coal maceral ratios as indicators of environment of deposition do they work for ombrogenous mires an example from the miocene of new zealand abstract maceral indices were applied to sub bituminous coals of the maryville coal measures as a means of interpreting environment of deposition very low amounts of inertinite and ubiquitous bituminite lead to difficulties in interpretation of the maceral ratios comparison with modern analogues suggests the theoretical basis for discrimination of mire type by maceral ratios is not well founded on the following grounds absence of well structured wood tissues does not imply the absence of arborescent vegetation inertinite formation may be unrelated to vegetation gelification is used in a geochemical sense and does not indicate groundwater table level as supposed for biochemical gelification detrital macerals often result from in situ fragmentation and not transportation

coal characteristics palynology and palaeoenvironmental interpretation of the yenikoy coal of late oligocene age in the thrace basin nw turkey abstract the yenikoy coal field is located in a narrow area between the black sea coast and the istranca standrja mountain in the thrace basin the aims of this study are to characterize coal petrographical mineralogical palynological geochemical and sedimentological properties of the yenikoy coal deposit and to reconstruct palaeoenvironmental conditions during peat accumulation a total of 9 coal samples collected from the coal seam section are almost entirely composed of xylite rich lithotype and are characterized by low ash yield 7 9 21 1 average 13 6 on dry basis and high total s contents 1 0 3 7 average 2 2 on dry basis the macroscopic features maceral composition and coal facies suggest that the peat was accumulated under mesotrophic anoxic conditions and the peat forming vegetation consisted mainly of arboreal species e g cupressaceae ulmus carya zelkova alnus pterocarya and quercus the low hi values of the analysed samples are presumably related to presence of xylite rich lithotype rather than the dominance of herbaceous plant and or low preservation of organic matter in the palaeomire even though relatively b enrichments high total s contents and weak anomalies of some rey e g y ce and gd in the analysed samples could refer possible sea water influence into palaeomire in the study area during late oligocene the sedimentological and palynological freshwater algaes pediastrum spirogyra and mougeotia data that indicate the palaeomire was located within a delta plain environment where small freshwater lakes and or ponds developed the statistical analysis and sem edx data show the vast majority of elements in the analysed coal samples have inorganic affinity the major elements al k and enriched elements like b v cr hg and u seem to be affiliated with aluminosilicate minerals whereas fe ni and as have probably sulphide affinity the detrital presences of apatite crystals as detected by sem edx analysis indicate that rey have mainly phosphate affinity in the analysed samples vertical distributions of the elements and ash yields suggest that the detrital input ratio was changeable and controlled some elemental enrichment during peat accumulation these variations could be related to development of and fluvial conditions in the study area which interrupted peat accumulation several times during late oligocene

vegetation zones and diagnostic pollen profiles of a coastal peat swamp bocas del toro panama abstract a survey of the dominant vegetative cover of a large domed coastal swamp near changuinola in the province of bocas del toro panama has been undertaken as an initial step in reconstructing the holocene history of peat accumulation on this coast seven phasic communities of peat forming vegetation are defined and mapped 1 rhizophora mangle mangrove swamp 2 mixed back mangrove swamp 3 raphia taedigera palm swamp 4 mixed forest swamp 5 campnosperma panamensis forest swamp 6 sawgrass stunted forest swamp 7 myrica cyrilla bog plain pollen extracted from surface peat samples and collected from dominant vegetation at representative sites is used to prepare a pollen profile of each phasic community these profiles are then compared to pollen distribution in 2 peat cores one from the deep central part of the deposit and the second from a site near the marine margin in order to construct a history by floral succession of the 4000 year evolution of the deposit the changuinola mire originated as freshwater palm and hardwood forest swamps that developed in close proximity to both the changuinola river mouth probably behind a barrier bar and freshwater lagoon system adjacent to a low energy mangrove dominated bay the early swamp was likely drained to the southeast by brackish blackwater creeks much as it is today and formerly extended considerably farther in the direction of almirante bay the palm swamp was succeeded by hardwood forest swamp dominated by a very limited number of specialized species only one of which campnosperma panamensis is prone to forming monospecific stands increasing accumulation of woody peat promoted by the everwet climate impeded drainage of the mire leading to doming increased oligotrophy and establishment of bog plain conditions in a manner similar to that described by the anderson model of succession in the coastal swamps of malaysia and indonesia development of the changuinola mire did not require the initial mangrove phase which is common to the peat swamps of southeast asia as the palm raphia taedigera is able to colonise and institute peat accumulation in a variety of freshwater and brackish environments

accumulation of organic rich sediments in a dendritic fluvial lacustrine mire system at tasik bera malaysia implications for coal formation abstract the tasik bera mire system represents deposition of peat and peaty sediments within a dendritic fluvial drainage basin in the humid tropics as such it serves as an analogue for the earliest stages of coal deposition in low relief topogenous coal swamps peaty sediments have been accumulating for at least 4500 years in the lowest part of the basin but accumulation rates and hence the thickness and lateral extent of the mire underwent a rapid increase and expansion beginning at about 660 years b p the sediments are highly variable both vertically and laterally the variations principally controlled by the type of vegetation dominant vegetation in turn is related to the degree of wetness of the site three distinct environments of deposition contribute peat with physical characteristics which can be related to coals the limnetic environment dominated by algae and easily degraded aquatic macrophytes contributes very fine hemic peaty sediment with high fine silt content and a large algal component the littoral environment is dominated by sedges and the woody shrub pandanus both of which have a large subaqueous biomass and are quite resistant to degradation sediment from this environment is woody hemic to coarse hemic with a moderate to high very fine silt content and a much smaller algal element forest swamps which occupy most of the mire area contribute woody fibric to hemic peaty sediments with low to moderate mineral matter content in the form of clays and very fine silt succession from both limnetic to forest swamp and the reverse is recorded in cores from different sites in coals these transitions would be manifest as both brightening upward algaedominated peat to woody peat and dulling upward the reverse sequence trends the first in the topographically lower part of the basin the second in the middle reaches no part of the mire yet studied is approaching oligotrophic conditions allowing for a compression ratio of 5 1 thin stony coals from the tasik bera mire would be laterally discontinuous and would vary from about 1 m in thickness at channel margins tapering out to nothing as they onlap the interfluves

marine flooding events and coal bed sequence architecture in southern west virginia abstract eight regional lower to middle pennsylvanian coal beds namurian b c to westphalian c in southern west virginia were examined beds were divided into their component sedimentary parts or benches by identifying bounding surfaces and associated siliciclastic partings within beds bounding surfaces represent the cessation of peat accumulation paleo peat mire morphology at the bench level was determined using shape analysis petrographic indices and coal chemistry data planar and raised paleo peat mire benches were identified all gas coal and some splint coal benches were derived from raised mires heterolithic coal and the remaining splint coal benches were derived from planar mires most bounding surfaces are thin composed of oxidized and degraded organic materials high in ash and sulfur content and contain clay minerals and silt sized quartz vitrinite reflectance is suppressed in the upper part of some benches the associated siliciclastic parting materials when thick show evidence of tidal influence and contain brackish water to marine trace fossil assemblages bounding surfaces and the associated sediments represent a sudden increase in water depth and the lateral continuity of these surfaces indicates regional to basinal extent bounding surfaces are the up paleoslope expression of rapid

