spectrum of pore types and networks in mudrocks and a descriptive classification for matrix related mudrock pores matrix related pore networks in mudrocks are composed of nanometer to micrometer size pores in shale gas systems these pores along with natural fractures form the flow path permeability network that allows flow of gas from the mudrock to induced fractures during production a pore classification consisting of three major matrix related pore types is presented that can be used to quantify matrix related pores and relate them to pore networks two pore types are associated with the mineral matrix the third pore type is associated with organic matter om fracture pores are not controlled by individual matrix particles and are not part of this classification pores associated with mineral particles can be subdivided into interparticle interp pores that are found between particles and crystals and intraparticle intrap pores that are located within particles organic matter pores are intrap pores located within om interparticle mineral pores have a higher probability of being part of an effective pore network than intrap mineral pores because they are more likely to be interconnected although they are intrap om pores are also likely to be part of an interconnected network because of the interconnectivity of om particles in unlithifed near surface muds pores consist of interp and intrap pores and as the muds are buried they compact and lithify during the compaction process a large number of interp and intrap pores are destroyed especially in ductile grain rich muds compaction can decrease the pore volume up to 88 by several kilometers of burial at the onset of hydrocarbon thermal maturation om pores are created in kerogen at depth dissolution of chemically unstable particles can create additional moldic intrap pores

ground penetrating radar and its use in sedimentology principles problems and progress abstract ground penetrating radar gpr also referred to as ground probing radar surface penetrating radar subsurface radar georadar or impulse radar is a noninvasive geophysical technique that detects electrical discontinuities in the shallow subsurface

vertical dimensions and age of the wicklow mountains ice dome eastern ireland and implications for the extent of the last irish ice sheet abstract patterns of erratic distribution show that the wicklow mountains formerly supported an independent ice cap or ice dome geomorphological mapping of the upper limits of evidence for glaciation ice scoured and moulded bedrock perched boulders and the distribution of features indicative of prolonged periglacial conditions tors frost shattered rock blockfields indicates that along the main axis of high ground erosive warm based ice buried all but the highest 725 m summits and over ran adjacent lower peaks and cols the presence of gibbsite in soil samples from above the inferred upper limit of glacial erosion and its absence in all samples from below this limit is consistent with the geomorphological evidence and implies removal of gibbsitic soils below 725 m by glacial erosion during the last glacial stage cosmogenic 10 be exposure ages for rock outcrops above the inferred upper limit of glacial erosion yield pre last glacial maximum lgm ages of 46 9 3 0 ka to 95 9 6 1 ka whereas rock outcrops on summits over ridden by warm based ice give post lgm ages of 18 2 1 2 to 19 1 1 2 ka all geomorphological and dating evidence thus indicates an lgm age for the ice dome the thickness of the ice dome and limited lateral dispersal of erratics indicate that at the lgm the wicklow ice was encircled by and confluent with thick powerful ice streams moving se from the irish midlands and southwards down the irish sea basin this conclusion is irreconcilable with the traditional view that the last irish ice sheet terminated at the south ireland end moraine but consistent with recent proposals that the last ice sheet was much more extensive than previously believed and over ran the south coast of ireland

geochemistry of the extremely high thermal maturity longmaxi shale gas southern sichuan basin abstract the marine shale of the silurian longmaxi formation in southern sichuan basin china is characterized by its huge thickness 100 600 m high toc values 0 35 18 4 favorable types of organic matter i and ii1 high ro values 1 8 4 2 abundant brittle minerals average 56 3 and strong gas generation intensity particularly its bottom section which has toc 2 and thickness of 20 70 m has recently been a main target for shale gas exploration and development geochemical parameters of 13 gas samples from longmaxi shale from 10 wells were analyzed in this study wetness of the gas molar fraction of ethane through pentanes in total gaseous hydrocarbon is only 0 24 0 70 making the longmaxi shale gas among the driest in the world carbon isotopic compositions of the alkane gases from longmaxi shale are characterized by 13c1 13c2 13c3 with the most positive 13c1 values in the world a positive relationship was observed between its 13c1 and 13c2 values reflecting the extremely high thermal maturity of the source rock 2hch4 values range from 140 to 151 and the 2hc2h6 values range from 130 to 173 the hydrogen isotopic compositions were mainly characterized by 2hch4

investigating fluvial features with electrical resistivity imaging and ground penetrating radar the guadalquivir river terrace jaen southern spain abstract a geophysical survey has been conducted on the lowest terrace levels and the present day floodplain of the current course of the guadalquivir river passing through the province of jaen spain using two techniques electrical resistivity imaging eri and ground penetrating radar gpr three areas have been selected in one of these sectors los barrios there is an old quarry where there are excellent outcrops that allow for the calibration of the survey techniques facies associations on these outcrops are typical of meandering rivers with sequences of channel fills lateral accretion of point bars and floodplain facies the usefulness of the two methods is analysed and compared as a support for stratigraphic and sedimentological studies the geometry and lithofacies of subsurface deposits were characterised using eri and compared with field observations a total of 5 electrical resistivity imaging profiles were obtained the changes in electric resistivity highlight granulometric differences in terrace sediments this technique can thus be used to identify the morphology of these bodies the lithofacies silt sand or gravel and buried channel pattern in addition 16 gpr profiles using 100 and 250 mhz antennas were acquired indicating terrace morphology and the filling of the sedimentary bodies in a more detailed manner than in eri the study thus allows for inferring the existence of channel migration the lateral accretion of point bars and the presence of vertical accretion deposits attributable to the floodplains

development of organic porosity in the woodford shale with increasing thermal maturity abstract using a combination of focused ion beam milling and scanning electron microscopy we describe the evolution of secondary organic porosity in eight woodford shale late devonian early mississippian samples with mean random vitrinite reflectance values ranging from 0 51 ro to 6 36 ro organic porosity was observed to be absent in samples with vitrinite reflectance values of up to 0 90 ro with the first appearance of secondary pores starting with the 1 23 ro sample porosity in the organic matter was unexpectedly absent in a sample with a vitrinite reflectance of 2 00 ro however organic pores were again found in samples with higher thermal maturities porosity when present did not appear to be uniformly distributed among the organic matter that was within less than a micron of each other suggesting important differences in composition of the organic matter thin regions of organic matter were observed between grains raising the possibility that small amounts of the deposited organic matter were compacted between grains to form thin layers and or the structures are part of the secondary organic matter interpreted to be post oil bitumen which was left behind as a residue during oil migration through the shale some regions of porous organic matter appeared to be grain protected whereas others did not which indicates that these non protected porous organic regions may be stress supporting with porosity intact under in situ reservoir conditions these observations suggest that thermal maturity alone is insufficient to predict porosity development in organic shales and other factors such as organic matter composition complicate porosity development

