sedimentology and stratigraphy of thetownsend tuff bed lower old red sandstone in south wales and the welsh borders the townsend tuff bed has a highly distinctive internal stratigraphy which allows it to be recognized at a large number of localities scattered over the welsh borders and south wales it is a group of 3 almost directly superimposed normally graded air fall tuffs that originated in distant but powerful plinian eruptions centre unknown and became spread over extensive but practically featureless coastal mud flats the bed occurs in a barren interval within the early lower old red sandstone between a silurian invertebrate vertebrate fauna below and an already devonian vertebrate assemblage above the base of the devonian system in south wales and the welsh borders is accordingly defined as occurring at a regionally uniform lithological contact within the townsend tuff bed

base level buffers and buttresses a model for upstream versus downstream control on fluvial geometry and architecture within sequences abstract the effects of downstream base level control on fluvial architecture and geometry are well explored in several broadly similar sequence stratigraphic models cretaceous dakota group strata u s western interior have characteristics reflecting combined downstream and upstream base level controls that these models cannot address particularly three layers of amalgamated channel belt sandstone within this group thicken and are continuous for distances 300 km along dip that stretch the reasonable lengths for which these models are intended to apply as well architecture in up dip reaches records repeated valley scale cut and fill cycles this contrasts with equivalent strata down dip which record channel scale lateral migration with no such valley scale cycles apparent we here introduce the concept of buffers and buttresses to address these observations we assume that river longitudinal profiles are each anchored down dip to some physical barrier e g the sea strand etc that we refer to as a buttress buttress shift is considered the primary downstream control on base level profiles extrapolated up dip from the buttress over any modeled duration of buttress shift can range widely because of high frequency variability in upstream base level controls e g discharge etc all these potential profiles however are bounded above by the profile of highest possible aggradation and below by the profile of maximum possible incision these upper and lower profiles are buffers and they envelop the available fluvial preservation space thickness of the buffer zone is determined by variability in upstream controls and should increase up dip to the limit of downstream profile dominance dakota valley scale surfaces record repeated cut and fill cycles driven by up dip controls and are confined between thick stable buffers equivalent strata down dip record lateral reworking within a thinner channel scale buffer zone that was positioned by downstream controls regression exposed slopes similar to the buffer zone thus buffers were stable for long distances and durations this prompted dip extensive lateral reworking of strata into upstream valley scale and downstream channel scale sheets buffers and buttresses provide a broadly applicable model for fluvial preservation that captures upstream vs downstream base level controls on geometry and architecture the model lends general insights into dip oriented variations in fluvial architecture production of sheet vs lens geometry total preservation volumes for fluvial systems and variations in these factors related to contrasting climatic conditions and basin physiography the model can be amended to existing sequence stratigraphic approaches in order to capture dip oriented variations in sequence architecture

large scale alluvial architecture and correlation in a triassic pebbly braided river system lower wolfville formation fundy basin nova scotia canada abstract determining what the controls are on the large scale 10 km horizontal architecture of coarse grained fluvial deposits is important for understanding subsurface fluid distribution and extraction from these important aquifers and hydrocarbon reservoirs this contribution describes the architecture of coarse grained fluvial sediments from an almost continuous lateral profile 27 km long by 115 m high in the upper triassic wolfville formation fundy basin nova scotia the lateral extent and quality of exposure allows development of a high resolution correlation scheme and definition of architectural elements the lower wolfville formation lithofacies composed of breccias conglomerates sandstones mudstones and paleosols comprises alluvial fan fluvial and ephemeral lake margin facies associations alluvial fan deposits form 15 of the studied section and are developed locally between the overlying fluvial facies and the unconformity with carboniferous strata where they infill remnant topography the succession is dominated 80 by pebbly sandstones deposited as part of a gravelly braided fluvial system and ends abruptly with a thin ephemeral lake margin facies association 5 the large scale architecture and sedimentology of the pebbly sandstone succession is documented with particular attention focussed on bounding surfaces and stacking patterns in the fluvial facies association two scales of development of erosion surface and cycles can be recognized the s surfaces can be correlated across the profile 27 km and show evidence of up to 10 m of erosion a significant facies or grain size change onlap and association with mature calcic paleosols the e surfaces can be correlated between 5 and 17 km display erosion of the regional extent of the e and s surfaces indicate that the gravelly fluvial system has a large scale sheet like geometry which comprises a series of stacked erosion dominated multi story bodies high resolution architectural elements are poorly defined in this coarse fluvial system and make it difficult to constrain the scale of the depositional system an individual high resolution cycle records braid plain development and is interpreted as a multi story channel belt the braid plain width is estimated at 19 km but the width of individual active channels is unknown the sediments were deposited in a proximal fluvial setting disconnected from marine influences we interpret the high resolution cycles and bounding e surfaces to record a progressive decrease in runoff and fluvial transport capacity indicative of a drying upward climatically driven signal the origin of the s surface bounded packages is more difficult to determine a variety of mechanisms are considered including changes in discharge driven by climatic fluctuations changes in stream power related to drainage capture within the source area and tectonic tilting an important aspect of the study is that the s surfaces can be identified and correlated for 27 km and provide an example of a robust high resolution correlation framework in coarse grained braided fluvial deposits that could be applied elsewhere in contrast the e surfaces do not display any significant changes in facies or grain size across them such that many of the smaller scale cycles could potentially be miscorrelated

tectonic evolution of sw wales during the upper palaeozoic during the upper palaeozoic the development of several strike faults strongly influenced the deformation history of sw wales this aspect of the deformation is emphasized in this new description of the tectonic evolution of the region after the caledonian orogeny several strike faults caused crustal extension by normal dip slip and partially controlled the subsidence of depositional basins these faults ceased moving before the initiation of variscan deformation in sw wales two of the earlier faults were reactivated with reverse slip translations during variscan deformation when three strike faults were initiated as a result of gravitational spreading two of the new faults formed sole thrusts for northward translating nappes and the other developed as a subsidiary lag fault the sole thrusts transected some of the pre existing faults causing along strike variation in their motion the strike faults in sw wales were therefore initiated at different times and display contrasting displacement histories

anatomy of extremely thin marine sequences landward of a passive margin hinge zone neogene calvert cliffs succession maryland u s a abstract detailed examination of neogene strata in cliffs 25 35 m high along the western shore of chesapeake bay maryland reveals the complexity of the surviving record of siliciclastic sequences 150 km inland of the structural hinge zone of the atlantic passive margin previous study of the lower to middle miocene calvert plum point member and choptank formations documented a series of third order sequences 7 10 m thick in which lowstand deposits are entirely lacking transgressive tracts comprise a mosaic of condensed bioclastic facies and regressive highstand tracts are present but partially truncated by the next sequence boundary smaller scale fourth order cyclic units could not be resolved together these sequences constitute t e transgressive and early highstand tracts of a larger second order miocene composite sequence the present paper documents stratigraphic relations higher in the calvert cliffs succession including the upper miocene st marys formation which represents late highstand marine deposits of the miocene second order sequence and younger neogene fluvial and tidal inlet deposits representing incised valley deposits of the succeeding second order cycle the st marys formation consists of a series of tabular units 2 5 m thick each with an exclusively transgressive array of facies and bounded by stranding surfaces of abrupt shallowing these units which are opposite to the flooding surface bounded regressive facies arrays of model parasequences are best characterized as shaved sequences in which only the transgressive tract survives and are stacked into larger transgressive highstand and forced regression sets biostratigraphic analyses by others indicate that this onshore record contains the same number of third order 1 my duration units as present offshore and so thinning landward of the hinge zone was accomplished not by omission or erosion of entire cycles of deposition but instead by omission of some subsidiary elements e g lowstand tracts by erosional shaving of sequence tops removing the entire regressive tract in some sequences by a reduced number of component high order cycles surviving per larger set and by qualitative changes in the anatomy or composition of elements e g condensed transgressive tracts shaved sequences rather than parasequences all of these differences can be attributed to limited accommodation ut preservation of an onshore record of each baselevel cycle was probably also favored by the large amplitude and rapidity of eustatic fluctuations during the miocene

structure and composition of calcified roots and their identification in calcareous soils abstract fine white branching structures isolated from calcareous soils in southern france were shown by microscopy and by chemical and mineralogical analysis to be calcified roots these structures occur mainly in rendzinas calcic xerosols and cambisols that are dense or rich in fines and where drainage is slow visible to the naked eye they can locally represent up to a quarter of the soil mass calcified roots consist of calcite elements whose mean size varies from 60 to 80 m and which retain the structure of the original cells of the root cortex each calcified cell has a central nucleus composed of two crystals on average and is coated with a thin mineral layer that seems to be poorly crystallized some retain organic remnants and the structure of cell walls calcified cells contain tubes less than 1 m in diameter which appear to have formed by weathering although they have generally not been recognized as calcified roots similar microstructures have been indicated in some calcareous soils and calcretes both present day and ancient ones that suggests that calcified roots are widespread and that their occurrence contributes to the genesis of some calcareous soils

upper cretaceous sequences and sea level history new jersey coastal plain we developed a late cretaceous sea level estimate from upper cretaceous sequences at bass river and ancora new jersey odp ocean drilling program leg 174ax we dated 11 14 sequences by integrating sr isotope and biostratigraphy age resolution 0 5 m y and then estimated paleoenvironmental changes within the sequences from lithofacies and biofacies analyses sequences generally shallow up section from middle neritic to inner neritic paleodepths as shown by the transition from thin basal glauconite shelf sands transgressive systems tracts tst to medial prodelta silty clays highstand systems tracts hst and finally to upper delta front quartz sands hst sea level estimates obtained by backstripping accounting for paleodepth variations sediment loading compaction and basin subsidence indicate that large 25 m and rapid 1 m y sea level variations occurred during the late cretaceous greenhouse world the fact that the timing of upper cretaceous sequence boundaries in new jersey is similar to the sea level lowering records of exxon production research company epr northwest european sections and russian platform outcrops points to a global cause because backstripping seismicity seismic stratigraphic data and sediment distribution patterns all indicate minimal tectonic effects on the new jersey coastal plain we interpret that we have isolated a eustatic signature the only known mechanism that can explain such global changes glacio eustasy is consistent with foraminiferal 18 o data either continental ice sheets paced sea level changes during the late cretaceous or our understanding of causal mechanisms for global sea level change is fundamentally flawed comparison of our eustatic history with published ice sheet models and milankovitch predictions suggests that small 5 10 10 6 km 3 ephemeral and areally restricted antarctic ice sheets paced the late cretaceous global sea level change new jersey and russian eustatic estimates are typically one half of the epr amplitudes though this difference varies through time yielding markedly different eustatic curves we conclude that new jersey provides the best available estimate for late cretaceous sea level variations

