marine ice sheet stability we examine the stability of two dimensional marine ice sheets in steady state the dynamics of marine ice sheets is described by a viscous thin film model with two stefan type boundary conditions at the moving boundary or grounding line that marks the transition from grounded to floating ice one of these boundary conditions constrains ice thickness to be at a local critical value for flotation which depends on depth to bedrock at the grounding line the other condition sets ice flux as a function of ice thickness at the grounding line depending on the shape of the bedrock multiple equilibria may be possible using a linear stability analysis we confirm a long standing heuristic argument that asserts that the stability of these equilibria is determined by a simple mass balance consideration if an advance in the grounding line away from its steady state position leads to a net mass gain the steady state is unstable and stable otherwise this also confirms that grounding lines can only be stable in positions where bedrock slopes downwards sufficiently steeply

high temperature alteration and porosity generation in upper ordovician microbial reefs hudson bay intracratonic basin arctic canada abstract upper ordovician biohermal mounds of the red head rapids river formation in the hudson bay basin consist of microbial and sponge boundstone and cementstone the cementstone is made up of isopachous layers and botryoids of former aragonite now calcite secondary dissolution porosity and small fractures are cutting through the bioherm secondary pore fillings consist of drusy calcite cement and subsequent bitumen the 18ovpdb and 13cvpdb values of late cements are invariably more negative than those of the marine cements fluid inclusion microthermometry documents the presence of two distinct populations of homogenization temperatures one in secondary pore filling burial calcite cement th average 93 10 c and a second one in recrystallized marine calcite cements th average 118 25 c the combined 18ovpdb and th data suggest that burial cements precipitated from a fluid having 18osmow values between 0 5 and 2 whereas the marine cement data indicate resetting of the fluid inclusions in the presence of a high temperature 18osmow heavy brine 2 5 to 12 the lower temperature fluid inclusions of the late pore filling cement agree with recent apatite fission track data suggesting early oil window temperature at maximum burial the higher th values recorded in the marine cement represent resetting of initial or entrapment of new fluid inclusions from fracture controlled circulation of basement derived fluids the petrographic and geochemical data suggest that fracture controlled high temperature brine circulation occurred after the inception of burial and recrystallization of original marine aragonite to calcite which resulted in the generation of significant secondary porosity that was later filled by lower temperature burial cements and hydrocarbons

on the factors behind large labrador sea tides during the last glacial cycle and the potential implications for heinrich events 1 labrador sea ls tidal elevations over the last glacial cycle are investigated in a near global numerical model that accurately captures the present day tides from 65 ka to 7 ka the modeled elevations at the debouchement point of the hudson strait ice stream in the ls are exceptionally large comparable to the largest elevations seen anywhere in the present day ocean new numerical simulations performed for this article demonstrate that both local changes in basin geometry e g ice cover over hudson bay and changes outside of the ls led to enhanced ls paleotides new simulations run at higher horizontal resolution and a considered examination of uncertainties including uncertainties in the adopted sea level models strengthen confidence in the robustness of the large ls paleotides the tide model is run with both spatially uniform sea level drops taken from curves of eustatic and red sea sea levels versus time and spatially variable sea level maps taken from two different gravitationally self consistent viscoelastic solid earth sea level models which both account for ice sheet geometry the tides are larger when the spatially variable sea level models are used observations in present day antarctica indicate that the mechanical action of tides significantly impacts the dynamics of both continental ice streams and their associated floating ice shelves it is postulated here that large ls paleotides played a key role in the formation of heinrich event icebergs that is massive discharges of ice from the ls into the glacial north atlantic ocean the paleotide calculations described here provide a potential explanation for why the ls region more than any other dominated the production of heinrich event icebergs most previous hypotheses of a tidal role in climate variability and ice sheet dynamics focus on tidal mixing in contrast here the role of tidal mechanical forcing of ice sheets is emphasized

on the hemispheric origins of meltwater pulse 1a abstract during the glacial interglacial transition that began subsequent to the last glacial maximum approximately 21 000 calendar years ago globally averaged eustatic sea level rose by approximately 120 m as climate warmed to its current holocene state this rise of relative sea level rsl did not occur smoothly however but was characterized by the occurrence of one or more episodes of extremely rapid increase the most extreme of these events has come to be referred to as meltwater pulse 1a and was initially identified in the coral based record of rsl history from the island of barbados in the caribbean sea although it has usually been assumed that this episode of rapid rsl rise was derivative of a partial collapse of the northern hemisphere ice sheets it has recently been suggested that this pulse could have originated in a dramatic melt back of the antarctic ice sheet in this paper the arguments presented in favour of the southern hemisphere source are revisited in order to assess the plausibility of this alternative scenario based upon the analyses presented it is concluded that the evidence previously provided in support of the southern hemisphere scenario is in fact unable to rule out an entirely northern hemisphere source for the meltwater pulse 1a since explicit evidence does exist that both the laurentide and fennoscandian ice sheets contributed to this event and that antarctic ice sheet melting occurred significantly later the southern hemisphere appears not to have been a prime mover of northern hemisphere events

hydrocarbon source rock characterization burial history and thermal maturity of the steele niobrara and mowry formations at teapot dome wyoming abstract teapot dome oilfield near the town of midwest wyoming has been the testing site of numerous drilling and production techniques since the early 1900 s the structure is a doubly plunging basement cored anticline that formed during the laramide orogeny with sediments ranging from cambrian to quaternary the steele niobrara and mowry formations are potential source rocks in the area in this study we combine geochemical analyses with one dimensional modeling of burial history thermal maturity and timing of petroleum generation to evaluate the potential of the field for unconventional exploration rock eval pyrolysis and oxidation results show a mixture of type ii and type iii kerogen in the niobrara and mowry formations and no hydrocarbon generation potential for the steele formation these geochemical results combined with regional tectonics stratigraphy and sedimentological conditions were implemented into burial history and maturation models results from the modeling show that the niobrara and mowry formations are in the early oil generation window the mowry is the most mature of the three formations but only 10 of the kerogen has been converted to oil the study area did not reach the thermal maturity required to generate the significant amount of oil and gas produced to date from the structure the results and method of this study can easily be extrapolated to better constrain the basin evolution of nearby fields this study is significant for further exploration in other established laramide basins with similar formations

cadalenes and norcadalenes in organic rich shales of the permian irati formation parana basin brazil tracers for terrestrial input or also indicators of temperature controlled organic inorganic interactions abstract cadalene isocadalene and a series of norcadalenes were identified in black shales of the permian irati formation in the northeastern and central eastern parana basin brazil the origin of their isomers with an isopropyl substituent is potentially related to higher plants and likely reflects the spreading of pteridophytes and gymnosperms after the glaciation of southern gondwana a general increase in the relative abundance of isocadalene 1 6 dimethyl 3 isopropylnaphthalene the isomer co occurs in with increasing thermal maturity at the base of the amaral machado quarry northeastern basin and refers to the acid catalyzed rearrangement of cadalene 1 6 dimethyl 4 isopropylnaphthalene the isomer due to the presence of montmorillonite via an organic inorganic interaction this localized and incipient maturation can be related to diabase sills of the serra geral formation similar maturation due to heating also affected the distribution of the norcadalenes by thermally stabilizing their isomers with an isopropyl substituent in addition to the formation of related compounds with an ethyl substituent based on this a norcadalene ratio is proposed which is the sum of the 1 6 dimethyl 4 ethylnaphthalene and 1 6 dimethyl 3 ethylnaphthalene over the sum of the 1 isopropyl 4 methylnaphthalene and 1 isopropyl 7 methylnaphthalene the results of this ratio and the established cadalene ratio resemble each other whereas samples from the sao mateus do sul quarry central eastern basin were not affected by thermal maturation and are characterized by a uniform distribution of the cadalenes and norcadalenes

space geodetic and water level gauge constraints on continental uplift and tilting over north america regional convergence of the ice 6g_c vm5a vm6 models

interhemispheric air temperature phase relationships in the nonlinear dansgaard oeschger oscillation it has previously been suggested that the southern ocean might act as a thermal reservoir in mediating the relationship between the northern and southern hemisphere air temperature signals during a dansgaard oeschger cycle on the basis of a climate model based analysis we demonstrate on the contrary that it is equatorial and subtropical north atlantic thermocline waters that act so as to integrate and damp the northern hemisphere signal to fix the amplitude and phase of the southern hemisphere counterpart to the more intense north atlantic component of the oscillation the dynamics of the southern ocean component of the atlantic meridional overturning circulation are critical in explaining the evolution of the interhemispheric temperature phase relationships european project for ice coring in antarctica dronning maud land inferred air temperature variations are in phase with sea surface temperatures north of the antarctic sea ice edge suggesting that it is via a fast atmospheric pathway that this temperature signal is transmitted into the antarctic ice core record

post oil solid bitumen network in the woodford shale usa a potential primary migration pathway abstract an important if not predominant component of porosity in many gas shales has been identified in organic matter an organic network in shales has been described in the literature as organic matter generalized term kerogen primary or bitumen secondary recognition of the type and origin of an organic network in shales has relevance in establishing the origin and timing of porosity and fracture development the pervasive nature of the organic network adopting the shape of pores in type ii kerogen rich woodford shale suggests it is the residue of primary oil migration we use the term post oil solid bitumen to distinguish this bitumen occurrence from pre oil solid bitumen defined as a precursor of oil three forms of this post oil solid bitumen network are recognized in reflected white light at 500 magnification and confirmed in backscattered scanning electron microscope images at 2500 magnification namely speckled 1 2 m wispy 2 5 m and connected 5 m the post oil solid bitumen network demonstrates the prior occurrence of oil generation and migration within this hydrocarbon source rock provides porosity for hydrocarbon storage sites and forms hydrocarbon migration pathways