deformation of organic matter and its effect on pores in mud rocks pores within organic matter om are strongly linked to hydrocarbon generation and primary migration in fine grained source rocks and are very important for evaluating hydrocarbon storage and flow in shale reservoirs thus it is critical to clarify the features of om hosted pores and their evolution in organic rich mud rocks the om in mud rocks including kerogen and bitumen is deformed when the original equilibrium stress conditions are altered the om deformation at the nano or microscale has rarely been discussed because of the lack of unequivocal evidence this research begins with examining the subsurface evolution of kerogen and bitumen with emphasis on various features of pores hosted by bitumen evidence of om deformation is documented in scanning electron microscope images of seven overmature samples from the lower silurian longmaxi shale sichuan basin to aid in the understanding and analysis om deformation is classified into three types type i deformation induced by one additional force type ii deformation induced by two additional forces acting on two locations of single om particles and type iii deformation induced by three or more deforming forces acting at three or more locations of single om particles thus type i deformation is generally less complex than type ii and iii deformation the om particles subjected to type i deformation were analyzed quantitatively for parameters such as pore size geometry and long axis orientation of elliptical pores deformation of om enhances the robust heterogeneity of om hosted pores

a numerical comparison of 2d resistivity imaging with 10 electrode arrays numerical simulations are used to compare the resolution and efficiency of 2d resistivity imaging surveys for 10 electrode arrays the arrays analysed include polepole pp pole dipole pd half wenner hw wenner wn schlumberger sc dipole dipole dd wenner wb array gm multiple or moving gradient array gd and midpoint potential referred measurement mpr arrays five synthetic geological models simulating a buried channel a narrow conductive dike a narrow resistive dike dipping blocks and covered waste ponds were used to examine the surveying efficiency anomaly effects signal to noise ratios and the imaging capabilities of these arrays the responses to variations in the data density and noise sensitivities of these electrode configurations were also investigated using robust l1 norm inversion and smoothness constrained least squares l2 norm inversion for the five synthetic models the results show the following i gm and wn are less contaminated by noise than the other electrode arrays ii the relative anomaly effects for the different arrays vary with the geological models however the relatively high anomaly effects of pp gm and wb surveys do not always give a high resolution image pd dd and gd can yield better resolution images than gm pp wn and wb although they are more susceptible to noise contamination sc is also a strong candidate but is expected to give more edge effects iii the imaging quality of these arrays is relatively robust with respect to reductions in the data density of a multi electrode layout within the tested ranges iv the robust inversion generally gives better imaging results than the l2 norm inversion especially with noisy data except for the dipping block structure presented here v gd and mpr are well suited to multichannel surveying and gd may produce images that are comparable to those obtained with dd and pd accordingly the gd pd dd and sc arrays are strongly recommended for 2d resistivity imaging where the final choice will be determined by the expected geology the purpose of the survey and logistical considerations

a quantitative three dimensional depositional model of gravelly braided rivers a quantitative three dimensional depositional model of gravelly braided rivers has been developed based largely on the deposits of the sagavanirktok river in northern alaska these deposits were described using cores wireline logs trenches and ground penetrating radar profiles the origin of the deposits was inferred from observations of 1 channel and bar formation and migration and channel filling interpreted from aerial photographs 2 water flow during floods and 3 the topography and texture of the river bed at low flow stage this depositional model quantitatively represents the geometry of the different scales of strataset the spatial relationships among them and their sediment texture distribution porosity and permeability in the model are related to sediment texture the geometry of a particular type and scale of strataset is related to the geometry and migration of the bedform type e g ripples dunes bedload sheets bars associated with deposition of the strataset in particular the length to thickness ratio of stratasets is similar to the wavelength to height ratio of associated bedforms furthermore the wavelength and height of bedforms such as dunes and bars are related to channel depth and width therefore the thickness of a particular scale of strataset i e medium scale cross sets and large scale sets of inclined strata will vary with river dimensions these relationships between the dimensions of stratasets bedforms and channels mean that this depositional model can be applied to other gravelly fluvial deposits the depositional model can be used to interpret the origin of ancient gravelly fluvial deposits and to aid in the characterization of gravelly fluvial aquifers and hydrocarbon reservoirs

organic matter hosted pore system marcellus formation devonian pennsylvania the marcellus formation of pennsylvania represents an outstanding example of an organic matter om hosted pore system most pores detectable by field emission scanning electron microscopy fe sem are associated with om instead of mineral matrix in the two wells studied here total organic carbon toc content is a stronger control on om hosted porosity than is thermal maturity the two study wells span a maturity from late wet gas vitrinite reflectance ro 1 0 to dry gas ro 2 1 samples with a toc less than 5 5 wt display a positive correlation between toc and porosity but samples with a toc greater than 5 5 wt display little or no increase in porosity with a further increasing toc in a subset of samples 14 across a range of toc 2 3 13 6 wt the pore volume detectable by fe sem is a small fraction of total porosity ranging from 2 to 32 of the helium porosity importantly the fe sem visible porosity in om decreases significantly with increasing toc diminishing from 30 of om volume to less than 1 of om volume across the range of toc the morphology and size of om hosted pores also vary systematically with toc the interpretation of this anticorrelation between om content and sem visible pores remains uncertain samples with the lowest om porosity higher toc may represent gas expulsion pore collapse that was more complete as a consequence of greater om connectivity and framework compaction whereas samples with higher om porosity lower toc correspond to rigid mineral frameworks that inhibited compactional expulsion of methane filled bubbles alternatively higher toc samples may contain om low initial hydrogen index relatively unreactive that is less prone to development of fe sem detectable pores in this interpretation om type controlled by sequence stratigraphic position is a factor in determining pore size distribution

ice sheet variability around the north atlantic ocean during the last deglaciation millennial scale variability in the flux of ice rafted detritus to north atlantic sediments during the last glacial period has been interpreted to reflect a climate forced increase in the discharge of icebergs from ice sheet margins surrounding the northern north atlantic ocean 1 but the relationship between ice sheet variability and climate change is not clear as both the sources of ice rafted detritus and the ice marginal processes are varied and complex 2 4 terrestrial records are helpful in unravelling this complexity because they can demonstrate the scale of ice sheet oscillations and whether the ice sheet or sector was advancing or retreating with respect to climate change here we constrain the age and anatomy of a prominent readvance of the british ice sheet in the northern irish sea region at similar to 14 14 c kyr bp similar to 16 4 calendar kyr bp the analysis indicates that the british ice sheet participated in an iceberg discharge episode known as heinrich event 1 comparison with other terrestrial and marine ice sheet records suggests that the dynamic collapse of the laurentide ice sheet beginning at 14 6 15 0 c 14 kyr bp1 4 similar to 17 2 17 6 calendar kyr bp 5 initiated varied responses from other ice sheet margins around the northern north atlantic region these observations support the argument that the release of icebergs and meltwater during heinrich event 1 disrupted the north atlantic thermohaline circulation 6 8 leading to a delay or reversal of deglaciation of the northern hemisphere and at least as far south as 40 degrees s for two to three thousand years 5 9 10 suggesting a climate forcing and response similar to that of the ensuing younger dryas cold snap 11 12

