the influence of clay content salinity stress and wettability on the dielectric properties of brine saturated rocks 10 hz to 10 mhz complex impedance measurements have been performed on 14 shaly sand samples berea sandstone and ottawa sand bentonite packs in a frequency range of 10 hz to 10 mhz using both the two and four electrode techniques measurements have been conducted at an effective radial stress varying from ambient pressure to 4000 psi for brine saturated oil wet and water wet samples the dielectric permittivity is found to correlate with the clay volume fraction the cation exchange capacity and electrochemical potential of the rock samples and to depend strongly on the salinity of the brine used stress and wettability are shown to have a small influence on the dielectric constant of fully brine saturated rocks a lower critical frequency is found to characterize the geometry of the pore space empirical correlations between the dielectric constant frequency permeability cation exchange capacity and porosity are presented for the shaly sands used in this study these correlations provide a means of estimating important petrophysical parameters such as the permeability and the clay content from a nondestructive complex impedance sweep of shaly sands fully saturated with brine

stress perturbations associated with active faults penetrated by boreholes possible evidence for near complete stress drop and a new technique for stress magnitude measurement detailed studies of stress induced wellbore breakouts in wells drilled through active faults reveal stress field discontinuities that are apparently associated with recent fault movements these discontinuities are expressed as localized rotations in wellbore breakout orientation in the vicinity of the fault penetrated by the borehole this phenomenon is observed in a variety of tectonic environments and rock types utilizing cases where relatively complete knowledge of the horizontal principal stresses is available from in situ measurements we use three dimensional dislocation modeling to demonstrate that these discontinuities can be explained as the superposition of a reference stress state and a perturbation caused by movement on preexisting faults case studies from normal strike slip and reverse faulting stress states indicate that nearly complete stress drop is required to match the observed breakout orientation anomalies hydraulic fracturing data independently confirm the occurrence of near complete stress drop on some faults penetrated by drilling modeling of the observed interactions between breakouts and fractures can also be used to obtain information about the magnitude of in situ stress

effects of birefringence within ice sheets on obliquely propagating radio waves in this paper effects of birefringence on radio waves obliquely propagating though polar ice sheets are examined to facilitate interpretations of bistatic and side looking radar data a formalism applicable for arbitrary radar configurations is developed to predict the returned power from within and beneath the ice sheets that have arbitrary alignments of ice crystals ice fabrics we applied this formalism to a range of ice fabrics found in ice cores and assessed the effects of birefringence in terms of ray path configurations ice fabrics and radar frequency predicted frequency dependence of the bed return power replicates prominent features observed at greenland ngrip ice core site results show that birefringence in ice of 1 km or more thickness with strong weak fabric can reduce the power returned from the bed 2 db or more at frequencies higher than 200 mhz 20 mhz as compared to isotropic ice this suggests that quantitative interpretation of the power returned from the bed requires careful assessment of birefringence almost everywhere over the ice sheets application of this formalism also suggests a radar frequency range usable for attenuation measurements possible effects of fabric on synthetic aperture radar processing and a feasibility of remote sensing of ice fabric

multifractal characterization of microbially induced magnesian calcite formation in recent tidal flat sediments abstract structures resulting from biogenic carbonate cementation of microbial mats in recent siliciclastic tidal flat sediments of the north sea are analyzed quantitatively by a novel combination of scanning electron microscopy and energy dispersive x ray spectrometry sem edx imaging and subsequent multifractal analysis evaluation of calcium distribution patterns and their links to sediment intrinsic mineralization processes show that the applied geometrical technique is an efficient tool for detecting microscopic variations in elemental distributions and related minerals within sedimentary matrices two main conclusions can be drawn i magnesian calcite is a rapidly formed product of the early diagenesis of organic matter in recent bioactive marine sediments and ii multifractal spectra are measures for the spatial inhomogeneity of authigenic calcification processes acting on the sedimentary structure this implies that elemental distribution patterns in a sedimentary system are scale independent phenomena processes causing such patterns have occurred over certain periods with varying rates and on different scales the detection of multifractal measures also opens a way towards a systematic survey of dynamic processes occurring in sedimentary structures

