chemostratigraphy a method to improve interwell correlation in barren sequences a case study using onshore duckmantian stephanian sequences west midlands u k abstract chemostratigraphy has been applied to onshore duckmantian stephanian successions encountered in outcrop and penetrated by two boreholes from the west midlands u k these successions represent the onshore equivalents of the barren red measures which are important hydrocarbon bearing sequences in the southern north sea much is known about the onshore successions in terms of sedimentology mineralogy and provenance and thus they provide the ideal test for the validity of chemostratigraphy as a stratigraphic tool reliable inorganic geochemical data have been acquired from geochemical analyses of core sidewall core and cuttings samples with 19 elements being determined stratigraphic variations in elemental concentrations are compared with known variations in the mineralogical data the established lithostratigraphic units of the duckmantian stephanian intervals can also be recognized from the geochemical data and by using these data can be subdivided further this results in an independent chemostratigraphic correlation being established for the two boreholes which has been assessed statistically by discriminant function analysis from the geochemical and mineralogical data distinct changes in provenance are identified within the upper carboniferous successions the sediments of the coal measures were derived from a north westerly and westerly source caledonian whereas the etruria formation sediments came from the wales brabant massif the sediments having mixed caledonian and cadomian characteristics eventually these sediments were replaced by sediments from a southern hercynian source halesowen and salop formations

geochemical facies analysis of fine grained siliciclastics using th u zr rb and zr rb sr ratios abstract abundance of the trace elements zr rb sr th and u may provide insight into the sedimentological origin of fine grained siliciclastic sediments provided that the units are derived from similar source areas as demonstrated here with suites of the fine grained jurassic and cretaceous rocks from the barents sea and svalbard zr rb ratios can be interpreted to indicate grain size variations while zr rb sr values reflect variations in the siliciclastic versus carbonate contents the th u ratio can be applied as an indicator of the redox conditions in 3d plots such as presented here the interplay between these geochemical factors can be interpreted in terms of the sedimentological evolution of the depositional basin the geochemical facies analyses show that similar depositional conditions existed on the jurassic shelf in the two studied localities the succeeding prodeltaic cretaceous beds were generally coarser grained and deposited in ventilated depositional conditions

shelf construction in a foreland basin storm beds shelf sandbodies and shelf slope depositional sequences in the upper cretaceous mesaverde group book cliffs utah the upper cretaceous campanian kenilworth member of the blackhawk formation mesaverde group is part of a series of strand plain sandstones that intertongue with and overstep the shelfal shales of the western interior basin of north america analysis of this section at a combination of small sedimentological and large stratigraphical scales reveals the dynamics of progradation of a shelf slope sequence into a subsiding foreland basin four major lithofacies are present in the upper mancos and kenilworth beds of the book cliffs a lag sandstone and channel fill shale lithofacies constitutes the thin basal transgressive sequence which rests on a marine erosion surface it was deposited in an outer shelf environment shale interbedded sandstone and shale and amalgamated sandstone lithofacies were deposited over the transgressive lag sandstone lithofacies as a wave dominated delta and its flanking strand plains prograded seaward analysis of grain size and primary structures in kenilworth beds indicates that there are four basic strata types which combine to build the observed lithofacies the fine to very fine grained graded strata of the interbedded facies are tempestites deposited out of suspension by alongshelf storm flows geostrophic flows there is no need to call on cross shelf turbidity currents density underflows to explain their presence very fine to fine grained hummocky strata are likewise suspension deposits created by waning storm flows but were deposited under conditions of more intense wave agitation on the middle shoreface cross strata sets in this region are bed load deposits that accumulated on the upper shore face in the surf zone lag strata are multi event bed load deposits that are the product of prolonged storm winnowing they occur on transgressive surfaces while the graded beds are tempestites in the strict sense all four classes of strata are storm deposits the distribution of strata types and their palaeocurrent orientations suggests a model of the kenilworth transport system driven by downwelling coastal storm flows and probably by a northeasterly alongshore pressure gradient the stratification patterns shift systematically from upper shoreface to lower shoreface and inner shelf lithofacies partly because of a reduction in fluid power expenditure with increasing water depth but also because of progressive sorting which resulted in a decrease in grain size in the sediment load delivered to successive downstream environments the kenilworth member and an isolated outlier the hatch mesa lentil constitute a delta prodelta shelf depositional system their rhythmically bedded lenticular sandstone and shale successions are a prodelta shelf facies and may be prodelta plume deposits major upper cretaceous sandstone tongues in the book cliffs are underlain by erosional surfaces like that beneath the blackhawk formation which extend for many tens of kilometres into the mancos shale these surfaces are the boundaries of upper cretaceous depositional sequences the sequences are large scale genetic stratigraphic units they result from the arranging of facies into depositional systems the depositional systems are in turn stacked in repeating arrays which constitute the depositional sequences the anatomy of these foreland basin sequences differs

