phanerozoic evolution of the basins of northern egypt and adjacent areas the results of integrating geological well data and geophysical information from the subsurface of northern egypt are presented in terms of basin dynamics recent biostratigraphic data from wells and scarce outcrops are shown to be critical to an understanding of syndepositional tectonics six tectonostratigraphic phases of basin evolution are recognized to span the phanerozoic these phases initially record the development of intracratonic subsidence controlled by deep crustal strike slip tectonics as nubian continental and tethyan marine influences competed across the northern margin of gondwanaland evidence is also presented for the formation of the present day continental margin to northern egypt after a phase of crustal stretching oceanic rifting focused on the western margin of the arabian platform propagating progressively westwards during the early mid jurassic thereafter the effects of passive subsidence on the continental margin were disturbed by discrete phases of intracratonic strike slip associated syrian arc folding and the formation of deep basins in the opening red sea and gulf of suez three structural fabrics persisted throughout phanerozoic basin evolution the result of repeated extensional reactivation and inheritance from pan african basement

sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

influence of water column anoxia and sediment supply on the burial and preservation of organic carbon in marine shales abstract previous work has suggested that the laminated organic rich and bioturbated organic poor shales of the camp run member of the late devonian early mississippian new albany shale formed under anoxic and oxygenated bottomwater conditions respectively and that the interbedding of the two facies was due to the vertical oscillation of a water column anoxic oxic boundary where it impinged on the basin margin we have extended this analysis by examining the chemical and mineralogical differences between the two shale facies in a single borehole core by seeking evidence for deposition of the laminated shales under bottom water oxia or anoxia and by determining whether the laminated shales formed when the carbon supply to the sea floor was higher the results of this study show that the laminated and bioturbated shales are mineralogically and chemically distinct relative to al an index of the aluminosilicate content si ti fe p na ba co cr cu mo ni v zn and zr are all higher whereas mn ca mg and sr are lower in the laminated compared with the bioturbated shales the differences are due to a higher quartz feldspar titanite ilmenite and zircon content in the laminated shales probably indicating a coarser grain size and the greater abundance of manganoan calcite in the bioturbated shales dissolved oxygen was present in bottom waters during the deposition of some of the laminated shale intervals because of the presence of manganoan calcite a phase that can only form in sediments with an oxic surface in addition the organic matter preserved in the two shale types is isotopically different 13corganic values are 1 9z permil lighter on average in the laminated compared with bioturbated intervals possibly indicating a larger fraction of terrestrial organic matter in the latter 15n values are 1 9z permil lighter on average in laminated compared with bioturbated intervals possibly indicating a larger fraction of terrestrial organic matter in the latter 15n values are 1 9z permil lighter on average in laminated compared with bioturbated intervals suggesting that nutrient drawdown was less during the deposition of the organic rich laminated shales the chemical mineralogical and isotopic contrasts between the two shale facies of the camp run member indicate that the conditions of sedimentation were different during their deposition the difference was possibly related to variations in sea level which would have caused the camp run shoreline to move closer to and farther from the core site causing in turn the deposition of coarser and finer grained sediments that contained different mixtures of marine and terrestrial organic matter bottomwater conditions were anoxic during deposition of most laminated intervals bottom water anoxia or dysoxia led to decreased burial and preservation of the essential nutrient phosphorus in the laminated organic rich shales relative to the rocks deposited beneath better oxygenated bottomwaters increased availability of phosphorus in the water column on long timescales leads to increased productivity and a higher settling flux of organic matter causing bottom water oxygen levels to fall this is consistent with the nitrogen isotope evidence suggesting that production was probably higher during the deposition of the organic rich shales thus production variations coupled with enhanced sedimentary regeneration of phosphorus from sediments related to low oxygen bottom water concentrations provide a general mechanism for the formation of the alternating facies of this member of the new albany shale

on the role of closed and open boundaries in a model of the tropical atlantic ocean abstract a series of model experiments of the tropical atlantic ocean is performed to demonstrate the effect of various closed and open boundary configurations on spinup and steady state time sclaes in response to forcing by idealized winds and a realistic seasonal cycle the large scale interior solutions are relatively insensitive to the choice of boundary condition however the choice of boundary condition does have an important impact on the structure and variability of the western boundary circulation and its relation to the interior flow field as expected transient effects during spinup produced significant differences in western boundary coastal upwelling and downwelling regimes based on the implementation of closed or open boundaries more importantly the mere existence of certain western boundary features such as coastally trapped jet was strongly dependent on the choice of boundaries under mean and seasonal equilibrium conditions in particular only those solutions with an open western bou

comparative study of organic matter preservation in immature sediments along the continental margins of peru and oman part i results of petrographical and bulk geochemical data abstract detailed petrographical and bulk geochemical investigations of organic matter om have been performed on sediments deposited below or close to upwelling areas offshore peru odp leg 112 sites 679 681 688 and oman odp leg 117 sites 720 723 724 in order to obtain a quantitative understanding of its accumulation and degradation microscopical as well as nanoscopical investigations reveal that the om in sediments affected by upwelling mechanisms mainly up to 98 consists of unstructured amorphous organic aggregates without any apparent biological structures in sediments which are not or to a lesser extent affected by upwelling site 720 terrestrial om predominates organic carbon toc contents are highly variable and range between 9 8 in sediments deposited below upwelling cells and 0 2 in sediments outside the upwelling zone the toc sulphur ratios of the sediments scatter widely the samples from the deep water locations sites 688 and 720 show c s ratios of normal marine sediments whereas at the other locations no correlation or even a negative correlation between sulphur and toc concentration exists in most of the upwelling influenced sediments om contains a significant amount of sulphur the incorporation of sulphur into the om followed microbial sulphate reduction and occurred in the upper meters of the sedimentary column below om is still present in vast amounts and relatively hydrogen rich but is nevertheless non metabolizable and becomes the limiting factor for bacterial sulphate reduction according to mass balance calculations 90 99 of the om produced in the photic zone was remineralized and 1 3 was consumed by microbial sulphate reduction the aerobic and anaerobic processes have greatly affected degradation and conservation of om

