eddy resolving observation of the north pacific subtropical mode water abstracthydrographic data obtained by high resolution shipboard observations and argo profiling floats have been analyzed to study the mesoscale structure and circulation of the north pacific subtropical mode water stmw the float data show that in the late winter of 2008 stmw having a temperature of approximately 18 8 17 7 and 16 6 c formed west of 140 e at 140 150 e and east of 150 e respectively in the recirculation gyre south of the kuroshio extension after spring the newly formed stmw gradually shift southward decreasing in thickness simultaneously the stmws of 16 6 and 17 7 c are gradually stirred and then mixed in terms of properties in late fall they seem to be integrated to form a single group of stmws having a temperature centered at 17 2 c such stmw circulation in 2008 is much more turbulent than that in 2006 which was investigated in a previous study the difference between the two years is attributed to the more variable state of the kuroshio extension in 2008 associate

decadal variability in the kuroshio oyashio extension simulated in an eddy resolving ogcm abstract through analysis of a hindcast integration of an eddy resolving quasi global ocean general circulation model decadal variability in the kuroshio oyashio extension region is investigated with particular emphasis on that of the subarctic oyashio and the kuroshio extension ke fronts the ke front is deep and is accompanied by a sharp sea surface height ssh gradient with modest sea surface temperature sst gradient in contrast the subarctic front is shallow and is recognized as a zone of tight gradient in sst but not ssh as a decadal scale change from a warm period around 1970 to a cool period in the mid 1980s those fronts in the model migrate southward as observed and the associated pronounced cooling is confined mainly to those frontal zones reflecting the distinctive vertical structure of the fronts the mixed layer cooling is the strongest along the subarctic front whereas the subsurface cooling and the associated salinity changes are most pronounced along the ke front concomitan

chronology of late wisconsinan glaciation in middle north america abstract we propose a chronology of late wisconsinan glacial fluctuations in middle north america from alberta to wisconsin based on radiocarbon dates derived solely from wood previous chronologies of the southwestern margin of the north american continental ice sheet have depended to a considerable degree on radiocarbon dates from fine grained organic sediment this material is commonly contaminated with older carbon resulting in chronologic confusion by using only dates from wood much of the confusion disappears however because of the scarcity of wood dates only four of the sixteen identified fluctuations are accurately dated an advance into iowa about 14 000 to 13 500 bp an advance into south dakota and iowa about 12 300 bp an advance into the lake michigan basin about 11 700 bp and an advance into the lake superior basin about 9900 bp in addition the beginning of late wisconsinan glaciation before 20 000 bp is fairly well documented none of the fluctuations in the western part of the region are accurately dated

alkyldibenzofurans in terrestrial rocks influence of organic facies and maturation abstract dibenzofuran dbf dibenzothiophene dbt and phenanthrene phe have been determined along with their methyl derivatives mdbfs mdbts mps in coals carbonaceous shales and mudstones of lower cretaceous to upper carboniferous ages from the elmworth gas field canada and from the sakoa madagascar and ruhr coal germany basins the samples contained mainly terrestrial organic matter with thermal maturities in the 0 7 1 9 mean vitrinite reflectance rr range the pronounced predominance of mdbfs over mdbts in the sakoa samples is typical of plant debris deposited in lacustrine swamp environments onset of intense mdbf generation occurs at fairly low rank 0 77 rr as indicated by elevated concentrations of 50 120 g mdbfs g total organic carbon toc influences of lithology organic matter type and maturity on distributions of the target compounds were extracted from the molecular concentration data by multivariate statistical methods such as principal components analysis pca and fuzzy c means cluster analysis with nonlinear mapping nlm a specific source effect on 1 mdbt concentrations suggests that lichens contributed to the senescent coal forming forest in the sakoa coal basin alkyldibenzofurans hence are potential lichen biomarkers mdbfs can be used as maturity indicators only beyond 1 0 rr where ruhr coals displayed a distinct increase in the 1 4 mdbf ratio

southern laurentide ice lobes were created by ice streams des moines lobe in minnesota usa abstract regional mapping in southern minnesota has illuminated a suite of landforms developed by the des moines lobe that delimit the position of the lobe at its maximum and at lesser readvances the ice lobe repeatedly advanced discharged its subglacial water and subsequently stagnated recent glaciological research on antarctic ice streams has led some glacial geologists to postulate that ice streams drained parts of the marine based areas of the laurentide ice sheet i postulate that such ice streams may develop in land based areas of an ice sheet as well and that the des moines lobe 200 km wide and 900 km long was an outlet glacier of an ice stream it appears to have been able to advance beyond the laurentide ice sheet as long as adequate water pressure was maintained however the outer part of the lobe stagnated because subglacial water that facilitated the flow was able to drain away through tunnel valleys stagnation of the lobe is not equivalent to stoppage of the ice stream because ice repeatedly advanced into and onto the stagnant margins stacking ice and debris similar landforms are also seen in other lobes of the upper midwestern united states

currents associated with the quasi stationary jet separated from the kuroshio extension abstractthe hydrographic structure of a quasi stationary jet separated from the kuroshio extension a phenomenon that possibly leads to deepening of the winter mixed layer is revealed via intensive observations using a conductivity temperature depth profiler and a ship mounted acoustic doppler current profiler adcp carried out in september 2009 data collected from profiling floats set to drift isopycnal layers and time series of sea surface buoys and satellite altimeters were also analyzed to understand the continuity water characteristics and time variation of the jet although the flow field was complex due to disturbances such as energetic eddies the jet transported subtropical water to the downstream northeastern observation region in a layer shallower than 400 dbar and its highest velocity was concentrated in the mid and deep layers 0 30 m s 1 at the sea surface and 0 05 m s 1 at 800 m depth the velocity axes of the jet detected from the satellite data corresponded to those detected th

changes in bulk properties and molecular compositions within new zealand coal band solvent extracts from early diagenetic to catagenetic maturity levels abstract the bulk properties and bitumen molecular compositions of a rank series of 38 humic coals from the new zealand coal band cretaceous cenozoic have been analysed to investigate early maturation processes affecting coaly organic matter through diagenesis to moderate catagenesis rank s r 0 0 11 8 r o 0 23 0 81 the samples comprise a relatively restricted range of vitrinite rich coal types formed largely from higher land plant material under relatively oxic conditions but with a significant contribution from microbial biomass with increasing rank total organic carbon contents show a general increase whereas moisture and asphaltene contents decrease bitumen yields also decrease through the stages of diagenesis and early catagenesis rank s r r o r 5 6 r o 0 40 as indicated by the constant occurrence and gradual increase of isoprenoids e g pristane and phytane and hopanoids in their more mature configuration this early phase of catagenesis not previously recognised in new zealand coals is followed at rank s r 9 r o 0 55 by the main catagenesis phase characterised by a more rapid increase in the generation of hydrocarbons including total n alkanes isoprenoids and hopanes changes in the maturity of new zealand coals can be traced by the carbon preference index and several hopane maturity parameters including 22 s 22 s 22 r and

origin of the northern atlantic s heinrich events as first noted by heinrich 1988 glacial age sediments in the eastern part of the northern atlantic contain layers with unusually high ratios of ice rafted lithic fragments to foraminifera shells he estimated that these layers are spaced at intervals of roughly 10 000 years in this paper we present detailed information documenting the existence of the upper five of these layers in odp core 609 from 50 n and 24 w their ages are respectively 15 000 radiocarbon years 20 000 radiocarbon years 27 000 radiocarbon years about 40 000 years and about 50 000 years we also note that the high lithic fragment to foram ratio is the result of a near absence of shells in these layers although we are not of one mind regarding the origin of these layers we lean toward an explanation that the heinrich layers are debris released during the melting of massive influxes of icebergs into the northern atlantic these sudden inputs may be the result of surges along the eastern margin of the laurentide ice sheet

generation of gas and oil from coal and other terrestrial organic matter abstract late carboniferous permian sedimentary rocks contain the world s largest coal reserves which have generated and released gas but little if any oil in comparison organic matter deposited in lacustrine fluvial deltaic or brackish water sediments has sourced large quantities of waxy oils in countries such as china australia the u s a argentina venezuela and indonesia plus gas and condensate in deltas worldwide why is more oil coming from land derived organic matter disseminated in sediments than from the carboniferous permian coal beds which also are land deposits the answer appears to be in the hydrogen content and the ease of migration when organic matter and coals have high hydrogen contents relative to carbon they can form oil when the hydrogen is low mainly gas is formed most of the world s coal is low in hydrogen whereas much of the terrestrial organic matter disseminated in sediments is higher in hydrogen so it forms more oil also both gas and oil are adsorbed on coal more strongly than on the disseminated kerogen of sedimentary rocks this makes migration of oil out of the coal more difficult compared to migration from conventional shale source rocks

paleo pressure evolution and its origin in the pinghu slope belt of the xihu depression east china sea basin abstract the xihu depression in the east china sea basin is one of the prime gas and light oil producing regions of eastern china overpressure evolution and origin in the sandstone reservoirs of the pinghu e2p formation in the pinghu slope belt of the xihu depression were investigated through a combination of fluid inclusion analyses and basin numerical modeling combined with measured pore pressures drill stem and wireline formation tests well loggings gas geochemistry and casting thin section data four oil inclusion types exhibiting different api gravities and hydrocarbon gas inclusions were identified using inclusion petrography microscopic fluorescence and raman spectra homogenization and ice melting temperatures of coeval aqueous inclusions determined using microthermometry combined with burial thermal histories determined by basin numerical modeling suggested multiple episodes of oil and natural gas charge in the e2p reservoirs from the miocene to the present day pore pressure evolution history reconstructed with fluid inclusion pvtx analysis indicated that the pinghu formation experienced three phases overpressure generation followed by overpressure release and then further overpressure generation the first phase of weak overpressure was generated during burial in the middle late miocene currently it is hard to definitely determine the origin of the first phase of overpressuring nevertheless it can be speculated that the origin may be related to disequilibrium compaction oil generation and tectonic compression based on burial tectonic and hydrocarbon generation histories following this a sudden uplift of formations led to overpressure release in the late miocene and then the second phase of moderate overpressure generation occurred during burial in the late pliocene and quaternary based on well log signatures vitrinite reflectance data of mudstones and gas geochemistry combining with seismic analysis the second phase of overpressuring was interpreted to have been mainly caused by fluid expansion which resulted from local gas generation by kerogen maturation and long distance vertical and lateral pressure transfer

