagenetic features that are probably more common in ancient limestone than previously recognized 1 burial cements have 18o values similar to meteoric cements when precipitated from hypersaline waters with 18o values 5o oo greater than contemporary seawater 2 deep burial cements have 13c values similar to the bulk rock because carbon is derived from pressure dissolution of nearby carbonate 3 bulk rock isotope values are characteristic of marine limestones subjected to meteoric diagenesis even though they have suffered substantial deep burial diagenesis this study clearly illustrates the value of analyzing diagenetic components to accurately understand porosity evolution in limestones

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

deglacial warming of the northeastern atlantic ocean correlation with the paleoclimatic evolution of the european continent abstract isotopic micropaleontologic and pollen analyses of deep sea cores from the bay of biscay and the northeastern atlantic ocean show that the deglacial warming of this oceanic area was closely correlated with the paleoclimatic evolution of the adjacent european continent temperatures were at least as warm as those of today in the bay of biscay between 13 300 and 11 000 b p coinciding with the combined bolling allerod warm continental events a major spread of polar water occurred between 11 000 and 10 000 b p during this event which coincides with the younger dryas continental cold event marine temperatures were almost as low as those of the last glacial maximum the final deglacial warming of the norteastern atlatntic ocean occurred during the following 3000 yr

late pennsylvanian glaciation evidence of icehouse conditions from canyon and cisco units midland basin texas abstract the late paleozoic has long been recognized a time of significant continental glaciation associated with high frequency high amplitude glacioeustasy although precise assessment of glacioeustatic amplitudes are difficult to extract from the stratigraphic record best approximations may be possible by analyzing spatial and temporal distributions of depositional facies utilizing several wells across the study area we used detailed sedimentologic description and depositional facies analysis from 12 wells and applied rigorous cycle stacking pattern analysis exposure surfaces recognition and wireline logs to correlate timelines across the wells on the basis of the high resolution sequence stratigraphic framework built for the scurry area canyon reef operators sacroc field a highly resolved glacioeustatic curve was generated for latest desmoinesian to the latest virgilian our eustatic curve suggests that the missourian and virgilian stages of the late pennsylvanian are characterized by high frequency high amplitude eustatic fluctuations the missourian stage was a period dominated grainstone capped cycles that are isopachous and conformable these cycles reflect a eustatic amplitude of at least 37 m with an average duration of 100 ka suggesting the dominance of short term eccentricity signal the virgilian stage is far more complicated and is characterized by highly shingled cycles compared to the missourian stage deeper water phylloid boundstone and calichified shoal complex grainstones are juxtaposed next to each other which suggests a stronger eustatic amplitude 40 m compared to the missourian stage although the eustatic amplitude of the virgilian cycles is similar to those of the missourian cycles they have a longer frequency 343 ka representative of long term eccentricity we conclude that the late pennsylvanian stratigraphy of the sacroc field in the midland basin records extensive continental glaciation during the missourian stage and increased and reached an acme during the virgilian stage

transgressive depositional systems of the mississippi delta plain a model for barrier shoreline and shelf sand development abstract depositional sequences generated in the mississippi river delta plain consist of a regressive and a transgressive component the transgressive component has been considerably less studied but accounts for the majority of the surface area on the lower mississippi river delta plain and up to 50 percent of the total sequence thickness in shallow water deltas the development and preservation of transgressive depositional systems in abandoned delta complexes follows the process of transgressive submergence in which the horizontal component of reworking occurs during shoreface retreat combined with a vertical component of submergence acting to preserve the sequence the evolution of transgressive depositional systems in each of the abandoned holocene mississippi river delta complex s can be summarized in a three stage model beginning with stage 1 an erosional headland and flanking barriers in this stage regressive sand deposits contained within abandoned deltaic headlands are reworked by the eroding shoreface and dispersed longshore into contiguous flanking barriers enclosing restricted interdistributary bays submergence of the delta plain during relative sea level rise generates an intradeltaic lagoon separating the former stage 1 sand body from the shoreline forming stage 2 a transgressive barrier island arc the landward migrating barrier island arc is unable to keep pace with relative sea level rise and the retreating mainland shoreline resulting in submergence and the formation of stage 3 an inner shelf shoal following submergence the former barrier island arc sand body continues to be reworked into a marine sand body on the inner continental shelf during stage 3 this sequence of coastal evolution provides direct evidence of barrier island formation with each stage producing a distinctive stratigraphic signature the current sea level rise models of shoreface retreat and in place drowning developed for the u s atlantic continental shelf do not adequately explain either the morphology or the stratigraphy of transgressive mississippi river delta sand bodies current models of mississippi deltaic stratigraphy emphasize the deep water artificially maintained balize delta which differs considerably from the shallow water shelf phase delta complexes that are the primary depositional constituents of he holocene mississippi river delta plain

field tracer investigation of unsaturated zone flow paths and mechanisms in agricultural soils of northwestern mississippi usa summary in many farmed areas intensive application of agricultural chemicals and withdrawal of groundwater for irrigation have led to water quality and supply issues unsaturated zone processes including preferential flow play a major role in these effects but are not well understood in the bogue phalia basin an intensely agricultural area in the delta region of northwestern mississippi the fine textured soils often exhibit surface ponding and runoff after irrigation and rainfall as well as extensive surface cracking during prolonged dry periods fields are typically land formed to promote surface flow into drainage ditches and streams that feed into larger river ecosystems downward flow of water below the root zone is considered minimal regional groundwater models predict only 5 or less of precipitation recharges the heavily used alluvial aquifer in this study transport mechanisms within and below the root zone of a fallow soybean field were assessed by performing a 2 m ring infiltration test with tracers and subsurface monitoring instruments seven months after tracer application 48 continuous cores were collected for tracer extraction to define the extent of water movement and quantify preferential flow using a mass balance approach vertical water movement was rapid below the pond indicating the importance of vertical preferential flow paths in the shallow unsaturated zone especially to depths where agricultural disturbance occurs lateral flow of water at shallow depths was extensive and spatially non uniform reaching up to 10 m from the pond within 2 months within 1 month the wetting front reached a textural boundary at 4 5 m between the fine textured soil and sandy alluvium now a potential capillary barrier which prior to extensive irrigation withdrawals was below the water table within 10 weeks tracer was detectable at the water table which is presently about 12 m below land surface results indicate that 43 of percolation may be through preferential flow paths and that any water breaking through the capillary barrier as potential recharge likely does so in fingers which are difficult to detect with coring methods in other areas where water levels have declined and soils have similar properties the potential for transport of agricultural chemicals to the aquifer may be greater than previously assumed

stratigraphy and structure of coalbed methane reservoirs in the united states an overview stratigraphy and geologic structure determine the shape continuity and permeability of coal and are therefore critical considerations for designing exploration and production strategies for coalbed methane coal in the united states is dominantly of pennsylvanian cretaceous and tertiary age and to date more than 90 of the coalbed methane produced is from pennsylvanian and cretaceous strata of the black warrior and san juan basins investigations of these basins establish that sequence stratigraphy is a promising approach for regional characterization of coalbed methane reservoirs local stratigraphic variation within these strata is the product of sedimentologic and tectonic processes and is a consideration for selecting completion zones coalbed methane production in the united states is mainly from foreland and intermontane basins containing diverse compressional and extensional structures balanced structural models can be used to construct and validate cross sections as well as to quantify layer parallel strain and predict the distribution of fractures folds and faults influence gas and water production in diverse ways however interwell heterogeneity related to fractures and shear structures makes the performance of individual wells difficult to predict