early diagenetic alteration of organic matter by sulfate reduction in quaternary sediments from the northeastern arabian sea abstract hemipelagic sediments from the northeastern arabian sea off pakistan were analyzed by geochemical and microscopical methods to study the importance of bacterial degradation processes on the quantity and composition of sedimentary organic matter om on the basis of elemental analysis of total organic carbon toc and total sulfur ts the decay of om by sulfate reducing bacteria were calculated concentrations of total iron reactive iron total nitrogen tn total phosphorus tp and hydrogen indices hi were used to assess organic matter reactivity and redox conditions stable sulfur isotopic compositions provided further information about pathway timing and mechanisms of sulfate reduction microscopical observations indicate that throughout the study area om is amorphous 75 95 in almost all samples with only a small contribution of terrigenous om bacterially mediated sulfate reduction leads to continuously decreasing toc ts ratios from 0 4 m to a burial depth of 2 3 m at this depth the anaerobic oxidation of particulate organic matter ceases sulfate reduction in this narrow interval accounts for the decay of up to 70 of the om which has primarily entered the anoxic domain during the bacterially mediated diagenesis preferential consumption of nitrogen and phosphorus containing organic compounds can be observed and quantified the regeneration of up to 60 of tn and more than 50 of tp can lead to a feedback of nutrients to the seawater this recycling process may contribute to the high productivity in the northeastern arabian sea

complete archive of late turonian to early campanian sedimentary deposition in newly drilled cores from the tarfaya basin sw morocco an expanded succession of organic rich marlstones and limestones deposited in the tarfaya basin provides an outstanding opportunity to closely retrace climate evolution and sea level changes during the cretaceous greenhouse period we present high resolution x ray fluorescence xrf scanning and bulk carbon and oxygen isotope records from two newly drilled sediment cores in the tarfaya atlantic coastal basin which recovered a continuous upper turonian to campanian succession of 290 m thickness the xrf core scanning records reveal three long term oscillations in the abundance of terrigenous elements increase of al ti k si and fe normalized against ca which correspond to progressive transgressive phases followed by rapid regressions during the coniacian and early santonian sea level highstands during this interval corresponding to the coniacian santonian oceanic anoxic event 3 oae 3 are characterized by overall oxygen depleted to anoxic conditions at the seafloor indicated by the high organic carbon content the presence of laminations and low log mn s high log v ca and high log br ca the upper santonian interval marks the transition from anoxic to oxic bottom water conditions prevalent through the early campanian the composite bulk carbonate 13 c curve exhibits strong similarities to the global stacked 13 c reference curve characterized by negative excursions in the early coniacian navigation and east cliff events and late santonian bracketed by the haven brow and buckle events and by positive excursions in the latest turonian hitchwood event middle coniacian wight fall event and at the santonian campanian boundary during the early campanian enhanced accumulation of fine grained carbonate and clay rich hemipelagic sediments increasing bulk carbonate 18 o and low log br ca and log v ca values indicate climate cooling associated with a substantial improvement in bottom water ventilation two long term 13 c cycles of 2 m y duration probably related to variations in earth s orbital eccentricity are associated with the long term cooling trend initiating the campanian maastrichtian climate transition toward a cool greenhouse state

depositional and organic carbon controlled regimes during the coniacian santonian event first results from the southern tethys egypt abstract geochemical and palynological proxies were determined for 31 samples representing the upper coniacian lowermost campanian abu roash a member collected from the bed2 3 well this was done to assess the prevailing paleoredox conditions productivity levels and water column settings to 1 understand controls and mechanisms related to accumulation of organic carbon within the sedimentary record 2 assess principal environmental processes that triggered the preservation of organic matter poor calcareous shale and limestone facies of the abo roash a member and 3 to interpret the paleoceanographic settings and confirm the occurrence of either oceanic anoxic event 3 oae3 or cretaceous oceanic red beds corbs within the abu gharadig basin in the southern part of the tethyan ocean egypt sedimentation rates were reconstructed based on the biostratigraphic age constraints of marine dinoflagellate cysts dinocysts trace elements based ratios and relationships were used in order to study the role of clastic terrestrial input three groups of dinocysts and freshwater pediastrum algae were used to study the water column conditions results showed that the abu roash a member was deposited under oxic to intermittently dysoxic conditions in a distal inner to middle neritic environment with varying sedimentation rates from 32 to 119 mm kyr 1 productivity appeared to be a significant factor for determining magnitudes of the organic carbon accumulation however low productivity was prevalent during deposition carbonate content was high which resulted in dilution of organic matter during varied rates of sediment input such results indicate that the paleoceanographic conditions in the southern tethys witnessed the absence of prevalent oceanic anoxia i e the coniacian santonian oae 3 and deposition of the corbs as in several parts of the tethys the pacific and the indian oceans

hydrocarbon potential and depositional paleoenvironment of a middle jurassic succession in the falak 21 well shushan basin egypt integrated palynological geochemical and organic petrographic approach abstract the topmost lower and middle jurassic formations of organic rich clastics with minor carbonate deposits were recognized as very significant source reservoir rocks in the north western desert of egypt although several studies are devoted to their source rock characteristics and petroleum potential the depositional paleoenvironment and paleoredox conditions are still poorly understood in the current study these sediments were assessed in terms of their organic matter richness hydrocarbon generative potential and thermal maturity total sulfur ts contents and organic petrographic characteristics depositional paleoenvironment was investigated using dinoflagellate cysts dinocysts and the composition of particulate organic matter along with organic petrographic characteristics redox conditions were assessed based on ts total organic carbon toc relationship and type of kerogen that was derived mainly from palynofacies analysis toc contents show fair to excellent generative potential of hydrocarbons mainly of kerogen type iii gas prone the thermal maturity based on tmax and rr indicates mature stage of oil window palynological analysis yielded poor to rich intervals of moderately preserved biostratigraphically useful dinocysts in the upper part of the khatatba formation an assemblage of 81 species belonging to 54 genera of moderately diverse dinocysts spores and pollen grains was identified freshwater algae acritarchs and microforaminiferal test linings are sporadically documented within the studied interval based on the first downhole appearance fda of the recovered marker dinocyts the upper part of the khatatba formation was palynologically dated as late bathonian callovian the depositional environment was interpreted and three environments were deduced the lower interval representing the topmost ras qattara and yakout red shale member was deposited in a fluvial lacustrine environment where oxic conditions prevailed as deduced from the color of reddish brown sandstone and red shale the middle interval spans unit iib kabrit and unit iii which accumulated in a deltaic to shallow marine environment under dysoxic suboxic settings the upper interval covers unit i and unit iia that have been deposited in a fluvio deltaic to shallow marine with high paleoproductivity under suboxic conditions one sample in the upper interval in unit iia reflected anoxic setting