carbon isotopic evidence for organic matter oxidation in soils of the old red sandstone silurian to devonian south wales uk petrographic and calcrete carbon isotope data from seasonally waterlogged upper silurian p idoli to lower devonian pragian palaeo vertisols of the old red sandstone south wales uk are presented the 13 c values mostly range from 9 to 12 vpdb suggesting that the soils were inhabited by abundant vegetation that when oxidized perhaps with microbial assistance resulted in co 2 rich soils such soils would favour calcrete precipitation through equilibration of soil zone co 2 with the relatively lower atmospheric p co 2 however reliably estimating palaeoatmospheric p co 2 using these carbon isotope data is a challenge supplementary material detailed information on stable isotope measurement methods descriptions of the samples and carbon and oxygen isotope data are available at www geolsoc org uk sup18754

estuarine deposits of the albian paddy member peace river formation and lowermost shaftesbury formation alberta canada abstract outcrop exposures of the peace river formation in northwestern alberta contain evidence of significant relative sea level fluctuations that occurred during the middle to late albian these include paddy member channels that incised into the cadotte member shoreline deposits and the subsequent estuarine frill the upper cadotte member contact is irregular and siderite cemented it has been scoured into and infilled by sandstone of the paddy member the lower sandstone of the paddy member is crossbedded with abundant comminuted carbonaceous debris channels cut into the cadotte member are up to 5 m deep and are locally overlain by in situ coal and roots the channels are infilled with alternating couplets of moderately to intensely bioturbated sand and mud which form inclined h terolithic stratification mud plugs are also present internally these sands are ripple and parallel cross laminated this part of the paddy member is interpreted as estuarine fill that resulted from a relative sea level rise the channel fill is overlain by intensely bioturbated locally rooted finely interbedded sandstone siltstone and shale with minor reworked bentonites interpreted as tidal flat deposits tidal flat sediments are overlain by 2 to 3 m of scoured parallel laminated sandstone and capped by 1 5 m of planar tabular crossbedded sandstone interpreted as shoreface and transgressive estuary mouth deposits respectively evidence for tides throughout the paddy member includes inclined heterolithic stratification mud couplets reactivation surfaces reversing paleoflows and compound crossbeds the incised channels and related fill are correlative with a sequence of paleosols 300 km southwest in the boulder creek formation a brackish influence is indicated by the presence of a few species of peridinioid dinoflagellates occurring in abundance at certain levels and the trace fossil assemblage the paddy member is overlain by marine mudstone of the shaftesbury formation a 20 to 30 cm thick wave rippled layer of fish teeth fish bones and pebbles near the base of the shaftesbury formation can be traced along the peace river for at least 75 km the layer of fish remains is interpreted as transgressive lag

recrystallization of holocene calcareous root tubes in the tengger desert northwest china and its effects on the reliability of paleoenvironmental reconstruction results abstract reconstructing paleoenvironmental conditions using geochemical proxies from pedogenic carbonate must ensure that the pedogenic carbonate is not recrystallized calcareous root tubes crts formed by carbonate precipitation along the roots have been widely used for paleoenvironmental reconstruction in arid and semi arid regions however whether further recrystallization occurs after crt formation and its impact on the reliability of paleoenvironmental reconstruction remains uncertain in this study 52 holocene age crt samples obtained from 17 sites in the tengger desert of northwestern china were described using cathodoluminescence and optical microscopy to clarify this uncertainty the crt outer detrital layer is composed of detrital material and carbonate while the inner precipitated carbonate layer is composed only of carbonate the results of this study showed that recrystallized carbonates occurred in the detrital layers of 45 of the samples 87 but no recrystallization was observed in the precipitated carbonate layer in any of the crt samples crt recrystallization is caused by the introduction of calcium bearing meteoric waters after crt formation these crt recrystallization characteristics not only occurred in the tengger desert but also in other regions with seasonal soil moisture deficits this study showed that carbonate from the crt detrital layer is not a suitable material for 14c dating and 13c and 18o analyses however carbonate from the precipitated carbonate layer could be a suitable material for these analyses moreover paleoenvironmental reconstruction results derived from changes in the sr ca and mg ca ratios of crts should not be affected by recrystallization

evolution of chernozems in the northern caucasus russia during the second half of the holocene carbonate status of paleosols as a tool for paleoenvironmental reconstruction abstract a chronosequence of chernozems buried under kurgans funeral mounds dated archaeologically to 5000 3800 4000 and 1600 1700 years bp as well as the modern surface chernozems were studied to reconstruct environmental change in the central northern caucasus in the second half of the holocene special emphasis was made on the detailed morphological and analytical characteristics of pedogenic carbonates and microscopic investigation of phytoliths in the paleosols buried 5000 years bp carbonates represented by compact micritic pedofeatures are in the uppermost part of the solum neoformed gypsum is found below this differs from the features of the modern soils and the paleosols buried 1600 1700 years bp in which the upper part of the profile is leached pedogenic carbonates occur mostly in the form of diffuse pseudomycelium impregnations and fine films whereas gypsum is absent the comparison of morphological features of the paleosols and the modern soils confirms the general tendency of paleoenvironment evolution from warm and dry in the atlantic period to cooler and more humid in the late subboreal and subatlantic periods the compaction of soil mass and tonguing of humus horizon together with some dissolution of carbonate pedofeatures and signs of high biological activity in the paleosols buried 3800 4000 years bp are thought to indicate contrasting seasonal and annual variations of precipitation in early subboreal period presence of calcified root cells of perfect habit in the paleosols of this chronointerval is also interpreted as evidence of contrasting seasonal climate hard carbonate nodules were found in all chernozems of the chronosequence the size of nodules their internal porosity and recrystallization phenomena increase with age we assume nodules to be relict pedofeatures in the subatlantic paleosols and modern soils which were transformed but not completely destroyed during the late holocene humidification and enhancement of leaching thus a multiphase model of carbonate pedofeatures formation is dominant in the soils studied phytolith assemblages indicate meadow steppe vegetation in the atlantic period later in the subboreal and subatlantic periods forest vegetation appears meadow with some steppe elements associations also determined in the late holocene profiles probably reflect anthropogenic deforestation these results are in good agreement with the interpretation of paleosol s properties we conclude that complex characteristic of pedogenic carbonates which we define with the term carbonate status is one of the most valuable sources of the paleogeographical information in the chronosequences of steppe and forest steppe soils

different paleoenvironments of late pleistocene age identified in verőce outcrop hungary preliminary results abstract complex geomorphological geological paleopedological and chronometrical investigations were started to reveal the development of the alluvial section and the loess paleosol sequence containing remnants of a late palaeolithic site near ver ce hungary different paleoenvironments were identified in the profiles of the abandoned brickyard influenced by different facies in the margin of fluvial alluvial palaeo danube and proluvial southeast pediment of borzsony mountain area and the environments affected by the climate fluctuation of late pleistocene loess paleosol sequence overlying the base of alluvial materials sediments possibly deposited by palaeo danube were identified in a basal section of the abandoned brickyard the alluvial facies was indicated by sand silt and clay layers in the sediment sequence some parts of the alluvial sediments were covered by loess in the glacial periods intercalated by four paleosol horizons formed during interglacial or interstadial periods the sedimentation of loess and the forming of paleosols were finished by pedimentation processes sheet wash redeposition indicated by the fine layered material at the top of each paleosol horizon another complex fluvial alluvial section was identified at a different part of the brickyard possibly developed synchronous with the loess paleosol sequence during the late pleistocene based on relative and chronometrical dating methods e g archaeological stratigraphy and correlation of the artifacts 14c and luminescence dating the development of the loess paleosol sequence started in marine isotope stage 6 mis6 and the youngest layer dated to mis2

the use of microcodium to identify a paraconformity an example from the paleogene sequence of malatya basin eastern turkey abstract the eocene oligocene boundary in eastern turkey has generally been considered conformable with no break in sedimentation to the west of malatya in eastern turkey however the eocene oligocene boundary is located between the asartepe member of the darende formation eocene and the overlying muratli formation rupellian early chattian analysis of the strata below the boundary shows that fossil evidence of the priabonian stage is missing and that the sediments just below the boundary contain numerous microcodium although the precise origin of microcodium is open to debate it is generally agreed that they formed as a result of calcification of roots of terrestrial plants the morphologically diverse array of microcodium types 1 2 and 3 that are up to 1660 m in diameter found in the asartepe member provides clear evidence that terrestrial plants were established before the sediments in the overlying muratli formation were deposited this study demonstrates that the presence of microcodium can highlight the presence of a paraconformity in an otherwise conformable succession of shallow water sediments

sediment recycling on siluro devonian floodplains some of the red mudstones in the red mark old red sandstone of llansteffan dyfed are interpreted as originating as sand sized mud aggregates pellets produced in soils and deposited from bed load in small sinuous channels by analogy with the channel country of australia such channels may represent periods of low discharge and reduced hydraulic efficiency when the floodplains were locally reworked in contrast larger channel fills with extraneous sediments may represent pluvial periods with increased discharge

biogenic β fabric features in the hard laminated crusts of the mersin and adana regions southern turkey and the role of soil organisms in the formation of the calcrete profiles abstract this paper describes fabric features and their distribution in the calcretes and emphasizes the role of soil organisms in the formation of the calcrete profiles quaternary calcretes are common in the mersin and adana provinces occurring as powdery nodular tubular fracture infill and various forms of crusts the stable isotope values indicate calcrete development under semi arid climatic conditions and a pedogenic origin biogenic or fabric constituents are abundant in the hard laminated crust these are the rhizoliths alveolar septal structures needle fiber calcites calcified filaments spherical calcite bodies microcodium and vadose calcrete pisoliths rhizoliths have mainly formed by the petrification of roots and often contain cellular cortex structures the alveolar septal structure comprises root voids separated by a micritic wall or a bundle of tangentially oriented calcite needles needle fiber calcite is common in the hard laminated crust as monocrystalline rods and polycrystalline needles monocrystalline rods are smooth and small