comparison of changes in vegetation in northeast greece with records of climate variability on orbital and suborbital frequencies over the last 450 000 years abstract a new direct pollen orbital tuning procedure based on a correspondence between changes in certain vegetation elements and march and june perihelion configurations is applied to the tenaghi philippon record northeast greece the development of a refined chronological scheme allows comparisons to be made with records of climate variability from the north atlantic as well as of global sea level ice volume and atmospheric co2 content on orbital frequencies the comparison reveals a close correspondence between relative ice volume extent and tree population size during glacial intervals during interglacial and interstadial periods the degree of forest development is more closely associated with high latitude insolation and related climate regimes rather than extent of residual ice volume on suborbital frequencies the greek record shows similar repeat times in peaks of steppe vegetation with north atlantic ice rafting events but the amplitude of this variability in the two records is not always proportional overall what emerges is that the major shifts in the relative abundance of forest v open vegetation communities at tenaghi philippon on orbital and suborbital frequencies over the last 450 000 years are coherent with high latitude changes affecting atmospheric and oceanic circulation glacial decreases in atmospheric co2 content contributed to the elimination of tree populations by exacerbating water stress conditions during arid intervals but do not appear to be the primary driver of the observed vegetation changes at this latitude variations in co2 levels in the order of 40 ppmv between different interglacial interstadials periods with adequate moisture availability appear to have had a limited effect on the nature and size of tree populations

last interglacial climates the last interglacial commonly understood as an interval with climate as warm or warmer than today is represented by marine isotope stage mis 5e which is a proxy record of low global ice volume and high sea level it is arbitrarily dated to begin at approximately 130 000 yr b p and end at 116 000 yr b p with the onset of the early glacial unit mis 5d the age of the stage is determined by correlation to uranium thorium dates of raised coral reefs the most detailed proxy record of interglacial climate is found in the vostok ice core where the temperature reached current levels 132 000 yr ago and continued rising for another two millennia approximately 127 000 yr ago the eemian mixed forests were established in europe they developed through a characteristic succession of tree species probably surviving well into the early glacial stage in southern parts of europe after ca 115 000 yr ago open vegetation replaced forests in northwestern europe and the proportion of conifers increased significantly farther south air temperature at vostok dropped sharply pulses of cold water affected the northern north atlantic already in late mis 5e but the central north atlantic remained warm throughout most of mis 5d model results show that the sea surface in the eastern tropical pacific warmed when the ice grew and sea level dropped the essentially interglacial conditions in southwestern europe remained unaffected by ice buildup until late mis 5d when the forests disappeared abruptly and cold water invaded the central north atlantic ca 107 000 yr ago

time dependent changes for midcontinent pennsylvania black shales u s a abstract three types of midcontinent north american black shale types have been recognized based on metal content organic carbon contents sulfur isotopes and various other sedimentological and paleontological characteristics that may reflect fluctuations in bottom water oxygenation during deposition near shore middle pennsylvanian black shales exemplified by the mecca quarry shale member of indiana typically yield degree of pyritization dop values near 0 65 the highest measured in the study consistent with relatively but not fully anoxic conditions of sedimentation dop values for heebner type shales most prevalent in the upper pennsylvanian average 0 27 0 35 barely in the dysaerobic range which is difficult to reconcile with an origin for black shale dependent upon upwelling bottom water positive correlations exist between dop metal values and total organic carbon toc in black shale units through the pennsylvania these changes can be related to organic carbon production and published sea level fluctuations suggesting a change in black shale character in the midcontinent from the middle to late pennsylvanian consistently decreasing values for dop and toc through time suggest the likelihood of a progressive ventilation or improved bottom water oxygenation accompanied by a reduced rate of input from terrestrial organic matter during this time interval

did glacials start with global warming abstract correlation of paleoclimatic evidence with orbital changes shows that the build up of polar ice accelerated when low obliquity coincided with perihelion in northern hemisphere winter under low obliquity the insolation was channeled to the tropics at the expense of both polar caps as perihelion moved from winter solstice toward spring equinox the solar beam in astronomic winter and spring became stronger than in summer and autumn this orbital configuration under climate conditions like today would lead to warming of tropical oceans but cooling of the polar regions the areally weighted global mean surface temperature which is dominated by the low latitudes would increase consequently during the first millennia the early glacial ice build up was most likely accompanied by global warming it was the associated increase of meridional insolation and temperature gradients which were instrumental in the transition to a glacial a significant part of the current global warming is due to the gradual temperature increase of the tropical oceans as the changing orbital configuration today resembles that of the last interglacial glacial transition the warming is likely to have a natural component

epigenetic sulfide mineralization associated with pennsylvanian paleokarst in eastern iowa u s a abstract paleokarst associated sulfide bearing mineral deposits are wide spread in the paleozoic carbonate rocks of eastern iowa minerals occur in nodules enclosed in karst filling mudstones as sandstone cements and as surface coatings on and fracture fillings in foundered carbonate rock clasts mineralogy and paragenetic sequence vary among the occurrences sulfur isotopic compositions exhibit wide variations within and among deposits 34 s 33 8 to 35 1 oxygen isotopic compositions of fracture filling calcite spars 18 o 8 41 to 3 60 are similar to the isotopic compositions of their carbonate rock hosts calcite spars are somewhat depleted in 13 c relative to host rock 13 c spars 5 66 to 0 24 vs 1 54 to 1 21 host rock results of mineralogic paragenetic and isotopic investigations suggest that 1 minerals are products of multiple events operating on a local rather than a regional scale 2 spatially disjunct fracture filling mineral deposits exposed in the same quarries are probably not cogenetic with paleokarst associated deposits 3 paleokarst filling calcite spars formed at near surface temperatures and 4 paleokarst associated deposits are probably not cogenetic with upper mississippi valley zn pb pitch flat deposits

sediment supply as a control on the variability of sequences an example from the late namurian of northern england currently variations in accommodation space are seen as the major control on facies stacking patterns and stratal geometries this paper emphasizes the importance of the sediment supply variable through the use of a regional stratal surface based interpretation of the late namurian stratigraphy of northern england late highstand palaeogeographies and stacking pattern variations highlight spatial and temporal variations in sediment supply which promote the contemporaneous development of prograda tional aggradational and retrogradational stacking patterns this questions the derivation of relative sea level curves from specific stacking patterns and highlights the potential for miscorrelation in areas with major sediment supply variations

stratigraphic and biofacies patterns in the middle pennsylvanian magoffin marine unit in the appalachian basin u s a abstract the magoffin marine unit is a middle pennsylvanian age interval of marine strata that directly overlies the taylor copeland and correlative coal zones in the appalachian basin for this study the magoffin was measured described and sampled at 17 localities along a northeast to southwest transect in the center of the middle pennsylvanian outcrop belt in eastern kentucky and west virginia throughout the study area the base of the magoffin is characterized by a thin dark highly fossiliferous limestone with a brachiopod dominated fossil assemblage the limestone base is usually overlain by a fining upward sequence consisting of fossiliferous dark shales or mudstones with mollusk dominated assemblages these dark mudstones include a fissile black shale with a distinctive posidonia fauna deposited over part of the study area the lower fining sequence is overlain by a thicker coarsening sequence bearing brachiopod dominated fossil assemblages the lower beds of the magoffin particularly the basal limestone are persistent and relatively uniform throughout the study area in contrast strata in the upper part of the magoffin sequence show a high degree of geographic variability with localities in the southwestern half of the study area showing two successive thick coarsening upward sequences of strata while those to the northeast record a single thinner coarsening upward sequence the widespread uniform nature of the basal magoffin limestone appears to indicate rapid transgressive flooding of the coal swamp and associated environments accompanied by a hiatus in clastic influx into the magoffin seaway nearshore brachiopod faunas were replaced by deeper water possibly dysaerobic adapted mollusk faunas as transgression progressed culminating in the fissile black shales and monotaxic posidonia fauna deposited beneath a localized pycnocline during maximum transgression the onset of regression is indicated by the reverse of the stratigraphic sequence of faunas observed during transgression and by the return of rapid clastic influx into the basin