high resolution imaging of the high agri valley basin southern italy with electrical resistivity tomography abstract the first high resolution images of the fault controlled high agri valley basin obtained with the electrical resistivity tomography are presented the agri valley is one of the more complex components of the quaternary fault network of the apennine chain the geometry of the pre quaternary bedrock the location and dip of the master fault and the tectonic evolution of the basin are still a subject of debate therefore deep electrical resistivity tomography integrated with stratigraphic analyses has been carried out to improve knowledge of the geological setting of the basin the high resolution electrical images allow us to reconstruct the complex geometry of the basin the electrical imaging highlights the irregular shape of the basin which is bordered by shallow faults and filled with pleistocene alluvial deposits in longitudinal cross section the basin appears as a mosaic of fault bounded blocks forming three different depocenters separated by intrabasinal highs in transverse cross section the basin is an irregular graben locally asymmetric to the northeast and with secondary grabens due to antithetic faults

unconventional shale gas systems the mississippian barnett shale of north central texas as one model for thermogenic shale gas assessment shale gas resource plays can be distinguished by gas type and system characteristics the newark east gas field located in the fort worth basin texas is defined by thermogenic gas production from low porosity and low permeability barnett shale the barnett shale gas system a self contained source reservoir system has generated large amounts of gas in the key productive areas because of various characteristics and processes including 1 excellent original organic richness and generation potential 2 primary and secondary cracking of kerogen and retained oil respectively 3 retention of oil for cracking to gas by adsorption 4 porosity resulting from organic matter decomposition and 5 brittle mineralogical composition the calculated total gas in place gip based on estimated ultimate recovery that is based on production profiles and operator estimates is about 204 bcf section 5 78 10 9 m 3 1 73 10 4 m 3 we estimate that the barnett shale has a total generation potential of about 609 bbl of oil equivalent ac ft or the equivalent of 3657 mcf ac ft 84 0 m 3 m 3 assuming a thickness of 350 ft 107 m and only sufficient hydrogen for partial cracking of retained oil to gas a total generation potential of 820 bcf section is estimated of this potential approximately 60 was expelled and the balance was retained for secondary cracking of oil to gas if sufficient thermal maturity was reached gas storage capacity of the barnett shale at typical reservoir pressure volume and temperature conditions and 6 porosity shows a maximum storage capacity of 540 mcf ac ft or 159 scf ton

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

integration of electrical resistivity imaging eri and ground penetrating radar gpr methods to identify soil profile around necatibey subway station ankara turkey electrical resistivity imaging eri and ground penetrating radar gpr methods were utilized in this study to identify soil profiles around necatibey subway station of kizilay cayyolu metro line ankara turkey the necatibey metro station is located within the alluvial deposits of dikmen stream and the so called ankara clay at the metro station a number of boreholes were drilled however due to the spacing of the boreholes the boundary between alluvium and ankara clay deposits could not be separated precisely thus in this study eri and gpr methods were utilized to distinguish soil types at the study area gpr measurements were taken from a total of 14 profiles and total length of the profiles was about 320 m for every eri measurement section schlumberger dipole dipole dipole dipole schlumberger and wenner arrays were used results from the geophysical measurements identified that the fill materials are underlain by the dikmen stream channel deposits which consist of silty clay and gravelly sand units the study also shows that the dikmen stream channel deposits are underlain by the ankara clay unit the meaningful range of resistivity values was between 1 and 15 m and the gpr signals were strong in sandy units while they attenuated in clayey environments based on borehole logs eri and gpr data three dimensional lithological subsurface model of the survey area was constructed the resultant three dimensional diagrams may serve engineers as a practical tool during different construction stages groundwater surface water interactions within short and long term and probable remedial measures

morphology genesis and distribution of nanometer scale pores in siliceous mudstones of the mississippian barnett shale research on mudrock attributes has increased dramatically since shale gas systems have become commercial hydrocarbon production targets one of the most significant research questions now being asked focuses on the nature of the pore system in these mudrocks our work on siliceous mudstones from the mississippian barnett shale of the fort worth basin texas shows that the pores in these rocks are dominantly nanometer in scale nanopores we used scanning electron microscopy to characterize barnett pores from a number of cores and have imaged pores as small as 5 nm key to our success in imaging these nanopores is the use of ar ion beam milling this methodology provides flat surfaces that lack topography related to differential hardness and are fundamental for high magnification imaging nanopores are observed in three main modes of occurrence most pores are found in grains of organic matter as intraparticle pores many of these grains contain hundreds of pores intraparticle organic nanopores most commonly have irregular bubblelike elliptical cross sections and range between 5 and 750 nm with the median nanopore size for all grains being approximately 100 nm internal porosities of up to 20 2 have been measured for whole grains of organic matter based on point count data from scanning electron microscopy analysis these nanopores in the organic matter are the predominant pore type in the barnett mudstones and they are related to thermal maturation nanopores are also found in bedding parallel wispy organic rich laminae as intraparticle pores in organic grains and as interparticle pores between organic matter but this mode is not common although less abundant nanopores are also locally present in fine grained matrix areas unassociated with organic matter and as nano to microintercrystalline pores in pyrite framboids intraparticle organic nanopores and pyrite framboid intercrystalline pores contribute to gas storage in barnett mudstones we postulate that permeability pathways within the barnett mudstones are along bedding parallel layers of organic matter or a mesh network of organic matter flakes because this material contains the most pores

thermal history of sedimentary basins maturation indices and kinetics of oil and gas generation temperature is the most sensitive parameter in hydrocarbon generation thus reconstruction of temperature history is essential when evaluating petroleum prospects no measurable parameter can be directly converted to paleotemperature maturation indices such as vitrinite reflectance tmax from rock eval pyrolysis spore coloration thermal alteration index tai or concentration of biological markers offer an indirect approach all these indices are a function of the thermal history through rather complex kinetics frequently influenced by the type of organic matter their significance and validity are reviewed besides the problems of identification e g vitrinite and interlaboratory calibration it is important to simultaneously interpret kerogen type and maturation and to avoid difficult conversions from one index to another geodynamic models where structural and thermal histories are connected are another approach to temper ture reconstruction which could be calibrated against the present distribution of temperature and the present value of maturation indices kinetics of kerogen decomposition controls the amount and composition of hydrocarbons generated an empirical time temperature index tti originally introduced by lopatin does not allow such a quantitative evaluation due to several limitations no provision for different types of kerogen and different rates of reactions poor calibration on vitrinite reflectance it is of limited interest unless one has no access to a desk top computer kinetic models based on a specific calibration made on actual source rock samples can simulate the evolution of all types of organic matter and can provide a quantitative evaluation of oil and gas generated examples from the jurassic source rocks of the paris basin monterey formation of california green river shales of utah paleozoic source eds of the algerian sahara and miocene rocks of the mahakam delta indonesia illustrate various aspects of the discussion geological geochemical models are the most efficient way to integrate geological seismic and geochemical data and they should greatly help to reduce the risk in exploration