ages distributions and origins of upland coastal dune sheets in oregon usa a total of ten upland dune sheets totaling 245 km in combined length have been investigated for their origin s along the oregon coast 500 km in length the ages of dune emplacement range from 0 1 to 103 ka based on radiocarbon 36 samples and luminescence 46 samples dating techniques the majority of the emplacement dates fall into two periods of late pleistocene age 11 103 ka and mid late holocene age 0 1 8 ka that correspond to marine low stand and marine high stand conditions respectively the distribution of both the late pleistocene dune sheets 516 km 2 total surface area and the late holocene dune sheets 184 km 2 are concentrated 90 of total surface area along a 100 km coastal reach of the south central oregon coast this coastal reach lies directly landward of a major bight heceta perpetua stonewall banks on the continental shelf at depths of 30 200 m below present mean sea level msl the banks served to trap northward littoral drift during most of the late pleistocene conditions of lowered sea level 50 20 m msl the emerged inner shelf permitted cross shelf eolian sand transport 10 50 km distance by onshore winds the depocenter sand deposits were reworked by the holocene marine transgression and carried landward by asymmetric wave transport during early to mid holocene time the earliest dated onset of holocene dune accretion occurred at 8 ka in the central oregon coast a northward migration of northeast pacific storm tracks to the latitude of the shelf depocenter stonewall perpetua heceta banks in holocene time resulted in eastward wave transport from the offshore depocenter the complex interplay of coastal morphology paleosea level and paleoclimate yielded the observed peak distribution of beach and dune sand observed along the south central oregon coast 2007 elsevier b v all rights reserved

fractal measurements of sandstones shales and carbonates measurements were made of the fractal properties of sandstones shales and carbonates using a statistical analysis of structural features on fracture surfaces fractal behavior is associated with power law behavior for the number of features as a function of the feature size on the pore rock interface only one sedimentary rock a novaculite was found not to have a fractal structure the fractal dimensions range from 2 27 to 2 89 and the long length limits to the fractal regime range from 2 m to over 50 m in all cases the fractal behavior extends to less than 0 2 m which is the measurement resolution the porosity associated with the fractal pore rock interface can be calculated from the fractal parameters some of the samples have additional porosity not associated with power law behavior photographs and other evidence are used to show that the fractal structures are the result of diagenesis fractal diagenetic structures include euhedral quartz overgrowths druse quartz calcite dolomite clays and chert

heterogeneity of intergranular intraparticle and organic pores in longmaxi shale in sichuan basin south china evidence from sem digital images and fractal and multifractal geometries abstract previous studies have determined many types of pores in shale such as organic pores inorganic pores and microfractures in this study pores are classified as intergranular intraparticle and organic pores based on the location of their occurrence the heterogeneities of the three pore types and their effects on the occurrence of shale gas which is of utmost practical importance for shale gas exploration and development are discussed in this study the three types of pores are quantitatively characterized using fractal and multifractal methods the mean fractal dimension and mean width of the multifractal spectrum of these pores are found to be different i e 1 5985 and 1 665 for intraparticle pores 1 5869 and 1 475 for intergranular pores and 1 6 and 1 3725 for organic pores intraparticle pores have the highest heterogeneity intergranular pores have intermediate heterogeneity and organic pores have the lowest heterogeneity sem images show that organic pores have good connectivity homogeneous distribution and small range of aperture change but have the lowest heterogeneity even where pores are abundant thus they provide the largest shale gas occurrence space in contrast intergranular pores are less abundant have lower connectivity and have higher heterogeneity than organic pores thereby providing a relatively smaller shale gas occurrence space finally intraparticle pores are the least abundant and possess the poorest connectivity largest range of aperture change and highest heterogeneity of the three pore types thereby providing the smallest shale gas occurrence space we conclude that organic pores are crucial to the occurrence of shale gas and can provide a new index for the evaluation of shale gas exploration and development

3d digital rock modeling of the fractal properties of pore structures abstract fractal parameters of porous media have been a focus of study in petroleum engineering and hydrogeology for several decades because they provide an effective way to describe the complexity of pore structure across a wide range of scales this paper combines 3d process driven digital rock modeling with fractal analysis in order to understand the effect of varying sorting compaction cementation and the fine grain fraction of binary models on the fractal parameters and specific surface area of porous media digital rock models drms were constructed to simulate sandstone using a process driven modeling technique which simulates sedimentation the fractal parameters of the resulting pore geometry were calculated using the box counting method on 2d and 3d representations of the drms our simulations indicate that increasing compaction or cementation lead to significant decreases in fractal dimension specific surface area ssp and porosity showing that these two diagenetic processes can affect the pore microstructure of the rock significantly while interface fractal dimension di and ssp both increase slightly with decreases in sorting grain size variety and porosity decreases slightly examining the behavior of binary models the porosity of our digital models shows a v shaped curve as fine grain fraction increases from 0 to 1 consistent with but higher than the theoretical values which we attribute to incomplete packing of the grains arising from the simplified packing algorithm and finite boundary of models the value of both ssp and di increase as the fine grain fraction increases however we must notice that the porosity may be underestimated and the fractal dimension may be overestimated when we use models consisting of very fine spherical grains due to the effect of image resolution

evaluating the removal of non detrital matter from soils and sediment using uranium isotopes this study was supported by an arc discovery project grant dp1093708 and arc future fellowship ft0990447 to ad and a university of wollongong postgraduate scholarship award to anm