sedimentology and paleontology of a carboniferous log jam a localized sandstone split in the mary lee coal early pennsylvanian langsettian of the black warrior basin alabama has a channel form geometry and preserves a concentrated log and gravel pebbles cobbles and boulders assemblage at the top of the fill sequence gravel lithotypes within and amongst rooting structures of lycopsid cordaitean and calamitean trees are indicative of an appalachian orogenic provenance and support an allochthonous origin for some of the logs in addition a skolithos ichnological assemblage within the channel is indicative of opportunist colonization during channel fill a low sinuosity geometry characterizes the overall channel form belt exhibiting a general northwesterly trend paleocurrent measurements from the cross bedded sandstone at the margin of the channel belt indicate flow was to the northwest log orientations at these sites are subperpendicular to perpendicular to the overall sediment transport direction and are interpreted to represent an ancient log jam the genesis of the fluvial channel the introduction and emplacement of the concentrated log assemblage the effects of this floating log accumulation on sedimentation within the channel and the relationship between paleocurrent and log orientation are discussed the red river located in the southern united states is used as a modern analog for comparative purposes

morphology and origin of an erosion surface cut into the bad heart formation during major sea level change santonian of west central alberta canada abstract marine sandstones of the early santonian bad heart formation are up to 50 m thick and are underlain and overlain by marine mudstones of the muskiki and puskwaskau formations respectively our examination of 395 well logs in this stratigraphic interval allowed the recognition of many distinctive well log markers correlations of these markers at and below the base of the bad heart indicates a basinward depositional thinning of about 10 cm km the bad heart itself thins from 50 to 2 m northeastward over a distance of 100 km although part of this thinning is probably depositional the truncation of gamma ray and resistivity log markers within the bad heart indicates that there is at least 38 m of erosional topography a paleotopographic map and three dimensional mesh diagram show 1 a relatively smooth high level terrace ending seaward at 2 a main erosive bevel trending nw se across the area the bevel grades seawards into 3 a topography of bumps and hollows which fades into 4 a relatively smooth basin plain most of the erosion was probably due to erosional shoreface retreat through wave scour processes during a major relative lowering of sea level the upper parts of the erosion surface were probably subaerially exposed during maximum lowstand of sea level in outcrop the erosion surface is marked by a thin pebble lag which is in turn overlain by marine mudstones the contact between the conglomerate and underlying sandstone is sharp and locally irregular but gives no hint of the presence of deep regional erosion which can only be demonstrated by using the subsurface data

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

centennial scale vegetation dynamics and climate variability in se europe during marine isotope stage 11 based on a pollen record from lake ohrid abstract to better understand climate variability during marine isotope stage mis 11 we here present a new centennial scale resolution pollen record from lake ohrid balkan peninsula derived from sediment cores retrieved during an international continental scientific drilling program icdp campaign our palynological data augmented by quantitative pollen based climate reconstructions provide insight into the vegetation dynamics and thus also climate variability in se europe during one of the best orbital analogues for the holocene comparison of our palynological results with other proxy data from lake ohrid as well as with regional and global climate records shows that the vegetation in se europe responded sensitively both to long and short term climate change during mis 11 the chronology of our palynological record is based on orbital tuning and is further supported by the detection of a new tephra from the vico volcano central italy dated to 410 2 ka our study indicates that mis 11c 424 398 ka was the warmest interval of mis 11 the younger part of the interglacial i e mis 11b 11a 398 367 ka exhibits a gradual cooling trend passing over into mis 10 it is characterized by considerable millennial scale variability as inferred by six abrupt forest contraction events interestingly the first forest contraction occurred during full interglacial conditions of mis 11c this event lasted for 1 7 kyrs 406 2 404 5 ka and was characterized by substantial reductions in winter temperature and annual precipitation most notably it occurred 7 ka before the end of mis 11c and 15 ka before the first strong ice rafted debris event in the north atlantic our findings suggest that millennial scale climate variability during mis 11 was established in southern europe already during mis 11c which is earlier than in the north atlantic where it is registered only from mis 11b onwards

sea level curve for pennsylvanian eustatic marine transgressive regressive depositional cycles along midcontinent outcrop belt north america at least 55 cycles of marine inundation and withdrawal are recognized in the mid desmoinesian to mid virgilian midcontinent outcrop sequence in north america they range from widespread major cycles classic cyclothems with deep water facies extending across the northern shelf through intermediate cycles persisting as marine horizons across the shelf to minor cycles developed on the lower shelf or as parts of major cycles biostratigraphic differentiation of the cycles should establish interbasinal correlation on a scale fine enough to allow evaluation of differential tectonics and sedimentation sequential groupings of cycles are more irregular than proposed megacyclothems or mesothems but they may be obscured by the distinctness of the major cyclothems estimates of cycle periods range from about 40 to 120 x 10 sup 3 yr for the minor cycles up to about 235 to 400 x 10 sup 3 yr for the major cyclothems the range for all cycles corresponds well to the range of periods of earth s orbital parameters that constitute the milankovitch insolation theory for the pleistocene ice ages and it further supports gondwanan glacial control for the pennsylvanian cycles even though the dominant period of the major pennsylvanian cyclothems is up to four times longer than the dominant 100 000 yr period inmore the pleistocene the shapes of both curves display rapid marine transgression rapid melting of ice caps and slow interrupted regression slow buildup of ice caps which suggest similar linkages between the climatic effects of the orbital parameters and ice cap formation and melting at the two different scales widely separated in time 28 references 3 figures less

preferential flow in a sandy vadose zone 1 field observation abstract field experiments of water movement in the lower portion of an unsaturated zone i e vadose zone are far more difficult to conduct than those in the root zone thus our concept of the transport mechanism in the vadose zone is still primitive and mainly an extrapolation of our understanding of transport in the root zone recent results from field experiments conducted at the hancock agricultural research station indicated that water and solute applied uniformly to soil surfaces did not flow through the entire vadose zone by using dye tracing and profile excavation field experiments were conducted during the 1987 growing season to examine water flow patterns in the unsaturated zone of the central sand area of wisconsin csaw the results confirmed that preferential flow paths constitute the dominant flow pattern at this location water flowing through the root zone was funneled into concentrated flow paths that occupied only a small portion of the soil matrix in the vadose zone yet accounted for most of the transport the observed phenomena of preferential flow in a sandy vadose zone are discussed in this paper the mechanism and implications of preferential flow are presented in a companion paper

