geologic and geomorphic controls of coal development in some tertiary rocky mountain basins usa abstract previous investigations have not well defined the controls on the development of minable coals in fluvial environments this study was undertaken to provide a clearer understanding of these controls particularly in of the lower tertiary coal bearing deposits of the raton and powder river basins in the rocky mountain region of the united states in this region large amounts of coals accumulated in swamps formed in the flow through fluvial systems that infilled these intermontane basins extrabasinal and intrabasinal tectonism partly controlled the stratigraphic and facies distributions of minable coal deposits the regional accumulation of coals was favored by the rapid basin subsidence coupled with minimal uplift of the source area during these events coals developed in swamps associated with anastomosed and meandering fluvial systems and alluvial fans the extensive and high rate of sediment input from these fluvial systems promoted the formation of ombrotrophic raised swamps which produced low ash and anomalously thick coals the petrology and palynology of these coals and the paleobotany of the associated sediments suggest that ombrotrophic raised swamps were common in the powder river basin where the climate during the early tertiary was paratropical the paleoecology of these swamps is identical to that of the modern ombrotrophic raised swamps of the baram and mahakam rivers of borneo

the ocean continent boundary off the western continental margin of iberia i crustal structure at 40 30 n summary the western continental margin of the iberian peninsula has the characteristics of a rifted non volcanic margin with half graben and tilted fault blocks seen in several places the ocean continent boundary ocb is therefore expected to be where thinned continental crust and oceanic crust are juxtaposed as at many similar margins worldwide it is particularly useful to locate the ocb off western iberia in order to constrain the pre rift fit of north america to iberia and by implication the shape of the proto bay of biscay the fit is only marginally constrained by sea floor spreading magnetic anomalies because anomaly 34 is believed to be far to the west of the ocb and it is even possible that all older oceanic crust was created during the cretaceous constant polarity interval the best way to distinguish oceanic crust from thinned continental crust appears to be the crustal seismic velocity structure therefore in 1986 a series of seismic refraction lines was shot parallel to and normal to the continental margin these lines enabled us to bracket the location of the ocb a further constraint on the location was obtained by modelling an east west magnetic profile which included the enigmatic j anomaly this anomaly can be explained as either just pre anomaly mo or as part of the cretaceous constant polarity interval depending on whether spreading began about 127 or after 118 myr ago respectively the evidence favours the former explanation lastly the depth to acoustic basement was contoured from a compilation of seismic reflection profiles this indicated a new fracture zone at 41 15 n which offsets the ocb a few key reflection profiles also suggest that the ocb can be identified by an abrupt landward step down in acoustic basement we conclude that the ocb in the eastern iberia abyssal plain lies between 12 10 and 12 30 w and has a trend just east of north this westerly location is consistent with recent estimates of the location of the ocb off the grand banks but brings into question the proposed location at about 11 w of the ocb in the tagus abyssal plain

the plant biostratigraphy of the cenozoic coal bearing formations in primorye russian far east abstract the paper presents a review of stratigraphy lithology and metallogeny of the paleogene and neogene coal basins from the primorye region of southeast russia the stratigraphic division of the studied sections is based on the abundant fossil plant material represented by leaf impressions and in lesser amounts fruit and seed fossils as well as detailed palynological analyses previously published u pb zircon and k ar bulk rock dates of volcanic and volcaniclastic rocks were also used as a result of this study five stages of cenozoic sedimentation are distinguished namely the late paleocene early eocene late eocene late oligocene and early miocene the early eocene late eocene late oligocene coal bearing units carry high concentrations of critical elements and include 3 of the 7 most germanium enriched coal deposits in the world in addition coals in the pushkino pavlovka vanchin rakovka and rettikhovka basins contain numerous occurrences of rare earth elements and yttrium gold occurs in the pavlovka vanchin rakovka krylovka sredne bikin and verkhne bikin basins uranium occurs in the pavlovka rakovka rettikhovka and glukhovka basins while zirconium and niobium occur in the pushkino basin

cenozoic deformation and mesozoic abandoned spreading centre in the tagus abyssal plain west of portugal results of a multichannel seismic survey the seismic stratigraphy of the sedimentary section that fills in the tagus abyssal plain is specified by means of new multichannel seismic data six sedimentary sequence units are identified these ranging from late jurassic to recent have been dated by extrapolation of deep sea drilling project dsdp and ocean drilling program odp drilling results and from sampling by dredging and submersible surveys based on this stratigraphic calibration and other geophysical data a geodynamic evolution can be established for the tagus abyssal plain faulting and folding in these sedimentary units clearly indicate that both the portuguese margin and the adjacent oceanic crust were deformed by a miocene compressive event an oxfordian kimmeridgian rifting in the lusitanian basin and on the portuguese margin may herald a sea floor spreading in the tagus abyssal plain the continent ocean boundary is marked by landward dipping reflectors similar to those observed along the canadian margin the oceanic structure of

ocean continent boundary in the iberia abyssal plain from multichannel seismic data abstract the ocean continent boundary of the west iberia margin is marked by a basement ridge trending n s four segments of this ridge are recognized each of them being progressively offset westward from 40 n to 43 n because the setting and seismic character of the ridge in the iberia abyssal plain are similar to those of the galicia margin ridge which is made of serpentinized peridotite we think that the southern segments of the ridge are also made of the same mantle material the segmentation of the ridge suggests that the northward propagation of the continental break up during the north atlantic opening in early cretaceous times was discontinuous each segment possibly corresponding to a propagation step east of the ridge the basement of the whole iberia abyssal plain consists of highly thinned continental crust locally resting on a seismic reflector that resembles the s reflector previously recognized off galicia by analogy with the galicia margin we propose that the tilted crustal blocks lay on serpentinized peridotite derived from the upper mantle the s reflector corresponding to the contact between crustal rocks and serpentinite

