trace metal signatures of eastern mediterranean sapropels abstract sapropel samples of pliocene to pleistocene age recovered during odp leg 160 from sites 964 ionian basin 969 mediterranean ridge 966 967 top and northern slope of the eratosthenes seamount south of cyprus and 968 cyprus margin were analysed for major and trace elements eastern mediterranean sapropels are characterized by high organic carbon and sulphur contents and by significant enrichments in several redox sensitive and or sulphide forming trace metals bi cd co cr cu mo ni re sb tl u v enrichment factors relative to average shale are comparable to those found in ctbe black shales the re content is extremely high in the sapropels studied with maximum values up to 1000 ng g re mo ratios averaging 2 7 10 3 are close to the seawater value high trace metal enrichments and re mo ratios close to the seawater value point to an anoxic water column during sapropel formation additionally enhanced ba concentrations in the sapropels support the assumption that bioproductivity was also high during these episodes trace metal signatures of sapropels originating from different drill sites on a transect across the eastern mediterranean are not only influenced by water depth but also by their location in the eastern mediterranean metal enrichments seem to be higher at the western sites compared with the eastern sites this probably reflects a change in the circulation pattern during periods of sapropel formation pliocene sapropels exhibit elevated trace metal contents in comparison with pleistocene examples therefore different palaeoceanographic conditions may have developed during the pleistocene compared with the pliocene altering palaeoceanography was probably controlled by climatic change which may be related to the onset of glaciation of the northern hemisphere decreasing summer precipitation throughout the late pliocene and the pleistocene may also have influenced sapropel deposition

present day stress orientations adjacent to active strike slip faults california and sumatra present day stress directions interpreted from well bore breakouts adjacent to two crastal scale active strike slip faults the san andreas fault in california and the great sumatran fault in sumatra indicate that the maximum horizontal stress direction sh is oriented at a high angle 70 90 to both faults the regionally defined stress fields spanning these faults show that adjacent young or actively growing folds have formed orthogonal to sh and are therefore in the thrust fault orientation these observations indicate a decoupling of the strike slip and compressional components of the deformation within these broadly transpressive zones borehole breakouts in 118 wells in western california indicate a regionally consistent stress pattern with sh generally oriented ne sw nearly perpendicular 80 90 to the strike of the san andreas fault the orientation of sh nearly perpendicular to the san andreas fault implies low shear stress on the fault and is consistent with geological interpretations of the coast and transverse ranges indicating active compressional deformation fault plane solutions for recent dip slip style earthquakes principal stress directions determined from inversion of earthquake focal mechanisms and induced hydraulic fracture orientations a stress trajectory map for western california is computed using an iterative statistical algorithm in which observed directional data such as breakout directions are used to obtain a model regional stress field analysis of well bore breakouts in 25 wells within the central and southern oil districts of sumatra indicates that the regionally defined sh adjacent to the active great sumatran strike slip fault is oriented at a high angle 70 80 to the fault this orientation of sh is consistent regionally with geologic stress indicators and focal mechanisms of dip slip earthquakes preliminary analysis of the stress field in the vicinity of the philippine and alpine faults suggests sh is also oriented at a high angle to these active strike slip faults similarly the minimum horizontal stress sh is oriented at a high angle to the the kane and dead sea transforms the observation of sh and sh in the vicinity of active strike slip faults being oriented nearly perpendicular and parallel to the faults suggests that large crustal scale strike slip faults may in general be inherently weak surfaces

new u th pb constraints on timing of shearing and long term slip rate on the karakorum fault 1 zircons and monazites from 6 samples of the north ayilari dextral shear zone nasz part of the karakorum fault zone kfz have been dated with the u th pb method using both id tims and sims techniques the ages reveal 1 inheritance from several events spanning a long period between the late archean and the jurassic 2 an eocene oligocene magmatic event similar to 35 32 ma 3 an oligo miocene magmatic event similar to 25 22 ma at least partly synkinematic to the right lateral deformation and 4 a period of metamorphism metasomatism similar to 22 14 ma interpreted as thermal and fluid advection in the shear zone the labhar kangri granite located similar to 375 km farther southeast along the kfz is dated at 21 1 0 3 ma such occurrence of several oligo miocene granites along the kfz some of which show evidence for synkinematic emplacement suggests that the fault zone played an important role in the genesis and or collection of crustal melts we discuss several scenarios for the onset and propagation of the kfz and offset estimates based on the main sutures zones our preferred scenario is an oligo miocene initiation of the fault close to the na range and propagation along most of its length prior to similar to 19 ma in its southern half the averaged long term fault rate of the kfz is greater than 8 to 10 mm a in good agreement with some shorter term estimates based on the indus river course or quaternary moraines and geodesy our results show the kfz cannot be considered as a small transient fault but played a major role in the collision history

relationship between tectonism and volcanism along the great sumatran fault zone deduced by spot image analyses abstract satellite images provide evidence for numerous stepovers pull apart grabens and volcanic structures along the nw trending right lateral great sumatran fault zone high resolution spot images permit us to analyze the relationship between volcanic and tectonic structures this analysis reveals that releasing stepovers and pull aparts are ephemeral structures along the great sumatran fault zone and that the geometry of the strike slip fault evolves permanently through time the interpretative structural maps obtained from spot image analysis reveal that the formation of huge peculiarly shaped volcanic calderas has occurred in large releasing stepover fault zones and that the bounding faults of rectangular pull apart basins are analogous to the circular ring faults of calderas in particular detailed study of the segments at the southernmost 150 km long termination of the great sumatran fault zone from northwest of ranau lake to semangka bay allows us to describe the development of the ranau collapse caldera this caldera is located within a pull apart basin bounded by a stepover its peculiar rectangular shape and its relatively large size about 200 km 2 are controlled by the evolution of the extinct ranau releasing stepover similarly the toba elliptical caldera one of the largest volcanic caldera in the world is elongated parallel to the present trace of the great sumatran fault and appears to be related to a releasing stepover associated with a wide pull apart basin that is not active at present

displacement features associated with fault zones a comparison between observed examples and experimental models abstract fault zones commonly consist of discontinuous surfaces or are composed of different kinds of en echelon fractures tension cracks r or p type fractures which give the brittle shear zone a width translation along these faults and related features can occur by sliding on the elementary planes and or by solution deposition processes with opening of transtension zones and possible dilatation of the shear zone in order to understand how fault planes develop and to investigate the mechanical conditions corresponding to natural configurations displacement along an analogue fault model was examined under conditions of direct shear the experimental fracture patterns were then compared with the natural features the structural elements of certain faults created by testing and showing transpression and transtension zones were found to be similar to natural domino structures bounded by elementary shears and could be compared with computed situations it can be inferred that stresses are reoriented inside the shear zone the angle between elementary fractures depends on their order of development transpression and transtension zones occur systematically and the shear zone undergoes dilatancy under low normal stresses