quaternary sediment architecture in the orkhon valley central mongolia inferred from capacitive coupled resistivity and georadar measurements abstract detailed information on shallow sediment distribution in basins is required to achieve solutions for problems in quaternary geology geomorphology neotectonics geo archaeology and climatology usually detailed information is obtained by studying outcrops and shallow drillings unfortunately such data are often sparsely distributed and thus cannot characterise entire basins in detail therefore they are frequently combined with remote sensing methods to overcome this limitation remote sensing can cover entire basins but provides information of the land surface only geophysical methods can close the gap between detailed sequences of the shallow sediment inventory from drillings at a few spots and continuous surface information from remote sensing however their interpretation in terms of sediment types is often challenging especially if permafrost conditions complicate their interpretation here we present an approach for the joint interpretation of the geophysical methods ground penetrating radar gpr and capacitive coupled resistivity ccr drill core and remote sensing data the methods gpr and ccr were chosen because they allow relatively fast surveying and provide complementary information we apply the approach to the middle orkhon valley in central mongolia where fluvial alluvial and aeolian processes led to complex sediment architecture the gpr and ccr data measured on profiles with a total length of about 60 km indicate the presence of two distinct layers over the complete surveying area i a thawed layer at the surface and ii a frozen layer below in a first interpretation step we establish a geophysical classification by considering the geophysical signatures of both layers we use sedimentological information from core logs to relate the geophysical classes to sediment types this analysis reveals internal structures of orkhon river sediments such as channels and floodplain sediments we also distinguish alluvial fan deposits and aeolian sediments by their distinct geophysical signature with this procedure we map aeolian sediments debris flow sediments floodplains and channel sediments along the measured profiles in the entire basin we show that the joint interpretation of drillings and geophysical profile measurements matches the information from remote sensing data i e the sediment architecture of vast areas can be characterised by combining these techniques the method presented here proves powerful for characterising large areas with minimal effort and can be applied to similar settings

grain assemblages and strong diagenetic overprinting in siliceous mudrocks barnett shale mississippian fort worth basin texas porosity permeability and total organic carbon toc in a heterogeneous suite of 21 high maturity samples vitrinite reflectance 1 52 2 15 from the barnett shale in the eastern fort worth basin display few correlations with parameters of rock texture fabric and composition these factors being mostly obscured by the effects of a protracted history of diagenesis diagenesis in these rocks includes mechanical and chemical modifications that occurred across a wide range of burial conditions compaction and cementation have mostly destroyed primary intergranular porosity the porosity average 5 vol by gas research institute helium porosimetry and pore size 8 nm median pore throat diameter are reduced to a degree such that pores are difficult to detect even by imaging ar ion milled surfaces with a field emission scanning electron microscope the existing porosity that can be imaged is mostly secondary and is localized dominantly within organic particulate debris and solid bitumen the grain assemblage is highly modified by replacement a weak pattern of correlation survives between bulk rock properties and the ratio of extrabasinal to intrabasinal sources of siliciclastic debris higher porosity permeability and toc are observed in samples representing the extreme end members of mixing between extrabasinal siliciclastic sediment and intrabasinal derived biosiliceous debris reservoir quality in these rocks is neither more strongly nor more simply related to variations in primary texture and composition because the interrelationships between texture and composition are complex and importantly the diagenetic overprint is too strong

outburst flood origin of the central kalamazoo river valley michigan usa abstract geomorphic evidence and stratigraphic information from boreholes suggest that the oversized central kalamazoo river valley ckrv in southwest michigan resulted from a catastrophic outburst flood emanating from subglacial channels under the saginaw lobe of the laurentide ice sheet the ckrv occurs as a deeply incised trench over 2 km wide and in excess of 50 m deep situated in a reentrant formed by the lake michigan saginaw and huron erie lobes the course of the ckrv follows an irregular flow path that bisects the kalamazoo moraine of the lake michigan lobe erosional terraces near the mouth of the channel indicate that lake michigan lobe meltwater drained eastward prior to the westward saginaw outburst prior to valley formation the lake michigan lobe had retreated westward to at least the lake border moraine with the lake michigan lobe absent to impede flow drainage from the ckrv proceeded southwesterly until draining into glacial lake chicago near st joseph michigan the outburst originated from a system of saginaw tunnel channels that display convex up flow profiles and contain eskers meltwater drainage transitioned from subglacial to ice marginal and proglacial environments during the interval represented by the outburst the saginaw lobe appears to have been in a relatively stationary position

the nature of porosity in organic rich mudstones of the upper jurassic kimmeridge clay formation north sea offshore united kingdom abstract analyses of organic rich mudstones from wells that penetrated the upper jurassic kimmeridge clay formation offshore united kingdom were performed to evaluate the nature of both organic and inorganic rock constituents and their relation to porosity in this world class source rock the formation is at varying levels of thermal maturity ranging from immature in the shallowest core samples to mature in the deepest core samples the intent of this study was to evaluate porosity as a function of both organic macerals and thermal maturity at least four distinct types of organic macerals were observed in petrographic and sem analyses and they all were present across the study area the macerals include in decreasing abundance 1 bituminite admixed with clays 2 elongate lamellar masses alginite or bituminite with small quartz feldspar and clay entrained within it 3 terrestrial vitrinite fusinite semifusinite grains and 4 tasmanites microfossils although pores in all maceral types were observed on ion milled surfaces of all samples the pores largely nanopores with some micropores vary as a function of maceral type importantly pores in the macerals do not vary systematically as a function of thermal maturity insofar as organic pores are of similar size and shape in both the immature and mature kimmeridge rocks if any organic pores developed during the generation of hydrocarbons they were apparently not preserved possibly because of the highly ductile nature of much of the rock constituents of kimmeridge mudstones clays and organic material inorganic pores largely micropores with some nanopores have been observed in all kimmeridge mudstones these pores particularly interparticle i e between clay platelets and intraparticle i e in framboidal pyrite in partially dissolved detrital k feldspar and in both detrital and authigenic dolomite are noteworthy because they compose much of the observable porosity in the shales in both immature and mature samples the absence of a systematic increase in organic porosity as a function of either maceral type or thermal maturity indicates that such porosity was probably unrelated to hydrocarbon generation instead much of the porosity within mudstones of the kimmeridge appears to be largely intraparticle and interparticle adjacent to inorganic constituents so the petroleum storage potential in these organic rich mudstones largely resides in inorganic pores