once again once again tidal friction topex poseidon t p altimetry has reopened the problem of how tidal dissipation is to be allocated there is now general agreement of a m2 dissipation by 2 5 terawatts 1 tw 1012 w based on four quite separate astronomic observational programs allowing for the bodily tide dissipation of 0 1 tw leaves 2 4 tw for ocean dissipation the traditional disposal sites since jeffreys 1920 have been in the turbulent bottom boundary layer bbl of marginal seas and the modern estimate of about 2 1 tw is in this tradition but the distribution among the shallow seas has changed radically from time to time independent estimates of energy flux into the marginal seas are not in good agreement with the bbl estimates t p altimetry has contributed to the tidal problem in two important ways the assimilation of global altimetry into laplace tidal solutions has led to accurate representations of the global tides as evidenced by the very close agreement between the astronomic measurements and the computed 2 4 tw working of the moon on the global ocean second the detection by ray and mitchum 1996 of small surface manifestation of internal tides radiating away from the hawaiian chain has led to global estimates of 0 2 to 0 4 tw of conversion of surface tides to internal tides measurements of ocean microstructure yields 0 2 tw of global dissipation by pelagic turbulence away from topography we propose that pelagic turbulence is maintained by topographic scattering of barotropic into baroclinic tidal energy via internal tides and internal waves previous estimates by baines 1974 baines 1982 of this conversion along 150 000 km of continental coastlines gave a negligible 0 02 tw evidently the important conversion takes place along mid ocean ridges the maintenance of the abyssal global stratification requires a much larger expenditure of power 2 tw versus 0 2 tw this is usually attributed to wind forcing if tidal power is to play a significant role here then the bbl estimates need to be reduced the challenge is to estimate dissipation from the energy flux divergence in the t p adjusted tidal models without prior assumptions concerning the dissipation processes

electrical resistivity and chemical properties of kerogen isolated from organic rich mudrocks abstractlow electrical resistivity measurements in organic rich mudrocks are commonplace in highly mature zones these low resistivity values are usually difficult to justify and lead to overestimation of water saturation when using conventional resistivity porosity saturation models e g dual water and waxman smits previous publications suggest that the electrical conductivity of kerogen increases when it thermally matures this increase in thermal maturity of kerogen might contribute to low resistivity measurements in organic rich mudrocks however electrical properties of kerogen within these rocks have not yet been quantified experimentally we have introduced a technique to quantify electrical resistivity of kerogen through combined experimental and numerical approaches and quantified electrical resistivity of kerogen samples from the haynesville and eagle ford formations we first isolated kerogen from mudrock samples using physical and chemical treatments the isolated kerogen powder was then

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

thermohaline instability and the formation of glacial north atlantic super polynyas at the onset of dansgaard oeschger warming events late quaternary rapid warming events inferred on the basis of oxygen isotopic data from greenland ice cores are the most prominent characteristic of millennial scale dansgaard oeschger oscillations in a coupled climate model simulation which has accurately reproduced this oscillatory behavior for the first time we show that formation of a glacial north atlantic super polynya characterizes the initial stage of transition from cold stadial to warm interstadial conditions the winter polynya forms within the otherwise sea ice covered north atlantic as a consequence of the onset of a thermohaline convective instability beneath an extensive stadial sea ice lid early in the stadial period the tendency for thermal convective instability of an extensive warm pool beneath the sea ice lid is strongly inhibited by a stabilizing vertical salinity gradient which gradually diminishes until a thermohaline convective instability occurs that leads to polynya formation and the rapid retreat of north atlantic sea ice cover

binge purge oscillations of the laurentide ice sheet as a cause of the north atlantic s heinrich events ice rafted debris in sediment cores from the north atlantic suggests that the laurentide ice sheet lis periodically disgorged icebergs in brief but violent episodes which occurred approximately every 7 000 years here i propose that heinrich events i e what these episodes are called were caused by free oscillations in the flow of the laurentide ice sheet which arose because the floor of hudson bay and hudson strait is covered with soft unconsolidated sediment that forms a slippery lubricant when thawed the proposed heinrich event cycle has two phases the growth phase occurs when the sediment is frozen and the lis is stranded immobile on a rigid bed the volume of the lis slowly grows during this phase at a rate dictated by snow accumulation the purge phase occurs when the basal sediment thaws and a basally lubricated discharge pathway i e an ice stream such as those which occur in west antarctica today developes through hudson strait the volume of the lis rapidly equilibrates to the reduced basal friction during this phase by dumping icebergs into the labrador sea the periodicity t k sl2g 2 7000 years of the proposed heinrich event cycle is a function of the thermal conductivity and diffusivity of ice k and respectively the atmospheric sea level temperature sl in degrees celsius and the excess geothermal heat flux defined by g g k where is the atmospheric lapse rate and g is the geothermal heat flux agreement between the predicted t and the apparent periodicity implied by the marine record is the main virtue of the free oscillation mechanism i propose an alternative mechanism in which heinrich events are forced by periodic variations in external climate is implausible because periodic atmospheric temperature perturbations are strongly attenuated with depth in an ice sheet

oxygen isotopes and sea level from the time that detailed oxygen isotope records derived from foraminifera living in the constant temperature environment of the abyssal ocean became available there has been a discrepancy between the ice volume record that these records imply and that derived from the altitude of dated coral terraces around the world here we re examine the data and conclude that the temperature of the abyssal ocean has been an actively varying component of the climate system

the petroleum potential of tertiary coals from western indonesia relationship to mire type and sequence stratigraphic setting abstract more than 500 deltaic sediments from 14 basins in western indonesia were subjected to detailed geochemical petrographic and palynological analysis the resultant data represent each of the main peat forming tectonostratigraphic episodes paleogene syn rift transgressive paleogene neogene post rift transgressive and neogene syn tectonic regressive of the indonesian tertiary the coals are hydrogen rich with average hydrogen index hi of 250 300 and atomic h c ratios of 1 0 1 3 where immature paleogene coals from syn rift transgressive systems tracts are more hydrogen rich than neogene coals from syn tectonic regressive systems tracts and upon pyrolysis yield lower gas oil ratios implying they are more oil prone pliocene coals from a strongly regressive sequence in the sumatran fore arc are very hydrogen poor with average hi of 138 indonesian coals display a systematic increase in hi with increasing rank peaking at a tmax of c 430 c suggesting that rock eval pyrolysis underestimates petroleum potential in low rank coals the increase in hi is accompanied by a decrease in s1 toc ratio and the disappearance of suberinite and resinite reflecting the assimilation of these macerals into the coal matrix with increasing diagenesis petrographic analyses reveal a very poor correlation between liptinite content and hi the term detrovitrinite index di is coined to describe the ratio of detrovitrinite total vitrinite a better relationship between hi and di suggests that vitrinite type is a more important control on petroleum potential than liptinite content the coals are classified into four sub types i iv on the basis of their pyrolysis potential and petrographic composition sub types i ii and iii are low ash coals and are likely to have been deposited in raised mires sub type i is hydrogen rich and primarily represents middle to late miocene coals deposited in a regressive megasequence sub type ii coals are hydrogen poor and occur in multiple tectonostratigraphic settings sub type iii consists of very hydrogen poor pliocene coals from the rapidly subsiding west sumatran fore arc sub type iv is hydrogen rich and consists of high ash eocene coals deposited in submerged mires in a transgressive syn rift setting a close relationship between hi and tissue preservation index tpi suggests that the degree of degradation of the peat is an important factor in determining petroleum potential highly degraded peats result in hydrogen rich coals with a higher proportion of vitrinite of detrital or allochthonous origin the degree of degradation is most likely related to the amount of time the peat spends within the zone of influence of the water table and is unlikely to be directly related to tectonostratigraphic setting

megatides in the arctic ocean under glacial conditions 1 over the history of the earth changes in ocean depth and coastal configuration have led to considerable variations in the pattern and amplitude of ocean tides here we perform global simulations of ocean tides for the last glacial maximum using new data sets for both ocean depth and density stratification we show how the configuration of the arctic ocean which was almost entirely enclosed by continents at that time leads to the near resonant excitation of large semi diurnal tides under certain conditions this previously unidentified arctic tide is massively amplified in the canadian archipelago such tides may have played a role in destabilizing the coastal margins of north american ice sheets with implications for rapid changes in the earth s climate and ocean circulation

iceberg discharges into the north atlantic on millennial time scales during the last glaciation high resolution studies of north atlantic deep sea cores demonstrate that prominent increases in iceberg calving recurred at intervals of 2000 to 3000 years much more frequently than the 7000 to 10 000 year pacing of massive ice discharges associated with heinrich events the calving cycles correlate with warm cold oscillations called dansgaard oeschger events in greenland ice cores each cycle records synchronous discharges of ice from different sources and the cycles are decoupled from sea surface temperatures these findings point to a mechanism operating within the atmosphere that caused rapid oscillations in air temperatures above greenland and in calving from more than one ice sheet

rock eval tmax suppression documentation and amelioration the rock eval thermal maturation parameter tmax may occasionally be suppressed relative to surrounding rock units this is commonly assumed to result from either a bitumen contribution to the s2 peak or the presence of sulfur rich and hence thermally labile kerogen the phenomenon is frequently coincident with a high natural gamma ray signature and elevated rock eval hydrogen index hi and total organic carbon toc contents determination of thermal maturity of such units relies either on the interpolation of tmax from surrounding units or the direct estimation of the extent of suppression on a given sample the latter may be required if the available samples are restricted to conventional or sidewall core material representative of imited stratigraphic intervals the second white speckled shale part of the cretaceous colorado group in the alberta basin displays tmax suppression over part of its thickness a consistent relationship emerges from calculating a linear regression of tmax as a function of either toc or hi for several wells at different levels of thermal maturity below values of about 453 c late oil window tmax is suppressed by about 1 c for every increase in hi of 50 mg hydrocarbon g toc thus tmax suppression in the second white speckled shale can be corrected by extrapolating all tmax values to a constant hi of 100 to 150 mg hydrocarbon g toc values typical of type iii kerogen