n2 fixing cyanobacteria supplied nutrient n for cretaceous oceanic anoxic events the abundance of specific membrane lipids 2 methylhopanoids indicates that cyanobacteria played a key role in the seemingly global deposition of black shales during the early aptian ca 120 5 ma and late cenomanian ca 93 5 ma oceanic anoxic events organic matter rich sediments deposited during these events are characterized by a 15n content typical of newly fixed n2 indicating that cyanobacterial n2 fixation was the main source for nutrient n we propose that denitrification and anaerobic ammonium oxidation effectively cut off the return of nutrient n from the anoxic deep waters to the photic zone in the oceans giving n2 fixing cyanobacteria a competitive advantage over algae during these oceanic anoxic events

deformation and surface uplift associated with serpentinization at mid ocean ridges and subduction zones 1 we employ the classical problem of an inclusion in an elastic half space to model effects of sub surface serpentinization on crustal deformation change of stress state and surface uplift at the tag hydrothermal field on the mid atlantic ridge the model suggests that an anomalous salient 3 km in diameter and 100 m high that projects 3 5 km westward from the east valley wall may have resulted from a relatively deep seated well serpentinized body exhibiting transformational strain the associated large strains would likely result in sub surface fracturing or faulting but surface uplift may be relatively insensitive to the exact depth and shape of the serpentinized region serpentinization of a region beneath the footwall of the tag detachment fault will tend to promote slip along some overlying normal faults which may then enhance fluid pathways to the deeper crust to continue the serpentinization process our solution for the miyazaki plain above the kyushu palau subduction zone in sw japan explains the observed uplift of 120 m the small transformational strains associated with serpentinization in this region may promote thrust type events in the aseismic slip zone near the upper boundary of the subducting philippine sea plate as well as intraplate earthquakes associated with normal faulting the rate of serpentinization needed to produce the observed uplift at the miyazaki plain is significantly greater than that needed at tag though significantly smaller on per unit volume basis thermal effects of serpentinization in both regions appear to be small but uplift data provide an additional constraint on inferring serpentinization from geological and seismological observations

source rock potential and paleoenvironment of the miocene rudeis and kareem formations gulf of suez egypt an integrated palynofacies and organic geochemical approach abstract a study on source rock characterization and paleoenvironmental interpretation has been carried out on a relatively thick miocene sedimentary succession from three wells gh 404 2a gh 420 1 sa e6a in the southern gulf of suez egypt the compilation of detailed optical investigations including palynofacies analysis spore coloration index sci vitrinite reflectance vrr and source rock geochemical data enables a detailed evaluation of organic matter om richness kerogen type and thermal maturation level despite their high content of calcium carbonate up to 52 the studied sediments yielded sufficient palynologic residue for a detailed palynofacies and organic petrographic study the palynomorph content comprises mainly marine components essentially dinoflagellate cysts and accessorily microforaminiferal linings while terrestrial derived material is relatively rare persistent occurrence of amorphous organic matter aom indicates that dysoxic to anoxic conditions prevailed throughout the deposition of the investigated sediments the main objective of this study is to combine organic geochemical and palynological data in an attempt to assess the source rock potential of the rudeis and kareem formations in the gulf of suez these data in addition also allow for the reconstruction of the depositional environment the present investigation employs multimode microscopic methods using transmitted white light along with incident light fluorescence microscopy for the first time geochemical and petrographic analyses performed on bulk rock samples and palynological residues demonstrate that both the rudeis formation and the kareem formation are mainly of kerogen type iii or mixed type ii iii independent thermal maturation specific parameters such as rock eval tmax vrr and sci indicate an immature to early mature stage palynofacies analyses combined with organic geochemical data indicate that the rudeis formation was deposited under shallow to open marine conditions whereas the overlying kareem formation was formed mainly in an open marine setting

geochemical and petrographic characterization of campanian lower maastrichtian calcareous petroleum source rocks of hasbayya south lebanon abstract santonian paleocene marls and fine grained carbonates have been sampled in hasbayya locality south lebanon in order to evaluate their organic matter om content petroleum source rock potential and assess their depositional environment methods included total organic carbon toc total inorganic carbon tic total sulphur ts rock eval pyrolysis organic and inorganic petrography x ray fluorescence xrf gas chromatography mass spectrometry gc ms and curie point pyrolysis gas chromatography mass spectrometry cp py gc ms toc rock eval and vitrinite reflectance vrr results reveal excellent immature petroleum source rocks within the campanian lower maastrichtian interval with toc up to 11 6 wt hydrogen index hi up to 872 mg gtoc tmax up to 433 c and vrr average of 0 36 biomarker ratios and maceral analysis suggest a marine depositional environment with a dominance of algal as well as submicroscopic om original sediment composition and redox sensitive geochemical parameters suggest deposition of the om rich intervals under an oxygen minimum zone omz that was emplaced and controlled by primary productivity and nutrient supply pyrolysate composition shows an important content of organic sulphur compounds thiophenes increasing with toc and thus indicating the presence of type ii and type iis kerogen in the analysed sample set which is consistent with the presence of immature solid bitumen in the hasbayya region the data produced in this study coupled with regional correlations allow us to construct a conceptual depositional model for the upper cretaceous om rich rocks of the eastern mediterranean suggesting deposition under a productivity belt localized along the inner and outer shelf leading to a decrease in source rock quality and a shift in kerogen type toward the deeper parts of the levant basin