triassic 40ar 39ar ages from the sakaigawa unit kii peninsula japan implications for possible merger of the central asian orogenic belt with large scale tectonic systems of the east asian margin the 218 4 0 4 228 8 0 9 and 231 9 0 7 ma 40ar 39ar laser probe pseudo plateau ages 2 49 63 39ar release of very low grade meta pelitic whole rocks from the sakaigawa unit date high p t metamorphism we argue that this event occurred in a subduction accretion complex not along the east asian continental margin but on the pacific side of the proto japan superterrane proto japan was a permian magmatic arc presently dispersed in the japanese islands which also contained older subduction accretion complexes the arc system was fringing but not yet part of the eurasian continent the middle to late triassic high p t tectono metamorphic event was partly coeval with proto japan s collision with proto eurasia along the southward extension of the central asian orogenic belt causing the main metamorphism in the hida oki terrane it is possible that this system continued via the cathaysia block china to indochina the late permian to middle triassic indosinian event might stem from docking of pacific derived terranes with southeast asia s continental margin the concept of the proto japan superterrane implies that the qinling dabie sulu suture zone joined the central asian orogenic belt to the east of the north china craton and did not continue to japan as commonly assumed

geochemical and mineralogical variations as indicators of provenance changes in late quaternary deposits of se po plain combined geochemical and mineralogical characterisation of mudstone prone successions can provide suitable indicators of sediment provenance a case study from the late quaternary depositional sequence of southeastern po plain shows that major changes in geochemical and mineralogical composition can be ascribed to changes in sediment dispersal patterns occurring during the last 30 ka in response to fluctuating sea level the po river with a mixed contribution from the alpine and apenninic chains and its southern tributaries flowing from the apennines acted as the major feeders for the study area during the late quaternary chromium and nickel among trace elements and serpentine and dolomite among minerals appear as the major provenance indicators for the study succession allowing distinction of an apenninic chromium and serpentine poor province from a mixed alpine apenninic po related chromium and serpentine rich province the relatively low cr al2o3 and serpentine silicate ratios recorded in sediments of late pleistocene age 30 ka bp which accumulated at the last glacial maximum suggest that during lowstand times and early stages of transgression the southeastern po plain was beyond the po river influence being fed uniquely by rivers of apenninic provenance increasing cr al2o3 and serpentine silicate ratios recorded within back barrier transgressive deposits 8 10 ka bp in the comacchio and ravenna sectors reflect a major change in sediment supply taking place during the holocene when partially barred environments largely connected with the open sea became established in the study area and po derived detritus was delivered to estuaries and lagoons by littoral drift maximum chromium and serpentine values are recorded at peak transgression and during the following sea level highstand 6 ka bp present when sediment supply exceeded the rate at which new accommodation space was created leading to extensive po delta progradation the drop in cr al2o3 and serpentine silicate ratios recorded in some cores at top of the holocene succession reflects the local reestablishment behind the prograding po delta complexes of an alluvial plain drained by rivers of apenninic provenance as a result of distributary channel switching and delta lobe abandonment geochemical and mineralogical analyses show negligible compositional variations between pleistocene and holocene deposits landward of the line of maximum marine incursion especially close to the basin margin in these instances sample composition throughout the entire stratigraphic succession clearly suggests an ongoing supply from the adjacent apenninic chain comparison with sand compositional analyses from major sand bodies of the same stratigraphic succession highlights the complementary but fundamental role of geochemical and mineralogical characterisation of clays for provenance research

synthetic heavy mineral stratigraphy applications and limitations abstract a multi disciplinary study of the dominantly fluvial lower triassic otter sandstone formation east devon uk is presented the approach integrates a variety of methods including sedimentology conventional heavy mineral analysis single grain microprobe analysis and elemental whole rock geochemistry icp aes and icp ms a species level conventional heavy mineral study is compared to a whole rock geochemical analysis for the corresponding samples to investigate whether or not heavy mineral compositions can be discriminated from elemental whole rock data the comparison provides sufficient evidence that the absolute and relative abundance of some of the heavy minerals apatite iron titanium oxides monazite and zircon can be discriminated geochemically the established element mineral relationships are used to construct both synthetic heavy mineral assemblages and synthetic heavy mineral index values from the geochemical data which show considerable similarity to those of the conventional heavy mineral analysis the presented synthetic heavy mineral logs display intraformational packages that enable subdivision of this barren continental succession furthermore the observed subdivision is correlatable over a considerable distance when extended into the offshore wessex basin the chemical approach unquestionably lacks the sensitivity of conventional heavy mineral analysis however by comparison it is rapid this novel approach demonstrates that synthetic heavy mineral stratigraphy based as here on a well constrained stratotype has considerable potential for creating high resolution correlations in both outcrops and the subsurface and may be of significant value to people working with reservoir characterisation