numerical modeling of the global semidiurnal tide in the present day and in the last glacial maximum 1 a hydrodynamic model incorporating a self consistent treatment of ocean self attraction and loading sal and a physically based parameterization of internal tide it drag is used to assess how accurately barotropic tides can be modeled without benefit of data and to explore tidal energetics in the last glacial maximum lgm m2 solutions computed at high resolution with present day bathymetry agree with estimates of elevations from satellite altimetry within 5 cm rms in the open ocean this accuracy and agreement with atlimetric estimates of energy dissipation are achieved only when sal and it drag are included in the model solutions are sensitive to perturbations to bathymetry and inaccuracies in available global databases probably account for much of the remaining error in modeled elevations the 100 m drop in sea level during the lgm results in significant changes in modeled m2 tides with some amplitudes in the north atlantic increasing by factors of 2 or more dissipation is also significantly changed by the drop in sea level if it drag estimated for the modern ocean is assumed dissipation increases by about 50 globally and almost triples in the deep ocean however it drag depends on ocean stratification which is poorly known for the lgm tests with modified it drag suggest that the tendency to a global increase in dissipation is a robust result but details are sensitive to stratification significant uncertainties about paleotides thus remain even in this comparatively simple case where bathymetry is well constrained

shale oil resource potential and oil mobility characteristics of the eocene oligocene shahejie formation jiyang super depression bohai bay basin of china abstract oil mobility in liquid rich shale is crucial for economic success of resource development the characteristics of the host rock and the properties of oil fluids are two primary factors controlling fluid mobility organic geochemistry data allows examination of both resource potential and oil mobility we propose data driven empirical models in this paper to describe hydrocarbon resource potential with respect to oil mobility the proposed methods were applied to a dataset collected from the eocene oligocene es3 and es4 source rock units in four recent shale oil exploration wells in the jiyang super depression of the bohai bay basin the dataset results from standard programmed pyrolysis of whole rock samples as well as solvent extracted replicates of 139 core samples was studied to examine the source rock characteristics and shale oil resource potential bulk geochemical characteristics and thermal decomposition trends allow for sub division of the samples into two groups a samples with high initial hydrogen index 800 mg hc g toc and average present day toc of 4 07 from ly1 and ny1 wells in a distal facies and b samples with slightly lower initial hydrogen index about 700 mg hc g toc and average toc of 3 11 from fy1 and l69 wells in a transitional facies three different categories of oil resource with respect to oil mobility can be defined adsorbed restricted and movable based on organic geochemical characteristics and their variations in the stratigraphic intervals represented by the samples in the four wells we show that expulsion efficiency is a good indicator of hydrocarbon retention in source rock reservoir and that the two wells in the distal facies have higher total resource potentials with abundant movable oil resource than the two wells in the transitional facies the total oil potential is separated into three types of oil resource to show oil mobility thus providing more information for business decision

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds

internal tide generation at the continental shelf modeled using a modal decomposition two dimensional results abstract stratified flow over topography is studied with oceanic applications in mind a model is developed for a fluid with arbitrary vertical stratification and a free surface flowing over three dimensional topography of arbitrary size and steepness with background rotation in the linear hydrostatic regime the model uses an expansion of the flow fields in terms of a set of basis functions which efficiently capture the vertical dependence of the flow the horizontal structure may then be found by solving a set of coupled partial differential equations in two horizontal directions and time subject to simple boundary conditions in some cases these equations may be solved analytically but in general simple numerical procedures are required using this formulation the internal tide generated by a time periodic barotropic tidal flow over a continental shelf and slope is calculated in various idealized configurations the topography and fluid motion are taken to be independent of one coordinate di

expelled oils and their impacts on rock eval data interpretation eocene qianjiang formation in jianghan basin china abstract source rock samples can be contaminated by expelled oils from nearby mature source rocks or from the organic rich laminae within the same source rock units the contaminations on the rock eval samples could produce a false high s1 peak a high production index pi a suppressed tmax and other anomalies identifying the samples affected by expelled oils assessing and correcting the impacts are crucial in source rock study for shale oil shale gas resource evaluation this study analyzes the rock eval 6 results of 43 core samples from two recent shale oil exploration wells of the eocene qianjiang formation a confined source rock unit embedded with salt intervals formed in a hypersaline lacustrine setting in central china the geochemical anomalies of the affected samples are shown through the available samples in this study criteria for identifying the affected samples are discussed and impacts on the conventional rock eval parameters and subsequent estimation of kinetic parameters presented this study provides insights into rock eval data interpretation particularly in source rock evaluation for estimating shale oil resources

organic geochemical characteristics and depositional environment of the tertiary tanjong formation coals in the pinangah area onshore sabah malaysia article i nfo article history the tertiary tanjong formation coals exposed in the west middle block of the pinangah coalfield central part of southern sabah were analyzed and their depositional environments were interpreted the tertiary tanjong coals are humic and generally dominated by vitrinite with significant amounts of liptinite and low amounts of inertinite macerals total organic carbon contents toc of the coals range from 51 2 to 77 7 wt and yield of bitumen values ranging from 57 300 to 140 000 ppm which meet the standard as a source rock with good hydrocarbon generative potential in support good liquid hydrocarbons generation potential can be expected from the tanjong coals based on significant liptinitic content 15 this is supported by their high hydrogen index up to 300 mg hc g toc consistent with type ii and mixed type ii iii kerogens and py gc s2 pyrograms with n alkane alkene doublets extending beyond c30 the coal samples have vitrinite reflectance values in the range of 0 42 0 66 ro indicating immature to early mature stage for hydrocarbon generation these vitrinite reflectance values also indicated that the tanjong coals are with sub bituminous b a and high volatile bituminous c rank tmax values ranging from 419 to 451 c are good agreement with the vitrinite reflectance data this is supported by biomarker maturity parameters as suggested by the c32 homohopane the saturated fraction of the tanjong coals are characterized by dominant odd carbon numbered n alkanes n c23 to n c33 high pr ph ratios 8 18 high tm ts ratios 6 28 and pre dominant of regular sterane c29 all biomarker parameters clearly indicate that the organic matter was de rived from terrestrial inputs and deposited under oxic condition

relative sea level in the western mediterranean basin a regional test of the ice 7g_na vm7 model and a constraint on late holocene antarctic deglaciation abstract the mediterranean basin is a region of special interest in the study of past and present relative sea level evolution given its location south of the ice sheets that covered large fractions of northern europe during the last glaciation the large number of biological geological and archaeological sea level indicators that have been retrieved from its coastal regions as well as its high density of modern coastal infrastructure models of the glacial isostatic adjustment gia process provide reconstructions of past relative sea level evolution and can be tested for validity against past sea level indicators from the region it is demonstrated herein that the latest ice 7g na vm7 model of the gia process the north american component of which was refined using a full suite of geophysical observables is able to reconcile the vast majority of uniformly analyzed relative sea level constraints available for the western part of the mediterranean basin a region to which it was not tuned we also revisit herein the previously published interpretations of relative sea level information obtained from roman era coastal mediterranean fish tanks analyze the far field influence of the rate of late holocene antarctic ice sheet melting history on the exceptionally detailed relative sea level history available from southern tunisia and extend the analysis to complementary constraints on the history of antarctic ice sheet melting available from islands in the equatorial pacific ocean the analyses reported herein provide strong support for the global exportability of the ice 7g na vm7 model a result that speaks directly to the ability of spherically symmetric models of the internal viscoelastic structure to explain globally distributed observations while also identifying isolated regions of remaining misfit which will benefit from further study

self organized criticality of turbulence in strongly stratified mixing layers motivated by the importance of stratified shear flows in geophysical and environmental circumstances we characterize their energetics mixing and spectral behaviour through a series of direct numerical simulations of turbulence generated by holmboe wave instability hwi under various initial conditions we focus on circumstances where the stratification is sufficiently strong so that hwi is the dominant primary instability of the flow our numerical findings demonstrate the emergence of self organized criticality soc that is manifest as an adjustment of an appropriately defined gradient richardson number ri g associated with the horizontally averaged mean flow in such a way that it is continuously attracted towards a critical value of ri g sim 1 4 this self organization occurs through a continuously reinforced localization of the scouring motions i e avalanches that are characteristic of the turbulence induced by the breakdown of holmboe wave instabilities and are developed on the upper and lower flanks of the sharply localized density interface embedded within a much more diffuse shear layer these localized avalanches are also found to exhibit the expected scale invariant characteristics from an energetics perspective the emergence of soc is expressed in the form of a long lived turbulent flow that remains in a quasi equilibrium state for an extended period of time most importantly the irreversible mixing that results from such self organized behaviour appears to be characterized generically by a universal cumulative turbulent flux coefficient of unicode stix x1d6e4 c sim 0 2 only for turbulent flows engendered by holmboe wave instability the existence of this self organized critical state corroborates the original physical arguments associated with self regulation of stratified turbulent flows as involving a kind of equilibrium as described by turner 1973 buoyancy effects in fluids cambridge university press

organic geochemistry and organic petrology of a potential source rock of early eocene age in the beaufort mackenzie basin abstract the biological marker compounds 17 h and 17 h 23 28 bisnorlupane have been identified in a coaly interval at about 3300 3320 m depth within the lower taglu sequence early eocene in the immiugak a 06 well in the beaufort mackenzie basin these biomarkers were previously only known to occur in the lower part of the richards formation and were thus used to infer that the richards was the source for most of the tertiary oils and condensates in the basin the discovery of bisnorlupanes in older much more organic rich rocks indicates that the previous oil source rock correlations may not have been correct and that the coals in the lower taglu sequence are likely the dominant effective source rock especially for the paleocene and early eocene reservoirs in the southern part of the mackenzie delta petrographic and rock eval analyses indicate that the lower taglu sequence coaly section should be mainly a source for gas but with some potential to expel liquids the level of thermal maturity inferred from rock eval tmax 432 438 c equivalent to about 0 65 0 75 ro vitrinite is slightly higher than that inferred from the measured reflectance fluorescence and foraminiferal colouration index which all indicate that the maturity at 3300 m is about 0 60 0 65 ro vitrinite equivalent at the gulf et al immiugak a 06 well site