organic geochemistry and kinetics for natural gas generation from mudstone and coal in the xihu sag east china sea shelf basin china abstract a comparative study on organic geochemistry and kinetics was performed on two representative coal measure mudstone and coal samples of the eocene pinghu formation in the xihu sag east china sea shelf basin china gas chromatography mass spectrometry analysis of the aliphatic fractions of the source rock extracts was performed to characterize the maturity depositional conditions and source materials in the samples the kerogens isolated from the mudstone and coal were pyrolyzed in a closed system at two heating rates to determine the kinetics for natural gas generation and the results were extrapolated to geological conditions biomarker assemblages show that the mudstone type iii kerogen and coal type ii iii kerogen contain predominantly terrigenous source materials with the effect of microbial reworking and were deposited under oxic conditions within an unstratified water column the mudstone has slightly more algal material input and less oxic conditions during deposition than the coal the rocks are at the early mature stage but the coal is slightly more mature than the mudstone the activation energies for natural gas generation from the mudstone and coal distribute mainly in the range of 47 62 kcal mol and 50 69 kcal mol with a frequency factor of 2 0 1011 s 1 and 1 0 1013 s 1 respectively the lower activation energies for the mudstone than the coal suggests an earlier onset of natural generation assuming a constant burial heating rate of 3 c ma for the calculated activation energy distributions the calculated temperature for a given transformation ratio can differ by 60 c indicating varying kinetic stability due to different kerogen composition and structure this significant and unexpected difference suggests that more attentions should be paid to the kinetic heterogeneity of coal bearing source rocks and we must be particularly cautious about selecting appropriate kinetic models in petroleum system modeling

origin and consequences of cyclic ice rafting in the northeast atlantic ocean during the past 130 000 years deep sea sediment cores recovered from the northeast atlantic ocean were examined in order to elucidate the influence of the earth s orbital parameters on major ice rafting analyses of coarse grained ice rafted debris and planktonic foraminifers revealed a strong reaction to the precession signal since 130 000 yr b p dropstone layers have been deposited each half period of a precessional cycle 11 000 1000 yr ice rafting occurs during times of winter minimum summer maximum insolation and summer minimum winter maximum insolation in the first case high summer insolation forces meltwater discharge from the ice sheets into the polar seas which subsequently enhances formation of sea ice during the winter in the second case growth of continental ice enhances iceberg production which also leads to a salinity reduction of surface seawater both situations result in a southward penetration of polar water thus the marine record of dropstones documents ice rafting not only during weichselian stades but also during cold events within interstades the regularity of ice rafting yields a useful framework to calibrate and elucidate climatic changes not only in the region of the north atlantic ocean but also in remote areas such as the pacific ocean and the antarctic

characteristics of type iii kerogen in coal bearing strata from the pennsylvanian upper carboniferous in the ruhr basin western germany comparison of coals dispersed organic matter kerogen concentrates and coal mineral mixtures abstract quality quantity and maturity of coal and dispersed terrigenous organic matter were studied on six coal bearing intervals in duckmantian strata pennsylvanian upper carboniferous of the ruhr basin western germany between 10 and 40 samples were collected from fresh drill cores of each interval typically consisting of a coal seam as well as clastic roof and floor strata sandstone siltstone claystone coal seams constitute about 8 vol of the succession studied the samples were analysed by organic petrological methods and rock eval pyrolysis maturity expressed in terms of vitrinite reflectance is between 0 75 and 1 0 for the six successions studied the total amount of dispersed organic matter in clastic rocks is about half of that stored in coal seams both containing predominantly vitrinite significant differences between rock eval parameters determined on whole rock samples and kerogen concentrates were observed especially with respect to hydrogen index hi values thus the hi of the coal is about twice as high as that of the dispersed organic matter although the maceral composition is similar the effects of minerals were further examined by rock eval pyrolysis of artificial mixtures of coal lignite powder and different minerals reduced hi values are partly explained by the retention of generated hydrocarbons on mineral surfaces and partly by reactions of generated fluids with pyrite in kerogen concentrates

locally enhanced wintertime air sea interaction and deep oceanic mixed layer formation associated with the subarctic front in the north pacific 1 satellite derived high resolution air sea flux data and argo float data were analyzed to reveal the fine scale spatial structures of air sea turbulent heat and momentum fluxes and their relationship with the deep oceanic mixed layer around the subarctic front saf in the north pacific an important feature inferred from the satellite derived dataset is the presence of a pair of positive and negative air sea flux anomaly bands with a width of 100 200 km on both sides of the saf such a fine scale structure in air sea fluxes has not been captured in previous datasets the saf plays a significant role in determining the fine scale structure of air sea fluxes the oceanic mixed layer is deeper to the south of the saf and the maximum mixed layer depth is observed near the positive anomaly band in air sea fluxes this study concludes that active air sea interactions due to the presence of the saf enhances upward air sea heat and momentum fluxes to the south of saf and selectively produces a deep oceanic mixed layer where the formation of transition region mode water occurs

the oleananes origin maturation and limits of occurence in southern nigeria sedimentary basins oleananes occur within well defined age and paleogeographic boundaries in the sedimentary province of southern nigeria thus signifying that the biomarkers may be analogous to index fossils in anambra syncline lower benue trough the biomarkers are found in rocks which are as old as late upper cretaceous in tertiary niger delta the concentration composition and distribution of the oleananes in rocks and oils are determined mainly by palaeodepositional environment and thermal history and are independent of age and geographical location of specific samples oleanane content varies with increasing burial depth with peak concentration coinciding within rm range 0 4 0 6 implying early generation of hydrocarbons from the basin s typically resin rich kerogens it is evident that the oleanane content parameter is superior to the hopane and sterane isomerisation indices for monitoring thermal maturation in the delta and for differentiating paralic from paralic marine source facies as well as early from late generated oils

quasi stationary jets transporting surface warm waters across the transition zone between the subtropical and the subarctic gyres in the north pacific 1 surface flow jets and associated sea surface temperature sst distribution are investigated in the northwestern north pacific using satellite derived surface currents and sst data that can resolve fine spatial scale structure the combined use of these data reveals warm tongue phenomena driven by surface geostrophic jets which extend northeastward in the kuroshio oyashio transition area they roughly coincide with the subarctic front saf defined as the 4 c isotherm at 100 m depth the phenomena appear throughout the year with seasonal cycles which do not correspond with that of the subarctic north pacific their positions are affected by bottom topography so that their quasi stationary and consistent features are suggested thus it is implied that these jets play an important role in transporting warm waters toward the subarctic region the time series of sst and current fields describe the jets year to year variability involving some changes in strength and connections with the kuroshio extension ke and demonstrate the effects of advection by the jets on sst fields when ke extends northward at its crests for 1999 2002 one of the jets along saf simultaneously strengthens resulting in high sst region directly over and along the south side of the jet hydrographic data show warm saline water intrusions along the jets their mean fields also reveal that these jets are vertically well developed forming a boundary between the subtropical and subarctic gyres in the north pacific

biological origin of tetracyclic diterpanes n alkanes and other biomarkers found in lower carboniferous gondwana coals niger abstract the saturated hydrocarbons of coal samples of the anou araren mine tim mersoi basin niger republic have been studied by gc and gc ms chromatograms revealed rather unusual n alkane distributions dominated by compounds in the c 20 c 23 range and showing a rapid and irregular decrease towards higher molecular weights these signatures appear to be typical of the paleozoic gondwana swamps flora unlike typical low maturity terrestrial organic matter characterized by a dominance of odd carbon number n alkanes in the c 27 c 33 range which could be attributed to angiosperms the presence of large amounts of polycyclic diterpanes ent beyerane phyllocladanes and kauranes is unexpected in samples of that age since these compounds are usually thought to be derived from conifers which supposedly had not yet evolved at the time a more likely explanation is that these diterpanes could be derived from biological precursors of the conifers

the north pacific climatology of winter mixed layer and mode waters abstract a climatology of the winter mixed layer in the north pacific ocean was constructed using hydrographic data from historical archives and recent observational programs including the world ocean circulation experiment the main aim was to provide better knowledge about source areas of upper water masses the authors have endeavored to preserve water properties near the frontal regions by keeping the smoothing scale as small as possible the resulting climatology shows considerable differences in the mixed layer depth and its water properties from those derived from the world ocean atlas woa maps of the potential vorticity field of the north pacific pycnocline are presented using the isopycnally averaged climatology hydrobase three distinct lateral minima of potential vorticity are identified as subtropical mode water stmw central mode water cmw and eastern subtropical mode water estmw in the western central and eastern parts of the subtropical gyre respectively the hydrobase isopy

