sedimentology and isotope geochemistry of carnian deep water marl limestone deposits from the sicani mountains sicily environmental implications and evidence for a planktonic source of lime mud abstract the upper triassic halobia bearing marl limestone deposits from the sicani mountains sicily record the sedimentary evolution of the sicanian basin through the middle and late carnian time dark marls and interbedded grey calcilutites of julian age are characterized by abundant pyrite sparse bioturbation and negative carbonate carbon 13c values they accumulated in a basin with dominantly anoxic to dysaerobic bottom waters lower tuvalian dark grey pyritic marls and calcilutites which contain carbonate minerals with relatively high mn contents and widely fluctuating 13c signatures were deposited under dysaerobic conditions middle and upper tuvalian cherty limestones show intense bioturbation and nearly invariable positive 13c values around 2 for calcite they form a thick and monotonous succession accumulated in a deeper and more oxygenated basin the halobia bearing deposits preserve some calcareous nannoplanktonic forms the nannofossils varying in size from 7 to 32 m are significantly abundant in the cherty limestones pointing to a notable role of the calcareous nannoplankton as a source of carbonate mud in the deep water basins of the southern tethys during the late triassic time

mapping of marine benthic habitats using image processing techniques within a raster based geographic information system the present paper describes a method where maps of marine benthic communities in the littoral and sublittoral zones are produced using image processing techniques within a raster based geographic information system gis maps of the littoral zones were based on digital raster images derived from aerial photographs for the sublittoral zone a raster image was generated from acoustic data recorded by a roxann system the image processing technique of unsupervised classification divided the images into areas which possess similar physical environmental characteristics images were validated with biological information collected from dedicated visual littoral and video sublittoral surveys ground validation data were overlain onto the image to enable a supervised classification each area was assigned to a biotope thus creating biotope maps for the littoral and sublittoral zones using image processing for the analysis of roxann data is a new approach to benthic mapping because it treats acoustic data as continuous variables rather than categorical data as used by traditional methods the methods described here allow remotely sensed data from tile sublittoral and littoral environments to be processed using similar analyses however prior to producing a composite map of both these environments problems of scale and spatial resolution need to be resolved these issues are discussed

a rise in the carbonate compensation depth of western tethys in the carnian late triassic deep water evidence for the carnian pluvial event the upper triassic of the lagonegro basin southern apennines southern italy is represented by hemipelagic cherty limestones of the calcari con selce formation deposited in an oceanic setting two stratigraphic sections petina chiana and pignola 2 representative of the evolution of the lagonegro basin during the carnian have been studied in detail with a multidisciplinary approach in the pignola 2 section within the calcari con selce formation a unique interval composed of green shales and radiolarites has been identified the absence of carbonate deposition within this interval is interpreted as evidence of a contemporaneous shallowing of the carbonate compensation depth conodont and palynomorph biostratigraphy constrain the age of this interval to the julian tuvalian lower carnian upper carnian boundary the age and characteristics of this interval suggest correlation with a putative climatic event known as the carnian pluvial event which has also been recognized in continental and shallow marine successions from different european localities this event is thus now documented also in a deep marine setting like the continental and shallow water settings it is characterized by a sudden input of siliciclastics petina chiana and pignola 2 integrate current knowledge of the carnian distribution of conodonts paragondolella praelindae kozur to date known only from the lower tuvalian has now been documented from the uppermost julian moreover a drastic turnover was recorded between julian and tuvalian conodont assemblages which is clearly associated with the carnian pluvial event thus a biotic crisis oceanographic changes associated with the rise of the carbonate compensation depth increased rainfall and an anomalous siliciclastic input occur contemporaneously at the time of the carnian pluvial event a similar pattern is associated with perturbations of the carbon cycle that occur during the jurassic and cretaceous e g in the early aptian thus it is hypothesized that the carnian pluvial event may have analogous causes

utility of coal petrology for sequence stratigraphic analysis abstract sequence stratigraphy seeks to predict the depositional architecture of sediments based on the principle that their superposition and lateral arrangement are largely determined by the rate at which accommodation is made below depositional base level relative to the supply rate of sediments depositional base level is generally correlated with sea level which in paralic peat coal deposits controls the position of the groundwater table above which oxidation ablation and erosion would occur the current late quaternary sequence is used to discuss some of the constraints on coal formation that stem from the interaction of short and long period modulations on sequence forming eustatic cycles the results show that the mid transgressive systems tract is unlikely to produce significant coal deposits which is supported by a survey of the relevant literature from eight different countries it reveals a bimodal distribution of coal deposits with the strongest mode being situated in the early transgressive systems tract while a broader secondary mode occurs in the early and mid highstand position this concentration contrasts with the complete absence of any significant coal deposits in the early and mid lowstand systems tract and only a low occupancy of the late highstand systems tracts the reasons for this distribution are briefly discussed and attention is drawn to the possible over stating of the coal forming potential of the late lowstand systems tract following a brief discussion of the sequence stratigraphic interpretation of coal measures emphasis is put on the application of sequence stratigraphy to the study of coal seams and their composition at various levels of petrographic detail while in low rank coals botanical affinities contribute much to the lithotype based analysis a genetic assessment of bituminous coal seams relies primarily on physical and chemical palaeo environmental signatures simple properties such as maximum coal thickness low detrital mineral content and maximum preservation of vitrinite particularly of telovitrinite define a good balance between the former rates of accommodation versus peat accumulation iso metamorphic variations in telovitrinite reflectance and its dispersion measured by the coefficient of variation have also contributed to the palaeo environmental interpretation this paper confirms the identification within coal seams of most of the sequence stratigraphically significant surfaces e g sequence and parasequence boundaries transgressive flooding and maximum flooding surfaces it also gives examples of some new ones referred to as accommodation reversal non marine flooding give up transgressive terrestrialisation and paludification surfaces some of these are specific to coal measures but the give up transgressive and accommodation reversal surfaces may have wider significance

clay mineral assemblages of mesozoic pelagic and flysch sediments of the lombardian basin southern alps implications for palaeotectonics palaeoclimate and diagenesis clay mineral assemblages determined by x ray diffraction in the jurassic to lower cretaceous hemipelagic pelagic sediments and in the upper cretaceous flysch sequences of the lombardian basin southern alps record tectonic and possibly climatic changes in the source areas and to a lesser extent alterations during burial diagenesis

hot spot activity and the break up of pangea abstract the mesozoic and cenozoic positions of the continents that formed pangea in the triassic jurassic were derived from paleomagnetic and intraplate volcanic data paleoclimatic observations such as reef and fossil flora distribution and geological observations major hot spots helped to determine the longitudinal position of pangea and to construct a model of plate motion during the pangean break up the position of the northern part of pangea was constrained using iceland and jan mayen hot spots the iceland hot spot was traced from its present day position to greenland in the paleocene to baffin bay in the late cretaceous to the alpha ridge in the early cretaceous to the chukchi borderland in the middle late jurassic to franz joseph land in the early jurassic the yenisei khatanga trough in the middle triassic and finally to west siberia in the late permian early triassic the hot spot activity is expressed by eastern and western greenland volcanics the siberian trap basalts and perhaps by alpha ridge and chukchi borderland volcanics the chukchi borderland volcanics are related to the early stage of the opening of the canadian basin the position of the southern part of pangea was constrained using the bouvet hot spot this hot spot was tracked from its present day position to western antarctica in the early cretaceous late jurassic and to south africa in the early jurassic late triassic this hot spot activity produced the ferrar and karoo volcanics the model of plate motion obtained agrees with other data on intraplate volcanics which are also related to hot spots at the time of the opening of the central atlantic the cape verde and canary island hot spots were located along the ocean s spreading axis the long lasting location of hot spot and associated mantle upwelling plumes could help to explain forces driving the tethys transit plates opening of the ligurian ocean and eastern mediterranean the european hot spots are related to the several mesozoic phases of rifting for example the rhine graben hot spot may have been located at the rifting axis in the north sea several authors have already discussed the contribution of hot spots to the opening of the south atlantic and indian oceans mantle plumes associated with hot spots play an active role in rifting and initial phases of spreading the lithospheric displacement caused by upwelling combined with sometimes remote collisional forces on the other side of continental plate may result in compression and basin inversion