2d multifractal analysis and porosity scaling estimation in lower cretaceous carbonates abstractthe study of scaling porosity in carbonate rocks has great importance because 1 porosity measurements are usually made at scales that are different from the one of interest and 2 carbonate formations contain most of the hydrocarbon reservoirs and aquifers in the world despite these facts scaling porosity in heterogeneous media such as carbonate rocks is still an open problem the heterogeneity of carbonate rocks mainly resides in their complex texture we have extended previous studies on carbonate multifractal behavior in pore space morphology at different scales and we have developed a new equation based in fractal geometry that could be used to scale the porosity in our methodology we 1 perform a multifractal analysis in thin section images of a set of complex carbonate rocks from the lower cretaceous 2 review the effect of magnification in scanning electronic microscope and thin section images 3 deduce a new scaling equation for porosity and finally 4 evaluate this equati

evidence of holocene climatic changes from aeolian deposits in baja california sur mexico abstract well defined late pleistocene and holocene dune fields are present on the surface of the purisima iray magdalena sedimentary basin and on top of barrier islands of the magdalena lagoonal complex in baja california sur mexico thermoluminescence amino acid epimerization and radiocarbon techniques were used for dating dune sands and shell samples respectively during late pleistocene to early holocene 14 to 8 ka bp mega barchans and linear dunes were formed during early holocene through middle holocene warm dry climate dune fields were still active at about 5 to 6 ka bp the stabilization of sea level developed the present lagoonal system in the area sandy barrier islands capped by foredunes were developed at this time coastal dunes were eroded and in part inundated forming large flooding flats and sabkha deposits in the old inter dune areas during late holocene after the lagoonal system was fully developed dunes were emplaced along the lagoonal coasts the presence of some younger dates in older deposits seems to represent dune reactivation

atlantic ocean modulated hydroclimate of the subtropical northeastern mexico since the last glacial maximum and comparison with the southern us abstract proxy records generated from chemical composition and radiocarbon dating of a sediment sequence collected from the el potosi basin provide information about variable hydroclimate of the subtropical northeastern mexico since the last glacial maximum lgm minimal amounts of runoff and more carbonate deposition during 19 ka represent the lgm the deglaciation was wetter compared to the lgm and enhanced runoff during 19 12 ka transported more ti bearing clastics from a relatively humid watershed over the deglaciation the basin received more runoff during the bolling allerod compared to the heinrich stadial 1 and younger dryas reduction in the amount of runoff during 10 1 ka and deposition of unweathered si bearing clastics during 4 1 ka suggest that the holocene was drier compared to the deglaciation hydroclimates of the northeastern mexico and southern us were synchronous during the lgm as well as deglaciation change from the drier lgm to wetter bolling allerod occurred as the gulf of mexico became warmer and the region received more summer precipitation however the dissimilarities observed in regional hydroclimates of the holocene need further evaluation

a holocene record from a former coastal lagoon in bahia kino gulf of california mexico a 10 m long core was recovered from the coastal flood plain on the eastern margin of the gulf of california bahia kino sonora sediments were analysed for loss on ignition magnetic susceptibility pollen diatoms ostracodes and foraminifera three levels were dated by 1 4 c the combined data suggest that the site was flooded during the middle holocene as sea level increased at about 6600 yr bp the area was a freshwater to brackish marsh dominated by typha domingensis and cyperaceae freshwater to brackish conditions suggest the presence of a local source of freshwater during this time and therefore a climate wetter than present continued rise in sea level was associated with an increase in depth and salinity by c 6350 6250 yr bp the coring site was an inner lagoon by c 6125 yr bp a central lagoon and by c 5900 yr bp the site was close to the mouth of the lagoon lower lagoon lower lagoon conditions persisted until the top of the record showing sea level stabilization which was followed by the formation of the dune ridge that presently separates the coring site from the sea