design and application of a constant head well permeameter for shallow high saturated hydraulic conductivity soils a new constant head well permeameter has been designed to measure saturated hydraulic conductivities ks ranging from 10 6 to 10 3 ms 1 application to shallow soils of western australia in this ks range highlighted problems with different aspects of the borehole discharge response firstly steady state borehole discharge was only reached in 13 out of 50 tests conducted this was a consequence of the constraint placed on the volume of water storage 40 l of the permeameter for some non steady state cases techniques of estimating steady state discharge from the available data are examined secondly borehole discharge was observed to increase with time in 34 per cent of cases a satisfactory physical explanation of this phenomenon is not presently available other limitations in the application of the constant head well permeameter are noted examination of a number of recent theoretical developments in the determination of ks led to a preference of saturated unsaturated flow solutions by philip 1985 and reynolds et al 1985 these solutions involve the sorptive number to which the solutions were sensitive but not critically sensitive the theory was used to establish design criteria for the permeameter and to identify an optimum application strategy in terms of well dimensions and heads error estimation indicated that the designed permeameter was a practically useful field instrument

evidence for extreme variations in the permeability of laterite from a detailed analysis of well behaviour in nigeria laterite soils are widespread in tropical africa and have a large impact on the hydrology of the areas they cover the permeability of laterite helps determine the partitioning of runoff and interflow and regulates groundwater recharge to underlying bedrock groundwater within laterite also forms a widespread source of drinking water typically from unimproved hang dug wells despite its importance there is little published information on laterite aquifer properties in this study data from a 6 m deep well in nigeria have been analysed to characterise the hydraulic conductivity of the laterite from repeated pumping tests transmissivity measurements from 40 tests spread out across a hydrological year varied from 0 1 to 1000 m2 d further interpretation of the data demonstrate a strong non linear decrease in horizontal hydraulic conductivity with depth characterised by an upper horizon of extreme permeability 400 m d and a much lower permeability profile beneath 0 1 m d these data are substantiated with observations from other wells throughout the area this non linear permeability structure has several implications the upper laterite can facilitate rapid lateral throughflow in the wet season enabling contaminants to be transported significant distances up to 1 km natural groundwater levels are restricted to a narrow range for much of the year and in the dry season the lower permeability of the deeper laterite restricts the amount of water which can be abstracted from shallow wells leading to well failure the work highlights the need for a wider study to better understand laterite soils and the role they play in regional hydrology 2013 natural environment research council hydrological processes published by john wiley sons ltd

the trace metal content of recent organic carbon rich sediments implications for cretaceous black shale formation organic carbon rich sediments are enriched in several redox sensitive and stable sulfide forming trace metals tm and form an important sink in global tm cycles in today s ocean such sediments are deposited in coastal upwelling areas like those in the gulf of california off peru or off the namibian coast and euxinic basins like the black sea in an attempt to distinguish both environments by their specific tm patterns some important conclusions may be drawn 1 the tm enrichment seen in both environments broadly is rather similar 2 upwelling sediments are often enriched in cd and p and depleted in co and mn 3 sapropels have a tendency towards higher enrichments in ba and mo s re as cu ni sb and fe reflecting the strong sulfidation in an anoxic water column 4 upwelling systems cover a broad range of environmental settings where the steepness of the slope the proximity of h2s to the sediment seawater interface and the intensity of bio accumulation and regeneration play an important role for tm accumulation 5 the tm content of anoxic basins is mainly controlled by tm availability in the water column and sedimentation rate 6 enhanced bio productivity is the main switch turning an oxygenated into an anoxic environment cretaceous black shales oae 2 exhibit tm signatures of both coastal upwelling areas and sapropels the strong enrichments in cd mo tl v cu ni bi and sb demonstrate that bio accumulation and presence of h2s in the water column and associated sulfidation processes persisted during this time interval in large parts of the proto atlantic the usefulness of ba as a paleoproductivity proxy is obscured by diagenesis the extreme accumulation in ag and zn requires either an additional tm source for instance hydrothermal input or a different tm seawater composition during the cretaceous the geochemical data suggest that the major driving force for the widespread occurrence of c t black shales seems to be the increase in volcanic activity and associated co2 input throughout the cretaceous the ocean atmosphere system operated in a mode different from today during this time interval after conversion of the nutrient co2 into organic matter the system switched back into the normal operational mode

barium peaks at glacial terminations in sediments of the equatorial atlantic ocean relicts of deglacial productivity pulses in sediment cores recovered from oligotrophic settings of the western and eastern north equatorial atlantic ocean ceara rise and sierra leone rise distinct peaks of excess barium were detected at glacial interglacial transitions these ba maxima are unrelated to any other potential productivity proxy e g organic carbon carbonate or opal moreover they coincide with minima in organic carbon contents despite the lack of correlation between excess barium and organic carbon we ascribe these ba spikes to pulses of productivity that occurred during glacial interglacial transitions the discrepancy between barium and organic carbon in these transitional sediment intervals is attributed to the action of downward progressing oxidation fronts during deglacial nonsteady state depositional conditions the oxidation fronts were initiated due to the overall low sedimentation rates prevailing in the study areas and an increase in bottom water oxygen concentrations at the onset of enhanced nadw production during interglacial periods the fronts led to a very efficient oxidation of the organic carbon initially present leaving peaks in solid phase barium as relicts of these short time productivity events this assumption is supported by the depth arrangement of the solid phase peaks of ba fe and mn along the 6 5 oxygen isotope stage boundary in sediments of the ceara rise which show striking similarities to the distribution of these elements in oxidized sapropel intervals in eastern mediterranean sediments it remains unclear whether productivity was proportional to the magnitude of the baexcess maxima possibly higher dissolved ba concentrations in intermediate and deep waters during glacial interglacial transitions caused the precipitation of barite to increase out of proportion of the postulated deglacial productivity pulses

the paleoclimatic interpretation of clay minerals in sediments a review abstract the application of paleoclimatic interpretation to clay minerals from continental and marine sediments is reviewed and the advantages of this method are indicated levels relatively rich in chlorite illite palygorskite and quartz are interpreted as corresponding to relatively dry periods while more humid periods lead to more intensive weathering and consequently to the dominance of clay minerals more advanced in the relative stability scale such as kaolinite smectite is taken to indicate a climate with contrasting seasons and a pronounced dry season using this and similar schemes the paleoclimates of areas adjoining the mediterranean basin north sea north atlantic southern arctic equatorial and north west pacific and north phillipine sea are reconstructed clay minerals in sediments particularly marine sediments can be useful indicators of paleoclimatic conditions while they do not produce direct indications of climatic parameters they provide integrated records of overall climatic impact occasionally they may be superior to the more conventional paleoclimatic methods such as pollen or oxygen isotope analysis the limitations imposed on the paleoclimatic interpretation of clay minerals in sediments are discussed on the basis of examples the distinction between authigenic and detrital clay minerals is shown to be problematic particularly with regard to smectite the relationship between climatic parameters and clay mineral formation is complicated by the intervention of extra climatic factors such as topography geomorphology lithology and time post depositional diagenetic changes may not be recognized differentiation during transport due to size sorting or differential flocculation may overlap climate induced differentiation the association of clay mineral assemblages with specific source areas presents difficulties due to dispersal pathways that are affected by type of transport agency i e water ice or wind transport agencies are not constant with time by an interdisciplinary approach with the paleoclimatic information derived from clay minerals being correlated with that obtained from the analysis of microfossils and oxygen isotope data many of these limitations can be overcome