the marine permian of east and northeast asia an overview of biostratigraphy palaeobiogeography and palaeogeographical implications abstract the permian marine biostratigraphy faunal successions and mutual correlations where possible throughout east and northeast asia are synthesized region by region based on both published literature and the author s field observations in certain parts of the region the correlation of the permian marine successions of ne asia with the permian international timescale and in particular with gondwanan permian marine sequences remains a major challenge due to profound marine provincialism during the permian however by employing biogeographically mixed faunas from east asia se mongolia ne china south primorye of far east russia and the south kitakami terrane of japan as biostratigraphic gateways coupled with some bipolarly and bi temperately shared permian marine taxa and faunas it has been possible to correlate with reasonable confidence some of the high palaeolatitude permian marine rock units and faunas of ne asia with those of the tethyan region and gondwana palaeobiogeographically the permian marine faunas of east and ne asia are assigned to four major provinces verkolyman sino mongolian japanese cathaysian and panthalassan provinces on the basis of their palaeogeographical distribution patterns and characteristics of faunal assemblages of these the sino mongolian japanese province has considerable significance for regional palaeogeographical plate tectonic and palaeoceanographical reconstructions during the middle permian because of its conspicuously mixed cool and warm water marine biota the origin of this biogeographically mixed marine biota is interpreted to have resulted from a combination of some key factors including the increased tectonic convergence between the bureya jiamusi terrane and the sino korean platform during the permian and the intermingling of both warm and cold water ocean currents off the eastern coastal areas of the bureya jiamusi terrane and the sino korean platform during the middle permian

geochemical correlation in deltaic successions a reality check whole rock geochemical analysis can aid the stratigraphic correlation of faunally barren successions compared to petrographic techniques or heavy mineral separations such analysis is quick and objective yet rarely has the reliability of the method been tested against unequivocal correlations we have applied it to the kenilworth member of the upper cretaceous blackhawk formation a well exposed and easily correlated 100 m thick unit in the deltaic successions of the book cliffs utah united states this is the first evaluation of geochemical analysis as an aid to sequence stratigraphic interpretation at the parasequence scale from the geochemistry alone it is not possible with statistical confidence to separate individual parasequences or systems tracts nor the fluvial incised valley from the marine shoreface units the magnitude of geochemical variation in a single sandstone bed over a 30 m lateral traverse is as great as vertically through an entire parasequence y nb rb and ti abundances are inversely correlated with grain size thus geochemical signatures follow sedimentological trends and distal parts of a parasequence appear distinct from proximal parts y ratios compensate for this grain size effect but introduce confusing distortions for elements such as zr that are not correlated with grain size contrary to some predictions zr is as common in the finest grained units as the coarsest and sr is not correlated with ca in some sections sr is also inversely correlated to grain size and cannot be used as an indicator for cement abundance

provenance of a permian accretionary complex nishiki group of the akiyoshi belt in southwest japan and paleogeographic implications abstract the akiyoshi belt in the inner zone of southwest japan is made up of a permian accretionary complex the main component of which is the late permian nishiki group that mainly consists of sandstone mudstone felsic tuff and a minor amount of chert and conglomerate we employ multiple methods which includes sandstone petrography detrital garnet composition and detrital zircon u pb dating to investigate the likely sources of these terrigenous deposits and to reconstruct the paleogeographic link between the proto japan and the east asian continent the highly immature late permian sandstones are interpreted to derive from multi type source rocks that include felsic igneous rocks basalts sedimentary rocks and low to medium grade metamorphic rocks in proximal locations the detrital zircon u pb results show that all samples contain a dominant early to late permian zircon population 294 254 ma and these zircons are interpreted to be derived from an active volcanic arc which was most likely caused by subduction of the paleo pacific plate beneath the south china block we found that spessartine rich almandine garnets and almandine garnets dominated assemblages in the lower unit changed to grossular andradite garnets dominated assemblage in the upper unit which was caused by a progressive uplifting and denudation of the permian volcanic arc

middle miocene denudation of the higher himalayan crystallines revealed by chemical composition of detrital garnets from the siwalik foreland basin sediments western and central nepal abstract the middle miocene to early pleistocene siwalik group is composed of sediments deposited in the himalayan foreland basin in this study the heavy mineral assemblage and chemical composition of detrital garnets from the sandstones in the lower siwalik sub group which are exposed along the karnali river in western nepal and the tinau khola in central nepal are studied and the provenance shift during the middle miocene is discussed the heavy mineral assemblage in the lower section of the lower siwalik sub group is characterized as predominantly zircon tourmaline rutile chemical analysis of the detrital garnets showed a monomodal almandine rich composition with low pyrope prp