hydrocarbon evaporative loss from shale core samples as revealed by rock eval and thermal desorption gas chromatography analysis its geochemical and geological implications abstract the s1 peak generated by rock eval analysis of source rock and reservoir interval core and cuttings samples has been routinely employed for in place hydrocarbon resources assessment by petroleum geochemists geologists and even engineers significant evaporative loss of gaseous and light hydrocarbons up to c10 can occur during core and cuttings collection and storage and subsequent sample preparation in the laboratory before instrumental analysis consequently a correction to the s1 values is needed in order to obtain a more accurate estimate of the resources to investigate the effect of evaporative loss on both the amount and the composition of the hydrocarbons retained in shale a time series of rock eval and thermal desorption gas chromatography td gc analyses have been carried out on an organic rich devonian duvernay formation shale core sample from the western canada sedimentary basin wcsb and an organic lean ordovician lotbiniere formation shale core sample from quebec canada the results suggest that the content of total organic carbon toc may play an important role in retaining and preserving light hydrocarbons in sedimentary rocks a total loss of gaseous and light liquid hydrocarbons up to c9 is shown to take place within 21 h of sample preparation for the low toc 11 devonian duvernay shale core sample after 360 h of exposure to the open air the powdered duvernay shale sample shows only 15 decline in its rock eval s1 peak and still contains high relative concentrations of c7 c9 hydrocarbons in addition the evaporative loss of some isomers of c5 c7 hydrocarbons from the organic rich shale is not fully in agreement with their gc retention elution behavior but appears to be partially controlled by their adsorption desorption on the organic matter and mineral matrix this suggests that the c5 c8 gasoline range hydrocarbon parameters should be used with caution for oil oil correlation for unconventional shale and tight petroleum systems while the findings in this study validate the current industrial practice that targets organic rich and mature shale intervals for unconventional shale gas and oil exploration because of their large hydrocarbon storage capacity the results also have an important implication that high toc content may adversely affect the production efficiency of shale and tight hydrocarbon reservoirs due to the strong adsorption of hydrocarbons by the high maturity organic matter

organic petrography and geochemical characterization of the upper cretaceous second white specks and upper belle fourche alloformations west central alberta analysis of local maturity anomalies abstract the second white specks is an enigmatic unconventional shale play in the western canada foreland basin wcfb this play has an inconsistent production performance that has impacted exploration and production risk preventing extensive development in this contribution geochemical properties are studied with the purpose to identify possible geochemical factors that could contribute to the production variability of this unconventional petroleum system the studied succession consists of the second white specks sws and upper belle fourche ubf alloformations which are part of the sws shale play organic petrology and rock eval pyrolysis were combined to characterize the organic matter om and assess om richness thermal maturity and hydrocarbon generation potential in the foredeep section of the basin the results show that the om richness and hydrocarbon generation potential in this area is good and comparison with other studies show that they do not exhibit major lateral variations the kerogen is marine type ii and is dominated by liptinite vitrinite inertinite macerals and solid bitumen alginite and bituminite are the most abundant macerals altered bituminite provides evidence of anaerobic bacteria degradation there is a modest contribution of inertinite that may be responsible for a dilution effect of the pyrolyzable carbon the thermal maturity indicators in this study such as vitrinite reflectance tmax and alginite uv fluorescence color indicate that the controls on thermal maturity and hydrocarbon generation are not well understood there are lateral short scale variations or maturity anomalies that require further investigation to reduce the exploration risk

late precambrian tidal rhythmites in south australia and the history of the earth s rotation sedimentary rhythmites of siltstone and fine sandstone from late precambrian c 650 800 ma glaciogenic formations in south australia are interpreted as distal ebb tidal deposits that record variability in the velocity and range of palaeo ebb tides variations in lamina thickness encode a full spectrum of palaeotidal cycles including semidiurnal diurnal fortnightly and monthly tidal cycles as well as the lunar apsides perigee and nodal cycles a half yearly oscillation is attributable largely to a beat between the fortnightly tidal cycles of luni solar conjunction and lunar declination the lunar nodal cycle is discernible as an amplitude modulation of this beat oscillation the data allow determination of the earth9s palaeorotation and the past dynamics of the earth moon system with an accuracy previously unattainable for the precambrian the late precambrian c 650 ma year contained 13 1 0 5 lunar months and c 400 20 days and the late precambrian lunar month c 30 5 1 5 days these values suggest an average equivalent phase lag near 3 since late precambrian time rather than the present value of 6 the period of 19 5 0 5 years determined for the lunar nodal cycle c 650 ma ago indicates a lunar distance 96 9 1 7 of the present distance the low rate of lunar recession since late precambrian time revealed by the rhythmite data militates against a close approach of the moon during the proterozoic precambrian sedimentary rhythmites may hold a key to the early history of the earth9s rotation

ocean tides and heinrich events climate varied enormously over the most recent ice age1 for example large pulses of ice rafted debris2 originating mainly from the labrador sea3 were deposited into the north atlantic at roughly 7 000 year intervals with global climatic implications3 here we show that ocean tides within the labrador sea were exceptionally large over the period spanning these huge abrupt ice movements which are known as heinrich events we propose that tides played a catalytic role in liberating iceberg armadas during that time

tidal evolution of the northwest european shelf seas from the last glacial maximum to the present 1 two dimensional paleotidal simulations have been undertaken to investigate tidal and tide dependent changes tidal amplitudes tidal current velocities seasonal stratification peak bed stress vectors that have occurred in the nw european shelf seas during the last 20 ka the simulations test the effect of shelf wide isostatic changes of sea level by incorporating results from two different crustal rebound models and the effect of the ocean tide variability by setting open boundary values either fixed to the present state or variable according to the results of a global paleotidal model the use of the different crustal rebound models does not affect the overall changes in tidal patterns but the timing of the changes is sensitive to the local isostatic effects that differ between the models the incorporation of ocean tide changes greatly augments the amplitude of tides and tidal currents in the celtic and malin seas before 10 ka bp and has a large impact on the distribution of seasonally stratified conditions magnitude of peak bed stress vectors and tidal dissipation in the shelf seas the predictions on seasonal stratification are supported by well dated evidence on tidal mixing front migration in the celtic sea additional experiments using the global model suggest that the variability of offshore tides has been caused mainly by changes of eustatic sea level and ice sheet extent in particular a large decrease observed at 10 8 ka bp is attributed to the opening of hudson strait accompanied by the retreat of the laurentide ice sheet

seismic anisotropy and subduction induced mantle fabrics beneath the arabian and nubian plates adjacent to the red sea for most continental areas the mechanisms leading to mantle fabrics responsible for the observed anisotropy remain ambiguous partially due to the lack of sufficient spatial coverage of reliable seismological observations here we report the first joint analysis of shear wave splitting measurements obtained at stations on the arabian and nubian plates adjacent to the red sea more than 1100 pairs of high quality splitting parameters show dominantly n s fast orientations at all 47 stations and larger than normal splitting times beneath the afro arabian dome aad the uniformly n s fast orientations and large splitting times up to 1 5 s are inconsistent with significant contributions from the lithosphere which is about 50 80 km thick beneath the aad and even thinner beneath the red sea the results can best be explained by simple shear between the lithosphere and the asthenosphere associated with northward subduction of the african arabian plates over the past 150 ma

geochemistry of a thermally immature eagle ford group drill core in central texas abstract the upper cretaceous eagle ford group displays significant lateral and vertical geochemical variability much of the work on the eagle ford group has been focused southwest of the san marcos arch to more fully characterize the eagle ford across the entire region a thermally immature drill core was acquired north of the san marcos arch that recovered the pepper shale and the eagle ford group molecular and isotopic analyses of rock extracts were combined with bulk organic and inorganic geochemistry and mineralogy to track the variability in organic matter source and depositional environment as well as to identify drivers of organic enrichment the pepper shale received significant terrigenous organic matter in its distal deltaic or prodeltaic setting compared to the more distally deposited eagle ford group that primarily hosts marine organic matter the upper eagle ford contains two chemofacies the older upper eagle ford chemofacies has similar mineralogy and organic matter to the underlying lower eagle ford and both intervals display good to excellent source rock potential in contrast the younger upper eagle ford chemofacies has a different sterane assemblage a larger terrigenous component and a higher clay mineral abundance however anoxic to euxinic depositional conditions distinguish the lower eagle ford from the upper eagle ford which was deposited under oxic to dysoxic conditions redox chemistry and organic matter source are two important variables that determine source rock quality but they did not change in parallel during eagle ford deposition differences in organic facies explain the tmax variability and depositional redox conditions governed organic richness in the eagle ford group in central texas

dansgaard oeschger oscillations predicted in a comprehensive model of glacial climate a kicked salt oscillator in the atlantic during the period from 60 000 to 35 000 years ago summit greenland ice core records of the oxygen isotopic ratio 18o 16o exhibit intense millennium time scale oscillations these dansgaard oeschger oscillations have been interpreted to represent the variations in north atlantic air temperature caused by correlative changes in the strength of north atlantic deep water production we apply a comprehensive model of glacial climate to unambiguously identify the mechanism responsible for this phenomenon this is shown to involve a salt oscillation of relaxation oscillator form this nonlinear oscillation does not require the existence of feedback due to freshwater release from grounded ice on the continents during the warm phase of the cycle