truncated higher order sequences as responses to compressive intraplate tectonic events superimposed on eustatic sea level rise abstract high resolution sequence stratigraphic analysis of the lignite bearing miocene siliciclastic sequence of the salotarjan lignite formation slf has been performed by lithostratigraphic dissection of more than 1350 boreholes and by detailed analysis of well logs from more than 150 boreholes biostratigraphic data indicate that the slf represents a single 3rd order eustatic sequence namely the bur 4 of vakarcs et al vakarcs g hardenbol j abreu v s vail p r varnai p tari g 1998 oligocene middle miocene depositional sequences of the central paratethys and their correlation with regional stages sepm special publication vol 60 209 231 as for facies conditions facies models for sandy shorefaces and or wave dominated deltas can be applied twenty six parasequences have been identified and mapped in the adjacent sub basins from well log correlations the sharp based sand bodies of ps 10 and 17 were interpreted as the falling stage systems tract fsst of higher order sequences the subsequent transgressive systems tracts tst are represented by retrograding sets of 2 3 parasequences ps 11 13 18 19 based on the regional unconformity at the base and the regionally extended sharp based sand bodies three sequence boundaries sb were determined that dissect the 3rd order sequence into three higher order sequences one of the special features of the sequence is that the fssts interrupt the rapid relative sea level rises ps 9 and 16 and lie directly on the silty material of nearshore environments leading to the lack of the higher order highstand system tracts hst truncated transgressive semi cycles another characteristic is the striking basinward fore stepping of the sedimentary depocentres and that of the facies belts of the lignite seams the rapid relative sea level falls implied by the two fssts are unexpected in the context of an overall eustatic rise thus the possibility of tectonic origin of shallowing was investigated this verification was based primarily on the observations that 1 the basin was united when parasequences 1 to 13 were developed whereas 2 by the end of the sequence development the palaeozoic basement protruded to the surface dividing the basin reflecting intense tectonic events simultaneous with sequence development the fssts with the sbs above and the formation of higher order sequences can thus be regarded as sedimentary responses to syn sedimentary tectonic elevation and tilting of the basement this elevation was induced by tectonic compression and associated imbrication along a regional reverse fault that was known as the darno line the imbrication could have controlled not only the repeated relative sea level falls but also the striking fore stepping of the sedimentary depocentres and facies belts of the associated lignite seams tectonic tilting influenced not only the fssts but the subsequent early tsts as well thus lignite seams associated with the tectonically counteracted tsts are characterized by multiple seams with several accessory seams va iiia b and ia while those associated with tectonically quiescent periods are aerially extensive and solitary comparison with other coal bearing formations enhanced the importance of the fsst in the interpretation of stratigraphic truncations coal seam geometry conditions facies shiftings and stratal geometry enabling a more accurate description of syn sedimentary tectonic events

depositional controls on coal distribution and quality in the eocene brunner coal measures buller coalfield south island new zealand abstract the buller coalfield on the west coast of the south island new zealand contains the eocene brunner coal measures the coal measures unconformably overlie paleozoic cretaceous basement rocks and are conformably overlain by and laterally interfinger with the eocene marine kaiata formation this study examines the lithofacies frameworks of the coal measures in order to interpret their depositional environments the lower part of the coal measures is dominated by conglomeratic lithofacies that rest on a basal erosional surface and thicken in paleovalleys incised into an undulating peneplain surface these lithofacies are overlain by sandstone mudstone and organic rich lithofacies of the upper part of the coal measures the main coal seam of the organic rich lithofacies is thick 10 20 m extensive locally split and locally absent this seam and associated coal seams in the buller coalfield are of low to high volatile bituminous rank vitrinite reflectance between 0 65 and 1 75 the main seam contains a variable percentage of ash and sulphur these values are related to the thickening and areal distribution of the seam which in turn were controlled by the nature of clastic deposition and peat forming mire systems marine transgression and local tidal incursion the conglomeratic lithofacies represent deposits of trunk and tributary braided streams that rapidly aggraded incised paleovalleys during sea level stillstands the main seam represents a deposit of raised mires that initially developed as topogenous mires on abandoned margins of inactive braidbelts peat accumulated in mires as a response to a rise in the water table probably initially due to gradual sea level rise and climate and the resulting raised topography served as protection from floods the upper part of the coal measures consists of sandstone lithofacies of fluvial origin and bioturbated sandstone mudstone and organic rich lithofacies which represent deposits of paralic deltaic barrier shoreface tidal and mire and marine environments the fluvial sandstone lithofacies accumulated in channels during a sea level stillstand the channels were infilled by coeval braided and meandering streams prior to transgression continued transgression ranging from tidal channel estuarine incursions to widespread but uneven paleoshoreline encroachment accompanied by moderate basin subsidence is marked by a stacked back stepping geometry of bioturbated sandstone and marine mudstone lithofacies final retrogradation sea level highstand is marked by backfilling of estuaries and by rapid landward deposition of the marine kaiata formation in the late eocene

palaeoclimate reconstructions of the middle jurassic of kachchh western india an integrated approach based on palaeoecological oxygen isotopic and clay mineralogical data abstract the middle jurassic sedimentary succession of the kachchh basin shows significant changes in lithology faunal content and diversity across the bathonian callovian boundary the change in lithology from predominantly carbonates in the middle and late bathonian to siliciclastics in the callovian is accompanied by a drop in species diversity from high to moderate characteristic faunal elements of the bathonian corals sponges the bivalves eligmus and members of the opinae are absent or rare in the callovian in contrast callovian sediments contain comparatively high proportions of nuculid bivalves the clay mineral assemblage reveals prominent variations in the smectite vs kaolinite abundance especially during the bathonian to callovian transition from the bajocian to the middle bathonian smectite becomes the dominant clay mineral and is nearly exclusively present in the late bathonian towards the middle callovian its content gradually decreases and kaolinite becomes the dominant clay mineral illite generally is only a minor component throughout the middle jurassic based on these results the bajocian to middle bathonian time interval is interpreted to represent subtropical climatic conditions with seasonal droughts and a moderate supply of terrigenous clastics to the basin the late bathonian was a period with a semi arid climate hot seasonal droughts and a minor input of terrigenous clastics the increase in kaolinite contents in the callovian suggests a subtropical humid climate with less prominent seasonal droughts and a higher input of siliclastics into the basin accompanied by a higher nutrient influx oxygen isotope ratios measured on bathonian to early callovian brachiopod shells give palaeotemperatures of 19 24 c callovian to oxfordian paleotemperatures calculated from oxygen isotopes measured on belemnite rostra range from 11 to 21 c the lower palaeotemperatures estimated from the oxygen isotopic composition of belemnite calcite are explained by assuming that the belemnites spent most of their life span in colder regions of the malagassy gulf and migrated into the warmer subtropical waters of the kachchh basin combining these various lines of evidence the changes in lithology and faunal composition taking place in the kachchh basin during the middle jurassic appear to reflect largely a change towards increasing humidity rather than a distinct decrease in water temperature