sequestration of 12c in the deep ocean during the early wenlock silurian positive carbon isotope excursion abstract marine carbonates from three biostratigraphically well dated silurian sections from the mid continent of north america were analyzed for carbon isotopic 13 c carb study the early wenlock positive carbon isotope excursion ireviken excursion is recorded in three sections from tennessee iowa and ohio with values of 4 5 this global shift in the carbon isotopic ratio of marine waters began during a protracted extinction event ireviken event that spanned the llandovery wenlock boundary although several oceanographic models have been developed to account for the coincident changes in lithology biology and carbon isotope stratigraphy during this interval of the silurian their proposed causal connections among glaciation oceanography primary productivity and the global carbon cycle remain a matter of debate this investigation provides carbon isotopic and lithologic evidence that the ireviken excursion occurred during a time of relatively oligotrophic conditions a third order transgressive regressive cycle and increased carbonate production throughout the mid continent of north america the ireviken excursion is recorded in relatively pure carbonate sequences and is immediately preceded by a significant unconformity in each of the measured sections it is proposed that the ireviken excursion was the product of sequestration and burial of 12 c in deep water as a result of altered deep ocean circulation

hydrothermal minerals and microstructures in the silangkitang geothermal field along the great sumatran fault zone sumatra indonesia detailed study of core samples of silicic tuff recovered from three geothermal wells along the strike slip great sumatran fault zone near silangkitang north sumatra supports a model for enhanced hydrothermal circulation adjacent to this major plate boundary fault two wells a and c were drilled nearly vertically 1 km southwest of the eastern i e the principal fault trace and the third directional well b was drilled eastward from the site of well a to within 100 m of the principal fault trace the examined core samples come from depths of 1650 2120 m at measured well temperatures of 180 320 c the samples collected near the principal fault trace have the highest temperatures the largest amount of secondary pore space that correlates with high secondary permeability and the most extensive hydrothermal mineral development secondary permeability and the degree of hydrothermal alteration decrease toward the southwestern margin of the fault zone these features indicate episodic localized flow of hot possibly co 2 rich fluids within the fault zone the microstructure populations identified in the core samples correlate to the subsidiary fault patterns typical of strike slip faults the geothermal reservoir appears to be centered on the fault zone with the principal fault strands and adjoining highly fractured and hydrothermally altered rock serving as the main conduits for vertical fluid flow and advective heat transport from deeper magmatic sources

origin sequence stratigraphy and depositional environment of an upper ordovician hirnantian deglacial black shale jordan the upper ordovician succession of jordan was located 60 s less than 100 km from the hirnantian ice sheet margin new graptolite dates indicate glaciation ended in jordan in the late hirnantian persculptus biozone the succession records two glacial advances within the ammar formation and the subsequent deglaciations organic rich black shales batra formation form part of the final deglacial transgressive succession that in filled an existing low stand glacial continental shelf topography the base of the black shale is coincident with the maximum flooding surface during transgression interfluves and sub basin margins were breached and black shale deposition expanded rapidly across the region the top of the black shales coincides with peak highstand the expanding puddle model sensu wignall for black shale deposition adapted for the peri glacial setting provides the best explanation for this sequence of events we propose a hypothesis in which anoxic conditions were initiated beneath the halocline in a salinity stratified water column a fresher surface layer resulted from ice meltwater generated during early deglaciation during the initial stages of marine incursion nutrients in the monimolimnion were isolated from the euphotic zone by the halocline increasing total organic carbon toc and 13corg up section indicates the organic carbon content of the shales was controlled mainly by increasing bioproductivity in the mixolimnion the strakhov model mixolimnion nutrient levels were sustained by a continual and increasing supply of meltwater derived nutrients modulated by obliquity changes in high latitude insolation anoxia was sustained over tens to hundreds of thousands of years the formation of black shales on the north gondwana shelf was little different to those observed in modern black shale environments suggesting that it was the nature of the ordovician seas that pre disposed them to anoxia

lateral variation in slab orientation beneath toba caldera northern sumatra the investigator fracture zone ifz subducts beneath toba caldera the earth s largest quaternary caldera in northern sumatra suggesting a possible relationship between them locations of sub crustal earthquakes based on arrival times of p and s waves at a seismograph network surrounding toba reveal the geometry of the subducted slab and the ifz beneath toba a vertical tear of less than 20 km in the slab across the ifz as previously suggested cannot be ruled out but the large scale geometry of the slab is dominated by a broad bend of slab contours parallel to the concaveseaward indentation of the trench the slab shape is probably a response to the trench curvature can explain the change in trend of the volcanic arc near toba and may cause shallowing of the forearc basin near nias island the decrease in radius of curvature of the slab contours is not accompanied by an observable decrease in dip angle possibly resulting in lateral compressive stress in the slab the high rate of seismicity along the subducted investigator fracture zone that intersects the slab obliquely to its plunge direction is uncommon at subducted fracture zones and is likely caused by such lateral stress in the slab

is the slip rate variation on the great sumatran fault accommodated by fore arc stretching in oblique convergent subduction areas an obliquity increase should produce a slip rate increase on trench parallel strike slip faults and thus the fore arc platelet should be stretched along the great sumatran fault gsf that is associated with the oblique convergent sunda arc a northward increase of the gsf slip rate occurs parallel with the convergence obliquity transpressional back arc deformation accommodates part of the gsf slip rate variation while no significant fore arc stretching is observed the sumatran case shows that oblique convergence may be accommodated by deformation of a 500 km wide zone from the fore arc to the back arc domains

relationships between sliding behavior and internal geometry of laboratory fault zones and some creeping and locked strike slip faults of california abstract moore d e and byerlee j 1992 relationships between sliding behavior and internal geometry of laboratory fault zones and some creeping and locked strike slip faults of california in t mikumo k aki m ohnaka l j ruff and p k p spudich editors earthquake source physics and earthquake precursors tectonophysics 211 305 316 in order to relate fault geometries to sliding behavior maps of recently active breaks within the hayward fault of central california which is characterized by fault creep have been examined and compared to maps of the san andreas fault the patterns of recent breaks of the hayward fault are consistent with those found within the creeping section of the san andreas and they appear to have plausible physical explanations in the findings of laboratory experiments the distinguishing geometric features of the examined locked and creeping faults are 1 p type second order traces predominate over r riedel type traces in creeping sections and 2 r type second order traces make smaller angles to the local fault strike in creeping sections than they do in locked sections two different maps of the hayward fault gave similar results supporting the inference that the patterns identified are basic characteristics of the fault rather than artifacts of a particular mapping procedure p shears predominate over r shears under laboratory conditions that allow dilation within the fault zone in our own experiments p shear development was favored by the generation of excess pore fluid pressures we propose that creep in california faults also is the result of fluid overpressures that are maintained in a low permeability gouge zone and that significantly lower effective stresses thus helping to stabilize slip and producing high values of the ratio p r small r trace angles may also be an indicator of low effective stresses but the evidence for this is not conclusive because other factors can also affect the size of the angles