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

suppression of thermal maturity indicators in lacustrine source rocks a case study of dongying depression eastern china abstract the paleogene shahejie formation of the dongying depression in eastern china is a unique region and can offer insights into the suppression of thermal maturity in a large set of successive lacustrine shales this study focuses on the paleogene shahejie formation of n 38 well in the dongying depression the unusual distribution of thermal maturity indicators such as vitrinite reflectance vro and c29 sterane thermal parameters was investigated through geochemical analysis the research interval 2770 3376 m was divided into three parts the upper part of es32 2770 2990 m the lower part of es32 2990 3190 m and the es31 3190 3376 m the es31 mainly contained organic matter type i and some type ii which included mostly good and excellent source rocks meanwhile the upper es32 mainly contained organic matter type iii which included mostly poor and moderate source rocks the parameters g c30h c35h c31 35h c31m c31h c29 20s 20s 20r c31 22s 22s 22r and c32 22s 22s 22r showed a different distribution corresponding to the different lake sedimentary environments various organic facies were developed at the different evolution stages of the lake basin which showed a noticeable influence on the parameters the thermal maturity indicator vro and molecular thermal parameters such as c29 20s 20s 20r c31 22s 22s 22r c32 22s 22s 22r and c31m c31h presented abnormal distributions in the large set of lacustrine shales especially in the es31 this observation suggested suppression of several thermal maturity indicators vro suppression positively correlated well with the corrected hydrogen index and alginite content in maceral composition the high content of alginite group was considered to be the primary reason behind the evident negative vro anomaly

space geodesy constrains ice age terminal deglaciation the global ice 6g_c vm5a model a new model of the last deglaciation event of the late quaternary ice age is here described and denoted as ice 6g c vm5a it differs from previously published models in this sequence in that it has been explicitly refined by applying all of the available global positioning system gps measurements of vertical motion of the crust that may be brought to bear to constrain the thickness of local ice cover as well as the timing of its removal additional space geodetic constraints have also been applied to specify the reference frame within which the gps data are described the focus of the paper is upon the three main regions of last glacial maximum ice cover namely north america northwestern europe eurasia and antarctica although greenland and the british isles will also be included if peripherally in the discussion in each of the three major regions the model predictions of the time rate of change of the gravitational field are also compared to that being measured by the gravity recovery and climate experiment satellites as an independent means of verifying the improvement of the model achieved by applying the gps constraints several aspects of the global characteristics of this new model are also discussed including the nature of relative sea level history predictions at far field locations in particular the caribbean island of barbados from which especially high quality records of postglacial sea level change are available but which records were not employed in the development of the model although ice 6g c vm5a is a significant improvement insofar as the most recently available gps observations are concerned comparison of model predictions with such far field relative sea level histories enables us to identify a series of additional improvements that should follow from a further stage of model iteration

sea level and deep water temperature changes derived from benthic foraminifera isotopic records we show that robust regressions can be established between relative sea level rsl data and benthic foraminifera oxygen isotopic ratios from the north atlantic and equatorial pacific ocean over the last climatic cycle we then apply these regressions to long benthic isotopic records retrieved at one north atlantic and one equatorial pacific site to build a composite rsl curve as well as the associated confidence interval over the last four climatic cycles our proposed reconstruction of rsl is in good agreement with the sparse rsl data available prior to the last climatic cycle we compute bottom water temperature changes at the two sites and at one southern indian ocean site taking into account potential variations in north atlantic local deep water 18o our results indicate that a last glacial maximum lgm enrichment of the ocean mean oxygen isotopic ratio of 0 95 is the lowest value compatible with unfrozen deep waters in the southern indian ocean if local deep water 18o did not increase during glacials with respect to present such a value of the lgm mean ocean isotopic enrichment would impose a maximum decrease in local bottom water 18o at the north atlantic site of 0 30 during glacials

the abrupt termination of the younger dryas climate event previous studies on two deep greenland ice cores have shown that a long series of climate oscillations characterized the late weichselian glaciation in the north atlantic region1 and that the last glacial cold period the younger dryas ended abruptly 10 700 years ago2 here we further focus on this epoch defining event and present detailed heavy isotope and dust concentration profiles which suggest that in less than 20 years the climate in the north atlantic region turned into a milder and less stormy regime as a consequence of a rapid retreat of the sea ice cover a warming of 7 c in south greenland was completed in about 50 years

critical considerations when assessing hydrocarbon plays using rock eval pyrolysis and organic petrology data data quality revisited abstract the dramatic increase in exploration for unconventional hydrocarbon resources has inherently fuelled the need for new source rock geochemical data the need for new data comes along with an increasing number of new users many of whom do not possess the background to interpret accurately and evaluate the quality of data sets generated by different geochemical screening techniques e g rock eval pyrolysis vitrinite reflectance here datasets from rock eval pyrolysis vitrinite reflectance and leco toc analyses are scrutinized and compared to show how failing to recognize good vs bad datasets can dramatically change interpretations during prospect or play appraisals detector saturation contamination of the sample with drilling fluid and suppression of both tmax and vitrinite reflectance are examples of complications that could compromise the validity of the results and the play or prospect reviews derived from them in addition misconceptions such as leco toc is better than rock eval 6 toc expressed by many users are a consequence of the lack of understanding of how different screening techniques and instrumentation work a solid understanding of these pitfalls and limitations can provide inexperienced geoscientists and engineers with the required support to improve risk maps for hydrocarbon charge analysis and source rock evaluations when using classic guidelines for interpreting results

on the resonance and influence of the tides in ungava bay and hudson strait 1 the tides of leaf basin in ungava bay may be the world s highest an analysis of the frequency dependence of the response to outside forcing a normal mode analysis and a study of the damped oscillation of an initial disturbance suggest that the ungava bay hudson strait region has a natural period of about 12 7 hours and so is close to resonance with the tidal forcing the implications for regional and global tides in the present past and future are explored

greenland ice core studies abstract greenland deep ice cores represent continuous sequences of deposits spanning the last up to several hundred thousand years isotopes and impurities in the ice reveal a broad spectrum of information on past environmental conditions in the north atlantic region for example climatic changes in terms of surface temperature and annual precipitation turbidity and chemical composition of the atmosphere including its co 2 concentration volcanic activity and its climatic impact and cosmic radiation flux changes in the past one of the fundamental parameters in ice core studies is the isotopic composition of the ice for example the 18 o concentration on the relative scale which varies in phase with the temperature of snow formation the seasonal variations allow identification of annual layers in the core and hence absolute dating back to at least 8000 yrs b p with some reservations smoothed records may be interpreted in terms of climatic temperature changes cp fig 1 which shows profiles along two deep ice cores from dye 3 southeast greenland and camp century northwest greenland the latter spans all of the last glaciation and the preceding interglacial eem the time scale in units of 10 3 yrs b p has been derived by comparison of the most predominant features with their analogues in sea sediment cores dansgaard et al 1982 the dramatic shifts in times of full glacial severity seem to recur with a quasi periodicity of 2550 yrs perhaps caused by abrupt changes of the north atlantic sea ice cover spectral data analysis by the maximum entropy method shows similar but greatly damped oscillations in the well dated post glacial part of the camp century record in antiphase with independent estimates on world wide degree of glaciation dansgaard et al 1984 figure 2 left shows the deepest 340 m of the dye 3 profile plotted on a linear depth scale the very deepest 25 m of ice is silty and the s are higher than in holocene ice indicating a time of deposition with unusually high temperature of formation probably the eemian interglacial however the record is hardly continuous that far back in time fig 2 middle shows some of the oscillations in detail and fig 2 right gives further details of three representative shifts along with a dust concentration profile increasing towards left the dust is probably brought to greenland mainly from distant areas covered by loss the dust content changes less abrupt than and not at exactly the same depth which indicates that the measured shifts are not due to temporal discontinuities in the ice core the general antiphase between dust content and suggests higher storminess in times of lower s the circles are co 2 concentrations in air inclusions in the ice but it is still doubtful if they can be interpreted in terms of past atmospheric co 2 concentrations hammer et al 1980 great volcanic eruptions inject acid gases into the stratosphere particularly sulphuric gases which are spread all over the hemisphere under oxydation the strong acids re enter the troposphere and are subsequently washed out by precipitation causing acid layers in the ice sheets hence acidity profiles along the holocene part of the ice cores reveal violent volcanic activity in the northern hemisphere and comparison with the profiles suggest a substantial cooling impact on the climate hammer et al 1980

black shale xenolith in a jurassic cretaceous kimberlite and organic rich upper ordovician shale on baffin island canada a comparison of their organic matter abstract rock eval pyrolysis and molecular organic geochemical analyses as well as organic petrographic observations were carried out on a rare black shale xenolith core drilled from a late jurassic early cretaceous kimberlite on the hall peninsula in southern baffin island canada the results are compared with those of outcrop shale samples from the upper ordovician amadjuak formation the only organic rich shale deposit discovered so far in the region the shale xenolith is found to be organic rich and thermally mature at the stage of peak oil generation and contain type ii organic matter similar to that of the immature amadjuak shale discounting the differing thermal maturation effect similar depositional environments and original organic inputs are suggested for both the shale xenolith and the upper ordovician shale based on their bulk molecular and isotopic signatures as well as organic maceral assemblages the present study cannot exclude the possibility of the shale xenolith being originated from an organic rich lower silurian deposit as suggested by previous re os isotope dating study it is clear however that depending on their areal distribution and thickness the lithostratigraphic unit from which the organic rich black shale xenolith is derived would make an excellent petroleum source rock in the study area

depositional environment and hydrocarbon source potential of the permian gondwana coals from the barapukuria basin northwest bangladesh article barapukuria coal basin is situated in dinajpur district of the northwestern part of bangladesh a total of eight coal samples have been collected from two different locations of the basin and analyzed using organic geo chemical and organic petrological methods the extracted organic matter of the studied samples is a mixture of type iii and type ii kerogen as evaluated by the source rock analyzer sra and pygc pyrograms the measured total organic carbon toc ranges from 61 to 74 wt and the recovered extractable organic matter eom varies from 27 561 to 41 389 ppm these results suggest that the coals are ranked as good quality source rock the hydrocarbon yield has been calculated which is also high and it ranges from 12 192 to 20 799 ppm the organic matter is thermally mature for hydrocarbon generation considering their tmax and measured mean vitrinite reflec tance values of 431 to 435 c and 0 72 to 0 81 ro respectively the hopane 22s 22s 22r moretane hopane ratio and sterane parameters are also in support of these thermal maturity assessment