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

three dimensional mechanical models for the june 2000 earthquake sequence in the south iceland seismic zone abstract a sequence of earthquakes including two m w 6 5 events occurred in june 2000 in an atypical transform zone located in the southwest of iceland the inter co and post seismic time intervals of the associated deformation cycle have been well recorded by previous geodetic studies including gps and insar using a numerical code based on a finite element method we analyze the influence of structural and rheologic heterogeneities on the earthquake deformation cycle within the south iceland seismic zone sisz the co seismic deformation is especially sensitive to the increase of lithospheric stiffness with depth as shown by a joint inversion of the geodetic data the estimated distribution of co seismic slip for the june 21 mainshock is deeper when estimated in a realistic layered lithospheric model than in a homogenous half space the geometry of the rheologic layers also plays an important role during the post seismic interval when several inter related processes poro elastic effects around the fault plane afterslip in it and or visco elastic relaxation in the lower crust and or upper mantle appear to occur on overlapping time and length scales we also consider the seismicity both in its contribution to stress transfer and in its tendency to migrate from east to west at least six processes may be involved in changing the stress distribution 1 propagation of seismic waves 2 changes of static stress caused by major co seismic slip 3 cascading seismicity 4 fluctuations in hydrological conditions 5 ductile flow of subcrustal rocks and 6 inter seismic strain accumulation all six of these phenomena occurred in the sisz before during and after the june 2000 earthquake sequence by using three dimensional finite element models with realistic geometric and rheologic configurations to match the observations we test the influence of the increase of rigidity with depth and the variable crustal thickness on processes 2 3 5 and 6 inter seismic strain 6 accumulating in an elastic upper crust that thickens eastward can produce an asymmetric stress distribution this process may explain the tendency of subsequent earthquakes to migrate from east to west across the south iceland seismic zone within a single sequence yet it cannot explain their timing or the location of the first event our modeling with realistic geometric and rheologic configurations suggests that the june 17 earthquake triggered the june 21 event by a combination of several time dependent post seismic processes

habitat of oil in abu gharadig and faiyum basins western desert egypt the abu gharadig and faiyum basins are areas which have some of the greatest hydrocarbon potential in the western desert of egypt several extensive cycles of marine transgression and regression occurred in these territories through geologic time the depositional cycles combined with at least 3 tectonic cycles 1 the hercynian orogeny at the end of the paleozoic 2 from late jurassic to early tertiary and 3 from late cretaceous to middle tertiary resulted in a highly deformed thick sedimentary sequence this organic rich jurassic upper cretaceous lower tertiary sequence in large areas of these basins was subjected to enough heat and depth to generate hydrocarbons it is evident from recent discoveries that these source rocks generated large amounts of high quali y oil and gas the abu gharadig and faiyum basins are separated structurally by a major ridge both basins are bounded on the north by another major ridge associated with cretaceous and tertiary faulting a major platform with thin sedimentary cover forms the southern boundary the hydrocarbon potential exists in cyclic sequences of sandstone shale and carbonate having moderate porosities and permeabilities an important hydrologic phenomenon prevails in major parts of the basins fresh water has flushed the early cenomanian and older reservoirs the eastern part of the faiyum basin the southern platform the kattaniya high and the southern and western rims of the abu gharadig basin are completely flushed leaving little chance for hydrocarbon preservation in these localities exploration efforts should be concentrated on deep structures close to the main depocenters and inside or very close to the 150 f 65 c geothermal contour contemporaneous structures on the northern rims of the basins should have high potential resulting from migration of hydrocarbons from the south across major faults the jurassic in the northeastern part of the abu gharadig basin may provide good hydrocarbon potential the lower tertiary sequence present in the troughs also may have large amounts of oil entrapped in situ or resulting in short distance migration to the northern structures or to the late cretaceous early tertiary syrian arc traps

sedimentology and characteristics of dispersed organic matter in tertiary niger delta origin of source rocks in a deltaic environment organic matter in tertiary strata of the niger delta is mainly a mixture of types ii and iii kerogen as defined by pyrolysis has a high pristane phytane ratio 1 and is composed of the macerals vitrinite and minor liptinite the main palynofacies are structured woody material opaque organic matter cuticles pollen and spores and minor amorphous organic matter the geochemistry petrology palynofacies and distribution data indicate a predominantly terrestrial and detrital source of the organic matter irrespective of facies formation or age the distribution and abundance of the organic matter are related to both the age of the strata and depositional environment the most significant variation is the decline in mean total organic carbon toc content from late eocene 2 2 toc to pliocene strata 90 toc and an associated general decline in pyrolysis defined hydrogen index hi and pristane phytane ratio the decrease in toc and hi in younger strata reflects increased dilution of a nearly constant supply of terrestrial organic matter with the generally higher sedimentation rates of younger strata a simple linear dilution model accounts for about 50 of the variance in measured toc the low pristane phytane ratio of younger strata may reflect less oxidizing depositional conditions the variation in organic matter with depositional environments and environmental depth zones defined by foraminiferal assemblages is significant although less important than variation due to age the highest toc and hi values occur in nonmarine swamp marsh and floodplain deposits reflecting proximity to the organic source beach barrier and offshore bar facies have lower toc and hi values due to selective winnowing of organic matter and greater oxidation from continental to transition marine depth zones a marked decline in toc and hi occurs as a result of dilution selective transport and oxidation of the organic matter from transitional to bathyal depth zones little variation is found in toc but a general increase is found in hi which reflects a relative increase in more hydrogen rich autochthonous organic matter in all facies autochthonous organic matter comprises less than 20 of the toc no interpretable variation appears in maceral or palynofacies abundance with sediment type which probably reflects the homogeneity of the organic matter paradoxically no rich source rocks occur in the tertiary succession in the niger delta and as conventionally measured the strata have little or no oil generating potential the poor quality of the source rocks has been more than compensated for by their great volume by the excellent migration routes provided by interbedded permeable sands and possibly by the relatively rapid rate of maturation niger delta type of source rock although an end member in terms of general source rock composition appears to be relatively typical of tertiary deltas