rapid least squares inversion of apparent resistivity pseudosections by a quasi newton method1 a fast inversion technique for the interpretation of data from resistivity tomography surveys has been developed for operation on a microcomputer this technique is based on the smoothness constrained least squares method and it produces a two dimensional subsurface model from the apparent resistivity pseudosection in the first iteration a homogeneous earth model is used as the starting model for which the apparent resistivity partial derivative values can be calculated analytically for subsequent iterations a quasi newton method is used to estimate the partial derivatives which reduces the computer time and memory space required by about eight and twelve times respectively compared to the conventional least squares method tests with a variety of computer models and data from field surveys show that this technique is insensitive to random noise and converges rapidly this technique takes about one minute to invert a single data set on an 80486dx microcomputer

formation and evolution of solid bitumen during oil cracking abstract solid bitumen is widespread throughout lower paleozoic paleo reservoirs in southern china however the processes that control its formation and evolution remain unclear here we document temporal changes in the yield and characteristics of solid bitumen generated during oil cracking using an experimental approach involving the anhydrous pyrolysis of crude oil the results indicate that solid bitumen is predominantly produced in environments of high thermal maturity associated with the dry gas stage of oil cracking i e during rapid methane generation and c2 c5 gaseous hydrocarbon destruction with maximum solid bitumen yields up to about 42 of the original amount of crude oil a near linear relationship exists between solid bitumen yields and methane abundance during the main stage of solid bitumen formation although there is no clear variation in the 13c values of solid bitumen produced at any stage of this process this suggests that the isotopic composition and distribution of solid bitumen within a reservoir can be used to identify hydrocarbon sources delineate the range of paleo reservoirs and assess the size of paleo oil reservoirs and oil cracked gas reservoirs within a basin

electrical resistivity tomography to investigate geological structures of the earth s upper crust it is important to have detailed knowledge of the electrical properties of the earth s crust in order to recognize geological structures and to understand tectonic processes in the area surrounding the german continental deep drilling project ktb we have used dc dipole dipole soundings to investigate the electrical conductivity distribution down to a depth of several kilometres we have adapted the electrical resistivity tomography ert technique a well established near surface method to large scale experiments independent transmitting and receiving units were used to realize the concept of simultaneous multichannel registration of the scalar electrical potential at 44 dipoles the measured data yielded apparent resistivities which were inverted to a 2d resistivity model ranging from the surface down to a depth of 4 km two highly conductive structures with steep inclination were detected they are expected to be major fault zones embedded in a metamorphic body the rather low resistivity 10 m can be explained by the existence of graphitic minerals and or electrolytic fluids

contribution of electrical resistivity tomography to the study of detrital aquifers affected by seawater intrusion extrusion effects the river velez delta velez malaga southern spain abstract the coastal aquifer of the plio quaternary delta sediment deposits of the velez river province of malaga spain presents a highly irregular basement morphology and widely varying fill thickness 10 80 m between neighbouring sectors the basin which is tectonically controlled is filled with lutite facies alternating with channel filling rudites this detrital aquifer is affected by seasonal seawater intrusion extrusion processes due to increasing withdrawal of groundwater for human consumption and irrigation during dry periods a study was performed to improve the hydrogeological knowledge of this coastal aquifer system the study examined the morphology of the impervious substratum the facies distribution and the position of the seawater wedge for this purpose an electrical resistivity tomography ert geophysical technique was used and the tomographic data were calibrated using geological observations and borehole studies an analysis was carried out to compare the direct information obtained from the 35 boreholes with the indirect data corresponding to the four electrical tomography profiles in the study over 9660 resistivity data points were processed the ert profiles perfectly corroborated the information derived from the boreholes the profiles made it possible to detect thickness changes lithological changes and the presence of faults moreover from a hydrogeologic standpoint this research technique is capable of detecting the position of the phreatic level and in coastal aquifers such as the one examined in this study the possible horizontal or vertical penetration of seawater intrusion therefore the electrical geophysical prospecting based on ert can be highly useful in areas lacking sufficient geological information and or mechanical borehole data

organic matter pores and oil generation in the tuscaloosa marine shale the upper cretaceous tuscaloosa marine shale tms is an oil play across central louisiana and southwest mississippi the lower tms is characterized by relatively high log resistivity 5 ohm m compared to the upper part and this elevated resistivity zone erz has become the primary target zone this study is to investigate the cause of variation in log resistivity based on the data of petrography mineralogy and organic matter property and porosity the results suggest that log resistivity is not controlled by mineralogy or porosity rather it is associated with oil generation during organic matter maturation total organic carbon toc content rock eval free hydrocarbon yield s1 and hydrogen index hi in the studied core increase with depth porosity within organic matter om measured by field emission scanning electron microscopy fe sem is also higher within the erz the correlated variations among toc content s1 values om porosity and log resistivity suggest that the higher log resistivity resulted from in situ oil generation and that the om pores were generated during oil generation thermal maturity varies little in the core whereas the downward increasing hi indicates an increasing abundance of oil prone type ii kerogen higher om porosity appears to be related to the greater proportion of type ii kerogen in the erz the data set demonstrates that higher contents of toc and oil prone kerogen are the combined factors for higher oil generation therefore higher log resistivity in the erz the study provides a quantitative relationship between om porosity and oil generation

investigation of formation and evolution of organic matter pores in marine shale by helium ion microscope an example from the lower silurian longmaxi shale south china abstract using a helium ion microscope him we carefully observed and analyzed organic matter om pores in several longmaxi shale samples collected from the upper yangtze platform south china the results indicate that the formation process of om pore essentially involves gradual expansion and connection of defects space within om this process which is divided into the four stages of formation expansion connection and consolidation can involve pore scales ranging from a few nanometers to over a micrometer under him more specifically spotted spherical pores first form within om then expand until they connect to adjacent pores within large areas of such connectivity pit structures eventually form preliminarily defined as om pores that are significantly larger than surrounding pores essentially being greater than 100 nm in size as the final stage of om pore evolution the shape and size of pit structures can be limited by the framework of mineral particles around or within the om additionally we found that surrounding pores are smaller when pit structures develop perhaps because removal of side chains of om tends to occur on the inner surface of the formed pores leading them to rapidly expand or because om particles have differing compositions or structures some of which may be unfavorable to pore development

small headwater stream evolution in response to lateglacial and early holocene climatic changes and geomorphological features in the saint gond marshes paris basin france the study focuses on river dynamics and vegetation changes during the last glacial interglacial transition from a headwater stream located in the eastern part of the paris basin we adopt a spatial multiproxy approach combining image analyses geophysical surveys sedimentary and pollen record analyses to document the impact of lateglacial climate changes and geomorphological features on vegetation and fluvial dynamics in the small boitet catchment ca 20 km2 our results show that the sedimentary record is organized into six successive alluvial sequences reflecting changes in discharge and channel morphology in response to short phases of climate oscillations during the lateglacial and early holocene periods the boitet alluvial sequences present some similarities with other nw european rivers that are interpreted as large scale fluvial system evolution to climate changes however some local differences have also been highlighted partly related to the upstream position of the catchment among them two distinctive features of the boitet catchment are 1 the preservation of the oldest dryas deposits which have been rarely described in this area and 2 the recognition of multichannel river dynamics during the oldest dryas and younger dryas we demonstrate that the fluvial evolution is firstly triggered by climate changes and that land surface features may also influence specifically upstream areas revealing contrasting responses of the river system