marine and nonmarine deposition in a long term low accommodation setting an example from the middle pleistocene qm2 unit eastern central italy abstract facies anatomy and large scale stratigraphic organization of mid pleistocene strata qm2 unit exposed near the town of ortona eastern central italy have been defined through an integrated outcrop and subsurface dataset and record sedimentation within a long term low accommodation setting the studied interval can be subdivided into nine facies associations reflecting a range of continental marginal marine nearshore and innermost shelf environments and contains a well preserved record of high frequency relative sea level changes in the form of a stack of three unconformity bounded sequences each of the three sequences designated qm23 qm22 and qm21 from oldest to youngest consists of a specific subset of the nine identified facies associations as a function of preserved depositional systems and systems tracts typically the following architectural elements occur in ascending stratigraphic order i a basal unconformity molded by fluvial incision and subaerial exposure during sea level fall and shoreface erosion during subsequent rise ii a maximum regressive surface which is coincident with the sequence boundary iii a transgressive systems tract including braided river conglomerates and floodplain fines within the confines of an incised valley palustrine carbonates and back barrier lagoon mudstones and a deepening and fining upward shoreface to offshore transition facies succession bounded at the base by a wave ravinement surface iv a sharp regressive surface of marine erosion produced by shoreface incision during relative sea level fall and v a prograding downstepping and offlapping sharp based lithofacies assemblage of either beach conglomerates or sandstones ascribed to the falling stage systems tract overlain by a rooted paleosol marking subaerial exposure sequences were deposited on the uplifting palaeo adriatic shelf in response to repeated high frequency and high amplitude eustatic changes in sea level that would promote the creation of accommodation space by subtracting space to deposition the contemporaneous regional uplift of the basin margin may be accounted for the shingled downstepping configuration of individual sequences to form a falling stage sequence set of a larger composite sequence in dip view the erosional contact at the base of the qm2 falling stage sequence set is a composite regressive surface resulting from the downdip convergence and amalgamation of multiple erosional surfaces produced by the progressive basinward translation of successive sequences results from this study have direct implications for the oil and gas field development and exploration when making predictions of reservoir and seal geometries within shallow marine marginal marine and nonmarine sediments emplaced in similar long term limited accommodation settings

carbonate rhizoliths in loess and their implications for paleoenvironmental reconstruction revealed by isotopic composition δ13c 14c abstract loess paleosol sequences are important terrestrial archives for studying quaternary climate changes they often contain secondary carbonates including e g rhizoliths calcified roots these secondary carbonates are precipitated in isotopic equilibrium with root derived co2 and are therefore used to reconstruct the vegetation present during their formation based on stable carbon isotopic composition 13c usually the chronological context of secondary carbonates in general is not mentioned because it is assumed that they are formed synsedimentary with loess deposition the loess paleosol sequence at nussloch sw germany contains in its youngest part upper wurmian large carbonate rhizoliths with diameters of up to 5 cm and lengths of up to 1 m and more which have not been described in this profile so far we investigated rhizoliths as well as loess adjacent to and distant from rhizoliths for carbonatic carbon ccarb and organic carbon corg contents as well as their isotopic composition 13c radiocarbon dating to identify the rhizolith origin and the time frame of their formation considering the 13c fractionation by carbonate precipitation the 13ccarb values 10 9 0 1 revealed c3 plant origin of the rhizolith carbonate and the absence of large amounts of occluded primary loess carbonate similar 14c ages of rhizolith ccarb and corg 3788 59 years bp and 3150 59 years bp respectively argued for the absence of postsegregational alteration therefore they are suitable for the reconstruction of paleoenvironmental conditions after loess sedimentation the 14c ages clearly indicate that rhizoliths did not form synsedimentary roots penetrated the loess at nussloch after the deposition had ceased at 15 ka bp even in the loess adjacent to the rhizoliths up to a distance of 5 cm 13ccarb values indicate the presence of secondary carbonate deriving from postsedimentary organic matter of origin other than that of the reference loess material hence this postsedimentary input of younger root biomass might have masked the initial plant signal in loess paleosol sequences which could cause uncertainties for paleoenvironmental reconstructions based solely on loess organic matter

structural controls on palaeozoic basin evolution and inversion in southwest wales the tectonic evolution of sw dyfed is presented in terms of a model of basin evolution and subsequent destruction by reactivation of the basin bounding faults in contractional mode movements along long lived palaeozoic extensional faults were reversed during variscan compression with the pre existing faults accommodating the contraction in addition to the development of a thin skinned thrust and fold system basin analysis of the pre variscan extensional system uses sedimentological and stratigraphical evidence to constrain the timing of movements of the basin bounding faults thus allowing division of the stratigraphy into depositional megasequences related to these extensional movements field examples on all scales illustrate active extension during the palaeozoic structural cross sections through sw dyfed demonstrate the interrelationship of the extensional and contractional deformations with palinspastic restorations of the cross sections illustrating the complexity of the pre variscan template

petrography and geochemistry of floodplain limestones from the clarks fork basin wyoming u s a carbonate deposition and fossil accumulation on a paleocene eocene floodplain abstract floodplain limestones are increasingly important sources of fossil vertebrates from the clarks fork basin the northern extension of wyoming s bighorn basin despite their importance for understanding paleogene floodplain faunas little work has addressed the depositional history of these carbonates or evaluated potential taphonomic biases affecting the assemblages they produce recent studies of bighorn basin paleosols have increased our understanding of parameters affecting the paleo floodplain and large collections of limestones now exist this has allowed detailed investigation of limestone petrography and geochemistry and the proposal of a new model for their formation floodplain limestones record a complex depositional and diagenetic history precipitation of micritic low mg calcite and accumulation of bone occurred in low energy ponded water at the earth s surface pedogenic overprinting obscured primary textures and produced diagenetic grainstones packstones and wackestones biological and chemical pedogenic processes formed most carbonate allochems including micrite grains and calcified plant cells microbial fermentation occurred at shallow burial depths and methane production migration and oxidation affected the carbon isotope composition of diagenetic carbonate and primary micrite pore space was fully occluded by phreatic calcite cements during late stage diagenesis fossil assemblages contained within the limestones likely represent fauna derived from rarely sampled floodplain microenvironments hydraulic transport of bones was minimal accumulation of fossil material occurred episodically and bones were rapidly encased in micrite the uncommon body size distribution characteristic of limestone faunas is attributed in part to buffering of chemical and physical processes normally effecting bone decomposition during surface exposure and pedogenesis

iron iii reduction in a low organic carbon brackish marine system abstract siderite rhizocretions are generally considered to be an indicator of fresh water conditions the presence of siderite rhizocretions with a marine 18o isotope signature in the rutland formation ketton u k seems to contradict this belief commonly in marine settings pyrite is more prevalent than siderite because of the high concentrations of sulfate in seawater the rutland formation is a fine grained mixed carbonate clastic succession with interbedded coals that was deposited in marginal marine conditions analysis of siderite revealed that it was chemically zoned predated pyrite and has an average 18o signature of 0 44 this siderite is interpreted as having precipitated during early diagenesis from brackish to marine porewaters containing low concentrations of bioavailable organic matter despite the porewaters being dominantly marine under conditions of restricted organic matter quality and or quantity fe iii reducing bacteria can outcompete sulfate reducing bacteria for the organic substrate resulting in the precipitation of siderite at the expense of pyrite

a classification of rhizogenic root formed calcretes with examples from the upper jurassic lower cretaceous of spain and upper cretaceous of southern france reply abstract studies of fluvial sequences from the upper jurassic and lower cretaceous of the cameros basin spain and the upper cretaceous of the aquitaine basin france have revealed large numbers of calcrete profiles which have formed wholly or largely through the action of plant root calcification those from spain have formed by the calcification of root mats whereas those from france resulted from the accumulation of calcified root cells microcodium these root related rhizogenic calcretes developed in stages allowing developmental time series chronosequences to be identified contrasting with existing models for calcrete profile growth they provide unique examples where vegetation has been the dominant control on profile development and probably indicate specific vegetation types and palaeoecological settings the role of root activity in forming some quaternary calcretes is also discussed

late silurian and early devonian terrestrialisation ichnological insights from the lower old red sandstone of the anglo welsh basin u k abstract late silurian to early devonian deposits from the lower old red sandstone anglo welsh basin preserve a diverse assemblage of trace fossils that collectively comprise an important record of early terrestrialisation five main palaeoenvironmental categories are represented 1 perennial rivers 2 ephemeral rivers 3 floodplain lakes 4 alluvial fan and 5 marginal marine ichnocoenoses mainly reflect the activity of aquatic and or semi aquatic animals fluvial deposits preserve evidence for colonisation by eurypterids fish and myriapods ephemeral river channel margins splays preserve the most diverse ichnofauna composed of deposit feeders burrows and trackways produced by arthropods feeding and foraging in channel margin soft grounds that were colonised after fluvial flood events high densities of deposit feeding structures may indicate of explosive population growth in response to periodic acyclical replenishment of nutrients in these aquatic settings ichnotaxa common to both perennial and ephemeral fluvial environments suggest that there might have been only one aquatic ecosystem the degree to which the channel margin ichnofaunas record a truly subaerial terrestrial arthropod signature is difficult to ascertain and most trace makers were probably semi aquatic some terrestrial animals invaded channel margin areas to feed and were also capable of inhabiting high energy alluvial fan environments however the fans contain low diversity ichnological assemblages and were likely to have been inhabited by an opportunistic fauna possibly the only truly subaerial terrestrial ichnocoenosis is that of pedogenically modified mudrock with scoyenia which represents an early soil ichnofauna the majority of ichnocoenoses described from continental palaeoenvironments could be classified under the scoyenia ichnofacies marginal marine deposits contain an impoverished skolithos cruziana ichnofacies typical of silurian devonian brackish water assemblages

calcification generates protons for nutrient and bicarbonate uptake abstract the biosphere s great carbonate deposits from caliche soils to deep sea carbonate oozes precipitate largely as by products of autotrophic nutrient acquisition physiologies protons constitute the critical link calcification generates protons which plants and photosynthetic symbioses use to assimilate bicarbonate and nutrients a calcium atpase based trans mechanism underlies most biological calcification this permits high calcium carbonate supersaturations and rapid carbonate precipitation the competitive advantages of calcification become especially apparent in light and nutrient deficient alkaline environments calcareous plants often dominate the lower euphotic zone in both the benthos and the plankton geographically and seasonally massive calcification concentrates in nutrient deficient environments including alkaline soils coral reefs cyanobacterial mats and coccolithophorid blooms structural and defensive uses for calcareous skeletons are sometimes overrated

