fire ecology of the carboniferous tropical zone abstract fossil charcoal fusain indicating the occurrence of wildfire is common in the carboniferous rocks of north america and europe during the carboniferous these regions lay on the southern margins of the laurasian continent and within the tropical zone this study examines the facies distribution and botanical identity of charcoal in order to investigate the influence of fire on carboniferous tropical ecology new data from charcoal bearing units in eastern canada poland and the british isles are presented and synthesised with previously published data of charcoal occurrence tournaisian visean charcoal bearing strata were deposited in volcanic lacustrine alluvial plain and coastal marine environments in these deposits charred floras are dominated by pro gymnospermous plants whilst uncharred compressed or permineralised floras are dominated by lycopsids uncharred lycopsid remains were probably derived from wetland communities growing close to the depocentres whilst charred gymnospermous remains may have been sourced from well drained extrabasinal settings based on the vertical distribution of charcoal layers in annually laminated lacustrine deposits it is estimated that fires occurred with high frequency approximately every 3 35 years palaeoclimatic analysis indicates that southern laurasia at this time was subject to a seasonal monsoonal tropical climate such environments today are characterised by tropical savannas with high fire frequencies and early carboniferous fire prone gymnospermous plant communities may have represented a comparable vegetation biome namurian stephanian charcoal bearing strata were deposited in alluvial plain coastal plain and coastal marine environments channelised sandstone units interpreted as river channel deposits contain charcoal derived from cordaitaleans and conifers this assemblage records fires in extrabasinal coniferopsid forests mudstone units containing coals are interpreted as the deposits of floodbasins and peat mires hollow uncharred lepidodendrid stumps occur in this facies and contain lepidodendrid charcoal in the stump bases and lepidodendrid pteridosperm coniferopsid and sphenopsid charcoal outside the stumps this assemblage records fires in wetland lepidodendrid dominated forests lepidodendrid trunks comprising of a spongy parenchymatous core surrounded by dense periderm became hollowed out during fire events an estimate of fire frequency based on the vertical spacing of charcoal layers in coals implies that fires occurred every 105 1085 years in the peat mires palaeoclimatic analysis indicates that southern laurasia was subject to a humid tropical climate during the late carboniferous such environments today are characterised by tropical rainforests where fires occur rarely and late carboniferous communities may have represented a comparable biome

the early carboniferous courceyan arundian monsoonal climate of the british isles evidence from growth rings in fossil woods the british isles lay at a palaeolatitude of 4 s during the early carboniferous courceyan arundian period this paper examines fossil gymnosperm wood from ten localities in western ireland and southern scotland in order to analyse palaeoclimate fifty two percent of the 77 fossil wood specimens studied exhibit growth rings that possess subtle discontinuous ring boundaries and ring increments of narrow but variable width these growth rings are qualitatively and quantitatively analysed and are shown to bear a close similarity to growth rings in modern araucarian conifer woods these araucarian growth rings are formed in response to tropical rainfall seasonality linked to monsoonal circulation the findings of this study therefore support earlier palaeoclimatic interpretations based on sedimentological evidence which suggest that the british isles experienced a monsoonal climate during the early carboniferous courceyan arundian period

onset of late palaeozoic glacio eustasy and the evolving climates of low latitude areas a synthesis of current understanding studies of depth sensitive carbonate successions in the uk indicate that regular orbitally forced glacio eustatic sea level oscillations which characterized the late palaeozoic started abruptly around 330 ma early asbian the gondwanan ice sheet was highly sensitive to orbitally forced variations in solar insolation and the resultant sea level oscillations had an approximate 100 ka periodicity studies of fossil soils and palaeokarst from low latitude settings suggest that pre asbian climates were relatively stable with infrequent changes however climatic changes became increasingly frequent in the asbian and brigantian with regular fluctuations of a sub 100 ka periodicity occurring during glacial lowstand intervals