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

organic petrology of an early paleocene coal zone wabamun alberta palynology petrography and geochemistry abstract an interdisciplinary investigation of a section through the early paleocene ardley coal zone at wabamun alberta reveals that there are distinct vertical variations in the palynological petrographical and geochemical properties reflecting changes in the original depositional environment palynological assemblages are dominated by taxodiaceaepollenites hiatus revealing that the original coal accumulating mires were inhabited by taxodiaceous vegetation subordinate palynomorphs include varied gymnosperm pollen other than t hiatus laevigatosporites spp fern spores of polypodiaceous affinity stereisporites spp mosses including sphagnum and osmundacidites sp family osmundaceae coal petrography reveals that these coals are inertinite rich abundant fusinite pyrofusinite along with semi fusinite and inertodetrinite comprise up to 65 of the maceral assemblages huminite macerals are predominantly eu ulminite b with lesser eu ulminite a densinite and geli huminite gelified huminite lacking any remnant cell structure liptinite macerals include resinite sporinite and cutinite thinner stratigraphically lower seams at wabamun seams nos 6 3 consist predominantly of bright coal with high huminite contents palynofloral assemblages are comprised of t hiatus with few abundances of other palynomorphs suggesting that the original depositional environment was low lying dominated by taxodiaceous vegetation and frequently flooded as evidenced by numerous shale partings high ash contents and relatively high sulphur percentages the thick no 2 seam displays a distinct dulling up petrographic profile resulting from increasing inertinite contents coupled with increased abundances of stereisporites spp this may be evidence of localized ombrogeny within the original wabamun mires and may support a genetic relationship between stereisporites sp and inertodetrinite the no 1 seam consists of abundant fibrous fusain rich coal modes of origin of this fibrous coal include extreme oxidation due to prolonged drought and possibly forest fires elevated ash contents within the nos 1 and 2 seams may be a result of this oxidation of organic matter and concentration of the inorganics as well as airborne volcanic ash as evidenced by numerous bentonite bands within these coals sulphur contents are extremely low as low as 0 05 reflecting a terrestrial depositional environment

neogene through quaternary tectonic reactivation of sw iberian passive margin southwest portugal the gulf of cadiz and morocco are under the potential threat of natural hazards linked to seismicity and tsunami generation we report the results of two multi channel seismic mcs surveys carried out in 1992 and 1998 along the continental margin and oceanic crust of sw iberia this mcs data set shows the evidence of the compressional deformation which involves both the continental and the oceanic crust of the study area the area of deformation extends from the southern border of the tagus abyssal plain to the seine abyssal plain encompassing the continental margin of sw portugal most of the structures observed are probably related to a mid miocene phase of africa europe plate convergence in this paper we discuss the recent advances on the identification of the tectonic structures that are still active and that may generate great earthquakes and tsunamis the tectonic structures identified are located respectively at the guadalquivir bank along the eastern border of the horseshoe abyssal plain and along the southern continental slope of sw portugal

comparison of the petrography palynology and paleobotany of the stockton coal bed west virginia and implications for paleoenvironmental interpretations abstract the stockton coal bed middle pennsylvanian is a relatively high ash coal composed primarily of moderately thin banded sparsely thin banded and nonbanded coal splint and cannel coal comparisons of petrographic palynologic and paleobotanic data gathered from the same sample sets from a single column of the stockton coal bed indicate that compositional correspondences among the sets exist regardless of coal type some correspondences are believed to exist because of original plant constituents and others because of the paleoenvironment of peat formation using some combination of these data is critical when interpreting paleoenvironmental conditions because 1 a direct correspondence is lacking between many of the data and 2 each of the three data sets provides a unique and important perspective on the paleomire the stockton paleomire in the area of this study supported a diverse flora that consisted of both small and arboreous lycopsids small ferns and tree ferns calamites cordaites and pteridosperms there appear to have been two successions of lycospora spore dominated vitrinite rich liptinite poor peat formation which were followed by inertinite rich peat formation marked by a tree fern dominant spore assemblage and abundant unidentifiable plant tissues these are interpreted to be two water laden or topogenous peat formational stages followed by slightly domed better drained peat formation

petrography and palynology of the blue gem coal bed middle pennsylvanian southeastern kentucky usa petrographic and palynological trends in the blue gem coal bed middle pennsylvanian westphalian b breathitt formation a thin low sulfur low ash coal in southeastern kentucky were studied in order to establish a depositional model for the seam within the study area the coal bed averages 67 cm and has two distinct zones the lower and middle parts of the seam the lower 45 55 cm are enriched in well preserved vitrinite and are dominated by arborescent lycopods sphenopsids and tree ferns fusinite rich layers dominated by arborescent lycopods but also containing herbaceous lycopods and sphenopsids occur within the lower and middle parts of the seam the upper part of the seam the upper 15 25 cm is recognizable in the field and is distinct in that it contains a greater amount of degraded macerals and is characterized by high palynomorph diversity primarily by miospores that are associated with sphenopsids herbaceous lycopods and arborescent lycopods these data in conjunction with geochemical data available for the seam suggest that initially the peat swamp was fairly diverse and well nourished the base of the seam being characterized by a relatively diverse miospore assemblage and a slightly higher ash content following this initial planar stage the blue gem peat swamp was probably planar to slightly domed during accumulation of most of the lower and middle parts of the seam as suggested by the very low ash and sulfur contents the high telovitrinite content and the preponderance of arborescent lycopod spores in its final stages the peat swamp was domed and is characterized by a more diverse flora and greater levels of degradation of the peat constituents sulfur content of this seam is generally low 1 but can increase locally to 3 4 factors influencing sulfur content include the thickness and nature of the overburden shale versus sandstone and petrographic composition