interaction between faulting and sedimentation during dinantian extension of the solway basin sw scotland the ene wsw trending north solway fault acted as a northern marginal fault to the solway basin during dinantian sedimentation structural sedimentological and diagenetic relationships suggest syn sedimentary dinantian movement was dip slip and normal a later carboniferous phase of dextral transtension is also indicated allokinetic deformation features increase in abundance and intensity towards the north solway fault their presence and nature being strongly facies dependent syn sedimentary fault deformation of the hanging wall sediments also increases towards this fault both distributed and localized shearing characterizes these early faults and is thought to be related to the water content of beds at the time of deformation local minor thrusting and reverse fault movement also occurred within the sediments during basin extension due to dextral transtensional movement on the north solway fault n s and nw se trending faults appear to show no evidence for syn sedimentary dinantian movement and are interpreted as the products of 9hercynian9 basin shortening and mesozoic basin formation

palaeoenvironmental controls on the clay mineralogy of carnian sections from the transdanubian range hungary abstract the upper triassic sediments both in nw europe and in the mediterranean region imply a generally arid climate regime in the carnian however a humid phase with a high input of siliciclastics is assumed carnian pluvial event but its causes are still highly controversial the carnian marine succession of the transdanubian range tr hungary also shows a significant change in sedimentation pelagic carbonate deposition fured limestone formation was followed by the formation of marly sediments veszprem marl and sandorhegy formations in order to understand the environmental changes the clay mineralogy of 240 carnian samples determined by x ray diffraction is discussed in the present paper additionally this set of clay mineral data from four boreholes from the bakony hills bakonysz cs bszu 1 balaton highland balatonfured bfu 1 mencshely met 1 and zsambek basin zsambek zs 14 allows us to test the reliability of clay minerals as palaeoclimatic proxies for the carnian late triassic by reconstructing spatial and temporal variations the first increase in clay content of the studied carnian succession can be detected in the limestone marl couplets of the cordevolian fured limestone its clay fraction is dominated by illite mixed layer illite smectite is and chlorite without kaolinite a good indicator of landmasses with a hot climate and constant humidity thus this compositional change probably related to a sea level drop subsequently the clay mineral assemblages of the veszprem marl sections in the bakony hills and the balaton highland are composed of illite poorly ordered r 0 is with 60 70 expandable component chlorite and kaolinite on the other hand the clay fraction of the samples from the zsambek basin is composed of illite is with an average of 40 50 expandable component and a transitional r 0 to r 1 type of ordering and kaolinite chlorite does not occur in the early julian kaolinite enrichments 10 20 in the clay fraction can be regarded as a manifestation of the climate shift from the prevailing aridity to the more seasonal climate with enhanced humid season the overall presence of abundant illite and accompanying chlorite can indicate a high rate of erosion of moderately weathered rocks while the large amount of smectitic clay transformed to is could be partly derived from transport of weathering products from a distant source area and subordinately from diagenetic alteration of intermediate to basic volcanic rocks spatial variation in the expandability and ordering of the is at least partially could be caused by different degree of the diagenetic overprint

the mid cenozoic challenger rift system of western new zealand and its implications for the age of alpine fault inception analysis of the structure and sedimentary geology of western new zealand has identified a middle eocene to early miocene continental rift system 1 200 km long and 100 200 km wide named here the challenger rift system four phases of rift development occurred 1 infra rift subsidence 2 active axial trough subsidence 3 expanded rift subsidence involving collapse of the rift shoulders and 4 incipient sea floor spreading the spatial and temporal distribution of these phases identifies a north island and a south island rift segment and shows that rifting propagated toward the center of the rift from both ends the northern segment shows a simple pattern of rifting that is comparable with vink9s model of rift propagation the southern segment with locked zones and rift nucleation segments is comparable to courtillot9s model of rift propagation the sea floor spreading history of the southwest pacific shows that the northern rift segment probably linked with a sea floor spreading center in the norfolk basin and the southern segment linked with the southeast indian ridge this is corroborated by the good correlation between the ages of sea floor magnetic anomaly lineations that are aligned with the rift and the biostratigraphic ages of rifting the probable continuity of the rift system in its early development precludes pre miocene transcurrent displacement on the alpine fault an early miocene 23 m y b p age of alpine fault inception is indicated by the age and pattern of rift disruption attributed to compression that originated at the australia pacific plate boundary the modern australia and pacific plates were not discrete entities therefore until the early miocene

sedimentary structures associated with extensional fault movement from the westphalian of ne england at an opencast coal mine in southern co durham close to the major butterknowle fault an exposed upper westphalian a sequence displays a plethora of tectonically associated structures fractures across the area of the opencast site were found to contain high concentrations of minerals which were apparently introduced at the time of formation of the n pennine orefield carboniferous permian from authors

climate of the supercontinent pangea numerous climate models predict that the geography of the supercontinent pangea was conducive to the establishment of a megamonsoonal circulation in general geologic evidence supports the hypothesis of a megamonsoon that reached maximum strength in the triassic pangea in the late carboniferous had widespread peat formation in what is now central and eastern north america and europe and relatively dry conditions on the colorado plateau the equatorial region of the continent became drier through the end of the carboniferous by the permian the equatorial region of pangea was dry and indicators of aridity and rainfall seasonality became more widespread wind directions from colorado plateau eolian sandstones are consistent with an increasing influence of monsoonal circulation at this time in the triassic climate in the colorado plateau region became relatively wet though still seasonal and the few eolian sandstones indicate a major shift in wind direction at that time in addition sedimentation

the origin and tectonic significance of asymmetrical meander belts in the hebgen lake area of sw montana the madison and south fork rivers occupy the northeast sides of their respective meander belts the form of the abandoned meander loops within these asymmetric meander belts indicates that they were produced by gradual northeast migration of the active channels this progressive migration can be related to tectonic tilting produced by regional extensional faulting at a high angle to the original channel belt axis which ran down a gently sloping outwash cone asymmetric channel sandstone bodies in the rock record can be recognized by the preferred dip of successive lateral accretion units in meander loops together with soft sediment deformation facies and thickness variations they may indicate tectonic deformation of the sedimentary surface

sequence stratigraphic distribution of coaly rocks fundamental controls and paralic examples significant volumes of terrigenous organic matter can be preserved to form coals only when and where the overall increase in accommodation approximately equals the production rate of peat accommodation is a function of subsidence and base level for mires base level is very specifically the groundwater table in paralic settings the groundwater table is strongly controlled by sea level and the precipitation evaporation ratio peat accumulates over a range of rates but always with a definite maximum rate set by original organic productivity and space available below depositional base level groundwater table below a threshold accommodation rate nonzero no continuous peats accumulate due to falling or low groundwater table sedimentary bypass and extensive erosion by fluvial channels this is typical of upper highstand lowstand fan and basal lowstand wedge systems tracts higher accommodation rates provide relatively stable conditions with rising groundwater tables mires initiate and copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received september 7 1995 revised manuscript received november 25 1996 final acceptance may 5 1997 2exxon production research company 3120 buffalo speedway houston texas 77096 3exxon production research company 3120 buffalo speedway houston texas 77096 present address conoco inc p o box 2197 houston texas 77252 we benefited from the input and assistance of many people of special assistance were the teams involved in collaborative studies with esso australia and esso malaysia p moore m sloan j emmett b burns a partridge s creaney hanif hussein r hill r lovell and m feeley we also thank the rock springs team r beauboeuf p mclaughlin w devlin a carroll y y chen g grabowski jr k miskell gerhardt m farley r webster and j schwalbach group members d curry and j yeakel were always helpful we also enjoyed and profited from many discussions of these concepts with our colleagues outside exxon c diessel r boyd k shanley b zaitlin p mccabe m hendricks a cohen and m kirschbaum we thank the reviewers of company reports whose careful comments on several generations of this work improved it s creaney m feeley j van wagoner f wehr j yeakel and a young f weber and j zullig provided extensive management support k linke translated our sketches into the fine figures herein we value all the help