model assisted rock eval data interpretation for source rock evaluation examples from producing and potential shale gas resource plays abstract rock eval pyrolysis has been widely accepted by the petroleum industry as a useful technique for a quick easy and cost effective source rock evaluation however there are misconceptions and misuse of some of the existing rock eval parameters due to implicit underlying assumptions or poor understanding of the limitations which could lead to erroneous conclusions data interpretation from a perspective of hydrocarbon generation kinetics may facilitate better interpretation of the hydrocarbon generation capacity of a source rock from its thermal stability and transformational behaviors we present a model assisted approach for data interpretation from which data scatters can be viewed not only for the remaining petroleum generation potential of individual samples but also for data specific thermal decomposition path as a whole to verify whether the data come from a single kerogen population with similar kinetics and associated generation potentials moreover we propose a concept of dimensionless toc and s2 variables that effectively removes the thermal maturity overprint in the traditional toc vs s2 plot used for the determination of the kerogen type the dimensionless variables are defined by rescaling the parameters against their original values before thermal decomposition on a dimensionless plot data points from the same genetic population of source rocks align on a single line regardless of their thermal maturation levels this article demonstrates the methods and the proposed approaches for studying oil generation kinetics and resource potential using traditional rock eval data through examples from selected producing and potential shale gas plays in canadian sedimentary basins and elsewhere

a fluorescence alteration of multiple macerals famm study of netherlands coals with normal and deviating vitrinite reflectance abstract suites of well characterised westphalian coals from the netherlands with normal and deviating vitrinite reflectance have been examined by the famm fluorescence alteration of multiple macerals technique the fluorescence alteration characteristics of the normal netherlands coals change with rank in a similar manner to normal australian permian coals except that the telovitrinites of the netherlands coals appear to be relatively more perhydrous this difference is also apparent in a comparison of rock eval hydrogen index values a fluorescence alteration diagram has been calibrated for the netherlands carboniferous from which accurate equivalent vitrinite reflectance values can be obtained as well as suppression corrections for measured vitrinite reflectances however the errors in using the equivalent australian permian diagram for the determination of the suppression correction are small 0 05 absolute the well hengevelde 1 is used as an example to illustrate how corrections may be made to perhydrous samples with deviating vitrinite reflectance for maturation assessment in petroleum exploration

interpretation of vitrinite reflectance depth profiles in the northern denison trough bowen basin australia abstract the denison trough bowen basin australia is a mature hydrocarbon province that contains permian to triassic coal and gas bearing sediments deposited in deltaic to shallow marine shelf conditions the sandstone reservoirs of the permian aldebaran sandstone freitag formation and catherine sandstone of the northern denison trough ndt were evaluated for their co2 storage potential as part of the queensland government s zerogen co2 capture and storage project which found that diagenetic processes acting on the sandstones have resulted in poor permeability and reduced porosity making them unsuitable for large scale injection and storage in this area to better understand the factors acting to degrade these reservoirs the purpose of the current study was to establish a thermal maturity framework for the permian sandstone reservoirs of the northern denison trough based on vitrinite reflectance measurements of coals and rock eval analysis of coals and shales from the aldebaran sandstone through to the catherine sandstone mean maximum vitrinite reflectance of coals rmax ranges from 0 55 to 0 93 and estimated maximum burial temperatures calculated from vitrinite reflectance fall between 83 oc 125 oc calculation of palaeotemperatures from vitrinite reflectance data has been hampered by inversions of depth reflectance profiles at the top of the aldebaran sandstone and scatter in vitrinite reflectance data this has been attributed to depositional effects including the major marine flooding surfaces at the top of the aldebaran sandstone that have affected vitrinite reflectance evolution in the ndt producing low reflecting fluorescing perhydrous vitrinite near marine flooding surfaces and subhydrous vitrinite when oxidising conditions prevailed a vitrinite reflectance difference of up to 0 2 rmax is detected in an isometamorphic coal an equivalent palaeotemperature difference of approximately 19 oc the abundance of perhydrous vitrinite has resulted in largely suppressed vitrinite reflectance throughout the examined permian interval in the northern denison trough and the presence of both perhydrous and subhydrous vitrinite introduces an error in palaeotemperature calculation in high volatile bituminous coals rock eval analysis provides supporting and calibrating maturity data tmax over the studied interval ranges from 421 oc to 447 oc generating a positive broadly linear correlation between rmax and tmax that is applicable specifically to the ndt tmax suppression was also detected in perhydrous coals hydrogen index serves to evaluate the level of vitrinite reflectance suppression through an inverse relationship between the two parameters the rock eval data confirms the oil generation potential of coals in the ndt while shales associated with the same stratigraphic intervals have lower hydrocarbon generation potential this study brings new insights into the thermal maturity framework in the ndt and highlights the importance of reliable vitrinite reflectance data for calculation of maximum burial temperatures particularly in underexplored or frontier areas

influence of paleoenvironmental conditions on distribution and relative abundance of saturated and aromatic hydrocarbons in sediments from the nw part of the toplica basin serbia abstract the investigation of the relationship between paleoenvironmental conditions and distribution and relative abundance of specific saturated and aromatic hydrocarbons was the main objective of this study thus marking the parameters which were most sensitive to environmental changes insights on the type generative potential and maturity of organic matter om as well as paleoclimate conditions along with the reconstruction of depositional settings of the northwest part of the toplica basin serbia were provided organic petrographic palynofacies organic geochemical mineralogical and xrf analyses were carried out to investigate 40 sediment samples of the prebreza and cucale sedimentary units investigated samples were deposited in the saline and anoxic environment under semi arid to semi humid humid climate conditions along with the constant inflow of volcanoclastic material the predominance of methyltrimethyltridecil chroman mttc within euxinic portions of the stratified water column was associated with an increase in salinity which was noticed for sediments of the prebreza unit sediments from this stratigraphic unit showed a higher contribution of algae precursor whereas sediments of the cucale unit suggested higher participation of microbiologically reworked om most of the samples contained oil prone kerogen type ii maturity of the om for sediments of the prebreza unit ranged from immature to early mature while for samples of the cucale unit varied from early mature to mature stages distribution of hopane biomarkers typical for crude oil indicated that depth of 1 km was a boundary for the genesis of thermodynamic more stable compounds a significant portion of semifusinite was correlated with the paleofire event which affected the distribution of n alkanes the high production of hydrocarbons was related to volcanic activity parameters which proved to be highly susceptible at the stratigraphic boundary between the prebreza and cucale units were c value s h mttc mttc mttc and 1 3 1 6 1 4 1 5 dmc respectively

anatomy of heinrich layer 1 and its role in the last deglaciation this research used data acquired at the xrf core scanner lab at the marum center for marine environmental sciences university of bremen germany this research used samples provided by the international ocean discovery program iodp funding for this research was provided by the uk natural environmental research council nerc to hodell the nerc radiocarbon facility supported two radiocarbon dates and wally broecker generously supported the remainder with funding from the comer family foundation research by rodriguez tovar and dorador was financed by project cgl2015 66835 p b m acknowledges support from the csic ramon y cajal postdoctoral programme ryc 2013 14073 j f e would like to acknowledge funding under erc advanced grant 320750 nanopaleomagnetism

the accuracy of surface elevations in forward global barotropic and baroclinic tide models abstract this paper examines the accuracy of surface elevations in a forward global numerical model of 10 tidal constituents both one layer and two layer simulations are performed as far as the authors are aware the two layer simulations and the simulations in a companion paper deep sea research ii 51 2004 3043 represent the first published global numerical solutions for baroclinic tides self consistent forward solutions for the global tide are achieved with a convergent iteration procedure for the self attraction and loading term energies are too large and elevation accuracies are poor unless substantial abyssal drag is present reasonably accurate tidal elevations can be obtained with a spatially uniform bulk drag c d or horizontal viscosity k h but only if these are inordinately large more plausible schemes concentrate drag over rough topography the topographic drag scheme used here is based on an exact analytical solution for arbitrary small amplitude terrain and supplemented by dimensional analysis to account for drag due to flow splitting and low level turbulence as well as that due to breaking of radiating waves the scheme is augmented by a multiplicative factor tuned to minimize elevation discrepancies with respect to the topex poseidon t p constrained got99 2 model the multiplicative factor may account for undersampled small spatial scales in bathymetric datasets an optimally tuned multi constituent one layer simulation has an rms elevation discrepancy of 9 54 cm with respect to got99 2 in waters deeper than 1000 m and over latitudes covered by t p 66 n to 66 s the surface elevation discrepancy decreases to 8 90 cm 92 percent of the height variance captured in the optimally tuned two layer solution the improvement in accuracy is not due to the direct surface elevation signature of internal tides which is of small amplitude but to a shift in the barotropic tide induced by baroclinicity elevations are also more accurate in the two layer model when pelagic tide gauges are used as the benchmark and when the t p constrained tpxo6 2 model is used as a benchmark in deep waters south of 66 s for antarctic diurnal tides the improvement in forward model elevation accuracy with baroclinicity is substantial the optimal multiplicative factor in the two layer case is nearly the same as in the one layer case against initial expectations that the explicit resolution of low mode conversion would allow less parameterized drag in the optimally tuned two layer m 2 solution local values of the ratio of temporally averaged squared upper layer speed to squared lower layer speed often exceed 10