use of bed form climb models to analyze geometry and preservation potential of clastic facies and erosional surfaces based on a combination of walther s law of facies and bed form climb theory we propose a model that explains how erosion surfaces and vertical sequences of clastic strata are preserved where deposition occurs in channelized or locally erosional environments including fluvial and submarine channel deposits barred beaches and transgressive coastlines the model considers both lateral and vertical migration of a scour surface and its associated depositional products as in studies of bed form climb we recognize subcritical critical and supercritical climb of scour surfaces relative to adjacent depositional forms for a given erosion surface the amount of underlying material removed is dictated by the climb angle of the erosion surface preservation of sequences also d pends on whether conditions were relatively variable or invariable one important conclusion of this study is the recognition of the bed form climb angle s control on the thickness of a sedimentary facies estimates of paleochannel depth or paleowater depth based on facies thickness can be made only if the climb angle is zero by combining depositional models of fluvial nearshore and offshore facies it is theoretically possible to model depositional systems such as deltas and passive continental margins potential applications are limited by several factors including influence of sea level climatic fluctuations on sedimentation and variable migration of facies or nonideal behavior or sedimentary environments in addition negative climb angles or climb angles less than horizontal can result in the removal of large amounts of material such negative climb angles may be caused by drops in eustatic sea level and lowering of base levels of drainage systems we believe that this heuristic model has considerable potential in helping sedimentologists and stratigraphers predict the consequences of facies mi ration

duration of last interglacial conditions in northwestern greece a new astronomical calibration method for long pollen records from southern europe is applied to the last interglacial interval of the ioannina sequence northwest greece this shows that the last interglacial in this region as defined by the presence of forest communities lasted c 15 500 years from 127 300 to 111 800 yr b p interglacial conditions developed within marine isotope sub stage mis 5e and persisted into mis 5d lagging changes in global ice volume

last interglacial and early glacial enso although the link between insolation and climate is commonly thought to be in the high northern latitudes in summer our results show that the start of the last glaciation in marine isotope stage mis 5d was associated with a change of insolation during the transitional seasons in the low latitudes a simplified coupled ocean atmosphere model shows that changes in the seasonal cycle of insolation could have altered el nino southern oscillation enso variability so that there were almost twice as many warm enso events in the early glacial than in the last interglacial this indicates that ice buildup in the cooled high latitudes could have been accelerated by a warmed tropical pacific

climate change on tectonic time scales abstract observational and modeling studies relevant to climate change on tectonic time scales are reviewed probably the most significant climate result from this time scale involves inferences about nearly ice free conditions for some intervals of earth history some additional results suggest relatively rapid transitions between climate states modeling studies indicate that although tectonic changes significantly modify the atmosphere and ocean circulation in most cases such modifications do not appear to be sufficient to explain ice free climates increased atmospheric co2 levels 5 10 presentvalues may be needed to completely reconcile models and data although the co2 paradigm has received widespread attention in the last few years the results summarized herein indicate that co2 is only one of several important factors influencing climate i believe the time is appropriate for contemplating climate change on tectonic time scales in terms of a post co2 synthesis in which direct tectonic factors are approximately equal in importance to co2 fluctuations in the last few years modeling studies have progressed from a state of virtually no work on the topic to one where the models are in some respect ahead of the observations in the sense that data have not been compiled to test even some of the most basic model predictions in particular information is needed on past atmospheric co2 levels tropical sea surface temperatures seasonality of continental interiors and locations and production rates of deep waters initial steps are being taken to integrate observational and modeling activities on tectonic time scales and some of these shortcomings may be rectified over the next few years

the impact of climate change tectonism and hydrology on the formation of carboniferous tropical intermontane mires the springhill coalfield cumberland basin nova scotia abstract both climate and tectonism are influential in determining basin and mire hydrology in the rapidly subsiding intermontane basins of euramerica which formed in response to the variscan hercynian alleghenian orogeny however the record of climate change has been muted and may therefore go unrecognized the complex interplay of climate and tectonism in a tropical continental setting is recorded in the 4 km thick westphalian a b fill of the cumberland basin thick peat accumulation was favoured at the southern basin margin where rheotrophic forested mires 4 9 km wide flourished between basin axis rivers and coalesced alluvial fans derived from the cobequid highlands as a result of their geomorphic setting the thicker coals 4 3 m exhibit distinct areal zones piedmont inner mire and riverine evidence that the forest swamps were nourished both by rainfall and by groundwater discharge from alluvial fans includes the stratigraphic affinity of thick coals and basin margin conglomerates interfingering of distal fan sheetflood and mire deposits petrographic evidence of elevated ph partial gelification of tissues and predominance of the arboreous lycopsids lepidodendron and paralycopodites whereas such groundwater supply is crucial to maintenance of modern wetlands in drier periods a subhumid climate is implied coals at joggins further removed from groundwater discharge at the basin margin are less well developed a 600 m thick coal window within the fining and reddening upward basin fill sequence at springhill is inferred to represent a coincidence of optimal groundwater supply and net subsidence the ultimate decline of peat accumulation in the basin may reflect decrease in catchment area and fan size and loss of rainshadow as the cobequid massif was denuded and the basin filled the coal window ca 6 9 10 5 yr is punctuated by non marine cyclothems of coal grey sideritic mudrock and multistorey sandstone that share similar time frames with astronomic cycles of axial precession ca 1 4 10 4 yr the stress of related climate change is inferred to have caused peat accumulation to fall into disequilibrium with sediment flux and basin subsidence the late quaternary history of certain african mires illustrates the dramatic impact of climate change especially temperature and seasonality and orographic effects on tropical continental peat accumulation aspects of the groundwater recharge model may be applicable to the westphalian stephanian intermontane mires of spain and mesozoic coal basins of northern china

accommodation and sedimentary architecture of isolated icehouse carbonate platforms insights from forward modeling with carb3d abstract a fundamental control on the evolution of carbonate platforms is accommodation the space available for sediment deposition here we adopt a sensitivity analysis approach using the process based forward model carb3d to quantitatively investigate the sedimentary response of isolated carbonate platforms to individual accommodation drivers of eustasy subsidence and surface dissolution sediment production the mechanism invoked to fill accommodation is also investigated fourth order milankovich driven sea level cycles dominate icehouse carbonate sedimentology with 400 ky cycles modulating the effect of 100 ky cycles of comparable magnitude when both cycles are present both overwhelm higher frequency lower amplitude fifth order cycles which are rarely preserved on the platform top subsidence is a fundamental control on sedimentary stacking patterns sequence boundary frequency sbf and platform geometry with rapid subsidence increasing the preservation of platform top sequences most icehouse platforms are subject to extended periods of platform top exposure missed beats when the platform top remains emergent at a sea level maximum are common and create non milankovich sbfs furthermore during platform emergence surface lowering via surface dissolution also creates accommodation for the subsequent platform flooding event with surface dissolution rates in humid climates comparable to moderate rates of subsidence however accommodation generation by surface dissolution is self limiting in as much as accommodation generated by dissolution is rapidly refilled on flooding sediment production is a key control on unfilled accommodation which our simulations suggest is considerable on icehouse platforms increased shallow water 3 m depth sediment production enhances intra platform bathymetric relief between the margin and interior this is driven in large part by a higher sedimentation rate at the margin than in the interior platforms can be flooded to depths up to 45 m during marine transgressions and accommodation often remains unfilled there are two distinct phases of platform top sedimentation during the transgression and early highstand platform margins accumulate at a greater rate than interior sediments generating differential intra platform bathymetry subsequently accommodation in the interior fills by forced regression and progradation from the margins into the platform interior numerical forward models can augment our understanding of icehouse carbonate platform evolution by identifying the nature of the sedimentary response to individual controls they can thus contribute to improving characterization of carbonate reservoirs in icehouse platforms such as the large hydrocarbon fields in the north caspian and s e asia