late holocene sedimentary environments and lake level fluctuations at walker lake nevada usa walker lake is a terminal lake located at the end of the walker river in western nevada lake level lowering of 50 m during the past 100 yr has led to deep incision by the walker river into the former lake bed this incision has exposed a sedimentary record of lake level fluctuations spanning at least the past 4000 yr fourteen new radiocarbon dates on plant material collected from diverse sedimentary environments including fluvial deltaic beach and offshore settings have led to the refinement of the late holocene lake level curve for this basin this new curve documents at least four highstands that have occurred since ca 3500 cal yr b p between elevations of 1245 and 1255 m the lake has also experienced several lowstands during this same period comparison of this outcrop based record to existing lake level curves and to an oxygen isotope curve for the past 1200 yr reveals many similarities between the records but also some differences therefore research should be conducted to integrate outcrop studies where absolute water depth and lake volume can be estimated with isotopic or other types of proxies from cored sediments that may have higher temporal resolution the extensive and nearly continuous outcrops along the lower walker river also provide valuable information on the relationships between various sedimentary features and their formative water depths in clastic dominated lacustrine systems the paleo water depth relationships deciphered here can be applied in other basins where outcrops are typically more limited to arrive at better constrained lake level records

controls on the chemical variability of peat types in a domed peat deposit baram river area sarawak malaysia pyrolysis gc ft ir fid and pyrolysis gc ms studies have been conducted on peat samples from the margin and central portions of a tropical domed peat deposit in the baram river area sarawak malaysia in order to determine the chemical variability of peat types found within the deposit in an effort to unmix the chemical variability of the samples an extended qmodel program was utilized which produced a series of 4 end members these end members composed of various proportions of each of the 49 pyrolysis products monitored in this study are combined in various proportions to reproduce the composition of each of the 32 samples comparison of the chemical data with previous petrographic and megascopic analysis reveals parallel trends between the input from the end members and the makeup and degree of degradation of each of the peat types from this analysis it can be concluded that the 4 end members produced in this analysis represent input from a guaiacyl lignins b lignin biodegradation products c cellulosic derived products and d syringyl lignins the inputs from the 4 end members can be traced to the type of plants and the degree of degradation in addition comparison of the spatial distribution of the 4 end members reveals that the samples in the central portion of the deposit have much more chemical variability than the highly degraded samples on the margin of the deposit

new evidence for an extended occupation of the provo shoreline and implications for regional climate change pleistocene lake bonneville utah usa abstract lake bonneville was a climatically sensitive closed basin lake that occupied the eastern great basin during the late pleistocene ongoing efforts to refine the record of lake level history are important for deciphering climate conditions in the bonneville basin and for facilitating correlations with regional and global records of climate change radiocarbon data from this and other studies suggest that the lake oscillated at or near the provo level much longer than depicted by current models of lake level change radiocarbon data also suggest that the lake dropped from threshold control much more rapidly than previously supposed these revisions to the lake bonneville hydrograph coupled with independent evidence of climate change from vegetation and glacial records have important implications for conditions in the bonneville basin and during the pleistocene to holocene transition

a depositional model for the taylor coal bed martin and johnson counties eastern kentucky abstract this study investigated the taylor coal bed in johnson and martin counties eastern kentucky using field and petrographic techniques to develop a depositional model of the coal bed petrography and chemistry of the coal bed were examined multiple benches of the taylor coal bed were correlated over a 10 km distance three sites were studied in detail the coal at the western and eastern sites were relatively thin and split by thick clastic partings the coal at the central site was the thickest and unsplit two major clastic partings are included in the coal bed each represents a separate and distinct fluvial splay the taylor is interpreted to have developed on a coastal plain with periodic flooding from nearby structurally controlled fluvial systems doming is unlikely due to the petrographic and chemical trends which are inconsistent with modern indonesian models the depositional history and structural and stratigraphic setting suggest contemporaneous structural influence on thickness and quality of the taylor coal bed in this area

lithotype sequences in the early miocene maryville coal measures new zealand abstract coals of the early miocene maryville coal measures show well developed dulling up trends defined by a decrease in the proportion of bright coal that culminate in sapropelic horizons field determination of lithotype is difficult but the use of polished surfaces enables classification by either the brightness or stopes heerlen systems during upwards dulling gross petrographic composition remains essentially constant at 80 90 huminite vitrinite 10 15 liptinite and 1 4 inertinite except in sapropelic types which are liptinite dominated dull bands are characterized petrographically by fragmentary macerals especially detrogelinite whereas bright bands are composed of intact plant fragments dulling up is related to the development of raised ombrogenous mires where growth and subsequent preservation of large intact plant fragments is favoured during early stages of mire development and around the mire margins

characterization and quantification of inorganic constituents of tropical peats and organic rich deposits from tasek bera peninsular malaysia implications for coals abstract since the carboniferous tropical latitudes have been the site of formation of many economic coal deposits most of which have a restricted range of mineralogical composition as a result of their depositional environment climatic conditions and diagenesis mineralogical and microscopic investigations of tropical peats from tasek bera peninsular malaysia were performed in order to better understand some of these factors controlling the nature distribution and association of inorganic matter in peat forming environments distribution and nature of the inorganic fraction of peat deposits give insight into the weathering conditions and detrital input into the mire system because the inorganic composition of peat deposits is determined by plant communities height of water table and climate the results of the quantitative and qualitative analysis can be used to reconstruct palaeoclimatic conditions tasek bera is a peat accumulating basin in humid tropical malaysia with organic deposits of low to high ash yield and thus representative of many ancient peat forming environments clay minerals dominate the mineralogical composition of the peat and organic rich sediments while quartz and clays dominate the underlying siliciclastic deposits kaolinite is the most abundant clay mineral in the organic deposits with minor amounts of illite and vermiculite particle size analyses indicate that 50 of the inorganic detrital fraction is 75 of the ash constituents as a consequence the vegetational communities make an important contribution to the inorganic and overall ash composition of peats and coals the ash content of the often inundated peat consists on average of 10 opaline silica from diatoms and sponge spicules while the ash of the top deposits may have up to 50 biogenic silica hence al and si hydroxides and the opaline silica from diatoms and sponges represent a large repository of al and si which may form the basis of mineral transformation neoformation and alteration processes during coalification of the peat deposits as a result most coal deposits from paleotropical environments are anticipated to have little to no biogenic inorganic material but high amounts of secondary clays such as kaolinite detrital kaolinite resilisified kaolinite or desilisified gibbsite or illite and various amounts of detrital and authigenetic quartz