late cretaceous to early paleocene climate and sea level fluctuations the tunisian record abstract climate and sea level fluctuations across the cretaceous tertiary k t transition in tunisia were examined based on bulk rock and clay mineralogies biostratigraphy and lithology in five sections el melah el kef elles ain settara and seldja spanning from open marine to shallow inner neritic environments late campanian to early danian trends examined at el kef and elles indicate an increasingly more humid climate associated with sea level fluctuations and increased detrital influx that culminates at the k t transition this long term trend in increasing humidity and runoff in the tethys region is associated with middle and high latitude cooling results of short term changes across the k t transition indicate a sea level lowstand in the latest maastrichtian about 25 100 ka below the k t boundary with the regression marked by increased detrital influx at el kef and elles and a short hiatus at ain settara a rising sea level at the end of the maastrichtian is expressed at elles and el kef by deposition of a foraminiferal packstone a flooding surface and condensed sedimentation mark the k t boundary clay which is rich in terrestrial organic matter the p0 p1a transition is marked by a sea level lowstand corresponding to a short hiatus at ain settara where most of p0 is missing and a period of non deposition and erosion in the lower part of p1a 64 95 ma at seldja p0 and possibly the topmost part of cf1 are missing these sea level fluctuations are associated with maximum humidity these data suggest that in tunisia long term environmental stresses during the last 500 ka before the k t boundary and continuing into the early danian are primarily related to climate and sea level fluctuations within this long term climatic trend the pronounced warm and humid event within the latest maastrichtian zone cf1 may be linked to greenhouse conditions induced by deccan volcanism the absence of any significant clay mineral variations at or near the k t boundary and ir anomaly suggests that the bolide impact had a relatively incidental short term effect on climate in the tethys region

the middle carnian wet intermezzo of the stuttgart formation schilfsandstein germanic basin abstract the middle carnian wet intermezzo mcwi of the stuttgart formation schilfsandstein and age equivalent strata of the northwestern tethys occurred entirely within equivalents of the upper subzone of the austrotrachyceras austriacum ammonoid zone of the late julian its duration is estimated to be only about 0 7 0 8 myr in both the germanic basin and the northwestern tethys the warm climate during the mcwi was characterized by a rate of precipitation that exceeded somewhat the evaporation but was not so great as to be pluvial the mcwi was related to the atmospheric circulation of a megamonsoonal system that was characterized by strong moisture laden northwesterly flowing trade winds that rose as they reached the estimated 2000 3000 m high eastern shoulder uplift of a huge rift causing them to drop an extraordinary amount of rain this eastern shoulder uplift lay within the caledonides of modern day western scandinavia this region only between 30 and 50 n palaeolatitude had a truly pluvial climate and the huge amounts of fresh water dropped there transported large amounts of siliciclastics from this rift shoulder uplift southward into the germanic basin before deposition of the siliciclastics an early julian eustatic sea level fall caused widespread erosion in the germanic basin in the later part of late julian a transgression from the eastern gates with the concurrent strong fresh water influx from the north flooded the centre of the northern germanic basin with a shallow brackish sea in which the osterhagen horizon basisschichten of the lower stuttgart formation was deposited in the upper osterhagen horizon the salinity rapidly decreased from mesohaline through mio and oligohaline to fresh water levels in southern germany the basisschichten formed entirely within fresh water or very low salinity brackish environments later a slight subsidence of the southwestern germanic basin shifted the main outflow of fresh water toward the southwestern end of the basin creating local brackish conditions in the northern marginal part of the northwestern tethys e g in the lunz beds during this time interval tidal influence also can be found in the stuttgart formation deposited in palaeoestuaries of the southwestern germanic basin adjacent to the tethys the very strong fresh water influx from the north however prevented these estuaries from developing a strongly elevated salt content so that only fresh water to oligohaline brackish faunas are found there such as the eberstadt bivalve conchostracan fauna at the base of the tuvalian the megamonsoonal system either disintegrated or else the trade winds shifted their principal flow direction this caused the climate within the germanic basin and in the nearby northwestern tethys sea to become arid again as it had been before the deposition of the stuttgart formation these changes in the atmospheric circulation patterns also terminated the pluvial climatic regime to the north along the scandinavian eastern rift shoulder uplift this in turn ended the transport of huge amounts of siliciclastics from this region southward into the germanic basin and ended the deposition of the schilfsandstein after this the hypersaline sabkha and playa sedimentation of the weser formation began which was accompanied by some minor marine ingressions in the southwestern germanic basin

palynological correlation of carnian humid pulses throughout western tethys abstract the carnian pluvial event is an upper triassic swing toward increased rainfall best documented in the tethys tropical belt and mainly recognized on its effects on sedimentary systems as the demise of carbonate platforms and the enhanced siliciclastic supply in some portions of western tethys and particularly in the raibler schichten of the northern calcareous alps and in the dolomites the carnian pluvial event is recorded by four discrete siliciclastic pulses in the raibler schichten three siliciclastic intervals are documented and take the name of first second and third shale in order to correlate these pulses at the basinal scale the study of the palynological assemblages in a section of the raibler schichten near rubland austria and of the classical succession of the lunz nappe have been carried out more than eighty palynomorph species are recorded most of them correspond to typical carnian morphospecies of the carnian pluvial event in europe on the base of their stratigraphic distribution three different palynomorph assemblages are described aulisporites astigmosus assemblage lagenella martinii assemblage and granuloperculatipollis rudis assemblage a fourth older assemblage is also informally defined a palynostratigraphic correlation between the nca the germanic basin and the dolomites has been obtained the four siliciclastic pulses recognized in the raibler schichten and lunz are also found in the dolomites and yield the same palynological associations the base of the schilfsandstein that record the carnian pluvial event in the germanic basin is correlated to the second or third siliciclastic pulse first or second shale of the raibler schichten siliciclastic pulses are thus correlated throughout western tethys and can thus be interpreted as short lived humid climate wiggles within the carnian pluvial event a quantitative analysis of the carnian successions of the nca highlights a shift toward hygrophytic elements in the uppermost julian and an abrupt return to xerophytic associations in the lower tuvalian the palynological hygrophytic associations that characterize the aulisporites astigmosus and lagenella martinii assemblages are present in many other parts of europe and middle east suggesting that the carnian pluvial event determined a humid climate perturbation in a wide area of the northern hemisphere spanning from tropical to high latitudes

climato environmental controls on clay mineralogy of the hettangian bajocian successions of the mecsek mountains hungary an evidence for extreme continental weathering during the early toarcian oceanic anoxic event abstract clay mineralogy has been successfully used in palaeoclimatic interpretation of jurassic rocks in the mecsek zone hungary the clay mineral assemblages of the hettangian sinemurian fluvial and shallow marine coal bearing siliciclastic rocks gresten facies mecsek coal and vasas marl formations comprise predominantly illite smectite i s mixed layer minerals illite ill and kaolinite kao with the presence of berthierine and or chlorite these clay mineral suites suggest a humid subtropical climate with short term climate changes of high and low rainfall and a high supply of terrigenous clastics to the basin in the pliensbachian part of the sequence studied which is composed of predominantly hemipelagic mudstones allgau facies with intercalations of redeposited sandstone and limestone bodies the hosszuheteny calcareous marl mecseknadasd sandstone and kecskehat limestone formations are predominantly made up of illite and very little kaolinite and i s mixed layer minerals kao ill 1 suggesting a humid climate and intense continental weathering possibly related to the oceanic anoxic event in contrast rocks of the bajocian komlo calcareous marl formation contain high proportions of i s mixed layer mineral and illite with sparse occurrence of kaolinite kao ill 0 or kao ill