senonian basin inversion and rejuvenation of rifting in africa and arabia synthesis and implications to plate scale tectonics abstract the late paleozoic to tertiary stratigraphic record of much of the african plate reflects the effects of continental rifting and passive margin development several short lived but widespread and tectonically important compressional or wrench dominated events occurred however during the permian to recent evolution of africa we focus here on the best documented of these events which occurred during the late santonian at that time older sedimentary basins mostly ene wsw trending were folded and inverted including some basins along the tethyan margin from morocco to the syrian arc and the intraplate benue southern chad basins and the lugh mandera basin in oman ophiolites were obducted following the santonian tectonism an extensive phase of rifting occurred in central and north africa and northern arabia spanning from campanian to maastrichtian or paleocene times rejuvenation or acceleration of subsidence occurred in several basins located along the tethyan margin along the atlantic and indian ocean margins as well as within the intraplate domain rifting was sometimes accompanied by magmatic activity especially in offshore northern libya and along the indian ocean margin compressional deformations rejuvenated or developed by latest maastrichtian times along the tethyan margin and locally within the intraplate domain one of the most remarkable attributes of the santonian tectonic event which we consider representative of the major trans african stress field changes is the rapidity with which the change was reflected stratigraphically across north and central africa and its short duration the cause of the santonian compressional event is directly linked to the change in poles of rotation for the opening of the atlantic at 83 85 ma the end of the cretaceous normal magnetic quiet zone this was also synchronous with the obduction of ophiolites along the northeast margin of arabia oman the onset of separation between india and madagascar with formation of the mascarene oceanic basin and the development of the european alpine chain we interpret these phenomena as causally related aspects of a global tectonic event the santonian compressional event as well as the campanian maastrichtian rifting event and the end cretaceous compressional event illustrate the critical connection between intraplate tectonic histories and processes occurring at sometimes very distant plate boundaries

depositional environment thermal maturity and shale oil potential of the cretaceous qingshankou formation in the eastern changling sag songliao basin china an integrated organic and inorganic geochemistry approach abstract the changling sag in the petroliferous songliao basin has produced large amounts of conventional petroleum but studies on unconventional resources are rare a suite of core samples from the cy 1 well drilled in the eastern changling sag was analysed employing a series of micropetrographic geochemical and pyrolysis techniques to reveal the shale oil potential of the lower k2qn1 and middle k2qn2 qingshankou formation in this area for the first time from the lower k2qn1 upwards the sampled section the ratio of k al delineates an increasing palaeo temperature trend but still within a warm climate based on element ratios al2o3 toc and tio2 toc the highest terrestrial matter and nutrient supply on average occurred in the lower k2qn1 triggering bioproductivity toc ts and fe mn show that bottom water anoxia prevailed in the upper k2qn1 and lower k2qn2 providing excellent conditions for organic matter om preservation as compared to the lower k2qn1 high maturity of the studied layers is implied by e g vitrinite reflectance vrr of 1 03 1 09 tmax values over 445 c and molecular organic geochemical indices which correlate very well with vrr kinetic data on petroleum generation from open system pyrolysis were implemented in a numerical 1d basin and petroleum system model the k2qn1 has generated and expelled large amounts of petroleum 78 and 36 transformation of kerogen to petroleum based on kinetics of the low mature qingshankou shale om consisted originally of type i ii kerogen but has lost more than half of its original hydrocarbon generation potential upon maturation oil saturation index osi and s1 suggest that the studied layers show fair shale oil potential but are regarded as good conventional petroleum source rocks a newly proposed shale oil potential index sopi takes also thickness into account application to the qingshankou formation implies that the lower k2qn2 holds the highest shale oil potential

simple kinetic models of petroleum formation part i oil and gas generation from kerogen modern basin analysis uses kinetic models to predict the extent of petroleum generation within potential source rocks the global kinetic model presented here assigns kinetic parameters based on gross depositional environment and stratigraphic age this is useful in areas of low geochemical knowledge including exploration frontiers five kerogen kinetic organofacies each characterized by a specific organic matter input and early diagenetic overprint can broadly be related to sedimentary facies age associations even using seismic sequence stratigraphy alone a aquatic marine siliceous or carbonate evaporite any age b aquatic marine siliciclastic any age c aquatic non marine lacustrine phanerozoic d e terrigenous non marine ever wet coastal mesozoic and younger and f terrigenous non marine coastal late palaeozoic and younger routine pyrolysis data allow partitioning of organic carbon in the immature source rock into four initial components oil oil generative gas generative and inert separate kinetic parameters for the oil and gas generative fractions allow computation of the evolving concentration and composition of the products it was assumed that the activation energy distributions for each fraction were normally distributed non linear regression of large combined laboratory and field data sets varying by up to 12 orders of magnitude in heating rate established optimum values for the required ten 5 2 kinetic parameter sets a emean e differences in kinetic parameters can be reconciled with known chemical properties although our knowledge base is still inadequate to construct kinetic models from first principles mean activation energies governing oil generation increase systematically in the order a f causing a corresponding increase in generation temperature at a reference heating rate 2 c ma 1 the oil generation window 10 90 oil generative kerogen degraded increases from ca 95 135 c to 145 175 c organofacies c has the tightest energy distribution and narrowest oil generation window the gas generation window ranges from ca 105 155 c to 175 220 c thermal stress results from a combination of temperature and time an order of magnitude increase decrease in heating rate elevates depresses reaction temperatures by ca 15 c heating rates in subsiding sedimentary basins can vary by two orders of magnitude dramatic differences in generation temperature can result if the heating rate and organofacies effects compound thus global oil and gas generation temperature thresholds constitute blunt instruments with which to screen the petroleum potential of sedimentary basins because unexpelled oil provides a potential feedstock for oil to gas cracking in the source rock quantitative models of petroleum generation become really useful only when coupled with models of oil gas cracking and expulsion for example the frequently observed association between gas provinces and coals cannot be explained solely by their generation behaviour

late cretaceous late turonian coniacian and santonian petroleum source rocks as part of an oae tarfaya basin morocco abstract late turonian coniacian and santonian source rock samples from a recently drilled well tafaya sondage no 2 2010 in the tarfaya basin were analyzed for quantity quality maturity and depositional environment of the organic matter om to our knowledge such a thick sequence of organic matter rich turonian to santonian source rocks was investigated in that great detail for the first time organic geochemical and organic petrological investigations were carried out on a large sample set from the 200 m thick sequence in total 195 core samples were analyzed for total organic carbon corg total inorganic carbon contents and total sulfur ts contents rock eval pyrolysis and vitrinite reflectance measurements were performed on 28 samples chosen on the basis of their corg content non aromatic hydrocarbons were analyzed on selected samples by way of gas chromatography flame ionization detection gc fid and gc mass spectrometry gc ms the organic matter rich carbonates revealed a high source rock potential representing type i kerogen and a good preservation of the organic matter which is mainly of marine phytoplankton origin hi values are high 400 900 mg g corg and in a similar range as those described for more recent upwelling sediments along the continental slope of north africa ts corg ratios as well as pristane over phytane ratios indicate variable oxygen content during sediment deposition all samples are clearly immature with respect to petroleum generation which is supported by maturity parameters such as vitrinite reflectance 0 3 0 4 tmax values 401 423 c production indices s1 s1 s2 0 1 as well as maturity parameters based on ratios of specific steranes and hopanes