the formation of inertinite rich peats in the mid cretaceous gates formation implications for the interpretation of mid albian history of paleowildfire abstract image analysis and standard point count petrographic data are used to interpret the amount source and variation of inertinite in coal seams of the mid cretaceous gates formation rocky mountain foothills northeastern british columbia inertinite on average is abundant between 40 60 by seam by volume and higher in some zones and within seams fluctuates cyclically the inertinite is interpreted to be almost exclusively fire derived suggesting that fire was a relatively common occurrence in the original peat forming wetlands inertinite enrichment in the gates coals appears to have resulted from preferential destruction of vitrinite precursors by either low temperature decomposition processes or burning rather than by formation of inertinite by a microbial process the position of the gates formation depositional setting east of the rising canadian cordillera is interpreted to have resulted in overall drier conditions in the region and periodic drought in the wetland settings cyclic variation in inertinite vitrinite composition within some of the seams is primarily attributed to climatic variations although variation in subsidence rates could also have been responsible

application of 3 d seismic attributes analysis to mine planning target gold deposit south africa major south african gold mining companies have recently turned to 3 d seismic surveys for mine planning in witwatersrand basin e g pretorius et al 1997 we present examples showing that 3 d seismic data provide the gross structure and depth of the prospective stratiform ore horizons the original objective of such surveys and that careful analysis of 3 d seismic attributes backed up with borehole control direct geologic observations and synthetic seismograms can provide important information on small scale faulting throws of 10 20 m and lithologic variations of the ore zone conglomerates

peat accumulating depositional systems of sarawak east malaysia many coal deposits originate in deltaic estuarine and coastal plain settings and a knowledge of interrelationships between the tectonic and depositional elements active at the time of sediment deposition is necessary to formulate basin scale models the prograding coastal depositional systems of sarawak all contain domed peat accumulating environments in which low ash low sulfur peats are being deposited in areas of active clastic siliciclastic sedimentation these depositional systems are as large as 11 400 km2 and individual peat deposits within systems are in excess of 20 m thick and 1000 km2 in area the geographic positions and drainage basin areas of each depositional system are controlled by fault and fold systems although prograding into the same receiving basin individual system geomorphology is variable and ranges from a wave dominated microtidal delta to a wave dominated meso to macro tidal delta coastal plain system to a tide dominated macrotidal estuarine embayment along a 450 km stretch of coastline system variation is a function of sediment supply shelf and embayment geometry wave climate and tidal range these factors which control depositional system geomorphology also control the resulting long axis orientation of the thick domed peat deposits the surface vegetation and internal characteristics of most domed peat deposits however are similar internal characteristics consist of basal high ash high sulfur degraded peats overlain by low ash low sulfur well preserved peats in vertical profile these systems demonstrate variable responses to late pleistocene holocene sea level rise and in these instances the variation is most attributable to local differences in siliciclastic sediment supply which is a function of the drainage basin area

the age palaeoclimate palaeovegetation coal seam architecture mire types paleodepositional environments and thermal maturity of syn collision paralic coal from mukah sarawak malaysia abstract the mukah coal accumulated in the balingian formation where the time stratigraphic position is poorly defined by fauna though a probable late miocene age has always been assigned to this formation samples collected in the present study that yielded an abundance of casuarina pollen associated with occurrences of dacrydium stenochlaena palustris florschuetzia levipoli and also stenochlaena areolaris spores compare closely to zone pr9 of the palynological zonation of the malay basin and can be tied to depositional sequences of malay basin seismic sequences i2000 i3000 indicating an early miocene age for the studied coal the early miocene age shows that the mukah coal was formed during the collision between luconia block dangerous grounds with the borneo that lasted from late eocene to late early miocene the rapid increase of deposition base level caused by the collision is clearly reflected by the architecture of the mukah coal seams that were generally thin and also by the reverse order of the paleo peat bodies the studied coal samples contained large amounts of detrohuminite without the enrichment of liptinite group macerals usually explained by the dominance of herbaceous plants in the paleomires however the pollen assemblages recovered in the present study provide no support for a herbaceous swamp instead the peats were likely formed mainly from forest vegetation based on the recovery of dominant arboreal pollen assemblages in the present study palynomorph assemblages recovered in the present study with abundance of casuarina pollen associated with common occurrences of dacrydium strongly suggest kerangas vegetation and kerapah type peat swamps indicating a very wet climate the occurrence of rattan and pandanus pollens shows that the kerapah type peat swamps were locally bordered by rattan and pandanus swamps this shows that the prevailing use of coal petrography to discern the type of vegetation that was present in the peat forming mires may lead to wrong conclusions therefore a multi disciplinary approach must be applied for a more accurate and reliable spatial interpretation of the type of vegetation that was present in the peat forming mires consistent with the low sulphur content evidence from the palynomorph assemblages recovered from the coal seams shows that the coal forming peat was deposited in freshwater mires with little or no marine influence despite the fact that the accumulation of the mukah coal forming peat took place within a coastal plain setting moreover the fauna present in the host rock formation also suggested a brackish water environment of deposition

the rise and fall of lake bonneville between 45 and 10 5 ka a sediment core taken from the western edge of the bonneville basin has provided high resolution proxy records of relative lake size change for the period 45 1e10 5 calendar ka hereafter ka age control was provided by a paleomagnetic secular variation psv based age model for blue lake core bl04 4 continuous records of d 18 o and total inorganic carbon tic generally match an earlier lake level envelope based on outcrops and geomorphic features but with differences in the timing of some hydrologic events states the stansbury oscillation was found to consist of two oscillations centered on 25 and 24 ka lake bonneville appears to have reached its geomorphic highstand and began spilling at 18 5 ka the fall from the highstand to the provo level occurred at 17 0 ka and the lake intermittently overflowed at the provo level until 15 2 ka at which time the lake fell again bottoming out at w14 7 ka the lake also fell briefly below the provo level at w15 9 ka carbonate and d

marine influence helps preserve the oil potential of coaly source rocks eocene mangahewa formation taranaki basin new zealand abstract many cretaceous cenozoic coaly source rocks in australasian and southeast asian basins were deposited in coastal plain environments yet the effect of early diagenetic marine influence on their oil potential is not well understood an integrated organic geochemical and petrographic study of humic coals from the eocene mangahewa formation taranaki basin new zealand was undertaken with coals predominantly from raised mire petrofacies with subordinate proportions from planar mires the total s content of 0 63 4 4 dry ash free indicated very slight to strong degrees of marine influence other than minor addition of inferred mangrove derived suberinite and associated liptodetrinite the degree of marine influence had no obvious effect on maceral or plant tissue abundance however hydrogen index hi values were up to ca 150 109 mg hc g toc higher and total c 6 oil potential up to ca 140 43 mg g toc higher among the more strongly marine influenced coals correlation of organic s with solvent extract parameters pristane phytane c 27 c 29 diasteranes steranes c 29 steranes hopanes c 35 c 35 c 34 homohopanes and oleanane index suggested that inundation of brackish water into the early diagenetic peat forming environment enhanced the bio resistance of higher plant and other lipids through sulfurization thereby helping to preserve more of the inherent h content and total oil potential of the original peat biomass conversely marine influence had only a minor effect on the capacity of mangahewa coals to generate paraffinic oil total n c 6 and non volatile n c 15 paraffinic oil potentials were instead controlled primarily by the abundance of leaf derived cutinite and associated liptodetrinite this in turn was dependent on the type of peat mire facies with planar mire facies having better potential for preservation of leaf litter than raised mire facies because of their generally higher groundwater level marine influence is nonetheless beneficial for paraffinic oil charge from coaly source rock sequences in that the associated higher his enhance the efficiency and quantum of paraffinic oil expulsion through increased saturation of the coal pore system