the morphology of ice streams a b and c west antarctica and their environs airborne radar soundings of the ice sheet surface made in 1984 1985 together with elevations measured by oversnow traverses between 1957 and 1964 have been used to produce a surface elevation map of ice streams a b and c and much of the region around them the flight positions and elevations were tied to many ground control stations whose positions in three dimensions were fixed by satellite tracking ice thicknesses were also measured along the flight lines but have not yet been mapped the surfaces of active ice streams a and b exhibit a longitudinal ridgetrough topography of uncertain origin prominent surface valleys are associated with most but not all of their marginal shear zones there is a deep subglacial trough beneath the grid northeastern side of ice stream a that connects to the subglacial trough beneath reedy glacier the boundary between ice streams bl and b2 the two tributaries of ice stream b persists as a suture zone for 250 km downstream from their merger ice stream bl overlies a relatively deep subglacial trough that continued under the corresponding part of ice stream b until it disappears close to the grounding line between ice streams bl and b2 there is a complex zone containing several regions of undisturbed ice separated by bands of disturbed ice which suggest to us that rafts of ice are being incorporated into the ice streams the previously reported negative mass balance for the drainage system of ice stream b may arise from the expansion of the ice stream into the interior of the west antarctic ice sheet crevasse bands at some places on ridge ab together with high glacial velocities reported elsewhere also suggest this expansion close to the ross ice shelf ice stream b widens into a nearly flat area where the mean surface slope is only 3 5 10 4 and the surface elevations are only a few tens of meters above hydrostatic equilibrium inactive ice stream c differs from active ice streams a and b in surficial and basal characteristics no elongated ridges and troughs are observed instead the ice stream surface exhibits several terraces including some maxima and minima in elevation radar sounding reveals areas where basal echoes are strong and steady indicating subglacial water alternating with areas of weaker echoes with short fading lengths calculations indicate that the strong reflections require a water layer at least several centimeters to several meters thick depending on the electrical conductivity of the water due to reversals in the surface slope the hydrologic potential gradient changes sign several times along ice stream c which implies that subglacial water should collect in some locations

trace and rare earth element ree characteristics of mudstones from eocene pinghu formation and oligocene huagang formation in xihu sag east china sea basin implications for provenance depositional conditions and paleoclimate abstract the interpretation of depositional conditions provenance and paleoclimate provide important information to understand hydrocarbon source rock formation and distribution the concentrations of trace elements and rare earth elements rees of fifty mudstone samples from eocene pinghu formation and oligocene huagang formation in xihu sag east china sea basin were determined by inductively coupled plasma mass spectrometry icp ms to test the depositional conditions provenance and paleoclimate evidences from the visual comparisons of the simple bivariate plots diagrams and statistical comparisons of the mann whitney rank sum test suggest that there may be a common source for the pinghu formation and huagang formation mudstones sedimentary provenance from bivariate plots diagrams of hf versus la th and la sc versus co th shows that pinghu formation mudstones are mainly composed of mixed felsic basic source and acidic source whereas huagang formation is mainly acidic source additionally the ree vs la yb discrimination diagram shows that the property of the provenance for the pinghu formation mudstones consists sedimentary rock alkaline basalt and a small amount of continent tholeiitic basalts whereas that of the huagang formation is mainly alkaline basalt and sedimentary rock discriminant diagrams consisting of la th sc and th co zr 10 suggest that the mudstones of two formations were deposited in continental island arc and active continental margin tectonic setting redox proxies v ni v v ni and ce indicate that most of the mudstones of two formations were deposited in a relatively dysoxic anoxic condition the cool and humid climate represented by sr cu and rb sr ratios were prevailing in xihu sag during the eocene and oligocene period and the oligocene was cooler than eocene moreover five long term base level cycles siii1 siii5 and four sequence boundaries sb2 sb5 were recognized in the pinghu formation and huagang formation based on the previous research we find that the abnormal surfaces of geochemical parameters such as v ni sr ba u ti v ti ti and ree to some extent agree with sequence boundaries sb2 sb3 sb4 and sb5 in mudstones additionally the increment of ti and ree concentrations and the decrease of sr ba v ni u ti and v ti ratios above the sb4 indicates that terrigenous clast grew significantly and the sea level dropped after late eocene which is related with the late eocene tectonic movement

role of the gulf stream and kuroshio oyashio systems in large scale atmosphere ocean interaction a review abstract ocean atmosphere interaction over the northern hemisphere western boundary current wbc regions i e the gulf stream kuroshio oyashio and their extensions is reviewed with an emphasis on their role in basin scale climate variability sst anomalies exhibit considerable variance on interannual to decadal time scales in these regions low frequency sst variability is primarily driven by basin scale wind stress curl variability via the oceanic rossby wave adjustment of the gyre scale circulation that modulates the latitude and strength of the wbc related oceanic fronts rectification of the variability by mesoscale eddies reemergence of the anomalies from the preceding winter and tropical remote forcing also play important roles in driving and maintaining the low frequency variability in these regions in the gulf stream region interaction with the deep western boundary current also likely influences the low frequency variability surface heat fluxes damp the low frequency sst anomalies ove

cyclic terpenoids of contemporary resinous plant detritus and of fossil woods ambers and coals abstract cyclic terpenoids present in the solvent extractable material of fossil woods ambers and brown coals have been analyzed the sample series chosen consisted of wood remains preserved in holocene to jurassic sediments and a set of of ambers from the philippines copalite israel canada and dominican republic the brown coals selected were from the fortuna garsdorf mine and miocene formations on fiji the fossil wood extracts contained dominant diterpenoid or sesquiterpenoid skeletons and aromatized species were present at high concentrations with a major amount of two ring aromatic compounds tricyclic diterpenoids were the predominant compounds in the ambers aromatized derivatives were the major components consisting of one or two aromatic ring species with the abietane and occasionally pimarane skeletons the saturated structures were comprised primarily of the abietane and pimarane skeletons having from three to five carbon c1 c2 etc substituents kaurane and phyllocladane isomers were present in only minor amounts bicyclic sesquiterpenoids as saturated and partial or fully aromatized forms were also common in these samples but only traces of sesterterpenoids and triterpenoid derivatives were found the brown coal extracts were composed of major amounts of one and two ring aromatized terpenoids with a greater proportion of triterpenoid derivatives than in the case of the woods and ambers this was especially noticeable for the german coal where the triterpenoids were predominant open c ring aromatized structures were also present in this coal steroid compounds were not detectable but some hopanes were found as minor components in the german brown coal an overview of the skeletal structure classes identified in each sample as well as the general mass spectrometric characteristics of the unknown compounds are included in the present paper it can be concluded from these structural distributions that aromatization is the main process for the transformation of terrestrial cyclic terpenoids during diagenesis constituting a general pathway for all terpenoids

cenozoic sill intrusion in the central and southern east china sea shelf basin abstract cenozoic igneous rocks dominated by basalts are exposed sporadically onshore east china and they provide important information about the cenozoic evolution of the region importantly their geometries and distribution are still not well constrained in the 200 600 km wide offshore continental shelf region based on seismic profiles this study presents the geometric characteristics of 133 igneous sills that are widely distributed in the central and southern regions of the east china sea shelf basin ecssb sills in high amplitude continuous seismic reflections mostly occur in a time interval of 1 1 3 3 s in multiple seismic profiles corresponding to a depth range of 1 1 4 8 km they can be classified into five types saucer shaped sills strata concordant sills laccoliths inclined sheets and hybrid sills of these the saucer shaped sills predominate strata deformation associated with these igneous sills indicate that sill intrusion has become intense since the miocene and it potentially affected petroleum systems in the ecssb forced folds induced by the sills are prospective petroleum traps we infer that sill intrusion in the ecssb was due to magma upwelling caused by dehydration and or small scale convection in a large mantle wedge above the stagnant pacific slab the subduction of the philippine sea plate resulted in tectonic inversion in the ecssb and extension in the okinawa trough since the early miocene triggered more magmatism in the tectonically thinned ecssb thick sedimentary strata over a thin crust in the ecssb may have induced more intrusive than extrusive cenozoic magmatism

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

till beneath ice stream b 3 till deformation evidence and implications most of the velocity of ice stream b near the upstream b camp upb west antarctica appears to arise from deformation of a seismically detected subglacial till layer that averages 6 m thick available evidence indicates that the entire thickness of this till layer is deforming and is eroding subjacent bedrock into flutes parallel to ice flow and hundreds of meters across the resulting till flux beneath upb is equivalent to an average erosion rate of about 0 4 mm yr 1 in the catchment area and suggests that till deltas tens of kilometers long have been deposited at the grounding line during the holocene such deltas should be characterized by partial ice till decoupling across a water film and by a small ice air surface slope they may have been discovered by recent geophysical work

effect of burial history on diagenetic and reservoir forming process of the oligocene sandstone in xihu sag east china sea basin abstract porosity evolution history hydrocarbon charging periods diagenetic and reservoir forming characteristics of low permeability and tight sandstone are presented in this study the interpretation is based on information including thin section scanning electron microscope homogenization temperature of fluid inclusion bulk rock x ray diffraction analysis clay x ray diffraction analysis and stable isotopic composition these sandstones are located in the oligocene e3h formation in the xihu sag east china sea basin east china five diagenetic events in the h3 h4 and h5 members were determined including connate alkaline pore water of the oligocene sandstone meteoric water leaching in late miocene organic acids and co2 acidic fluids in early middle miocene reservoir temperature decrease induced by tectonic uplift and alkaline diagenetic environment from late miocene to present day porosity evolution history of different grain size lithology were evaluated by basin modelling and test data the medium sandstone and coarse sandstone of the h3 member and medium sandstone of the h4 member not reached the tight state in the geologic time the fine sandstone of the h4 member entered the tight state at 12 ma suffered acidic fluids to improve the tight state in late stage and entered the tight state again since 6 5 ma the medium sandstone fine sandstone and siltstone in the h5 member entered the tight state at 13 5ma 16ma and 19ma respectively three hydrocarbon charging periods were determined including 15 5 ma 10 4 ma in the middle miocene 9 6 ma 7 0 ma in the late miocene and 6 2 ma 0 0 ma from the late miocene to present day three diagenetic and reservoir forming patterns were proposed including accumulation without tightness accumulation after tightness improving reservoir quality with acidic fluid accumulation while tightness accumulation after tightness the burial history cannot be ignored in the diagenetic events porosity evolution history and hydrocarbon charging periods of similar low permeability and tight sandstone in sedimentary basins