preferential flow occurs in unsaturated conditions copyright 2011 john wiley sons ltd because it commonly generates high speed high volume flow with minimal exposure to solid earthmaterials preferential flow in the unsaturated zone is a dominant influence in many problems of infiltration recharge contaminant transport and ecohydrology by definition preferential flow occurs in a portion of a medium that is a preferred part whether a pathway pore or macroscopic subvolume there are many possible classification schemes but usual consideration of preferential flow includes macropore or fracture flow funneled flow determined by macroscale heterogeneities and fingered flow determined by hydraulic instability rather than intrinsic heterogeneity that preferential flow is spatially concentrated associates it with other characteristics that are typical although not defining it tends to be unusually fast to transport high fluxes and to occur with hydraulic disequilibrium within the medium it also has a tendency to occur in association with large conduits and high water content although these are less universal than is commonly assumed predictive unsaturated zone flow models in common use employ several different criteria for when and where preferential flow occurs almost always requiring a nearly saturated medium a threshold to be exceeded may be specified in terms of the following i water content ii matric potential typically a value high enough to cause capillary filling in a macropore of minimum size iii infiltration capacity or other indication of incipient surface ponding or iv other conditions related to total filling of certain pores yet preferential flow does occur without meeting these criteria my purpose in this commentary is to point out important exceptions and implications of ignoring them some of these pertain mainly to macropore flow others to fingered or funneled flow and others to combined or undifferentiated flow modes

eustatic and autocyclic influences on deposition of the lower pennsylvanian mary lee coal zone warrior basin alabama abstract deposition of marine strata associated with the lower pennsylvanian mary lee coal zone pottsville formation was controlled by the allocyclic mechanism of eustatic sea level change the vertical stacking of marine marginal marine and terrestrial facies indicates that this interval was deposited during a single transgression regression transgression cycle ravinement surfaces and associated autochthonous macro invertebrate and trace fossil assemblages record the landward retreat of the shoreline and abrupt deepening due to rapid rise in sea level these horizons are overlain by terrigenous clastic facies either tidal sand bodies or shelf mudstones which indicate shoaling due to progradation during the subsequent filling of the generated accommodation space although marine influence including the effects of tidal currents continued during the more terrestrial phases of deposition autocyclic factors including the control of paleotopography by differential compaction of buried peat bodies were also important in determining facies distribution

inferring flow types from dye patterns in macroporous soils in this study we exploit dye patterns to identify flow types in macroporous soils as a step forward from using dye patterns simply as qualitative pictures that illustrate preferential flow dye tracer experiments at different irrigation rates and initial soil moisture conditions were carried out on three hillslope sites several vertical and horizontal soil sections were prepared after each experiment to analyze the patterns of the dye tracer brilliant blue fcf photographs of the soil sections were processed by image analysis to discriminate between stained and unstained areas and to classify stained areas into three classes of dye concentration the images of the vertical sections were first analyzed according to conventional approaches e g dye coverage then a new approach was developed using the extent and distribution of the stained objects to classify flow into five types two of these flow types occur only in the soil matrix and three of them are related to the degrees of water flow between macropores and soil matrix interaction from horizontal sections the macropore distribution was classified and in combination with the dye pattern the interaction quantified based on statistical description of the spatial relationship between macropores and stained areas categorized flow type profiles showed a logical sequence in each of our experiments and we think the concepts will have broad application in soil science and infiltration research to compare the infiltration regimes of soils

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

evolution and distribution of porosity associated with subaerial exposure in upper paleozoic platform limestones west texas middle pennsylvanian lower permian limestones in the subsurface of west texas were studied to determine how subaerial exposure and freshwater diagenesis karstification affected porosity distribution in meter scale cycles approximately 87 depositional cycles are present in the gross reservoir interval depths of 2600 3000 m and each cycle is interpreted to represent a glacio eustatic sea level fluctuation using recent radiometric age dating average cycle duration is estimated at 160 000 yr per cycle reservoir grade porosity 4 occurs in 5 25 of the gross reservoir section porosity is stratified occurring in 1 6 m thick intervals in the upper part of cycles that were subaerially exposed however many cycles that were subaerially exposed now lack porosity diagenesis and porosity development have distinct patterns related to duration of subaerial exposure four stages of porosity development are identified 1 very brief or no subaerial exposure estimated at less than 5000 yr caused little or no diagenetic change 2 brief to moderate subaerial exposure estimated at 5000 50 000 yr resulted in most primary pores being filled with calcite cement and dissolution creating fine matrix pores molds and intercrystalline pores 3 moderately long subaerial exposure estimated at 50 000 130 000 yr resulted in cements filling primary pores and some fine secondary pores and dissolution creating small conduit pores vugs fractures fissures 4 prolonged subaerial exposure estimated at greater than 130 000 yr resulted in most primary and secondary matrix pores being filled with calcite cement but dissolution enlarged conduit pores vugs fractures fissures present subsurface porosity in this field preferentially occurs in thick grainstones phylloid algal boundstones and a few wackestone packstones in cycles subjected to brief subaerial exposure stages 2 and 3 matrix porosity molds intercrystalline pores is dominant because most conduit pores formed during prolonged subaerial exposure were filled with either shale during subsequent transgressions or burial cements derived from pressure solution associated with the shales the distribution of porosity in the southwest andrews area indicates that duration of subaerial exposure and supply of clastics are major factors determining ultimate porosity in limestones subjected to subaerial exposure and karstification

characteristics of a pennsylvanian ravinement surface abstract a transgressive ravinement surface is documented above the mary lee coal zone of the lower pennsylvanian pottsville formation black warrior basin northwestern alabama this ravinement surface separates an underlying non marine regression sequence from an overlying marine one and is marked by a thin ravinement bed two types of ravinement beds are identified 1 a mudstone bed with an autochthonous pelecypod and brachiopod assemblage and 2 a sandstone bed with an autochthonous zoophycos and an allochthonous trilobite crinoid brachiopod assemblage under a subcritical condition in which the shoreface angle is greater than the gradient of coastal areas gradual rise of sea level causes erosion of the existing shoreface landward and upward migration of the shoreface has two genetic consequences 1 the formation of a ravinement surface consisting of a series of erosional surfaces and 2 the deposition of ravinement beds the sediments of which are controlled by the properties of the eroded shoreline the areal distribution of the two types of the ravinement beds represents a more than 60 km retreat of the shoreline in response to a long term change of sea level the recognition of the pennsylvanian ravinement surface not only provides a correlative surface for coal bearing rocks but also documents the basinal transgressive histories not previously recognized

orbital signatures and long term vegetation patterns in the mediterranean abstract an attempt is made to explore the relation between vegetation phases and orbital configurations by comparing long pollen sequences from the mediterranean region and astronomical curves on the basis of their independent chronologies three recurring patterns emerge from this comparison i all intervals with perihelion passage occurring during northern winter were associated with significant contractions of tree populations ii all temperate stage expansions of certain mediterranean vegetation elements occurred when perihelion passage was in summer and iii temperate stage forests reached maximum extent at times of autumn perihelion of these patterns the first corresponds to extreme dry cold episodes culminating at times of march perihelion and the second to maximum summer temperature and evaporation regimes following june perihelion the third associated with the occurrence of september perihelion appears to be more diffuse both in time and space possibly reflecting local variations in hydrological regimes the consistency of at least the first two cases provides some support for the notion that certain recurring vegetation patterns appear to be a result of climate changes linked to specific orbital signatures this could eventually lead to the development of improved terrestrial chronologies through astronomical tuning