eustatic curve for the middle jurassic cretaceous based on russian platform and siberian stratigraphy zonal resolution we have used the stratigraphy of the central part of the russian platform and surrounding regions to construct a calibrated eustatic curve for the bajocian through the santonian the study area is centrally located in the large eurasian continental craton and was covered by shallow seas during much of the jurassic and cretaceous the geographic setting was a very low gradient ramp that was repeatedly flooded and exposed analysis of stratal geometry of the region suggests tectonic stability throughout most of mesozoic marine deposition the paleogeography of the region led to extremely low rates of sediment influx as a result accommodation potential was limited and is interpreted to have been determined primarily by eustatic variations the central part of the russian latform thus provides a useful frame of reference for the quantification of eustatic variations throughout the jurassic and cretaceous the biostratigraphy of the russian platform provides the basis for reliably determining age and eustatic events the mesozoic section of the central part of the russian platform is characterized by numerous hiatuses in this study we filled the sediment gaps left by unconformities in the central part of the russian platform with data from stratigraphic information from the more continuous stratigraphy of the neighboring subsiding regions such as northern siberia although these sections reflect subsidence the time scale of variations in subsidence rate is probably long relative to the duration of the stratigraphic gaps to be filled so the subsidence rate can be calculated and filtered from the stratigraphic data we thus have compiled a more complete eustatic curve than would be p ssible on the basis of russian platform stratigraphy alone relative sea level curves were generated by backstripping stratigraphic data from well and outcrop sections distributed throughout the central part of the russian platform for determining paleowater depth we developed a model specifically designed for this region based on paleoecology sedimentology geochemistry and paleogeography the curve describes a series of high frequency eustatic events superimposed on longer term trends many of the events identified from our study can be correlated to those found by haq et al 1988 and other sea level studies from other parts of the world but there are significant differences in the relative magnitudes of events because the eustatic curve resulting from this study is based on a stable reference frame the curve can be used in sedimentary basin modeling and as a tool for quantifying subsidence history from the stratigraphy of passive margins basins and other active regions

importance of high frequency tectonic sequences during greenhouse times of earth history the relative importance of tectonism in the stratigraphic record should be more clearly expressed during greenhouse times of earth history due to the lack of overmasking effects of high frequency and high amplitude sea level changes typical for icehouse periods establishment of the importance of tectonism especially at temporal scales comparable to durations of typical transgressive regressive cycles has been plagued by poor temporal resolution our outcrop and subsurface based study of a cenomanian shallow marine siliciclastic interval constrained by bentonite based geochronology and detailed biostratigraphy examines this problem in a 2 2 m y interval we identified four tectonically driven erosional surfaces that dominate preserved stratigraphy biostratigraphic correlation to a sea level curve for the cenomanian where coeval high frequency lowamplitude eustatic cyclicity has been demonstrated allows the first direct comparison of the effects of eustasy and tectonics at temporal scales of hundreds of thousands of years during a global greenhouse time we suggest that minor tectonic pulses locally overshadow the effects of eustasy and exert the dominant control over preserved stratigraphy while subtle tectonic control on sedimentation has been documented throughout the cretaceous western interior the results of this study suggest that much of that deformation occurred at sub million year frequencies and at time scales comparable to eustatic transgressiveregressive cycles

microcodium an extensive review and a proposed non rhizogenic biologically induced origin for its formation abstract microcodium has been previously described as a mainly cenozoic calcification pattern ascribed to various organisms a review of the available literature and our data reveal two peaks in microcodium abundance the moscovian early permian and the latest cretaceous paleogene a detailed analysis of late paleozoic and cenozoic examples leads to the following new conclusions typical microcodium forming unilayered corn cob aggregates of elongated grains and thick multilayered palisade replacing structures cannot be linked to smaller grained intracellular root calcifications as became widely accepted after the work of klappa klappa c f 1979 calcified filaments in quaternary calcretes organo mineral interactions in the subaerial vadose environment j sediment petrol 49 955 968 typical microcodium is recognized from the early carboniferous with doubtful devonian reports to quaternary as a biologically induced mineralization formed via dissolution precipitation processes in various aerobic ca rich soil and subsoil terrestrial environments morphology and 13c signatures of microcodium suggest that neither plants algae or roots and root associated mycorrhiza regulate the formation of these fossil structures non recrystallized microcodium grains basically consist of slender 1 5 4 m curved radiating monocrystalline prisms with occasionally preserved hyphae like morphology thin 0 5 3 m hypha like canals can also be observed these supposed hyphae may belong to actinobacteria however thin fungal mycelia cannot be excluded we propose a model of microcodium formation involving a mycelial saprotrophic organism responsible for substrate corrosion and associated bacteria capable of consuming acidic metabolites and caco3 reprecipitation into the microcodium structures

micromorphology of calcitic features in highly calcareous soils of fars province southern iran abstract the micromorphology of calcitic pedofeatures in highly calcareous arid and semiarid soils of the fars province southern iran has been studied in order to determine their genesis and distribution in different climatic regions available soil moisture soil temperature soil texture vegetation and availability of calcium carbonate are amongst the main factors determining the type and morphology of calcitic features size and frequency of microcrystalline calcite nodules and coatings increase from aridic to xeric but decrease again towards the areas with a ustic moisture regime cytomorphic and acicular calcite are observed mainly in areas with an ustic moisture regime and a denser vegetative growth but rarely in xeric areas layered pendents of calcite are common beneath coarser fragments but are considered as relicts of a more humid paleoclimate calcite depletion pedofeatures are observed in xeric mesic areas with higher available soil moisture ultraviolet uv violet vl and blue light bl fluorescence and cathodoluminescence cl studies proved to be useful in differentiating in this region pedogenic from geogenic calcite all types of pedogenic calcite were uv and bl fluorescent but didn t show cl whereas limestone fragments showed cl but no uv bl fluorescence the absence of cl in the studied pedogenic calcite samples is suggested to be related to the oxidative environment hindering mobilisation of mn

soil parent material relationship in a mountainous arid area of kopet dagh basin north east iran abstract the effects of parent rock types on soil evolution in arid areas were studied in a sequence of soils derived from different lithologies in the kopet dagh basin northeastern iran using micromorphology clay mineralogy magnetic susceptibility and physico chemical properties the selected parent rocks and associated soils were shale haplocalcids claystone haplotorrerts gypsiferous marl haplogypsids limestones haplocalcids and torriorthents siltstone and sandstones torriorthents the results showed that the properties and development of soils were mainly affected by grain size and mineralogy of parent materials soil magnetic susceptibility lf variations were attributed to the types of parent material and pedogenic processes redistribution of calcite and gypsum in soil profiles and natural and pedogenic formation of ferrimagnetic minerals were responsible for lf variations the soils clay mineral origins were found to be mainly of inheritance from parent materials smectite was the dominant clay mineral of the most soils based on the micromorphological index of soil evolution miseca the soils studied were categorized into weakly developed orthents weakly to moderately developed aridisols gypsids and calcids and moderately developed soils including calcids and torrerts the degree of microstructure development alteration of weatherable minerals and calcitic features were the most important criteria influencing assessment of soil development degree by miseca index the vertic features were only observed in soils of claystone in which there were considerable amounts of clay and smectite high amounts of gypsum and low smectite content were mainly responsible for the lack of vertic behavior in other fine grained soils derived from shale and marl

enigmatic sedimentary structures in the lower old red sandstone south wales uk possible microbial influence on surface processes and early terrestrial food webs several enigmatic sedimentary structures are present in upper silurian and lower devonian terrestrial rocks of south wales these are millimetre ripples wrinkle structures cauliflower and molehill structures calcretized matgrounds pepper pots and fairy rings most of the structures occur on fine grained sandstone bedding surfaces in both inclined and non inclined red heterolithic deposits that form a large part of the lower old red sandstone in south wales these deposits consist of conspicuous units up to 3 m thick comprising millimetre to centimetre scale laminasets of alternating mudstone and fine grained sandstone interpreted as muddy point bars on ephemeral channel margins crevasse splay lobes or distal flood out deposits from ephemeral flow they are rich in trace fossils reflecting animal locomotion burrowing foraging ploughing and resting millimetre ripples and wrinkle structures are related to rapid growth of cyanobacterial mats on wet sediment surfaces especially in films of standing water that may have been a critical constituent of the food chain for terrestrial communities pustular cauliflower and molehill structures are preserved on tuffs and have been linked to algal blooms formed following an increase in nutrients due to ashfall into floodplain ponds the tuffs are associated with a diverse ichnofauna indicating that opportunist colonizers took advantage of an abundant food source

classification of paleosols despite increased interest in paleosols during the past decade no satisfactory classification is in current use presented here is a largely descriptive classification system that utilizes those pedogenic features that have the highest preservation potential in the rock record emphasized in the classification are morphological and mineralogical features that are easily recognizable in the field and through the petrographic microscope the classification is based on evaluation of the relative prominence in a paleosol of six pedogenic features or processes organic matter content horizonation redox conditions in situ mineral alteration illuviation of insoluble minerals compounds and accumulation of soluble minerals the most prominent of these six features processes provides the key to classifying a paleosol into one of nine orders four of the order names are borrowed from soil taxonomy histosol spodosol oxisol vertisol whereas the other five order names are presented here for the first time calcisol gypsisol gleysol argillisol protosol the orders may be preceded by one or more subordinate modifiers that describe other important features of the paleosol the classification is relatively easy to apply to the rock record and should enhance communication and aid in the standardization of terminology

