calcretes at sequence boundaries in upper carboniferous cyclothems of the sydney basin atlantic canada abstract nodular and associated groundwater calcretes in coal bearing cyclothems of the sydney basin mark the boundary between underlying marginal marine and overlying alluvial deposits they are inferred to represent lowstand surfaces sequence boundaries the host sediments include both sand siltstones and palustrine limestones microfabrics of calcretes with detrital hosts show evidence of replacement displacement and shrinkage alpha fabrics suggesting that the calcretes formed under relatively arid conditions in contrast microfabrics of nodular calcretes with limestone hosts exhibit predominantly beta fabrics with root induced brecciation and subordinate shrinkage fabrics the calcretes and host limestones are inferred to have formed in topographic lows thick alluvial sediments with red calcic vertisols overlie the calcretes and formed within the transgressive systems tract under conditions of abundant sediment supply coals and associated hydromorphic palaeosols lie near the transgressive maximum and in the highstand systems tract the presence of calcareous palaeosols on lowstand surfaces suggests that the lowstands were times of relative climatic aridity

a physical mechanism for temporal variation in seismicity in southwest japan related to the great interplate earthquakes along the nankai trough abstract a significant correlation has been reported between the intraplate inland and the great interplate earthquakes in southwest japan based on historical earthquake data since 868 the frequency of intraplate earthquakes is high for several decades before and up to a decade after great interplate earthquakes to explain the correlation we treated two types of interaction between the inland faults and the plate boundary a in which the stress changes caused by great interplate earthquakes affect the occurrence of intraplate earthquakes and b in which the stress changes caused by intraplate earthquakes trigger other intraplate earthquakes and great interplate earthquakes to simulate the sequences of these earthquakes we calculated the static stress changes resulting from large intraplate and great interplate earthquakes and also estimate the rate of increase in tectonic stress on the faults and the plate boundary the estimated rates of increase here are smaller than those used in previous studies thus in our models stress changes could more strongly affect the seismicity than previously considered we simulated the earthquake sequences for our models in four cases i with no interaction among the inland faults in southwest japan and the plate boundary along the nankai trough ii with stress changes on the inland faults caused only by great interplate earthquakes iii with stress changes on the plate boundary caused only by large intraplate earthquakes and iv with stress changes both on the inland faults and on the plate boundary caused by large intraplate earthquakes the simulated time series in case i of course shows no correlation between intraplate and great interplate earthquakes those in cases iii and iv also show no significant correlation only the time series of intraplate earthquakes in case ii shows a temporal variation similar to that of the real intraplate earthquakes before and after the great interplate earthquakes we examined statistically the similarity between the simulated time series and the real earthquake data about 40 of the time series in case ii are significantly similar although in the other three cases less than 5 of the time series are understanding of the effects of stress changes on the inland faults caused by the great interplate earthquakes along the nankai trough is essential to explain the temporal variation in seismicity in southwest japan before and after the great interplate earthquakes

latest mid pennsylvanian tree fern forests in retrograding coastal plain deposits sydney mines formation nova scotia canada a latest mid pennsylvanian early cantabrian tree fern forest is reported from cape breton island nova scotia the fossil forest is rooted below the point aconi coal seam of the sydney mines formation at cranberry head the tree ferns are preserved in the deposits of a coastal plain subject to brackish incursions they were constructed of psaronid type trunks and massive pecopterid fronds and locally intergrew with sigillarian lycopsids neuropterid pteridosperms and calamiteans basal stump diameter measurements including the root mantle range from 12 to 89 cm indicating that the ferns were mostly large forest trees rather than shrubs stump distribution measurements on palaeosols indicate that localized patches of tree fern dominated forest attained densities of c 3850 trees per hectare when scaled up to standard forestry units much denser than typical mid pennsylvanian lycopsid forests tree ferns dominantly grew in aggrading floodbasin settings and a few of the largest trees show evidence for post burial regeneration being approximately coeval with the late mid pennsylvanian extinction event which resulted in tree fern forests rising to dominate tropical lowlands for the first time the cranberry head fossil forests provide insight into community composition and structure during a critical phase of ecosystem reorganization

invertebrate trace fossils and agglutinated foraminifera as indicators of marine influence within the classic carboniferous section at joggins nova scotia canada the sea cliffs at joggins nova scotia are the most extensive and continuous carboniferous section in eastern north america although the section has been considered to have formed within a nonmarine depositional basin paleobiological information indicates that parts of the section were deposited in brackish water the occurrence of a trace fossil assemblage which includes cochlichnus kouphichnium and treptichnus is part of an assemblage of biogenic structures that apparently reflects paleodeposition within fluvial systems that may have experienced distal marine influences presence of agglutinated foraminifera characteristic of brackish water environments supports this interpretation this information provides new evidence of brackish water conditions at joggins such as those now being widely recognized in other carboniferous coal bearing sections