petrology and genesis of upper carboniferous seams from the ruhr region west germany abstract the petrology of 21 seam profiles of upper carboniferous age westphalian c and b has been studied in order to determine their depositional environments and diagenetic history the youngest profile was drilled at a depth of 790 m and is mainly overlain by cretaceous sediments the oldest seam was reached at a depth of 1470 m the seam thicknesses vary from 0 4 to 2 5 m the main petrographic compounds are vitrinite intertinite liptinite and minerals the last group occurs as clay bands with illite kaolinite minor chlorite and minor quartz contents or as crack or pore filling calcite fe dolomite siderite pyrite or marcasite or as syngenetic siderite concretions and pyrite crystals the percentages of the different macerals and minerals vary mainly because of different depositional environments diagenetic loss or genesis of compounds is a less important factor in their distribution three types of profiles are distinguished by their different petrologies type i is most abundant and contains much vitrinite many clay bands and syngenetic iron sulfides whereas type iii is rich in inertinite and certain characteristic spores type ii is intermediate but generally contains only low percentages of minerals generally this type is vitrinite rich in the lower and inertinite rich in the central and upper parts of the profiles spores and other liptinites are much better preserved in all the seams than in clay partings or in siltstones and sandstones above and below the seams the seams are interpreted to be former autochthonous peats type i profiles are probably derived from swamps which were sometimes inundated and covered by overbank deposits type ii and iii seams represent former peats which were not inundated by rivers and partly grew under the influence of more oxidizing conditions therefore they contain more inertinite and less sulfide and clay bands they can be interpreted as former raised bogs diagenetic changes are expressed as increases of vitrinite reflectances from 0 65 to 1 0 and of liptinite reflectances a red shift of fluorescence of liptinites was found increasing amounts of exudatinite and micrinite and decreasing amounts of fluorinite and resinite were found minerals seem to be less affected by diagenesis illite crystallinity for example remains poor

a test for the analogy of tropical domed peat deposits to dulling up sequences in coal beds preliminary results abstract megascopic and microscopic characteristics of a domed peat deposit in sarawak malaysia were examined to test their analogy to dulling up sequences in low ash coal beds preliminary petrographic results show high concentrations 95 of vitrinite precursor material for all peat types but that fibrous peats in the upper central portion of the deposit contain more preserved plant material than peats toward the base and margins which although more decomposed contain large fragments 5 150 cm of wood these results present contradictory evidence in support of a dulling up model and suggests that modern tropical peat domes are perhaps poor petrographic analogues for dulling up sequences this deposit would produce an all bright coal seam with bright vitrain bands of variable thickness and amount set in bright high vitrinite matrix

changing patterns of pennsylvanian coal swamp vegetation and implications of climatic control on coal occurrence abstract improved regional and interregional stratigraphic correlations of pennsylvanian strata permit comparisons of vegetational changes in euramerican coal swamps the coal swamp vegetation is known directly from in situ coal ball peat deposits from more than 65 coals in the united states and europe interpretations of coal swamp floras on the basis of coal ball peat studies are extended to broader regional and stratigraphic patterns by use of coal palynology objectives of the quantitative analyses of the vegetation in relation to coal are to determine the botanical constituents at the peat stage and their environmental implications for plant growth and peat accumulation morphological and paleoecological analyses provide a basis for deducing freshwater regimes of coal swamps changes in composition of pennsylvanian coal swamp vegetation are quire similar from one paralic coal region to another and show synchrony that is attributable to climate paleobotany and paleogeography of the euramerican province indicate a moist tropical paleoclimate rainfall runoff and evapotranspiration were the variable climatic controls in the distribution of coal swamp vegetation peat accumulation and coal resources in relative terms of climatic wetness the pennsylvanian period is divisible into five intervals which include two relatively drier intervals that developed during the lower middle and middle upper pennsylvanian transitions the climate during early pennsylvanian time was moderately wet and the median in moisture availability early middle pennsylvanian was drier probably seasonally dry wet late middle pennsylvanian was the wettest in the midcontinent early late pennsylvanian was the driest and late late pennsylvanian was probably the wettest in the dunkard basin the five climatic intervals represent a general means of dividing coal resources within each region into groups with similar botanical constituents and environments of peat accumulation regional differences in basinal geology and climate were significant variables but the synchronous control of paleoclimate was of primary importance

the geology botany and chemistry of selected peat forming environments from temperate and tropical latitudes abstract peat has been studied in several geologic settings 1 glaciated terrain in cold temperate maine and minnesota u s a 2 an island in the atlantic ocean off the coast of maine where sea level is rising 3 the warm temperate u s atlantic and gulf coastal plains where sea level has changed often and 4 the tropical coast of sarawak malaysia and the tropical delta of the batang hari river sumatra indonesia most of these deposits are domed ombrotrophic or partly ombrotrophic bogs in which peat accumulation continued above the surface of the surrounding soil however the bogs of the u s atlantic and gulf coastal plains are comparatively not as domed and many have almost level surfaces in some bogs aquatic or semi aquatic plant materials accumulated replaced water in the depressions and formed a surface on which marsh or swamp vegetation could subsequently live die and accumulate in others the plant materials accumulated initially on level silt or sand surfaces supporting marshes or swamps as the peat dome formed plants growing on it changed from luxuriant ones near the base of the dome where nutrients were brought into the bog by surface and ground water to stunted ones at the top of the dome where the raised bogs are fed by nutrient poor precipitation the physical and chemical changes that take place in the sequence of environments from the pond stage of deposit development through the grassy marsh stage through the forested swamp stage and finally through the heath dome stage can be measured in terms of acidity and ash volatile matter carbon hydrogen nitrogen sulfur and oxygen contents as well as in the kind and distribution of trace elements the organic and inorganic contents of the deposits relate to geomorphology and geomorphology relates to their settings as models of coal formation some domed peat deposits may help in solving problems of distribution and character of ancient coal beds but clearly not all peat deposits are precursors of coal most holocene peat deposits are subject to destruction by erosion fire and decomposition through microbial and chemical oxidation before burial the best environments for coal precursors have biomass accumulation a continuously rising water table within the mass and minimum influx of clay and silt until preservation by burial the most suitable settings for future economic coal deposits are domed bogs that accumulate thick widespread peat having low ash and low sulfur contents the ombrotrophic peat deposits of tropical sarawak and sumatra are thick and extensive contain low ash and low sulfur peat and have high heating values they are considered to be the best tropical coal analogs because of their extent and chances of preservation the base of the peat is below adjacent river levels and chemical and structural conditions are favorable for accumulation

