glass from the cretaceous tertiary boundary in haiti tektite like glasses preserved at the cretaceous tertiary boundary at beloc in haiti provide clear evidence of an impact event the glass composition suggests that the impact occurred on a continental shelf region generating a silica rich glass with chemical composition that reflects the melting of continental crustal rocks and a calcium rich glass produced by the fusion of marl sediments these findings indicate that catastrophic release to the atmosphere of 1015 moles of c02 from vaporized marl occurred during the impact

a new cretaceous tertiary boundary site at flaxbourne river new zealand biostratigraphy and geochemistry abstract an exceptionally complete rock sequence across the cretaceous tertiary k t boundary has been discovered near the flaxboume river marlborough province south island new zealand the boundary is marked by a large ir anomaly 21 ng g on a decalcified basis with an integrated abundance of 134 ng cm2 after correction for background above the boundary there is a 30 cm transition zone in which a few cretaceous foraminiferal taxa such as hedbergella monmouthensis and guembelitria cretacea survived though with reduced abundance and size only ca 1 2 to 1 4 of normal apparently reflecting environmental stresses inaa and icp analyses show that in addition to ir the boundary clay is also enriched in cr and ni mainly from meteoritic material and as co cu sb and zn from terrestrial sources volcanic sources even when scaled to the 10 7 km 3 volume of the deccan basalts fail by three orders of magnitude to account for the ir and as at the k t boundary and by even larger factors for sb zn cu etc comparison of our data with those from six other k t boundary sites shows that the zn sb as sb and zn as ratios generally fall between crustal and oceanic values suggesting contributions from both sources mass balance calculations show that as and sb could be derived from only 300 500 m of ocean water or also from modest amounts 20 36 g cm 2 of average crustal rock copper and zn on the other hand can only be derived from crustal or mantle rock 5 15 g cm 2 presumably impact ejecta such an amount of ejecta is fairly close to the global fallout of boundary clay 2 5 g cm 2

environmental perturbations caused by the impacts of asteroids and comets we review the major impact associated mechanisms proposed to cause extinctions at the cretaceous tertiary geological boundary we then discuss how the proposed extinction mechanisms may relate to the environmental consequences of asteroid and comet impacts in general our chief goal is to provide relatively simple prescriptions for evaluating the importance of impacting objects over a range of energies and compositions but we also stress that there are many uncertainties we conclude that impacts with energies less than about 10 mt are a negligible hazard for impacts with energies above 10 mt and below about 104 mt i e impact frequencies less than one in 6 104 years corresponding to comets and asteroids with diameters smaller than about 400 m and 650 m respectively blast damage earthquakes and fires should be important on a scale of 104 or 105 km which corresponds to the area damaged in many natural disasters of recent history however tsunami excited by marine impacts could be more damaging flooding a kilometer of coastal plain over entire ocean basins in the energy range of 104 105 mt intervals up to 3 105 years corresponding to comets and asteroids with diameters up to 850 m and 1 4 km respectively water vapor injections and ozone loss become significant on the global scale in our nominal model such an impact does not inject enough submicrometer dust into the stratosphere to produce major adverse effects but if a higher fraction of pulverized rock than we think likely reaches the stratosphere stratospheric dust causing global cooling would also be important in this energy range thus 105 mt is a lower limit where damage might occur beyond the experience of human history the energy range from 105 to 106 mt intervals up to 2 106 years corresponding to comets and asteroids up to 1 8 and 3 km diameter is transitional between regional and global effects stratospheric dust sulfates released from within impacting asteroids and soot from extensive wild fires sparked by thermal radiation from the impact can produce climatologically significant global optical depths of the order of 10 moreover the ejecta plumes of these impacts may produce enough no from shock heated air to destroy the ozone shield between 106 and 107 mt intervals up to 1 5 107 years corresponding to comets and asteroids up to 4 and 6 5 km diameter dust and sulfate levels would be high enough to reduce light levels below those necessary for photosynthesis ballistic ejecta reentering the atmosphere as shooting stars would set fires over regions exceeding 107 km and the resulting smoke would reduce light levels even further at energies above 107 mt blast and earthquake damage reach the regional scale 106 km tsunami cresting to 100 m and flooding 20 km inland could sweep the coastal zones of one of the world s ocean basins fires would be set globally light levels may drop so low from the smoke dust and sulfate as to make vision impossible at energies approaching 109 mt 108 years the ocean surface waters may be acidified globally by sulfur from the interiors of comets and asteroids the cretaceous tertiary impact in particular struck evaporate substrates that very likely generated a dense widespread sulfate aerosol layer with consequent climatic effects the combination of all of these physical effects would surely represent a devastating stress on the global biosphere

sanidine spherules at the cretaceous tertiary boundary indicate a large impact event the hypothesis that a catastrophic impact of an extraterrestrial body caused the terminal cretaceous mass extinctions of dinosaurs planktonic foraminfera and other species is now accepted as respectable following the discovery of a worldwide iridium enrichment in the cretaceous tertiary k t boundary clay1 5 in the basal lamina of the k t boundary clay of caravaca spain 7 numerous spherules were discovered composed of finely crystallized almost pure k feldspar in the structural state of high sanidine it is concluded here that these spherules solidified from a melt and were probably derived from the impacting body this poses problems as high k values are not reported from bulk analyses of meteorites6 the k feldspar phenocrysts reported in some iron meteorites23 suggest the body may have been a metal sulphide silicate planetesimal a cometary body is suggested as an alternative

the pre quaternary history of fire abstract although evidence for land vegetation comes from the silurian and maybe even earlier the first record of fossil charcoal fusain is from the late devonian for this period there are only one or two isolated records not until the early carboniferous is there a record of extensive charcoal deposits mainly preserved in near shore clastic sediments which provide evidence of significant and widespread wildfires by the late carboniferous charcoal was common or abundant in a wide range of facies including tropical wetland peats wildfire played an important role in shaping the environment at this time the latest palaeozoic and early mesozoic records of charcoal are fewer whereas important deposits of late mesozoic age are found worldwide the occurrence of charcoal at the cretaceous tertiary boundary has been highlighted as evidence for a global fire following a meteorite impact but this interpretation is questionable charcoal has been widely reported from tertiary sediments and its appearance in the quaternary and recent is not solely as a result of human impact through the past 400 million years there have been major changes in atmospheric oxygen levels that affected fire intensity and frequency fire systems thus have a long history and their impact on shaping the environment is assessed

the cold climate origin of inertinite rich gondwana coals abstract in the inertinite rich permian coals of australian there occurs a close association between inertodetrinite and alginite of a kind which has been generally overlooked in the past the association is believed to be a consequence of the environment of deposition and especially the climate which is inferred to have been one of wet cool summers and freezing winters the inertodetrinite formed by drying out of a gelified homogenised precursor the algae lived at the periodically desiccated surface of the accumulating peat much of the evidence for these conclusions has come from the combined use of light microscopy and transmission electron microscopy

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

proximal cretaceous tertiary boundary impact deposits in the caribbean trace element isotopic and mineralogic studies indicate that the proposed impact at the cretaceous tertiary k t boundary occurred in an ocean basin although a minor component of continental material is required the size and abundance of shocked minerals and the restricted geographic occurrence of the ejecta layer and impact wave deposits suggest an impact between the americas coarse boundary sediments at sites 151 and 153 in the colombian basin and 5 to 450 meter thick boundary sediments in cuba may be deposits of a giant wave produced by a nearby oceanic impact on the southern peninsula of haiti a approximately 50 centimeter thick ejecta layer occurs at the k t boundary this ejecta layer is approximately 25 times as thick as that at any known k t site and suggests an impact site within approximately 1000 kilometers seismic reflection profiles suggest that a buried approximately 300 km diameter candidate structure occurs in the colombian basin

the global stratigraphy of the cretaceous tertiary boundary impact ejecta the chicxulub crater ejecta stratigraphy is reviewed in the context of the stratigraphy of underlying and overlying rock sequences the ejecta sequence is regionally grouped in a thick polymict and monomict breccia sequences inside the crater and within 300 km from the rim of the crater known from drill holes in and close to the breater and exposures near the border of yucatan and belize b gulf of mexico region 2500 m from the crater with up to 9 m thick complex tsunami wave influenced tektite bearing sequences in shallow marine 500 m deep environments and tektite bearing decimeter thick gravity flow deposits in deep water sites c an intermediate region between 2500 and 4000 km from the crater where centimeter thick tektite bearing layers occur and d a global distal region with a millimeter thin ejecta layer the distal ejecta layer is characterized by sub millimeter sized microkrystites often rich in ni rich spinels and altered clinopyroxene wherever present the ejecta layers mark exactly the sudden mass mortality horizon of the k t boundary what exactly caused the mass mortality is still uncertain but it appears the main event leading to the k t mass extinctions

boltysh another end cretaceous impact the chixculub impact occurred at the cretaceous tertiary k t boundary and although several other late cretaceous and paleogene impact craters have at times been linked with the k t boundary isotope geochronology has demonstrated that all have significantly different ages the currently accepted age of the 24 km diameter boltysh crater a k ar whole rock age places it in the coniacian at 88 3 ma however comprehensive ar ar dating of a range of melt samples yields a mean age of 65 17 0 64 ma within errors of the k t boundary several of the fresh samples exhibit signs of excess argon but this seems to be concentrated in rapidly crystallized glass rich samples the ar ar age confirms an earlier fission track measurement and thus two dating techniques have yielded an age within errors of the k t boundary for this crater crucially although the ages of boltysh and chixculub are within errors they may not have formed synchronously craters of 24 km diameter occur much more commonly than impacts of chixculub dimensions but their proximity does raise the important question of how many impacts there might have been close to the k t boundary