calcrete palaeosols from the lower carboniferous llanelly formation south wales abstract three calcrete bearing palaeosol units are described from the lower carboniferous llanelly formation in south wales and are named the tyle r bont pedocomplex the cwm dyar pedoderm and the llanelly pedocomplex these units were formed on semi arid to arid floodplains and are associated with sheet flood stream flood and meandering channel deposits three major processes operated during pedogenesis calcification pedoturbation and solution pedoturbation resulted in the formation of brecciated horizons pseudo anticlinal and prismatic structures and a predominance of disorthic nodules the soils developed in smectite rich clays under a seasonally arid climate resulting in strong argillipedoturbation

heterogeneity cyclicity and diagenesis in a mississippian brachiopod shell of palaeoequatorial britain a shell of gigantoproductus okensis shows twenty growth lines with marked changes of fabric indicating periodical reduction of growth rates caused by environmental perturbations the number of growth lines suggests a lifespan of 20 years in agreement with the survival rates of extant brachiopods and with spiral deviation analysis geochemical analyses across the growth profile show a heterogeneous distribution of stable isotopes and trace elements it is possible to distinguish primary from altered carbonate and to interpret the isotopic data the oxygen isotope signal in the unaltered parts is periodical and annual with oscillation of 1 1 the higher values are at the growth lines winter and therefore most likely related to monsoon circulation during the visean the annual periodicity seems also present in the altered part of the shell suggesting that diagenesis could have reset the primary values but preserved their cyclicity

ferrolysis in arundian alluvial palaeosols evidence of a shift in the early carboniferous monsoonal system an unusual clay mineral assemblage from early carboniferous arundian palaeosols in south wales contains a three component kaolinite chlorite like material smectite mixed layer clay this is interpreted as the product of ferrolysis a complex process involving dissolution of clays a d the subsequent production of interlayered varieties from the repetitive reduction and reoxidation of iron compounds in seasonally waterlogged surface water grey soils support for this interpretation comes from the distribution of iron species iron concretions and vertic features in the palaeosol profile which indicate formation under strongly seasonal dry hydromorphic conditions the appearance of the ferrolytic pa iaeosol indicates a shi from a dry to a wet type monsoonal regime in late arundian times

seismic signals from tsunamis in the pacific ocean 1 we examine seismic signals from tsunamis for 14 earthquakes of mw 7 1 to 8 4 in the circum pacific region that generated tsunamis measured previously from tide gauges or coastal runup low frequency signals of 0 5 mhz up to 2 8 mhz are observed at the expected tsunami arrival time on the horizontal components of low elevation seismic stations near coastlines for eight of the 14 earthquakes lower amplitude signals are observed for the other six for two earthquakes mw 8 2 8 4 we observe a dispersed tsunami signal between 1 and 8 mhz with lower frequencies arriving earlier this dispersion is consistent with predictions from the standard model for gravity waves for the bathymetry along these source station paths these observations along with earlier observations from the indian ocean suggest that seismic data could be used to complement tide gauges and ocean bottom pressure recorders to indicate the arrival of a tsunami

equatorial aridity and climatic oscillations during the early carboniferous southern britain evidence from palaeosols palaeokarsts and styles of meteoric diagenesis shows that the early carboniferous climate of southern britain was dominantly seasonally semi arid this semi aridity occurred while the region was in an equatorial palaeolatitudinal position the cause of the seasonal aridity was possibly the deflection of easterly winds into a major low pressure zone set up over gondwana during the southern hemisphere summer

early dinantian evaporites of the easton 1 well solway basin onshore cumbria england abstract an early visean anhydrite rich carbonate clastic succession of vertical thickness 3784 feet no base was found in 1990 at the easton 1 well in the solway basin onshore cumbria the succession is stratigraphically located in the lower border group where only traces of evaporites had been found at outcrop it is proposed to name the succession the easton anhydrite facies of the lower border group abbreviated to ea beds the ea beds are divided into three units unit 1 at the top about 400 feet thick contains two sequences of upwardly thickening anhydrite beds within mixed lithologies unit 2 about 2100 feet thick consists of nine cyclic sequences of limestones shales and sandstones with numerous interbeds of anhydrite overall similarity of several of the sequences suggests similar origins unit 2 sequences are grouped into three megacycles two of approximately 750 feet and one 590 feet thick deposition is interpreted to have taken place in arid or partly arid climatic conditions within a shallow and rapidly but uniformly subsiding basin with glacio eustatically controlled rise and fall of sea level many of the unit 2 anhydrite beds are interpreted to be of subaqueous origin unit 3 about 1500 feet thick displays complex patterns of cyclicity with sedimentation apparently responding directly to solar insolation under orbitally induced control within milankovitch periodicities of 100 000 and 400 000 years seismic interpretation indicates that the regional extent of the ea beds is greater than 1000 km 2