role of fluids in faulting inferred from stress field signatures the stress orientation signature of weak faults containing high pressure fluids has been observed for segments of the san andreas fault system in southern california the inferred lithostatic fluid pressures extend into the surrounding relatively intact rock in a zone scaling with the width of the interseismic strain accumulation repeated strain related fracturing and crack sealing may have created low permeability barriers that seal fluids into the network of currently active fractures

neotectonics of the sumatran fault indonesia the 1900 km long trench parallel sumatran fault accommodates a significant amount of the right lateral component of oblique convergence between the eurasian and indian australian plates from 10 n to 7 s our detailed map of the fault compiled from topographic maps and stereographic aerial photographs shows that unlike many other great strike slip faults the sumatran fault is highly segmented cross strike width of step overs between the 19 major subaerial segments is commonly many kilometers the influence of these step overs on historical seismic source dimensions suggests that the dimensions of future events will also be influenced by fault geometry geomorphic offsets along the fault range as high as 20 km and may represent the total offset across the fault if this is so other structures must have accommodated much of the dextral component of oblique convergence during the past few million years our analysis of stretching of the forearc region near the southern tip of sumatra constrains the combined dextral slip on the sumatran and mentawai faults to be no more than 100 km in the past few million years the shape and location of the sumatran fault and the active volcanic arc are highly correlated with the shape and character of the underlying subducting oceanic lithosphere nonetheless active volcanic centers of the sumatran volcanic arc have not influenced noticeably the geometry of the active sumatran fault on the basis of its geologic history and pattern of deformation we divide the sumatran plate margin into northern central and southern domains we support previous proposals that the geometry and character of the subducting investigator fracture zone are affecting the shape and evolution of the sumatran fault system within the central domain the southern domain is the most regular the sumatran fault there comprises six right stepping segments this pattern indicates that the overall trend of the fault deviates 4 clockwise from the slip vector between the two blocks it separates the regularity of this section and its association with the portion of the subduction zone that generated the giant m w 9 earthquake of 1833 suggest that a geometrically simple subducting slab results in both simple strike slip faulting and unusually large subduction earthquakes

lower silurian hot shales in north africa and arabia regional distribution and depositional model abstract lowermost silurian organic rich hot shales are the origin of 80 90 of palaeozoic sourced hydrocarbons in north africa and also played a major role in petroleum generation on the arabian peninsula in most cases the shales were deposited directly above upper ordovician peri glacial sandstones during the initial early silurian transgression that was a result of the melting of the late ordovician icecap deposition of the main organic rich shale unit in the north african arabian region was restricted to the earliest silurian rhuddanian stage acuminatus atavus and probably early cyphus graptolite biozones during this short period 1 2 m y a favourable combination of factors existed which led to the development of exceptionally strong oxygen deficiency in the area in most countries of the study area the post rhuddanian silurian shales are organically lean and have not contributed to petroleum generation the distribution and thickness of the basal silurian hot shales have been mapped in detail for the whole north african region using logs from some 300 exploration wells in libya tunisia algeria and morocco in addition all relevant accessible published and unpublished surface and subsurface data of the lower silurian shales in north africa and arabia have been reviewed including sedimentological biostratigraphic and organic geochemical data the lowermost silurian hot shales of northern gondwana are laterally discontinuous and their distribution and thickness were controlled by the early silurian palaeorelief which was shaped mainly by glacial processes of the late ordovician ice age and by pan african and infracambrian compressional and extensional tectonism the thickest and areally most extensive basal silurian organic rich shales in north africa occur in algeria tunisia and western libya while on the arabian peninsula they are most prolific in saudi arabia oman jordan and iraq the hot shales were not deposited in egypt which was a large palaeohigh at that time the depositional model presented may help in better understanding the source potential of the basal silurian shales in less explored regions of north africa and arabia including morocco northern niger and the kufra basin in southeast libya

comparative geometry of the san andreas fault california and laboratory fault zones textural examination of fault gouge deformed in triaxial friction experiments has revealed differences in the orientations of secondary shear sets between the stably sliding and stick slip samples in order to determine whether such differences can be identified in natural faults maps of recently active breaks along the san andreas fault from point arena to cajon pass california were examined to compare the types and orientations of secondary structures mapped in the creeping and locked sections the fault zone was divided into 52 geometrically defined segments of uniform strike which were then grouped into 7 sections 4 straight and 2 curved sections and cholame valley one of the straight sections is the creeping section between san juan bautista and cholame in central california the rest of the sections are locked many of the gross geometric characteristics of the individual segments such as length width and stepover size reflect their position in either a straight or a curved section in contrast with respect to the orientations of the recent breaks within the segments the single creeping section differs from all of the locked sections both straight and curved as follows 1 the traces of recent breaks with a more west ward orientation than the local strike of the fault zone p traces dominate over those with a more northward orientation r traces in the creeping section whereas the opposite relationship holds in the locked sections and 2 the more northward oriented r traces make larger angles to the local strike of the fault zone in the locked sections than in the creeping section the latter result is consistent with the orientations of r shears in our various laboratory samples the former result was unexpected because of the predominance of r shears in most laboratory samples but a small number of samples are analogous to the creeping section in terms of their p shear abundances r shear orientations and sliding behavior the causes of these distinguishing characteristics are not yet understood

evolution of the freshwater ecosystem the fossil record abstract the freshwater ecosystem may be as old as most life although freshwater life is taxonomically impoverished in comparison with marine and terrestrial biotas and ultimately derived from them it cannot be assumed that freshwater communities have necessarily been less complex in the geologic past than they are today although it is clear they have undergone a number of major changes freshwaters contain not only their own ancient and peculiar groups some with ancestries as far back as the middle paleozoic but they have been a theater for adaptive radiation of more recent immigrants from the land or sea and a way station for still other groups that passed through both from sea to land and the reverse this review summarizes first fossil records in freshwaters for many of these organisms and examines the question of the changing complexity of the freshwater ecosystem through time by looking at the fossil record of continental aquatic habitats