chronology of lake bonneville 30 000 to 10 000 yr b p abstract 368 radiocarbon ages between 30 and 10 cal ka for samples collected from outcrops and shorelines from the lake bonneville basin have been compiled for this paper samples include 1 organic materials from sources outside the lake such as wood charcoal plant fragments from emergent aquatics and dispersed wetland organics and 2 carbonate materials deposited in the lake such as mollusk shells tufa charophyte debris ooids and marl in general organic materials provide rather than precise ages for lacustrine events but their interpretation is less complicated than interpretation of results from carbonate samples the data set shows evidence of contamination of different carbonate samples with both younger carbon and older carbon for example a radiocarbon reservoir at certain places within the lake during the middle transgressive phase accounts for ages of mollusk shells that are older than basal wood ages at similar altitudes the large number of ages permits an accurate reconstruction of the lake chronology conflicts between ages can be detected and reliable ages can be meaningfully integrated in interpretations if fewer ages were available the chronology might look simpler but its accuracy would be unknown

development of low ash planar peat swamps in an alluvial plain setting the no 5 block beds westphalian d of southern west virginia abstract coals from the no 5 block coal beds westphalian d of the central appalachian basin are noted for their blocky dull character and their low ash and low sulfur content the beds are multiple benched with rock partings separating benches individual benches have limited lateral extent and where thick are dominated by bright high ash coal at the base and dull low ash coal in the upper parts the duller coals contain more exinite group and inertinite group macerals than the brighter coals these coal beds are encased in sandstone units dominated by fining upward sequences the overall depositional setting is an alluvial plain environment with northwest flowing channels spaced approximately 20 km apart the channels were flanked by clastic swamps about 7 km wide low ash peat accum lated in areas of the flood plain most distant from the channels these peat accumulating swamps were about 8 km across in a few instances low frequency flood events introduced fine siliciclastic sediment into the peat swamps depositing a thin layer of sediment on top of the peat this sediment layer is thicker where the underlying coal is the thickest these thick coal areas are topographically lower than surrounding coal areas this relationship between coal thickness parting thickness and topography indicates that these peat swamps were planar at the time of deposition individual coal benches contain abundant preserved cellular tissue telocollinite semifusinite and fusinite at most locations suggesting that robust vegetation was widespread in the swamps and that the morpholo y was planar the high concentrations of exinite group an inertinite group macerals in the upper parts of benches resulted from selective decomposition and oxidation of the peat in subaerial and aquatic planar swamp environments

low ash peat deposits from a dendritic intermontane basin in the tropics a new model for good quality coals many good quality thick low ash carboniferous cretaceous and tertiary coal deposits have dulling upward sequences that have been interpreted to be of ombrotrophic lowland coastal origin previous studies of potential modern analogues for thick dulling upward coal sequences have focused on tropical ombrotrophic coastal peats however most modern coastal ombrotrophic deposits would yield all bright coal seams new evidence from peat deposits of the southern intermontane tasek bera basin western malaysia reveals that thick low ash low sulfur peat may originate in narrow tributary valleys with moderately steep flank gradients these deposits may be favorable precursors to dulling upward coals in that they contain high wood and low ash content at depth and medium wood and slightly increasing ash content in the upper parts peat accumulation in the tasek bera basin began in mid holocene time during the past 4500 years 500 cm of low ash 40 cm white fluvial silty clay with wood fragments was deposited the clay rich sediments are overlain by limnic black mud sandy clay and dark brown mud rich peat up to 70 cm thick the ash content of the mud rich peat is as high as 31 wt the high ash peat is overlain by low ash sapric to hemic peat up to 5 m thick the basal 3 m of the peat deposits contain abundant logs and large woody fragments whereas the top 2 m have less hard wood but more arborescent fragments of palmae such as roots from pandanus atrocarpus the acrotelm top 50 cm has a low to medium ash content 10 wt with burial the deposits of southern tasek bera basin would yield a dendritic sediment pattern of sandstone shale carbonaceous shale and a dulling upward vitrain rich coal overlain by carbonaceous shale because of the dendritic nature of the tasek bera basin coal seams would most likely have a similar pattern as the carboniferous humic coal deposits of the black warrior basin in alabama usa however the good quality coals with dulling upward characteristics would be concentrated in the southern tributaries of the basin

relationship between petrographic and chemical properties and coal seam geometry hance seam breathitt formation southeastern kentucky the upper hance coal seam in southeastern kentucy was used as a template to examine the spatial distribution of ash yield sulfur content and petrographic constituents relative to the geometry of the deposit geometric characteristics include thinning and splitting of the two main benches leaders and riders analytical data showed the thick non split portions of the coal body to be low in ash and sulfur as well as vitrinite content whereas the thinned and split margins were higher in ash sulfur and vitrinite content these relationships suggest that thick non split portions of the upper hance peat accumulated in areas isolated from detrital influx while thinner marginal peat was subject to intermittent flooding from adjacent channels marginal peat was derived from larger trees which flourished at the mire s edge in the presence of adequate nutrients whereas only stunted vegetation subsisting in the nutrient depleted center contributed to interior peat accumulation ponds formed on the sparsely vegetated mature surface of the bog s interior the petrographic and chemical character of the hance coal body is analogous to ombrogenous domed peats which characteristically contain higher concentrations of inorganics at the periphery of the deposit

a short term establishment of forest fen habitat during pliocene lignite formation in the ptolemais basin nw macedonia greece the intermontane basin of ptolemais is part of a major tectonic trench located in nw greece and includes around 65 of greek coal reserves the upper xylite layer uxl is a distinct lignite layer being 3 6 m thick and outcropping in the upper part of the pliocene lignite bearing sequence at the notio field and tomeas eksi mines of ptolemais compared with the xylite rich lithotypes the matrix lithotypes within uxl contain more ash micropetrographic studies suggest that the upper xylite layer is rich in huminite 90 textinite dominates in the xylite rich lithotypes while attrinite dominates in the matrix lithotypes the liptinite content is 10 while inertinite rarely occurs palaeobotanical determination revealed that the xylite rich coal originated from coniferous vegetation specifically from glyptostrobus europaeus the occurrence of g europaeus as a coal forming element is significant because though this kind of vegetation was common in many greek coals of miocene age this is the first time it has been recorded from the pliocene this study suggests that the upper xylite layer is autochthonous according to coal facies diagrammes peat accumulated under pure telmatic conditions in a relatively wet forest fen both herbaceous and arboreal vegetation contributed to peat formation