provenance of permian sandstones south kitakami terrane northeast japan implications for permian arc evolution abstract the sandstone petrography of the permian sequence of the south kitakami terrane skt suggests the disrupted development of a magmatic arc and subsequent scattering of the arc along the northern margin of the sino korea continent the skt in northeastern japan is a stratigraphic terrane with well developed coherent sequences of silurian to lower cretaceous extent on a pre silurian basement while most of the pre tertiary terranes of the japanese islands are regarded as accretionary in origin the permian deposits of the skt are particularly well developed and unconformably overlie carboniferous strata these permian deposits are overlain by lower triassic sediments and then upper triassic and jurassic sediments with local unconformities the permian system is divided into lower middle and upper permian units on the basis of lithofacies and fusulinid zonation the lower permian is composed of sandstone mudstone and limestone with a basal conglomerate the middle permian unit is subdivided into a lower sequence consisting of massive sandstone and an upper sequence of limestone or mudstone associated with thick conglomerates the upper permian unit is mainly composed of massive mudstone although sandstone and conglomerates are predominant near the top of the unit the provenance of the permian sandstones in the skt was investigated based on the petrography and chemical composition of detrital pyroxene grains the lower permian sandstones can be divided into two petrofacies based on petrographic character quartzose lithic sandstones derived from pre permian rocks and volcanolithic sandstones dominated by andesitic fragments suggestive of a magmatic arc provenance from the upper middle to upper permian the sandstone composition changes upwards from polymictic quartzofeldspathic to feldspathic detritus derived from the pre permian felsic volcanics and from contemporaneous magmatic arc volcanic plutonic rocks are mixed in various proportions and deposited as middle permian sediments the compositional variation within the permian sequence reflects progressive denudation from undissected to dissected magmatic arc the triassic to jurassic sandstones are derived from a continental provenance the permian jurassic sequences overall therefore records the transition of the tectonic setting of the skt from its development as an oceanic magmatic arc in the permian to its accretion with a continental block by the end of the triassic this tectonic history and paleobiogeographic data suggest that the skt may have originated as one of the terranes along the northern margin of the sino korea block

generic relationships in the mineral chemical stratigraphy of turbidite sandstones ratios of abundance of hydraulically and diagenetically equivalent heavy minerals apatite tourmaline garnet zircon from deep water sandstones of similar age and derived from the same overall source terrain have contrasting trends the differences are explained by contrasting sediment transport paths deep water sandstones with fluctuating heavy mineral ratios are inferred to be derived directly from alluvial basins bypassing any contemporaneous shallow marine shelf deep water sandstones with homogeneous heavy mineralogy are inferred to be fed by sediment that originally accumulated on shallow marine shelves but was subsequently mixed

tectonometamorphic evolution of the permo triassic songrim indosinian orogeny evidence from the late paleozoic pyeongan supergroup in the northeastern taebaeksan basin south korea the deformed and metamorphosed middle pennsylvanian to early triassic rocks of the pyeongan supergroup occurring in northeastern flank of the paleozoic taebaeksan basin east central south korea record the impact of the late permian triassic songrim indosinian collisional orogeny in the eastern eurasia margin analysis of meso and microstructures and their relationship with porphyroblast growth has revealed that these metasedimentary rocks were affected by four deformation events d1 d4 during the polyphase deformations successive foliations with alternately steep s1 and s3 and flat lying s2 and s4 orientations were produced with growth of chloritoid andalusite and kyanite porphyroblasts during d1 and d2 and growth of garnet staurolite and andalusite porphyroblasts during d3 and d4 shrimp u pb detrital zircon ages 330 310 ma from metapelites in the oldest unit of the pyeongan supergroup in the study area combined with the previous data on sandstone compositions indicate magmatic activity that was contemporaneous with the initial deposition of the pyeongan supergroup this also suggests that the pyeongan supergroup was deposited in an arc related foreland basin at an active continental margin during the late carboniferous and permian time two contractional deformation events d1 and d3 and two events related to gravitational flattening d2 and d4 along with barrovian type medium pressure regional metamorphism may have resulted from the late permian triassic songrim orogeny related to collision between the north and south china blocks and or collision between the eastern eurasia margin and the proto japan terrane