palynofloral and organic characteristics of a miocene bog forest kalimantan indonesia palynological investigations of a 20 m thick miocene lignite from southeastern kalimantan indonesia reveal that there are distinct vertical variations in palynofloral characteristics three palynofloral zones likely represent large scale successional changes that were a product of long term ecological and depositional changes within the original mire all three zones are represented by palynofloras of both bog forest and mangrove affinity the abundance and diversity of these bog forest palynofloras accompanied by extremely low sulphur contents 0 4 suggests predominantly freshwater terrestrial deposition it is probable that the mangrove pollen is allochthonous and was transported into the mire by winds increasing relative abundances of mangrove pollen within the total palynofloral assemblage suggests encroachment of the mangrove swamp toward the bog forest pollen common and abundant within all assemblages includes that of species of the genera calophyllum melanorrhea and dactylocladus overall the vegetation that formed this miocene lignite is virtually identical to the present day peat forming vegetation of indonesia despite the vertical variations in vegetation within this miocene lignite as deduced from palynology coal petrographic investigations reveal that there is little variation in the organic characteristics within this seam petrographic analyses show that maceral assemblages are similar for most parts of this seam analyses of the plant parts and matrix illustrate that these characteristics are similar for much of the seam and that the composition and grain size of organic components are wholly comparable to results of similar analyses from a holocene mire this suggests that degradation processes during the miocene were similar to processes occurring in present day indonesian mires it further suggests that these degradation processes have homogenized the organic characteristics within the lignite despite original vegetational differences

response of a multi domain continental margin to compression study from seismic reflection refraction and numerical modelling in the tagus abyssal plain abstract the effects of the miocene through present compression in the tagus abyssal plain are mapped using the most up to date available to scientific community multi channel seismic reflection and refraction data correlation of the rift basin fault pattern with the deep crustal structure is presented along seismic line iam 5 four structural domains were recognized in the oceanic realm mild deformation concentrates in domain 1 adjacent to the tore madeira rise domain 2 is characterized by the absence of shortening structures except near the ocean continent transition oct implying that miocene deformation did not propagate into the abyssal plain in domain 3 we distinguish three sub domains sub domain 3a which coincides with the oct sub domain 3b which is a highly deformed adjacent continental segment and sub domain 3c the miocene tectonic inversion is mainly accommodated in domain 3 by oceanwards directed thrusting at the ocean continent transition and continentwards on the continental slope domain 4 corresponds to the non rifted continental margin where only minor extensional and shortening deformation structures are observed finite element numerical models address the response of the various domains to the miocene compression emphasizing the long wavelength differential vertical movements and the role of possible rheologic contrasts the concentration of the miocene deformation in the transitional zone tc which is the addition of sub domain 3a and part of 3b is a result of two main factors 1 focusing of compression in an already stressed region due to plate curvature and sediment loading and 2 rheological weakening we estimate that the frictional strength in the tc is reduced in 30 relative to the surrounding regions a model of compressive deformation propagation by means of horizontal impingement of the middle continental crust rift wedge and horizontal shearing on serpentinized mantle in the oceanic realm is presented this model is consistent with both the geological interpretation of seismic data and the results of numerical modelling

isometamorphic variations in the reflectance and fluorescence of vitrinite a key to depositional environment abstract petrographic investigations of serial ply samples from five high to medium volatile bituminous coal seams from australia 4 and canada 1 reveal substantial in seam variations in the reflectance and monochromatic microfluorescence intensities of the maceral subgroup telovitrinite the variations consist of one case of reflectance enhancement and fluorescence suppression and four cases of reflectance suppression and fluorescence enhancement the single case of reflectance enhancement and fluorescence suppression is due to the oxidation of the vitrinite nuclei at the sequence boundary between the bayswater and upper wynn seams in new south wales the four cases of reflectance suppression and fluorescence enhancement result from the syn and epigenetic absorption by the vitrinite nuclei of hydrogen donated by presumably anaerobic bacteria generated lipids two of the coals are marine influenced the liskeard seam from the bowen basin by combined syngenetic and epigenetic effects and the greta seam from the sydney basin mainly by epigenetic contact with sea water for both coals the results are strong vitrinite reflectance suppression and fluorescence enhancement the remaining two coals the bulli seam from the sydney basin and a coal seam from the gates formation in british columbia show moderate epigenetic effects on the optical properties of telovitrinite by fresh water in the bulli seam which was studied in two adjacent localities the reflectance suppression and fluorescence enhancement of telovitrinite are stronger under sandstone roof than under shale roof in some cases the epigenetic effects are superimposed on syngenetic telovitrinite reflectance and fluorescence variations resulting from the cogeneration and mixing of different telovitrinite precursors for example autochthonous roots and hypautochthonous or allochthonous shoots a measure of the degree of dispersal and mixing is the coefficient of variation of telovitrinite reflectance and or fluorescence this coefficient correlates well with detrital minerals and dispersed macerals e g inertodetrinite and to a lesser extent sporinite some comments are made on slitted so called pseudovitrinite which is regarded as a telovitrinite that was subjected to very weak post coalification desiccation and possibly oxidation without losing much of its thermoplastic properties