redox sensitivity of p cycling during marine black shale formation dynamics of sulfidic and anoxic non sulfidic bottom waters abstract a high resolution geochemical record of a 120 cm black shale interval deposited during the coniacian santonian oceanic anoxic event 3 odp leg 207 site 1261 demerara rise has been constructed to provide detailed insight into rapid changes in deep ocean and sediment paleo redox conditions high contents of organic matter sulfur and redox sensitive trace metals cd mo v zn as well as continuous lamination point to deposition under consistently oxygen free and largely sulfidic bottom water conditions however rapid and cyclic changes in deep ocean redox are documented by short term 15 20 ka intervals with decreased total organic carbon toc s and redox sensitive trace metal contents and in particular pronounced phosphorus peaks up to 2 5 wt p associated with elevated fe oxide contents sequential iron and phosphate extractions confirm that p is dominantly bound to iron oxides and incorporated into authigenic apatite preservation of this fe p coupling in an otherwise sulfidic depositional environment as indicated by fe speciation and high amounts of sulfurized organic matter may be unexpected and provides evidence for temporarily non sulfidic bottom waters however there is no evidence for deposition under oxic conditions instead sulfidic conditions were punctuated by periods of anoxic non sulfidic bottom waters during these periods phosphate was effectively scavenged during precipitation of iron oxyhydr oxides in the upper water column and was subsequently deposited and largely preserved at the sea floor after 15 25 ka sulfidic bottom water conditions were re established leading to the initial precipitation of cds zns and pyrite subsequently increasing concentrations of h2s in the water column led to extensive formation of sulfurized organic matter which effectively scavenged particle reactive mo complexes thiomolybdates at site 1261 sulfidic bottom waters lasted for 90 100 ka followed by another period of anoxic non sulfidic conditions lasting for 15 20 ka the observed cyclicity at the lower end of the redox scale may have been triggered by repeated incursions of more oxygenated surface to mid waters from the south atlantic resulting in a lowering of the oxic anoxic chemocline in the water column alternatively sea water sulfate might have been stripped by long lasting high rates of sulfate reduction removing the ultimate source for hs production

the cenomanian turonian oceanic anoxic event in the razzak field north western desert egypt source rock potential and paleoenvironmental association abstract the western desert of egypt is one of the world s most prolific jurassic and cretaceous hydrocarbon provinces it is one of many basins that experienced organic rich sedimentation during the late cenomanian early turonian referred to as oceanic anoxic event 2 oae2 the razzak 7 oil well in the razzak field in the northern part of the western desert encountered the upper cretaceous abu roash formation this study analyzed 23 samples from the upper g f and lower e members of the abu roash formation for palynomorphs particulate organic matter total organic carbon toc and 13corg in order to identify the oae2 determine hydrocarbon source rock potential and interpret the depositional environment the studied samples are generally poor in palynomorphs but show a marked biofacies change between the lower e member and the rest of the studied samples palynofacies analysis kerogen quality and quantity indicates the presence of oil and gas prone materials kerogen types i and ii iii respectively and implies reducing marine paleoenvironmental conditions detailed carbon stable isotopic and organic carbon analyses indicate that fluctuations in the 13corg profile across the abu roash upper g f and lower e members correspond well with changes in toc values a positive 13corg excursion 2 01 believed to mark the short term global oae2 was identified within the organic rich shaly limestone in the basal part of the abu roash f member this excursion also coincides with the peak toc measurement 24 61 wt in the samples

climate and tectonic driven deposition of sandwiched continental shale units new insights from petrology geochemistry and integrated provenance analyses the western sichuan subsiding basin southwest china abstract how the depositional setting efficiently governs the characteristic sandwiched continental shale units remains uncertain which restricts an integrated assessment of organic rich fluvio lacustrine shale reservoirs and accurate estimation of potential natural gas resources here we present new results from petrological observations element geochemical fingerprinting and integrated analyses of heavy mineral basinal subsidence history and sandstone stratum ratio on typical and terrigenous sandwiched like depositional systems of the targeted upper triassic xujiahe formation in the western sichuan subsiding bain southwest china in view of the representative and environment sensitive indices we suggest that passive continental margin and continental island arc dominated by granite to granodiorite source are the major tectonic settings of the provenance and both a more warm humid climate characterized by intensified chemical weathering conditions and a calm tectonically quiescent setting are identified as two major drivers forcing the accumulation and preservation of organic matter in organic rich continental shale units finally a comprehensive depositional model is established for providing new insights into the linkage between palaeoclimatic conditions tectonic pulses and terrigenous clastic sedimentation both the cyclic palaeoclimate fluctuations and episodic tectonic activities are believed to have exerted a very considerable force on development of the unique sandwiched like stratigraphic framework and the coupling interactions between the tectono climatic evolution and fine grained sedimentation are thus also stressed