a dual porosity model for evaluating petroleum resource potential in unconventional tight shale plays with application to utica shale quebec canada unconventional tight to shale reservoirs vary from tight sandstone siltstone to organic rich mudstone shale commonly with mixed lithologies in such reservoir systems matrix pores and organic pores with different origins and distinct physical and chemical properties co exist for hydrocarbon storage traditional resource assessment methods designed for conventional reservoirs cannot handle the two pore systems properly this study proposes a dual porosity model to respond to the need for a new method in assessing hydrocarbon resource potential in such reservoir systems the dual porosity model treats the two types of pores separately and derives the resource estimates from different sources of data thus better characterizing unconventional reservoirs with complicated pore systems the new method also has the flexibility of assessing resource potential for the entire spectrum of mixed lithologies ranging from a complete tight to a pure source rock organic rich shale mudstone reservoir the proposed method is illustrated through the assessment of the in place petroleum resource potential in the upper ordovician utica shale of southern quebec canada the results of the application suggest that the proposed approach effectively handles the two pore systems in tight shale reservoirs effectively and provides a useful tool for estimating resource potential in unconventional plays

kerogen asphaltene sulfur relationships in sulfur rich monterey oils abstract monterey oils in the santa maria basin onshore and offshore are generally low maturity oils because of low thermal exposure relatively shallow burial for short times they are generated as heavy high sulfur oils because of the composition of the unusual type ii source kerogens which are exceptionally rich in organic sulfur 8 14 these high sulfur kerogens which we designate type ii s appear to generate oil at significantly lower thermal exposures than ordinary type ii kerogens with less than 6 s in contrast to common type ii kerogens which generate oil largely by cleavage at oxygen bridge groups and carbon carbon bonds eliminating co2 h2o and hydrocarbon fragments type ii s kerogens have an additional complement of weak bonds associated with bound sulfur the preferential cleavage at weak sulfur linkages tends to produce larger fragments leading to high initial amounts of asphaltenes resins and sulfur rich aromatics together with smaller amounts of saturated hydrocarbons elemental analyses of monterey kerogens and asphaltenes clearly support the concept that the asphaltenes are essentially fragments of kerogen cleaved sufficiently to be soluble or peptized in this heavy oil system solubilization of asphaltenes is attributed to their interactions with the abundant resins and aromatics this sysstem is sufficiently stable under source and reservoir conditions to allow expulsion and migration for reasonable distance without significant fractionation or changes in gross properties initial asphaltenes have essentially the same atomic h c ratios as the source kerogen but have significantlyy lower o c ratios and slightly lower s c ratios the n c ratios are nearly the same for kerogens and their derived asphaltenes with increasing maturity the h c ratios in asphaltenes decrease much like maturation changes in kerogen the s c ratio also decreases significantly however the o c ratios initially low in asphaltenes and n c ratios increase slightly due to material balance caused by other losses these element composition and atomic ratio relationships allow some important inferences concerning source kerogen composition from analysis of asphaltenes alone this can be useful when potential source rock samples are not available for analysis and or when a choice between alternate source rock possibilities must be made

improving spatial predictability of petroleum resources within the central tertiary basin spitsbergen a geochemical and petrographic study of coals from the eastern and western coalfields central tertiary basin ctb coals from a variety of palaeogeographic conditions within the longyear and verkhnij seams were sampled to assess the relationship between the petroleum present the remaining generation potential and coal geochemistry in order to improve the spatial predictability of petroleum resources within the basin vitrinite reflectance vr values from the ctb coals have been shown to be suppressed marshall et al 2015b this study attempts to quantify and correct for this suppression effect by applying the lo 1993 method lovr which uses hydrogen index hi values to modify vr data and the coal rank sr scale of suggate 2000 2002 a technique not affected by suppression in addition the oil generation and expulsion thresholds for the ctb coals were investigated with discussions on oil potential versus marine influence upon the mires in which the coals formed a pseudo van krevelen diagram shows that the majority of the coals plot on the type ii kerogen line while the remainder plot between the types ii and iii kerogen lines with hi between 151 and 410 mg hc g toc however maceral analysis shows that type iii kerogen predominates this is attributed to the presence of abundant fluorescing oil prone vitrinites the lovr tmax and rank sr parameters all show that maturity increases from basin margins towards basin centre i e from bassen to lunckefjellet to breinosa and colesdalen and indicate that all the coals are within the oil generation window the marginal samples at bassen are within the early mature stage of the oil window i e 0 7 ro meaning the threshold for oil generation in the basin could not be clearly defined however the observed maturation trend somewhat parallels the maturation pathway of the new zealand coal band nz coal band and the envelope of the sykes and snowdon 2002 nz coal data set therefore it is considered that the oil generation threshold for the ctb coals is likely at rank sr 9 10 tmax 420 430 c in line with the observed rise in bitumen index bi some of the lunckefjellet coals and all the breinosa and colesdalen coals have either reached or progressed beyond the threshold for oil expulsion as indicated by the peak in hi at rank sr 11 12 lovr 0 75 0 85 ro tmax 430 440 c the peak in bi at rank sr 12 5 13 5 suggests that some of the lunckefjellet and breinosa coals and all the colesdalen coals have reached the effective oil window total sulphur st contents range between 0 46 and 12 05 indicating non marine to strong marine influence upon precursor peats with st contents of the longyear seam appearing to record instances of coastal retreat associated with base level rise marine deposition seems to significantly control the distribution of oil prone coals within seams and across the ctb the levels of marine influence as indicated by st content show clear positive relationships between bi and hi within the bassen samples because they have not started expelling oil conversely the levels of marine influence show clear negative relationships with bi and hi within the colesdalen samples because they have commenced oil expulsion and probably reached the effective oil window the more marine influenced coals appear to have commenced petroleum generation relatively earlier which is a plausible explanation why the coals from the lunckefjellet locality appear to be at different stages within the oil window

a mathematical representation of rock eval hydrogen index vs tmax profiles abstract different types of kerogens have different maturation paths on rock eval hydrogen index hi vs t max plots an equation hi 1 a exp b t max 435 c where a b and c are constants can be used to define hi t max profiles of particular source rock units the constants a b and c characterise the particular kerogen and also allow expression of its transformation ratio tr as a function of the t max by an equation tr hi 0 a exp b t max 435 hi 0 a exp b t max 435 1 where hi 0 1 c the hi t max equation constants were determined by nonlinear curve fitting for three standard type i ii and iii kerogens and for two geological sections second white speckled 2ws formation alberta basin and a source rock unit of cambay basin india high correlation coefficients for the fitted equations for four hi t max data sets of four groups of the 2ws samples segregated using oxygen index oi vs t max cross plot and for one data set of the cambay basin source rock unit show the validity of the proposed hi t max equation comparison of the calculated tr and measured production index pi values for the 2ws samples allow identification of samples that have expelled generated hydrocarbons and samples that contain unexpelled generated hydrocarbons for the cambay basin example where rock eval data of silty and sandy samples were screened out a reasonable match exists between the calculated trs and measured production index values up to a t max value of 445 c indicating onset of oil expulsion the proposed hi t max equation can thus characterise organic matter in a source rock unit with respect to its original generation potential and hydrocarbon generation threshold and rate it may also help to identify the effective source sections that have expelled generated hydrocarbons from several potential source rocks if present in a basin

a data driven model for studying kerogen kinetics with application examples from canadian sedimentary basins abstract source rock is an essential element in unconventional resource play evaluation while kerogen kinetics is one of the most important components in source rock evaluation traditional approach for determining oil generation kinetics is done through laboratory pyrolysis analysis by mimicking the hydrocarbon generation processes with variable accelerated heating rates thus the thermal energy required for hydrocarbon generation under geological conditions is inferred study suggests that for a given kerogen type numerical kinetic models derived from a limited number of laboratory tests may result in unacceptable errors because of under representation of variation in activation energy related to organic facies change and source rock heterogeneity as economic margin of developing an unconventional resource play can be small business success often depends on early identification of favourable area a quick and robust method for resource play evaluation is critical this study proposes a data driven statistical approach that utilizes existing rock eval toc data by fitting the measured hydrogen index and tmax to an exponential model the model is designed so that all parameters have an explicit physical meaning and the ranges of parameter values are predictable once the empirical statistical model is established hydrocarbon transformation ratio can be calculated to represent the hydrocarbon generation kinetics of the source rock the main advantage of the proposed approach is the utilization of widely available rock eval datasets so that 1 no additional specifically designed laboratory pyrolysis experiments are required 2 the uncertainty due to facies variation or source rock heterogeneity nature and poor data quality human can be quantified through the statistical analysis of a large dataset and 3 validation for temperature and geothermal rates in situ pressure and other environmental conditions is not necessary as the input data for the model are all based on naturally matured samples rock eval datasets from four well known canadian source rock intervals representing the most common kerogen types are tested and used as examples to demonstrate the application of the proposed method the examined source rocks with different kerogen types show distinct kinetic behaviours and this is consistent with models derived from laboratory tests applications also indicate that the proposed method appears to be robust and convenient for modelling kerogen kinetics from rock eval data directly

organic facies and thermal maturity of late aptian to early cenomanian shelf deposits northern sinai egypt abstract organic petrologic and geochemical investigations were carried out on late aptian to early cenomanian mid cretaceous sediments recovered from the paleoshelf of the northern sinai egypt the organic facies and thermal maturity of sedimentary organic matter were evaluated with regard to maximum burial depth results from organic geochemical analyses c org n tot rock eval pyrolysis performed on kerogen concentrates indicate the dominance of hydrogen depleted organic matter of either terrestrial or degraded marine origin kerogen typing reveals a mixture of type iii and iv maceral analyses conducted on concentrates support geochemical results showing variable proportions of vitrinite migrabitumen graphite and traces of inertinite vitrinite and inertinite are considered to be of autochthonous or parautochthonous origin indicating at least partly humid paleoclimatic conditions in the hinterland this assumption is also supported by the occurrence of graphite which points to aquatic transport from the southerly exposed precambrian basement the presence of migrabitumen presumably relates to migrated hydrocarbons from underlying organic carbon rich jurassic strata the organic facies of mid cretaceous deposits from the northern sinai indicates a proximal fluvio deltaic or oxic shelf environment equivalent to organic facies types c d according to jones jones r w 1987 organic facies in brooks j welte d h eds advances in petroleum geochemistry academic press london pp 1 80 t max data obtained from rock eval pyrolysis reveal an immature level for organic matter 350 c to 425 c although these values are probably depressed due to the presence of migrabitumen since vitrinite is very scarce in kerogen concentrates reflectance measurements were also performed on migrabitumen the best correlation of both types of reflectance data was obtained when migrabitumen data were corrected following the approach of jacob jacob h 1989 classification structure genesis and practical importance of natural solid oil bitumen int j coal geology 11 pp 65 79 reflectance values range between 0 6 to 0 7 rm equivalent to high volatile bituminous coalification stages since there is no indication for an abnormal geothermal gradient along the ne african margin a maximum burial depth between 1 2 km and 2 0 km is estimated for the mid cretaceous strata of the northern sinai