petroleum system and production characteristics of the muddy j sandstone lower cretaceous wattenberg continuous gas field denver basin colorado wattenberg field is a continuous type gas accumulation estimated ultimate recovery from current wells is 1 27 tcf of gas from the lower cretaceous muddy j sandstone mean gas resources that have the potential to be added to these reserves in the next 30 yr are 1 09 tcf this will be primarily through infill drilling to recover a greater percentage of gas in place and to drain areas that are isolated because of geologic compartmentalization greatest gas production from the muddy j sandstone in wattenberg field occurs 1 from within the most permeable and thickest intervals of fort collins member delta front and nearshore marine sandstones 2 to a lesser extent from the horsetooth member valley fill channel sandstones 3 in association with a large thermal anomaly that is delineated by measured temperatures in wells and by vitrinite reflectance contours of 0 9 and greater 4 in proximity to the bounding mowry graneros and skull creek shales that are the hydrocarbon source rocks and reservoir seals and 5 between the lafayette and longmont right lateral wrench fault zones wfzs with secondary faults that act as conduits in areas of the field the axis of greatest gas production is north 25 to 35 degrees northeast which parallels the basin axis recurrent movement along five right lateral wfzs that crosscut wattenberg field shifted the denver basin axis to the northeast and influenced depositional and erosional patterns of the reservoir and seal intervals levels of thermal maturity within the wattenberg field are anomalously high compared to other areas of the denver basin the wattenberg field thermal anomaly may be due to upward movement of fluids along faults associated with probable igneous intrusions areas of anomalous high heat flow within the field correlate with an increased and variable gas oil ratio

formation and environmental significance of late quaternary calcareous root tubes in the deserts of the alashan plateau northwest china calcareous root tubes are widely distributed across the badain jaran desert and the tengger desert of the alashan plateau in northwest china however the reliability of their 14 c dating results and their environmental significance remain unclear in this study the conventional 14 c ages of 31 calcareous root tube samples and one aquatic mollusc shell sample which were all collected from the badain jaran desert and the tengger desert were measured the results reveal that nine of the 14 calcareous root tube samples from the badain jaran desert were from marine isotope stage mis 3 while two samples were from mis 2 the other three samples were dated to the mid holocene one of which is consistent with the aquatic mollusc shell sample collected from the shoreline of zhunzhahanjilin lake in the badain jaran desert moreover the 17 calcareous root tube samples from the tengger desert were all dated to the mid and late holocene most of which were from the mid holocene the results demonstrate that calcareous root tubes can be used as

calcareous crusts on exposed pleistocene limestones a case study from grand cayman british west indies abstract calcareous crusts which include laminar up to 6 cm thick and non laminar calcretes have developed on ooid grainstones and skeletal wacke pack grain floatstone in the pleistocene ironshore formation exposed at morgan s harbour tarpon springs and rogers wreck point on grand cayman british west indies non laminar calcretes which consist largely of micrite with variably altered skeletal fragments and lithoclasts derived from the host limestone contain peloids in their basal parts in contrast the laminar calcretes are formed of porous laminae and low porosity laminae calcified roots are common in the porous laminae but rare in the low porosity laminae the 18o values of calcretes from 5 22 to 0 16 have a positive correlation with the 13c values that vary from 10 03 to 6 41 at tarpon springs from 11 57 to 5 43 at morgan s harbour and from 9 89 to 8 68 at rogers wreck point the non laminar calcretes reflect progressive micritization of the bedrock with a basal peloidal zone that passes upward into the micrite zone in contrast laminar calcretes are attributed to accretionary build up dictated by microscale processes that were controlled largely by the interplay of plant roots and their associated microorganisms the positive correlation between the 18o and 13c values from the calcareous crusts indicates that evaporation influenced calcite precipitation the 13c values of the laminar calcretes record a change from vegetation dominated by c3 plants that grew in a cool wet climate to a c3 c4 vegetation that grew in a hotter drier climate the cayman calcretes resemble those found on the pleistocene miami limestone in florida and highlight the possibility that these calcareous crusts may reflect regional climates and may therefore enable regional stratigraphic correlation

geologic and seismic models muddy sandstone lower cretaceous bell creek rocky point area powder river basin montana and wyoming abstract the muddy sandstone in the northern powder river basin consists of two distinct members genetic units that are separated by a widespread subaerial surface of erosion the older sandstone member the reservoir rock at the giant bell creek field was deposited in shoreline and associated nearshore marine environments it is genetically related by intertonguing to the underlying skull creek shale the younger member is a valley fill deposit of fluvial estuarine and tidal flat environments the deposition and distribution of these two genetic units were controlled primarily by relative sea level changes the bell creek sandstone was deposited as a widespread regressive sandstone during a highstand of sea level a following sea level lowstand caused valley cutting erosion of all or portions of the bell creek sandstone and paleosoil development causing early diagenesis especially of kaolinite siderite and quartz a rising sea level resulted in valley filling coastal onlap and a transgressive surface of erosion that is overlain by black marine shale nefsy or shell creek recurrent movement on basement controlled fault blocks appears to have controlled distribution of the muddy members drainage incisement patterns present structure and heat flow and possibly petroleum migration seismic modeling indicates that it may be possible to recognize seismically the distribution of muddy reservoir facies that occur in the area seismic modeling suggests that the amplitude response of the muddy is influenced by muddy facies and thickness changes the lowest muddy amplitude observed occurs when the bell creek sandstone is prevalent an increase in the muddy amplitude is noted when thick valley fill deposits are present results from seismic modeling compare well to actual seismic data amplitude changes noted in the muddy reflector in the bell creek rocky point area may help explorationists in the future to distinguish between nonprospective and reservoir quality muddy sandstone

carbonate features in the uppermost layers of quaternary deposits northern armenia and their significance for paleoenvironmental reconstruction recent archaeological studies in the lori depression of armenia lesser caucasus revealed a series of multilevel early paleolithic acheulian sites belonging to the early middle pleistocene stage of occupation of the caucasus in the uppermost layers of these sites the paleosols and sediments contain carbonate features cfs whereas the lower layers are absolutely free from carbonates the aim of this work is to examine the role of detected cfs as an indicator for reconstructions of the early middle pleistocene paleoenvironments to determine the source time and conditions of carbonates accumulation in initially non calcareous and high degree weathered humid paleosols three sections were studied kurtan i points 1 2 and muradovo there are different forms of cfs represented by the calcified root cells in the layer 1 the hard nodules in the layer 2 and the laminae like carbonates in the layer 3 of the sites studied all the cfs are of the aqueous hydrogenic origin the cfs of the uppermost layers 1 and 2 in the kurtan i point 2 were accumulated in the holocene lake the calcified root cells were formed on the swamp shore whereas the hard nodules on the lake bottom under stagnant water the laminae like carbonates in the layer 3 were accumulated in the kurtan i and muradovo sections due to strong erosion cycle s in the late pleistocene interglacial period s that led to the limestone scour in the region by ground and surface water they reflect the earliest stage of the allochthonous carbonate accumulation in the area dated by radiocarbon method to approximately 20 ka cal bp therefore all the cfs cannot be regarded as indicative of early and middle pleistocene environmental changes as they appeared in the uppermost layers of the studied sections much later than the time of formation for the surrounding groundmass

palaeosols as indicators of geomorphic stability in two old red sandstone alluvial suites south wales palaeosols fossil soils are abundant in the alluvial late silurian early devonian moor cliffs formation and rat island mudstone freshwater west formation of south dyfed south wales the palaeosols occur in thick mudstones deposited on floodplains under a seasonal semi arid climate and represent vertisol type soils simple single profiles are rare and most of the mudstone intervals exhibit complex overprinted profiles however a major difference exists between the palaeo vertisols in each of the two units studied the moor cliffs formation contains thick floodplain intervals with evidence of frequent erosion and reactivation of earlier soil horizons the associated coarser channel deposits mainly represent ephemeral streams the alluvial system was unstable flashy and prone to extensive stripping of stored floodplain sediment arroyos unstable ephemeral stream channels probably developed during this interval evidence for any marine influence on soil development is missing and previous speculations that the formation may represent deposition in an upper intertidal or supratidal system are not supported the rat island mudstone represents a complete contrast in that there was little or no stripping of floodplain sediments the channel deposits are typically of the fining upwards type representing more stable low sinuosity channels and with ephemeral stream floods by integrating the palaeosols a more detailed picture of the geomorphic history of these units can be formulated comparison with contemporary drainage basins indicates that a change in climate was a possible cause for the differences between the two units less frequent and more severe storms occurring during the deposition of the rat island mudstone

high resolution sequence stratigraphy of early transgressive deposits viking formation joffre field alberta canada the lower cretaceous viking formation of the joffre field is characterized by complex reservoir architecture deposits of three discrete sequences were delineated using high resolution sequence stratigraphy the coarse grained deposits of sequence 3 lying between bd 2 and an overlying open marine flooding surface comprise the main reservoir interval within the viking formation of the joffre field this succession has previously been interpreted as an incised conglomeratic shoreface stranded in a basinal position during transgression however sequence 3 displays characteristics difficult to reconcile with a shoreface interpretation including an abundance of brackish mudstone interbeds and rip up clasts dominance of trough cross stratification in the coarse clastics and large scale interfingering of the coarse clastics with fine grained marginal marine deposits despite the incised basal contact and brackish water characteristics of the deposits the succession does not reflect an estuarine incised valley complex as conventional sequence stratigraphic wisdom might suggest the shore parallel orientation of the deposit the lack of a convincing valley margin to the northeast and parasequence orientations lying parallel to the strike of the deposit are inconsistent with an incised valley interpretation instead the succession is interpreted as a broad brackish water embayment of the shoreline into which coarse clastic bayhead delta and distributary channel complexes were deposited during incremental transgression such lagoonal or brackish bay complexes are ubiquitous in modern transgressive shorelines but previously have been recognized only rarely in the ancient record

geochemical perspectives on coral mineralization corals open an exceptional window into many phenomena of geological geochemical climatic and paleontological interest from the paleozoic to the present corals provide some of the finest high resolution archives of marine conditions corals are likewise exceptional for chronometric purposes and even the terrestrial 14c timescale has now been calibrated against coral 230th 234u corals also represent a testing ground for basic ideas about mineralogy and geochemistry the shapes sizes and organization of skeletal crystals have been attributed to factors as diverse as mineral supersaturation levels and organic mediation of crystal growth the coupling between calcification and photosynthesis in symbiotic corals is likewise attributed to everything from photosynthetic alkalinization of the water to efforts by the coral to prevent photosynthetic alkalinization corals also leave a significant geochemical imprint on the oceans their aragonite skeletons accept about 10 times more strontium than does calcite hence the proportion of marine aragonite precipitation affects the oceanic chemical balance biological carbonates represent the biosphere s largest carbon reservoir hence calcareous organisms affect the ocean s ph co2 content and ultimately global temperatures through the greenhouse gas connection finally corals present some geochemical puzzles for ecology and conservation how do symbiotic corals obtain nutrients in some of the most nutrient deficient parts of the planet are global geochemical changes partially responsible for the widespread declines in coral reefs during recent decades we will address many of these issues but will concentrate on coral skeletal structure and calcification mechanism these topics bear most directly on the biomineralization process and generally affect the choice of skeletal materials and analytical techniques used in geochemical investigations the coral reef is probably the planet s most spectacular biomineralization product these grand and complex ecosystems build on the accumulated skeletal debris of countless generations of organisms especially calcareous algae and symbiotic