infiltration characteristics of a complex lateritic soil profile large infiltration ponds 10 15 m2 were used in conjunction with a ring infiltrometer and a well permeameter to determine the infiltration characteristics of a complex lateritic soil profile in the jarrah eucalyptus marginata forest of western australia simultaneous measurements of soil water content and soil water potential allowed a description of the infiltration and redistribution in the soil profile the infiltration ponds effectively measured the conductivity of a subsurface lateritic duricrust which was found to have a relatively high saturated hydraulic conductivity ks of 2 7 m d 1 despite its apparently massive and extensive nature removal of the topsoil identified large 1 m2 infilled holes penetrating the duricrust over about 6 by area measurements indicated that these large holes had a high ks value 10 m d 1 whereas the remaining duricrust had a lower ks value 2m d 1 these results have implications for probable maximum flood design calculations and assessing the hydrological impact of extensive open cut bauxite mining

late early silurian wenlockian general circulation model generated upwelling graptolitic black shales and organic rich source rocks an accident of plate tectonics through an evolutionary process of plate tectonics the wenlockian physical world was composed of an oceanic northern hemisphere and a mainly continental southern hemisphere dominated by the giant continent of gondwana the high latitude position of gondwana placed much of its extensive margin in the middle latitudes laurentia and baltica occupied an equatorial position siberia and kazakh were to the north the global paleoclimate was created and driven by the diverse paleogeography of the two hemispheres in the model the northern hemisphere is dominated by strong zonality in all seasons in contrast the continental southern hemisphere reacts to wide temperature ranges of summer heating and winter cooling of gondwana the extensively flooded 28000 km margin of gondwana occupied the zone of the southern hemisphere westerlies these westerlies produced intense surface upwelling and by extension of present analogies high primary biologic productivity gondwana s northern margin extended far enough toward the equator that significant winter sea ice did not form in the southern hemisphere this allowed a vertically stratified sea to develop as well as probable dysaerobic and anoxic conditions a high organic flux of marine plankton accumulated on the sea floor where it was subsequently buried and preserved a strong positive correlation exists between upwelling generated by a general circulation model gcm on gondwana s northern margin and the distribution of southern hemisphere basins with source rocks containing types i and ii kerogens

spectral gamma ray characterization of high resolution sequence stratigraphy examples from upper carboniferous fluvio deltaic systems county clare ireland the application of high resolution sequence stratigraphy requires the ability to recognize key surfaces which record fluctuations in relative sea level in sub surface studies gamma ray logs have been used to identify maximum flooding surfaces but their full potential has not been realized gamma ray profiles produced using a portable spectrometer on exposed upper carboniferous fluvio deltaic deposits in western ireland reveal that key surfaces and systems tracts can be characterized more comprehensively and recognized with greater confidence if spectral gamma ray data k u th and their respective ratios are used in conjunction with traditional total count data maximum flooding surfaces can be distinguished from lesser flooding surfaces by a distinctive u peak 5 ppm and low th u ratio 6 laterally correlative interfluves are represented by distinctive palaeosols that can be clearly identified in spectral gamma ray data by their anomalously low k content 17 finally the stacking pattern of parasequence sets can be identified using the trends of th k ratios from sandstones in successive parasequences these results have widespread implications for the recognition of high resolution sequence stratigraphic signatures in the stratigraphic record with particular reference to the subsurface analysis of fluvio deltaic deposits

water depth and diagenetic constraints on the use of barium as a palaeoproductivity indicator sediments underneath the high productivity areas of the coastal upwclling and equatorial divergence zones in the pacific and indian oceans are enriched in barium and on this basis the barium content of the sediments has long been suggested as a potential palaeoproductivity indicator analyses of sediments from the peru margin corroborate the pattern of enhanced barium accumulation in areas of high primary productivity in the deep ocean but also show that this pattern cannot be extended to shallow water deposits sediments from the peru shelf lack any barium enrichment whereas this element is significantly enriched in slope and basinal deposits in water columns deeper than 2000 m this depth effect is further illustrated at site 682 located in the rapidly subsiding lima basin the quaternary sequence deposited at water depths 3000 m is enriched in organic carbon opal and biogenic barium the miocene sediments although deposited under highly productive waters associated with a coastal upwclling centre do not show an enrichment in the barium record corresponding to the very high organic carbon and opal levels a pattern that is consistent with deposition in shallow basins in addition to the effect of water depth on the barium distribution overprinting of primary signals can be observed in sediments from upwclling areas undergoing strong anoxic diagenesis microcrystalline barite is partly dissolved in intervals depleted in interstitial sulphate as shown for sediments from the peru margin dissolution of barite in sulphate depleted intervals of deep water sections leads to high barium concentrations near the termination of the sulphate reducing zone where downward sulphate and upward barium diffusion foster local barite precipitation in diagenetic fronts the barium distribution in sedimentary oxic and suboxic environments at deep water depositional sites has a high potential as a palaeoproductivity indicator however barium accumulation as a proxy for ocean fertility should be used with caution in areas of varying water depths and in anoxic diagenetic environments where sulphate depletion undcrsatur ates the interstitial waters with respect to barite

correlations among the reflectances of vitrinite chitinozoans graptolites and scolecodonts abstract paleozoic marine sequences sampled in outcrops and wells of northeastern gaspe peninsula quebec appalachians yield kerogen composed in part of vitrinite and zooclasts chitinozoans scolecodonts and graptolites on which reflectance measurements were made the comparison between means of random measurements show that reflectance of chitinozoans is similar to that of telinite vitrinite with a cellular texture and that the reflectance of scolecodonts is significantly lower than that of telinite in the lower range of studied values at higher reflectivities differences decrease but at the end of the condensate gas zone reflectancea are not yet identical as shown by previous studies reflectance of graptolites is slightly less than that of telinite pyrobitumen reflectance is related to the lithology of the host rock and no generalized correlation can be established between the reflectance of pyrobitumen and that of vitrinite

the sipoholon geothermal field and adjacent geothermal systems along the north central sumatra fault belt indonesia reviews on geochemistry tectonics and natural heat loss abstract the sipoholon system in the tarutung basin is one of five geothermal systems associated with a c 100 km stretch of the sumatra fault system sfs in north central sumatra indonesia that exhibits parallel sets of dextral strike slip faults associated with seismic activity characteristics of discharged thermal fluids differ significantly between the systems the gas rich sipoholon field transfers only c 19 mw heat by ca so4 hco3 springs with sio2 fluid equilibria pointing to temperatures of 50 80 c at intermediate depths most of its thermal springs t in contrast all four thermal systems in the sarulla block concession to the southeast of the sipoholon field are convective high temperature systems that transfer significant heat to the surface fumaroles steaming ground thermal springs hot pools and thermal lakes discharge at least 50 mw heat at three of the four prospects where the temperatures of springs and fumaroles often reach boiling point many hot springs of the sarulla block systems discharge dominantly na hco3 cl type waters with partially equilibrated cation compositions a result of fluid rock equilibration and mixing processes sio2 fluid equilibria indicate 130 to c 200 c with cation geothermometers pointing to a high reservoir temperature 200 260 c for all four systems this was confirmed by the first deep exploratory wells drilled c 20 years ago in three prospects that encountered t 250 c at bottom hole 1 5 km depth the structural setting of the five geothermal fields is complex at tarutung it is associated with the narrow tarutung basin filled with volcanic debris and ash the basin exhibits a partly exposed dextral strike slip fault along its ne margin and can be interpreted in terms of a trans tensional pull apart basin two of the adjacent sarulla block systems are associated with large volcanic debris basins namora i langit and silangkitang that exhibit half graben structures in profiles normal to two large active faults of the sumatra fault system sfs the other two systems donotasik and sibualbuali are hosted by an elongated graben structure parallel and within the sfs and by a stratovolcano respectively