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

heat flow and thermal maturity modelling in the northern carnarvon basin north west shelf australia abstract the northern carnarvon basin is located at the southern end of the north west shelf of australia it was developed by rifting during the jurassic earliest cretaceous heat flow and thermal maturity in seven wells from three sub basins rankin platform and exmouth plateau of the northern carnarvon basin were modelled using basinmod 1d program multiple thermal maturity parameters were used to constrain the influence of anomalously low vitrinite reflectance those t max data with reliable quality can be applied to correlate with vitrinite reflectance establish thermal maturity and calibrate the modelled results the modelled results indicated that the measured maturity data in some wells were consistent with the rift heat flow model jarvis mckenzie associated with the jurassic rift and the earliest cretaceous seafloor spreading events the maximum values of heat flow were in the range from 67 mw m 2 jurabi 1 to 105 mw m 2 bowers 1 in the exmouth and barrow sub basins on the exmouth plateau the maximum values of heat flow were modelled to be 72 mw m 2 in the jupiter 1 well and 78 mw m 2 in the investigator 1 well these maximum values were modelled to occur during syn rift phase which were 29 88 and 33 37 greater than their current heat flow values in the sub basins and on the exmouth plateau respectively this study suggests that maturity indicators are less diagnostic of rifting thermal histories if the maximum thermal effect is associated with cretaceous and cainozoic burial in this basin

trends in thermal maturity indicators for the organic sulfur rich eagle ford shale abstract thermal maturity is critical to evaluate petroleum systems and to interpret biomarker results for paleoenvironmental and geobiology studies many thermal maturity indices were developed for marine source rocks containing type ii kerogen but their behavior in organic sulfur rich source rocks requires more investigation here we present geochemical analyses of whole and extracted rock isolated kerogen and extractable organic matter across a natural thermal maturity sequence of the upper cretaceous eagle ford shale to evaluate the behavior of maturity parameters in organic sulfur rich source rocks the samples have similar mineralogy and trace element composition minimizing potential facies effects on thermal maturity parameters atomic h c ratios of isolated kerogen extractable organic matter yield and programmed pyrolysis results show that the samples range from the pre oil through dry gas generation windows programmed pyrolysis data and kerogen elemental ratios show that the immature samples host both type iis atomic sorg c 0 04 and sulfur rich type ii kerogen kerogen sorg c 0 03 0 04 while samples with lower kerogen sorg c ratios kerogen sorg c

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

two case studies of thermal maturity and thermal modelling within the overpressured jurassic rocks of the barrow sub basin north west shelf of australia abstract thermal maturity within the jurassic thick overpressured source rocks of the bambra 2 and barrow deep 1 wells barrow sub basin western australia was investigated and modelled using a temperature time related kinetic model the aim of this study is to investigate whether overpressure has a determinable influence on thermal maturation repeat formation tests rfts drill stem tests dsts and mud weights indicate that the jurassic section in the barrow sub basin is highly overpressured it appears that the overpressured zone is associated with high sonic transit times and low resistivity values in the jurassic fine grained rocks anomalously low measured vitrinite reflectance r o values in the overpressured zone appear to be due to either r o suppression or inaccurate identification of vitrinite anomalously low t max values are found to be caused by contamination from drilling mud additives a good correlation is found between the reliable maturity data including biomarker maturity and predicted maturity values r o between 0 8 and 2 2 and suggests that the anomalously low r o and t max values are probably not related to the overpressuring fluid pressure about 40 80 mpa at 3000 4600 m these results demonstrate that the true maturity level in the jurassic overpressured section probably depends on temperature and time alone we therefore conclude that overpressure is not an important factor in thermal maturity and hydrocarbon generation in this region

liquid hydrocarbon generation potential from tertiary nyalau formation coals in the onshore sarawak eastern malaysia tertiary coals exposed in the north central part of onshore sarawak are evaluated and their depositional environments are interpreted total organic carbon contents toc of the coals range from 58 1 to 80 9 wt and yield hydrogen index values ranging from 282 to 510 mg hc g toc with low oxygen index values consistent with type ii and mixed type ii iii kerogens the coal samples have vitrinite reflectance values in the range of 0 47 0 67 ro indicating immature to early mature initial oil window t max values range from 428 to 436 c which are good in agreement with vitrinite reflectance data the tertiary coals are humic and generally dominated by vitrinite with significant amounts of liptinite and low amounts of inertinite macerals good liquid hydrocarbons generation potential can be expected from the coals with rich liptinitic content 35 this is supported by their high hydrogen index of up to 300 mg hc g toc and py gc s 2 pyrograms with n alkane alkene doublets extending beyond c30 the tertiary coals are characterised by dominant odd carbon numbered n alkanes n c23 to n c33 high pr ph ratio 6 8 high t m t s ratio 8 16 and predominant regular sterane c29 all biomarkers parameters clearly indicate that the organic matter was derived from terrestrial inputs and the deposited under oxic condition

last glacial maximum ice sheet impacts on north atlantic climate variability the importance of the sea ice lid 1 last glacial maximum lgm ice 5g vm2 ice 6g vm5a and paleoclimate modelling intercomparison project phase 3 ice sheet reconstructions are employed in high resolution coupled climate model simulations to investigate the changes they induce in north atlantic climate variability an initial ice 5g vm2 experiment develops a rapid increase of sea ice extent once a thermal threshold is exceeded in this multimillennial simulation subpolar sea ice concentration and thickness are found to be strongly impacted by topographically induced downstream thermal effects from the laurentide ice sheet in each of the reconstructions however in the two additional lgm perturbation experiments the modeled changes in sea ice area are sufficiently similar to the lgm ice 5g vm2 experiment to lead to an equilibrium atlantic meridional overturning circulation strength that is also reduced by the same 40 from preindustrial even though we find significant variation among the models in the deep convection regions of the subpolar glacial north atlantic model predicted sea ice concentrations in this critical region exceed those based upon multiproxy reconstructions and we trace these significant differences to the intensity of the interannual variability of sea ice cover predictions

heinrich events massive late pleistocene detritus layers of the north atlantic and their global climate imprint 1 millennial climate oscillations of the glacial interval are interrupted by extreme events the so called heinrich events of the north atlantic their near global footprint is a testament to coherent interactions among earth s atmosphere oceans and cryosphere on millennial timescales heinrich detritus appears to have been derived from the region around hudson strait it was deposited over approximately 500 250 years several mechanisms have been proposed for the origin of the layers binge purge cycle of the laurentide ice sheet jokulhlaup activity from a hudson bay lake and an ice shelf buildup collapse fed by hudson strait to determine the origin of the heinrich events i recommend 1 further studies of the timing and duration of the events 2 further sedimentology study near the hudson strait and 3 greater spatial and temporal resolution studies of the layers as well as their precursory intervals studies of previous glacial intervals may also provide important constraints

factors controlling the petroleum generation characteristics of palaeogene source rocks in the austrian molasse basin as revealed by principal component analysis biplots abstract after rock eval toc screening and heterogeneity evaluation on 91 palaeogene source rock samples from a well drilled in the austrian molasse basin ten shale samples were selected for detailed investigations by means of pyrolysis gas chromatography bulk kinetics and biomarker identification and quantification afterwards 2 d biplots based on principal component analysis were applied to unravel the palaeo environmental control on the development of petroleum source rocks all samples are immature source rocks with good petroleum generation potentials the redox environment during deposition was generally reducing and palaeosalinity is suggested to be the main factor causing the differences in organic carbon contents among the samples the hydrogen index values the gas generation preferences and the aromaticity of the products are controlled by both depositional environment and precursors and the product of a salinity indicator mttc and the oleanane index is introduced as predictive proxy to evaluate these features the maturity indicator tmax is revealed as dominated by the stability of the kerogen structure which is controlled by the proportion of organic sulphur compounds in the kerogen the global eocene oligocene climate change from a greenhouse to an icehouse world is suggested to play an important role in changing the palaeoenvironment and further in influencing the development of petroleum source rocks by triggering upwelling increasing the palaeo sea water salinity and decreasing the deposition of carbonate minerals the chemometric method suggested here acts as a powerful tool in identifying the controlling factors for the petroleum generation potential among many variables and can be applied more widely in petroleum geology when multi parameters are involved to get quick and meaningful correlations

a 50 000 year record of climate oscillations from florida and its temporal correlation with the heinrich events oscillations of pinus pine pollen in a 50 000 year sequence from lake tulane florida indicate that there were major vegetation shifts during the last glacial cycle episodes of abundant pinus populations indicate a climate that was more wet than intervening phases dominated by quercus oak and ambrosia type ragweed and marsh elder the pinus episodes seem to be temporally correlated with the north atlantic heinrich events which were massive periodic advances of ice streams from the eastern margin of the laurentide ice sheet possible links between the tulane pinus and heinrich events include hemispheric cooling the influences of mississippi meltwater on sea surface temperatures in the gulf of mexico and the effects of north atlantic thermohaline circulation on currents in the gulf