palaeozoic and mesozoic tectonic evolution and palaeogeography of east asian crustal fragments the korean peninsula in context east and southeast asia comprises a complex assembly of allochthonous continental lithospheric crustal fragments terranes together with volcanic arcs and other terranes of oceanic and accretionary complex origins located at the zone of convergence between the eurasian indoaustralian and pacific plates the former wide separation of asian terranes is indicated by contrasting faunas and floras developed on adjacent terranes due to their prior geographic separation different palaeoclimates and biogeographic isolation the boundaries between asian terranes are marked by major geological discontinuities suture zones that represent former ocean basins that once separated them in some cases the ocean basins have been completely destroyed and terrane boundaries are marked by major fault zones in other cases remnants of the ocean basins and of subduction accretion complexes remain and provide valuable information on the tectonic history of the terranes the oceans that once separated them and timings of amalgamation and accretion the various allochthonous crustal fragments of east asia have been brought into close juxtaposition by geological convergent plate tectonic processes the gondwana derived east asia crustal fragments successively rifted and separated from the margin of eastern gondwana as three elongate continental slivers in the devonian early permian and late triassic late jurassic as these three continental slivers separated from gondwana three successive ocean basins the palaeo tethys meso tethys and cenotethys opened between these and gondwana asian terranes progressively sutured to one another during the palaeozoic to cenozoic south china and indochina probably amalgamated in the early carboniferous but alternative scenarios with collision in the permo triassic have been suggested the tarim terrane accreted to eurasia in the early permian the sibumasu and qiangtang terranes collided and sutured with simao indochina east malaya in the early middle triassic and the west sumatra terrane was transported westwards to a position outboard of sibumasu during this collisional process the permo triassic also saw the progressive collision between south and north china with possible extension of this collision being recognised in the korean peninsula culminating in the late triassic north china did not finally weld to asia until the late jurassic the lhasa and west burma terranes accreted to eurasia in the late jurassic early cretaceous and proto east and southeast asia had formed palaeogeographic reconstructions illustrating the evolution and assembly of asian crustal fragments during the phanerozoic are presented d 2005 international association for gondwana research published by elsevier b v all rights reserved

detrital garnet and chromian spinel chemistry of permian clastics in the renge area central japan implications for the paleogeography of the east asian continental margin abstract the japanese islands comprise a complex assembly of allochthonous continental shelf deposits and subduction related accretionary complexes the paleogeography of permian clastic strata was restored based on chemical analysis of detrital garnets and chromian spinels which are useful for provenance discrimination detrital garnet assemblages from the permian clastic rocks in japan are characterized by a grandite rich assemblage and a grandite poor assemblage most trench fill deposits in permian accretionary complexes contain the grandite poor assemblage which is composed of spessartine rich almandine grossular rich almandine and rarely pyrope rich almandine and is commonly associated with chromian spinels and volcanic rock fragments it is suggested that the sediments were derived from a volcanic arc and associated non calcareous contact metamorphic rocks along the north china block where pelitic granulites including pyrope rich almandine garnets are extensively exposed in the northern margin ophiolite and high p t schist also crop out along the continental margin most permian shelf deposits and the trench fill deposits of the central part of the accretionary complexes in japan contain the grandite rich assemblage analyses suggest provenance from a calc alkaline volcanic arc and association with calcareous contact metamorphic rocks including skarn deposits sediments lack ophiolite detritus a part of the grandite poor trench fill deposits of the accretionary complexes is overlain by grandite rich clastic rocks this indicates that the grandite rich detritus increased and the supply extended through the fore arc basin to the trench the trench fill deposits in the northernmost part of the permian accretionary complex in the renge area yield a grandite poor assemblage particularly uvarovite rich andradite garnets and chromian spinels derived from a back arc basin basalt which is very similar to the clastic composition of the permian back arc basin strata of japan hence we conclude that a back arc basin existed in the northernmost region of the permian subduction zone along the north china block

smithian and spathian early triassic ammonoid assemblages from terranes paleoceanographic and paleogeographic implications early triassic paleobiogeography is characterised by the stable supercontinental assembly of pangea however at that time several terranes such as the south kitakami massif sk south primorye sp and chulitna respectively and presently located in japan eastern russia and alaska straddled the vast oceans surrounding pangea by means of quantitative biogeographical methods including cluster analysis non metric multidimensional scaling and bootstrapped spanning network applied to smithian and spathian early triassic ammonoid assemblages we analyze similarity relationships between faunas and suggest paleopositions for the above cited terranes taxonomic similarities between faunas indicate that primary drivers of the ammonoid distribution were sea surface temperature and currents possible connections due to current controlled faunal exchanges between both sides of the panthalassa are shown and terranes such as sk sp and chulitna played an important role as stepping stones in the dispersal of ammonoids sk and sp terranes show strong sub equatorial affinities during the smithian thus suggesting a location close to south china at the same time the chulitna terrane shows strong affinities with equatorial faunas of the eastern panthalassa this paleoceanographic pattern was markedly altered during the spathian possibly indicating significant modifications of oceanic circulation at that time as illustrated by the development of a marked intertropical faunal belt across tethys and panthalassa

south kitakami region an allochthonous terrane in japan the pre cretaceous geology of the japanese islands may be interpreted as an accretion complex in which many terranes of several origins are juxtaposed and a number of allochthonous blocks are involved the south kitakami and abukuma regions of northeast japan and probably also silurian and devonian blocks in the kurosegawa fault zone and the border fault zone of the hida metamorphic terrane are the allochthonous blocks the stratigraphic sequence and paleobiofacies of the regions are similar to each other and their lithologic characters are of continental affinity but however are quite different from those of the other terranes having oceanic characters the south kitakami and abukuma regions have been fragments of a lost continent less remotely situated to gondwana during the middle paleozoic and may have drifted and incorporated with the other part of the japanese islands before late mesozoic to early tertiary igneous activity