cretaceous rhythmic bedding sequences a plausible link between orbital variations and climate abstract simple oscillation cycles have been recognized in cretaceous pelagic sequences as a marked periodicity in carbonate and or organic carbon content the estimated periodicities of these cycles resemble milankovitch type variations in orbital elements however during warm geologic periods the nature of the link between orbital variations and the sedimentary record has been problematic climate model studies show that the intensity of continental margin precipitation in specific low latitude regions is a function of land sea thermal contrast which is sensitive to orbital variations cretaceous climate model simulations are characterized by regions of intense precipitation the locations of which are controlled by geographic configuration in particular in the model simulation the northern margin of the tethys ocean has all the climatic characteristics necessary to exhibit a sensitivity to orbital variations detailed studies of the biota sedimentology and geochemistry of the bedding rhythms in greenhorn cyclothem in the western interior seaway of north america are best interpreted in terms of variations in precipitation runoff and stable stratification of the seaway combined the geologic and model studies support a link between orbital periodicities variations of intense precipitation associated with specific paleogeographic situations and cretaceous bedding patterns this hypothesis has important implications for the sensitivity of the atmosphere hydrosphere lithosphere system to external forcing

cordaiteans in paleotropical wetlands an ecological re evaluation abstract cordaiteans in cordaite dominated permineralized peat from pennsylvanian coals in iowa have been reconstructed as mangroves using root anatomy peat taphonomy and geochemical data macrofloral palynofloral and conodont biostratigraphy indicate that these peats come from the latest atokan blackoak coal and earliest desmoinesian cliffland coal mid moscovian both in the kalo formation thus their depositional setting can be used to evaluate the mangrove hypothesis in recent mires thick mangrove peats have accumulated in tropical to subtropical carbonate systems in contrast thick tropical freshwater peats have accumulated in siliclastic systems kalo formation coals which we interpret as freshwater deposits formed in siliciclastic depositional settings similar to those of modern tropical freshwater peat and to other pennsylvanian coals in north america interpreted as freshwater deposits in the late atokan and earliest desmoinesian mid moscovian cordaiteans and tree ferns predominated in the western interior and illinois basins lycopsids and cordaiteans predominated in the appalachian and donets basins the scarcity of lycopsid only mires in north america during the late atokan earliest desmoinesian mid moscovian suggests drier climates than during the mid to late desmoinesian late moscovian rather than indicating mangrove swamps cordaite dominated peat may indicate climates with a low rain season although most plants in cordaite dominated peat probably grew in freshwater coastal mires in climate zones with seasons of low rain may harbor mangrove taxa the changuinola swamp of panama a modern peat accumulating wetland that has a low rain season is a possible analog of ancient cordaite dominated mires in changuinola most plants require freshwater however mangroves sustained by salt water influx into the swamp grow along the seaward edge and along blackwater creeks the low rain season hypothesis has implications for understanding rainfall amount and continuity during pennsylvanian cyclothem deposition the floral succession in diverse cordaite coals from cordaiteans to tree ferns to lycopsids suggests increasingly wet climate during coal accumulation the position of these coals immediately above the sequence boundary suggests humid climate during early glacial melting for these cyclothems

application of sequence and genetic stratigraphic concepts to carboniferous coal bearing strata an example from the black warrior basin usa carboniferous strata provide an excellent example on which to test the application of genetic stratigraphic and sequence stratigraphic concepts both approaches are employed in the evaluation of the coal bearing strata of the black warrior basin south eastern usa bounding hiatal surfaces have been recognized in the succession of rock that includes the mary lee coal zone within the framework of genetic stratigraphy one genetic sequence has been identified comprised of offlap progradational and aggradational facies and onlap aggradational and transgressive facies components seven parasequence sets have been delimited according to the concepts of sequence stratigraphy these have been ascribed to transgressive highstand and shelf margin systems tracts the identification of components of these contrasting frameworks provide the basis for evaluating other carboniferous strata

pleistocene climatic variability at astronomical frequencies abstract spectral analysis of geological records show periodicities corresponding to those calculated for the eccentricity 400 and 100 ka the obliquity 41 ka and the climatic precession 23 and 19 ka it is precisely the geological observations of this bi partition of the precessional peak confirmed to be real in astronomical computations which was one of the most impressive of all tests for the milankovitch theory concerning the question of whether or not the observed cycles account for most of the climatic variability having periods in the range predicted by the astronomical theory substantial evidence from cross spectral analysis coherency analysis and modelling is provided that at least near frequencies of variation in obliquity and precession a considerable fraction of the climate variance is driven in some way by insolation changes accompanying changes in the earth s orbit the variance components centered near a 100 ka cycle dominate most ice volume records and seem in phase with the eccentricity cycle although the exceptional strength of this cycle needs a non linear amplification by the glacial ice sheets themselves and associated feedbacks as the insolation spectra change with latitudes and with the type of parameters considered the diversity of the spectra of different climatic proxy data recorded in different places of the world over different periods is used to better understand how the climate system responds to the insolation forcing this study of the physical mechanisms involved is also achieved through the analysis of the log log shape of the geological records and through the comparison in frequency domain between simulated climatic time series and proxy data the evidence both in the frequency and in the time domain that orbital influences are felt by the climate system implies that the astronomical theory may provide a clock with which to date quaternary sediments with a precision several times greater than is now possible

organic rich radioactive marine shale a case study of a shallow water condensed section cretaceous shaftesbury formation alberta canada abstract organic rich radioactive shales are a common regional feature resting on cretaceous transgressive surfaces in western canada the basal shale in the shaftesbury formation late albian from the peace river area of northern alberta is characterized by high gamma ray high resistivity and low neutron wireline log signatures three facies in ascending order are present within the basal shaftesbury formation 1 a brackish water estuarine shale 2 a restricted marginal marine shale which is radioactive and 3 an open marine normal salinity shale the radioactive shale contains an abundance of large lenticular algal cysts cf lancettopsis lanceolata madler 1963 which are rare in overlying and underlying shale the algal cysts and high organic content may be the locus of th radioactivity the total organic carbon content 6 and sulphur content 3 4 of the radioactive shale also are higher than the shale above and below with a different mineralogy as well the radioactive portion of the basal shaftesbury shale has the characteristics of a condensed section it is directly above a ravinement surface and transgressive lag deposit which in turn locally overlie estuarine sediments deposited within an incised valley other characteristics include evidence of low oxygen values low concentrations of benthonic foraminifera and evidence of a slow sedimentation rate palynological micropaleontological and geochemical results indicate that the radioactive s ale was deposited in restricted marginal marine conditions and that overlying shale shows a progressive deepening to nearshore open marine conditions this radioactive shale does not represent the deepest water sediments of the transgression but is a condensed section deposited in relatively shallow water