the ocean continent boundary off the western continental margin of iberia ii crustal structure in the tagus abyssal plain summary an 80 km long reversed seismic refraction line line 5 was shot over the tagus abyssal plain off portugal the main p wave reflected and refracted phases were modelled both for traveltime and amplitude the resulting p wave velocity depth model has the following features a an extremely thin crust of about 2 km b the absence of oceanic layer 3 and c very low upper mantle velocities between 7 6 and 7 9 km s this very unusual seismic velocity crustal structure is quite unlike thinned continental crust but is remarkably similar to the seismic crustal structures found at atlantic fracture zones and in particular to the structures found in profiles shot along the transform valley and near ridge transform intersections a magnetic anomaly chart seems to allow the possibility of several fracture zones one of which could intersect the centre of line 5 as an alternative to the fracture zone hypothesis we show that if the oceancontinent transition in the tagus abyssal plain is located at about 11 30 w in a symmetric position with respect to the ocean continent transition in the conjugate south newfoundland basin then magnetic anomalies can be modelled simply by assuming sea floor spreading west of 11 45 w at 10 mm yr beginning at m11 time 133 myr bp and blocks of rifted continental crust to the east the location of the proposed ocean continent transition in the tagus abyssal plain is marked by a well defined n s linear magnetic anomaly which is adjacent to the oldest sea floor spreading block east of the proposed ocean continent transition there is an increase in the depth to basement similar to that found east of the ocean continent transition in the iberia abyssal plain and elsewhere this model also allows us to explain why purdy s 1975 seismic refraction line a ar in the tagus abyssal plain cannot be interpreted as a conventional reversed pair because most of line a was shot over the ocean continent transition zone and most of line ar over thinned continental crust remarkably similar velocity depth structures to that under line 5 are found close to the ocean continent transition zone off the whole of western iberia in areas which show no clear evidence of fracture zones therefore it appears more likely that the seismic structure of line 5 is due to its proximity to the ocean continent transition than to a local association with a fracture zone and further that its structure is typical of this transition off the western margin of iberia we also suspect that the low upper mantle velocities associated with the ocean continent transition indicate the widespread occurrence of serpentinized peridotite

a debris flow deposit in alluvial coal bearing facies bighorn basin wyoming usa evidence for catastrophic termination of a mire abstract coal and clastic facies investigations of a paleocene coal bearing succession in the grass creek coal mine southwestern bighorn basin wyoming usa suggest that disruption of peat accumulation in recurrent mires was caused by the repetitive progradation of crevasse splays and ultimately by a catastrophic mass movement the mass movement represented by deposits of debris flow marked the termination of significant peat accumulation in the grass creek coal mine area megascopic and microscopic analyses of coal beds exposed along the mine highwalls suggest that these deposits developed in low lying mires as evidenced primarily by their ash yields and maceral composition disruption of peat accumulation in successive mires was caused by incursions of sediment into the mire environments termination by crevasse splay progradation is represented by coarsening upward successions of mudrock and tabular rooted sandstone which overlie coal beds in the lower part of the coal bearing interval a more rapid process of mire termination by mass movement is exemplified by a debris flow deposit of diamictite which overlies the uppermost coal bed at the top of the coal bearing interval the diamictite consists of a poorly sorted unstratified mixture of quartzite cobbles and pebbles embedded in a claystone rich or sandy mudstone matrix deposition of the diamictite may have taken place over a matter of weeks days or perhaps even hours by catastrophic flood thus reflecting an instantaneous process of mire termination coarse clastics and mud were transported from the southwest some 20 40 km as a viscous debris flow along stream courses from the ancestral washakie range to the grass creek area where the flow overrode a low lying mire and effectively terminated peat accumulation

sedimentology of fraser river delta peat deposits a modern analogue for some deltaic coals abstract on the recent lobe of the fraser river delta peat accumulation has actively occurred on the distal lower dilta plain the transition between upper and lower delta plains and the alluvial plain distal lower delta plain peats developed from widespread salt and brackish marshes and were not influenced appreciably by fluvial activity lateral development of the marsh facies were controlled by compaction and eustatic sea level rise the resulting thin discontinuous peat network contains numerous silty clay partings and high concentrations of sulphur freshwater marsh facies formed but were later in part eroded and altered by transgressing marine waters the peats overlie a thin fluvial fining upward sequence which in turn overlies a thick coarsening upward prodelta delta front succession lower delta plain upper delta plain peats initially developed from interdistributary brackish marshes and were later fluvially influenced as the delta prograded the thickest peats occur in areas where distributary channels were abandoned earliest sphagnum biofacies replace sedge grass dominated communities except along active channel margins where the sedge grass facies is intercalated with overbank and splay deposits the peats are underlain by a relatively thin sequence of fluvial deposits which in turn is underlain by a major coarsening upward delta front and pro delta sequence alluvial plain peats accumulated in back swamp environments of the flood plain earliest sedge clay and gyttjae peats developed over thin fining upward fluvial cycles or are interlaminated with fine grained flood deposits thickest accumulations occur where peat fills small avulsed flood channels overlying sedge grass and sphagnum biofacies are horizontally stratified and commonly have sharp boundaries with fine grained flood sediments at active channel margins however sedge grass peats are intercalated with natural levee deposits consisting of silty clay these levees reduce both the number and size of crevasse splay deposits coal originating from peats of the different environments of the fraser delta would vary markedly in character peats of the lower delta plain will form thin lenticular coal seams with numerous splits and have a high ash and sulphur content peats from the lower to upper delta plain will be laterally extensive and of variable thickness and quality basal portions of the seams will contain numerous splits and have a high sulphur content whereas upper portions will be of higher quality peats from the upper delta plain alluvial plain will form thick isolated and laterally restricted coal seams characterized by low ash and sulphur contents