variations in organic geochemistry and lithology of a carbonate sequence deposited in a backplatform basin triassic hungary abstract the variations in the organic matter quantity and quality were studied with respect to the mineral composition of the carbonate sequences accumulated on a gentle slope zl 1 well and at the toe of the slope rzt 1 well located between a late triassic carbonate platform and a backplatform basin parallel variations observed in mineral composition and organic geochemical features of the successions appeared to be controlled by the change in climate and by sea level fluctuations the repetitive sea level changes resulted in a variation in the carbonate rich basin facies and in the mineralogically heterogenous slope and toe of slope ones according to rock eval pyrolysis organic petrography and carbon isotope ratios the immature organic matter is of predominantly marine origin and composed of mainly liptinites in both of the studied boreholes the results of the gc and gc ms analyses of the saturated hydrocarbon fractions of bitumens together with the composition of kerogen pyrolysates reveal a predominant algal input with a minor variable bacterial and subordinate terrestrial contribution for the rzt 1 borehole in the zl 1 borehole a significantly higher proportion of the bacterial biomass contributed to the organic precursors the 13 c values and the composition of the kerogen pyrolysates together with the results of the maceral analysis and gc data suggest a relatively higher but moderate higher plant derived contribution in the slope facies and at the top of the toe of slope facies the elementary composition of kerogens and rock eval data display type ii s kerogen in the basin and the slope facies and type i ii s one in the toe of slope facies variations in the hydrogen content of the organic matter mainly reflect variations in the preservation conditions and in primary productivity the presence of the 2 6 10 15 19 pentamethyleicosane and the extremely low pristane phytane ratios indicate a relatively high methanogenic bacterial activity and strongly anoxic depositional conditions in the rzt 1 well especially in two most organic rich toe of slope facies

sediment deformation structures and the palaeotectonic analysis of sedimentary basins with a case study from the carboniferous of northern england

rainfall patterns and the distribution of coals and evaporites in the mesozoic and cenozoic abstract paleoclimatologists have adequately demonstrated over the last twenty years that the distribution of climatically sensitive sediments can be related to present day climatic zones that are roughly parallel to latitude for example coals were deposited at paleolatitudes that correspond to the present day rainy zones at the equator and at about 55 n and 55 s indicating that those zones were present in the past from this it can be concluded that atmospheric circulation has not been radically different from its present configuration despite some apparently great differences in some climatic parameters such as the equator to pole temperature gradient nevertheless the zonal model for predicting the distribution of climatically sensitive sediments is not wholly adequate although general atmospheric circulation may not have been radically altered from its present pattern it would have differed in some respects because the paleogeography was different from the present geography therefore we have constructed what we believe are more realistic maps of the distribution of rainfall through time these maps are based on maps of atmospheric circulation that have been successfully used to predict the distribution of some petroleum source beds and phosphorites we have compared the predicted distribution of rainfall to the distribution of coals and evaporites for each of seven geologic stages the circulation rainfall maps were more successful than the zonal model for predicting the distribution of evaporites and coals for times when the paleogeography would have maximized the development of a monsoonal circulation which most effectively disrupts the general zonal pattern for times when a monsoonal circulation would not have been important the zonal model adequately predicted the distribution of these rocks

termination of carbonate slope progradation an example from the carnian of the dolomites northern italy abstract the demise of carbonate platforms during carnian time is a widespread phenomenon of the western tethys but the controlling factors are not well understood the dolomites of the southern alps northern italy are well known for their large scale ladinian and carnian prograding carbonate platforms platform growth stopped during the early carnian and both platforms and basinal areas were subsequently covered by mixed carbonate siliciclastic sediments raibl group we present a carbonate platform whose slope progradation came to a halt prior to draping by the siliciclastic sediments judging from the height of the clinoforms a platform to basin relief of at least 100 m existed during the final stage of progradation this paleo slope was colonized by coral patches draped by skeletal packstones to microbial bindstones forming typically lens shaped mounds on the steep slope the formation of mounds on the platform flank was only possible because the downslope transport of detritus from the platform and or upper slope was stopped the sedimentary evolution in the adjacent basin indicates a poorly oxygenated environment with abundant brackish water ostracods of low diversity based on the inherited platform to basin relief and the lithofacies of the basin fill a local sea level drop in the order of 60 80 m is postulated with rising sea level the accommodation space between former basin and platform became filled by shallow marine mixed carbonate siliciclastic sediments the abundance of epibenthic suspension feeders of the basin fill such as megalodonts suggests increased nutrient supply the termination of slope progradation was a multiphased process triggered by a stagnation of the regional subsidence a reduction of water circulation followed by a sea level drop the influx of freshwater and the input of siliciclastics fluctuating salinity caused intermittently a biotically stressed environment

trace elements stable isotopes and clay mineralogy of the elles ii k t boundary section in tunisia indications for sea level fluctuations and primary productivity abstract trace elements and stable isotopes in bulk rocks and foraminifera bulk rock and clay mineral compositions are used as palaeoproxies to evaluate sea level fluctuations climatic changes and variations in primary productivity across the k t transition at elles ii in tunisia from 1 m 33 kyr below to 1 m 70 kyr above the k t boundary results on clay minerals major and trace elements stable isotopes in bulk rock samples e g ca cu zn rb sr zr ba 13c and 18o and in foraminifera sr ca 13c 18o indicate that the latest maastrichtian last 33 kyr in tunisia was marked by a relatively warm but humid climate and a rising sea level the transgressive surface is marked by deposition of a foraminiferal packstone just below the k t boundary followed by maximum flooding across the k t boundary red layer and black clay layer humid warm conditions accompanied the maximum flooding along with increased total organic carbon values and rapidly decreasing primary productivity at the k t boundary an impact event ir anomaly ni rich spinels spherules exacerbated already stressed environmental conditions leading to the mass extinction of tropical planktic foraminifera increasingly more humid conditions prevailed within the lowermost danian zone p0 50 kyr culminating in a sea level lowstand near the top of p0 a slow recovery of the ecosystem in zone p1a coincided with a rising sea level and gradually less humid climatic conditions

synchroneity of climatic change and extinctions in the late triassic although the late triassic was a time of widespread aridity evidence exists for a significant increase in rainfall during the middle to late carnian upper triassic playa lake sediments were interrupted by late carnian fluviatile sandstones with erosive bases and high kao linite illite ratios there was also an increase in the clastic component of marine sequences during this interval middle and upper carnian marine carbonates show an extreme depletion in 13 c values consistent with increased fresh water influx large scale karstic phenomena in limestone areas subaerially exposed during the late triassic are a further indication of increased rainfall important faunal and floral changes occurred during the carnian norian interval marine invertebrate turnover was greatest at the lower middle carnian boundary and terrestrial extinctions were concentrated at the carnian norian boundary the cause of this carnian pluvial episode may have been related to the rifting of pangea through disruption of atmospheric and oceanic circulation patterns eustatic changes or the effects of volcanism associated with rifting a change in surface ocean temperature salinity or ph or habitat loss may have caused the decline of many shallow marine invertebrates at the start of the middle carnian a return to arid conditions at the carnian norian boundary would account for the turnover among terrestrial vertebrates and plants