microtektite like impact glass associated with the frasnian famennian boundary mass extinction abstract glass spherules of probable impact origin occur in the late devonian hony section in belgium they are found at the stratigraphic level of the frasnian famennian boundary which is marked by one of the largest mass extinctions in the phanerozoic the hony glass spherules are chemically identical to those previously described from the stratigraphically equivalent senzeille section located 90 km to the west southwest in contrast to the senzeille layer the age of the hony spherule layer is well constrained by conodont biostratigraphy the spherules have morphological and chemical characteristics similar to tektites and microtektites they have a broad range of chemical composition with generally high k2o na2o and al2o3 na2o k2o their water content is in the range measured for tektites and impact glasses small inclusions of lechatelierite may be present in the spherules these glass spherules are likely to be the product of an impact event that occurred at or very near the frasnian famennian boundary the target rock was probably a clay rich pelitic sediment intermixed with carbonates the 368 1 ma siljan ring crater sweden is the most likely impact site candidate the hony and senzeille glass spherules represent the first substantial evidence that an impact event may be linked to the frasnian famennian mass extinction

the relationship between coal petrography and depositional environments from selected coal basins in canada abstract this paper reviews current research in canada relating to the sedimentology of coal bearing sequences and the petrographic character of contained seams from selected intermontane and foreland basin settings the intermontane cumberland and stellarton basins of nova scotia contain westphalian coal bearing strata of different character coal seams that formed in fluvial dominated depositional environments of the springhill coalfield cumberland basin commonly brighten upward and laterally display distinct areal zones a piedmont zone formed by interfingering of mire and distal fan sheetflow deposits an inner mire zone largely devoid of partings and a riverine zone with large scale seam splits about multistorey sandstone bodies maceral based groundwater influence and vegetation indices combined with miospore analyses indicate that the peat precursors of the no 3 seam of the inner mire zone accumulated from a groundwater influenced rheotrophic to mesotrophic forest mire swamp fen both the gelification of lignin derived maceral precursors and the domination of mire vegetation by lycopsid trees reflect this groundwater influence coal that formed from the frequently flooded paleomires of the stellarton basin is generally dull microbanded and mineral rich the location of mires within the basin was largely determined by basin subsidence rates when subsidence rates were high mires developed around the margin of a central basin lake coal seams that formed from these mires e g mcleod seam thicken toward basin margins and grade into sapropelic shale near the basin centre petrographic analyses of the mcleod seam suggest development from limnic to wet forest swamp conditions and a return to a limnic environment at the top of the seam thick coal e g foord seam developed near the basin centre during periods of lower subsidence rates and grades into red beds and paleosols toward the basin margin the foord seam of the basin centre is characterized by low mineral matter contents and a high proportion of degraded vitrinite macerals in the central parts of the seam interpreted to reflect prolonged peat accumulation with very limited clastic input the top and the base of the seam in contrast were subjected to significant clastic input as indicated by microbanding associated with significant amounts of detrital minerals and macerals coal seams of the lower cretaceous gates formation in the western canada basin formed in depositional settings ranging from coastal swamps strandplains to the upper delta plain strandplain coal is characterized by great lateral continuity and substantial thickness whereas coal of the upper delta plain is thin and discontinous the strandplain coal is characterized by variable lithotype sequences oscillatory brightening up dulling up maceral based facies parameters indicate a wide range of mire facies for these lithotype successions open moor forest moor herbaceous and or shrubby marshes and slightly raised mires results from megafossil and phyteral analyses suggest that the coastal plain mires were dominated by taxodiaceous conifers whereas ferns angiosperms and herbaceous lycopods are thought to have occupied the more marshy and or marginal stream lake side environments

observations on the nature and origin of fusain abstract evidence for a wildfire origin of fusain is examined charcoal produced by natural fires and artificial charring resembles fossil fusain both in physical size and shape and in optical reflectance artificially charred leaves and naturally burnt wood are illustrated using the sem reflectance studies on modern charcoals suggest that much semifusinite may be produced by pyrolysis the ecological implications of a wildfire origin of fusain are discussed and it is concluded that fires have been a feature of terrestrial ecosystems from at least the late devonian

tectonic evolution of low grade metamorphosed rocks of the cretaceous shimanto accretionary complex central japan abstract we reconstructed the tectono metamorphic evolution of the low grade metamorphosed cretaceous shimanto accretionary complex in the kanto mountains central japan based on radiolarian fossils metamorphic temperatures derived from illite crystallinity analysis and timing of metamorphism based on illite k ar dating the accretionary age of the kobotoke group is turonian to maastrichtian 66 94 ma based on radiolarian fossils illite crystallinity data indicate metamorphic temperatures of approximately 300 c the illite k ar ages constrain the timing of metamorphism to the middle eocene around 40 ma combining our results and previous study we defined two types of low grade metamorphism within cretaceous shimanto accretionary complex of the kanto mountains the early metamorphism in excess of 300 c was related to the uplift of the sambagawa metamorphic rocks in turn associated with the subduction of the kula pacific ridge during the late cretaceous 65 75 ma this metamorphism is recorded in the otaki group within the northernmost part of the complex in the kanto mountains subsequent to the subduction of the kula pacific ridge a later period of metamorphism recorded in the kobotoke group is characterized by the thermal effects of the subduction of the young hot pacific plate during the middle eocene the effect of the early metamorphism occurred synchronously 500 km along the trench from southwest to central japan the later metamorphism occurred at 50 ma in kyushu and shikoku of southwest japan and at 40 ma in the kanto mountains of central japan this difference in the timing of metamorphism between southwest and central japan is explained by the northward migration of the young hot pacific plate

terrestrial carbon and nitrogen isotopic ratios from cretaceous tertiary boundary nanodiamonds one hypothesis for the origin of the nanometer size diamonds found at the cretaceous tertiary k t boundary is that they are relict interstellar diamond grains carried by a postulated asteroid the 13 c 12 c and 15 n 14 n ratios of the diamonds from two sites in north america however show that the diamonds are two component mixtures differing in carbon and nitrogen isotopic composition and nitrogen abundance samples from a site from italy show no evidence for either diamond component all the isotopic signatures obtained from the k t boundary are material well distinguished from known meteoritic diamonds particularly the fine grain interstellar diamonds that are abundant in primitive chondrites the k t diamonds were most likely produced during the impact of the asteroid with earth or in a plasma resulting from the associated fireball

magnitude and timing of peat to coal compaction the peat to coal transition is commonly assumed to be accompanied by compaction that decreases the thickness of the organic deposit to values of 10 or less of the original peat thickness decompaction modeling using such values for coal seams in contact with penecontemporaneous channel sandstones leads to impossible depositional geometries for the sandstones which have a final thickness that is 90 of their original thickness similarly decompaction modeling of the fragments of organic material within channel lags using the assumed large peat compaction value results in the destruction of the associated sedimentary structures such as trough cross beds dinosaur tracks in the roofs of coal mines show a shallow depth of penetration and a preservation of foot morphology that is not possible unless the peat the animals walked upon was very firm these data confirm the macroscopic observations from coal balls that the compaction associated with the peat to coal transformation is minimal equally important the data also show that most of the compaction occurs essentially at the surface and not at the depths where coalification takes place

phyterals of humic coals in the u s s r abstract the results of a study of plant remains found in coals of devonian to neogene age which were studied mainly by the method of phyteral analysis are presented most of phyterals discussed and illustrated in this paper are from coal basins in the u s s r however a discussion of occurrences of phyterals in coal basins worldwide is also included middle devonian coals contain fungal remains and phyterals of the enigmatic vascular plant orestovia the most characteristic phyterals of euramerican carboniferous coals are the following periderm of stems and rhizomes of lepidophytes wood and cortex of gymnosperms of uncertain systematic position rachides of pteridosperms and fructifications of spore bearing plants vitrinized phyterals predominate over fusinized phyterals in carboniferous coals in permian coals of gondwana and angarida vitrinized and fusinized woods bark tissues and leaves of pycnoxylic gymnosperms are characteristic phyterals differences in phyteral composition of early and late permian coals indicate that phyterals from vitrinized leaves were more dominant in late permian coals triassic coals rarely contain phyterals of known affinity jurassic and early cretaceous coals are similar in phyteral composition periderm and cork of conifers and ginkgoaceous plants are typical phyterals phyterals of vitrinized and fusinized gymnospermous wood played a significant role in these coals as well leaf phyterals usually compose layers of the paper and fall of leaves coals distinctive characteristics of phyteral composition of cenozoic coals are 1 wide distribution of lignitized woods 2 constant presence of well identified and very specific root remains 3 high content of plant attritus 4 commonly occurring and distinctive fungal phyterals further study of coal phyterals is suggested for correlation of coal seams and coal bearing strata and for the prediction of coal quality

siliceous plankton bloom in the earliest tertiary of marlborough new zealand in marked contrast to mass extinctions and productivity crises in much of the world oceans at the cretaceous tertiary boundary siliceous plankton thrived in earliest paleocene seas of marlborough new zealand five bathyal sections show no radiolarian mass extinction across a well defined cretaceous tertiary boundary but instead an abrupt increase of diatoms relative to radiolarians a general increase in both groups and an influx of spumellarians a pronounced increase in modal quartz and sio2 within a 9 25 m thick basal paleocene interval indicates high biosiliceous productivity the silica being derived primarily from diatoms enhanced upwelling in response to climatic cooling or more efficient nutrient cycling related to sea level changes may explain this plankton bloom over the first 1 m y of the tertiary