lacustrine cave carbonates novel archives of paleohydrologic change in the bonneville basin utah usa records of past changes in lake levels and lake water isotopic composition in closed basins provide key insights into past variations in the hydrological cycle however these records are often limited by dating precision and temporal resolution here we present data from lacustrine cave carbonates a previously unexplored class of carbonates that comprise a promising new archive of past hydrologic changes in the bonneville basin of the northeastern great basin usa these dense carbonates precipitated within caves crevices and other protected spaces flooded by lake bonneville during its highstand in the last glacial period we report on deposits in cathedral and craners caves located 50 km apart at similar elevations approximately 100 m above the modern great salt lake and almost 200 m below lake bonneville s highstand shoreline carbonates from the two caves show similar chronologies mineralogical transitions isotopic compositions and uranium concentrations these findings suggest that lacustrine cave carbonates record changes in lake level and in the isotopic composition and chemistry of lake water importantly the deposits can be precisely dated by u th methods providing the first records of lake bonneville s water balance changes tied to precise u th ages close agreement between paired u th and calibrated 14 c ages in the deposits suggests a minimal o200 a carbon reservoir effect in the lake and allows 14 c dating to be used for age control in portions of the deposits less suitable for u th dating we use ages for the onset and cessation of lacustrine cave carbonate deposition to offer new constraints on past changes in lake level and the carbonate saturation state of lake water we also present precisely dated high resolution oxygen and uranium isotope records from the deposits within a first phase of deposition reflecting the lake s transgression between 26 and 18 ka our isotopic data suggest a large influx of freshwater during heinrich stadial 2 a hiatus in deposition beginning at 18 270 3 ka may be the result of freshening related to the lake s overflow calcite deposition resumes at cathedral cave at 16 470 2 ka suggesting that basin overflow had ceased by this time and that the lake s calcite saturation state had increased andd 18 o values increase markedly after 15 9 ka consistent with drying at this time these data imply that the lake s deglacial regression began well before the bolling warming cessation of this second phase of deposition at 14 770 2 ka coincident with the bolling warming may reflect the lake s drop below cathedral cave s elevation a final stage of aragonite deposition between 13 8 and 13 6 ka differs from the underlying facies and may not reflect deposition from lake waters filling the cave

a comparison of temperate and boreal peats from ontario canada possible modern analogues for permian coals abstract peat profiles were sampled from a raised bog and an interior fen located in the boreal james bay lowlands northern ontario and a cold temperate swamp and a cold temperate bog in the great lakes st lawrence lowlands southern ontario an examination of the micromorphology and maceral compositions of the peats indicates that considerable differences exist between environments the boreal bog and fen both consist predominantly of relatively unaltered textinite commonly sphagnum derived with higher liptinite contents in the fen profile attributable to the more diverse vegetation both the cold temperate swamp and bog show high levels of humification at the surface possibly partially attributable to recent climatic warming trends causing a decline in water table elevation in all profiles funginite was persistent ranging from 2 to 10 of the total maceral content indicating that aerobic conditions generally prevailed at the surface at the time of deposition the influence of depositional environment and vegetation type on the resulting peat was born out in plots of tissue preservation index vs gelification index the petrographic study also demonstrated that none of the profiles contained high inertodetrinite semifusinite contents comparable to those within cold climate cratonic permian gondwana coals since the oxidation processes leading to the formation of inertinite are considered to take place at the peat stage if the peats studied were to contain a similar maceral assemblage upon coalification inertinite precursors may be present in the peat the lack of petrographic similarity between the holocene peats and the permian coals may be related to a number of factors the decrease in water table elevation possibly responsible for the inertinization of the permian coals may have occurred following the cessation of peat formation not concurrently with accumulation and is potentially attributable to long term factors such as climatic warming the change in the peat forming vegetation from permian glossopteris and gangamopteris dominated communities to holocene sphagnum and coniferous vegetation alters the characteristics of the initial botanical starting materials and some aspects of the ecology particularly trophic and ph conditions which control the post depositional alteration of the plant materials and the resulting maceral assemblages

stratigraphy and chronology of offshore to nearshore deposits associated with the provo shoreline pleistocene lake bonneville utah abstract stratigraphic descriptions and radiocarbon data from eleven field locations are presented in this paper to establish a chronostratigraphic framework for offshore to nearshore deposits of lake bonneville based on key marker beds and geomorphic position the deposits are interpreted to have accumulated during the period from the late transgressive phase through the overflowing phase into the regressive phase of the lake radiocarbon ages of sediments associated with the provo shoreline indicate that lake bonneville dropped rapidly from the provo shoreline at about 12 600 14c yr bp 15 000 cal yr b p the presence of one or more sand beds in the upper part of the provo aged marl indicates rapid lowering of lake level or storm events at the end of the provo episode an accurate understanding of the timing and nature of lake bonneville s climate driven regression from the provo shoreline is critical to correlations with records of regional and hemispheric climate change the rapid descent of the lake from the provo shoreline correlates with the decline of lakes lahontan and estancia and with the onset of the b o lling aller o d warming event

transgressive stratigraphic record and possible oscillations of late pleistocene lake bonneville northern hogup mountains utah u s a abstract distinct mappable facies changes make the stratigraphic record of the shorezone of late pleistocene lake bonneville the most robust indicator for past lake level oscillations unfortunately clear stratigraphic evidence of transgressive and regressive deposits has been generally lacking new stratigraphic and chronological data within the lacustrine shorezone sediments of the hogup mountains of northwestern utah provide some of the best evidence yet for oscillations within the overall transgressive phase of the lake this study documents two previously unknown oscillations hereby named the lower hogup 22 cal ka and upper hogup 20 6 cal ka oscillations and provides further evidence for the previously proposed u2 oscillation 21 3 cal ka the study suggests that the water level of the lake changed dramatically up to 25 of the lake s total volume during the transgressive phase 30 15 cal ka with the additional oscillations documented in this study there are seven proposed oscillatory events during the transgressive phase of the lake these events likely correlate to rapid but short term regional climatic fluctuations during the broader climatic trends of the last glacial maximum however it is still unknown what specific climatic drivers are causing these oscillations and if these events can be correlated to other global climatic events

great salt lake and precursors utah the last 30 000 years sediment cores up to 6 5 m in length from the south arm of great salt lake utah have been correlated radiocarbon ages and volcanic tephra layers indicate a record of greater than 30 000 years a variety of approaches have been employed to collect data used in stratigraphic correlation and lake elevation interpretation these include acoustic stratigraphy sedimentologic analyses mineralogy geochemistry major element c o and s isotopes and organics paleontology and pollen the results indicate that prior to 32 000 year b p an ephemeral saline lake playa system was present in the basin the perennial lake which has occupied the basin since this time rose in a series of three major steps the freshest water conditions and presumably highest altitude was reached at about 17 000 year b p the lake remained fresh for a brief period followed by a rapid increase in salinity and sharp lowering in elevation to levels below that of the present great salt lake the lake remained at low elevations and divided at times into a north and south basin until about 8 000 year b p since that time with the exception of two short rises to about 1290 m the lake level has remained near the present elevation of 1280 m