depositional history source rock quality and thermal maturity of upper ordovician lower silurian organic rich sedimentary rocks in the central part of the baltic basin lithuania abstract this study provides a comprehensive geochemical and mineralogical characterisation of the fine grained organic matter rich sedimentary rocks of the lower palaeozoic in the central part of the baltic basin western lithuania the primary objective was to deduce environmental conditions for the lower palaeozoic succession which is very well preserved in the baltic basin while the secondary goal was to obtain information on maturation and thermal history of the rocks the sample set covers different stratigraphic units of the ordovician lower silurian succession and was analysed with a wide range of different methods including elemental analysis organic petrography rock eval pyrolysis molecular geochemical analysis of saturated and aromatic hydrocarbon fractions inorganic geochemistry mineralogy xrf xrd analysis and magnetic susceptibility ms of rock samples their integration allowed a determination of the redox conditions paleoproductivity and clastic input during sediment deposition the fine grained sediments are dominated by clay minerals and quartz and to a lesser extent carbonate pyrite and feldspar microscopic analysis revealed abundant solid bitumen and zooclasts biomarker data indicate a marine origin for the precursor organic matter maturity parameters revealed the presence of a thermal maturity anomaly in the southwestern part of lithuania where the late phase of oil generation and possibly beginning of condensate wet gas generation with corresponding maximum paleotemperatures of 140 180 c has been reached bottom water conditions varied from oxic to anoxic euxinic during deposition driven by interaction of climate states water mass circulation and stratification water geochemistry and sea bottom bathymetry four shaly horizons at the upper ordovician fjacka and mossen fms silurian dobele fm and near llandovery wenlock boundary levels were recognized as being formed in oxygen depleted benthic settings as indicated by high toc and ts contents sedimentation features high metal enrichment or degree of piritization the deposition of highly organic matter rich silurian dobele fm might have coincided with oceanic anoxia and late aeronian bioevent accompanied by an upwelling regime with increased paleoproductivity the interpreted coarsening upward trend at the early silurian adavere regional stage terminates with fall in relative sea level at the llandovery wenlock boundary the geochemical proxies near llandovery wenlock boundary may reflect the perturbations in oceanic water geochemistry which in turn may have eventually led to ireviken mass extinction event

palynological palynofacies paleoenvironmental and organic geochemical studies on the upper cretaceous succession of the gptsw 7 well north western desert egypt abstract the present study of the abu roash and bahariya formations in well gptsw 7 refines our understanding of the subsurface cretaceous of the north western desert of egypt our investigations are based on the palynological analyses of 71 cuttings samples of which 24 have also been analyzed for geochemistry in addition to 3 sidewall cores analyzed for vitrinite reflectance r o four palynological zones and three subzones in addition to a poorly fossiliferous interval ranging in age from coniacian santonian to early cenomanian are proposed these include a poorly fossiliferous interval coniacian santonian dinogymnium vozzhennikovae interval zone late to middle turonian ephedripites ambiguus ephedripites multicostatus foveotricolpites giganteus foveotricolpites gigantoreticultus assemblage zone early turonian classopollis brasiliensis interval zone late to middle cenomanian and afropollis jardinus interval zone early cenomanian the succeeding subzones are afropollis kahramanensis interval subzone elaterosporites klaszii interval subzone and cretacaeiporites densimurus interval subzone all of early cenomanian age total organic carbon toc and rock eval pyrolysis and palynofacies analyses indicate that the bahariya formation and the abu roash g member are primarily of kerogen iii type and hence gas prone suggesting a strong influence of hydrogen enriched organic matter the abu roash a c e members may also be gas prone type iii kerogen and appear to contain highly oxidized terrestrial organic matter in contrast the abu roash f member has very high toc and hi values and contains a very high proportion of amorphous organic matter aom indicating a highly oil prone facies while this finding is not unexpected for anoxic black shale it contrasts with earlier studies that suggest a gas prone nature r o measurements show that the bahariya formation represents an immature early genesis dry gas phase this is also true for all investigated samples from the abu roash and bahariya formations based on their low thermal alteration index tai quantitative and qualitative analyses of both the palynoflora and palynofacies show that the abu roash a and c members b is missing both of coniacian santonian age represent oxic proximal and distal shelf environment the abu roash d and e members dated as turonian represent oxic proximal shelf whereas the cenomanian abu roash f member was deposited in a distal suboxic anoxic basin the cenomanian abu roash g member and the bahariya formation were deposited in a shallow marine and shallow marine to fluvio deltaic setting respectively the senonian palmae province is recognized in the palynoflora by the presence of proteacidites auriculiidites reticulatus ariadnaesporites gabonisporis vigourouxii on the other hand the albian cenomanian elaterates province is characterized by the presence of steevesipollenites gnetaceaepollenites elaterocolpites elaterosporites elateroplicites senegalosporites sofrepites afropollis and cretacaeiporites

application of biological markers in the recognition of the geochemical characteristics of some crude oils from abu gharadig basin north western desert egypt abstract the objective of this study is to establish the relationship between the hydrocarbons recovered from the abu gharadig basin and middle jurassic khatatba formation as well as the previously established upper cretaceous abu roash f member a suite of fourteen crude oil and condensate samples from the mesozoic reservoirs jurassic cretaceous of the abu gharadig basin western desert egypt was analyzed and geochemically compared with extracts from source rocks of the middle jurassic khatatba formation and the upper cretaceous abu roash f member based on molecular indicators of organic source input depositional environment and age diagnostic biomarkers at least two petroleum systems operate in the abu gharadig basin those derived from late cretaceous marine shales and jurassic early cretaceous non marine organic rich shales as source rocks and possibly a third system appears to be a mixture of them both the correlation of some abu gharadig oils to a late cretaceous source establishes a petroleum system involving these marine cretaceous source rocks

organic geochemical characteristics and interpreted depositional environment of the khatatba formation northern western desert egypt the middle jurassic khatatba formation in the northern western desert of egypt was evaluated in terms of organic matter abundance type and thermal maturity as well as for some organic petrographic characteristics depositional environments were interpreted based on organic geochemical rock eval pyrolysis extract analysis and biomarker distributions and organic petrological methods organic carbon contents range between 1 0 and 32 5 wt the khatatba shale and coaly shale samples have hydrogen index values in the range of 63 to 261 mg hydrocarbon hc g total organic carbon with mixed types 2 3 and 3 kerogens mean vitrinite reflectance ro between 0 77 and 1 07 is in reasonably good agreement with pyrolysis tmax temperature at maximum of s2 peak data 438 459c organic rich sediments of the middle jurassic khatatba formation have very good source rock generative potential and have obtained thermal maturity levels equivalent to the oil window the main generation products are gas with very limited liquid hcs oil or condensate seven shale and coaly shale samples from khatatba formation were characterized using gas chromatography gc and gc mass spectrometry techniques the khatatba samples are characterized by the predominance of c14 c24 alkanes a pristane phytane ratio of less than 2 abundant c27 regular steranes and the presence of tricyclic terpanes these are consistent with the suboxic marine environment conditions for the khatatba source rock biomarker parameters for these samples generally indicate a mixture of land as well as marine derived organic matter input the maturity indicators based on c32 22s 22s 22r homohopane and c29 20s 20s 20r and sterane ratios reveal that the khatatba samples are thermally mature and have reached the peak oil window maturity supporting the ro data