on balanced and unbalanced accommodation peat accumulation ratios in the cretaceous coals from gates formation western canada and their sequence stratigraphic significance coal composition was investigated by means of photometric and maceral analyses on closely spaced lithotype based strip samples over the full thickness of several paralic coal seams from the cretaceous gates formation of the western canadian sedimentary basin the aim of this investigation was to test various methods of identifying accommodation trends in coal and use them to refine sequence stratigraphic interpretation of continental sediments conventional sequence stratigraphy derives its subdivisions and significant surfaces from the records left by relative sea level oscillations these records either do not project into the continental realm or are difficult to recognise in clastic non marine sediments paralic coal seams have been selected to study this problem because they are not entirely removed from marine influence and compared with most inorganic deposits coal has stored a greater wealth of information that can be analysed at a higher level of resolution the study has led to the identification of five new surfaces with chronostratigraphic potential in the sequence stratigraphic analysis of non marine sediments two of these surfaces called paludification surface pas and terrestrialisation surface tes occur at the bases of the investigated coal seams while two other surfaces referred to as non marine flooding surface nfs and give up transgressive surface guts form the tops of the coal the fifth and probably most important new surface called the accommodation reversal surface ars is independent of any particular facies and may either coincide with some of the other surfaces or occur separately the proportion of detrital minerals has been used as the chief discriminator between different mire types and accommodation trends other useful indicators of mire type and peat dispersal have been the proportions of sporinite and inertodetrinite as well as some derived maceral and or mineral ratios e g the groundwater influence index and the tissue preservation index isometamorphic variations of telovitrinite reflectance and fluorescence as well as their coefficients of variation were also found to contribute to the identification of cyclic shifts between balanced and unbalanced accommodation peat accumulation ratios some of these cycles which are backed up by clastic stratigraphy appear to correspond to the development of shallowing upward and deepening upward parasequences superimposed high frequency low amplitude perturbations in the coal cycles relate to smaller scale accommodation cycles of sub parasequence level not always recognised in non marine strata these sub parasequence coal cycles do not always continue the shallowing upward trend typical of conventional parasequences several coals were found to contain stacks of small scale cycles with upward increasing accommodation signatures either in their lower or upper halves or over the whole seam section

triassic jurassic weathering and clay mineral dispersal in basement areas and sedimentary basins of southern sweden abstract the basement rocks of southern sweden were deeply weathered in late triassic through cretaceous times and possibly even earlier sub mesozoic saprolites formed presumably due to long term warmth and humidity in conjunction with decomposition of abundant organic matter and subsequent infiltration of acidic water the upper parts of the weathering profiles were subjected to intense leaching and kaolinitisation whereas the less evolved deep weathering front is enriched in smectite thus any erosion prior to full regolith development or extraordinary deep erosion released less developed smectite rich weathering material to the late triassic jurassic receiving basins mesozoic sedimentary successions in southern sweden show high detrital smectite and or kaolinite contents moderate illite contents and low chlorite contents compatible with expected mid latitude warm equable greenhouse conditions norian and older triassic haematite cemented continental arkoses and smectite dominated clays smectite kaolinite were clearly formed in arid settings from the rhaetian and throughout the jurassic humid onshore conditions sustained abundant plant and peat accumulation early diagenetic meteoric flushing and intense chemical weathering kaolinite is therefore a dominating detrital clay mineral in these sedimentary successions kaolinite illite chlorite and smectite i s minor quantitative variations in clay mineralogy within the humid climate rhaetian jurassic sedimentary successions are difficult to interpret in deltaic coal bearing successions the detrital clay mineral composition is conspicuously constant kaolinite illite chlorite possibly due to post depositional clay mineral transformation conversely in shallow marine deposits some quantitative variation is notable kaolinite illite variable smectite chlorite this may reflect that the original detrital composition was better preserved in shallow marine settings smectitic clay minerals associated with gypsum and caliche nodules ambiguously indicate increased aridity towards the end of the jurassic

environmental controls on clay mineralogy of an early jurassic mudrock blue lias formation southern england we present a dataset including clay mineralogy gamma ray spectrometry organic matter content and magnetic susceptibility of the hettangian to lowest sinemurian successions of dorset and somerset southern uk blue lias formation bristol channel and wessex basins in both areas the clay assemblages comprise predominantly detrital illite kaolinite and illite smectite mixed layers clays probably originated from the erosion of the hercynian massifs the relative proportions of kaolinite and illite being modulated by arid humid climatic fluctuations the organic matter om content types ii to iv ranges up to 12 in both areas a clear stratigraphical trend in clay mineral assemblages is apparent in somerset whereas in dorset sharp contrasts between adjacent horizons and a greater dilution by carbonate mask the long term evolution correlations between both areas based on similar vertical trends in clay mineral abundance support the suggestion of a hiatus within the angulata zone of the dorset succession as expected the kaolinite illite ratio correlates with the th k ratio deduced from gamma ray spectrometry however significant departures from the correlation occur in om rich intervals suggesting that th may be partly adsorbed on to om particles surprisingly high magnetic susceptibility correlates with abundant kaolinite not with fe rich clays indicating either that kaolinite is accompanied by a soil inherited magnetisable phase possibly iron oxide or that illite rich rocks are more strongly diluted by carbonate than are kaolinite rich strata

the beysehir hoyran hadim nappes genesis and emplacement of mesozoic marginal and oceanic units of the northern neotethys in southern turkey the beysehir hoyran hadim nappes crop out over 700 km from nw to se above a regionally autochthonous tauride carbonate platform the beysehir hoyran nappes begin with a thrust sheet c 400 m of mainly redeposited carbonates quartzose sandstones and mudstones of mid late triassic age interpreted as a proximal slope base of slope succession above is a thrust sheet c 1 km of middle upper triassic intermediate acidic extrusive rocks volcaniclastic rocks and minor pelagic carbonates interpreted as a continental rift thin

comparison of clay mineral stratigraphy to other proxy palaeoclimate indicators in the mesozoic of nw europe this paper reviews the opportunities and pitfalls associated with using clay mineralogical analysis in palaeoclimatic reconstructions following this conjunctive methods of improving the reliability of clay mineralogical analysis are reviewed the mesozoic succession of nw europe is employed as a case study this demonstrates the relationship between clay mineralogy and palaeoclimate proxy analyses may be integrated with clay mineralogical analysis to provide an assessment of aridity humidity contrasts in the hinterland climate as an example the abundance of kaolinite through the mesozoic shows that while interpretations may be difficult the mesozoic climate of nw europe was subject to great changes in rates of continental precipitation we may compare sedimentological facies mineralogy geochemistry indicators of palaeoprecipitation with palaeotemperature estimates the integration of clay mineralogical analyses with other sedimentological proxy indicators of palaeoclimate allows differentiation of palaeoclimatic effects from those of sea level and tectonic change we may also observe how widespread palaeoclimate changes were whether they were diachronous or synchronous how climate sea level and tectonics interact to control sedimentary facies and what palaeoclimate indicators are reliable

the mid hungarian line a zone of repeated tectonic inversions abstract the mid hungarian line is a major tectonic feature of the intra carpathian area separating two terranes of different origin and tectonic structure although this tectonic line was known from borehole records it has not been described in seismic sections the study presents interpreted seismic lines crossing the supposed trace of the mid hungarian line these seismic sections show north dipping normal faults and thrust faults as well as cross cutting young strike slip faults a complex tectonic history is deduced including intra oligocene early miocene thrusting middle miocene extension local late miocene inversion and late miocene pliocene normal faulting and left lateral wrenching in the light of our seismic study we think that the best candidate for the mid hungarian line is a north dipping detachment fault beneath large masses of neogene volcanics the auxiliary structures to the north seen on seismic sections suggest that it moved as a south vergent thrust fault during the palaeogene early miocene which later was reactivated as a set of normal faults the northern alcapa unit overrode the southern tisza dacia unit along this fault zone the same relative positions are observed in the northern termination of the line other structures along the supposed trace of the line are north dipping normal or strike slip faults which frequently were reactivated as smaller thrust faults during the late neogene palaeogene early miocene thrusting along the line might be the result of the opposite tertiary rotations of the two major units as suggested by palaeomagnetic measurements and earlier models