a rendzina from the lower carboniferous of south wales a thin calcrete crust horizon from the lower carboniferous llanelly formation of south wales consists of two parts an upper laminated unit and a lower peloidal unit the former is interpreted as a subaerial stromatolite and the latter as an a horizon of a palaeosol comparisons are made with the a horizons of rendzinas and it is concluded that the calcrete crust represents a complete rendzina profile this fossil rendzina contains abundant evidence of a soil fauna in the form of fecal pellets and small burrows

early mississippian lycopsid forests in a delta plain setting at norton near sussex new brunswick canada mississippian lycopsid forests in growth position are extremely rare and their community scale ecology remains enigmatic this is a significant gap in our knowledge not least because they represent the precursors of pennsylvanian coal forests in this paper nearly 700 in situ fossil trees are described from 13 entisol or inceptisol horizons in the mid tournaisian albert formation horton group at norton near sussex new brunswick canada these trees almost all of which are lycopsids of the protostigmaria lepidodendropsis type are rooted mostly in the flood disturbed interdistributary wetland deposits of prograding wave dominated deltas tree mapping on extensive palaeosol surfaces indicates the existence of extremely dense forest vegetation scaled up to standard forestry units densities of 10 000 30 000 trees per hectare are inferred a significant inverse linear relationship between tree diameter and density for the five most extensive palaeosols indicates that inter tree competition led to natural self thinning as the forests matured forest maturation also led to a reduction in tree spacing heterogeneity flood events regularly killed whole stands at norton burying trees in sandstone sheets and preventing establishment of climax vegetation charcoal remains demonstrate that wildfire was another important disturbance process

detrital zircons reveal evidence of hadean crust in the singhbhum craton india a reply abstractthe singhbhum craton is one of five archean cratons constituting the indian subcontinent it consists of four major lithotectonic units with broadly defined ages from eoarchean to neoarchea

early mississippian evaporites of coastal tropical wetlands extensive evaporites in lower mississippian successions from palaeoequatorial regions are commonly used as evidence for an arid to semi arid palaeoclimate however in this study detailed studies of evaporites and their context refute this interpretation detailed sedimentological and petrographical analysis of the lower mississippian of northern britain is combined with archived log data from more than 40 boreholes across southern scotland northern england and northern ireland and published literature from canada two key cores from the tweed basin and the northern margin of the northumberland solway basin contain 178 evaporite intervals and reveal twelve distinct forms of gypsum and anhydrite across seven facies that are associated with planar laminated siltstone and intercalated thin beds of ferroan dolostone nodular gypsum and anhydrite typically in intervals less than 1 to 2 m thick are integral components of the succession nodular evaporite occurs within about 1 m of a palaeosurface but most evaporite deposits represent ephemeral brine pans to semi permanent hypersaline lakes or salinas on a floodplain that was subjected periodically to storm surges introducing marine waters formation of evaporites under a strongly seasonal climate in a coastal wetland is supported by palaeosol types and geochemical proxies and from palaeobotanical evidence published previously although 65 of modern equatorial areas experience a strongly seasonal climatic regime salinas and sabkhas are a minor component today in comparison with the evidence from these lower mississippian successions this implies that the earliest terrestrial environments were complex and dynamic providing a diverse range of habitats in which the early tetrapods became terrestrialized and represent a setting that is rarely preserved in the geological record