valley asymmetry evidence for periglacial activity in the central north sea present day open valleys with distinct asymmetric profiles have been studied from the central north sea the bulk of the valleys exhibit steep north facing and shallow south facing slopes this asymmetry is ascribed to preferential slumping of the south facing slope under periglacial climatic conditions exceptions to the regional asymmetric trend are probably the result of more localized factors such as fluvial and microclimatic processes and the effects of local geology the recognition of this type of within valley asymmetry associated with slumping in buried valleys within the quaternary sequence may be indicative of former periglacial activity

pore and pore network evolution of upper cretaceous boquillas eagle ford equivalent mudrocks results from gold tube pyrolysis experiments low maturity boquillas formation eagle ford formation equivalent organic lean calcareous mudrock samples collected from outcrop were heated in gold tubes under confining pressure to investigate the evolution of organic matter om pores and mineral pores the majority of om in the boquillas samples was migrated petroleum bitumen based on evidence from geochemical analyses solvent extraction and scanning electron microscopy sem petrography the sem images showed several diagenetic events including framboidal pyrite precipitation and euhedral calcite quartz kaolinite and chlorite cementation that were all interpreted to have occurred prior to petroleum expulsion and pore scale to bed scale petroleum bitumen migration two major pore types were present prior to heating primary mineral pores and modified mineral pores with migrated relic om from heating experiments pores were found to be associated with stages of om maturation during the bitumen generation stage modified mineral pores were dominant and primary interparticle and intraparticle pores were present during the oil generation stage modified mineral pores with isopachous om rim were observed to be the most abundant pore type during the gas generation stage both modified mineral pores and nanometer sized spongy om pores were predominant we interpreted the occurrence of modified mineral pores to be the result of 1 oil and gas filled or partially filled voids that developed during petroleum migration and water expulsion 2 voids after removing of oil gas and water during sample preparation and 3 trapping of water molecules the formation of these nanopores was interpreted to be related to gas generation and structural rearrangement of om

porosity of devonian and mississippian new albany shale across a maturation gradient insights from organic petrology gas adsorption and mercury intrusion the evolution of porosity in shales with increasing maturity was examined in a suite of five new albany shale samples spanning a maturity range from immature vitrinite reflectance ro 0 35 to postmature ro 1 41 devonian to lower mississippian new albany shale samples from the illinois basin used in this study contain marine type ii kerogen having total organic carbon contents from 1 2 to 13 0 wt organic petrology co2 and n2 low pressure adsorption and mercury intrusion capillary pressure techniques were used to quantify pore volumes pore sizes and pore size distributions increasing maturity of the new albany shale is paralleled by many changes in the characteristics of porosity the total porosity of 9 1 vol in immature new albany shale decreases to 1 5 vol in the late mature sample whereas total pore volumes decrease from 0 0365 to 0 0059 cm3 g in the same sequence reversing the trend at even higher maturity the postmature new albany shale exhibits higher porosity and larger total pore volumes compared to the late mature sample with increasing maturity changes in total porosity and total pore volumes are accompanied by changes in pore size distributions and relative proportions of micropores mesopores and macropores porosity related variances are directly related to differences in the amount and character of the organic matter and mineralogical composition but maturity exerts the dominant control upon these characteristics we conclude that organic matter transformation due to hydrocarbon generation and migration is a pivotal cause of the observed porosity differences

structural and depositional evidence for repeated ice marginal oscillation along the eastern margin of the late devensian irish sea ice stream abstract late devensian glacigenic sediments and landforms along the north west coast of wales document the advance and subsequent retreat of the eastern margin of an irish sea ice stream that met coalesced and ultimately uncoupled from ice radiating outwards from the adjacent welsh ice cap centred over snowdonia across the boundary between the two former ice masses is a set of sediment landform assemblages that reflect rapidly changing erosional and depositional conditions during ice interaction from the inner part of the ice stream the assemblages range outwards from a subglacial depositional assemblage characterised by drumlin swarms through a subglacial erosional assemblage marked by prominent bedrock scours and large subglacial rock channels through an ice marginal assemblage identified by closely spaced glaciotectonised push moraines and intervening marginal sandur troughs into a freely expanding proglacial sandur and lacustrine delta assemblage the ice marginal assemblage provides evidence for numerous oscillatory episodes during retreat and at least 20 ice marginal limits can be identified at least 11 of these display multiple criteria for identifying readvance and in the ideal case is characterised by a moraine form built by localised tectonic stacking of diamict to the rear fronted by a clastic wedge of ice front alluvial fan gravel and intercalated flow till the distribution of sediment landform assemblages suggests a highly dynamic convergent ice stream flow pattern with high ice velocity a sharply delineated lateral shear margin pervasive ice marginal glaciotectonic deformation and a tightly focused ice marginal sediment delivery system all signature characteristics of contemporary ice streams

detailed internal architecture of a fluvial channel sandstone determined from outcrop cores and 3 d ground penetrating radar example from the middle cretaceous ferron sandstone east central utah ideally characterization of hydrocarbon reservoirs requires information about heterogeneity at a submeter scale in three dimensions detailed geologic information and permeability data from surface and cliff face outcrops and boreholes in the alluvial part of the ferron sandstone are integrated here with three dimensional 3 d ground penetrating radar gpr data for analysis of a near surface sandstone reservoir analog in fluvial channel deposits the gpr survey covers a volume with a surface area of 40 x 16 5 m and a depth of 12 m five architectural elements are identified and described in outcrop and well cores using a sixfold hierarchy of bounding surfaces internally the lower four units consist of fine grained parallel laminated sandstone and the upper unit consists of medium grained trough cross bedded sandstone the same sedimentary architectural elements and associated bounding surfaces are distinguished in the gpr data by making use of principles developed in seismic stratigraphic analysis to facilitate comparison of geologic features in the depth domain and radar reflectors in the time domain the radar data are depth migrated the gpr interpretation is carried out mainly on migrated 100 mhz data with a vertical resolution of about 0 5 m measures of the spatial continuity and variation of the first and second order bounding surfaces are obtained by computing 3 d experimental variograms for each architectural element each radar begin page 1584 facies the maximum correlation length of the dominant internal features ranges between 4 and 6 m and the anisotropy factor ranges between 0 6 and 0 95