the stratigraphic distribution of inertinite abstract the paper presents the results of an investigation into the stratigraphic distribution of inertinite in humic coals ranging from the silurian to the neogene periods this range equals the time span during which both land plants and atmospheric oxygen evolved the survey is based on a literature study of inertinite in coals covering a variety of depositional environments and climates in all continents the inertinite percentages listed in this paper have been arranged in stratigraphic order they are the mean values based on mineral free whole coal compilations maceral compositions listed in the literature for individual subsections have been averaged to represent complete coal seams beds although this might not have been always possible due to some ambiguity in the published record moreover not all of the published and unpublished information could be used because of poor sample description obscure geographic origin or insufficient stratigraphic information the results show that there have been times in the geological past e g during the late permian in which coals were particularly rich in inertinite compared with other times e g during much of the late tertiary in which many coals contained very little inertinite occasionally such primary global trends were modulated by a diffuse distribution of inertinite percentages that correspond to differences in climate depositional settings e g active orogenic margins versus tectonically inactive shelf margins and other local or regional variations although various mechanisms for the generation of inertinite have been proposed in the past the overall pattern in its stratigraphic distribution supports the notion of incomplete combustion as the main source of inertinite in coal this points to secular variations in the atmospheric oxygen content as an explanation for the global changes in the inertinite distribution while differential subsidence and climatically influenced reaction rates governed regional and local variations in inertinite percentages

inertinite rich tertiary coals from the zeya bureya basin far eastern russia selected tertiary coals from the zeya buryea basin far eastern russia were investigated for aspects of their coal type rank depositional environment and post depositional history the coals have been examined in outcrop lithotype logging microscopically maceral reflectance and fluorescence and geochemically proximate analysis two laterally extensive coal bearing horizons occur one of palaeocene age and the other of early miocene age the palaeocene coals were investigated in active open cut mines at raichikhinsk and yerkovtsi and the early miocene deposit in an abandoned open cut mine at cergeyevka palaeocene coals at raichikhinsk and yerkovtsi were indistinguishable from each other macroscopically microscopically and geochemically the deposits were sufficiently coalified that brightness logging could be undertaken dull coals with numerous fusainous wisps were dominant four dulling up sequences which represent stacked peat deposits were observed at raichikhinsk at yerkovtsi only a small section of the middle of the seam which was mostly dull and muddy coal was investigated petrographically these coals were dominated by inertinite group macerals which is unusual in non gondwanan coals and rare in the tertiary rank classification was problematic with volatile matter vm content of vitrain daf macroscopic appearance and microscopic textures suggesting subbituminous b rank but carbon content moisture content and specific energy indicating a lignite rank notwithstanding complications of rank estimates of the maximum range burial depths were calculated taking the vm daf content of vitrain as 48 burial depth estimates range from 900 m for a high geothermal gradient and long heating time to a maximum of 3300 m for a low geothermal gradient and short heating time these estimates are maxima as the coal rank may be lower than implied by the vm the cergeyevka deposit is a soft brown coal limited sampling of the upper most portion indicated a high moisture content 75 daf and an unusual hydrogen rich geochemistry lack of identifiable liptinites using either reflected light or fluorescence microscopy suggested a significant bituminite component otherwise the coals appear to be typical for the tertiary an estimate of 125 m maximum burial depth was obtained using the bed moisture content of the coal which is around the present burial depth comparison of present day thicknesses with inferred burial depths suggests that at least 500 m of section is missing between the palaeocene coals and the early miocene coals palaeoenvironmental considerations suggest that fire played a significant role in the accumulation of the peats at raichikhinsk and yerkovtsi at cergeyevka peat accumulation ended by drowning of the mire two tuff beds were recognised within the seam at raichikhinsk and one in the seam at yerkovtsi correlation of the tuff beds is uncertain but they should prove useful in regional coal seam correlation and interpreting coal depositional environments geochemical analysis by xrf was complicated by high loss on ignition loi values despite extensive alteration an acid igneous source is implied from the presence of free quartz and tio2 al2o3 ratios of 0 02 to 0 05

provenance of mineral phases in the cretaceous tertiary boundary sediments exposed on the southern peninsula of haiti abstract acid insoluble mineral residua of tektite bearing cretaceous tertiary boundary sediments in the beloc formation of haiti contain abundant shocked quartz and lesser amounts of shocked plagioclase the shocked quartz grains typically have 2 or 3 sets of planar deformation features although grains with up to 15 sets were observed the proportion of shocked quartz in the boundary sediments increases with stratigraphic height at least 70 11 of the quartz grains are shocked in the uppermost stratigraphic interval the proportion of shocked quartz throughout the boundary sediments indicates that these grains were excavated primarily from crystalline silicate units which may have been covered with a small amount of porous quartz bearing sediments polyhedral and moderately sutured margins in shocked polycrystalline quartz grains the size of the crystal units in these grains and the presence of shocked plagioclase indicate these ejecta components were excavated from a target with continental affinities containing quartzites or metaquartzites and a sialic metamorphic and or igneous component other evidence suggests the target may also have contained a significant amount of calcium carbonate and or sulfate the large size and amount of shocked quartz grains deposited in haiti indicate the crater from which they were excavated was produced in the proto caribbean region

orbital tuning and correlation of 1 7 m y of continuous carbon storage in an early miocene peatland peatland is an important terrestrial carbon reservoir that contains 25 of soil carbon and accounts for 25 38 of natural methane emissions most of this carbon is contained in postglacial boreal peat our understandingof the carbon cycle within this reservoir and its links to the atmosphere is therefore restricted to periods of 1 m y spectral analysis of varying lignite color reveals that 120 m of early miocene lignite from the gippsland basin australia contains a 1 7 m y record of orbitally paced climate oscillations dominated by the response to obliquity use of the regular orbital signal indicates that the average long term rate of peatland carbon accumulation recorded in the lignite is 27 5 g m 2 yr 1 this rate is constant over periods of 100 k y and is independent of shorter term 10 k y fluctuations in climate and hydrology matching the lignite record to the theoretical insolation curve indicates that the lignite formed between 22 5 and 20 8 ma contemporaneous long term changes in lignite color and the 1 3 c 1 2 c ratios of marine foraminifera may relate to changing peatland methane flux and thus point to a link between terrestrial and marine carbon dynamics

global fire at the cretaceous tertiary boundary cretaceous tertiary k t boundary clays from five sites in europe and new zealand are 102 104 fold enriched in elemental c mainly soot which is isotopically uniform and apparently comes from a single global fire the soot layer coincides with the ir layer suggesting that the fire was triggered by meteorite impact and began before the ejecta had settled

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

sequence stratigraphic analysis and the origins of tertiary brown coal lithotypes latrobe valley gippsland basin australia abstract the methods of sequence analysis have been applied to the onshore gippsland basin and in particular to the latrobe valley group coal measures which include up to five coal seams each exceeding 100 m in thickness the methods appear to provide new depositional concepts to the evolution of these seams and the development of coal lithotypes in the eastern half of the latrobe valley evidence for marine transgressions into the coal measures are recorded in most of the interseam sediment splits by the presence of contained foraminifera and dinoflagellates to the west inland these splits pinch out into continuous coal however they can be followed westwards as enhanced organic sulphur levels along sharply defined boundaries between light coal lithotypes below and dark coal lithotypes above the dark lithotype immediately overlying each of these boundaries contains the highest sulphur value and warmer climate pollen assemblages sluiter et al 1995 this volume colorimeter and lithotype logging strongly supports an upwards lightening cyclicity to coal colour at 12 20 m intervals through the approx 100 m thick seams with cycle boundaries defined at sharp planar to undulating surfaces the lightening upward lithotype cycles together with their unique boundary conditions i e enhanced organic sulphur levels warm climatic indicators and laterally equivalent marine clay splits are interpreted as parasequences and parasequence boundaries respectively each major coal seam can comprise up to five parasequences and is interpreted to represent deposition during an outbuilding high stand systems tract at one of several maximum periods of tertiary coastal onlap the top of each major seam shows evidence of truncation erosion on a regional scale and these surfaces are interpreted to represent the sequence boundaries the major seams are usually conformably underlain by marine clays and extensive aquifer sands being deposits of the late transgressive systems tracts the low stands and early parts of the transgressive systems tracts appear not to be represented in the latrobe valley due to its more basin margin location but are probably present down dip in the equivalent marine facies of the seaspray group stratigraphic correlation of the sequence boundaries identified in the coal measures to the adjacent internationally dated marine seaspray group provides a basis for chronostratigraphic correlation of the coal successions to the coastal onlap charts of haq et al exon mesozoic cenozoic chronostratigraphic chart version january 1988 and august 1989 from this dating it appears that each major seam is confined to high stands of third order eustatic cycles it therefore follows that the lithotype cycles parasequences that comprise each seam are related to fourth order eustatic cycles by analogy all the coal cycles may have developed under subtropical conditions as ombrogenous forested peat swamps in a similar manner to the holocene though tropical swamps of indonesia