geochemical characteristics of carboniferous coaly source rocks and natural gases in the southeastern junggar basin nw china implications for new hydrocarbon explorations abstract the upper carboniferous coaly source rocks are verified to be developed in the southeastern junggar basin which is lithologically composed of carbonaceous mudstones and mudstones according to the geochemical total organic carbon rock eval and biomarker fingerprints and organic petrology analyses the carboniferous source rocks are primarily gas prone characterized by kerogen type iii and were deposited in an oxidized sub oxidized brackish environment significantly contributed by terrigenous higher plants carbonaceous mudstones are generally more oil prone in comparison with the mudstones the measured vitrinite reflectance t max and sterane isomers indicate that the source rocks are at immature early gas generation stage and have not entered the peak gas generation stage natural gases are coal type gases derived from the carboniferous source rock the maturities of them are highly inconsistent with those of source rock samples based on 2 d basin modeling natural gases were generated from the highly mature coaly source rocks in the fukang depression and migrated upward to the uplift via the p c regional inconformity

higher plant biomarkers reflect palaeovegetation changes during jurassic times abstract the relative abundances of three higher plant derived biomarkers retene cadalene and ip ihmn have been measured in marine sedimentary rocks from the northwest margin of australia it is thought that each biomarker represents input from a different plant type the distributions of these three compounds form a fingerprint representing higher plant input hpf variations in hpf in oxfordian sediments were nearly identical in all three locations with retene becoming very abundant relative to the other two compounds with decreasing age of the sediment this finding strongly suggests that the composition of terrestrial input during deposition largely determines hpf and that the possible effects of diagenesis and catagenesis on the distribution of the three biomarkers are relatively unimportant the marked increase in the abundance of retene relative to that of cadalene during the oxfordian is interpreted to reflect an increase in the contribution of plants that produced precursors for retene i e conifers brought about by a significant change in climate this was exemplified by measuring the distributions of retene and cadalene expressed in the higher plant parameter hpp for a suite of sediments from the carnarvon basin western australia covering the complete jurassic period the hpp profile displays three major cycles each covering a period of at least 10 million years this profile not only compared well with published palaeoclimate data but also showed a remarkable similarity with second order cycles in the global sea level curve thus strongly supporting the proposal that variations in hpf and hpp are indications of changes in palaeoclimate the relation with global sea level further suggests that global factors e g the atmospheric carbon dioxide concentration may play a major role in determining the observed variations in the distributions of these higher plant derived biomarkers

geochemical characteristics of tertiary coal bearing source rocks in xihu depression east china sea basin abstract this study aims at investigating hydrocarbon generation potential and biological organic source for the tertiary coal bearing source rocks of pinghu formation middle upper eocene in xihu depression east china sea shelf basin another goal is to differentiate coal and mudstone with respect to their geochemical properties the coal bearing sequence has a variable organofacies and is mainly gas prone the coals and carbonaceous mudstones in comparison with mudstones have a higher liquid hydrocarbon generation potential as reflected by evidently higher hi values averaging 286 mg hc g c and h c atomic ratios round 0 9 the molecular composition in the coal bearing sequence is commonly characterized by unusually abundant diterpenoid alkanes dominant c29 sterane over c27 and c28 homologues and high amount of terrigenous related aromatic biomarkers such as retene cadalene and 1 7 dimethylphenanthrene indicating a predominantly terrigenous organic source the source rocks show high pr ph ratios ranging mostly from 3 5 to 8 5 and low mdbts mdbfs ratios

ocean frontal effects on the vertical development of clouds over the western north pacific in situ and satellite observations abstract a suite of shipboard and satellite observations are analyzed and synthesized to investigate the three dimensional structure of clouds and influences from sea surface temperature fronts over the western north pacific sharp transitions are observed across the kuroshio extension ke front in the marine atmospheric boundary layer mabl and its clouds the ocean s influence appears to extend beyond the mabl with higher cloud tops in altitude along the ke front than the surroundings in winter intense turbulent heat release from the ocean takes place on the southern flank of the ke front where the cloud top penetrates above the mabl and reaches the midtroposphere in this band of high cloud tops frequent lightning activity is observed the results of this study suggest a sea level pressure mechanism for which the temperature gradient in the mabl induces strong surface wind convergence on the southern flank of the ke front deepening the clouds there in early summer sea fog frequently occurs on

vegetation differences and diagenetic changes between two bulgarian lignite deposits insights from coal petrology and biomarker composition abstract during the miocene numerous sedimentary basins formed on the territory of bulgaria as a result of the extensional tectonic settings related to the post orogenic development of the late alpine orogen in this study we review the petrographic composition and biomarker assemblage of two adjacent basins in western bulgaria i e beli breg and staniantsi basins both contain lignite formed during late miocene c 6 ma despite similar tectonic settings and depositional environments the lignite seams possess different petrographic and organic geochemical characteristics reflecting differences in the peat forming palaeo communities and facies variations the peat forming vegetation in beli breg basin was dominated by decay resistant coniferous plants as indicated by abundant fossil wood remains very good tissue preservation and a biomarker assemblage dominated by diterpenoids in contrast staniantsi lignite is poor in fossil wood and contains a significant amount of triterpenoid biomarkers suggesting the predominance of angiosperm plants in the swamp the results of the biomarker analyses are consistent with palaeobotanical and palynological data from the literature the lignite seams in both basins formed under frequently changing eh conditions as indicated by the severe degradation of the non gymnosperm tissues the low gelification index values and the variations in pristane phytane ratio probably as a result of seasonal drying of the swamps and changes of the ground water table hopanoid contents in beli breg lignite are very low and are consistent with the abundance of decay resistant vegetation in contrast bacterial activity was obviously higher in the staniantsi swamp however resulting only in slightly enhanced gelification of plant tissues the geochemical data suggest that the diagenetic changes of the organic matter were mainly governed by thermal degradation rather than bacterial activity

source rock potential of the lowest coal seams of the marcelina formation at the paso diablo mine in the venezuelan guasare basin evidence for the correlation of amana oils with these paleocene coals abstract the aims of this work were to carry out a combined petrographic palynofacies and organic geochemical study of twelve drill core samples collected from the lowest coal seams in the paleocene marcelina formation paso diablo mine guasare basin northwestern venezuela to characterize crude oil samples from three wells in the nearby amana field and to evaluate oil source correlations of these crude oils with the paso diablo coal extracts the coals under study were classified as high volatile bituminous a or at the b a boundary and showed vitrinite contents between 50 0 and 89 4 vol liptinites ranging from 1 4 to 24 2 vol and inertinites in the 6 2 30 8 vol range results from organic geochemical investigations indicate that the guasare coals were generated in a limno telmatic to telmatic zone under fluctuating oxygen conditions a type iii kerogen with relatively high hydrogen content and a thermal maturity corresponding to the early oil window are proposed for these coals as supported by rock eval and petrographic data as well as biomarker interpretations oil generation potential from marcelina formation coals is probably due to the perhydrous nature of the vitrinite high bitumen contents and considerable liptinite concentrations mainly oil prone resinites and exsudatinites palynofacies observations denote a dominance of psilate pollen grains related to angiosperm plants and as expected type iii kerogens or humic coals in the studied seams the parent material of which contained a significant contribution of algae the non detection of 18 h oleanane does not preclude the fact that angiosperms are the dominant plants in the guasare paleomire on the other hand the characterization of the amana oils suggests that they all fall into a unique oil family the presence of 25 norhopanes in them could indicate paleobiodegradation and mixing from various hydrocarbon charges in the reservoir thus the crude oils from the amana field seem to be a mixture of one or more oil charges from the early mature marine carbonate source rocks of the la luna formation deposited under anoxic reducing conditions and a later pulse of hydrocarbon generation which originated from an unknown so far nonmarine source rock in this regard hydrocarbon liquid derived from the lowest marcelina coal seams may be tentatively identified as the latter oil charge also this work delineates some components of a currently subcommercial and hypothetical tertiary petroleum system identified and named as marcelina misoa c5 in the lake maracaibo region finally the coalbed gas contents of sampled coals were determined

development of the topography controlled upper odra ice lobe scandinavian ice sheet in the fore mountain area of southern poland during the saalian glaciation abstract during the saalian drenthe glaciation the upper odra ice lobe constituted the most southern part of the scandinavian ice sheet in central europe the lobe was situated in an area with varied topography in the foreland of a mountain range the ice lobe had a complex form because it was subdivided into several smaller sublobes the primary factors that controlled the lobe were investigated it was found that the ice lobe development depended largely on the topography but the lithology of the ice sheet substratum was also highly important the topography controlled the main movement direction of the ice and caused a concentration of the ice flow in the axial part of the silesian lowland between subglacial morphological barriers which thereby formed a corridor of relatively fast flowing ice which was probably streaming and which supplied the lobe the topography also determined the ice flow within the lobe which strongly matched the valley system the presence of sediments with relatively low permeability at the base of the lobe the quaternary deposits are underlain by neogene clays caused high pore water pressure in the subglacial zone and triggered the basal movement of the ice sheet which promoted a rapid flow of the ice and favoured the development of the lobe the basal tills deposited from the active and passive ice and extant till patches without a fluvioglacial cover atop some parts of the studied area indicate spatially varying ice flow dynamics especially in the later stage of glaciation certain parts of the lobe underwent stagnation while in other parts the ice was probably still active the varied behaviour of the ice within the lobe was determined primarily by the topography and lithology of the substratum which produced spatially varied marginal compression and basal friction a model of the development of the lobe is proposed

structure and origin of terpenoid hydrocarbons in some german coals abstract hydrocarbon extracts of coal samples from major coal fields in west germany have been investigated by gas chromatography mass spectrometry gc ms the samples are of carboniferous and tertiary age and derive from limnic and paralic environments the saar district the ruhr area and the lower rhine basin differences in facies maturity and age reflected in the distribution patterns of the extracted alkylcyclohexanes an unexpected occurrence of cyclic diterpenoid hydrocarbons in some samples of carboniferous age has been found the tetracyclic compounds mainly show phyllocladane type structures and can serve as source indicators hydrocarbons obtained from chemical degradation of the macromolecular material of the samples also revealed phyllocladane type compounds which are normally associated to resins of modern and extinct familes of conifers origin and structural variations of this class of hydrocarbons are discussed in terms of maturity and palaeobotanical implications