a depositional model for the mid westphalian a to late westphalian b coal measures of south wales mid westphalian a to late westphalian b sediments of the south wales coalfield comprise mainly lacustrine raised mire and flood deposits developed in an upper coastal plain environment occasional high sinuosity fine grained channel systems drained the subdued topography of the wales brabant massif to the north and east of the basin low sinuosity channels with lithic coarse grained fills drained a rising source to the south direct marine influence was restricted to a single marine band facies distributions were controlled by 1 local scale 10 2 10 3 m 2 autocyclic sedimentary processes 2 regional scale 10 km 2 synsedimentary fault activity and differential subsidence and 3 basin wide scale 10 2 km 2 response to changes in relative sea level base level changes are recorded by basin wide bivalve horizons up dip or landward extension of marine bands developed in lacustrine mudstones above basin wide coal seams peat accumulation was terminated by a water table rise related to base level rise following flooding re establishment of the clastic supply resulted in the gradual infilling of the basin wide lake to produce coarsening upwards cyclothems or parasequences a eustatic origin for parasequence development is supported by the development of identical facies associations and parasequences in coeval sediments from the pennine and midland valley coalfields

community heterogeneity of early pennsylvanian peat mires reconstructions of pennsylvanian coal swamps are some of the most common images of late paleozoic terrestrial ecosystems all reconstructions to date are based on data from either time averaged permineralized peats or single site collections an erect in situ early pennsylvanian forest preserved above the blue creek coal black warrior basin alabama was sampled in 17 localities over an area of 0 5 km 2 resulting in the first temporally and spatially constrained pennsylvanian mire data set this three tiered forest was heterogeneous lycopsid and calamitean trees composed the canopy and lepidodendrids lepidophloios and sigillarians grew together at most sites more juvenile than mature lycopsid biomass occurs in the forest floor litter indicating a mixed age multicohort canopy pteridophytes tree fern and pteridosperms seed fern dominated as understory shrubs whereas sphenophyllaleans pteridophytes and pteridosperms composed the ground cover and liana tier the proportion of canopy understory and ground cover biomass varied across the forest low proportions of ground cover and liana taxa existed where canopy fossils accounted for 60 of the litter there is a distinct spatial clustering of sites with more or less understory or ground cover where canopy contribution was 60 where canopy biomass was low 50 understory shrubs contributed more biomass indicative of light interception and or competition strategies sphenopteris pottsvillea a ubiquitous ground cover plant is abundant in all sites except one where pteridosperm creepers and lianas dominate the litter interpreted to indicate total suppression of other ground cover growth ecological wet dry gradients identified in other pennsylvanian swamps do not exist in the blue creek mire with the interpreted wettest lepidophloios driest sigillaria and intermediate lepidodendron sensu latu taxa coexisting in most assemblages

erosion study of new orleans levee materials subjected to plunging water during hurricane katrina overtopping water caused erosion and subsequent failure of several sections of i type flood walls in new orleans erosion stemmed from the kinetic energy of water falling from the top of the flood wall unlike the typical surface erosion caused by shear flow this study evaluated the effects of important parameters of levee soils fines content degree of compaction doc clay mineralogy and water content in relation to the erosion behavior of new orleans levees subjected to the plunging water in general test results showed that a higher fines content contributed to greater erosion resistance the trend became unclear when fines content exceeded 20 25 a higher degree of compaction did not necessarily contribute to greater erosion resistance underwater soaked soils showed much less erosion resistance than nonsoaked soils soils containing expansive clay minerals showed less erosion resistance than soils containing nonexpansive clay minerals

late paleozoic to cenozoic history of the offshore sydney basin atlantic canada the sydney basin covers a large offshore area south of newfoundland with a well exposed outcrop belt on cape breton island the geological history of the poorly known offshore area is interpreted using an industry seismic grid and lithoprobe line 86 5 tied to outcrops and two wells the mid devonian to upper carboniferous permian basin fill is 6 7 km thick and represents three extensional phases with intervening and succeeding compressive phases the mid devonian mcadams lake formation was deposited in a local half graben during early post acadian extension following deformation a suite of early carboniferous extensional basins filled mainly with horton group conglomerates developed on northeast trending and southeast dipping master faults some faults developed along acadian terrane boundaries the windsor group extends over the master faults to onlap basement as a result of thermal sag and visean eustatic rise mid carboniferous deformation linked to the alleghanian orogeny reactivated faults an