carbon and oxygen isotopic signatures in albian danian limestones of cauvery basin southeastern india abstract the albian danian limestones of cauvery basin show a wide range of d13c and d18o values 13 2 to 1 1 and 9 0 to 2 5 respectively the cement samples show negative carbon and oxygen isotope values 18 9 to 3 9 and 9 0 to 4 3 respectively the petrographic study reveals the presence of algae molluscs bryozoans foraminifers and ostracods as major framework constituents the limestones have microspar and equant sparry calcite cements the pore spaces and vugs are filled with sparry calcite cement the bivariate plot of d13c and d18o suggests that most of the samples fall in the freshwater limestone and meteoric field while few samples fall in the marine limestone and soil calcite fields the presence of sparry calcite cement together with negative carbon and oxygen isotope values indicates that these limestones have undergone meteoric diagenesis

early carboniferous floodplain deposits from south wales a case study of the controls on palaeosol development two palaeosol sequences are described from early carboniferous floodplain deposits from south wales which exhibit a complex series of pedogenic profiles soil types recognized include vertic aridisols and entisols as well as dolomite bearing sulphaquents the sequential and lateral changes in these soil types are interpreted as due to both intrinsic factors such as channel avulsion and changing proximity to channel belts causing changes in sedimentation rates and extrinsic factors such as possible climatic changes and a marine transgression

distribution of diagenetic alterations in fluvial deltaic and shallow marine sandstones within a sequence stratigraphic framework evidence from the mullaghmore formation carboniferous nw ireland abstract the distribution of diagenetic alterations in the fluvial deltaic and shallow marine arkosic to subarkosic sandstones average q72f26l02 of the mullaghmore formation carboniferous nw ireland can be predicted within a sequence stratigraphic framework eogenetic calcite 18opdb 13 3 to 6 5 13cpdb 3 0 to 3 4 and 87sr 86sr 0 706721 to 0 709227 and ferron dolomite feco3 8 12 mol 18opdb 14 2 to 7 8 13cpdb 1 4 to 1 0 and 87sr 86sr 0 709051 to 0 709167 occur in bioclast rich transgressive lag deposits at parasequence boundaries and transgressive surfaces and in wave influenced deltaic highstand systems tract hst deposits mesogenetic illite chlorite baroque dolomite feco3 16 mol 18opdb 14 2 to 12 7 13cpdb 3 8 to 1 0 quartz and calcite 18opdb 15 7 to 12 5 13cpdb 5 8 to 3 7 and 87sr 86sr 0 709016 to 0 709122 were formed mainly in the bioclast poor deposits which were not pervasively cemented by carbonates during near surface eodiagenesis these deposits include fluvial incised valley sandstones of lowstand systems tract lst and fluvial dominated deltaic sandstones of transgressive systems tract tst and hst illite is the dominant diagenetic clay mineral in the fluvial incised valley sandstones of lst possibly because of simultaneous albitization of k feldspars conversely chlorite dominates in the fluvial dominated deltaic sandstones of tst and hst because of the presence of suitable precursor clays the integration of diagenesis into sequence stratigraphic framework of clastic sequences should improve the ability to predict the spatial and temporal distribution of diagenetic alterations and related reservoir quality modifications of sandstone deposits