hot shale in an ice world paleoceanographic evolution of the northern gondwana margin during the early paleozoic tanezzuft formation tunisia abstract the tanezzuft formation deposited in marine periglacial conditions on the northern gondwana margin during the end of the ice house climate that characterized the lowermost silurian the basal part of this sedimentary sequence is characterized by organic rich facies with locally very high measured total organic carbon toc content up to values greater than 20 while deposition of organic rich sediments during greenhouse time interval is well known deposition of black shales during ice house conditions is poorly documented the extraordinary paleoceanographic conditions that led to the accumulation and preservation of enormous amounts of organic matter in periglacial settings makes this formation an atypical example of black shales deposition the study area is situated on the north african platform in southern tunisia on the northern flank of the ghadames basin petrophysical logs biostratigraphic organic and inorganic geochemical data from nine wells are here integrated with the aim of reconstructing the depositional history of the tanezzuft formation and the role played by organic matter production preservation and dilution through time data indicate that dilution that is depositional style and framework had an important control on lateral and vertical distribution of the c organic rich facies toc and hydrogen index hi maxima are found in correspondence of the main transgressive phases with repetitive stacking patterns strongly associated with source rock properties organic matter production as observed by detailed palynofacies analysis was mainly marine in nature with important contribution by amorphous organic matter leiosphaeridia tasmanaceae and minor amounts of graptolites fragments geochemical data indicate that the organic richest interval hot shale of the tanezzuft formation deposited under severe anoxic conditions that resulted in enhanced organic matter preservation at the sea floor of mod 3d an organic facies modelling software tool by sintef is used in order to reconstruct and quantify the peculiar processes that controlled the exceptional accumulation of organic matter at the time of deposition modelling results indicate that water stratification was the most plausible process that drove organic matter sedimentation under mesotrophic conditions density stratification was probably controlled by the deglaciation phase after the hirnantian glaciation and or by the flooded complex basin physiography that induced an inefficient circulation of the water masses the complete recovery from these extreme paleoceanographic conditions implied progressive processes that took several hundred thousand years

compositions and parageneses of secondary minerals in the onikobe geothermal system japan abstract parageneses and chemical compositions of secondary minerals in many core samples of the onikobe geothermal system japan were investigated in detail in order to evaluate the controls of geothermal waters on alterations of andesitic dacitic rocks depth zonations of secondary minerals were delineated for cazeolites as mordenite laumontite yugawaralite wairakite and clay minerals as smectite alkaline smectite chlorite smectite chlorite compositional variations with depth hence temperature are apparent for smectite chlorite and illite chlorite interstratified clay minerals but not for wairakite both prehnite and epidote at depth have fe rich compositions and become more aluminous with increasing depth the ubiquitous occurrence of pyrite and rare magnetite and the absence of hematite suggest that the onikobe system had fs2 fo2 conditions within the pyrite stability field the occurrence of abundant calcite and ca zeolites indicates that thermal waters at depth are neutral to slightly alkaline and xco2 is very low to stabilize ca al silicates this conclusion is consistent with the production of a remarkable amount of alkaline high temperature steam and thermal waters in a newly drilled production well

fluctuations in epeiric sea carbonate production during silurian positive carbon isotope excursions a review of proposed paleoceanographic models positive excursions in the carbon isotopic ratio of marine carbonates 13ccarb are commonly attributed to an increase in the burial ratio of organic versus carbonate carbon in the global oceans regardless of whether this increased deposition of organic carbon was oceanographically or biologically induced the fact that high carbon isotope values are most often attributed to the sequestration and burial of organic carbon remains the notion that high 13ccarb values should be the result of organic rich deposition in epeiric sea settings is not surprising considering that the overwhelming majority of organic carbon burial in the modern oceans occurs in continental shelf and margin settings what is surprising is that major positive carbon isotope excursions during the silurian are recorded in clean carbonate successions with little to no appreciable black shale deposition in epeiric seas in fact silurian 13ccarb excursions occurred during intervals of prolific reef development and an overall expansion of carbonate platform environments globally this discrepancy has sparked considerable debate among silurian carbon isotope specialists but has offered a valuable opportunity to re examine the intricate connections among nutrients primary productivity carbonate sedimentology and the global carbon cycle in the lower paleozoic here we consider several sedimentological and geochemical features of one of these silurian positive carbon isotope 13ccarb excursions and discuss the broader implications of current silurian 13ccarb models to the interpretation of lower paleozoic carbonate sequences

a chronology of paleozoic sea level changes sea levels have been determined for most of the paleozoic era 542 to 251 million years ago but an integrated history of sea levels has remained unrealized we reconstructed a history of sea level fluctuations for the entire paleozoic by using stratigraphic sections from pericratonic and cratonic basins evaluation of the timing and amplitude of individual sea level events reveals that the magnitude of change is the most problematic to estimate accurately the long term sea level shows a gradual rise through the cambrian reaching a zenith in the late ordovician then a short lived but prominent withdrawal in response to hirnantian glaciation subsequent but decreasingly substantial eustatic highs occurred in the mid silurian near the middle late devonian boundary and in the latest carboniferous eustatic lows are recorded in the early devonian near the mississippian pennsylvanian boundary and in the late permian one hundred and seventy two eustatic events are documented for the paleozoic varying in magnitude from a few tens of meters to 125 meters

low productivity and slow deep water circulation in mid cretaceous oceans paleofertility estimates are derived from organic carbon accumulation rates determined in nonbioturbated mid cretaceous deep sea deposits using organic carbon preservation factors observed in laminated sediments from anoxic holocene environments the estimated mid cretaceous primary production rates are as much as an order of magnitude lower than those measured in today s oceans an evaluation of dissolved oxygen budgets using a simple oceanic circulation model indicates very low deep water renewal rates in mid cretaceous oceans 28 references 2 tables 4 figures

recurring patterns of total organic carbon and source rock quality within a sequence stratigraphic framework sequence stratigraphy has been combined with total organic carbon toc analysis from well logs core and cuttings to develop a model of toc accumulation in marine source rocks routine well profiling of toc in marine source rocks has revealed that recurrent patterns in the vertical distribution of toc occur that can be explained with sequence stratigraphic concepts the model assumes that the principle controls on organic carbon accumulation are 1 the presence of low oxygen conditions at the sediment water interface and 2 sedimentation rate under these circumstances toc will vary inversely with terrigenous clastic influx if accommodation is high clastic influx is low in distal locations and the resulting weight percent toc in basinal sediments is increased th maximum toc in a vertical profile through a single marine sequence probably correlates to the maximum flooding surface toc decreases above this surface due to increasing sediment dilution during highstand progradation and decreases below it with the higher sedimentation rate of the older transgressive systems tract commensurate with toc increase towards the maximum flooding surface the organic matter type becomes more marine and therefore increasingly oil prone several marine source rock examples are presented as well as a lacustrine example which also conforms to the marine model