ross ice shelf antarctica in situ radio frequency attenuation we have measured the in situ average electric field attenuation length hli for radio frequency signals broadcast vertically through the ross ice shelf antarctica we chose a location moore embayment south of minna bluff known for its high reflectivity at the ice sea interface we confirmed specular reflection and used the return pulses to measure the average attenuation length from 75 1250 mhz over the round trip distance of 1155 m we find hl i to vary from 500 m at 75 mhz to 300 m at 1250 mhz with an experimental uncertainty of 55 15 m

calcite formation in microbial mats modeling and quantification of inhomogeneous distribution patterns by a cellular automaton model and multifractal measures the evolution of early diagenetic calcite cements in microbial mats of recent supratidal sediments of the southern north sea is modeled in a two dimensional microscale approach by a cellular automaton model cam calcite is traced out in the model by virtual calcium distribution patterns obtained from runs under different assumptions concerning sediment intrinsic conditions for justification of the cam real calcium distribution patterns documented by scanning electron microscopy coupled with energy dispersive x ray spectrometry sem edx are quantitatively compared with the virtual patterns on the basis of multifractal analyses the formation of high magnesian calcite as a consequence of biogenic anaerobic decomposition of organic matter starts at certain initial calcite domains in this stage an inhomogeneous and multifractal calcium distribution is characteristic nearly complete remineralization of organic matter leads to monofractal behavior of generalized fractal dimensions db q 1 84 the cam results confirm that calcite formation is a self determining morphogenetical process and diffusive transport processes of reactants within the mat affect the biogenic calcite formation

fractal geometry of sedimentary rocks simulation in 3 d using a relaxed bidisperse ballistic deposition model several studies both theoretical and experimental show that sedimentary rocks have a fractal pore grain interface in this paper a computer simulated 3 d sedimentary rock structure generated by the relaxed ballistic bidisperse deposition model rbbdm is investigated to characterize the micro structure of its pores the pore volume and the rock pore interface show the same fractal dimension indicating that the pore volume is a fractal the two point density correlation is computed for the pore space and the results compare favourably with the range reported from experiments an array of 2 d x ray tomography micrograph sections of a real sedimentary rock an oolitic limestone pure calcite from the mondeville formation of middle jurassic age paris basin france was used to generate a 3 d bitmap the 3 d real rock sample generated in this manner was analysed for similar studies as the simulated structure the results were compared with those obtained from simulation the simulation results agree qualitatively with the real rock sample diffusion through the connected pore space of the simulated structure was studied using a random walk algorithm and the results compared with the similar simulation study done on the 3 d oolitic limestone specimen in both cases diffusion was found to be anomalous indicating that the sedimentary rock has a fractal geometry the favourable comparability of results between the simulated and real rock supports the usefulness of the model of sedimentary rock generation which can be applicable to transport phenomena

growth of correlated pore scale structures in sedimentary rocks a dynamical model this report explores statistical models and geochemical observations to determine new insights into the formation of sedimentary rock

fabrics in polar ice sheets development and prediction fabrics in polar ice sheets provide a record of deformational history and control the viscosity of ice during further deformation they affect geophysical sensing of ice sheets and provide an accessible analogue to fabric development during deformation of other geological and engineering materials a new synthesis of experimental and theoretical results shows that c axis fabrics are quantitatively related to cumulative strain and stress state in ice sheets for the full range of likely flow patterns basal shear divergent flow and parallel flow cause c axes to rotate toward the vertical axis whereas convergent flow causes c axes to rotate toward a vertical plane transverse to flow

fractal analysis of tight shaly sandstones using nuclear magnetic resonance measurements assessing quantitatively the microscopic pore structures of porous rocks including irregularities of pore shapes and pore size distributions is becoming one of the most challenging efforts nuclear magnetic resonance nmr measurements were used to provide insights into the pore geometry pore size and shape and pore connectivity of the chang 7 tight shaly sandstones in situ permeability 0 1 md in ordos basin the incremental transverse relaxation time t2 distributions for the 100 brine saturated samples display unimodal and bimodal behaviors presenting a geometrical arrangement composed of small to large pore size domains the nmr parameters such as bulk volume irreducible bvi capillary and clay bound water free fluid index ffi movable water the value of t2 separating the bvi from ffi the amplitude weighted mean on a logarithmic scale t2gm and the value of t2 that shows the highest frequency on the t2 spectrum t2peak for each sample were determined then the fractal theory was adopted to quantitatively express the complexity and heterogeneity of the sandstones the results show that only minor primary intergranular porosity remains and variable amounts of micropores and secondary intragranular porosity with poor connectivity occur in the chang 7 tight shaly sandstones assuming spherical pores a new model to calculate the fractal dimension of pore structure from the nmr t2 distributions is proposed the fractal dimensions of all the samples are calculated and the accuracy of the proposed model is verified by the regression coefficients the microscopic pore structures are heterogeneous in these tight sandstones according to the high value of fractal dimensions micropores are the primary causes of heterogeneity in tight sandstones and samples with unimodal t2 distribution behaviors and high content of short components have the highest fractal dimension and heterogeneity the calculated fractal dimension is strongly correlated with t2peak and t2gm therefore the fractal model proposed in this study can be used to calculate the fractal dimensions and evaluate the heterogeneities of the porous rocks satisfactorily the fractal model proposed in this study helps to quantitatively assess the pore structures of tight sandstones using nmr measurements