geochemical relationships of late paleozoic carbon rich shales of the midcontinent usa a compendium of results advocating changeable geochemical conditions abstract previous studies have shown that pennsylvanian black shales of the midcontinent us possess a more complex geochemical history than was once thought vine and tourtelot econ geol 65 1970 253 and coveney and glascock appl geochem 4 1989 347 note that the widespread nature of metalliferous pennsylvanian black shales and the diverse geological environments across the midwestern us pose the likelihood that metals contained in the black shales are of complex origins detailed geochemical and statistical representations using characteristics of numerous black shale members have shown that water depth may not have been uniformly deep as previously inferred by numerous workers earlier suggestions that these black shales were associated exclusively with anoxic depositional conditions have been challenged by a more realistic theory of multifaceted fluctuating environmental conditions a wide range of major and trace element concentrations combined with widely varying characteristics and diverse types of organic matter indicate the presence of fluctuating geochemical settings the presumption is that numerous associated chemical reactions occurred syngenetically one geochemical index degree of pyritization dop suggests a dysaerobic to aerobic setting for many of the shales whereas some other geochemical proxies i e v v ni indicate punctuated episodes of bottom water anoxia schieber abstr programs geol soc am 33 6 2001 a102 notes that in some black shales pyrite enrichment due to intermittent organic reworking explains the high dop values once thought to equate with extreme euxinic depositional conditions it seems likely therefore that even during apparent euxinic periods as indicated by bulk geochemistry oxygen deprived events were apparently short lived the seemingly euxinic fingerprint as shown by geochemical characteristics may result through time averaging abstr programs geol soc am 33 6 2001 a102 of intermittent euxinic events providing a misleading indication of dominant euxinic conditions thus detailed microstratigraphic sampling is necessary to delineate short punctuated occurrences of intermittent sub oxic episodes the midcontinent pennsylvanian shales may reflect a complex array of bottom water oxygenation variations and water depth fluctuations in response to climatic and localized events hatch j r and leventhal j s 1992 relationship between inferred redox potential of the depositional environment and geochemistry of the upper pennsylvanian missourian stark shale member of the dennis limestone wabaunsee county kansas usa in meyers p a pratt l m nagy b eds geochemistry of metalliferous black shales chem geol 99 65 82 complicated by post depositional events appl geochem 4 1989 347 this research examines the previous exclusively anoxic origin for midcontinent pennsylvanian black shales from a geochemical perspective and offers an alternative supported by detailed statistical presentations with the hypothesis that events of anoxia were punctuated by short lived dysaerobic or even near oxic events

astronomical forcing of carboniferous paralic sedimentary cycles in the upper silesian basin czech republic serpukhovian latest mississippian new radiometric ages afford an astronomical age model for european biozonations and substages abstract the 3 km thick ostrava formation in the foreland upper silesian basin which is located along the czech polish border provides the thickest and most complete record of mixed shallow marine to continental sediments of serpukhovian carboniferous age in the former equatorial pangea the coal bearing strata of the formation show a prominent rhythmic architecture with 200 faunal bands of which approximately 80 contain marine fauna three new and three existing u pb zircon ages of intercalated volcanic tuffs measured using chemical abrasion isotope dilution thermal ionization mass spectrometry ca idtims allow for the calibration of rhythmic patterns of several orders the genetic sequences show an average duration of 100 kyr in line with orbital forcing by short eccentricity this allows the astronomical tuning of these cycles in the ostrava formation to a time axis with a resolution of 100 kyr providing temporal constraints on lithostratigraphic units floral and ammonoid biozones and west european substages the pendleian arnsbergian boundary defined at the base of the e2a ammonoid zone is now constrained to 325 9 ma and the base of the lyginopteris stangeri zone at the base of the ostrava formation to 329 2 ma the boundary of this zone with the subsequent l larischii zone corresponds to the base of the jaklovec member at 325 8 ma the correlation of the major marine bands with equivalent bands in the pennine basin england and the midland valley of scotland based on ammonoid faunas is suggested

the importance of sea level fluctuations in the formation of linear conglomerate bodies carrot creek member of cardium formation cretaceous western interior seaway alberta canada abstract the raven river member of the cardium formation turonian upper cretaceous in the carrot creek area of alberta contains two coarsening upward sequences of marine mudstones and sandstones the lower sequence coarsens from black mudstones into bioturbated fine grained sandstones and is capped by a gritty siderite horizon which probably indicates a pause in deposition the sandstones of the upper sequence contain hummocky cross stratification suggesting open marine deposition below fairweather wave base the two sequences are scoured to variable depths by a major erosion surface which has a relative relief of up to 20 m a structure map and three dimensional mesh diagrams of this surface suggest four topographic elements a relatively high terrace a bevel at which und rlying beds are truncated and a series of bumps and hollows these are interpreted to represent a remnant erosional topography which gradually fades away into the final topographic element the smooth basin plain the erosion surface is covered with conglomerate assigned to the carrot creek member of the cardium the conglomerate thickness reaches about 20 m against the bevel and in some of the hollows but usually thins to a veneer on the terrace on top of the bumps and on the distal basin floor the conglomerate bodies are relatively long and narrow and trend northwest southeast they are overlain by marine mudstones of the dismal rat member the elongate conglomerate bodies appear at first sight to be another case of western interior seaway offshore bars encased in marine mudstones many tens of kilometers seaward of time equivalent shoreline deposits however the erosion surface indicates that the conglomerates are not genetically part of the underlying coarsening upward sequence we propose a rapid relative lowering of sea level following deposition of the hummocky cross stratified sandstones the shoreline advanced many kilometers northeastward into the basin and during stillstand wave erosion cut a new shoreface profile the bevel during this lowstand incised rivers supplied gravel to the shoreface waves worked the gravel alongshore against the bevel and into the erosional hollows subsequent transgres ion spread some gravel southwestward back across the terrace storms transported gravel stringers into the transgressive muds accumulating in the hollows other erosional surfaces of this type exist in alberta at the cardium viking and bad heart horizons and in new mexico at the gallup tocito horizon suggesting that sea level changes and shoreface incision may be an alternative explanation for other long narrow offshore bars encased in marine shales

a review of the origins of metal rich pennsylvanian black shales central u s a with an inferred role for basinal brines abstract compared to most shales even most black shales numerous thin pennsylvanian marine black shales of the u s midwest are very enriched in organic c 5 40wt and heavy elements for example instrumental neutron activation analysis of 74 samples of mostly black and dark gray pennsylvanian shales of the u s midwest average 1300 ppm zn 85 ppm u 655 ppm mo 130 ppm se and 55 ppm cd amounts sufficient to raise concerns about heavy element pollution direct precipitation of sulfides and fixation by abundant organic matter during sedimentation and early diagenesis may account for heavy metals contained by shales in most cases metal supply calculations however indicate that a special source would be needed to supply metals for a strictly syngenetic origin possible sources for such metals include submarine hot springs and pennsylvanian seas that may have been more enriched in metals than modern ocean water at least at some localities additional metal values may have been added later from basinal brines e g zn or from modern groundwaters e g mo se u the actions of modern supergene processes may fix metals mitigating detrimental effects from black shales