volcanic eruptions on mid ocean ridges new evidence from the superfast spreading east pacific rise 17 19 s uniform sediment cover were recovered from lava that buries older faulted terrain the boundary in lava composition coincides with a change in depth to the top of an axial magma lens seismic reflector consistent with magmas from two separate reservoirs being erupted in the same event chemical compositions from throughout the area indicate that lavas with identical compositions can be emplaced in separate volcanic eruptions within individual segments a comparison of our results to global data on submarine mid ocean ridge eruptions suggests consistent dependencies of erupted volume activated fissure lengths and chemical heterogeneity with spreading rate consistent with expected eruptive characteristics from ridges with contrasting thermal properties and magma reservoir depths index terms 3035 marine geology and geophysics midocean ridge processes 8414 volcanology eruption mechanisms 8439 volcanology physics and chemistry of magma bodies 3655 mineralogy and petrology major element composition keywords lava flow chemical heterogeneity erupted volume lava morphology side scan sonar

morokweng south africa a large impact structure of jurassic cretaceous boundary age geophysical petrographical and geochemical data indicate the presence of a large impact structure in the area around morokweng northwest province south africa possibly up to 340 km in diameter drill cores from the center of the structure show a thick layer of impact melt rocks with high abundances of cr ni co and the platinum group elements consistent with the presence of up to 5 of a chondritic component ion probe dating of zircons extracted from the impact melt yielded a 206 pb 238 u age of 146 2 1 5 ma and a 208 pb 232 th age of 144 7 1 9 ma these are indistinguishable from the age of the jurassic cretaceous boundary following the identification of the chicxulub impact structure of cretaceous tertiary boundary age the discovery of a second large impact structure at a previously established major chronostratigraphic boundary strengthens suggestions that large impact events have been major factors in the evolution of the earth

comparing maceral ratios from tropical peatlands with assumptions from coal studies do classic coal petrographic interpretation methods have to be discarded petrographic investigations of tropical peat deposits from the tasek bera basin malaysia show that petrographic methods can contribute valuable information about paleoecological settings of mire deposits comparing modern peat forming environments and the pre maceral composition of peat samples allows the reconstruction of paleoecological conditions such as floral composition fires microbial activity etc and gives insight into paleodepositional environments in the past maceral ratios of coals have been used to interpret paleodepositional settings of coal deposits such a procedure assumes that coal texture and coal maceral composition are dictated solely by the depositional environment and thus different depositional environments should be clearly discriminated based on maceral ratios in the modern peat deposits of tasek bera divergent petrographic results occur in similar depositional environments hence poor correlation occurs between the petrography the degree of decomposition and the depositional environment furthermore from the time of peat deposition peat is subject to considerable alteration during subsequent diagenesis preservation of structured and strongly altered material such as inertinite gelified material or funginite is favoured and results in biased coal maceral compositions because maceral indexes in modern peat studies are of little utility in the reconstruction of paleoenvironmental settings it follows that coal maceral indexes should not be utilized in the future to interpret paleodepositional environments of coals

sandstone composition of the upper jurassic emuerhe formation from the mohe basin china the sandstone composition analysis carried out on the samples from three different sections western section middle section and eastern section of the upper jurassic emuerhe formation in the mohe basin northeastern china reveals that the okhotsk orogenic belt and the ergun massif basement are the source areas for the emuerhe formation the source area of the western section and the a segment of the middle section is the okhotsk orogenic belt the tectonic attributes of the okhotsk orogenic belt are those of a dissected arc the transportation distance of clastic rocks from these sections gradually lengthened and the uplift rate of the okhotsk orogenic belt gradually increased the source area of the eastern section and the b segment of the middle section is the ergun massif basement compared with the okhotsk orogenic belt the tectonic attributes and uplift rate of the ergun massif basement are different from the former the attributes of the ergun massif basement are those of basement uplift the transportation distance of clastic rocks from the eastern section and the b segment of the middle section gradually shortened and the uplift rate of the ergun massif basement gradually decreased these conclusions are consistent with the characteristics of a foreland basin thus we can draw the conclusion that the mohe basin belongs to the foreland basin

elemental anomalies at the cretaceous tertiary boundary woodside creek new zealand iridium and 26 other elements were determined in shale from the cretaceous tertiary boundary at the locus classicus for iridium anomalies at woodside creek new zealand iridium gold copper cobalt chromium nickel arsenic molybdenum and iron were enriched in the basal 2 millimeters of the 8 millimeter shale parting as compared with the rest of the stratigraphic column no other shale partings in the column had anomalous concentrations of any element when the data were expressed on a carbonate free basis the boundary material showed striking compositional similarities with the stevns klint danish boundary shale elemental concentrations were in general much higher in the new zealand material than in nonboundary shales from elsewhere in the world the high concentration of iridium 153 nanograms per gram in the basal layer of the boundary together with the enrichment of other siderophile elements supports the idea of an extraterrestrial source for much of the material the iridium gold ratio of 2 1 is also in accordance with such a source the iridium content of the basal layer is higher than for any other marine boundary shale obtained on land the integrated iridium value is 187 nanograms per square centimeter of boundary surface

altered spherules of impact melt and associated relic glass from the k t boundary sediments in haiti partially to wholly altered glass spherules produced by impact induced shock melting have been found in the k t boundary sediments of haiti which also contain grains of shocked quartz the relic glass has an approximately dacitic composition and although grossly similar in composition to most previously described tektite glasses it is slightly enriched in ca and slightly depleted in si suggesting the haitian glass was produced either from a target with a greater fraction of carbonate and anhydrite lithologies and fewer silicate units than the targets from which most other tektites were produced and or from one with a significant mafic component the composition of the glass can best be reconciled with a continental margin terrane consistent with studies of shocked mineral phases reported elsewhere the thickness of the deposit in which the impact spherules occur indicates the source of the ejecta was in the proto caribbean region

diamonds from the iridium rich k t boundary layer at arroyo el mimbral tamaulipas mexico diamonds up to 30 m in size were found in the iridium rich layer from the k t boundary site at arroyo el mimbral and the spherule bed from arroyo el penon northeastern mexico stepped heating experiments indicate two or more isotopically distinct diamond components with carbon isotopic compositions characteristic of a mixture of carbon sources the diamonds crystal form is cubic not the hexagonal polymorph of diamond lonsdaleite which has been used previously to infer formation due to shock transformation of graphite the size crystallography and mineralogic associations of k t diamonds are similar to those of impact produced diamonds from the ries crater in germany where both shock transformation of graphite and a mode of formation by condensation from a vapor plume have been inferred the discovery of impact produced diamonds in association with high ir contents for these sediments supports their impact origin k t age and the inference that their source was from the buried impact crater of chicxulub on the yucatan peninsula mexico

a major fire event recorded in the mesofossils and petrology of the late permian lower whybrow coal seam sydney basin australia abstract petrographic and mesofossil analyses of plies from the late permian lower whybrow coal new south wales australia have revealed a significant fire event in both the swamp setting and the hinterland the fire event is characterised by a change in the maceral composition the seam during this interval being dominated by inertinite especially semifusinite following the fire event the mineral matter content of the coal increases this may be the result of increased run off and erosion in the hinterland due to destruction of vegetation this major fire event is also reflected in a change in the vegetation as represented by the mesofossil content of the seam prior to the fire event the seam contains abundant bisaccate taeniate pollen sporangia and seed like bodies of possible glossopterid affinity these are lost at the ply in which the fire event is recorded though seed like bodies become important again later the fire event also corresponds to a change in the megaspore content of the coal a new species appearing perhaps as a result of hydrological change following this major fire event a mineral rich ply was deposited which contains miospore masses of spores from fern like plants possibly representing a re colonisation event by rhizomorphs after vegetation death this evidence for a major fire and its implications for the origin of inertinites leads to the conclusion that throughout this and other permian gondwana coals fire was an integral part of the temperate mid high latitude southern hemisphere swamp ecosystem

chicxulub crater a possible cretaceous tertiary boundary impact crater on the yucatan peninsula mexico we suggest that a buried 180 km diameter circular structure on the yucatan peninsula mexico is an impact crater its size and shape are revealed by magnetic and gravity field anomalies as well as by oil wells drilled inside and near the structure the stratigraphy of the crater includes a sequence of andesitic igneous rocks and glass interbedded with and overlain by breccias that contain evidence of shock metamorphism the andesitic rocks have chemical and isotopic compositions similar to those of tektites found in cretaceous tertiary k t ejecta a 90 m thick k t boundary breccia also containing evidence of shock metamorphism is present 50 km outside the crater s edge this breccia probably represents the crater s ejecta blanket the age of the crater is not precisely known but a k t boundary age is indicated because the crater is in a thick carbonate sequence shock produced co2 from the impact may have caused a severe greenhouse warming

beyond methane towards a theory for the paleocene eocene thermal maximum abstract extreme global warmth and an abrupt negative carbon isotope excursion during the paleocene eocene thermal maximum petm have been attributed to a massive release of methane hydrate from sediments on the continental slope 1 however the magnitude of the warming 5 to 6 c 2 3 and rise in the depth of the ccd 2 km 4 indicate that the size of the carbon addition was larger than can be accounted for by the methane hydrate hypothesis additional carbon sources associated with methane hydrate release e g pore water venting and turbidite oxidation are also insufficient we find that the oxidation of at least 5000 gt c of organic carbon is the most likely explanation for the observed geochemical and climatic changes during the petm for which there are several potential mechanisms production of thermogenic ch4 and co2 during contact metamorphism associated with the intrusion of a large igneous province into organic rich sediments 5 is capable of supplying large amounts of carbon but is inconsistent with the lack of extensive carbon loss in metamorphosed sediments as well as the abrupt onset and termination of carbon release during the petm a global conflagration of paleocene peatlands 6 highlights a large terrestrial carbon source but massive carbon release by fire seems unlikely as it would require that all peatlands burn at once and then for only 10 to 30 ky in addition this hypothesis requires an order of magnitude increase in the amount of carbon stored in peat the isolation of a large epicontinental seaway by tectonic uplift associated with volcanism or continental collision followed by desiccation and bacterial respiration of the aerated organic matter is another potential mechanism for the rapid release of large amounts of co2 in addition to the oxidation of the underlying marine sediments the desiccation of a major epicontinental seaway would remove a large source of moisture for the continental interior resulting in the desiccation and bacterial oxidation of adjacent terrestrial wetlands