petroleum generation and migration in coal seams of the carboniferous ruhr basin northwest germany a series of 64 coal and clastic rock samples of westphalian age was taken from five narrow 3 m depth intervals between 1200 and 1530 m depth and studied by geochemical and petrological methods maturity increases regularly with increasing depth as indicated by several maturity parameters the influence of organic facies is evident in the uppermost coal seam 0 70 rr where a hand picked vitrinite contains less total extract and less saturated long chain hydrocarbons than a directly adjacent sporinite rich coal extracts from deeper and more mature coals are less affected by facies changes probably due to enhanced petroleum redistribution in the seams total yield and gross composition of extracts in the deepest seam 0 92 rr which is directly overlain by sandstone seem to be influenced by the preferential expulsion of saturated hydrocarbons

geochemical characteristics of terrigenous and marine sourced oils in hokkaido japan abstract crude oils in hokkaido japan are divided into two genetic groups based on bulk properties carbon isotope compositions and biomarker distributions one group is characterized by high carbon isotope canonical variables sofer 1984 high wax and low sulfur content high pr ph ratios low c27 c27 c29 sterane ratios relatively low ts ts tm ratios and the absence of tricyclic terpanes and c35 homohopanes these characteristics suggest that the oils were generated mainly from terrigenous organic matter in source rocks deposited under highly oxic conditions the other group is characterized by low canonical variables low wax and high sulfur content low pr ph ratios high c27 c27 c29 sterane ratios relatively high ts ts tm ratios and the presence of tricyclic terpanes and c35 homohopanes properties that suggest that they were generated from marine shales based on the biomarker distributions the terrigenous oils correlate to paleogene coals and coaly shales whereas the marine oils correlate to miocene marine shales the atomic h c ratios of the coals indicate that they have oil generating potential the geographic distribution of the terrigenous and marine source rocks and their thermal maturity control the distribution of the oils in hokkaido the geographic distribution of the paleogene coal bearing formations corresponds to the distribution of the terrigenous oils in central hokkaido the marine oils are restricted either to areas of high heat flow related to volcanic activity or to the area with thick neogene and quaternary sediments where the miocene source rocks are buried deep enough for oil generation

diterpenoid hydrocarbons in sediments from an offshore labrador well abstract aliphatic hydrocarbon fractions isolated from sediments r 0 0 4 of eocene palaeocene age taken between 2860 and 3055 m in an offshore labrador well were shown to be dominated by a number of compounds with kovats retention indices in the range 1875 1975 analyses of these hydrocarbons by gas chromatography and computerized gas chromatography mass spectrometry suggested that they were tricyclic diterpenoids interpretation of the mass spectra allowed structures to be assigned to some of the compounds and to be proposed for others they appear to belong to the primarane abietane and kaurane classes of hydrocarbons the diterpanes have been used to detect cavings in the deeper sediments between 3055 and 3270 m these compounds are either absent or trace components only of the dst 1 condensate 3212 3256 m or oil impregnating a sandstone core 3250 m and are only abundant in the cuttings from the same depth interval this occurrence of diterpanes in cuttings from the reservoir interval is due mostly to cavings resin like materials from which diterpanes are derived have not contributed significantly to the genesis of the condensate

ice dynamics at the mouth of ice stream b antarctica field data collected at the mouth of ice stream b show that the flow dynamics of this region are distinctly different than either the major portion of the ice stream upstream or the ice shelf downstream surface slopes in this region are as low as ice shelf surface slopes yet with the exception of patches of ice which may be floating the ice is grounded basal shear stress is negligible the resistance to flow being partitioned between shear at the sides and longitudinal gradients of longitudinal and transverse stress the surface is generally crevasse free features similar to ice rises are observed upstream of the grounding line their origin is uncertain but they move at velocities comparable to the surrounding ice the flow is laterally extensive and longitudinally compressive but there are large local variations of the strain rate from the regional trends the boundary between the two major tributaries to ice stream b followed with the radar is characterized by a band of strain rates much smaller than average detailed measurements at the downstream b network highlight this local variability of strain rates but confirm that there is a strong correlation between surface topography and strain rates the strain rates indicate that the undulating topography is locally generated the lower elevation ice is thicker and moves faster a velocity profile across the crevassed northern margin shows that the decrease of velocity toward the edge is nearly linear a calculation of ice stream discharge at this location agrees closely with two rather rough estimates of balance flux and is considerably larger than a third estimate the discharge of ice stream b does not appear to be significantly out of balance with published estimates of total ice accumulation within the present catchment basin

the ratios of dibenzothiophene to phenanthrene and pristane to phytane as indicators of depositional environment and lithology of petroleum source rocks abstract the ratio of dibenzothiophene to phenanthrene and the ratio of pristane to phytane when coupled together provide a novel and convenient way to infer crude oil source rock depositional environments and lithologies such knowledge can significantly assist in identifying the source formation s in a basin thereby providing valuable guidance for further exploration the ability to infer this information from analysis of a crude oil is especially valuable as frequently the earliest samples in a new area may be shows and or drill stem test samples from exploratory wells which are characteristically drilled on structural highs stratigraphically remote from the source formation s a cross plot of dibenzothiophene phenanthrene versus the pristane phytane ratios measured on seventy five crude oils from forty one known source rocks ranging in age from ordovician to miocene consistently classified the oils into the following environment lithology groups marine carbonate marine carbonate mixed and lacustrine sulfate rich lacustrine sulfate poor marine and lacustrine shale and fluvial deltaic carbonaceous shale and coal the dibenzothiophene phenanthrene ratio alone is an excellent indicator of source rock lithology with carbonates having ratios 1 and shales having ratios the dibenzothiophene to phenanthrene and the pristane to phytane ratios can also be used to classify source rock paleodepositional environments the classification scheme is based on the premise that these ratios reflect the different eh ph regimes resulting from the significant microbiological and chemical processes occurring during deposition and early diagenesis of sediments the dibenzothiophene phenanthrene ratio assesses the availability of reduced sulfur for incorporation into organic matter and the pristane phytane ratio assesses the redox conditions within the depositional environment interpretation of these ratios has been aided by quantitative biomarker analysis and by carbon isotope data for pristane and phytane obtained by gas chromatography isotope ratio mass spectrometry

landform and sediment imprints of fast glacier flow in the southwest laurentide ice sheet evidence for former fast glacier flow ice streaming in the southwest laurentide ice sheet is identified on the basis of regional glacial geomorphology and sedimentology highlighting the depositional processes associated with the margin of a terrestrial terminating ice stream preliminary mapping from a digital elevation model of alberta identifies corridors of smoothed topography and corridor parallel streamlined landforms megaflutes to mega lineations that display high levels of spatial coherency ridges that lie transverse to the dominant streamlining patterns are interpreted as a series of minor recessional push moraines b thrust block moraines or composite ridges hill hole pairs constructed during readvances surges and c overridden moraines cupola hills apparently of thrust origin together these landforms demarcate the beds and margins of former fast ice flow trunks or ice streams that terminated as lobate forms localised cross cutting and or misalignment of flow sets indicates temporal separation and the overprinting of ice streams lobes the fast flow tracks are separated by areas of interlobate or inter stream terrain in which moraines have been constructed at the margins of neighbouring competing ice streams outlet glaciers this inter stream terrain was covered by more sluggish non streaming ice during full glacial conditions thin tills at the centres of the fast flow corridors in many places unconformably overlying stratified sediments suggest that widespread till deformation may have been subordinate to basal sliding in driving fast ice flow but the general thickening of tills towards the lobate terminal margins of ice streams outlet glaciers is consistent with subglacial deformation theory in this area of relatively low relief we speculate that fast glacier flow or streaming was highly dynamic and transitory sometimes with fast flowing trunks topographically fixed in their onset zones and with the terminus migrating laterally the occurrence of minor push moraines and flutings and associated landforms because of their similarity to modern active temperate glacial landsystems are interpreted as indicative of ice lobe marginal oscillations possibly in response to seasonal climatic forcing in locations where meltwater was more effectively drained from the glacier bed further north the occurrence of surging glacier landsystems suggests that persistent fast glacier flow gave way to more transitory surging possibly in response to the decreasing size of ice reservoir areas in dispersal centres and also locally facilitated by ice bed decoupling and drawdown initiated by the development of ice dammed lakes copyright 2008 john wiley sons ltd

a role of eddies in formation and transport of north pacific subtropical mode water 1 hydrographic data acquired during 2001 by argo profiling floats deployed in the kuroshio recirculation region are used to verify the inference that mesoscale eddies prevailing in the recirculation region play an important role in the formation and transport of north pacific subtropical mode water npstmw that is the deeper winter mixed layer is formed preferentially where the thermocline is deeper in association with anticyclonic eddies in the succeeding seasons mesoscale eddies retain npstmw during their southwestward movement from the npstmw formation region so that anticylonic eddies contribute substantially to the npstmw transportation the spatial distributions of the mixed layer depth in winter and the npstmw thickness in the succeeding seasons based on the float data suggest that they are affected by mesoscale eddies the float data also provide the statistical relations of these quantities against the thermocline depth which are consistent with our inference