contrasting diagenesis of two carboniferous oolites from south wales a tale of climatic influence two oolites in the dinantian mississippian lower carboniferous of glamorgan sw britain were deposited in similar depositional environments but have contrasting diagenetic histories the brofiscin and gully oolites occur in the upper parts of shallowing upward sequences formed through strandplain progradation and sand shoal and barrier growth upon a southward dipping carbonate ramp the brofiscin oolite is characterized by a first generation cement of equant calcite spar preferentially located at grain contacts and forming non isopachous fringes around grains interpreted as meteoric vadose and phreatic in origin isopachous fibrous calcite fringes of marine origin are rather rare and occur only at a few horizons burial compaction was not important and porosity was occluded by poikilotopic calcite spar fitted grain grain contacts locally occur and could be the result of near surface vadose dissolution compaction syntaxial overgrowths on echinoderm debris are common pre compaction overgrowths are cloudy inclusion rich and probably of meteoric origin and post compaction overgrowths are inclusion free by contrast the gully oolite has little first generation cement however marine fibrous calcite is common in oolitic intraclasts as isopachous fringes of acicular calcite crystals closely associated with peloidal internal sediment and early equant drusy calcite spar occurs in the uppermost part of the gully beneath a prominent palaeokarst where pedogenic cements also occur the major feature of gully diagenesis is burial compaction resulting in extensive grain grain dissolution and microstylolitic grain contacts and post compaction poikilotopic spar occluded remaining porosity the brofiscin oolite is pervasively dolomitized up dip but the gully oolite for the most part only contains scattered pre compaction dolomite rhombs and late veins of baroque dolomite with less pervasive dolomitization the difference in diagenetic style of the two dinantian oolites is attributed to prevailing climate the paucity of early meteoric cements in the gully is a result of an arid climate and this is supported by the nature of the capping palaeokarst the abundant meteoric cements in the brofiscin reflect a more humid climate and effective meteoric recharge also resulted in up dip pervasive mixing zone dolomitization the style of early diagenesis in these two oolites exerted a major control on the later burial diagenesis in the brofiscin the early cements inhibited grain grain dissolution and pressure solution while these processes operated extensively in the gully oolite thus prevailing climate can influence a limestone s diagenetic history from near surface through into deep burial

the recognition and interpretation of paleokarsts two examples from the lower carboniferous of south wales abstract criteria for the identification and interpretation of paleokarstic surfaces in ancient carbonate sequences are discussed and two examples of such surfaces are described from the lower carboniferous of south wales one type is compared to kavornossen karren a type of tropical karst well developed today on puerto rico the second example a mammillated paleokarstic surface of a type common in the lower carboniferous is interpreted as a deckenkarren formed beneath a vegetation cover and similar to the makondo karsts of south africa paleokarsts can provide information on the paleoclimates paleohydrology and vegetation cover existing at the time of their formation

stable isotopic composition of meteoric calcites evidence for early mississippian climate change in the mission canyon formation montana abstract the lower mississippian mission canyon formation of central to southwestern montana was deposited under dominantly semiarid to arid climatic conditions during osagean to early meramecian times following deposition a pronounced climatic shift to more humid conditions occurred during middle meramecian times this climatic change is indicated by extensive post depositional karst fabrics and in the stable isotopic composition of early meteoric calcite cements and diagenetically altered sediments early meteoric calcite cement in mission canyon limestones is generally nonluminescent and fills intergranular and fenestral porosity petrographic data indicate that this cement formed during intermittent subaerial exposure of the mission canyon platform during osagean times this initial generation of meteoric calcite cement has 18o values from 8 1 to 2 6 pdb these data and the oxygen isotopic values from nonluminescent skeletal grains and micrite in host limestone indicate that osagean meteoric water may have had 18o values as low as 6 0 smow a second generation of petrographicalty similar but isotopically distinct calcite cement fills biomolds and porosity within solution collapse breccias in the mission canyon formation this cement generation postdates earlier nonluminescent osagean calcite cement and is volumetrically most abundant near the top of the mission canyon formation 18o values from these cements and from nonluminescent lime mudstone clasts and matrix in solution collapse breccias range from 13 8 to 8 2 pdb these data indicate that meramecian meteoric water may have had 18o values as low as 12 0 however a higher temperature burial overprint on the 18o values of the calcite cement cannot he ruled out the more positive 18o values of the osagean calcite components probably indicate warm and arid conditions during short term 104 yr subaerial exposure along intraformational sequence and parasequence boundaries the more negative 18o values from meramecian calcite components and the extensive karst associated with the post mission canyon unconformity may have developed because of cooler and more humid climatic conditions and possible rain out effects during middle meramecian times a dramatic shift towards cooler and more humid climatic conditions may be coincident with the onset of major continental glaciation in the early carboniferous the post mission canyon unconformity has been attributed to a major fall in sea level that may have glacio eustatic origins growth of continental glaciers during a time of global cooling would have caused migration of polar fronts further toward the paleoequator these polar fronts in turn would have pushed moist mid latitude weather systems toward the paleoequator resulting in cooler more humid conditions in low latitude settings during icehouse times