the influence of half graben syn depositional tilting on thickness variation and seam splitting in the brunner coal measures new zealand abstract the brunner coal measures buller coalfield new zealand comprise a fluviatile sequence of eocene age that is generally 30 100 m thick the sequence rests on basement and is dominated by coarse to granular very coarse sandstone the measures contain one mineable coal seam the buller seam member that is laterally extensive and up to 20 m thick it is characterized by simple splitting with a thin upper split a thick lower split and a split separation of up to 30 50 m locally the buller seam member exhibits splitting to form numerous thin seams areas of shale out comprise thin linear belts between areas of thick coal with a low ash yield the coincidence of faults and maximum thickness of seam isopachs indicates that the thickness and splitting characteristics of the buller seam member were largely controlled by syn depositional faulting and tilting of small half graben blocks thickness variation in basal sequences is primarily due to syn depositional faulting syn depositional tilting of fault blocks also influenced the migration of river channels and hence the stacking and distribution of sandstone and locally thick mudstone units overlying coal

significance of late permian triassic facies zones in terrane reconstructions in the alpine north pannonian domain abstract the present day setting of the tectonic units terranes making up the pre neogene basement of the pannonian basin and the west carpathians is the result of large scale displacements during the alpine collisional phases to explain this setting based on various concepts a number of models have been proposed in the last decade most of them agree in an eastward escape of the north pannonian terrane from the alpine domain towards the pannonian during the palaeogene early miocene period in the present paper a reconstruction of the pre escape setting of the displaced terranes is presented based on facies zones in selected time slices from the late permian to the late triassic according to our reconstruction the inner west carpathian units were located east of the austroalpine units forming the northern shelf of the euhallstatt meliatic basin of the vardar oceanic branch the drauzug should have been located in a position much more external than its present day setting the transdanubian range was situated in the northern neighbourhood of the southern alps whereas the bukk may have been located adjacent to the nw dinarides the mid transdanubian zone is a major shear zone containing elements of the julian alps and sava folds nappe system and the inner dinaric ophiolitic melange although the nappe tectonism may have played an important role in the structural evolution of the north pannonian terrane this mechanism alone can hardly produce hundreds of kilometres of facies offset on the opposite sides of strike slip zones

unraveling the origin of carbonate platform cyclothems in the upper triassic durrenstein formation dolomites italy abstract facies analysis of the durrenstein formation central eastern dolomites northern italy indicates that this unit was deposited on a carbonate ramp as evidenced by the lack of a shelf break slope facies or a reef margin together with the occurrence of a molechfor biological association its deposition following the accumulation of rimmed carbonate platforms during the ladinian and early carnian marks a major shift in growth mode of the triassic shallow marine carbonates in the dolomites the durrenstein formation is characterized by a hierarchical cyclicity with elements strongly suggestive of an allocyclic origin including a subaerial exposure features directly above subtidal facies within meter scale cyclothems b purely subtidal carbonate cyclothems c symmetric peritidal carbonate cyclothems and d continuity of cyclothems of different orders through facies boundaries the durrenstein cyclothems are usually defined by transgressive and regressive successions and so most of them probably originated from sea level oscillations their allocyclic origin allows their use for high resolution correlations over distances up to 30 km a stratigraphic section in the tre cime di lavaredo area encompassing the upper part of the durrenstein formation and the lower part of the overlying raibl formation upper carnian was studied using time frequency analysis a strong milankovitch signal appeared when interference arising from a variable sedimentation rate was estimated and removed by tuning the short precession line in a spectrogram all of the principal periodicities related to the precession index and eccentricity calculated for 220 ma are present p1 21 9 ky p2 17 8 ky e1 400 ky e2 95 ky and e3 125 ky along with a peak at a frequency double that of the precession which is a predicted feature of orbitally forced insolation at the equator components possibly related to earth s obliquity at ca 35 ky and ca 46 ky are present as well the recovery of milankovitch periodicities allows reconstruction of a high resolution timescale that is in good agreement with published durations of the carnian based on radiometric ages the recognition of a milankovitch signal in the durrenstein and lower raibl formations as well as in other mesozoic carbonate platforms strongly supports a deterministic and predictable rather than stochastic control on the formation of carbonate platforms carbonate platforms might thus be used in the future for the construction of an astronomical time scale for the mesozoic

late quaternary climatic control on erosion and weathering in the eastern tibetan plateau and the mekong basin abstract high resolution siliciclastic grain size and bulk mineralogy combined with clay mineralogy rubidium strontium and neodymium isotopes of core md01 2393 collected off the mekong river estuary in the southwestern south china sea reveals a monsoon controlled chemical weathering and physical erosion history during the last 190 000 yr in the eastern tibetan plateau and the mekong basin the ranges of isotopic composition are limited throughout sedimentary records 87 sr 86 sr 0 7206 0 7240 and e nd 0 11 1 to 12 1 these values match well to those of mekong river sediments and they are considered to reflect this source region smectites illite chlorite and smectites kaolinite ratios are used as indices of chemical weathering rates whereas the bulk kaolinite quartz ratio is used as an index of physical erosion rates in the eastern tibetan plateau and the mekong basin furthermore the 2 5 6 5 m 15 55 m siliciclastic grain size population ratio represents the intensity of sediment discharge of the mekong river and in turn the east asian summer monsoon intensity strengthened chemical weathering corresponds to increased sediment discharge and weakened physical erosion during interglacial periods in contrast weakened chemical weathering associated with reduced sediment discharge and intensified physical erosion during glacial periods such strong glacial interglacial correlations between chemical weathering erosion and sediment discharge imply the monsoon controlled weathering and erosion

dips ramps and rolls evidence for paleotopographic and syn depositional fault control on the western kentucky no 4 coal bed tradewater formation bolsovian illinois basin abstract the western kentucky no 4 coal is a high volatile b to high volatile c bituminous coal that has been heavily mined along the southern margin of the western kentucky coal field the seam has a reputation for rolling floor elevation elongate trends of floor depressions are referred to as dips and rolls by miners some are relatively narrow and straight to slightly curvilinear in plan view with generally symmetric to slightly asymmetric cross sections others are broader and asymmetric in section with sharp dips on one limb and gradual ramp like dips on the other some limbs change laterally from gradual dip to sharp dip to offset of the coal lateral changes in the rate of floor elevation dip are often associated with changes in coal thickness and in underground mines changes in floor elevation are sometimes associated with roof falls and haulage problems in order to test if coal thickness changes within floor depressions were associated with changes in palynology petrography and coal quality the coal was sampled at a surface mine across a broad ramp like depression that showed down dip coal thickening increment samples of coal from a thick 150 cm down ramp and thinner 127 cm up ramp position at one surface mine correlate well between sample sites a distance of 60 m except for a single increment the anomalous increment 31 cm in the lower middle part of the thick coal bed contained 20 more lycospora orbicula spores the rolling floor elevations noted in the study mines are inferred to have been formed as a result of pre peat paleotopographic depressions syn depositional faulting fault controlled pre peat paleotopography and from compaction beneath post depositional channels and slumps although the association of thick coal with linear trends and inferred faults has been used in other basins to infer syn depositional faulting changes in palynology within increment samples of the seam along a structural ramp in this study provide subtle evidence of faulting within a specific increment of the coal itself the sudden increase in l orbicula produced by paralycopodites in a single increment of a down ramp sample of the western kentucky no 4 coal records the reestablishment of a rheotrophic mire following a sudden change in edaphic conditions paralycopodites was a colonizing lycopod which in this case became locally abundant after the peat was well established along a fault with obvious growth during peat accumulation because many coal mire plants were susceptible to sudden edaphic changes as might accompany faulting or flooding changes in palynology would be expected in coals affected by syn depositional faulting