oil generation capacity of coals as a function of coal age and aliphatic structure abstract the relative proportions of aliphatic ch2 ch3 aliphatic hydrogen hali together with the aliphatic chain length in a series of carboniferous permian jurassic and cenozoic humic coals have been analysed using ftir and ruthenium tetroxide catalysed oxidation rtco followed by gc ms analysis of the n monocarboxylic acids esterified to assess their ability to generate oil most of the coals contain 2 11 vol liptinite only coals with almost similar hydrogen indices his were compared as they were considered to possess comparable hydrocarbon generation potentials all contain isolated aromatic hydrogen haro in the coal structure and a considerable proportion of aliphatic chains in the range c16 18 hi values cannot alone explain the proportion of aliphatic ch2 implying that for coals haro contributes to the measured hi cenozoic coals contain the highest proportion of aliphatic ch2 and hali and the content of longer chain aliphatics c18 increases considerably from palaeozoic to cenozoic coals aliphatic chains c18 are absent from or very restricted in the carboniferous coals and most of the permian coals indicate no or a negligible ability to generate oil jurassic coals show a slightly better potential whereas cenozoic coals contain aliphatic chains up to at least c35 demonstrating the greatest capacity to generate oil in addition to significant gas potential multivariate data analysis suggests that the aliphatic chains c24 are related to the collodetrinite liptodetrinite matrix which is a prominent constituent of cenozoic coals with regard to oil potential the coals from the major coal forming periods may be ranked carboniferous permian

the influence of sea surface temperature on surface wind in the eastern equatorial pacific seasonal and interannual variability abstract the climate of the eastern pacific exhibits a pronounced equatorial asymmetry boundary layer air originating in the southern hemisphere trades crosses the equator and flows into the intertropical convergence zone itcz whose southern limit is nearly always located at least 4 to the north of the equator the sea surface temperature sst distribution is characterized by a prominent cold tongue centered 1 s a strong frontal zone centered 2 n and a warm eastward current centered near 5 n the surface wind field exhibits a pronounced horizontal divergence as the air flows northward across the oceanic frontal zone these features vary in strength in response to the annual cycle and the el nino southern oscillation phenomenon the northward cross equatorial surface winds the cold tongue and the frontal zone all tend to be strongest during the cold season july through november during the cold season of the coldest years when the cold tongue is most prominent the cross equatorial flow t

saginaw lobe tunnel channels laurentide ice sheet and their significance in south central michigan usa abstract a network of tunnel channels in southern michigan records substantial subglacial meltwater activity beneath the saginaw lobe of the laurentide ice sheet the channels are incompletely filled with outwash contain eskers and in many places crosscut and continue beyond upland ridges previously mapped as recessional moraines the presence of the tunnel channels and drumlins on these upland ridges indicate that the ridges are not recessional moraines instead outwash fans and minor ridges record deglaciation in the area a palimpsest relationship between buried bedrock valleys and tunnel channels records the presence of multiple generations of tunnel channels evidence for a subglacial meltwater sheetflow consists of sheets of boulder gravel in upland 15 km wide with a hummocky upper surface the hummocks transform down flow into erosional remnant drumlins possibly the result of flow acceleration on a negative slope tunnel channels at the distal end of the drumlin swarm suggest collapse of the sheetflow into a channelized flow the tunnel channels then end at the sturgis moraine at the heads of large outwash fans the observed geomorphic relationships between tunnel channels moraines and drumlins in south central michigan are applicable to glacial landform studies elsewhere and indicate the important role of meltwater in landscape evolution

relations of petrographical and geochemical parameters in the middle miocene lavanttal lignite austria abstract samples from two lignite seams lower seam upper seam of the lavanttal basin austria and additional xylite were investigated for variations in maceral composition petrography based facies indicators bulk geochemical parameters and molecular composition of hydrocarbons both seams originated in a topogenous mire and evolved within a transgressive setting the final drowning of the mire is indicated by sapropelic shales whereas the sapropelic shale overlying the lower seam was deposited in a freshwater lake the sapropelic shale above the upper seam represents a brackish lake numerous relationships are found between petrography based facies indicators and the geochemical composition of organic matter the contents of macerals of the liptinite group are positively correlated with soluble organic matter som yields and hydrogen index hi consistent with maceral composition and high hi values enhanced proportions of short chain n alkanes which are predominantly found in algae and microorganisms are obtained from samples of the sapropelic shales the final drowning of the mire is reflected by decreasing pristane phytane ratios due to the rise in ground water table and the establishment of anaerobic conditions as well as by decreasing ratios of diasterenes sterenes indicating increasing ph values in the mire the degree of gelification of plant tissue gelification index is governed by the microbial activity in the mire as indicated by the hopanes concentration the differences in floral assemblage during the formation of the lavanttal lignite seams are reflected by major differences in tissue preservation preservation of plant tissue tpi in the lavanttal lignite is obviously controlled by the presence absence of decay resistant gymnosperms in the peat forming vegetation and additionally influenced by the relative contribution of wood to coal formation the results provide evidence that valuable information for coal facies characterization could be obtained by petrography based and geochemical facies indicators an influence of the floral assemblage gymnosperms angiosperms ratio and of the contribution of algal biomass on carbon isotopic composition of the organic matter 13c 24 2 to 28 6 is proposed carbon cycling during biogeochemical decomposition of plant tissue by bacteria is suggested to affect the 13c values of the coal the chemotaxonomical classification of the xylites as gymnosperm remnants based on the molecular composition of terpenoid biomarkers is corroborated by the carbon isotopic composition of the xylites mean 13c 24 1 and the extracted cellulose mean 13c 20 2 the higher isotopic difference of about 3 9 between cellulose and total organic carbon of the xylites compared to the difference between cellulose and wood found in modern trees is explained by the smaller effect of decomposition on 13c of cellulose

kerogen origin evolution and structure kerogen commonly defined as the insoluble macromolecular organic matter om dispersed in sedimentary rocks is by far the most abundant form of om on earth this fossil material is of prime importance as the source of oil and natural gas moreover kerogen can provide essential information on major topics such as past environments climates and biota this review reports the main advances in kerogen studies since the comprehensive synthesis edited by durand durand b ed kerogen insoluble organic matter from sedimentary rocks editions technip paris 1980 it is organized into eight sections the first two are concerned with the successive definitions of kerogen and the definition used here the different techniques used for kerogen isolation without loss or degradation and basic kerogen analysis the third and fourth focus on sedimentary om sources and preservation processes in relation to depositional environment including sedimentation conditions favourable for kerogen accumulation and extrapolation to past geological time great strides have been made in the latter topics over the last 25 years owing to a combination of classical studies in organic geochemistry and studies in other domains such as biogeochemistry oceanography hydrology and soil science along with the development of powerful analytical tools the next two sections deal with the different kerogen classifications by type and kerogen evolution and maturation upon burial in sediments structural modelling of coal and kerogen based on physical and or chemical structural analysis is described in the following section although only statistical the models thus derived provide a synthetic view of the main structural resemblances and differences among various samples in relation to source maturity or physicochemical properties finally the last section explores some of the advances in kerogen understanding expected for the near future the review includes a list containing about 500 references

glacial geology of western hudson strait canada with reference to laurentide ice sheet dynamics hudson strait is a large marine trough that connected the marine based interior of the laurentide ice sheet with the ocean field investigations of the glacial geology of western hudson strait have helped to define the role of the strait in laurentide ice sheet dynamics in general ice converged on western hudson strait from the north west and south upon reaching the strait ice flowing from foxe and ungava peninsulas turned eastward within less than 10 km of the coast to parallel eastwardly flowing ice in the strait glacial erosion of western hudson strait is identified as slight the texture carbonate content ph and the presence of several types of erratics distinguish till on nottingham salisbury and mill islands in western hudson strait from till on southern foxe peninsula and northern ungava peninsula till on the islands is characterized by higher ph and higher proportions of silt clay and carbonate than till on either adjacent peninsula in addition the presence of red sandstones porphyritic intrusives stromatolites omarolluks and iron formation are restricted to the islands with few exceptions that can be explained by ice rafting carbonate is present in the pebble and boulder fractions of till on foxe peninsula and in all fractions of till on the islands but is absent from till on ungava peninsula these data suggest that ice from distant and widely distributed source regions affected western hudson strait and along with evidence for a rapid change in ice flow direction along the margins of hudson strait suggest that the strait was occupied by a relatively fast moving ice stream that had a substantial impact on the interior of the ice sheet through downdraw

formation and subduction of central mode water based on profiling float data 2003 08 abstract temperature and salinity data from argo profiling floats in the north pacific during 2003 08 have been analyzed to study the structure of winter mixed layer north of the kuroshio extension and the subsurface potential vorticity distribution in the subtropical gyre in relation to the formation and subduction of the central mode water cmw in late winter two zonally elongated bands of deep mixed layer extend at 33 39 and 39 43 n from the east coast of japan to 160 w these correspond to the formation region of the lighter variety of cmw l cmw and that of the denser variety of cmw d cmw and the recently identified transition region mode water trmw respectively in the western part of the l cmw and d cmw trmw formation regions west of 170 e the winter mixed layer becomes deeper and lighter to the east i e to the downstream as a result the formed mode water is reentrained into the mixed layer in the farther east in the following winter and modified to the lighter water and is thus

carbonate till as a soft bed for pleistocene ice streams on the canadian shield north of lake superior silty carbonate till derived from erosion of paleozoic carbonate and proterozoic rocks within and adjacent to hudson bay covers extensive areas of the canadian shield north of lake superior it is hypothesized that this carbonate till could have acted as low resistance substrata for overriding ice streams by deforming and or supporting high subglacial water pressures contrary to assumptions presented in some current models for ice flow within the laurentide ice sheet it need not be assumed that shield terrain in these areas acted as a rigid bed generating large basal shear stresses and inhibiting ice flow indeed erratic dispersal patterns long distance glacial transport and splayed patterns of ice flow indicators in areas of thick till cover may be better explained by rapid ice flow events or ice streams enhanced by the thickness distribution impermeability and susceptibility to deformation of fine carbonate till