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

application of geophysical prospecting techniques to evaluate geological mining heritage the sinapismo mine la carolina southern spain abstract geological mining heritage is a valuable resource that deserves proper attention given its educational scientific landscape and cultural worth the significant geological and mining wealth of the abandoned metallogenic district of la carolina southern spain is particularly interesting in this regard this study is focused on one of the emblematic veins of this district the sinapismo vein and more specifically on the la paloma drainage adit stretching a total length of 1170 m a geological and geophysical study was conducted in the interior of this drainage structure to assess its heritage value as well as the condition of the mine voids with a view to converting the mine into a site open to the public electrical resistivity imaging eri provides a general characterization of the mine highlighting the vergence of the geological structure and the main faults and veins ground penetrating radar gpr offers higher resolution but provides a limited depth of penetration less than 3 m in this case profiles have been constructed using 500 mhz and 250 mhz shielded antennas to assist the analysis of the lithological alternance quartzites and phyllites layer dip and the various associated fault and vein families the position of the sinapismo shaft with respect to the la paloma drainage adit will permit an itinerary for visitors to be designed along the first 480 m of the tunnel because it will allow for the proper location of two evacuation points the shaft and the entrance to the adit according to the results obtained from eri and gpr studies access to the rest of the drainage tunnel by visitors is inadvisable for safety reasons due to the existing fracture networks and the presence of veining the two geophysical techniques applied in this study eri and gpr provide on the one hand complementary information to the geological observations which can be used to evaluate the geo mining heritage on the other hand they offer information about the geomechanical conditions of the rock mass thus permitting a safety assessment of access to the la paloma adit

pore types in the barnett and woodford gas shales contribution to understanding gas storage and migration pathways in fine grained rocks the identification of organoporosity microscale and nanoscale pores within organic matter in shales its importance to storage and perhaps transfer of gas molecules through shales and methods for gathering three dimensional images of the pores such as by argon ion milling and or field emission scanning electron microscopy have all been well documented and discussed for unconventional gas shales however other types of pores exist within shales that can be important to storage and migration of gas and oil and other technologies are available for their identification and imaging the different pore types found in the barnett and woodford shales are described and classified in this article scanning electron microscopy revealed the presence of porous floccules in both the barnett and woodford shales which appear similar to laboratory produced floccules and to those in other ancient shales published experimental and observational studies indicate that floccules are hydraulically equivalent to coarser grains and are transported by traction processes current induced microsedimentary structures and textures within the barnett and woodford shales as well as the preserved floccules suggest such processes were active during transport and deposition pore spaces between the floccules are open and can provide storage space as well as permeability pathways for gas molecules through the shales pores are also found within organic matter that occurs both as discrete particles and as adsorbed coatings around clay grains in the shale they are referred to here as organopores porous fecal pellets are also common in the barnett shale preserved fossil fragments such as organic walled spores and inorganic sponge spicules have hollow central chambers which may remain partially or completely open even after burial intraparticle pores occur between grains of various minerals e g pyrite framboids microchannels within shale matrix which may be the bounding surfaces of scours or microsedimentary structures may also provide permeability pathways for hydrocarbon migration mircrofractures are also common and their initiation might be related to mineral crystal structure when present in sufficient quantity these pore types offer potential gas and oil molecule storage spaces and permeability pathways through the shales

case studies of electrical and electromagnetic methods applied to mapping active faults beneath the thick quaternary it is of considerable importance to explore the geological structure around active faults especially near surface unconsolidated layers to estimate the faults activity there are numerous case studies to investigate active faults using geophysical exploration methods however only a few cases have been verified in detail by comparison with other geological information we have applied electric and electromagnetic methods which can be effective for exploring to several hundred meters depth to reveal geological structures covered by thick quaternary formations at four active fault sites in japan in this paper we used the controlled source audio frequency magnetotelluric csamt method the direct current dc resistivity method and the resistivity tomography method the resistivity profiles were analyzed by two dimensional inversion techniques and the resulting models were verified by comparison with geological evidence obtained by drilling or trenching our results are as follows 1 csamt is an effective method for defining an outline of geological structures around a fault to several hundred meters deep it enables us to define a resistivity boundary between different kinds of bedrock with a fault contact 2 the dc resistivity method distinguishes each sedimentary unit as a different resistivity zone and detects the vertical displacement in the quaternary formations 3 the resistivity tomography method is useful to determine in more detail the flexure structure produced by faulting using these latter two methods we can select drilling positions and trenching locations in addition it is verified from the data measured along trench walls and electrical logging that the resistivity of soft sedimentary layers and clayey cataclastic bedrock conforms to the relationship established between the resistivity and the clay content these resistivity methods have the advantages of detecting clayey layers as very low resistivity zones the overall conclusion is that the combination of these resistivity methods provides us with more detailed and accurate information for estimating fault activity

fractured shale gas systems the first commercial united states natural gas production 1821 came from an organic rich devonian shale in the appalachian basin understanding the geological and geochemical nature of organic shale formations and improving their gas producibility have subsequently been the challenge of millions of dollars worth of research since the 1970s shale gas systems essentially are continuous type biogenic predominant thermogenic or combined biogenic thermogenic gas accumulations characterized by widespread gas saturation subtle trapping mechanisms seals of variable lithology and relatively short hydrocarbon migration distances shale gas may be stored as free gas in natural fractures and intergranular porosity as gas sorbed onto kerogen and clay particle surfaces or as gas dissolved in kerogen and bitumen five united states shale formations that presently produce gas commercially exhibit an unexpectedly wide variation in the values of five key parameters thermal maturity expressed as vitrinite reflectance sorbed gas fraction reservoir thickness total organic carbon content and volume of gas in place the degree of natural fracture development in an otherwise low matrix permeability shale reservoir is a controlling factor in gas producibility to date unstimulated commercial production has been achievable in only a small proportion of shale wells those that intercept natural fracture networks in most other cases a successful shale gas well requires hydraulic stimulation together the devonian antrim shale of the michigan basin and devonian ohio shale of the appalachian basin accounted for about 84 of the total 380 bcf of shale gas produced in 1999 however annual gas production is steadily increasing from three other major organic shale formations that subsequently have been explored and developed the devonian new albany shale in the illinois basin the mississippian barnett shale in the fort worth basin and the cretaceous lewis shale in the san juan basin in the basins for which estimates have been made shale gas resources are substantial with in place volumes of 497 783 tcf the estimated technically recoverable resource exclusive of the lewis shale ranges from 31 to 76 tcf in both cases the ohio shale accounts for the largest share

tunnel channels and associated landforms south central ontario their implications for ice sheet hydrology the peterborough trenton drumlin field and associated meltwater erosion marks s forms were interpreted as the products of erosion by turbulent separated flows within a catastrophically released subglacial meltwater sheet the algonquin event recent theoretical modelling of ice sheet hydrology suggests progressive channelization of meltwater during the collapse of such a sheet inductive testing of this hypothesis using observations in south central ontario forms the crux of this paper a geometric model of the interaction of rough ice base and bed surfaces gives inferred meltwater flow patterns such a rough interactive geometry is suggested as the bed is drumlinized and flows responsible for drumlins may be expected to have eroded similar forms into the ice base three landforms in south central ontario namely tunnel channels megachannels and late stage sheet flow scours are described and interpreted as evidence of progressive channelization and flow diversion processes governed by the geometri