kinematic evolution of the southern north atlantic implications for the formation of hyperextended rift systems we focus on the southern north atlantic rifted margins to investigate the partitioning and propagation of deformation in hyperextended rift systems using plate kinematic modeling the kinematic evolution of this area is well determined by oceanic magnetic anomalies after the cretaceous normal polarity superchron however the rift and early seafloor spreading evolution 200 83 ma remains highly disputed due to contentious interpretations of the j magnetic anomaly on the iberia newfoundland conjugate margins recent studies highlight that the j anomaly is probably polygenic related to polyphased magmatic events and therefore does not correspond to an isochron we present a new palinspastic restoration without using the j magnetic anomaly as the chron m0 we combine 3 d gravity inversion results with local structural stratigraphic and geochronological constraints on the rift deformation history the restoration of the southern north atlantic itself is not the primary aim of the study but rather is used as a method to investigate the spatiotemporal evolution of hyperextended rift systems we include continental microblocks that enable the partitioning of the deformation between different rift segments which is of particular importance for the evolution of the iberia eurasia plate boundary our modeling highlights the following 1 the segmentation of the iberia newfoundland rift system during continental crust thinning 2 the northward v shape propagation of mantle exhumation and seafloor spreading 3 the complex partitioning of deformation along the iberia eurasia plate boundary and 4 a three plate propagation model which implies transtension

morphotectonics of the gorringe bank summit eastern atlantic ocean based on high resolution multibeam bathymetry abstract high resolution swath bathymetry of the gorringe bank located along the europe africa obliquely convergent plate boundary offshore sw portugal allowed investigation of its shallow depth morphotectonic structure as a contribution to understanding the interplay of sea level changes and active deformation of the region dominant ene wsw to nne wsw and subordinate nw se trending morphologic alignments were mapped on the digital terrain model dtm built from multibeam data for both the gettysburg and ormonde summits of the bank based on appraisal of regional structural and seismological data the dominant and subordinate sets are interpreted to reflect dip slip to left oblique reverse faults and normal faults or dyke like joints respectively several terrace remnants were mapped on the dtm and were grouped into five orders at depths ranging from 40 to 120 m morphological features suggest that the terraces were formed in a coastal environment likely during middle late pleistocene sea level changes the terraces are probably polycyclic implying minor vertical tectonic motion however the whole terrace set except the deeper and younger one which was mainly shaped during the lgm lowstand is consistently up to 10 m lower at ormonde in the east relative to gettysburg in the west suggesting displacement across a nne ssw striking fault mapped in the saddle between the two seamounts the structure assemblage is argued to represent the shallow splay system of a crustal scale fault ramp underlying the bank the ene wsw reverse faults have a southward polarity and together with the overall northwest tilt of the bank point to displacement toward the horseshoe abyssal plain to the south at least at upper crustal levels

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

fungal origin of oxidised plant material in the palangkaraya peat deposit kalimantan tengah indonesia implications for inertinite formation in coal abstract the top 1 0 1 5 m of the 6 m thick palangkaraya peat deposit in indonesia is decaying aerobically and contains up to 22 oxidised plant material i e inertinite in contrast intervals below the level of water table fluctuation contain less than 5 oxidised material analysis of fungal remains in the peat show there is a coincident increase in total aggregate hyphal length a measure of fungal activity with the proportion of oxidised plant constituents macroscopically the top of the peat which contains the greatest proportion of oxidised material is black lacks wood fragments and would be classed as a sapric or sapric hemic peat oxidised material in the peat is predominantly epidermal cell walls of primary roots these cell walls are abnormally thickened and display a distinctive dentate structure in cross section the texture of the cell walls are either laminated or granular and often contains intercellular nodules these features together with the absence of charcoal layers in the peat suggest that oxidised constituents were derived from fungal alteration furthermore the coincident increase in fungal hyphal length with the proportion of oxidised material may suggest a causal link based on texture morphology and size the same types of oxidised plant material found in the palangkaraya peat deposit have been identified in coal beds of tertiary age from indonesia new zealand and the u s a this indicates similar fungal alteration occurred in the past and may account for some of the oxidised constituents found in coal if the palangkaraya mire is used as a model fungal alteration zones may be recognised in coals as relatively thick 0 5 2 0 m laterally extensive macroscopically dull coal