organic nanopore structure and fractal characteristics of wufeng and lower member of longmaxi shales in southeastern sichuan china abstract organic nanopores in shale gas reservoirs are the main storage space for free gas and adsorbed gas and directly affect the occurrence mode and movement of shale gas in this study field emission scanning electron microscopy fe sem low pressure gas n2 and co2 adsorption and mercury injection capillary pressure micp analyses were performed and interpreted with statistical and fractal analyses to investigate the organic pore structure in the upper ordovician wufeng shale o3w and the lower silurian lower member of longmaxi shale s1l it was found that organic pores in 15 samples from 8 layers of the wufeng longmaxi shale section are usually developed in discrete organic matter particles organic matter associated with clay minerals and organic matter associated with pyrite framboids the size shape and quantity of organic pores vary greatly the organic pores in wufeng formation layer 1 are densely developed in organic matter particles with relatively small sizes and irregular shapes the organic pores in the lower part of the lower member of longmaxi formation layers 3 4 and 5 are less developed and have relatively larger pore sizes with an elliptical shape in contrast the organic pores in the upper part of the lower member of longmaxi formation layers 6 7 8 and 9 are the least developed with elliptical shapes and pore sizes in between the two cases above a higher value of fractal dimension refers a more complex form and this value of whole organic pores with full range of sizes dwop is the largest and followed by organic macropores dop 50 organic pores with pore sizes between 4 nm and 50 nm dop4 50 and organic pores with pore sizes less than 4 nm dop

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

response of the north american monsoon to regional changes in ocean surface temperature 1 the north american monsoon nam an onshore wind shift occurring between july and september has evolved in character during the holocene largely due to changes in northern hemisphere insolation published paleoproxy and modeling studies suggest that prior to 8000 cal years bp the nam affected a broader region than today extending westward into the mojave desert of california holocene proxy sst records from the gulf of california goc and the adjacent pacific provide constraints for this changing nam climatology prior to 8000 cal years bp lower goc ssts would not have fueled northward surges of tropical moisture up the goc which presently contribute most of the monsoon precipitation to the western nam region during the early holocene the north pacific high was further north and ssts in the california current off baja california were warmer allowing monsoonal moisture flow from the subtropical pacific to take a more direct northwesterly trajectory into an expanded area of the southwestern u s west of 114 w a new upwelling record off southwest baja california reveals that enhanced upwelling in the california current beginning at 7500 cal year bp may have triggered a change in nam climatology focusing the geographic expression of nam in the southwest usa into its modern core region east of 114 w in arizona and new mexico holocene proxy precipitation records from the southwestern u s and northwestern mexico including lakes vegetation pollen and caves are reviewed and found to be largely supportive of this hypothesis of changing holocene nam climatology

potential mechanisms for anisotropy in ice penetrating radar data radar data center frequency 150 mhz collected on the antarctic plateau near the epica deep drilling site in dronning maud land vary systematically in backscattered power depending on the azimuth antenna orientation backscatter extrema are aligned with the principal directions of surface strain rates and change with depth in the upper 900 m backscatter is strongest when the antenna polarization is aligned in the direction of maximal compression while below 900m the maxima shift by 90 pointing towards the lateral flow dilatation we investigate the backscatter from elongated air bubbles and a vertically varying crystal orientation fabric cof using different scattering models in combination with ice core data we hypothesize that short scale variations in cof are the primary mechanism for the observed anisotropy and the 900m boundary between the two regimes is caused by ice with varying impurity content observations of this kind allow the deduction of cof variations with depth and are potentially also suited to map the transition between holocene and glacial ice