geochemical and petrographical characteristics of a domed bog nova scotia a modern analogue for temperate coal deposits a freshwater domed bog in nova scotia canada was investigated for its petrographic mineralogical and geochemical characteristics three cores were taken from the lagg zone margin and centre to examine different stages of evolution in a fen to domed bog sequence based on this study a model was developed which shows the relationship between factors controlling peat geochemistry and petrography all of them being dependent on trophic conditions the bog may represent a modern analogue for temperate coal deposits and thus can be used to help understand spatial variability within coal beds rheotrophic conditions in the early stages of mire development result in the formation of high ash highly humified carex dominated peat while the evolution toward ombrotrophic conditions is reflected in a progressive replacement by low ash and well preserved sphagnum dominated peat the associated decrease in ph reflects a decrease of groundwater influence which is also supported by the mineralogical assemblage and petrographic data decrease in reflectance and change in maceral composition except for cl br i and se which are associated with the organic fraction variations in elemental composition can be explained in terms of mineral matter abundance i e decrease upward and with increasing distance from the margin sea spray is the most probable origin for halogen enrichment in the peat

coal facies studies in the eastern united states coals in the eastern united states east of the mississippi river have been the subject of a number of coal facies studies going back to the 19th century such studies would not necessarily fall within a strict modern classification of coal facies studies but if a study encompassed some aspects of paleobotany palynology petrology geochemistry or sedimentology we assumed that some data and interpretations may be of use in evaluations of the facies references are presented as a guide for further research with annotation in the tables

botanical control on banding character in two new zealand coal beds abstract two new zealand coal beds were examined using a palaeobotanical approach to determine controls on banding characteristics the morley cretaceous coal is thickly 5 to 1 or 32 to 2 mm and well 25 banded whereas the brunner eocene coal is essentially non banded palynological analyses indicate that the morley was formed from a gymnosperm dominated vegetation with a secondary component of angiosperms in contrast the brunner was dominated by angiosperm vegetation with only a minor component of gymnosperms however it was found that any xylite vitrain bands 1 mm in either coal bed were comprised exclusively of secondary xylem of probable gymnosperm origin the presence of gymnosperm wood i e secondary xylem forming the larger bands in both coals can be related to the relative resistance of this material to chemical and physical decay as compared to all other plant tissues an absence of angiosperm wood in either the morley or brunner coal beds may be the result of the relative chemical degradability of angiosperm wood as compared to gymnosperm wood alternatively angiosperms in either of the two palaeo mires may have been shrubby and thus did not produce abundant woody tissue in either case the banded nature of the morley coal bed is the result of the presence of gymnosperm wood and the non banded nature of the brunner is the result of being dominated by a flora angiosperm which is easily degraded

on the use of modern tropical domed peats as analogues for petrographic variation in carboniferous coal beds abstract a series of peat cores were collected along four transects in indonesia and malaysia for the purpose of developing modern analogues for the development of bright and dull lithofacies in coal fig 1 each deposit consists of a number of well defined zones of peat which reflect the original plant types and the degree of degradation these components vary with respect to their position within the peat body for example the sumatran deposit consists of predominantly of moderately decomposed woody peat with thin interbeds of coarser peat which become thicker in the central upper portion of the deposit fig 2 in contrast the cross sections from the malyasian transects show more distinct stratification in peat types and thicker coarse peat zones in the center of the deposit fig 3 presumably as the coast progrades the near coastal peats are being progressively overlain by inland forest peats as evidenced in the more mature deposits landward anderson 1964 although comparisons of bright to dull trends in coal i e decreasing vitrain band thickness and or vitrinite content have been made to the internal strata of the peat on the basis of the decreasing distribution of large wood fragments upwards within the deposits esterle and ferm 1986 esterle and tie in press the premaceral composition of these peats has not been fully established for this purpose a series of samples from each deposit was selected for petrographic examination in reflected light using coal petrologic methods wet peat samples were first frozen in liquid nitrogen lyophilized and finally vacuum impregnated with a low temperature bioplastic impregnated samples were then set up as blocks ground and polished for petrographic examination using brown coal terminology preliminary results show striking differences between the distinctly domed peat at tg pasir in sarawak and the relatively flat topped peat in jambi sumatra although the composition of both deposits is dominated by macerals of the huminite group which show relative decreases in the amount of structured textinite and humotelinite downhole and towards the margins of the deposit internite contents vary differently in the sarawak domed deposit inertinite macerals are virtually absent throughout and only occur in low percentages the results of preliminary petrographic examination suggest that modifications are needed for the usage of modern domed peat deposits as analogues for petrographic variation in carboniferous coal beds although the decrease in the size and amount of wood fragments in modern domed peat deposits supports a dulling up or decreasing vitrain band thickness model for coal on a megascopic scale the petrographic data show contradictory evidence

some observations regarding the potential effects of doming of tropical peat deposits on the composition of coal beds abstract several important concepts relative to the origin of coal beds can be gleaned from studies of modern domed and planar peat deposits in tropical subtropical settings these are 1 laterally some portions of a single continuous peat deposit may be domed and some portions may be planar 2 domed deposits are most often found to have begun as planar deposits 3 domed formed peat facies may be overridden by planar formed peat facies due to such factors as sea level rise and or increased rate of local and basinal subsidence 4 domed peat facies tend to have less mineral matter and contain fewer inorganic splits than planar facies 5 sulfur intrusion from marine waters can be retarded by doming allowing low sulfur peats to form relatively near to the coastline 6 marine transgression can cause high sulfur marine influenced planar peat facies to override freshwater domed or planar facies resulting in enrichment of the upper parts of these underlying facies in sulfur and ash 7 dome formed peat facies tend to be thicker and more uniform in composition than planar formed facies with dome formed peat facies having the potential to produce the more uniform bright coal types clarains and vitrains and planar formed peat facies often producing duller coal types and or alternating durainic inertinite rich and vitrainic wood derived bands 8 actively developing peat domes in wet settings often exhibit no appreciable increase in inertinitic material toward their tops although the tops of either domed or planar peat deposits can be enriched in inertinitic material if the water table is lowered by either local or regional changes in hydrology or climate

palynofacies coal petrographic facies and depositional environments amphitheatre formation eocene to oligocene and ravenscrag formation maastrichtian to paleocene canada abstract low rank coals from two disparate geological settings have been subjected to petrographic and palynological analysis the stratigraphic units studied and their locations are the amphitheatre formation st elias mountains yukon territory of eocene to oligocene age and the base of the ravenscrag formation south central saskatchewan of latest cretaceous to earliest paleocene age the depositional setting of the amphitheatre formation ranges from distal sand dominated braided stream and lacustrine environments to proximal gravel dominated fluvial environments the coals are low in inertinite 85 in localities with a dominance of angiosperm pollen the relative abundance of eu ulminite b and densinite is greatest whereas in the ones with a dominantly coniferous pollen assemblage eu ulminite a is the most prominent maceral these observations suggest as an immediate cause effect relationship an at least partial dependance of present maceral content on floral precursors this in turn probably reflects a certain combination of depositional environment conditions ph eh temperature etc that likely controlled the plant community and the preservation of vegetal matter the depositional environment of coals from the basal part of the ravenscrag formation contrasts sharply with that of the amphitheatre the ravenscrag coals formed within a low energy stable floodplain environment palynological and coal maceral profiles for the basal ravenscrag formation coal which spans the cretaceous tertiary boundary indicates that the environment of deposition progressed from an open canopied swamp forest with areas of open water through a phase of low lying to open water swamps with herbaceous pterophytic vegetation to at least locally raised bogs the change in coal petrography across the cretaceous tertiary boundary is shown to be relatively minor in comparison to subsequent changes in coal petrography in the earliest paleocene and to changes that occur in the palynological assemblages across the boundary interval