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

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

paleobotanical and paleoecological constraints on models of peat formation in the late carboniferous of euramerica abstract the dominant plants of the late carboniferous lowland tropics were taxonomically and structurally distinct from those of any later time periods dominance was distributed among lycopsids ferns sphenopsids pteridosperms and cordaites and each of these groups had distinctive and different ecological preferences and amplitudes peat forming habitats were dominated by lycopsids throughout the westphalian with a significant cordaitean element in the middle westphalian during the stephanian tree ferns were dominant following major extinctions near the westphalian stephanian transition each of the major plant groups had distinctive architectures and tissue composition trees contributed up to 95 of the peat biomass and tree forms of lycopsids psaronius and medullosa lack good modern analogues the cordaites were the only woody plant group to contribute significantly to peat and then only during the mid westphalian structurally wood like lycopsid bark is the major woody tissue encountered in most westphalian coals tree ferns and pteridosperms were largely parenchymatous in construction the stigmarian root systems of lycopsids also were largely parenchymatous the tissue structure of these dominant plant suggests the need for extreme caution in the inference of mire ecological conditions or vegetational structure from coal petrographic data peat formed under arborescent ferns or pteridosperms or peat repeatedly exposed to decay and rerooting by stigmarian root systems of lycopsids would have a distinctly non woody signature and yet would have formed in a forested environment a summary is presented of the autecology and synecology of mire plants emphazing the structural framework provided by lycopsids during the westphalian certain constraints in the links between peat biomass and miospore palynology are discussed in terms of over representation under representation and non representation the formulation of smith s four phase hydroseral model is discussed and compared with more recent data available from plant paleoecology the current debate over an ombrotrophic vs rheotrophic origin of late carboniferous peats relies in large part on paleobotanical data almost entirely palynological in combination with petrographic analyses ecological studies of miospores and of coal ball and compression macrofossils and the linkage of miospores to source plants permit the re evaluation of mire successional models evidence for tree lycopsids sphenopsids pteridosperms and cordaites suggests growth mainly in rheotrophic mires tree ferns are likely candidates for growth in domed mires although evidence is ambiguous and some tree ferns clearly grew under rheotrophic conditions densospores produced by at least sporangiostrobus lycopsid subtrees have been considered diagnostic of ombrotrophic conditions abundant evidence refutes this simplistic interpretation and suggests broad ecological amplitudes for densospore producers including growth under rheotrophic conditions although plant fossils alone can not resolve most of the major debates in modern coal geology paleobotany does contribute significantly to our understanding of ancient mires an approach combining paleobotanical data with petrography sedimentology and geochemistry on a case by case basis is most likely to produce a clear picture

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

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

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

the westphalian d fossil lepidodendrid forest at table head sydney basin nova scotia sedimentology paleoecology and floral response to changing edaphic conditions copyright c 1996 elsevier science b v all rights reserved strata of westphalian d age on the western coast of the sydney basin expose a fossil forest of approximately 30 lepidodendrid trees within one of several clastic splits of the harbour seam a mutidisciplinary approach was employed to interpret the origins of the coal bed the depositional history of the site and the response of the fossil forest to changing edaphic conditions the megaspore and miospore records indicate that the mire vegetation was dominated by arboreous lycopsids especially paralycopodites with subdominant tree ferns petrographic palynological and geochemical evidence suggest that the harbour coal bed at table head originated as a rheotrophic cf planarr mire eutric histosolr the mire forest is interpreted to have been engulfed by prograding distributary channel sediments sparse protist assemblages are suggestive of a freshwater delta plain lake environment occasionally in contact with brackish waters lepidodendrids persisted as site colonizers of clastic substrates even after burial of the rheotrophic peatland and influenced the morphology of deposited sediment but apparently were unable to colonize distributary channels equivocal taxonomic data compression fossilsr show the fossil forest to have been composed of both monocarpic lepidodendronr and polycarpic diaphorodendron paralycopodites sigillariar lycopsids genera recorded in the palynology of the uppermost ply of the underlying coal bed comparatively rare within the clastic beds of the fossil forest however is the stem compression of paralycopodites whose dispersed megapores and miospores dominate the underlying coal bed tree diameter data recorded equivalent to breast height indicate a forest of mixed age these data would appear to suggest that some lepidodendrids employing a polycarpic reproductive strategy were better able to cross the ecological barrier imposed between peat and clastic substrates foliar compressions indicate that an understory or stand of psaronius type tree ferns co existed with the lepidodendrids on clastic substrates which developed as incipient gleysol soils the entombment of the forest can be ascribed to its distributary coastal setting local subsidence and a seasonal climate that fostered wildfire and increased sedimentation