flow law hypotheses for ice sheet modeling ice flow modeling requires a flow law relating strain rates to stresses in situ but a flow law cannot be measured directly in ice sheets microscopic processes such as dislocation glide and boundary diffusion control both the flow law for ice and the development of physical properties such as grain size and c axis fabric these microscopic processes can be inferred from observations of the physical properties and the flow law can then be estimated from the microscopic processes a review of available literature shows that this approach can be imperfectly successful interior regions of large ice sheets probably have depth varying flow law constants with the stress exponent n for power law creep less than 3 in upper regions and equal to 3 only in deep ice n probably equals 3 through most of the thickness of ice shelves and ice streams

complex resistivity of synthetic sulphide bearing rocks the complex resistivity of synthetic samples has been measured over the frequency range 0 01 hz to 1 0 mhz the synthetic samples were made of a quartz matrix and sulphide particles grain sizes volume fractions and sulphide particles of different nature were used the samples were saturated to different degrees with different types of electrolyte the results obtained were used to check the validity of the theoretical electrochemical model developed by wong 1979 this model fits the experimental data reasonably well in the frequency range where the dispersion and the phase maxima occur against the model expectations the experiment did not duplicate the debye form of spectra because most of the common metals are oxidized to the ionic form and an electrochemical charge transfer reaction occurs at the interface the model prediction regarding the effect of the distribution of the grain radii on the complex resistivity could not be duplicated experimentally

an enhanced role for the tropical pacific on the humid pleistocene holocene transition in southwestern north america abstract climate effects on landscape evolution during the late pleistocene holocene transition 14 6 8 ka in southwestern north america traditionally are linked to the activity of the north american monsoon and to vegetation change related to a decrease in winter precipitation acting in response to orbital cyclicity we performed an integrated analysis of regional alluvial fan lacustrine and paleobotanical records for the area comparing them with hemispheric and regional paleoclimate proxies our focus was on the potential role the tropical pacific has as a synoptic pattern modulator and moisture source for hydrogeomorphic activity in the region our analysis indicates that the onset of alluvial fan aggradation in most of the region at 13 5 ka could have been a response to semi permanent el nino like conditions in the tropical pacific which enhanced the frequency of winter frontal storms as well as increased penetration of tropical cyclones in the region the north american monsoon was restricted in extent and intensity until 7 ka and probably was not a major factor in alluvial fan aggradation a second stage of alluvial fan aggradation from 11 5 to 9 ka was dominated by hyper concentrated flows and sheet flood sedimentation along with deposition in fluvial settings storms were probably were linked to landfall of enhanced water vapor bands in the leading edge of winter extra tropical cyclones with moisture advected directly from the tropical pacific at 8 ka favorable conditions for the occurrence of these storms waned and storm tracks shifted northward analysis of modern analogs for storm types described above as prevalent during this period indicates that changes in circulation patterns across the tropical pacific can affect storm properties enough to explain the observed geomorphic effects regardless of other factors traditionally considered of large impact like vegetation change our results suggest that the tropical pacific plays a larger role than currently thought in landscape evolution of the region

pore structure and fractal analysis of lower carboniferous carbonate reservoirs in the marsel area chu sarysu basin abstract evaluation of carbonate heterogeneity closely related to pore geometry and connectivity is important in oil and gas field production and reservoir prediction to profoundly understand the heterogeneity of lower carboniferous carbonate reservoirs in the marsel area including visean c1v and serpukhovian c1sr the pore structure and fractal characteristics are investigated using routine petrophysical measurements x ray diffraction xrd cast thin section analysis scanning electron microscopy sem and mercury injection capillary pressure micp tests the origin of potentially prolific reservoir the relationships between fractal dimension and reservoir physical properties mineral composition and pore structure are also discussed xrd results reveal that the mineral compositions are highly heterogeneous in c1v and c1sr routine petrophysical experiments indicate that c1v and c1sr are generally tight however some high porosity permeability zones exist in c1sr which is described as a potentially prolific reservoir the cast thin section and sem analyses identify three main pore types in the potentially prolific reservoir interparticle dissolution pores intercrystalline dissolution pores and moldic pores the micp data reflect that the pore throat radii in the prolific reservoir range from 0 29 to 4 6 m whereas those in tight section are typically

electrical properties of artificial clay bearing sandstone rocks which contain clay minerals often display electrical properties which cannot be predicted by bulk electrical properties of the constituents cohen 1981 interactions between clay minerals and groundwater can produce polarization phenomena decreases in resistivity and supposed nonlinear behavior