changes in garnet chemistry show a progressive denudation of the source areas for permian jurassic sandstones southern kitakami terrane japan abstract garnet is a widespread detrital mineral in permian jurassic sandstones of the southern kitakami terrane electron probe microanalyses of these garnets show a gradual change of chemistry with the age of the sandstones the dominant garnet suites in permian triassic sandstones are grandite with some spessartine almandine in upper triassic sandstones however in lower jurassic sandstones pyrope almandine and spessartine almandine garnets are common whereas grandite garnets are absent garnet suites in middle to upper jurassic sandstones are dominated by pyrope almandine garnet the grandite dominant suites are associated with hornblende epidote and titanite whereas the pyrope almandine dominant suites are associated with biotite these grandite garnets are rich in andradite and have very low spessartine almandine and pyrope contents some of the grandite garnets are anisotropic with oscillatory zoning and sector twinning typical of calcic skarn deposits spessartine almandine garnets are common in low grade metamorphic rocks the diverse suites of pyrope almandine garnets up to 42 mol pyrope from the jurassic sandstones are typical of epidote amphibolite to granulite facies metamorphic rocks the chemistry and optical properties of garnets and the heavy mineral data show that low grade or contact metamorphic rocks such as skarns and hornfelses were widely exposed in the source areas of the permian triassic sandstones high grade metamorphic rocks including granulites and intrusive rocks appeared in early jurassic time and were widespread during the middle jurassic the critical change in the source areas for the southern kitakami terrane occurred during late triassic to early jurassic time and may correspond to the indosinian movements associated with the collision between the north china and south china blocks

coprolites from the upper osawa formation upper spathian northeastern japan evidence for predation in a marine ecosystem 5myr after the end permian mass extinction abstract lower triassic marine deposits which can potentially provide important information on the diversity and trophic structure of marine ecosystems following the end permian mass extinction are rarely exposed in the world given the sparse body fossil record from the lower triassic non body fossil evidences such as trace fossils for example may provide additional windows on fossil ecosystems herein the authors recently found dark amorphous lumps of various sizes ranging from a few millimetres to approximately 7 cm in maximum dimension from the offshore marine deposit of upper osawa formation spathian lower triassic in the south kitakami terrane of northeast japan compared with the surrounding siliciclastic sediments the lumps are rich in phosphate and organic carbon and poor in silicates shape mode of occurrence bone inclusion and geochemical signatures of these lumps confirm that these are coprolites produced not by benthic sediment feeders but most likely by nektonic animals bone inclusion also suggests that carnivorous fish and or marine reptiles constituting the higher part of the food chain produced at least a part of the specimens despite the low diversity of the known fossil vertebrates from the osawa formation coprolites first shed light on the predator prey interactions in the marine ecosystem in south kitakami terrane 5 myr after the end permian mass extinction

alkali metals in the permo triassic as geochemical indicators of surficial processes abstract techniques established as most successful in the examination of widely variable but mainly oxidised geological materials require separation and isolation of components prior to analysis these methods reduce the number of variables involved in the production of clastic debris and enable conclusions to be drawn from a practical reversal of rock manufacture alkali metals prove successful as indicators of the surficial processes operative during permo triassic times they demonstrate enrichment by igneous material during early breccia production and subsequent dilution by wider sedimentation in basins to the east of cornubia england alkalis in recent soils river estuarine and beach sediments of southwest england are concentrated in the fine grained m fraction soils developed over permo triassic bedrock modern river estuarine sediments and beach sands all show anomalous enrichment of trace alkali metals they reflect the abundance of li rb and cs in parent material geochemical analyses of clays from deep boreholes in the wessex and central somerset basins enable inter basin comparisons with the high alkali deposits of devon absolute trace alkali levels are broadly similar to those of correlated beds at outcrop concentrations of cs prove higher in the upper permian than in the triassic of the wessex basin whilst values show devonian old red sandstone sediments to be un enriched in li and cs enrichment of li over rb in triassic mercia mudstones of the south devon coast suggests some li capture from sabkha brines by clays during evaporite production

provenance of the lower cretaceous hayang group gyeongsang basin southeastern korea implications for continental arc volcanism abstract provenance of the lower cretaceous hayang group in the gyeongsang basin korea was investigated using sandstone petrography and the composition of detrital plagioclase and clinopyroxene grains in sandstone and mudrock a magmatic arc tectonic setting is inferred for the source on the basis of sandstone composition detritus derived from granitic gneissic rock and incipient continental arc volcanic rock were mixed in a variable ratio in the hayang sedimentary rocks before deposition of the hayang group the source rock was composed mainly of granitic gneissic rocks this condition persisted in the north the euiseong subbasin during deposition of the lower part of the hayang group in the milyang subbasin the southern part of the gyeongsang basin source area volcanism occurred just before deposition of the hayang group compositions of detrital pyroxene and plagioclase revealed the source volcanic rock to be calc alkaline volcanic arc basaltic andesite to dacite later granitic gneissic rocks as well as volcanic rocks supplied detritus to both subbasins and the source volcanic rocks inferred from plagioclase composition might have been of silicic composition the hayang group was deposited in a transitional setting changing from strike slip movement with little volcanic activity to active subduction related volcanism in the eastern continental margin of asia during this transitional stage the source area was occupied by granitic gneissic rocks and within the source area intermediate to silicic volcanic rocks of dominantly calc alkaline affinity erupted sporadically