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

discovery of late jurassic fossils inside modern sediments at gorringe bank eastern atlantic ocean and some geological implications introductionin the horseshoe chain mainly com prising volcanic seamounts the gor ringe bank 36 n 11 w hereafterreferred to as gb is an exception because it consists of suboceanic man tle peridotites and gabbros the otherpeculiarity of this seamount is thegreat bathymetric gradient betweenthe summit of the bank at 30 m and the surrounding abyssal plains tagus and horseshoe at 5000 m fig 1 the gb is a n60 trendingridge 200 km long and 80 km wide with two summits the gettysburg inthe south west and the ormonde inthe north east beauzart et al 1979 the two summits separated by a deep 800 m saddle consist of igneousrock outcrops with very thin or absentsedimentary cover the rst exploration of the gb wasmade by the glomar challenger in1970 120 dsdp sites ryan et al 1973 this and some subsequentexplorations with manned submersi bles along the anks of the ridge in the0 3000 m bathymetric range auzen de et al 1978 lagabrielle andauzende 1982 and more recently atgreater depths girardeau et al 1998 have indicated that the gbrepresents a remarkable example of aseamount comprising lower oceaniccrust upper mantle rocks in december 2002 to january 2003duringthegorringe 2003 expedition on board r v urania nationalresearch council italy swath bathy metry seismo magnetic survey exten sive bottom samplings and some rov remotely operating vehicle dives overthe top of the gb were carried out dealteriis et al 2004 a further aim ofthe cruise was to study the bioclasticsediments recorded during previousexpeditions auzende et al 1978 gir ardeau et al 1998 at shallow depths the location and physiography of thegb guaranteed that these sedimentswere totally autochthonous anduncontaminated by other sources the only previous analyses availablefromthesesedimentswereprovidedbyavila and malaquias 2003 geological and stratigraphic resultsthe multibeam and geophysical sur vey extended to 500 m depth overboth summits revealed that gettys burg seamount has an almost subcir cular summit elongated n s for8 10 km the shelf area is somewhatconvex from 60 to 175 m at thecentre of the summit the igneousbasement crops out between depthsof 29 and 60 m the rocky outcropconsists of roughly n s trending rid ges consisting of foliated serpentinitesand gabbros completely surroundedby a blanket of bioclastic sands andgravels down to 140 m where a cleardepositional shelf break appears figs 1 and 2 pockets of these sandsare also hosted in the inter ridgedepressions sands consist of skeletalcalcareous algae forams bryozoansand molluscs the heterozoan associ ation james 1997 is dominated byforamol facies lees and buller 1972 over the entire shelf area withthe typical absence of allochthonousnon skeletal grains some exhumedearly pliocene foraminifers globoro talia margaritae bolli bermudez are also present in the ne fraction lithoclasts are generally rare andmainly consist of serpentinized ultra ma cs and gabbros samplings and rov observationscon rm that modern bioclastic mate rial is continually produced by thebenthic ecosystem that characterizesthis and other atlantic seamountsas temperate carbonate factories detailed bathymetry and subbottompro ling allow us to establish that theaverage thickness of this material doesnot exceed a few metres in the shelfareas and in the pockets theseabstract

the effects of clastic sedimentation on organic facies development within a tertiary subbituminous coal bed powder river basin montana u s a abstract the anderson dietz coal is a 25 m thick bed that splits eastward into three benches the anderson dietz 1 and dietz 2 each separated from the other by as much as 45 m of detrital sedimentary rocks petrographic and chemical analyses of the anderson and dietz 1 coal benches suggest that detrital sediments now lithified between the benches were introduced after the peat surface had subsided as a result of either fire or differential compaction of underlying sediments sediments associated with this event had a limited effect upon the quality of the anderson and dietz 1 coal benches ash yields and sulfur contents are elevated only at the very top and bottom of the benches in areas where the benches are not split sulfur content and maceral types indicating degradation increase only in a thin zone 1 m thick that is laterally equivalent to the split sediments however ash yields in this interval increase only slightly 2 5 this indicates that while little sedimentation occurred the peat which formed the coal was inundated by higher ph surface and ground water causing the degradation of plant material

structure and rifting evolution of the northern newfoundland basin from erable multichannel seismic reflection profiles across the southeastern margin of flemish cap we present the results from processing and interpreting five lines from the 1992 erable multichannel seismic reflection experiment extending from the southeastern margin of flemish cap into the northern newfoundland basin these profiles reveal significant along strike variations in the rifting styles experienced by flemish cap in the southwest a 100 km wide transition zone is identified between thinned continental crust and thin oceanic crust similar to the conjugate galicia bank and iberian margins this transition zone contains a section of deep basement adjacent to a series of shallower ridges and is interpreted as exhumed serpentinized mantle along strike towards the northeast this transition zone pinches out completely within 100 km and is replaced by thin oceanic crust directly adjacent to thinned continental crust by interpreting nearby seismic profiles and profiles on the conjugate margins using the same classification criteria we construct regional maps of the distribution of crustal domains on both sides of the north atlantic these maps reveal significant variations in rifting style on the conjugate margins and along strike of each margin and also highlight the role of ancient transfer zones in compartmentalizing these rifting variations into four distinct regions we propose that the limited localization of shallow topographically high serpentinized peridotite ridges on the newfoundland iberia and flemish cap galicia bank conjugate margins was directly related to an increase in the rate of extension following the separation of flemish cap and galicia bank which exhumed deeper less serpentinized mantle