the terrestrial landscapes of tetrapod evolution in earliest carboniferous seasonal wetlands of se scotland abstract the lower mississippian tournaisian ballagan formation in se scotland yields tetrapod fossils that provide fresh insights into the critical period when these animals first moved onto land the key to understanding the palaeoenvironments where they lived is a detailed analysis of the sedimentary architecture of this formation one of the thickest and most completely documented examples of a coastal floodplain and marginal marine succession from this important transitional time anywhere in the world palaeosols are abundant providing a unique insight into the early carboniferous habitats and climate more than 200 separate palaeosols are described from three sections through the formation the palaeosols range in thickness from 0 02 to 1 85 m and are diverse most are entisols and inceptisols 63 indicating relatively brief periods of soil development gleyed inseptisols and vertisols are less common 37 vertisols are the thickest palaeosols up to 185 cm in the ballagan formation and have common vertic cracks roots are abundant through all the palaeosols from shallow mats and thin hair like traces to sporadic thicker root traces typical of arborescent lycopods geochemical isotope and clay mineralogical analyses of the palaeosols indicate a range in soil alkalinity and amount of water logging estimates of mean annual rainfall from palaeosol compositions are 1000 1500 mm per year the high mean annual rainfall and variable soil alkalinities contrast markedly with dry periods that developed deep penetrating cracks and evaporite deposits it is concluded that during the early carboniferous this region experienced a sharply contrasting seasonal climate and that the floodplain hosted a mosaic of closely juxtaposed but distinct habitats in which the tetrapods lived the diversification of coastal floodplain environments identified here may link to the evolution and movement of tetrapods into the terrestrial realm

facies sequences on a carbonate ramp the carboniferous limestone of south wales during early carboniferous times a major sea level rise led to the development of an extensive carbonate ramp over what is now south wales differential subsidence and sea level changes resulted in distinctive facies sequences in the ramp succession and a model is offered which recognizes three distinct geomorpho tectonic settings inner mid and outer ramp the inner ramp zone occurs in the more landward part of the province and was an area undergoing little or no subsidence the sequence is dominated by oolitic grainstones and peritidal limestones representing shoal and back shoal environments the peritidal units are transgressive deposits consisting of stacked asymmetrical shallowing up cycles the sequence contains many subaerial breaks and tectonic uplift resulted in base level changes and fluvial incision the mid ramp zone sequence is intermediate in thickness between the inner and outer ramp successions and consists mainly of bioclastic limestones deposited below fairweather wave base sedimentation periodically exceeded sea level rise and subsidence and regressive progradational oolitic sand bodies developed the thickest of which are stacked units with up to four individual sand bodies storm processes were of major importance in this setting the outer ramp zone is represented by a thick sequence of muddy bioclastic limestones deposited below storm wave base and major waulsortian reef mounds also developed none of the shallowing phases seen in the other ramp zones can be detected in this sequence subsidence and eustatic sea level rise seem to have been the major controls on deposition but the recognition of eustatic sea level falls is difficult the detailed facies model for ramp carbonates presented here may be applicable elsewhere in the geological record

stable isotopic composition of paleosols in the lower visean of eastern belgium evidence of evaporation and soil gas co2 abstract numerous paleosols occur in the lower visean peritidal limestones of eastern belgium at the top of the peritidal unit a widespread paleosol horizon occurs which has been analysed for its carbon and oxygen isotopic composition in spite of the paleozoic age of the pedogenic carbonates the influence of evaporation and soil gas co 2 on the stable isotopic composition of the paleosol is very pronounced this has been assinged to the long exposure time in a semi arid seasonal climate evaporation caused an enrichment in 18 o in the paleosol compared with the over and underlying limestones which were cemented and mineralogically stabilized in meteoric pore waters the influence of soil gas co 2 in the soil formation is clearly indicated by the depletion in 13 c of the pedogenic carbonates 13 c 5 pdb compared with the carbon isotopic composition of lower visean marine limestones 13 c 4 pdb the possible effect of carbon derived from atmospheric co 2 on the 13 c values of the paleosols is discussed