precambrian sequence stratigraphy abstract sequence stratigraphy studies the change in depositional trends in response to the interplay of accommodation and sediment supply from the scale of individual depositional systems to entire sedimentary basin fills as accommodation is controlled by allogenic mechanisms that operate at basinal to global scales the change in depositional trends is commonly synchronized among all environments established within a basin thus providing the basis for the definition of systems tracts and the development of models of facies predictability all classical sequence stratigraphic models assume the presence of an interior seaway within the basin under analysis and are centered around the direction and types of shoreline shifts which control the timing of all systems tracts and sequence stratigraphic surfaces in overfilled basins dominated by nonmarine sedimentation the definition of systems tracts is based on changes in fluvial accommodation as inferred from the shifting balance between the various fluvial architectural elements the method of sequence stratigraphy requires the application of the same set of core principles irrespective of the age of strata under analysis from precambrian to phanerozoic the study of precambrian basins is often hampered by poorer stratal preservation and by a general lack of time control however where sedimentary facies are well preserved the lack of time control may be partially compensated by a good knowledge of facies architecture and relationships as well as by paleocurrent data the latter are particularly important to understand the stratigraphic record of tectonically active basins where abrupt shifts in paleoflow directions allow one to infer tectonic events and map the corresponding sequence bounding unconformities arguably the most important contribution of precambrian research to sequence stratigraphy is the better understanding of the mechanisms controlling stratigraphic cyclicity in the rock record and hence of the criteria that should be employed in a system of sequence stratigraphic hierarchy there is increasing evidence that the tectonic regimes which controlled the formation and evolution of sedimentary basins in the more distant geological past were much more erratic in terms of origin and rates than formerly inferred solely from the study of the phanerozoic record in this context time is largely irrelevant as a parameter in the classification of stratigraphic sequences and it is rather the stratigraphic record of changes in the tectonic setting that provides the key criteria for the basic subdivision of the rock record into basin fill successions separated by first order sequence boundaries these first order basin fill successions are in turn subdivided into second and lower order sequences that result from shifts in the balance between accommodation and sedimentation at various scales of observation irrespective of the time span between two same order consecutive events sequences identified in any particular basin are not expected to correlate to other first and lower order sequences of other basins that may be similar in age but may have different timing and duration

the magnitude of late paleozoic glacioeustatic fluctuations a synthesis a comprehensive literature review shows that the magnitude of eustatic fluctuations varied throughout the carboniferous and permian and that at least eight distinct phases can be recognized facies juxtapositions in carbonate successions and erosional relief in clastic successions indicate that glacioeustatic fluctuations of 20 25 m and occasionally as much as 60 m took place throughout the early mississippian tournaisian a widely recognized glacial period middle mississippian mid chadian through holkerian shallow marine carbonate and clastic successions indicate that eustatic fluctuations were 10 25 m a decrease that matches well with the paucity of coeval glacial deposits late visean asbian through mid brigantian glacioeustatic fluctuations of 10 50 m record the initial phases of ice accumulation in advance of the widespread mid carboniferous glacial event the latest mississippian earliest pennsylvanian mid brigantian through langsettian was a time of widespread glaciation and strata of this age commonly exhibit evidence of glacioeustatic fluctuations of as much as 40 100 m although middle pennsylvanian duckmantian through asturian glacial deposits are present in eastern australia paleovalley depths suggest that coeval glacioeustatic fluctuations were less than 40 m glacioeustatic fluctuations of as much as 100 120 m have been widely reported from late pennsylvanian earliest permian stephanian through mid sakmarian successions in north america an increase that corresponds to the growth of large ice sheets across much of gondwana and the accumulation of ice in the northern hemisphere incision and facies juxtaposition in early middle permian mid sakmarian through kungurian successions in eastern australia indicate that glacioeustatic fluctuations of 30 70 m occurred during the waning stages of major glaciation erosional relief in paleoequatorial carbonates and the presence of coeval glacial deposits in australia suggests that eustatic fluctuations of 10 60 m occurred during the final stages of glaciation in the middle to late permian roadian through capitanian but the modest size of most of these fluctuations makes it difficult to isolate the glacioeustatic signature this review demonstrates that far field cyclic successions record changing glacial conditions in gondwana that the magnitude of glacioeustatic fluctuations was directly related to the volume of glacial ice that carboniferous permian glacioeustasy was more variable than previously recognized and that generalizations from short temporal intervals are probably not representative of the late paleozoic ice age as a whole although any attempt to quantify the magnitude of ancient eustatic changes is based on caveats and assumptions this review incorporates the results of over 100 published papers on the topic in an attempt to minimize the errors inherent in any one study

long term variations of monthly insolation as related to climatic changes qualitative multivariate models which combine past insolations of selected months at selected latitudes explains 55 to 67 of the variance in the 135 millenia long oxygen isotope record of pleistocene climates

relationship between inferred redox potential of the depositional environment and geochemistry of the upper pennsylvanian missourian stark shale member of the dennis limestone wabaunsee county kansas u s a analyses of 21 samples collected from a core of the 52 8 cm thick stark shale member of the dennis limestone in wabaunsee county kansas demonstrate four cycles with two orders of magnitude variations in contents of cd mo p v and zn and order of magnitude variations in contents of organic carbon cr ni se and u the observed variability in amounts and or ratios of many metals and amounts and compositions of the organic matter appear related to the cause and degree of water column stratification and the resulting absence presence of dissolved o2 or h2s high cd mo u v zn and s contents a high degree of pyritization dop 0 75 0 88 and high high v v ni 0 84 0 89 indicate the presence of h2s in a strongly stratified water column intermediate contents of metals and s intermediate dop 0 67 0 75 and intermediate v v ni 054 0 82 indicate a less strongly stratified anoxic water column whereas low metal contents and low v v ni 0 46 0 60 indicate a weakly stratified dysoxic water column high p contents at the top of the organic matter rich intervals within the stark shale member indicate that phosphate precipitation was enhanced near the boundary between anoxic and dysoxic water compositions relatively abundant terrestrial organic matter in intervals deposited from the more strongly stratified h2s bearing water column indicates a combined halocline thermocline with the fresher near surface water the transport mode for the terrestrial organic matter the predominance of algal organic matter in intervals deposited from a less strongly stratified water column indicates the absence of the halocline and the presence of the more generally established thermocline relatively low amounts of degraded hydrogen poor organic matter characterize intervals deposited in a weakly stratified dysoxic water column the inferred variability in chemistry of the depositional environments may be related to climate variations and or minor changes in sea level during the general phase of deeper water deposition responsible for this widespread shale member

the stratigraphic and geochemical imprints of late ordovician glaciation on far field neritic carbonates anticosti island eastern canada abstract the storm dominated open marine neritic carbonate facies continuously exposed in coastal cliffs and wide rocky tidal flat exposures at the western end of anticosti island form a 315 m thick expanded section spanning the ordovician silurian boundary these carbonate facies display deepening shallowing trends of different orders resulting in a hierarchical stacking of sedimentary cycles the carbonate facies within these multi order cycles represent sediments that were deposited from shoreline to deeper outer carbonate ramp 80 m in water depth and exhibit sea level changes of several tens of metres in magnitude field petrographic and geochemical evidence support a well preserved primary 18o signal in close equilibrium with the original paleoenvironmental conditions the 18o intracycle variations up to 1 0 in magnitude reveal repeated decreasing and increasing values during the transgressive and regressive portions of decametre tr cycles respectively although temperature salinity and ice volume influenced the recorded primary 18o signal orbital scale glacioeustasy ultimately controlled facies and cycle development and 18o signal during the katian immediately before the latest ordovician hirnantian glaciation the 3 5 myr long 18o signal recorded by our entire succession supports a protracted period of cooling leading into the main phase of latest ordovician hirnantian glaciation spectral analysis of the 18o record also reveals decametre variations which are associated with decametre scale transgressive regressive tr cycles possibly reflecting eccentricity orbital signals our study shows the importance of a thick expanded stratigraphic succession sampled at the highest resolution possible to decipher potential linkages between facies changes multi order stratigraphic cycles 18o signal and the earth s orbital parameters