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

switch of mesozoic extensional tectonic style in the lusitanian basin portugal insights from magnetic fabrics abstract magnetic fabrics in the lusitanian basin show extreme variability in the orientation of strain axes during part of its mesozoic extensional stage a detailed study of anisotropy of magnetic susceptibility ams was done in triassic and upper jurassic units in the onshore part of the basin in the triassic samples the magnetic lineation shows a dominant nw se orientation perpendicular to the main normal fault set and also to the extension directions inferred from the analysis of brittle mesostructures for the late jurassic period the ams analysis indicates a dominant n s to ne sw extension moreover these main directions are complicated by perpendicular solutions co existing in the same sites comparison with syn sedimentary faults reveals the difficulty in interpreting ams data in these settings although magnetic stability for the obtained solutions can be tracked through different mineralogical composition for the sampled rocks interpretation of the obtained fabrics through a triassic radial extension regime is consistent with axes switching and local re orientation of strain axes close to major normal faults related to the opening of the northern atlantic during the jurassic

petrographic characteristics of the wyodak anderson coal bed paleocene powder river basin wyoming u s a abstract six lithofacies of the thick 30 m wyodak anderson subbituminous coal bed of the fort union formation paleocene powder river basin wyoming can be delimited using megascopic and petrographic data previous lithofacies analysis of the rock types associated with the wyodak anderson bed suggested that raised peat accumulated in restricted parts of an inland flood plain the peat bodies were separated by deposits of contemporaneous possibly anastomosed channels in this study megascopic descriptions from four mine highwalls of the wyodak anderson coal bed were found to be similar to facies defined by microscopic data from core and highwall samples the data indicate that the upper and lower parts of the coal bed are rich in preserved wood remains for instance humotelinite whereas the middle part of the bed contains comparatively larger amounts of material that resulted from degradation and comminution of the peat e g eugelinite the facies are interpreted to be the result of different chemical and biological environments at the time of peat formation

consequences of flight height and line spacing on airborne helicopter gravity gradient resolution in the great sand dunes national park and preserve colorado line spacing and flight height are critical parameters in airborne gravity gradient surveys the optimal trade off between survey costs and desired resolution however is different for every situation this article investigates the additional benefit of reducing the flight height and line spacing though a study of a survey conducted over the great sand dunes national park and preserve which is the highest resolution public domain airborne gravity gradient data set available with overlapping high and lower resolution surveys by using fourier analysis and matched filtering it is shown that while the lower resolution survey delineates the target body reducing the flight height from 80 m to 40 m and the line spacing from 100 m to 50 m improves the recoverable resolution even at basement depths

the conundrum of coal bed thickness a theory for stacked mire sequences maximum thicknesses for modern peats have been documented only up to about 20 m whereas coal beds can often be as much as 90 m thick since peat is expected to compact appreciably during burial there appears to be no modern analogue for the processes which formed thick coal beds and this seems to challenge the law of uniformitarianism however the conundrum of coal bed thickness can be resolved by identification of discontinuities in coal beds coal beds are generally treated as single entities created by a continuous process of peat deposition it is more likely however that most thick coal beds are composed of multiple paleo peat bodies stacked one upon another rather than a single paleo peat body it is suggested that there are three types of bounding surfaces seen in modern peat bodies that can be used to distinguish individual paleo peats in coal beds these bounding surfaces can be recognized both in the field and microscopically each of these surfaces represents cessation or at least ext

iberian plate motions during the mesozoic abstract as more data are collected on the deep parts of the conjugate margins of canada and eurasia models of the early kinematics of iberia become better constrained in order to specify the motions during phases of continental rifting to the west and to the north of iberia we used recent data on the early oceanic spreading in the tagus abyssal plain and added simple assumptions on the geometry the tagus abyssal plain was formed after the end of continental rifting on the southwest portuguese margin in latest jurassic time before chron m 0 118 ma as a first step we close the space adjacent to the m 0 anomaly to keep open only the oldest oceanic part of the tagus plain which is assumed to be latest jurassic to earliest cretaceous in age in a second step we close this space the main results are as follows 1 1 the galicia bank slid along the southern flank of flemish cap this motion is interpreted as a strike slip motion or as a very oblique rifting 2 2 a late jurassic reconstruction of iberia and north america is obtained without considerable overlap and without large motion of microplates such as galicia bank this is possible because a large amount of continental extension occurred over a long time to the north of the grand banks and permitted early motion between north america and eurasia 3 3 a tight initial reconstruction can only be reached if strike slip motion is located between southern eurasia and northern eurasia along a shear zone following the english channel and the transform area between galicia bank and flemish cap

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

models of the development of the west iberia rifted continental margin at 40 30 n deduced from surface and deep tow magnetic anomalies the ocean continent transition oct on nonvolcanic rifted continental margins is important in that it contains evidence concerning the breakup of the continents and the onset of seafloor spreading the nature of the oct off western lberia has recently been attracting attention following seismic and other geophysical studies there and drilling of acoustic basement by leg 149 of the ocean drilling program here we concentrate on the interpretation of a new digital magnetic anomaly chart for the iberia abyssal plain between 39 5 o and 42 2 o n the most striking anomaly is a trough which exists immediately east of and locally parallel to anomaly j and is closely coincident with a basement peridotite ridge we conclude from modeling surface magnetic anomalies and a deep tow magnetometer profile that seafloor spreading began about 129 9 m y ago barremian at a rate of 10 0 mm yr consistent with drilling and seismostratigraphic results from the southern lberia abyssal plain a second feature is the existence of linear low amplitude isochron parallel magnetic anomalies east of the peridotite ridge trough and a clear change in the trend of these anomalies east of about 11 o 15 w it is possible to model these anomalies by a series of 7 to 30 km wide weakly magnetized crustal blocks of about the same thickness as the oceanic crust the west to east anticlockwise change in trend at 11 o 15 w suggests either a major change in stress regime and or in the type of magnetic anomaly source we speculate that the region between the peridotite ridge and 11 o 15 w represents a transitional crust whose formation was dominated by the same stress regime which accompanied eventual seafloor spreading we explain the change in trend at 11 o 15 w by a model featuring a rift which propagated through continental crust from south to north we consider three scenarios for the formation of the transitional zone crust first continental crust is surrounded and impregnated by intrusive and extrusive material formed from passive upwelling of magma created by the limited adiabatic decompression partial melting which occurs as the two continental lithospheric plates first begin to separate second such crust is surrounded by unroofed upper mantle material or third the zone is the product of ultraslow seafloor spreading present evidence tends to support the first scenario in this scenario the top of the asthenosphere eventually becomes shallow enough to enable magma to penetrate the thinnest continental crust fill the space caused by additional extension and form the transitional crust already described over a broad zone at least several tens of kilometers wide at breakup upper mantle rocks become exposed on the seafloor and undergo extensive serpentinization in a final stage we envisage focusing of the igneous activity leading to the onset of seafloor spreading initially producing thin oceanic crust because of a restricted melt supply the width of continuous tectonically extended continental crust in the southern iberia abyssal plain is less than was previously supposed