palaeovalleys and protozoan assemblages in a late carboniferous cyclothem sydney basin nova scotia the early stephanian bonar cyclothem of the sydney basin nova scotia contains an erosional surface cut through coastal plain strata with economic coals and distributary channel bodies the erosion surface is interpreted as a palaeovalley 20 m deep and at least 7 km wide that marks a sequence boundary formed during relative fall in sea level the palaeovalley is filled with stacked alluvial channel bodies which become more isolated as the valley fill passes upward into red alluvial plain deposits probably laid down in an anastomosed river system in an adjacent interfluve area calcretes and red vertic palaeosols cap coastal strata assemblage analysis of agglutinated foraminifera and thecamoebians indicates that the palaeovalley was filled with freshwater sediments before an initial marine transgression flooded the alluvial surface and adjacent interfluve valley incision probably reflects glacioeustatic sea level fall however the alluvial nature of the valley deposits suggests that valley filling reflects an abundant sediment supply during lowstand and or transgressive stages and was not a direct consequence of sea level rise during the subsequent transgression phase aggradation was rapid as sediment supply apparently kept pace with rising sea level features of both channel and extra channel facies suggest that seasonality intensified during the transition from coastal plain to palaeovalley and alluvial plain deposition

fluvial channel and overbank deposits from the westphalian of the durham coalfield ne england the westphalian upper carboniferous coal measures of the durham coalfield in ne england were deposited in lower and upper delta plain environments distributary channels crossed the plain and were separated by shallow interdistributary lakes and bays detailed observation of three dimensional 3 d opencast surface mine exposures in collaboration with subsurface borehole analysis has revealed the existence of five varieties of channel deposits and two associated overbank facies within the durham coal measures major distributary channels were the major avenues of sediment transport across the coal measures plain were variably sinuous mostly 1 2 km wide and deposited elongate belts of sand mostly up to 5 km wide proximal major crevasse splay channels formed by the breaching of major channel banks during flood events were straight sand filled and up to 400 m wide minor distributary channels formed by the sustained operation of such crevasses varied from straight to highly sinuous and deposited shoestring sand mud belts up to a few hundred metres wide minor crevasse channels generally straight and up to 50 m wide were formed through bank breaching of minor and in a few cases major distributaries distal feeder channels formed down palaeocurrent extensions of minor distributaries which supplied interdistributary minor delta subsystems were generally straight and up to 200 m wide of the two types of channel overbank levee deposits recognized one comprising thinly interbedded fine grained sandstone and siltstone claystone is mostly though not exclusively associated with major distributary channels the other consisting of massive siltstones with regularly spaced thin claystone bands is uniquely developed at the margins of minor distributary channels the lower part of the westphalian a succession in the northern pennines records a change in the depositional environment upwards from a lower to upper delta plain through this transition major channel deposits show evidence of having evolved from being of dominantly low sinuosity to being more variable in morphology channel sedimentation was profoundly influenced by regular possibly seasonal variations in flow stage and sediment load

phyto and chronostratigraphical correlations between the late pennsylvanian morien group sydney nova scotia and the silesian pennant measures south wales three macrofloral interval zones lobatopteris vestita l micromiltoni and linopteris bunburii recognized in the westphalian d and the cantabrica biozone in the stephanian of europe are also present in the morien group pictou group of sydney coalfield nova scotia these zones allow a more refined correlation to be made between sequences of the same age in the sydney and south wales coalfields and thus between western europe and north america in general

a drowned lycopsid forest above the mahoning coal conemaugh group upper pennsylvanian in eastern ohio u s a over 800 mud filled casts of upright lycopsid tree stumps have been documented immediately above the mahoning coal in an active underground mine located in northwestern jefferson county ohio the coal body originated as a pod shaped peat body of 60 km2 trees are rooted at several levels within a thin 15 40 cm bone coal directly above the banded coal they extend upward up to 15 cm into overlying flat bedded carbonaceous mudstones that coarsen up from a maximum basal diameter of 1 2 m stumps taper upward to diameters no less than 0 3 m within single entry transects 6 m wide that total 2585 m in length stumps are randomly distributed the trees are identified as lepidodenrids on the basis of gross morphology external stem patterns and attached stigmarian root systems and provisionally as lepidophloios or lepidodendron by associated palynology of the enclosing matrix palynological analyses of incremental seam samples indicate an initial dominance of lycopsid spores with lepidodendracean affinities lycospora granulata from lepidophloios hallii replaced upwards by tree fern spores with a reoccurrence of lepidodendracean spores in the upper benches spores of sigillaria crassispora are abundant only at the base of the coal petrographic analyses indicate a prallel trend from vitrinite rich to inertinite and liptinite rich upward in the coal body all data indicate that the peat represented by the mahoning coal was drowned slowly during the earliest stages of inundation a lycopsid forest was re established only to be subsequently drowned