holocene evolution of the western orinoco delta venezuela the pristine nature of the orinoco delta of eastern venezuela provides unique opportunities to study the geologic processes and environments of a major tropical delta remote sensing images shallow cores and radiocarbon dating of organic remains form the basis for describing deltaic environments and interpreting the holocene history of the delta the orinoco delta can be subdivided into two major sectors the southeast sector is dominated by the rio grande the principal distributary and complex networks of anastomosing fluvial and tidal channels the abundance of siliciclastic deposits suggests that fluvial processes such as overbank flooding strongly influence this part of the delta in contrast the northwest sector is represented by few major distributaries and overbank sedimentation is less widespread relative to the southeast sector peat is abundant and occurs in herbaceous and forested swamps that are individually up to 200 km 2 in area northwest directed littoral currents transport large volumes of suspended sediment and produce prominent mudcapes along the northwest coast mapping of surface sediments vegetation and major landforms identified four principal geomorphic systems within the western delta plain 1 distributary channels 2 interdistributary flood basins 3 fluvial marine transitional environments and 4 marine influenced coastal environments coring and radiocarbon dating of deltaic deposits show that the northern delta shoreline has prograded 20 30 km during the late holocene sea level highstand progradation has been accomplished by a combination of distributary avulsion and mudcape progradation this style of deltaic progradation differs markedly from other deltas such as the mississippi where distributary avulsion leads to coastal land loss rather than shoreline progradation the key difference is that the orinoco delta coastal zone receives prodigious amounts of sediment from northwest moving littoral currents that transport sediment from as far away as the amazon system 1600 km late holocene progradation of the delta has decreased delta plain gradients increased water levels and minimized overbank flooding and siliciclastic sedimentation in the northwest sector these conditions coupled with large amounts of direct precipitation have led to widespread peat accumulation in interdistributary basins because peat forming environments cover up to 5000 km 2 of the delta plain the orinoco may be an excellent analogue for interpreting ancient deltaic peat deposits

radiocarbon chronology of lake bonneville eastern great basin usa abstract lake bonneville occupied a series of connected topographically closed structural basins in the eastern great basin from about 30 ka to 12 ka the following synthesis of lake bonneville history is based on a critical evaluation of the stratigraphic and geomorphic contexts of 83 radiocarbon ages of a variety of samples including wood charcoal dispersed organic matter mollusk shells and tufa the lake began to rise from levels close to average holocene levels after about 28 ka by 22 ka it had transgressed approximately 100 m between 22 and 20 ka it regressed about 45 m in the stansbury oscillation and the stansbury shoreline was formed transgression after 20 ka proceeded in two phases a rapid phase from 20 to 18 ka and a slower phase from 18 to 15 ka the lake overflowed intermittently at its highest level the bonneville shoreline from about 15 to 14 5 ka then catastrophically dropped 100 m during the bonneville flood to the level of the provo shoreline which it occupied until about 14 ka subsequent closed basin regression was rapid and complete by 12 ka and was followed by a modest transgression to form the gilbert shoreline between 10 9 and 10 3 ka the lake bonneville record is an accurate proxy of the changing water balance in the bonneville basin during the late pleistocene although the nature of the climatic changes during this period are still uncertain

lake bonneville fluctuations and global climate change lake bonneville the largest late pleistocene closed basin lake in the north american great basin fluctuated widely in response to changes in climate the geochemistry and mineralogy of endogenic calcium carbonate deposited in deep water and stratigraphic studies of shore zone deposits provide evidence of millennial scale lake level fluctuations that had amplitudes of about 50 m between 30 and 10 ka falling lake events occurred at 21 18 5 19 17 5 16 15 5 14 13 and 10 ka radiocarbon years synchronously with the terminations of heinrich events h1 and h2 and other smaller scale iceberg rafting events a b c and younger dryas in the north atlantic ocean the lake bonneville results thus support other climate records that suggest that late pleistocene millennial scale climate change was global in extent the size and shape of the northern hemisphere ice sheets which determined the mean positions of storm tracks may have been the primary control on late pleistocene water budgets of great basin lakes

limiting age for the provo shoreline of lake bonneville abstract pluvial lake bonneville features a prominent shoreline at the provo level which has been interpreted as having formed during a period of threshold stabilized overflow the timing of provo shoreline development is important for paleoclimate interpretations and for inferences on geomorphic process rates estimates for the timing of the shoreline formation based on radiocarbon measurements from gastropod shells are from approximately 18 to 15 cal ka one key radiocarbon age on plant fragments from swan lake which formed in the threshold spillway after overflow ceased has been taken as a young limiting age the conventional age of 12090 300 14c when calibrated at 2 has large uncertainty 13375 15103 cal bp we report six new ams radiocarbon ages recovered from new swan lake sediment cores a twig near the base of lacustrine muds was dated at 11 615 40 14c yr 13 350 to 13 560 cal bp age determinations on roots in that interval and deeper in the core are somewhat younger these ages limit the last overflow of the provo stand to earlier than 13 5 cal ka bp consistent with the younger bound of the imprecise age reported by bright if conservative interpretations of sedimentation rates for the thick well sorted sand interval below the lacustrine muds are correct and landscape change that resulted in damming of swan lake is accounted for cessation of flow probably occurred before 14 5 cal ka bp

petrology and organic geochemistry of peat samples from a raised bog in kalimantan borneo abstract two peat cores from the margin and centre of a tropical raised bog from the sebangau river near palangkaraya in kalimantan indonesia were investigated to illustrate the changes during peatification using coal petrographic and organic geochemical techniques these methods included a maceral analysis on polished peat blocks under reflected white and blue light excitation using the brown coal maceral nomenclature soxhlet extraction was carried out and an estimate of the humic composition was undertaken on the residues gc and gc ms analysis of the alkane and aromatic fractions were also made to identify biomarkers present in the peat results of this study show that peats from the margin of the raised bog were more decomposed than peats from the centre tissue content extract yield and alkaline insoluble acid soluble humic acid fraction support these results not only were there differences between the two locations of the peat cores but also differences arose with respect to depth in both cores the basal peats were more decomposed than the peats from the upper layers this was a result of their differing environments of deposition i e the basal peats were deposited under relative mesotrophic conditions and a more seasonal climate whereas the peats from the upper layers were deposited under acidic and oligotrophic conditions the biomarker composition of the alkane fraction included long chain n alkanes from n c 23 to n c 35 with an odd over even predominance and interestingly n alkanes from n c 36 to n c 40 with an even over odd predominance peaking at n c 38 pentacyclic triterpenoids were mainly represented by 17 21 h homohopane and hop 17 21 ene biomarkers in the aromatic fraction included polyaromatic triterpenoids derived from and amyrin