petrographic analysis of the rosebud seam at the absaloka big sky and rosebud mines powder river basin montana abstract analysis of maceral and mineral content and huminite reflectance for the rosebud coal at the absaloka big sky and rosebud mines provides information on the variation of coal composition and rank probably caused by variation in depositional environments and coalification humanite reflectance indicates that rank is gradational from lignite at the absaloka and rosebud mines to subbituminous c at the big sky mine amounts of minerals and huminite inertinite and liptinite group macerals vary vertically at absaloka and big sky defining lithologic layers and suggesting changes in type and style of peat accumulation direct correlation of huminite reflectance with huminite abundance and inverse correlation with inertinite abundance suggests a possible relationship with coalification depositional environment and or original floral characters depositional environment is initially interpreted as a swamp with mixed vegetation or a swamp alternating from arboreal to herbaceous vegetation

comparison of the petrography palynology and paleobotany of the little fire creek coal bed southwestern virginia u s a abstract two continuous cores that penetrated the lower pennsylvanian little fire creek coal bed in the southwestern coal field in southwestern virginia were sampled and x ray radiographed to determine subunit distinctions comparison of petrographic palynologic and paleobotanic data from the same sample sets from the two cores allowed for comparison of compositional data within the little fire creek coal bed the proximate petrographic palynologic and plant tissue data from two sets of samples indicate a high ash gelocollinite and liptinite rich coal consisting of a relatively diverse paleoflora including lycopsid trees small lycopsids tree ferns small ferns pteridosperms seed ferns and rare calamites and cordaites the relatively very high ash yields 3 80 wt the relatively thin subunits 1 28 cm and the large scale vertical variations in palynomorph floras suggest that the study area was at the edge of the paleopea forming environment as a result most of the compositional correspondences are among those components indicative of degradation or decomposition

petrology of fibrous coal fusain and associated inertinites from the early paleocene of the central alberta plains abstract megascopic micropetrographic and scanning electron microscopic investigations of fibrous coal indicate that paleo wildfires were common occurrences in the mire which produced highvale coals at least 20 fibrous coal fusain horizons have been identified in corehole samples from the pit no 3 locality at highvale in the central alberta plains thicknesses of individual horizons vary and are not particular to any stratigraphic position within coal seams the majority of these fibrous horizons is within the two thick economic seams the highvale nos 1 and 2 which are characteristically megascopically dull the dullness of given lithotypes is largely related to inertinite content with fibrous coal containing 51 inertinite on average and selected horizons comprised of as much as 85 inertinite semifusinite and inertodetrinite are the predominant inertinites with a few horizons exhibiting highly reflecting fusinite macrinite is rare and micrinite is absent sem investigations reveal that certain fibrous coals exhibit excellent preservation of the original gymnospermous taxodium woody tissue features such as homogenization and swelling of the cell walls elimination of the middle lamellae and preservation of bordered pits are clearly indicative of charcoal formation as a product of paleo wildfires depending upon the nature of the fire temperatures obtained and the nature of the mire vegetation a wide range of inertinite precursors can be produced

the giant chaotic body in the atlantic ocean off gibraltar new results from a deep seismic reflection survey abstract the central eastern atlantic continental slope and parts of the horseshoe and seine plains west of the gibraltar arc are occupied by a seismically chaotic body this paper reports new deep seismic reflection data that allows a first assessment of the three dimensional geometry of the body and discussion of its evolution the seismically chaotic body is huge in area and volume and complex in origin comprising mainly gravity deposits debris flows olistostromes in the northern sector and tectonic melanges in the southern where the body forms part of a south verging accretionary prism related to africa iberia convergence submarine extension of the rifian system of n africa the northern part up to several tens of thousands of cubic kilometers in volume results from the superposition of a few endoolistostromes probably of miocene age centripetally discharged onto the eastern horseshoe plain and adjacent slope from structural highs generated during the late miocene paroxismal phase of iberia africa convergence submarine flows were triggered along regional continuous slopes up to 100 km in length their volume largely exceeds previously reported marine occurrences of gravity flow deposits the outstanding examples of which occur in intraplate settings hot spots old passive margins at the boundaries lateral or frontal ramps of the southern tectonic melange complex smallscale olistostromes of pliocene age also occur recalling the so called precursory olistostromes of collisional chains the gravity and tectonic structures occur in a convergent plate setting with low shortening rates and their eventual fate will be incorporation with disruption in a collisional chain their volume and extent appear comparable to those that can be calculated for huge chaotic units in orogens such as the argille scagliose liguride complex of the apennines in which disrupted olistostromes and tectonic melanges coexist

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