stratigraphy sedimentology and palaeoecology of the dinosaur bearing kundur section zeya bureya basin amur region far eastern russia since 1990 the kundur locality amur region far eastern russia has yielded a rich dinosaur fauna the main fossil site occurs along a road section with a nearly continuous exposure of continental sediments of the kundur formation and the tsagayan group udurchukan and bureya formations the sedimentary environment of the kundur formation evolves from lacustrine to wetland settings the succession of megafloras discovered in this formation confirms the sedimentological data the tsagayan group beds were deposited in an alluvial environment of the gravel meandering type the dinosaur fossils are restricted to the udurchukan formation scarce and eroded bones can be found within channel deposits whereas abundant and well preserved specimens including sub complete skeletons have been discovered in diamicts these massive unsorted strata represent the deposits of ancient sediment gravity flows that originated from the uplifted areas at the borders of the zeya bureya basin these gravity flows assured the concentration of dinosaur bones and carcasses as well as their quick burial such taphonomic conditions allowed the preservation of sub complete hadrosaurid skeletons unearthed at the kundur site palaeobotanical data indicate a subtropical climate during the deposition of the kundur and udurchukan formations several elements in the composition of the kundur vertebrate fauna suggest a strong influence of the north american late cretaceous vertebrate communities the abundance of corythosaur like lambeosaurines the probable presence of a nodosaurid dinosaur and of a eucosmodontid or microcosmodontid multituberculate a late maastrichtian age is tentatively proposed for the dinosaur bearing sediments in amur region by comparison with the information collected in the western interior basin of north america as it is also observed in the latter area important floristic changes diminution of angiosperm pollens and predominance of modern families and the disappearance of dinosaurs mark the end of the maastrichtian age in the amur region late maastrichtian dinosaur localities from amur region are dominated by lambeosaurines whereas these dinosaurs apparently disappeared from western north america long before the iridium horizon that defines the k p boundary this local disappearance is therefore probably due to ecological factors rather than indicating a gradual extinction of the dinosaurs long before the k p boundary

lithotype maceral composition and variation as correlated with paleo wetland environments gates formation northeastern british columbia canada abstract lithotype samples collected from mid albian gates formation coal seams in northeastern british columbia were analysed in order to gain a better understanding of coal facies variation compositional boundaries between lithotypes are gradational from bright to dull coals there is a progressive decrease in vitrinite and increase in inertinite liptinite is negligible

reevaluation of siderophile element abundances and ratios across the cretaceous paleogene k pg boundary implications for the nature of the projectile abstract the discovery over 30 years ago at gubbio italy and caravaca spain of an enrichment in the concentrations of iridium ir and the other platinum group elements pge by up to four orders of magnitude irmax 0 10 87 ng g compared to average continental crustal background levels remains one of the most important discoveries in the earth sciences since then similar anomalies have been detected in more than 120 cretaceous paleogene k pg boundary sites worldwide highly elevated ir and other siderophile element abundances in roughly chondritic ratios are considered strong indicators for the presence of a meteoritic contribution in impact related lithologies melt rocks impact ejecta material etc delivered when an extraterrestrial object strikes earth the presented work adds 113 unpublished pge analyses of 38 k pg sections worldwide to the existing literature the analytical protocol relied on for this purpose consisted of a combination of a nickel sulfide fire assay pre concentration technique and subsequent trace metal determination via inductively coupled plasma mass spectrometry icp ms through repeated determination of key siderophile elements i e cr co ni and pge the importance of sampling nugget effects and analytical methodologies applied becomes more apparent even more critically these analytical effects are superimposed by the local syn and post depositional conditions that have affected the pristine meteoritic signature of the k pg impactor including potential fractionation during vaporization and condensation dissimilar pge carrier phases terrestrial pge input sedimentation rate reworking diagenesis bioturbation and chemical diffusion while chondrite normalized pge patterns of individual sites appear relatively flat i e chondritic strong variations in siderophile element content and inter element ratios exist between k pg locations inter laboratory measurements and replicate analyses hampering a precise projectile identification using highly siderophile elements only when considering improved databases of siderophile element concentrations in meteorites in combination with linear regression analysis to calculate inter element ratios from a large suite of ejecta deposit sites the nature of the k pg projectile can be resolved application of this methodology to an extensive data set of continental and marine sites very proximal to distal to the chicxulub impact structure supports a carbonaceous chondritic impactor type cm or co

mineralogic evidence for an impact event at the cretaceous tertiary boundary a thin claystone layer found in nonmarine rocks at the palynological cretaceous tertiary boundary in eastern montana contains an anomalously high value of iridium the nonclay fraction is mostly quartz with minor feldspar and some of these grains display planar features these planar features are related to specific crystallographic directions in the quartz lattice the shocked quartz grains also exhibit asterism and have lowered refractive indices all these mineralogical features are characteristic of shock metamorphism and are compelling evidence that the shocked grains are the product of a high velocity impact between a large extraterrestrial body and the earth the shocked minerals represent silicic target material injected into the stratosphere by the impact of the projectile

geochemistry and petrography of the taupiri and kupakupa coal seams waikato coal measures eocene new zealand abstract geochemical and conventional petrographic techniques have been used to characterise variation within and between the eocene taupiri and kupakupa coal seams in new zealand both seams have a macroscopically bright lustre but the taupiri is dominated by non banded coal in contrast to portions of the kupakupa which contain large 1 3 cm thick vitrain bands microscopically these bands contribute the bulk of the humotelinite preserved tissue found in both coals the kupakupa seam contains higher proportions approx 20 of humotelinite than the taupiri approx 10 which contains higher concentrations of liptinite and sclerotinite both seams show a general decrease in humotelinite upwards in the seam although inorganic partings can modify that general trend especially in the kupakupa in all three splits of the taupiri eugelinite decreases upwards whilst detrogelinite proportions increase these petrographic attributes suggest that the taupiri palaeo peat was subjected to higher levels of degradation than the kupakupa coal geochemistry when interpreted in the context of seam geometry and stratigraphic relationships reveals a complex chemical history major element analyses supplemented by mineralogical analyses confirm previous work indicating a strong organic association for ca mg na fe and b these elements are more abundant in seams which are overlain by other coal seams indicating depletion by circulation of groundwater of surface origin for example na values in a split taupiri seam at maori farm 3 opencast vary across major sediment partings being highest in the lowermost coal interval si al ratios vary widely and commonly fall below the composition of kaolinite indicating breakdown of silicates and transport of silica and alumina in solution at the time of peat accumulation ti and p in whole coal fluctuate substantially and their present distribution also indicates mobility in solution there appears to be little association between elemental and maceral variation however there is a clear association in the kupakupa coal seam at the weavers opencast between p presence of organic partings and the degree of vitrain banding the highest concentrations of p are within and just below inorganic partings similarly the highest abundance of vitrain bands occur just above and or below partings although probably not causally related the increase in p and vitrain band abundance may be related to the same process that is flooding of the kupakupa palaeo mire with sediment laden waters a quicker burial from sediment loading and less aerobic degradation may have preserved the plant root material vitrain bands the p may have resulted either from the flood waters themselves or as residual p in buried plant material in either case immobilisation in insoluble form by reaction with al species is probable

spheroids at the cretaceous tertiary boundary are altered impact droplets of basaltic composition sand size spheroids of k feldspar in the cretaceous tertiary c t boundary clay at caravaca southern spain were interpreted by smit and klaver as having solidified from a melt resulting from the impact of a large extraterrestrial body sand size spheroids of k feldspar glauconite and magnetite quartz have been found in the c t boundary clay in northern italy and spheroids of k feldspar and pyrite were found in the boundary clay at deep sea drilling project site 465a in the central pacific these spheroids have textures similar to those of rapidly crystallized feldspar and mafic silicates they are interpreted as diagenetically altered microcrystalline spherules of basaltic composition produced by the impact of a large asteroid in an ocean basin at the end of the cretaceous they are analogous to the glassy microtektites produced by impacts on more siliceous target rocks 21 references 4 figures

siderophile rich magnetic spheroids from the cretaceous tertiary boundary in umbria italy the magnetic fraction of some cretaceous tertiary k t boundary sediments sampled at two locations in italy contains a spheroidal component which has retained some relict mineral textures and possibly mineral chemistry from the k t event the spheroids contain small crystals 1 50 m of magnetite in a highly altered groundmass these crystals are commonly skeletal indicating formation by rapid growth from a high temperature liquid variable concentrations of ni mg and al differing by at least a factor of 5 in the magnetite may also reflect a relict chemistry these spheroids contain higher concentrations of ir and probably other siderophiles than the bulk sediment and may have been an important carrier for these elements at 65 myr this discovery supports evidence for a major accretionary event at the end of the cretaceous