a 210 000 year record of barium variability in the deep northwest atlantic ocean the deep ocean is the storehouse for most of the carbon and nutrients in the ocean atmosphere system together with its out crops at high latitudes the deep ocean is of great importance in driving glacial interglacial changes in the carbon dioxide content of the atmosphere1 3 the chemical and physical structure of the deep glacial oceans can be reconstructed by means of palaeochemical tracers for example the cadmium and carbon isotope contents of benthic foraminifera have been used to reconstruct the phosphate or labile nutrient compositions of deep waters4 14 recently it was proposed15 that barium in benthic foraminifera could be used to reconstruct the distribution of refractory deep regenerated chemical properties in the water masses of the glacial oceans a reconstruction of barium concentra tions in the oceans at the time of the last glacial maximum revealed the greatest changes in the north atlantic where barium concentrations in deep water were up to 50 higher than at present16 here we present a record of the benthic ba ca ratio in the deep northwest atlantic stretching back to interglacial stage 7 210 kyr ago encompassing two full glacial cycles a comparison of the barium record with that of the other nutrient like tracers lends confidence in the general agreement between these tracers while showing some spectral variability unique to barium thus underscoring its utility as an additional palaeoceanographic tracer

enhanced trapping of molybdenum by sulfurized marine organic matter of marine origin in mesozoic limestones and shales there have been many studies devoted to trace metals and their value in assessing the paleoredox conditions of ancient marine deposition among them molybdenum mo is frequently cited as an effective proxy for sediments and sedimentary rocks recently helz et al helz g r miller c v charnock j m mosselmans j l w pattrick r a d garner c d vaughan d j 1996 mechanisms of molybdenum removal from the sea and its concentration in black shales exafs evidences geochim cosmochim acta 60 3631 3642 and adelson et al adelson j m helz g r miller c v 2001 reconstructing the rise of recent coastal anoxia molybdenum in chesapeake bay sediments geochim cosmochim acta 65 237 252 suggested that mo does not behave conservatively in the water column when h2s reaches a threshold concentration above this concentration a switch operates and mo is scavenged by forming bonds with metal rich notably iron particles sulfur rich organic molecules and pyrite in this paper mo trapping by sulfur rich organic matter om in ancient marine deposits is emphasized the following mesozoic geological formations were selected for study because of their relatively high concentration of sulfurized om the akkuyu formation turkey the calcaires d orbagnoux france and kimmeridge clay uk and its timeequivalent in boulonnais france the kashpir oil shales russia and the la luna formation venezuela the sulfur rich om is identified by either measured organic s abundance or kerogen microscope observation our results show that mo is systematically more enriched relative to the other redox sensitive sulfide forming elements studied u v ni cu zn cr and mo enrichment is positively correlated with the amount of sulfurized om but not with pyrite abundance these results illuminate the role played by sulfurized om in geologic scale mo capture and retention but they also underline the role played by reactive iron significant om sulfurization is only possible when reactive iron is limited nevertheless pyrite formation though limited could act as an initial mo trap prior to mo uptake by om that is sulfurized after the pyritization step in future paleoenvironmental reconstructions attention must be paid to this enhanced mo enrichment in the presence of sulfurized organic matter in such cases the use of mo could lead to overestimation of the reducing conditions of the depositional environment

fluid flow within the damage zone of the boccheggiano extensional fault larderello travale geothermal field central italy structures alteration and implications for hydrothermal mineralization in extensional settings the neogene extensional province of southern tuscany in central italy provides an outstanding example of fossil and active structurally controlled fluid flow and epithermal ore mineralization associated with post orogenic silicic magmatism characterization of the hydrodynamic regime leading to the genesis of the polysulphide deposit known as filone di boccheggiano hosted within the damage zone of the boccheggiano fault is a key target to assess modes of fossil hydrothermal fluid circulation in the region and more generally to provide inferences on fault controlled hydrothermal fluid flow in extensional settings we provide a detailed description of the fault zone architecture and alteration mineralization associated with the boccheggiano ore deposit and report the results of fluid inclusion and stable oxygen isotope studies this investigation shows that the boccheggiano ore consists of an adularia illite type epithermal deposit and that sulphide ore deposition was controlled by channelling of hydrothermal fluids of dominantly meteoric origin within the highly anisotropic permeability structure of the boccheggiano fault the low permeability structure of the fault core compartmentalized the fluid outflow preventing substantial cross fault flow with focused fluid flow occurring at the hangingwall of the fault controlled by fracture permeability fluid inclusion characteristics indicate that ore minerals were deposited between 280 and 350 c in the upper levels of the brittle extending crust lithostatic pressure in the order of 0 1 gpa abundant vapour rich inclusions in ore stage quartz are consistent with fluid immiscibility and boiling and quartz ore vein textures suggest that mineralization in the boccheggiano ore deposit occurred during cyclic fluid flow in a deformation regime regulated by transient and fluctuating fluid pressure conditions results from this study i predict a strongly anisotropic permeability structure of the fault damage zone during crustal extension and ii indicate the rate of secondary structural permeability creation and maintenance by active deformation in the hangingwall of extensional faults as the major factor leading to effective hydraulic transmissivity in extensional terranes these features intimately link ore grade mineralization in extensional settings to telescoping of hydrothermal flow along the hangingwall block s of major extensional fault zones

seismic history and seismotectonics of the sunda arc historic records of the last 300 years reveal two great interplate earthquakes 1833 mw 8 1861 mw 8 8 which ruptured major segments of the sumatra fore arc in western indonesia a significant percentage of interplate slip along this portion of the plate boundary appears to occur seismically the ends of these rupture zones are coincident with clusters of large ms 7 and moderate 6 ms 7 shocks and with heterogeneities in the plate interface as inferred from geologic and geophysical data the northern extent of the 1833 rupture zone is coincident with a group of moderate and large earthquakes a structural arch in the fore arc and a fracture zone on the subducted plate the southern portion is coincident with a very prominent cluster and the along strike extension of a sediment filled trough on the subducted plate prior to this study sumatra was characterized as relatively aseismic as inferred from the lack of great earthquakes in the instrumental record of this century java and the lesser sunda islands had major ms 6 earthquakes in the historic record but none are of the same magnitude as the great events near sumatra there is no clear evidence that shocks in the java fore arc were interplate events yet geophysical data indicate recent uplift of the trench slope break and a change in strike of the trench axis where the northernmost flank of the roo rise a prominent bathymetrie high appears to be interacting with the fore arc this feature was formed at a ridge crest and is more buoyant and thus more difficult to subduct than the surrounding seafloor there is no increase in seismicity associated with this tectonism however that may indicate a lack of contact between the crystalline portions of the plates at this time we infer that a majority of slip on the plate interface near java occurs aseismically the variation in occurrence of great interplate earthquakes along the sunda arc may be interpreted in terms of a model that attributes variation in interplate coupling to the age of the subducted lithosphere great interplate earthquakes occur near sumatra where the age of the youngest crust is 46 ma the characteristics of the sunda arc and analogies with pacific arcs imply that the entire length of sumatra has the potential to produce great thrust earthquakes its seismic potential should be considered high as there has been no recurrence of the great events of 1833 and 1861 in contrast no such events have been reported off java and the lesser sunda islands where the oldest crust is 152 ma the plate interface near java and the lesser sunda islands should be considered to have low seismic potential