the palaeoenvironment and deformation of beaconites like burrows in the old red sandstone at gortnabinna sw ireland the gortnabinna area contains a number of well preserved deformed burrows within the fluviatile old red sandstone of s ireland detailed logging of the local succession enables subdivision into four facies facies 1 represents sheet flood deposits facies 2 ephemeral stream channels facies 3 marginal sheet flood deposits and facies 4 low energy settling of fines the burrows occur in facies 1 and 4 the sediments are now folded into a large upright westward plunging anticline the fold has a well developed axial planar cleavage and is extended along strike by listric normal faults the burrows in facies 1 were originally circular and orthogonal to bedding and reveal a n s layer parallel shortening strain of 2 1 followed by a shear strain of 1 48 during folding these burrows have a bimodal distribution of diameters with peaks in the ranges 50 80 and 110 170 mm the burrows of facies 4 are sub parallel to the bedding plane and are generally curved with a maximum width of 180 mm and lengths of up to 2 3 m these burrows display passive infill following abandonment the burrows are morphologically similar though distinct from beaconites barratti which has been described from elsewhere in the old red sandstone and are tentatively interpreted as lungfish burrows

revised stratigraphy depositional systems and hydrocarbon exploration potential for the lower cretaceous muddy sandstone northern denver basin the reservoir sandstones of the lower cretaceous muddy sandstone the major hydrocarbon producing reservoir in the northern denver basin are restructured into six informal members ms 1 to ms 6 based on sedimentary structures ichnofacies geophysical logs bounding discontinuities and sediment distribution patterns bounding discontinuities defining allostratigraphic units are used to assign these six informal members to three major depositional systems that may be used to redefine hydrocarbon reservoirs leading to new exploration targets in this mature basin

petrography micromorphology and genesis of holocene pedogenic calcrete in al jabal al akhdar sultanate of oman abstract holocene pedogenic calcrete nodules occur within quaternary terra rossa soil that fills shallow phytokarst cavities in the permian triassic carbonate sequence of al jabal al akhdar in the sultanate of oman they are preferentially clustered around plant roots and are almost wholly formed of calcite holocene pedogenic calcrete nodules developed within a mediterranean like climate that is characterized by intermittent wet and dry seasons petrographic examination revealed that the host terra rossa soil is partially calcitized and that the calcrete nodules consist of smaller coalesced diffused and or discrete granular nodules the latter consist of several types of rhizoliths floating in a groundmass formed of micrite and microspar as well as spar to a lesser extent several textures of calcrete groundmass are recognized the most common is partially neomorphosed micrite three types of rhizoliths are recognized root moulds root casts and petrified calcified root tissues the latter were developed by mimic replacement of the tissue cells by cytomorphic calcite sem investigation of the calcite forming the calcrete nodules revealed that it consists of closely stacked sheets formed of calcareous nanoglobules agglutinated by eps and entombed calcareous microbial fossils which indicate a biogenic origin the calcareous nature of the bedrock climatic conditions and prevalence of biological activities of microorganisms associated with the plant root system in the host soil have significantly controlled the development and texture of these nodules the relative abundance of scalenohedral calcite within the calcrete groundmass is attributed to the impact of mg ions and organic compounds it has been concluded that the studied pedogenic calcrete is a type of freshwater terrestrial thrombolitic microbialite this study may help improve the understanding of the palaeoenvironmental conditions of analogue fossil calcretes

occurence of the trace fossil beaconites antarcticus in the lower carboniferous fluviatile rocks of county mayo ireland abstract large straight curved or sinuous endichnial burrows with a meniscus pattern of infilling are described from lower carboniferous red beds of county mayo ireland the burrows have been identified as beaconites antarcticus the burrows show a strong facies association being concentrated in the upper parts of sandstones deposited during floods in shallow possibly ephemeral stream channels they appear to be absent from the overlying non red fluvial sandstones which show evidence for deeper more sinuous and more permanent channels it is suggested that burrowing was related to varying moisture content of the sediment the burrows were probably formed by locomotory back packing of arthropods or vertebrates but the precise nature of the producer remains unknown

clay mineral assemblages of the townsend tuff bed lower old red sandstone south wales and the welsh borders suites of samples from the townsend tuff bed possess widely varying clay mineralogies which may be divided into 5 major assemblages showing a general increase in diagenetic grade from smectite illite kaolinite to chlorite illite to the w this trend appears to be related to depth of burial fold style and proximity to basement illite crystallinity closely parallels cleavage development

carbon isotopic subsets of soil carbonate a particle size comparison of limestone and igneous parent materials abstract the c isotopic analysis of pedogenic carbonate is an important method for investigating paleoclimatic conditions and carbon sequestration however a calcic soil sample may contain multiple types of carbonate especially in soils formed in limestone parent material to evaluate isotopic values of the different soil carbonate types stable c isotopic analysis was applied to an array of particle size classes in bulk soil that was collected from soils formed in limestone parent material and neighboring soils formed in igneous parent material a pronounced trend of decreasing 13 c with progressively decreasing soil particle size was revealed in soils of both parent materials ranging from about 2 to 6 for limestone soils and 1 to 5 for igneous soils thin section microscopy and radiocarbon dating also indicated multiple subsets of calcium carbonate types in soils thin section analysis disclosed the presence of limestone detritus calcitans aggregates of carbonate crystals and calcified root hairs radiocarbon dating revealed different 13 c values of carbonate crystals of different ages ranging from about 2620 to 40 290 years for limestone soils and 1660 to 5830 years for igneous soils these results indicate 1 limestone particles in soil may contribute to a complex mixture of 13 c values that is absent from soils formed in igneous parent material and 2 it is necessary to recognize that isotopic values of bulk soil represent a mixture of different 13 c values from different size fractions and ages in both limestone and igneous soils

microcodium revisited root calcification products of terrestrial plants on carbonate rich substrates abstract microcodium is a problematic calcitic microfeature of many calcretes and calcareous paleosols in the cretaceous and tertiary continental and marine successions of the peri tethyan realm the main controversy about the microcodium structures is their origin and possible relation with calcified plant roots microcodium and rhizogenic root formed microfabrics were studied in calcrete profiles within the paleocene shallow marine carbonate succession in southwestern slovenia the prominent laminar calcrete horizons contain abundant calcite aggregates 150 m to 1 cm in size with perfectly preserved structural details of plant root tissues morphology and structure of these aggregates indicate that they formed through biologically controlled precipitation of calcium carbonate within the root cortical cells the morphologies intermediate between the typical microcodium aggregates composed of a single layer of individual elongate pyramidal or prismatic crystals of calcite measuring 100 500 m in length and 20 70 m in width and calcified roots with multilayer arrangement of isodiametric cells were observed and this supports previous rhizogenic interpretations of microcodium structures intermediate forms show that the typical microcodium aggregates formed through morphological transformation of the root tissue by growth of the calcite within the cortical cells which distorted the cell shape calcification of roots and the creation of microcodium structures can be explained as an effective nutrient acquiring mechanism used by certain types of terrestrial plants inhabiting nutrient poor calcareous substrates the widespread occurrence of microcodium in almost unaltered shallow marine limestones indicates that its formation took place during early stages of paleosol development probably reflecting specific types of vascular plants of a pioneer community that were able to colonize carbonate substrates during the early phases of subaerial exposure

endomycorrhizae in miocene paleosols implications in biotite weathering and accumulation of dolomite in plant roots sw madrid basin spain abstract this work provides evidence of arbuscular mycorrhizae or endomycorrizhae and their role in mineral weathering and soil carbonate production from miocene paleosols formation of the paleosols bearing mycorrhizae took place in marginal lacustrine and distal fan deposits in the madrid basin endomycorrizhae fossils are preserved as carbonate in biotite filled rhizoliths fossilized mycorrhizae are morphologically identical to those of living counterparts and consist of two linked parts the extraradicular segment surrounding the root is represented by a calcitic mycelium comprising spores and two types of hyphae that are seen to attach and to corrode the mineral grains the intraradicular part is made of a network of branched filaments hyphal coils arbuscules and likely vesicles that are mixed with the cortical root cells of the plants fossilized as dolomicrosparite aggregates the preferential formation of the dolomite aggregates on biotite grains in rhizoliths is interpreted to reflect a focused interest of the plants on this mineral and indicates the mineral may have been used as a source of plant nutrients the close association of the carbonate with the silicate further suggests that the precipitation of dolomite in the root cells and the weathering of the biotite resulted from interrelated processes main mechanisms to produce mineral dissolution include organic acids and chelate secretions by the plant roots and fungi which would remove nutrients these results confirm that carbonate paleosols provide an excellent reservoir of information on ecological interactions and biogeochemical cycling and expand the range of biogenic processes and their resultant products involved in the formation of carbonate soils this approach has broad applications given the abundance of carbonate paleosols and the endomycorrhiza record dating back 400 million years

micromorphology of periglacial sediments from the tayara site qikirtaq island nunavik canada abstract soil micromorphology provides an excellent resource for investigating palaeoeskimo site formation processes in the low arctic periglacial environment in this study micromorphology was used to answer questions concerning the composition structure origin and depositional agencies of the tayara site active layer s sediments as well as to distinguish between natural geogenic biopedogenic and cultural anthropogenic processes five groups of microfeatures were documented these include 1 biopedological features soil organic matter accumulation mesofaunal and fungal activities 2 transport inherited features related to depositional processes solifluction and stream sedimentation 3 frost induced microstructures and cryogenic features such as major post depositional changes ice segregation particle rearrangement frost shattering cryoturbation 4 bone preservation in the active layer at the microscopic level and 5 anthropogenic features related to palaeoeskimo activities the sediments from the three archaeological levels i ia and ii appear to have been very little influenced by anthropogenic factors cultural processes are micromorphologically observed in level ii with some evidence of feeding bone presence burning wood charcoal heated bone and possibly trampling however the effects of natural processes on the sediments are more pronounced than anthropogenic ones