trajectories and distribution of material ejected from the chicxulub impact crater implications for postimpact wildfires 1 the trajectories of low and high energy ejecta from the chicxulub impact crater have been computed using a numerical code and compared with analyses of debris deposited in k t boundary sections these calculations indicate that low energy ejecta produces centimeter to meter thick deposits within 4000 km of the point of impact although its azimuthal distribution depends on the incident angle of the projectile with the surface of the earth the high energy ejecta or vapor plume rises through the atmosphere and isotropically expands at the top of the atmosphere the velocity of this ejecta increases as it rises approximately 12 of the high energy ejecta is lost because it reaches escape velocities while 25 of the material reaccretes within 2 hours 55 reaccretes within 8 hours and 85 reaccretes within 72 hours this ejecta is distributed globally but it is concentrated around the chicxulub impact site and at the antipode corresponding to india and the indian ocean 65 million years ago it is also slightly smeared in a longitudinal direction because of earth s rotation because this debris does not reaccrete all at once the collisional shock heating of the atmosphere will be drawn out over a period of a few days and will occur in pulses this could be an important factor when calculating postimpact chemical reactions in the stratosphere the calculations also indicate the ejecta would have ignited wildfires on several continents around the world although the distribution of those fires depends partly on the trajectory of the projectile

petrography and geochemistry of tonsteins from the 4th member of the upper triassic xujiahe formation in southern sichuan province china petrographic and geochemical studies on five layers of tonsteins from the 4th member of the upper triassic xujiahe formation t3xj4 in the southern sichuan province of china are presented in this paper the results suggest that these tonsteins were derived from synsedimentary acid volcanic ash fallout which was subsequently altered into relatively pure kaolinitic rocks through hydrolysis and diagenesis in a peat bog environment for definition of tonsteins refer to geol soc am spec pap 285 1993 the petrographic texture is mainly of dense and granular types with a subordinate crystalline type each tonstein layer is characterized by its unique petrographic texture mineral content and assemblage of lithophile elements which is related to the composition of its parent magma the trace element geochemistry of these tonsteins is elaborated in this paper which also suggests an origin as silicic volcanic ash fallout typically these features are relatively consistent within the same tonstein layer over a broad lateral extent and are characteristic of each specific tonstein layer therefore some tonsteins in this region serve as distinct marker beds for correlation of coal seams within the framework of regional chronostratigraphy

the melt rocks of the boltysh impact crater ukraine ussr the 100 12 m y 25 km diameter boltysh impact crater was formed in precambrian granites and granite gneisses of the ukrainian shield the crater deposits have undergone minimal post impact erosion and it is possible to study a complete vertical section of the underlying 200 m thick melt sheet the melt rocks as sampled in two drill holes can be subdivided into two major textural classes microcrystalline and glassy the microcrystalline melt rocks form an uppermost and two lowermost units with the glassy variety occupying the middle of the melt sheet the microcrystalline units contain 25 zoned plagioclase phenocrysts set in a microcrystalline matrix of intergrown alkali feldspar and quartz pyroxene has been replaced by sheet silicates mineral and lithic clasts make up 5 15 and show varying degrees of shock and resorption the glassy melt rocks are characterized by 10 30 zoned plagioclase and 5 10 orthopyroxene set in a fresh to partially devitrified glassy matrix clast content is 5 chemically the melt rocks are relatively homogeneous and correspond to a mixture of kirovograd granites and gneisses in the ratio of 5 to 1 with ni ir and cr showing slight enrichments over the target rocks there are minor differences in the fe2o3 feo ratio and the alkalis between the microcrystalline and glassy varieties the increase in matrix crystallinity at the upper and lower contacts is contrary to observations at other impact melt sheets where greater matrix crystallinity occurs in the interiors of the melt sheets one possible explanation is that the melt matrix was originally glassy throughout due to its high sio2 content and the microcrystalline matrix is the result of extensive devitrification involving minor alkali exchange with circulating ground waters

coeval 40ar 39ar ages of 65 0 million years ago from chicxulub crater melt rock and cretaceous tertiary boundary tektites 40 ar 39 ar dating of drill core samples of a glassy melt rock recovered from beneath a massive impact breccia contained within the 180 kilometer subsurface chicxulub crater in yucatan mexico has yielded well behaved incremental heating spectra with a mean plateau age of 64 98 0 05 million years ago ma the glassy melt rock of andesitic composition was obtained from core 9 1390 to 1393 meters in the chicxulub 1 well the age of the melt rock is virtually indistinguishable from 40 ar 39 ar ages obtained on tektite glass from beloc haiti and arroyo el mimbral northeastern mexico of 65 01 0 08 ma mean plateau age for beloc and 65 07 0 10 ma mean total fusion age for both sites the 40 ar 39 ar ages in conjunction with geochemical and petrological similarities strengthen the recent suggestion that the chicxulub structure is the source for the haitian and mexican tektites and is a viable candidate for the cretaceous tertiary boundary impact site

impact dust not the cause of the cretaceous tertiary mass extinction most of the 3 mm thick globally distributed chicxulub ejecta layer found at the cretaceous tertiary k t boundary was deposited as condensation droplets from the impact vapor plume a small fraction of this layer 14 g was submicrometer size dust the global mass and grain size distribution of the clastic debris indicate that stratospheric winds spread the debris from north america over the pacific ocean to europe and little debris reached high southern latitudes these findings indicate that the original k t impact extinction hypothesis the shutdown of photosynthesis by submicrometer size dust is not valid because it requires more than two orders of magnitude more fine dust than is estimated here furthermore estimates of future impact hazards which rely upon inaccurate impact dust loadings are greatly overstated

black carbon in paleocene eocene boundary sediments a test of biomass combustion as the petm trigger abstract several explanations have been proposed to account for the dramatic perturbation to earth s carbon cycle that led to extreme warming ocean acidification mass extinction and a major negative carbon isotope excursion cie at the paleocene eocene p e boundary one reason that the ultimate cause for this event remains ambiguous is the difficulty in directly testing these multiple hypotheses we conducted a test of one proposed mechanism the wildfire hypothesis that suggests that combustion of a significant fraction of abundant paleocene peat deposits within several thousand years could release enough co2 to earth s atmosphere to account for all of these observations soot and graphitic black carbon hereafter collectively referred to as gbc both combustion byproducts are widely distributed through smoke by subaerial combustion and are remarkably resistant to diagenetic degradation using samples provided by the ocean drilling program we measured gbc concentrations across the p e boundary in two important paleocene eocene thermal maximum petm sections to test a prediction of the wildfire hypothesis namely that the combustion of paleocene organic matter at the onset of the petm would produce a peak in sedimentary gbc in the bass river section new jersey margin gbc concentrations are uniformly high 121 358 ppm consistent with the core s continental margin setting but there is no evidence of increased gbc flux at the petm furthermore carbon isotopic ratios of gbc display the negative cie seen in petm organic matter indicating that this material was sourced from contemporaneous p e boundary biomass not geologically old carbon at site 1210 shatsky rise gbc concentrations were uniformly below our method s detection limit 0 5 ppm whereas the wildfire hypothesis would predict high gbc concentrations 3000 ppm accompanying the event together these data appear to refute but cannot conclusively rule out biomass burning as the cause for the petm event

the petrographic composition of world coals statistical results obtained from a literature survey with reference to coal type maceral composition abstract this paper presents a statistical study concerning the petrographic composition of world coals in terms of vitrinite v liptinite l and inertinite i composition a comparison between vli compositions of coals from different ages facies continents and countries territories was done north atlantic palaeozoic coals show an average petrografic composition of vli 70 12 18 while gondwana palaeozoic coals show vli 52 8 40 mesozoic coals from north atlantic territories also show a higher v content 74 than gondwana coals of the same age 65 and a lower i content 18 than gondwana 21 north atlantic and gondwana tertiary coals have similar vli compositions 81 10 9 and 82 8 10 respectively data from quaternary coals are only available for north atlantic and these show a vli composition of 88 6 6 considering the ece un classification 1990 of coals into vitric liptic fusic trimaceric i and trimaceric l a study was carried out to determine the percentages of all coals falling into each of these categories the amount of vitric coals increases constantly from palaeozoic 54 5 to quaternary 98 6 with values of 68 4 and 90 2 for mesozoic and tertiary coals respectively on the opposite the amounts of fusic and trimaceric i coals decrease in the same way liptic and trimaceric l coals do not show a regular variation based upon the results an attempt is made to establish an alternative boundary limit for fusic coals i 55 to the one proposed by ece un i 50 a new proposal for a change of terminology is presented

search for extractable fullerenes in clays from the cretaceous tertiary boundary of the woodside creek and flaxbourne river sites new zealand abstract when fullerenes were first discovered to form spontaneously in condensing carbon vapors kroto et al 1985 it was suggested that they might be widely distributed in the universe searches for fullerenes in meteorites see devries et al 1993 were unsuccessful but c 60 and c 70 were reported to occur on earth in samples of shungite a meta anthracite from a deposit near shunga russia buseck et al 1992 and in fulgurite a substance formed when lightning strikes certain soils or rocks daly et al 1993 the occurrence of fullerenes in shungite is particularly surprising since fullerene synthesis in the laboratory has always involved gas phase chemistry at temperatures over 1000 c such conditions may be attained during lightning strikes but shungite is believed to have formed from carbonaceous material creeping into fissures of a precambrian rock which metamorphosed under extreme pressures if the original carbonaceous material did not already contain fullerenes perhaps from wildfires they must have formed during the metamorphism by as yet unknown solid or liquid phase mechanisms