implications for mechanical properties of brittle faults from observations of the punchbowl fault zone california field observations of the punchbowl fault zone an inactive trace of the san andreas are integrated with results from experimental deformation of naturally deformed punchbowl fault rocks for a qualitative description of the mechanical properties of the fault and additional information for conceptual models of crustal faulting the punchbowl fault zone consists of a single continuous gouge layer bounded by zones of extensively damaged host rock fault displacements were not only localized to the gouge layer but also to discrete shear surfaces within the gouge deformation in the exposure studied probably occurred at depths of 2 to 4 km and was dominated by cataclastic mechanisms textural data also suggest that significant amounts of pore fluids were present during faulting and that fluid assisted mechanisms such as dissolution diffusion and precipitation were operative the experimental data on specimens collected from the fault zone suggest that there is a gradual decrease in strength and elastic modulus and an increase in relative ductility and permeability toward the main gouge zone the gouge layer has fairly uniform mechanical properites and it has significantly lower strength elastic modulus and permeability than both the damaged and the undeformed host rock for the punchbowl fault and possibly other brittle faults the variations in loading of the gouge zone with time are primarily governed by the morphology of the fault and the mechanical properties of the damaged host rock in addition the damaged zone acts as the permeable unit of the fault zone and surrounding rock it appears that the gouge primarily governs whether displacements are localized and it therefore may have a significant influence on the mode of slip

prograde phase relations in the state 2 14 well metasandstones salton sea geothermal field california seventy five core samples of medium to fine grained metasandstones from the state 2 14 borehole were studied petrologically and mineralogically to evaluate compositional variations of geothermal minerals and prograde metamorphic reactions three distinct metamorphic zones are defined based on the appearance of index minerals with increasing grade they are 1 chlorite calcite chl cc zone at depths between 610 and 2480 m 2 biotite bt zone between 2480 and 3000 m and 3 clinopyroxene cpx zone between 3000 and 3180 m all of the studied metasandstones at depths greater than 906 m contain epidote ep and quartz qtz with or without albite ab characteristic assemblages ep qtz ab are 1 chl cc k feldspar ksp phengitic muscovite for the chl cc zone 2 bt chl ksp anhydrite anh and bt act chl for the bt zone and 3 diopsidesalite act bt oligoclase actinolitic hornblende for the cpx zone epidote exhibits a compositional variation ranging from 0 11 to 0 42 xfe fe fe al many amphibole grains of the clinopyroxene zone show patchy or lamellar intergrowths of both actinolite and actinolitic hornblende on a scale less than a few tens of micrometers these amphiboles show distinct compositional discontinuities such as in al2o3 contents 2 7 4 8 wt and fe fe mg ratios 0 41 0 55 the cpx zone samples thus mark the transition from the greenschist to amphibolite facies other important secondary phases include rutile or anatase depths 940 m peristerite 1235 m and mn salite 2484 m the observed assemblages and compositions of minerals are chemographically interpreted utilizing an epidote projection in the simple system al2o3 k2o mgo cao sio2 h2o co2 reactions for the appearance of index minerals are elucidated in a qualitative t xco2 diagram the results indicate that l the compositions of chl and bt are highly variable depending on the bulk composition however chl in the chl cc zone becomes enriched in mg with increasing depth 2 bt forms by a discontinuous reaction ksp chl cc bt ep qtz h2o co2 hence the first appearance of bt is greatly affected by the fluid composition 3 the hydrothermal fluid in equilibrium with the analyzed assemblages is very low in xco2 0 03 and 4 the absence of wairakite and prehnite is attributed to the high fo2 values of the salton sea geothermal system

the effects of coal gangue and fly ash on the hydraulic properties and water content distribution in reconstructed soil profiles of coal mined land with a high groundwater table soil water systems have been severely degraded in coal mined and subsiding land where a shallow groundwater table is also present the present paper discussed the effects of fly ash fa and coal gangue cg as filling materials on the hydraulic properties and water content distribution in a profile for the purpose of rehabilitating subsided lands the saturated water content water characteristic curve and water diffusivity of local soil fa cg and a mixture of fa and cg mixed filling were characterized a column experiment was conducted to investigate the changes of water content in profiles reconstructed from the combination of soil and filling materials including soil only fa cg and a mixture of fa and cg which were used to fill the lower part of the reconstructed profile the mixture of fa and cg was found to possess similar hydraulic properties to those of the soil particularly high water holding capacity and permeability moreover the volumetric water contents in the whole profile containing the mixture of fa and cg were consistent with those of the profile reconstructed with soil only as a result it is recommended to adopt the mixture of fa and cg for reconstructing the lower profile of the land to alleviate or rehabilitate subsided land in coal mines

evaluation and modelling of tertiary source rocks in the central arctic ocean abstract with the recently recovered organic rich sediments of early tertiary age from the lomonosov ridge by the integrated ocean drilling program iodp expedition 302 the first data collection directly from source rocks of the central basins of the arctic ocean is now available using the results of seismic interpretations and published sedimentological and organic geochemical data from expedition 302 the framework for the first quantitative assessment of source rock quality and distribution of the palaeogene sediments was modelled in the central arctic ocean the modelling results suggest that an approximately 100 m thick early to middle eocene sedimentary sequence of good to very good source rocks exists along a 75 km long transect across the lomonosov ridge in situ generation of hydrocarbons is unlikely because the overburden 200 250 m and consequently the thermal maturity are too low burial history and thermal modelling reveal that an additional overburden of at least 1000 m is necessary to start hydrocarbon generation along the ridge however source rock modelling results show that good source rock potential may exist in correlative units in the adjacent amundsen basin simulated organic carbon contents of 1 5 5 coupled with an overburden of 1000 1200 m and heat flow anomalies 117 and 100 mw m 2 due to the vicinity to the gakkel ridge spreading centre indicate that necessary conditions for hydrocarbon expulsion are already reached and point to viability of a potential petroleum system our results support the hypothesis that deposition of a potentially good hydrocarbon source rock occurred across the entire arctic basin and adjacent margins during the early tertiary