illite in aridic soils desert dusts and desert loess abstract in some desert loess deposits notably those of central asia illite dominates the clay fraction in others such as in the near east and north africa illite is a minor component the interaction between desert loess deposits and aridic desert soils via desert dusts is used to explain the difference in illite contents vertical profile distribution of illite as well as vertical distributions of soluble and exchangeable potassium are taken to indicate that illite forms pedogenetically in the surface horizon of aridic soils once formed it is stable and accumulates it is postulated that the potassium required for the illitazation process is introduced by aeolian dusts the process is facilitated by wetting and drying cycles dusts originating in deserts where they are presently produced by desert weathering of various rocks are defined as primary or juvenile dusts they have low illite contents such are the dusts that are carried from the eastern sahara and sinai peninsula northeast towards the middle east where they form local loess deposits the central asian dusts on the other hand have been subjected to numerous cycles of deflation and deposition resulting in relatively long residence times in the pedogenic environment of aridic soils this results in the enrichment of these dusts with illite the central asian desert loess deposits that interact with these dusts are consequently enriched with illite similar processes of illite enrichment may have operated in other areas such as australia

changes in hydrocarbon maturity indices with coal rank and type buller coalfield new zealand abstract the buller coalfield south island new zealand is an inverted late paleogene basin that contains middle eocene bituminous coals which exhibit considerable variation in both coal rank across basin and coal type in seam twenty two fractionated bitumen extracts of brunner coal measures coal samples from 12 drillholes were analyzed by gc and gc ms to characterize the effect of coal rank and type on conventional hydrocarbon maturity indices at the beginning and end of the oil window 0 56 1 26 ro max the carbon preference index pristane phytane and isoprenoid n alkane ratios evolve throughout the high volatile bituminous b rank stage while other biomarker ratios 18 h 22 29 30 trisnorneohopane 17 h 22 29 30 trisnorhopane ts tm 18 h 21 h 30 norneohopane c 29 ts 17 h 21 h 30 norhopane and c 30 diahopane hopane do not show appreciable change in value until medium volatile bituminous rank various aromatic based ratios appear to be more effective in delineating rank throughout the entire oil window in particular the methylphenanthrene index and vitrinite reflectance are positively correlated over the entire bituminous rank range however subtle changes in depositional conditions variable coal type complicate these rank estimates within a given coal seam variation in cpi isoprenoid n alkane and hopane sterane ratios appear to be related to the hydrogen content of the coal while the homohopane index and the oleanane hopane ratio covary with sulfur content as with depressed vitrinite reflectance values mpi is similarly lowered in the perhydrous samples the mechanisms that control these hydrocarbon parameters during deposition and diagenesis are complex and convoluted however changes in bacterial activity and community with marine incursion appear to play an important role due to these anomalies none of the hydrocarbon maturity indices calculated can be singularly used to constrain coal rank

peat accumulation on a drowned coastal braidplain the mullins coal upper carboniferous sydney basin nova scotia abstract the mullins coal lies within the braided fluvial south bar formation the lateral extent 15 km and thickness 2 m of the coal suggest that controls for peat accumulation were allogenic marine inundation of the distal braidplain as indicated by the high sulphur content of the coal and the occurrence of agglutinated foraminifera in associated shales caused ponding of freshwater near maximum marine transgression with accumulation of thick paralic peat across a stable platform of sandy fluvial sediments highstand parasequences with thin capping coals were subsequently incised beneath a sequence boundary as the braidplain readvanced the mullins coal thins and splits in association with muddy bayfill deposits eastward towards the glace bay syncline a long lived palaeotopographic element related to fault bounded basement blocks although relative sea level change controlled the stratigraphic position of the precursor peats differential tectonic subsidence and or compaction modified their extent thickness and quality

the aftermath of the carnian carbonate platform demise a basinal perspective dolomites southern alps in the dolomites of northernmost italy the carbonate platform growth came to a standstill late in the early carnian late triassic the response to this shutdown of shallow water carbonate production in the interplatform basins is largely unknown because erosion has removed most of the soft basinal sediments giving rise to today s scenic landscape of the dolomites mapping in the central part of the dolomites and newly available core material has recently revealed a wellpreserved succession of basinal rocks within the heiligkreuz hospiz basin ital ospizio di santa croce basin in this paper the regional depositional nature of arrested carbonate platform production is reconstructed by tracing its sedimentological record across the slope and into the basin the uppermost st cassian formation the time equivalent basinal rocks to the prograding carbonate platforms is overlain by the heiligkreuz formation whose basal succession was deposited in a restricted and oxygen depleted environment immediately post dating the platform demise the succession consists mainly of mudrocks marlstones and peloidal packstones with abundant low diversity ostracod and pelecypod fauna and early diagenetic dolomite c and o isotope values of the basal heiligkreuz formation post dating platform demise average 2 ae4 and 2ae4 respectively and largely overlap the isotopic composition of st cassian carbonates a shift toward slightly lower d 13 c values in the heiligkreuz formation may reflect incorporation of isotopically depleted c released during bacterial sulphate reduction in the heiligkreuz sediments sedimentological palaeobiological and geochemical indices suggest that nearnormal marine conditions persisted long after the shutdown of shallow water carbonate platform growth although there are clear indications of severely reduced oxygen levels in the restricted heiligkreuz hospiz interplatform basin the early carnian platform demise induced a distinct switch in the locus of carbonate production from the shallow water platform and slope to the basin floor and a decrease in the availability of dissolved oxygen in the basinal waters it is inferred that anoxia extended at least temporarily to the top of the carbonate slope as indicated by the onlap of normal marine mounds by dark marlstones of the basal heiligkreuz formation

distribution of clay minerals in early jurassic peritethyan seas palaeoclimatic significance inferred from multiproxy comparisons article i nfo a set of published unpublished and new clay mineral data from 60 european and mediterranean localities allows us to test the reliability of clay minerals as palaeoclimatic proxies for the pliensbachian toarcian period early jurassic by reconstructing spatial and temporal variations of detrital fluxes at the ammonite biochronozone resolution in order to discuss their palaeoclimatic meaning a compilation of low latitude belemnite 18 o 13 c mg ca and 87 sr 86 sr values is presented for the first time for the whole pliensbachian toarcian period once diagenetic and authigenic biases have been identified and ruled out kaolinite content variation is considered as a reliable palaeoclimatic proxy for the early jurassic major kaolinite enrichments occur during times of low 18 o high mg ca and increasing 87 sr 86 sr implying warm climates and efficient runoffs during the davoei falciferum and bifrons zones conversely cooler and drier times such as the late pliensbachian or the late toarcian are characterized by low hydrolysis of landmasses and correspond to kaolinite depleted intervals secondary factors as modifications of sources or hydrothermalism may sporadically disturb the palaeoclimatic signal e g in the bakony area during the late pliensbachian in addition a spatial comparison of clay assemblages displays significant kaolinite enrichments towards northern parts of the peritethyan realm probably related to the latitudinal zonation of hydrolyzing conditions this implies enhanced runoffs on northern continental landmasses that reworked kaolinite rich

climatic and biotic change in the late triassic generally arid conditions that pervaded much of europe and north america during the late triassic were interrupted by a wet monsoonal climatic phase during middle and late carnian times extensive fluviatile sandstones deposited at this time throughout the region occur within a thick sequence of playa lake mudstones the sandstones occasionally contain kaolinite suggesting a humid climate an extreme 13 c depletion in a shallow marine sequence of this age in israel has been interpreted as evidence for an influx of freshwater a widespread change from carbonates to clastics in marine sequences at this time may also be climate related water course cave systems in limestone areas exposed during the late triassic indicate high levels of runoff during the middle and late carnian the marine invertebrate fauna shows a significant turnover at the end of the early carnian the terrestrial fauna and flora were relatively unaffected at this time but subsequently diversified prior to a major biotic turnover at the carnian norian boundary these periods of biotic change appear to be synchronous with the onset and cessation of a carnian humid phase the change to a monsoonal climate during this interval has been documented over more than 90 of longitude between 5 and 50 north of the triassic equator it may have been caused by rising atmospheric co 2 levels due to volcanism associated with the incipient dispersal of pangaea