a 20 km diameter multi ringed impact structure in the north sea most craters found on earth are highly eroded poorly preserved and only exposed on land here we describe a multi ringed impact structure discovered in the north sea from the analysis of three dimensional seismic reflection data the structure is 20 km in diameter and has at least ten distinctive concentric rings located between 2 and 10 km from the crater centre the structure affects cretaceous chalk and jurassic shales and is well preserved below several hundred metres of post impact tertiary strata which constrains its age to be 60 65 myr old the formation of concentric ringed impact structures at this relatively small scale had not previously been thought possible especially on the terrestrial planets we have mapped the ring structures at a resolution of tens of metres both laterally and in depth and show that the rings are fault bounded graben structures similar to fault arrays formed in low strain rate detachment tectonic settings strata deeper than 500 m palaeodepth appear unfaulted and we infer that the concentric ring structures may have accommodated post impact extension towards the excavated crater through detachment on weak layers within the chalk

maceral and palynomorph facies from two tertiary peat forming environments in the powder river basin u s a abstract the differences between the depositional settings of the smith and anderson subbituminous coal beds paleocene central powder river basin u s a are interpreted on the basis of their petrographic composition and palynologic assemblages the smith coal bed is relatively thin m and has a high degree of thickness variation 0 5 m over short distances km the result of deposition in an anastomosed fluvial environment where numerous lakes and small channels limited the extent of peat deposits although plants related to the living genus glyptostrobus dominated the swamp peat forming plant communities contained mixes of ancestral species of platanus and ulmus as well as vegetation of lower stature such as spagnum some intervals within the coal bed contain anomalously high concentrations of cell walls humotelinite and cell fillings corpohuminite some of which came from locally abundant decay resistant pinaceae or pinaceous vegetation raised areas of the peat swamp characterized by sphagnum were also favorable for the accumulation of carbonized plant components inertinites because the peat of the anderson coal bed formed on top of thick 50 m sandstone bodies of an abandoned meander belt complex the coal bed is generally thicker 7 m and more widespread 15 km in extent than the smith coal bed the sands provided a relatively stable poorly compactable platform that was favorable to the growth of large arborescent vegetation such as the dominant ancestral glyptostrobus as well as ancestral nyssa carya and betulaceae in a well drained but moist swamp environment the stability of the peat forming environment resulted in a raised peat deposit of relatively uniform paleoflora and peat composition in the thicker areas of the anderson coal bed the upward increase in carbonized plant components indicates a progressively drier or better drained swamp environment intervals within the coal bed that overlie or are lateral to crevasse splay deposits contain a high concentration of pollen attributable to pterocarya and an absence of carbonized plant remains an indication that ancestral pterocarya preferred a water saturated environment close to the edge of the swamp where detrial influx occurred

sedimentary environment and diagenesis of the lower cretaceous chaswood formation southeastern canada the origin of kaolin rich mudstones abstract the lower cretaceous fluvial sandstone mudstone succession of the chaswood formation is the proximal equivalent of offshore deltaic rocks of the scotian basin that are reservoirs for producing gas fields this study interprets the mineralogical consequences of cretaceous weathering and early diagenesis in a 130 m core from the chaswood formation in order to better understand detrital and diagenetic minerals in equivalent rocks offshore mineralogy was determined by x ray diffraction electron microprobe analysis and scanning electron microscopy the rocks can be divided into five facies associations light gray mudstone dark gray mudstone silty mudstone and muddy sandstone sorted sandstone and conglomerate and paleosols facies transitions in coarser facies are related to deposition in and near fluvial channels in the mudstones they indicate an evolutionary progression from the dark gray mudstone facies association swamps and floodplain soils to mottled paleosols well drained oxisols and ultisols following syntectonic uplift facies transitions and regional distribution indicate that the light gray mudstone facies association formed from early diagenetic oxidation and alteration of the dark gray mudstone facies association probably by meteoric water principal minerals in mudstones are illite muscovite kaolinite vermiculite and quartz illite muscovite is of detrital origin but variations in abundance show that it has altered to kaolinite in the light gray mudstone facies association and in oxisols vermiculite developed from the weathering of biotite and is present in ultisols the earliest phase of sandstone cementation in reducing conditions in swamps and ponds produced siderite nodules and framboidal pyrite which were corroded and oxidized during subsequent development of paleosols kaolinite is an early cement coating quartz grains and as well crystallized pore filling booklets that was probably synchronous with the formation of the light gray mudstone facies association later illite and barite cement indicate a source of abundant k and ba from formation water this late diagenesis of sandstone took place when the chaswood formation was in continuity with the main scotian basin prior to oligocene uplift of the eastern scotian shelf findings of this study are applicable to other mid latitude cretaceous weathering and early diagenetic environments

coexisting altered glass and fe ni oxides at the cretaceous tertiary boundary stevns klint denmark direct evidence of meteorite impact abstract the cretaceous tertiary k t boundary at stevns klint denmark is noteworthy for its large ir anomaly that is taken as evidence of extraterrestrial components but the origin of the smectite in this marl has been variously interpreted to have a detrital meteorite impact or volcanic origin we have carried out scanning electron microscopy and transmission electron microscopy tem analytical electron microscopy observations of the impact and contiguous layers within the k t marl at stevns klint tem images show abundant smectite much of which occurs with layers curving around and grading into cores of nanometer scale glass shards the smectite composition is unusual in having both significant octahedral al and mg the glass and smectite major element compositions are similar and unique relative to glasses of terrestrial and extraterrestrial origin with the exception for one kind of glass at the k t boundary in haiti abundant 10 20 nm diameter iron oxides having as much as 10 ni and minor zn are intergrown with smectite we interpret these domains to be altered meteorite fragments which formed when impact glass was transformed to smectite the direct association of unique glass and meteorite fragments is unambiguous evidence for meteorite impact these data may imply fall out of globally distributed impact derived particles over an extended time period the relations imply that tem observations may be a powerful tool in detecting other impact events in the geological record

the dimensions of the chicxulub impact crater and impact melt sheet the chicxulub impact crater which is the principal source of impact debris in cretaceous tertiary boundary sediments is currently buried by a 1 km thick sequence of carbonate sediments because the crater is not exposed for direct scrutiny its size has remained uncertain and in particular estimates ranging from 100 to 300 km have been made on the basis of gravity and magnetic field data in this study the physical properties of the k t boundary impact ejecta and chicxulub impact melt sheet have been used to test the geophysical estimates of the impact crater s size on the basis of the measured thickness of impact ejecta in haiti and north america the calculated volume of the impact melt sheet and the chemical and isotopic composition of the melt sheet the chicxulub impact crater is inferred to be 180 km in diameter and to contain a 3 to 7 km thick melt sheet and breccia sequence within a centrally located 100 km diameter region that corresponds to the limits of the transient cavity

age and temperature of shock metamorphism of martian meteorite los angeles from u th he thermochronometry mineralogic features attributed to impact induced shock metamorphism are commonly observed in meteorites and terrestrial impact craters partly because the duration of shock metamorphism is very short constraining the timing and temperature of shock events has been problematic we measured u th he ages of single grains of merrillite and chlorapatite from the martian meteorite los angeles la merrillite and chlorapatite ages cluster at 3 28 6 0 15 ma 2s and 2 18 6 0 19 2s ma respectively the mean age of the merrillites which are larger than chlorapatites is indistinguishable from cosmic ray exposure ages 3 1 6 0 2 ma suggesting that impact induced shock metamorphism was coeval with ejection of the la precursor from mars to constrain the initial temperature of shock metamorphism in the la precursor body we modeled diffusive loss of he from merrillite as a function of diffusion domain size la precursor body size and ablation depth from these calculations we suggest that the metamorphic temperature of the shock event was higher than 450 8c these results support the idea that shock pressures of the martian meteorite shergotty were higher than 45 gpa as inferred from the presence of post stishovite sio2 polymorphs single grain u th he dating of phosphates may provide unique constraints on the timing and pressure temperature dynamics of shock metamorphism in a wide variety of extraterrestrial materials

geochemistry of impact glasses from the k t boundary in haiti relation to smectites and a new type of glass we have individually analyzed twelve black and seven yellow glasses from the k t boundary section at beloc haiti plus three smectite mantles around black glasses the main chemical differences between black and yellow glasses are higher s ca mg zn as br sb and au but lower k na and si abundances in the yellow glasses we have found high cao yellow glasses with low s contents 0 08 0 17 wt which may be explained by fusion of carbonate rich sediments microprobe studies of individual glasses show that the black glasses are very homogeneous in their composition at the 10 100 m level while yellow glasses show much more variability and different intra sample elemental correlations one of the black glasses has higher sio2 and k2o abundances but lower concentrations of all other major elements this suggests the existence of a third glass type which we have named the high si k variety hsi k glass the glass shows areas consisting of pure sio2 maybe lechatelierite and some schlieren with lower sio2 content the chemical composition indicates that the hsi k glass may have originated from melting of a sedimentary source rock such as shale or argillite severe changes in major and trace element composition occur during alteration of the glass as documented by analyses of adhering smectites the ree patterns in the glass are similar to average upper crust but the smectites exhibit much lower abundances and flat patterns not unlike the patterns observed in claystones at numerous k t boundary sites the suggestion that the chicxulub structure in yucatan may be the source crater for the k t impact glasses is not fully supported by the currently available data impact glasses and tektites are produced from the surface layers of their targets at chicxulub the target stratigraphy comprised mainly carbonates and evaporites although we cannot exclude chicxulub as a source the present data do not provide any firm chemical evidence for a connection we conclude however that the haiti glasses have formed by impact and have later undergone alteration by low temperature hydrothermal processes to produce clays the boundary claystones at k t boundary sites may very well be alteration products of these impact glasses