paleosols and tidal flat lagoon sequences on a carboniferous carbonate shelf sedimentary associations of triple disconformities abstract carbonate shelf sequences in the lower carboniferous of southwest britain contain thin peritidal intercalations within open shelf facies analysis of one such unit the caswell bay mudstone at miskin south wales shows it to contain a lower paleosol and an upper tidal flat lagoon sequence these are separated and bounded by erosion surfaces directly related to the origin of the units they underlie the complete sequence using letters for rock units and numbers for disconformities with interpretation in brackets is a oolite inner shelf shoal 1 irregular disconformity subaerial subsoil surface b oolite breccia conglomerate in clay matrix regolith with clay introduced as windblown or overbank material c mottled micrites calcrete 2 planar disconformity back barrie shoreface d peloid micrites e laminated micrites f paper shales and thin limestones all shallow subtidal lagoon low intertidal flat sediments 3 planar disconformity barrier shoreface g bioclastic limestone inner shelf open marine sands and gravels units b f total 6 m thickness and constitute the caswell bay mudstone they comprise a couplet of terrestrial and back barrier sediments preserved during a transgression probably because of the resistance of the calcrete and a moderate subsidence rate breaks 1 3 represent a subaerial surface plus two barrier associated erosion surfaces these three breaks are here termed a triple disconformity the subaerial surface is the major break of the three and the back barrier shorezone surface marks the base of the transgressive sequence the uppermost break the barrier shoreface is a relatively minor intra sequential erosion plane recognition of this sequence of deposition and erosional events clarifies the origin of the units involved provides an environmental framework for further biofacies and lithofacies analysis and indicates the relative significance of breaks that may be used for stratigraphic subdivision paleosol tidal flat lagoon couplets and triple disconformities should be widespread features of transgressive barrier island carbonate shoreline sequences

climatic change during the lower carboniferous in euramerica based on multivariate statistical analysis of palynological data abstract lower carboniferous palynological assemblages show marked differences between north and south euramerica in order to assess these regional differences multivariate statistical analysis has been applied to percentage frequency data from palynological assemblages from twenty different localities of euramerica the principal components resulting have been related to climate sensitive rocks such as coal and evaporites this relationship has been interpreted in terms of humidity curves and climatic zones four climatic zones have been recognized a dry a moderately humid and a humid zone the latter zone may be subdivided into a humid and a very humid zone during the lower carboniferous the humid climatic zone and the related palaeoclimatic equator shifts southwards however the very humid conditions present in the uppermost tournaisian to middle visean of spitsbergen have not yet been reached in the lower namurian of western europe and the u s a the southward shift of the palaeoclimatic equator has been interpreted in terms of a northward drift of the euramerican continent the palaeomagnetic evidence available for this northward drift is briefly discussed

tropical marine climate during the late paleozoic ice age using trace element analyses of brachiopods abstract the late paleozoic ice age can be considered an important analogue to the modern ice age but comparisons between the two time intervals have been hampered by the difficulty of resolving climatic changes that occur over short e g seasonal time scales in the paleozoic record as a first step toward overcoming these limitations this study employed mg ca trace element ratios sampled across the growth bands of six specimens of the brachiopod composita to assess differences in tropical marine mean temperature and seasonality in visean and moscovian time these time intervals bracket the onset of the late paleozoic ice age which occurred in mid serpukhovian time and thus provide a snapshot of climate changes from a greenhouse to an icehouse world shells were screened for diagenetic alteration by cathode luminescence and by comparing the values of mn sr na and b to those reported for modern brachiopods in addition a 87sr 86sr value measured for one specimen agreed with a published strontium isotope curve for the late paleozoic era both the mean and range of mg ca values were larger in visean than moscovian time suggesting colder and less seasonal temperatures during the late paleozoic ice age the decline in seasonality was due to a greater proportional reduction of maximum values which presumably represent summer temperatures than minimum values these relative differences between the pre ice age and ice age tropical climate provide a first step toward understanding the broad patterns of seasonal scale changes in temperature during a critical time in earth s history