the formation and evolution of an isolated submarine valley in the north channel irish sea an investigation of beaufort s dyke beaufort s dyke is a submarine depression located in the north channel of the irish sea with a maximum depth of 312 m the dyke is one of the deepest areas within the european continental shelf integration and interpretation of 450 km of sparker seismic data and full coverage bathymetric data derived from multi beam echo sounder surveys allow for the investigation of the formation processes of beaufort s dyke and the evolution of geomorphological features within it the dyke formed by composite subglacial processes dominated by subglacial meltwater discharge is interpreted as a tunnel valley the regional isolation of beaufort s dyke may be explained by the bounding of the north channel by the bedrock masses of ireland and scotland coupled with the exploitation of structural weakness along a fault plane and presence of halite in the eroded substrate enhancing the erosive potential of the overlying glacier beaufort s dyke has probably been maintained as an open feature by strong rectilinear tidal currents the morphology of lunate sediment waves and a large parabolic bedform towards the south of the dyke contradict the observed dominant s n mean hydrodynamic flow recorded within the north channel suggesting an alternative hydrodynamic regime either within the dyke or during bedform creation

late wisconsin landform distribution and glacier bed conditions in wisconsin abstract the late wisconsin laurentide ice sheet advanced across permafrost and reached its maximum extent in wisconsin between about 18 000 and 15 000 years ago deep permafrost persisted in southern wisconsin until about 14 000 years ago and in northern wisconsin until about 13 000 years ago we suggest that during maximum glaciation a zone about 5 km wide in the south and 20 km wide in the north along the margin of the late wisconsin glacier was frozen to its bed meltwater from farther behind the margin where the bed was at least locally thawed cut a series of closely spaced tunnel channels through the frozen bed zone these channels most likely formed episodically and they were the source for much of the meltwater stream sediment deposited in broad outwash plains beyond the ice margin frozen bed conditions near the margin also likely contributed to increased upward shearing of sediment and the accumulation of thicl supraglacial sediment in northern areas up ice from the frozen bed zone the glacier bed was at least locally thawed in a zone about 75 km wide extensive drumlin fields formed in the area of the bed that was thawed by about 13 000 years ago permafrost melted in northern wisconsin and thawed bed conditions probably extended to the ice margin throughout wisconsin and adjacent areas after about 13 000 years ago in northern wisconsin the glacier was sliding on its bed and forming drumlins out to the ice margin and thick supraglacial sediment no longer accumulated

origin properties and implications of solid bitumen in source rock reservoirs a review abstract this paper reviews the significance of solid bitumen with emphasis on source rock reservoirs we discuss difficulties and discrepancies with terminology especially those terms related to the origin of solid bitumen and its physical and chemical properties various definitions of solid bitumen have their own justifications and can be used provided there is clarity about which defining criteria are being considered difficulties in conforming to chemical solubility or origin related definitions lead us to suggest adapting the reflectance of solid hydrocarbon as a practical choice for placing the boundary between solid bitumen and pyrobitumen and 1 50 is proposed as the boundary value it has to be noted that this boundary may be shifted down to 1 3 for sulfur rich kerogen recently much progress has been made by combining imaging and physical adsorption techniques in porosity studies and so the porosity of solid bitumen is given special emphasis comparing pore characteristics obtained from sem versus those generated by gas adsorption mercury intrusion or neutron scattering techniques indicates that the sem pore inventory fails to account for the smallest pores we review the implications of the abundance of solid bitumen on reservoir quality porosity permeability and producibility based on examples of selected sequences one of the difficulties in predicting the influence of solid bitumen bearing horizons on reservoir quality arises from the problems with detecting organic phases using various logging techniques the use of specialized techniques such as nmr logging that allows two dimensional t1 and t2 measurements should be expanded and other potential techniques need to be further researched and tested certain aspects of the properties of solid bitumen that are not as well understood such as its hydrocarbon generation potential or its role in hydrocarbon migration are also discussed with the aim of identifying further research that could lead to a better understanding of the role that solid bitumen plays in unconventional reservoirs

sea level change in the irish sea since the last glacial maximum constraints from isostatic modelling models of glacio hydroisostatic sea level change have been published for the british isles that are broadly consistent with the observational evidence as well as with glaciological constraints it has been argued however that the models fail to represent sea level change along the irish sea margins and in southern ireland for the post deglaciation period the argument rests on the interpretation of the depositional environment of the elevated irish sea drift on both sides of the irish sea whether this is terrestrial or glaciomarine the isostatic models for the british isles are consistent with the former interpretation in that sea levels on either side of the irish sea south of about the isle of man are not predicted to have risen above present sea level at any time since the deglaciation of the irish sea this implies that ice over both the irish sea and ireland was relatively thin ca 600 700 m over ireland if the glaciomarine interpretation of the elevated irish sea drift is correct then the maximum ice thickness over central and southern ireland would have to reach 2000 m exceeding that over scotland furthermore for the resulting sea level change to be consistent with the holocene evidence this thick ice sheet could not have extended to the eastern side of the irish sea nor could it have been very thick at its northern and western limits if such an ice model is extreme and incompatible with glaciological observations then the alternative is to accept the interpretation of the irish sea drift as terrestrial in origin copyright 2001 john wiley sons ltd

electrical resistivity imaging of anastomosing river subsurface stratigraphy and possible controls of fluvial style change in a graben like basin czech republic abstract subject to frequent channel avulsions due to the increased frequency of floods rise of base level and or sediment overloading anastomosing rivers are sensitive to external climatic or tectonic forcing in sedimentary basins the morava river czech republic shows a well developed holocene anastomosis confined to the pull apart type upper morava basin umb we studied the stratigraphy and aggradation rates of the umb using electrical resistivity tomography ert dipole electromagnetic profiling demp core data and radiocarbon ages with the aim of identifying factors triggering the anastomosis at the pleistocene holocene transition the ert and demp proved to be excellent tools to visualize the shape and thickness of floodplain depositional units abandoned meanders scroll bars etc the major geophysical surfaces identified are the base of the late weichselian braided stream deposits osl age 34 53 3 42 ka interpreted as a palaeo stream gradient of the morava river and their transition to holocene floodplain deposits in the late weichselian the river aggraded at an average rate of 0 2 mm yr the holocene oldest 14c age 7 066 0 072 ka short term aggradation rates reached up to 13 7 mm yr but the average long term rates 0 07 to 0 4 mm yr are comparable to the late weichselian the stratigraphy and sediment ages indicate that the onset of anastomosis was not likely associated with accelerated basin subsidence possible controls of the anastomosis include upstream control by numerous tributaries large wood debris in the floodplain forests and changes in land use the tectonic and geomorphic context of the umb pull apart basin probably favoured the development of the anastomosis