water content of glasses from the k t boundary haiti an indication of impact origin abstract the water content in seven glass samples from the k t boundary on haiti was determined by micro infrared spectrometry these glasses are thought to result from impact melting associated with the k t boundary impact although this interpretation is not unanimous the results of the water determinations 0 013 0 021 wt h2o show that the haiti glasses are water poor this is a common characteristic of impact glasses and tektites which usually have water contents below 0 05 wt and is not in agreement with interpretations that the haitian glasses are of volcanic origin

tem study of meteorite impact glass at new zealand cretaceous tertiary sites evidence for multiple impacts or differentiation during global circulation abstract study by transmission electron microscopy of samples from the cretaceous tertiary k t boundary clay at flaxbourne river and woodside creek new zealand has revealed the occurrence of nanometer sized meteorite impact derived glass the average glass composition is exceptionally ca rich and is distinct from other glass found on earth apart from glass inferred to be of impact origin at mexican and haitian k t sites the glass shards are partially altered to montmorillonite like smectite with the dominant interlayer cation ca reflecting the composition of the parent glass the data imply a heterogeneous global distribution in composition of k t boundary impact glass si rich and ca rich in mexico and haiti si rich in denmark and ca rich in new zealand this heterogeneous distribution may relate to dispersal processes similar to those used to account for the asymmetric distribution of clastic debris from the chicxulub impact site however recent discovery of an impact crater of k t boundary age in ukraine raises the possibility of impact clusters which produce material of heterogeneous composition

weathered spheroids in a cretaceous tertiary boundary shale at woodside creek new zealand three types of spheroids are found in the iridium rich shale layer at the cretaceous tertiary boundary at woodside creek south island new zealand two of the types a and b consist mainly of microcrystalline goethite whereas the third type f contains an appreciable quantity of hematite there is a strong correlation between the iridium content of the spheroids and their matrices and the concentrations of other siderophiles such as chromium cobalt iron and nickel a similar pattern was observed for the chalcophiles arsenic copper and zinc it is suggested that spheroids of types a and b are weathering products derived from diagenetic pyrite clumps and that type f which contains hematite represents a further stage in the weathering process and was derived from goethite the original pyritic material could have readily scavenged arsenic and other siderophiles from the sea water column under organic rich reducing conditions at the end of the cretaceous and the siderophiles including iridium could have been incorporated into the original meteoritic material it was concluded therefore that types a b and f spheroids are weathering products and do not represent original meteoritic material

tektite bearing deep water clastic unit at the cretaceous tertiary boundary in northeastern mexico the hypothesis of cretaceous tertiary k t boundary impact on yucatan mexico predicts that nearby sites should show evidence of proximal impact ejecta and disturbance by giant waves an outcrop along the arroyo el mimbral in northeastern mexico contains a layered clastic unit up to 3 m thick that interrupts a biostratigraphically complete pelagic marl sequence deposited at more than 400 m water depth the marls were found to be unsuitable for determining magnetostratigraphy but foraminiferal biostratigraphy places the clastic unit precisely at the k t boundary we interpret this clastic unit as the deposit of a megawave or tsunami produced by an extraterrestrial impact the elastic unit comprises three main subunits 1 the basal spherule bed contains glass in the form of tektites and microtektites glass spherules replaced by chlorite smectite and calcite and quartz grains showing probable shock features this bed is interpreted as a channelized deposit of proximal ejects 2 a set of lenticular massive graded laminated beds contains intraclasts and abundant plant debris and may be the result of megawave backwash that carried coarse debris from shallow parts of the continental margin into deeper water 3 at the top several thin ripple beds composed of fine sand are separated by clay drapes they are interpreted as deposits of oscillating currents perhaps a seiche an iridium anomaly 921 23 pg g is observed at the top of the ripple beds our observations at the mimbral locality support the hypothesis of a k t impact on nearby yucatan

isotopic comparison of k t boundary impact glass with melt rock from the chicxulub and manson impact structures the discussion of candidate source craters for the catastrophic impact that occurred at the boundary between the cretaceous and tertiary periods k t boundary has recently centred on two buried craters the chicxulub in mexico 200 km diameter and the manson in iowa 35 km diameter both of which have 40ar 39ar ages of 65 myr indistinguishable from that of impact glass spherules found in k t boundary sediments1 4 here we report the strontium neodymium and oxygen isotopic compositions of core samples of impact melt rock recovered from drill holes into both the chicxulub and manson craters and compare these with previously published isotopic data for impact glasses from the k t boundary of the beloc formation in haiti5 7 the chicxulub melt rocks are isotopically indistinguishable from the k t impact glass strongly supporting the proposition that chicxulub is a source crater for the k t catastrophe the manson melt rocks by contrast have a clearly different isotopic composition strongly suggesting that they are unrelated to the k t impact spherules

impacts in the round a well preserved crater has been identified deep beneath the bed of the north sea it may well have been produced by the impact of an extraterrestrial body some 60 million years ago

coal facies interpretations based on lithotype and maceral variations in lower cretaceous gates formation coals of western canada abstract maceral analyses of lithotype samples from lower cretaceous coal seams have been used to define compositional characteristics of the various lithotypes and to assess coal facies changes within the seams based on maceral and lithotype variations the mean petrographic compositions of the lithotypes show a general trend to decreasing vitrinite increasing inertinite and increasing mineral matter contents from the bright to dull varieties the bright lithotypes are considered to have been formed in wet and densely forested swamps whereas the banded lithotypes were formed under somewhat drier conditions within the dull lithotype two distinct types were recognized based on differences in petrographic composition and the occurrence or absence of facies diagnostic macerals it is suggested that these differences are due to formation in distinct mire facies under the influence of open moor or raised mire conditions the lithotype variations within the seams together with the data on their petrographic composition were used to define facies changes which occurred during accumulation of the peats three types of seam development are recognized a seams containing a high proportion of clastic beds indicative of frequent floodings of the swamps these seams are characterized by the dominance of oscillatory sequences of bright lithotypes and dulling upward sequences below clastic beds the brighter lithotypes were formed in forested swamps and fens whereas for the duller sequences influences of open moor conditions are indicated b seams containing only minor thin clastic beds indicating relative stability of water levels during formation of the peat these seams are characterized by the predominance of duller lithotypes with common repetitions of dulling upward sequences the dulling up sequences indicate transitions from wet and very wet forest swamps to drier conditions with lower tree density c transitional seams characterized by a few clastic beds these seams formed under intermediate conditions of stability in respect to flooding events the seams are characterized by the predominance of banded lithotypes dull lithotypes near partings and brightening and dulling up sequences the brightening up sequences represent transitions from dry forest swamp to wet and very wet forest swamps while a reverse trend is indicated for the dulling up sequences the overall petrographic characteristics of full seam sections indicate that the seams are in general relatively low in vitrinite and relatively rich in inertinite macerals liptinite content is negligible and mineral matter contents are low based on petrographic indices obtained from facies diagnostic macerals an accumulation of the ancient peats under prevailing wet to very wet forest swamps is suggested vicinity to more open moor conditions is indicated for one seam by the higher input of dispersed macerals

composition and grain size of an eocene coal bed in southeastern kalimantan indonesia abstract a study of an eocene coal in southeastern kalimantan indonesia shows a relationship between megascopically determined coal types and microscopically determined kinds and sizes of organic components microscopic examination of small 3 3 3 cm uncrushed chemically eteched block samples revealed that the coal was composed of plant parts and tissues set in a matrix of both finegrained particulate and amorphous material the material identified as plant parts consists of stems and roots with secondary growth leaves and one unknown plant structure however most components with cellular features cannot be identified as particular organs and are designated only as woody tissue and categorized by cell wall preservation that is well moderately or poorly preserved the particulate matrix is composed of cell wall fragments cell fillings resins spores algae and unidentifiable fluorescing fragments fungal remains are also present within the matrix and are the only oxidized material represented within the coal the amorphous matrix consists of unstructured at 400 humic gels and bitumen size measurement of the organic constituents shows that each particulate component possesses its own size distribution that approaches normality when transformed to a log2 o scale the size distribution of most of the plant parts is nearly symmetrical around a mean of 3 4 whereas means of the particulate matrix components are in the 8 9 size range differences in proportions of the plant parts and matrix components determine the character of the megascopic coal types bright banded coal types contain the greatest proportion of well preserved plant parts whereas the bright nonbanded and dull steel gray coal types contain fewer well preserved plant parts and consist mostly of plants parts with poor cell wall preservation hence the megascopically recognizable coal types appear to reflect differences in particle size arising from the degree of preservation of the plant material concentration of decay resistant resin and cell fillings in the non banded and dull coal types is believed to be a result of the loss of intact plant material an absence of larger 2 mm plant material in the eocene coal contrasts with the proportions indicated by data from a miocene lignite and a holocene peat both from kalimantan in the latter two deposits logs and roots 2 mm thick comprise as much as 10 15 the paucity of large plant material in the eocene coal is a function of the original peat forming vegetation the eocene coal formed from palms and ferns which are easily degraded through microbial activity in contrast the lignite and peat deposits accumulated from woody angiosperms that are relatively more resistant to decay however all three deposits have similar size distributions among the smaller