stable carbon isotope compositions of crude oils application to source depositional environments and petroleum alteration the carbon isotopic composition of the c15 saturate and aromatic hydrocarbon fractions and the gas chromatographs of the c15 saturate fraction of 339 oils were geochemically and statistically evaluated results of this study show that the average isotopic compositions of the c15 aromatic hydrocarbon fractions of oils sourced from terrigenous or marine organic matter are identical the average isotopic composition of the c15 saturate fraction of oils derived from terrigenous organic sources is slightly more negative 0 9 pmil than the average for marine oils but this difference is insufficient to be used as a reliable source indicator reports in the literature stating that marine oils are isotopically more positive than te rigenous oils and that the difference can be utilized to distinguish between the two are therefore not supported by this study the isotopic differences between oils sourced from terrigenous and marine organic matter do not manifest themselves in the range of absolute values of one oil fraction but rather in the isotopic relationship between the saturate and aromatic hydrocarbon fractions the isotopic relationship is the following oils of terrigenous organic source dgr13caro 1 12 dgr13csat 5 45 oils of marine organic source dgr13caro 1 10 dgr13csat 3 75 the difference between the two equations was evaluated statistically and a statistical parameter cv the canonical variable cv 2 53 dgr13csat 2 22 dgr13caro 11 65 was used to distinguish between marine and terrigenous oils cv values larger than 0 47 indicate predominantly a terrigenous organic source for the oil whereas cv values smaller than 0 47 indicate mostly a marine organic source thermal maturity differences in oils and isotopic variations in the source beds can cause as much as 2 pmil variations in the isotopic composition of one family of oils finally stable carbon isotopes can in some situations help correlate biodegraded oils to their nondegraded counterparts

annual and interannual variability in the kuroshio current system abstract individual seasonal 300 m temperature maps were constructed over the kuroshio current system from 130 e to 170 w for a 4 year period from summer 1976 through spring 1980 using transpac xbt data and jodc temperature depth data quasi stationary meanders in the kuroshic current system occurred at 137 c i e kuroshio meander at 144 e and 150 e i e lee wave meanders and near 160 e i e meander over the shatsky rise a composite of the paths of the kuroshio i e the 12 c isotherm from the individual seasonal maps and the total variance map finds nodes i e minima and anti nodes i e maxima of variability to have existed along the mean kuroshio path the anti nodes coincided with the location of the quasi stationary meanders the nodes in between zonal propagation of temperature anomalies accounted for 20 30 of the total interannual variance these temperature anomalies propagated eastward at 0 5 1 5 cm s 1 in the region 140 155 e and westward at 1 to 2 cm s 1 in the re

interpreting rock eval pyrolysis data using graphs of pyrolizable hydrocarbons vs total organic carbon kerogen the major organic component of sedimentary rocks is commonly analyzed by rock eval pyrolysis plotting the data on a graph of s 2 vs total organic carbon toc and determining the regression equation is the best method for determining the true average hydrogen index and measuring the adsorption of hydrocarbon by the rock matrix such a plot also indicates the type of kerogen present and avoids the problem of increasing hydrogen index with total organic carbon content with the s 2 vs toc diagram the organic component of different suites of samples may be compared and their petroleum generation potentials established as an example the diagrams are used to evaluate the sedimentary environments and petroleum potential of the paleogene evaporitic sediments of the mulhouse basin alsace france

trimethylnaphthalenes in crude oils and sediments effects of source and maturity abstract three sedimentary sequences and a number of crude oils have been analysed for trimethylnaphthalenes tmns using gas chromatography the sediments were found to contain enhanced relative abundances of 1 2 5 tmn and 1 2 7 tmn in samples of cretaceous age and younger this was especially pronounced in lower maturity sediments containing type iii organic matter older samples containing type iii organic matter were found to contain enhanced relative abundances of 1 2 5 tmn and lower relative abundances of 1 2 7 tmn 1 2 7 tmn appears to be derived directly from the structural degradation of oleanane type triterpenoids present in angiosperms and as such is proposed as a marker for this class of plant and indirectly therefore also for samples deposited since the early cretaceous the crude oils have been classified according to their trimethylnaphthalene compositions this classification enables crudes of higher plant origin to be identified and to be further classified according to whether the organic matter pre dated or post dated the evolution of angiosperms

quasi decadal variation in intensity of the western part of the winter subarctic sst front in the western north pacific the influence of kuroshio extension path state abstractvariations of the subarctic front saf which is extracted as a strong sea surface temperature sst gradient in the longitudinal band of 146 152 e were investigated over 30 winters january march from 1982 to 2011 using high spatial resolution satellite derived sst dataset and hydrographic observations the saf had little meridional movement in this longitudinal band lying between 40 and 41 n throughout the analysis period the saf intensity had a dominant quasi decadal time scale about 8 yr its intensity in the strong phase was up to about 50 higher than in the weak phase the saf intensity strongly reflected upper ocean conditions in the kuroshio oyashio confluence koc region just south of the saf in the strong saf phase large positive anomalies in both temperature and salinity were found in the koc region not only at the sea surface but also below 300 m and the water properties in the koc region were those of the kuroshio water the warm salty water in the koc region was supp

climate driven hydrologic transients in lake sediment records calibration of groundwater conditions using 20th century drought abstract the effect of 20th century drought on groundwater and lakes in a climatically sensitive area of the northern great plains grant county western minnesota was investigated by analysis of lake sediments and historical air photos in conjunction with groundwater flow simulations drought caused an observed 4 0 to 5 1 m lake head decline between 1923 and 1938 all but three either dried completely or declined to 210 pb dated sediment core was analyzed for ostracode species distribution and geochemistry of c rawsoni shells 18 o 13 c mg ca sr ca mg ca and 13 c increased during drought at the same time that salinity tolerant ostracodes thrived suggesting increasing salinity however 18 o decreased during drought anti correlative with mg ca a numerical model for transient response of groundwater flow to drought modeled after that of 1923 38 was constrained by drought end recessional strand lines observed on air photos of one lake with strand line elevations inferred from bathymetry simulated lake water level declines in the first 15 drought years were consistent with strand line elevations the rate of decline was exponential at drought onset slowing as water in lakes and wetlands receded to below land surface and lake evaporation declined a near steady state was attained between 40 and 50 simulation years after onset of drought with the water table from 1 5 m below the level of dry lakebeds and only the two deepest lakes still holding water they were however greatly constricted in area and depth simulated evaporation fluxes were reduced by over 50 within 15 years despite increased et rates due to lake area constriction and water table declines both relate to land surface morphology beneath and around lakes model results suggest that lake bed elevations exert control on the rate and ultimate level to which groundwater is depressed by drought the deepest lakes in any region will tend to become the focus of groundwater flow during sustained drought once lakes around it dry out the unexpected finding of decreasing shell 18 o in response to drought is interpreted as some combination of source and or evaporation reduction effects such as seasonality of recharge precipitation or reduced et flux from wetlands that seep back into lakes

comparison of resinite related aromatic biomarker distributions in cretaceous tertiary coals from canada and germany a set of 13 cretaceous tertiary coals from western canadian coal deposits and two cretaneous coals from the southern part of the lower saxony basin of germany have been investigated using microscopial and organic geochemical methods the coals are in the ranl range of lignite to medium volatile bituminous 0 37 1 13 rr petrographically the coals are characterized by varying proportions in vitrinite inertinite and liptinite groups in most of the coals resinite constitutes the major liptinite component both of the german wealden coals are composed exclusively of conifer needles gc ms analyses indicate differences in the composition of resin related molecular biomarkers comparing samples from both deposits in the canadian coals of moderate rank 0 4 0 8 rr resin related napthalene derivatives are associated with tricyclic aromatic hydrocarbons such as retene abieta 6 8 11 13 tetraene simonellite and c5 phenanthrene samples higher in rank about 1 1 rr provide fully aromatized and partly desalkylated phenanthrene homologues generation of 1 methylphenanthrene from retene during maturation affects molecular rank parameters like mpr and mpi 1 additionally an intra seam homogenization of resin derived aromatic hydrocarbon is observed in comparison the german wealden coal extracts are dominated by bicyclic aromatic hydrocarbons and they are poor in tricyclic hydrocarbons analyses of hand picked macerals resinites and cutinites by thermodesorption coupled to gc ms indicate the presence of two potential sources for the naphthalene derivatives c4 tetralin is primarily associated with the resins of abietites linkii 1 2 5 trimethylnaphthalene and 1 2 5 6 tetramethylnapthhalene are probably derived from the fluorinite filling of the conifer needles

reconstruction of floral changes during deposition of the miocene embalut coal from kutai basin mahakam delta east kalimantan indonesia by use of aromatic hydrocarbon composition and stable carbon isotope ratios of organic matter the distribution of aromatic hydrocarbons and stable carbon isotope ratios of organic matter in a series of nine miocene embalut coal samples obtained from nine coal seams of kutai basin east kalimantan indonesia were studied the rank of the embalut coals ranged from lignites to low rank sub bituminous coals 0 36 0 50 rr based on measurements of huminite reflectance the aromatic hydrocarbon fractions of all coal samples were dominated by cadalene in the lower boiling point range and picene derivatives in the higher boiling point range of the gas chromatograms cadalene can be attributed to the contribution of dipterocarpaceae and various hydrated picenes to the contribution of additional angiosperms to the coal forming vegetation the picenes originate from alpha and beta amyrin however in some coal samples minor amounts of simonellite and retene were also detected which argues for an additional contribution of gymnosperms conifers to coal forming vegetation preferentially in the middle miocene and at the beginning of the late miocene the results of stable carbon isotope ratios d 13