geochemical discrimination of clastic sedimentary rock sources abstract factors controlling the geochemistry of a clastic sedimentary rock can include 1 composition of source terrain 2 chemical weathering 3 hydraulic sorting 4 diagenesis 5 metamorphism and 6 hydrothermal alteration a linear solution inferring source terrain composition from geochemistry of the sediment is impossible in this multivariate system as several unknowns will commonly be present the use of graphical analysis of element pairs circumvents the problem chemically immobile elements will maintain invariant ratios during rock mass change caused by either addition or depletion of mobile elements this results in chemically immobile element scattergrams exhibiting linear trends along radians extending from the origin if the major mineral phases of the immobile elements have behaved in a hydrodynamically similar manner as chemically mobile element plots will produce a scatter of points this relationship can be used to test chemical immobility and similarity in hydrodynamic sorting history the constraint on analysis is that the source area must be compositionally uniform or the sediment well mixed prior to delivery to the basin a second technique using sio2 plots has also been developed to investigate element mobility and hydrodynamic behaviour of the mineral phases containing the elements sio2 immobile element plots result in a linear arrangement of points extending towards either 0 or 100 sio2 the 0 intercept position occurs for elements with major mineral phases concentrated in sand the 100 intercept for those concentrated in clays plotting chemically mobile elements produces different patterns and this can be used to gain information on alteration and sorting history elemental ratios for chemically immobile elements with similar hydrodynamic behaviour will be the same as those for the weighted average composition of the source material this provides a powerful tool for deducing source terrain from sediment geochemistry techniques outlined above were tested on archaean metasandstones from superior province canada immobile element ratio diagrams for nb al ti and zr al ti indicate that a calc alkaline extrusive intrusive suite lying to the north of the study area was the source and not five other volcanic suites in the region this conclusion agrees with previous clast lithology studies and accentuates the applicability of the geochemical techniques

mobility of the high field strength rare earth elements and yttrium during late diagenesis authigenic titanite occurs as a secondary pore filling cement in the permian sandstones of the cock of arran scotland the titanite is apparently not associated with in situ alteration of a specific mineral phase or phases suggesting it crystallized from fluids migrating through these porous and permeable sandstones the titanite contains significant concentrations of zr nb p ce nd gd and y implying that these elements were also carried in solution probably in the form of halogen or carbonate complexes associated with hydrothermal circulation related to the intrusion of the adjacent northern granite

ordovician 40ar 39ar phengite ages from the blueschist facies ondor sum subduction accretion complex inner mongolia and implications for the early paleozoic history of continental blocks in china and adjacent areas we obtained 453 21 8 ma and 449 41 8 ma 2 laser step heating 40 ar 39 ar plateau ages for phengite from quartzite mylonites from the blueschist facies ondor sum subduction accretion complex in inner mongolia northern china these ages are within error of the inverse isochron ages calculated using the plateau steps and the weighted mean ages of total fusion of single grains the compositional change from glaucophane in the cores to crossite in the rims of blue amphiboles as revealed by electron microprobe analysis points to decompression probably caused by progressive exhumation of the subducted material the late ordovician ages were not affected by excess argon incorporation because in all likelihood the oceanic sediments were wet on arrival at the trench and free of older detrital mica the ca 450 ma ages are hence interpreted as the time of crystallization during mylonitization under high fluid activity at fairly low temperatures this means that accretion of the quartzite mylonite unit occured about 200 ma before final closure of the paleo asian ocean amalgamation of the siberian tarim and north china cratons and formation of the end permian solonker suture zone we argue that the early paleozoic evolution of the ondor sum complex occurred along the northeastern cimmerian margin of gondwana which was composed of micro continents fringed by subduction accretion complexes and island arcs the later evolution took place during the building of the eurasian continent following middle devonian and younger rifting along the east gondwanan margin and northward drift of the detached north china craton an extensive review shows that this type of two stage scenario probably also applies to the geodynamic evolution of other micro continents like south china tarim a number of kazakh terranes alashan qaidam and kunlun as well as south kitakami and correlatives in japan and probably indochina like the north china craton these were bordered by early paleozoic subduction accretion complexes island arcs or contained calc alkaline volcanic mar gins like for example the central tienshan north qinling north qaidam altun north qilian and kunlun belts in china as well as the oeyama and miyamori ophiolites and matsugadaira motai blueschist belt of japan and the dismembered sergeevka ophiolite of the southern part of the russian far east this implies that a vast orogenic system comprising an archipelago of micro continents seems to have existed along the cimmerian margin of east gondwana in early paleozoic time in which the ultrahigh pressure metamorphism that characterizes the early evolution of many of the asian micro continents occurred introduction and aim