a classification of rhizogenic root formed calcretes with examples from the upper jurassic lower cretaceous of spain and upper cretaceous of southern france discussion

near surface shrinkage and carbonate replacement processes arran cornstone formation scotland a 47 m thick succession of conglomerates sandstones and mudstones of late devonian or early carboniferous age outcrops at fallen rocks in northeast arran western scotland it is defined here as the type section of the arran cornstone formation at numerous levels in the succession varieties of fissures and carbonate concretions formed during the accumulation of the formation the fissures opened as a result of drying shrinkage and were closed again either by filling with different sediment or by wetting and expansion of the fissure wall sediment carbonate concretions form complete beds discontinuous bedding concordant sheets or bedding discordant nodules or rods the rod cornstones these concretions formed close enough to the surface to be incorporated after erosion and redeposition as clasts into overlying beds the concretions were formed by growth of micrite mainly by replacement but shrinkage displacement played an important role in subsequently fracturing and reworking the micrite the micrite was also locally replaced by microspar and spar and this involved dissolution and precipitation no independent evidence of biological influence in any of these processes has been found

late albian kiowa skull creek marine transgression lower dakota formation eastern margin of western interior seaway u s a abstract an integrated geochemical sedimentological project is studying the paleoclimatic and paleogeographic characteristics of the mid cretaceous greenhouse world of western north america a critical part of this project required to establish a temporal framework is a stratigraphic study of depositional relationships between the albian cenomanian dakota and the upper albian kiowa formations of the eastern margin of the western interior seaway wis palynostratigraphic and sedimentologic analyses provide criteria for the dakota formation to be divided into three sedimentary sequences bounded by unconformities d0 d1 and d2 that are recognized from western iowa to westernmost kansas the lowest of these sequences defined by unconformities d0 and d1 is entirely upper albian and includes the largely nonmarine basal dakota lower part of the nishnabotna member strata in western iowa and eastern nebraska and the marine kiowa formation to the southwest in kansas the gravel rich fluvial deposits of the basal part of the nishnabotna member of the dakota formation correlate with transgressive marine shales of the kiowa formation this is a critical relationship to establish because of the need to correlate between marine and nonmarine strata that contain both geochronologic and paleoclimatic proxy data the basal gravel facies up to 40 m thick in western iowa aggraded in incised valleys during the late albian kiowa skull creek marine transgression in southeastern nebraska basal gravels intertongue with carbonaceous mudrocks that contain diverse assemblages of late albian palynomorphs including marine dinoflagellates and acritarchs this palynomorph assemblage is characterized by occurrences of palynomorph taxa not known to range above the albian kiowa skull creek depositional cycle elsewhere in the western interior and correlates to the lowest of four generalized palynostratographic units that are comparable to other palynological sequences elsewhere in north america tidal rhythmites in mudrocks at the ash grove cement quarry in louisville cass county nebraska record well developed diurnal and semimonthly tidal cycles and moderately well developed semiannual cycles these tidal rhythmites are interpreted to have accumulated during rising sea level at the head of a paleoestuary that experienced at least occasional mesotidal conditions this scenario places the gravel bearing lower part of the nishnabotna member of the dakota formation in the mouth of an incised valley of an upper albian transgressive systems tract deposited along a tidally influenced coast furthermore it provides a depositional setting consistent with the biostratigraphic correlation of the lower part of the nishnabotna member of the dakota formation to the marine kiowa formation of kansas

genesis of blackened limestone clasts at late cenozoic subaerial exposure surfaces southern australia abstract black limestone clasts are present across the globe at modern and ancient subaerial exposure surfaces and in intertidal and supratidal environments these problematic clasts are particularly abundant at multiple subaerial exposure surfaces across southern australia the genesis of such exceptionally preserved clasts can be interpreted through universal fabrics across wide geographic regions and geologic ages regardless of location or age all south australian blackened clasts studied have a similar microstructure that is dominated by porous micritic laminae and chambered tubules such laminae are interpreted to represent calcified root cells and occur in two different varieties 1 micrite walled tubules with hollow centers that are thought to represent calcification in the rhizosphere or outer surfaces of the root and 2 tubules consistent with calcification of both the medulla and cortex which preserved medulla cortex and parenchymatic cells along with xylem vessels preserved root fabrics are present only in the blackest clasts and are consequently thought to be the main mechanism driving limestone blackening the dark coloration in southern australian clasts is derived from the impregnation of partially decayed terrestrial organic substances these organic substances were trapped in the cellular structures of roots as they calcified and were subsequently prevented from further decay and oxidation a threshold of approximately 7 weight organic carbon is needed in the insoluble residue to produce the distinct black coloration in limestone this process occurs at the base of slightly organic rich humic soil profiles where they interact with underlying carbonate bedrock b c soil horizon roots both physically and chemically through acid secretion corrode the underlying limestone and provide the calcium bicarbonate needed in the root calcification process specific semiarid flora have the ability to calcify their cellular structures which could explain why blackened clasts occur at only some unconformities this result means that the formation of blackened clasts via root calcification and entrapment of organics relies upon specific conditions of semiarid plants and climate along with organic soils such conditions would be restricted to a specific climate regime and when combined with the new proposed blackening mechanism herein could help explain their limited distribution and occurrences worldwide

occurrence formation and micromorphology of gypsum in soils from the central german chernozem region occurrence of gypsum in soils from loess of the central german chernozem region indicates that local climatic conditions with low precipitation average 500 mm a 1 and a real evaporation between 450 and 460 mm do not allow leaching of weakly soluble gypsum from soils at a site close to the strip mine etzdorf gypsum is accumulated in the ck horizon of a haplic chernozem down to a depth of about 1 5 m its distribution being nonuniform calculated total gypsum in the haplic chernozem amounts from 10 20 t ha 1 the highest accumulation of gypsum obviously by solution transport and evaporation can be observed in a profile exposed to the air since about 1960 in this profile maximum so42 values however are not found on the surface of the outermost aggregates with whitish efflorescence but at 20 cm depth in the profile in a eutric podzoluvisol the precipitation of gypsum developed on living roots as well as in pores of former roots in a buried chernozem large euhedral gypsum crystals with a diameter of up to 1 5 cm were found gypsum crystals occur in different shapes and sizes such as euhedral lenticular rosette like and equigranular ones even soils having undergone leaching processes reveal unusual increases of so42 at 40 50 cm depth this may be an indicator of more recent so42 input due to atmospheric deposition since the beginning of industrialization it is supposed that gypsum is formed by the reaction of atmogenic sulfuric acid with different ca sources in the soil

stratigraphic architecture of the tonganoxie paleovalley fill lower virgilian in northeastern kansas lower pennsylvanian paleovalley confined sandstones are important petroleum reservoirs in the midwest in kansas such reservoirs have produced approximately 220 million bbl of oil and 1 7 tcf of gas valley fill successions tend to become muddy upward but there can be considerable local heterogeneity in which reservoir sandstones pass laterally into muddy sandstones or nonreservoir shales the lack of understanding of this reservoir heterogeneity can lead to low drilling success rates the tonganoxie paleovalley upper pennsylvanian northeastern kansas contains facies very similar to lower pennsylvanian morrowan valley fills and can provide an outcrop and subsurface based model of sandstone deposition the tonganoxie paleovalley was incised during lowered sea level and filled during the subsequent transgression the main paleovalley is approximately 41 m deep 11 km wide and 240 km long and was fed by 1 km wide tributary valleys oriented roughly normal to the trunk valley sandstones occur in four distinct architectural elements that were deposited during different phases of transgression type i sandstone consists of a belt of sandstone and conglomerate 3 18 m thick and confined to the trunk valley and wider portions of tributary valleys type i sandstone consists of amalgamated channel fills has little or no mud and has the highest porosity and permeability the type i sandstone is overlain by estuarine deposits of sandstone type ii sandstones rippled argillaceous sandstone to sandy mudstone and coal most of the paleovalley was filled during this stage the type ii sandstones are narrow 1 5 km wide arcuate bodies up to 8 km long and were likely deposited in tidal point bars near the fluvial to tidal transition are either isolated sandstone bodies or are incised into type i sandstone the higher mud content is expected to reduce porosity and permeability compared to fluvial facies type iii sandstone bodies occur at the upstream limits of narrow tributaries and are probably bay head deltas well logs indicate a range of mud content type iv sandstone is a thin 3 m discontinuous sheet of marine sandstone deposited after most of the paleovalley had been filled

possible climate variability in the lower old red sandstone conigar pit sandstone member early devonian south wales uk abstract the early devonian conigar pit sandstone member cpsm of the freshwater west formation lower old red sandstone lochkovian age at freshwater west in south wales comprises a heterolithic predominantly alluvial suite mudstones fine to coarse grained sandstones conglomerates with varying depositional architecture a number of discrete facies associations are observed the fine grained inclined and non inclined heterolithic association is dominant within the cpsm it represents dryland sinuous channelized flow ihs bedsets and unconfined flow non inclined bedsets at terminal and intermediate floodouts deposited under semi arid conditions mudstones were deposited in two distinct environments associated with this semi arid river system laminated and burrowed reddish brown mudstones were deposited in shallow semi permanent lakes or pools on the floodplain massive mudstones were deposited as within channel muddy braid bars with sedimentary structures being lost during subsequent compaction the mudstones exhibit vertisol pedogenesis reflecting the seasonal wetting and drying associated with the semi arid climate periods of intense desiccation are indicated by deep desiccation cracks and associated rubbly surfaces possible though unproven tidal conditions influenced a small percentage of the heterolithic channels at freshwater west the extent of these channels is uncertain the coarser grained multi storey sandstone association was deposited by low sinuosity rivers with a fluctuating but perennial discharge associated with these laterally extensive sandbodies was a high water table with surface ponding wetlands that enabled the preservation of plant detritus during high discharge events flow expanded over the contemporaneous floodplain depositing the sheet sandstone association within splay complexes the interpretation that perennial discharge may have been triggered by basin wide climate change challenges the long held view that the lower ors climate was continuously semi arid in nature the spatial temporal extent of this climate change is uncertain as it is possible that the multi storey sandbodies were deposited by allogenic rivers draining a distant possibly uplifted source area a decrease in the observed frequency and maturity of vertisol profiles and a corresponding increase in multi storey sandbodies upward through the succession may reflect a long term episodic pattern of climate change