determining the petroleum generating potential of coal using organic geochemistry and organic petrology abstract the ardjuna basin of northwest java is typical of many tertiary basins in that it contains high wax crude oil pyrolysis gas chromatography revealed that potential precursors of long chain waxy paraffins are present in coals of the talang akar formation and are most abundant in those that are rich in matrix liptinite conversely it was not possible to estimate waxy oil generating potential using rock eval because pyrolysates from talang akar coal are mainly comprised of naphthenic and aromatic compounds these being derived from resinite and fluorescing vitrinite because of a controlling influence by the abundance of these macerals changes in hydrogen index could not be used to assess maturity resinite and related macerals might play an especially important role in petroleum expulsion as evidenced by their high genetic potential and hence inherent capability of saturating the source rock pore system it is speculated that their maturation products while not constituting typical crude oil might pervade the coal fabric deactivate adsorptive sites and hence facilitate the expulsion of waxy oil that is generated from matrix liptinite

covariations of sea surface temperature and wind over the kuroshio and its extension evidence for ocean to atmosphere feedback abstract satellite microwave measurements are analyzed revealing robust covariability in sea surface temperature sst and wind speed over the kuroshio extension ke east of japan ocean hydrodynamic instabilities cause the ke to meander and result in large sst variations increased reduced wind speeds are found to be associated with warm cold sst anomalies this positive sst wind correlation in ke is confirmed by in situ buoy measurements and is consistent with a vertical shear adjustment mechanism namely an increase in sst reduces the static stability of the near surface atmosphere intensifying the vertical turbulence mixing and bringing fast moving air from aloft to the sea surface south of japan the kuroshio is known to vary between nearshore and offshore paths these paths are very persistent and can last for months to years as the kuroshio shifts its path coherent wind changes are detected from satellite data in particular winds are high south of tokyo when the kuroshio takes the near

natural gas washing induces condensate formation from coal measures in the pinghu slope belt of the xihu depression east china sea basin insights from fluid inclusion geochemistry and rock gold tube pyrolysis abstract a systematic study into the origin and potential formation processes of condensates in the pinghu slope belt of the xihu depression east china sea basin was conducted using fluid inclusion analysis petroleum geochemistry and rock gold tube pyrolysis grains containing oil inclusions goi technique well logging and formation testing together indicate that the present day gas condensate layer has evolved from a paleo oil layer biomarkers from oil inclusions indicate that these paleo oils were generated from coal measures at a moderate maturity level based on organic macerals elemental ratios of kerogens rock eval pyrolysis and results from gold tube pyrolysis experiments the coal measures are evaluated as source rocks prone to gas generation and capable of oil formation at moderate levels of maturity this maturity level coincides with present day condensate maturities determined from a series of molecular maturity ratios vitrinite reflectance 0 7 1 0 ro biomarkers related to specific sources suggest that the condensates are also coal derived these observations suggest that the condensates are derived from secondary alteration following paleo oil accumulation rather than being related to the thermal degradation of resin rich organic matter at a low maturity level or the thermal cracking of kerogen at a high maturity level some condensates are characterized by a significant loss of n alkanes with low carbon numbers and relatively high toluene n heptane tol nc7 ratios this indicates that the paleo oil reservoirs have been subjected to varying degrees of gas washing which resulted in condensate formation as opposed to the process of oil cracking under high temperatures subsequent interactions between gas and paleo oils resulted in oil inclusions showing fluorescence varying from near yellow to blue variable vapor volume fractions measured in the same oil assemblage are the result of two phase trapping of oil and gas the widely observed presence of bitumen asphaltene in the reservoir pores and bitumen bearing oil inclusions is considered to be due to gas deasphalting homogenization temperatures th of associated aqueous inclusions and burial thermal curves suggest that the initial paleo oil reservoirs formed in the late miocene excess gas composed of local mature gas and heterochthonous high to over mature gas migrated into the paleo oil reservoirs later in the quaternary this process not only resulted in the formation of condensates but also led to vertical differentiation of density and wax content in the reservoirs

record of the vistula ice lobe advances in the late weichselian glacial sequence in north central poland during the last glacial maximum lgm the vistula ice lobe was one of the key morphological elements at the southern margin of the scandinavian ice sheet in north central poland the area of the vistula ice lobe experienced two ice sheet advances of varied extent the older one is correlated with the leszno brandenburg phase and the younger one is correlated with the poznan frankfurt phase sedimentological research and luminescence dating of the late weichselian glacial sequence in the vistula ice lobe area was conducted a new scenario of the late weichselian ice events in the area is presented the limit of the leszno phase within the vistula ice lobe was much smaller than had been accepted previously and its age is estimated to be about 20 300 bp significant ice sheet retreat was

sesqui and diterpenoid biomarkers preserved in taxodium rich oligocene oxbow lake clays weisselster basin germany several diterpenoids of the abietane pimarane and phyllocladane type and three cadalanetype sesquiterpenoids have been identified in the organic solvent extracts of lower oligocene clay sediments haselbach strata saxony germany the sediment contains needles and cone scales of a fossil taxodium species which represents the only conifer in the samples a clear correlation between the observed conifer biomarkers and taxodium is evident apart from diterpenoids detected previously in other sediments a new diaromatic totarane diterpenoid is reported in isolated fossil and recent taxodium needles and cone scales as well as in the haselbach clays a phenolic diterpenoid of the abietane type ferruginol has been identified the results indicate that the taxodium rich clay samples contain several diterpenoids which so far have been used as biomarkers for other conifer families and thus the chemotaxonomical use of diterpenoid biomarkers for the differentiation of fossil conifer families has to be revised

surface form of the southern laurentide ice sheet and its implications to ice sheet dynamics reconstructions of the ice surface morphology of several lobes of the southern laurentide ice sheet reinforce previous arguments that this sector of the ice sheet was thin and low sloping driving stresses estimated from the geometry of the reconstructed ice surfaces are 0 7 4 3 kpa for the 14 ka des moines lobe 0 9 1 2 kpa for the 14 ka james lobe 0 9 1 7 kpa for the 18 20 ka lake michigan lobe 1 8 2 9 kpa for the 15 18 ka chippewa sublobe and 17 22 kpa for the 15 18 ka green bay lobe previous estimates of rates of ice margin advance 450 2 000 m yr indicate moderate to fast ice velocities for the ice lobes reconstructed driving stresses and velocity estimates of the des moines james and lake michigan lobes are analogous to the distal ends ice plains of low sloping 0 4 x 10 3 but fast moving 500 m yr west antarctic ice streams whose dynamics have been attributed to sliding and or subglacial sediment deformation by pervasive shear these reconstructions support recent models of the laurentide ice sheet which include movement by sliding or by subglacial sediment deformation along its southern western and northwestern sectors evidence for either mechanism should be represented in the sedimentologic and geomorphic records thin ice in these regions indicates that the laurentide ice sheet contained less ice volume and represented less of an orographic obstacle to atmospheric circulation than has been considered in models of the ice sheet on a rigid bed with steep profiles

flow mechanism of glaciers on soft beds subhourly measurements of bed deformation bed shear strength subglacial water pressure and surface speed at storglaciaren a glacier in northern sweden showed that the shear strain rates of the bed decrease during periods of high water pressure and surface speed high water pressures appear to be accompanied by a reduction in the coupling of ice with the bed that is sufficient to reduce or eliminate shearing the instability of large ice masses may result from similar decoupling rather than from pervasive bed deformation as has been commonly thought

organic matter provenance and depositional environment of marine to continental mudstones and coals in eastern ordos basin china evidence from molecular geochemistry and petrology abstract cyclothems composed of interbedded mudstone coal and sandstone layers make up the taiyuan and shanxi formations in the late carboniferous to early permian in north china under a marine to continental depositional environment the cyclothems act as important fossil energy hosts such as coalbeds hydrocarbon source rocks and unconventional natural gas reservoirs organic geochemistry and petrology of mudstones and coals in the taiyuan and shanxi formations in the eastern ordos basin were studied to reveal the organic matter sources and paleoenvironments total organic carbon toc contents vary from 1 1 wt mudstone to 72 6 wt coal the samples are mainly within the oil window with the tmax values ranging from 433 to 469 c organic petrology and source biomarkers indicate that the mudstones were sourced from a mixed organic matter input and terrigenous organic matter predominates over aquatic organic matter the coals are mostly sourced by terrigenous organic matter inputs high concentrations of hopanes argue for a strong bacterial input some m z 217 mass chromatograms have peaks at the hopanes retention times as a result of high hopane to sterane ratios these hopane derived peaks do not interfere the identification of the steranes because the hopanes and the steranes have different retention times maturity dependent biomarkers demonstrate that the samples have been thermally mature which agree with the tmax values anomalously low c29 20s 20s 20r and c29 sterane ratios are present in all the samples and are interpreted as due to the terrigenous organic matter input or the coal related depositional environment in addition biomarkers and iron sulfide morphology indicate that the organic matter of the mudstones deposited in a proximal setting with shallow brackish fresh water bodies with consideration of preservation of organic matter the redox conditions are dysoxic redox oscillations resulted in the records of oxic conditions in some samples finally the coals and the mudstones mainly generate gas and have poor oil generative potential

antarctic ice streams a review an ice stream is a part of an inland ice sheet that flows rapidly through the surrounding ice the distinction between an ice sheet and an outlet glacier is clear in principle but muddy in practice many antarctic glaciers are intermediate in character the ross ice streams which flow through the west antarctic inland ice into the ross ice shelf are distinct in character differing even from other ice streams in the marine ice sheet of west antarctica their surface elevation profiles are low their bed slopes are low and smooth and their driving stresses diminish monotonically downglacier in transverse profile they are broader in relation to ice thickness and exhibit shallower subglacial troughs than other ice streams many models for the fast sliding of glaciers have been applied to the ross ice streams most have included in some form a reduction in basal drag resulting from a lesser effective than glaciostatic pressure at the bed most models are only semi physical at best so need to be tuned by fitting to assumed parameters at some place or places in the real ice sheet the recent discovery of a very small effective pressure beneath one ice stream consequently has led to some gross errors in the velocities predicted by the models the difficulty may be resolved if it is true as recent experiments suggest that ice stream b and by extrapolation other ross ice streams as well slide on a deforming bed that absorbs most or all of the differential motion between the ice and the bedrock