paleomagnetic evidence for the clockwise rotation of southwest japan abstract over 500 oriented samples of felsic rocks of cretaceous to middle miocene age were collected along the go river in the central part of southwest japan in an attempt to detect the process of tectonic rotation of southwest japan from the paleomagnetic view point thermal demagnetization was successful in isolating characteristic directions from the remanent magnetization of samples reliability of the paleomagnetic direction is ascertained through the agreement of directions from different kinds of rocks as well as the presence of both normal and reversed polarities the paleomagnetic results establish that southwest japan began to rotate clockwise through58 14 later than 28 ma and ceased its motion by about 12 ma southwest japan has undergone no detectable north south translation since 28 ma these results imply that southwest japan was rotated about the pivot around 34 n 129 e between 28 ma and 12 ma in association with the opening of the japan sea

late archaean crustal extension sedimentary basin formation flood basalt volcanism and continental rifting the nullagine and mount jope supersequences western australia abstract the mount bruce megasequence set formerly the mount bruce supergroup is a succession of volcanic and sedimentary rocks that was deposited on the pilbara craton of western australia in the late archaean to early proterozoic its history can be described and explained in terms of modern style sequence stratigraphy and of phanerozoic style plate tectonics the megasequence set comprises the chichester range megasequence that was deposited on a rifted to divergent continental margin and the overlying hamersley range megasequence that was deposited on a convergent continental margin the chichester range megasequence comprises in order of superposition the nullagine and mount jope supersequences and the marra mamba supersequence package the nullagine and mount jope supersequences are each the rock record of one phase of a protracted two phase late archaean 2770 2700 ma continental break up the nullagine supersequence consists of the mount roe sequence which comprises mostly subaerial basalt and the overlying hardey sequence package which comprises mostly terrigenous sedimentary rocks that were deposited in extensional sedimentary basins the mount jope supersequence consists of in order of superposition the kylena sequence which comprises mostly basalt the tumbiana sequence which comprises mostly tuff and tuffaceous rocks and the maddina sequence package which comprises mostly basalt the nullagine supersequence was deposited during an episode of wnw ese directed crustal extension that possibly led to the development of a rift to the west of the present pilbara craton the mount jope supersequence was deposited during the subsequent development of a wnw ese trending rift the position of which approximates the present southern craton margin regional scale uplift was associated with the development of both supersequences particularly with the nullagine supersequence basement strike slip faults were reactivated as dip slip structures during crustal extension and controlled the locations of some hardey sequence package extensional sedimentary basins nullagine supersequence and mount jope supersequence rifting led to a divergent continental margin bordering an ocean along the south and probably the far west of the craton post rift thermal subsidence was accompanied by the accumulation of mudrock carbonate sedimentary rock and iron formation of the marra mamba supersequence package in a shelf setting the implications of these interpretations are that at 2800 ma the pilbara craton was significantly larger than at present and that it had a sufficiently thick subcontinental lithosphere that divided it in a manner analogous to the break up of phanerozoic continents the nullagine and mount jope supersequences contain three stacked flood basalt successions which were erupted over a time period of between of 55 and 80 m y stacked flood basalt successions covering such a long time period are not known in the phanerozoic and are tangible evidence of a hotter late archaean mantle

comparison between outcrop spectral gamma ray logging and whole rock geochemistry implications for quantitative reservoir characterisation in continental sequences abstract a high resolution spectral gamma ray sgr log is compared to elemental whole rock geochemical data in a reservoir scale outcrop analogue the otter sandstone formation sherwood sandstone group east devon sgr data compare closely to those generated for point samples by inductively coupled plasma icp techniques with disparities attributable to the different sample volumes icp data reveal separate mineralogical sources for radio elements which enable three lithotypes to be discriminated using th u ratio and k 2 o data once established the discriminants are applied to the sgr log enabling three lithotypes to be dicriminated these conclusions suggests that sgr logs have significant potential for real time lithotype prediction in continental sequences which in turn enable predictions of reservoir quality and increase confidence in the interpretation of sedimentary architecture

stratigraphic control on laterally persistent cementation book cliffs utah field data from the upper cretaceous blackhawk formation in the book clitfs utah colorado demonstrate the presence of laterally extensive carbonate cements beneath major marine flooding surfaces the occurrence of firmgrounds compaction around concretions and high minus cement porosities indicate that cementation occurred during early diagenesis it is proposed that the early cementation associated with these marine flooding surfaces occurred as a result of reduced sediment accumulation rates or non depositional hiatuses linked to abrupt deepening during marine flooding these reduced sediment accumulation rates extended sediment residence time within early diagenetic zones leading to enhanced early cementation in shallow marine sandstones and mudstones