indication of millennial scale moisture changes by the temporal distribution of holocene calcareous root tubes in the deserts of the alashan plateau northwest china abstract calcareous root tubes or rhizoliths have a strong potential for paleoenvironmental studies especially in reconstructing paleoenvironmental conditions and paleovegetation previous studies suggested that the effectivity of the moisture level affects the formation of calcareous root tubes in the deserts of the alashan plateau northwest china however it remains unclear whether the temporal distribution of calcareous root tubes can be used to reconstruct paleo effective moisture in this area in this study based on conventional 14c dating results of 34 holocene calcareous root tube samples collected from the badain jaran desert the tengger desert and the ulan buh desert in the alashan plateau of northwestern china millennial scale changes in paleo effective moisture during the holocene in this area were reconstructed the frequency of the 14c dating results demonstrates that 62 of the holocene samples were dated to 7 5 cal kyr bp and 38 of the holocene samples were dated to 4 2 cal kyr bp indicating an arid period during the early holocene before 8 0 cal kyr bp a humid period during the mid holocene 8 0 5 0 cal kyr bp and a humid to arid period during the late holocene after 5 0 cal kyr bp the reconstruction results were consistent with other previous reconstruction results from lake sediments and aeolian sand lacustrine sequences which indicated that temporal distribution of calcareous root tubes can reflect millennial scale changes in paleo effective moisture in this area however a single sample could indicate local environmental changes that may differ from the overall desert environmental changes hence the relatively humid environmental record obtained from the presence of calcareous root tubes is a local signal or a regional signal that should be noted

the newer granite problem a geotectonic view the siluro devonian suite of granitic plutons in the british caledonides known as the newer granites together with their associated extrusive rocks represent one of the most extensively researched examples of calc alkaline magmatism apparently related to orogeny although recent chemical studies have credibly interpreted some of the scottish intrusions and volcanic rocks as part of a continental margin magmatic arc generated by the subduction of lapetus oceanic lithosphere beneath laurentia insurmountable problems of distribution and timing arise when attempts are made to relate the magmatic activity as a whole to a traditional two plate collision model for the orogeny newer granite magmatism is here discussed in the context of more mobilistic models for the post grampian evolution of the british caledonides which involve e w closure between laurentia and baltica terminated by collision in the silurian followed by the northward accretion of gondwana derived terranes in the early devonian the former produced the main caledonian tectonometamorphism of the northern highlands of scotland the latter the late caledonian deformation of the slate belts in the paratectonic caledonides these models imply much more complex convergence geometries which can in principle account for the whole newer granite suite as a series of subduction generated magmatic arcs overlapping in space and time the model proposed involves three late caledonian magmatic arcs in addition to the ordovician borrowdale arc which is not considered in this paper one is related to laurentia baltica convergence with westward subduction beneath the scottish sector of the laurentian margin in the ordovician and early silurian which generated the early members of the newer granite suite in the highlands a second is related to northward silurian early devonian subduction at the solway line which generated the younger newer granites and volcanic rocks north of the highland border and a third related to northward accretion of the armorican terrane in early devonian time produced intrusive and extrusive magmatism as far south as southeast ireland and the english midlands

multiple cycles of wave dominated estuarine deposits in low accommodation settings cretaceous j sandstone northwestern nebraska the j sandstone comprises less than 46 m 151 ft of sandstone dominated strata within the mudrock dominated lower upper cretaceous succession of northwestern nebraska the unit is a prolific hydrocarbon producer in this region denver julesburg basin but its lithostratigraphic and sequence stratigraphic framework critical for reservoir characterization and mapping is poorly known we have achieved an improved understanding of depositional history and sequence stratigraphy by describing and correlating cores and wireline logs from wells within sioux dawes and box butte counties nebraska and niobrara and goshen counties wyoming coals paleosols fluvial or inner estuarine sandstones estuarine mudstones fluvial conglomerate shoreface sandstone and reworked volcanic fallout bentonite lithofacies were identified trace fossil assemblages representing stressed expressions of the skolithos and cruziana ichnofacies are common these lithofacies are arranged vertically into three erosionally based cycles each less than 28 m 92 ft thick and each grade upward from fluvial or inner estuarine sandstones into estuarine mudstones and in turn into shoreface sandstones the lateral and vertical stacking patterns of the lithofacies are complex however and the upper cycles appear to fill space eroded into the underlying ones northeast southwest elongate isochore trends appear in all three cycles lithofacies transition downdip from inner estuarine sandstones in the northeast to estuarine basin mudstones and shoreface sandstones toward the southwest detrital mineralogy indicates an easterly cratonic provenance for the entire unit our data suggest that the j sandstone in northwestern nebraska accumulated in wave dominated estuarine settings as part of a long lived transgressive systems tract the unit as a whole occupies a complexly incised landscape cut during a third order lowstand ca 98 ma coeval cycles of similar magnitude throughout the western interior suggest that the three cycles represent eustatic fluctuations the highest quality reservoirs occur at the base of the unit in inner estuarine lithofacies in the central and southwestern parts of the study area

global correlation of cenomanian upper cretaceous sequences evidence for milankovitch control on sea level we have investigated the sequence stratigraphy of two widely separated marine cenomanian successions in southeast india and northwest europe and used high resolution ammonite biostratigraphy to demonstrate that sea level changes are globally synchronous and therefore must be eustatically controlled sequence scale sea level changes in the cenomanian were driven by the long eccentricity cycle 400 k y in the milankovitch band we hypothesize that during pre quaternary time the third order sequences of vail and haq are essentially a sediment response to sea level changes driven by the 400 k y cycle construction of a relative sea level curve for the marginal marine succession in india demonstrates that the short term sea level changes are rapid 10 100 m m y and have a magnitude of 2 20 m glacioeustasy is a possible but unproven driving mechanism

stable isotope composition of bulk and secondary carbonates from the quaternary loess paleosol sequence in suttő hungary abstract stable carbon and oxygen isotope composition of pedogenic carbonates were studied from the quaternary loess paleosol sequence of sutt in hungary to investigate genetic processes in a paleoenvironmental context and to distinguish subtypes bulk carbonate samples taken at 2 cm vertical resolution and microscale secondary authigenic carbonates calcified root cells carbonate coatings hypocoatings and earthworm biospheroids and concretions at 10 cm resolution were analysed to interpret stable isotope variations isotope values of bulk samples were in the range of 2 6 to 13 9 and 2 3 to 17 0 vs vpdb for 13c and 18o respectively the isotope compositions of secondary carbonates clearly distinguished between the organically related and inorganic direct precipitation of the different subtypes in general secondary carbonates showed more depleted values than bulk samples calcified root cells have the most depleted isotope composition with mean values of 16 0 and 11 8 for 13c and 18o respectively results indicate that loess and paleosol secondary carbonates reveal pedogenetic information during the different climatic phases carbon and oxygen isotope analyses are valuable to classify secondary carbonates and to serve as proxies for the interpretation of paleoenvironmental conditions e g moisture conditions leaching the role of organic matter or vegetation secondary carbonates are more reliable than bulk samples because of their direct connection to the host strata

reconstructing the response of c3 and c4 plants to decadal scale climate change during the late pleistocene in southern illinois using isotopic analyses of calcified rootlets abstract the 13c and 18o values of well preserved carbonate rhizoliths crs provide detailed insights into changes in the abundance of c3 and c4 plants in response to approximately decadal scale changes in growing season climate we performed stable isotope analyses on 35 40 crs sampled at 1 cm intervals from an 18 cm thick paleosol formed in southern illinois during wisconsin interstadial 2 minimum 13c values show little variation with depth whereas maximum values vary dramatically and average values show noticeable variability maximum 18o values vary less than the minimum 18o values these findings indicate that a diverse and stable c3 flora with a limited number of c4 grass species prevailed during this interval and suggest that the maximum growing season temperatures were relatively stable but minimum growing season temperatures varied considerably two general patterns characterize the relationships between the 13c and 18o values obtained from the 1 cm samples in some cases low 13c values correspond to low 18o values and high 13c values correspond to high 18o values suggesting that cooler growing season temperatures favored c3 and warmer growing season temperatures favored c4 plants in other cases low 13c values correspond to high 18o values likely suggesting that wetter growing season conditions were favorable to c3 plants the high density of well preserved crs in this paleosol provides a unique opportunity to study detailed ecological responses to high resolution variability in growing season climate

reservoir geology of nicholas and liverpool cemetery fields lower pennsylvanian stanton county kansas and their significance to the regional interpretation of the morrow formation incised valley fill systems in eastern colorado and western kansas reservoirs in the lower pennsylvanian morrow formation of eastern colorado southwestern kansas and northwestern oklahoma have produced greater than 8 tcf of gas and 200 million bbl of oil this prolific depositional system produces from reservoirs representing a range of depositional environments from updip fluvial dominated incised valley fills to deep water basin floor systems the valley fills of the morrow formation are of particular significance because they can be mapped in great detail from subsurface control over very long distances facies distributions in the valleys change systematically downdip as a result reservoir characteristics and trapping mechanisms vary with these changes in internal valley stratigraphy this paper focuses on the reservoir geology of nicholas and liverpool cemetery fields these fields produce gas from the extreme downdip region of an incised valley fill system in the lower morrow formation the valley systems in this downdip region are deeper and wider and demonstrate greater marine influence than the updip regions of the valley systems farther north and into the hinterland compartmentalization in these downdip reservoirs differs significantly from updip valley fill reservoirs the reservoirs in this downdip region are more highly compartmentalized because the dominant reservoir facies in these fields is a series of bayfill delta deposits these deposits are isolated by shale deposits in the valley this depositional setting contrasts markedly with predominantly fluvial reservoirs in updip regions of the valleys understanding the scale geometry and internal complexity of this depositional system is important because the associated sandstones are important gas reservoirs in southwest kansas cores wire line logs pressure data and production data collected from the morrow formation at nicholas and liverpool cemetery fields provide valuable information from which to describe and interpret this downdip valley fill this paper describes the downdip incised valley fill reservoirs in this producing complex and documents the trapping relationships of these reservoirs and their production characteristics