geochemistry and time series analyses of orbitally forced upper cretaceous marl limestone rhythmites lehrte west syncline northern germany a cyclic marl limestone succession of middle late campanian age has been investigated with respect to a milankovitch controlled origin of geochemical data in general the major element geochemistry of the marl limestone rhythmites can be explained by a simple two component mixing model with the end members calcium carbonate and average shale like material carbonate content varies from 55 to 90 non carbonate components are clay minerals illite smectite and biogenic silica from sponge spicules as well as authigenically formed zeolites strontian heulandite and quartz the redox potential suggests oxidizing conditions throughout the section trace element and stable isotopic data as well as sem investigations show that the carbonate mud is mostly composed of low magnesium calcitic tests of planktic coccolithophorids and calcareous dinoflagellate cysts calcispheres diagenetic overprint results in a decrease of 2 18 o and an increase in mn of up to 250 ppm however the sediment seems to preserve most of its high sr content compared to the primary low magnesium calcite of co occurring belemnite rostra the periodicity of geochemical cycles is dominated by 413 ka and weak signals between 51 and 22 5 ka attributable to orbital forcing accumulation rates within these cycles vary between 40 and 50 m ma the resulting cyclic sedimentary sequence is the product of a changes in primary production of low magnesium calcitic biogenic material in surface waters within the long eccentricity and the precession demonstrated by the caco 3 content and the mg al mn al and sr al ratios and b fluctuations in climate and continental weathering which changed the quality of supplied clay minerals the illite smectite ratio demonstrated by the k al ratio high carbonate productivity correlates with smectite favouring weathering semi arid conditions conspicuously dry and moist seasonal changes in warmer climates ti as the proxy indicator for the detrital terrigenous influx as well as rb si zr and na shows only low frequency signals indicating nearly constant rates of supply throughout the more or less pure pelagic carbonate deposition of the long lasting third order middle upper campanian sedimentary cycle

source rock potential and depositional environment of upper cretaceous sedimentary rocks abu gharadig basin western desert egypt an integrated palynological organic and inorganic geochemical study abstract the abu gharadig basin in the northern part of the western desert egypt is among the most important petroleum provinces in egypt here cenomanian to santonian rocks of bahariya formation and abu roash a g members from the gpt 3 well were investigated for their depositional environment kerogen quality petroleum generation potential and thermal maturity by geochemical petrological and palynological methods the sediments of the bahariya and abu roash formations excluding the abu roash f member represent variable shallow marine environments with poor preservation of marine organic matter whereas there is an excellent preservation in the abu roash f member the basal part of this member is characterized by anoxic carbonate rich depositional conditions high toc values up to 7 high hi up to 700 mghc gtoc and liptinite dominated organic matter depletion of iron leads to sulfur incorporation into organic matter which is reflected in high thiophene benzene ratios above sediments are enriched in terrestrial elements fe ti as well as k and mn this pattern and the occurrence of the fresh brackish water algae botryococcus suggests a regression phase during deposition the upper part of the abu roash f member is again characterized by fully marine suboxic conditions and a lower thiophene benzene ratio the source rock section demonstrates lower thermal maturity compared to the above and below sections based on all microscopic pyrolysis and biomarker data this indicates thermal maturity retardation suppression most likely due to a different organic facies and early diagenetic transformation of kerogen as indicated by the geochemical and palynological data the source rock heterogeneity indicates a relatively shallow marine environment where the changes in bottom water conditions are very sensitive to sea level fluctuations residual oil characterization reveals two reservoir compartments which are in the abu roash d and c members the abu roash f source rocks are compared with time equivalent sediments in the tarfaya basin in morocco which represent more distal settings the more proximal group a is characterized by s fe ratios between 0 57 and 0 67 indicating suboxic conditions it has toc and hi values not exceeding 4 and 600 mghc gtoc respectively at variable caco3 contents the more distal tarfaya sediments group b have higher toc and hi as well as high organic sulfur contents group a is higher in terrigenous element concentrations the tmax of immature source rocks ranges from 410 to 415 c in organic sulfur rich samples and from 420 to 430 c in organic sulfur poor samples revealing an important impact of organic facies on maturity parameters furthermore there is an inverse relationship between s fe and al2o3 toc which might become an important tool in paleoenvironmental reconstructions as well as petroleum source rock studies

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

poroelastic stress triggering of the 2005 m8 7 nias earthquake by the 2004 m9 2 sumatra andaman earthquake abstract the m9 2 sumatra andaman earthquake sae occurred three months prior to the m8 7 nias earthquake ne we propose that the ne was mechanically triggered by the sae and that poroelastic effects were a major component of this triggering this study uses 3d finite element models fems of the sumatra andaman subduction zone sasz to predict the deformation stress and pore pressure fields of the sae the coseismic slip distribution for the sae is calibrated to near field gps data using fem generated green s functions and linear inverse methods the calibrated fem is then used to predict the postseismic poroelastic contribution to stress triggering along the rupture surface of the ne which is adjacent to the southern margin of the sae the coseismic deformation of the sae combined with the rheologic configuration of the sasz produces two transient fluid flow regimes having separate time constants sae coseismic pore pressures in the relatively shallow forearc and volcanic arc regions within a few km depth dissipate within one month after the sae however pore pressures in the oceanic crust of the down going slab persist several months after the sae predictions suggest that the sae initially induced mpa scale negative pore pressure near the hypocenter of the ne this pore pressure slowly recovered increased during the three month interval separating the sae and ne due to lateral migration of pore fluids driven by coseismic pressure gradients within the subducting oceanic crust because pore pressure is a fundamental component of coulomb stress the mpa scale increase in pore pressure significantly decreased stability of the ne fault during the three month interval after the sae and prior to rupture of the ne a complete analysis of stress triggering due to the sae must include a poroelastic component failure to include poroelastic mechanics will lead to an incomplete model that cannot account for the time interval between the sae and ne our transient poroelastic model explains both the spatial and temporal characteristics of triggering of the ne by the sae