bitumen veins and eocene transpression neuquen basin argentina abstract in the northwestern part of the petroleum rich neuquen basin veins of solid hydrocarbon bitumen have been reported from over 150 localities the bitumen veins are mostly steeply dipping and show intrusive relationships with their wall rocks the largest are some 8 m wide 8 km long and probably several kilometres deep the bitumen probably formed in the earliest stages of thermal maturation of organically rich source rocks the most likely source rocks for the bitumen as well as for most of the oil and gas in the neuquen basin are black marine shales of the vaca muerta and agrio formations these were deposited in a rift setting during the late jurassic and early cretaceous according to subsidence models the source rocks should have reached thermal maturity in the latest cretaceous or paleocene and should have remained in the oil window ever since although the bitumen has not been dated directly the veins probably formed soon after maturation of the source rocks in other words in the paleocene or eocene the wall rocks of the veins are mostly the source rocks themselves other veins have been emplaced into overlying strata of early cretaceous to paleocene ages or into underlying sediments of jurassic age the bitumen veins have preferred orientations the dominant trend is 060 and subsidiary trends are either 000 to 020 or 100 as in other basins worldwide the majority of bitumen veins in the neuquen basin probably formed by tensile failure in orientations perpendicular to the least compressive stress under the combined effects of regional tectonics and fluid overpressures the orientations of the veins are compatible with the direction of oblique convergence between continental south america and the oceanic nazca plate in the eocene many major structures in the neuquen basin are also of eocene age and may have formed under right lateral transpression

raw material quality and oldowan hominin toolstone preferences evidence from kanjera south kenya the role of raw material quality in oldowan technology has not been fully explored there are numerous studies suggesting oldowan hominins preferred certain types of stone for artifact manufacture previous studies of the artifact assemblage from the early pliocene oldowan locality of kanjera south south rachuonyo district kenya show that raw material selection and transport was an important aspect of late pliocene hominin adaptations yet the exact properties of stones that hominins were selecting remain enigmatic two potentially important features of artifact raw material are durability and fracture predictability we investigate fracture predictability through mechanical tests of stone and investigations of the affect of stone properties on fracture patterns in archaeological collections we investigate stone durability with actualistic studies of edge attrition combined with further mechanical tests of various lithologies oldowan hominins at kanjera appear to have selected raw materials based on their durability the ability for a stone to fracture consistently does not appear to be as important in hominin toolstone preference as previously assumed hominins that produced the assemblages at kanjera south appear to have incorporated an extensive understanding of various attributes of raw material in the transport and production of stone artifacts when combined with previous research on the transport patterns at kanjera the results of this study provide evidence for a more complex raw material acquisition strategy than has previously been suggested for late pliocene oldowan hominins

alteration of crystalline basement rocks by hydrocarbon bearing fluids moinian of ross shire scotland abstract moinian proterozoic gneisses in easter ross shire scotland exhibit pronounced alteration where they have been subjected to the flow of hydrocarbon bearing fluids from an adjacent devonian sedimentary basin comparison of the petrography of altered and unaltered gneiss indicates that element redistribution accompanied the alteration process the alteration involved creation of secondary porosity by dissolution of primary minerals in the gneiss chloritization of biotite and precipitation of authigenic orthoclase cross cutting veinlets include bitumen authigenic quartz orthoclase albite monazite and titanium oxides attesting to redistribution of all the major components of the gneiss evidence for bitumen being coeval with albite quartz and an association of high porosity with bitumen indicate that hydrocarbon bearing fluids were present during the alteration process bitumen also penetrated beyond the visible alteration zone and accreted around radioelement bearing accessory minerals organic geochemical data indicate that there is a local source for the bitumen in the devonian sequence bitumen veining also occurs within the devonian sequence fluid inclusion data from quartz associated with bitumen in the gneiss and the devonian indicate minimum trapping temperatures of 120 140 and 100 120 c respectively the alteration was probably a result of a fluid flow episode relating to fault movement during basin subsidence

studying solute and particulate sediment transfer in a small mediterranean mountainous catchment subject to land abandonment the sediment budget of the small research catchment of cal parisa vallcebre eastern pyrenees was studied by hydrological monitoring and assessment of the erosion rates in the major sediment sources this area is characterized by clayey mudrock prone to landsliding and badland erosion but the catchment was selected in an area free of major badland features as a representative of middle mountain regions where a system of terraces and drainage ditches had been built for agricultural use but is now abandoned streamwater chemistry is dominated by ca 2 and hco 3 at concentrations close to calcite saturation total dissolved solids show dilution during runoff peaks and positive hysteresis loops that support a slow contribution of subsurface water relative dissolved ion concentrations are different for each event analysed particulate sediment yield is very low and represents only about 1 per cent of gross erosion in the catchment mineralogical analysis of suspended sediments shows an enrichment in calcite because of precipitation chemical analysis of suspended sediments using common one litre water samples shows higher contents of ca p and mn in transported sediment than in sediment source areas attributed to the precipitation of calcite and enrichment in organic particulate matter during events respectively for the two first elements whereas enrichment in mn remains uncertain solid matter yield is therefore clearly dominated by dissolved transport as a result of both high calcium bicarbonate concentrations in runoff waters and strong suspended sediment conveyance discontinuities land conservation structures are very effective because they are in good condition whereas the soil is covered by dense permanent vegetation nevertheless this state is unstable because the network of drainage ditches needs maintenance its spontaneous breakdown after abandonment may result in the rearrangement of the elementary stream network and gullying of old fields in hollows 1997 john wiley sons ltd

petrography and origin of deposits at the bentheim bitumen mine north western germany the fracture bound deposit at the sieringhoek bentheim bitumen mine in nw germany has yielded a substantial quantity of bitumen ore emplacement of the bitumen into the fracture system occurred under high pressure causing brecciation and impregnation of the host gildehaus sandstone subsequently the bitumen was brecciated and cemented by calcite and calcite entrained sand bitumen injection followed fracturing into a hydro carbon reservoir at depth generated from a jurassic cretaceous source rock diagenesis of the host rock was largely completed by the time of bitumen injection reflecting the long time gap during which source rock maturation occurred impurities in the bitumen include large quantities of rock fragments abraded during injection and crystals of metal oxides and sulphides

geology and geochemistry of bitumen vein deposits at ghost city junggar basin northwest china veins of solid bitumen occur in cretaceous sandstones at the northwest margin of the junggar basin china the bitumen has a low aromaticity and a composition comparable to gilsonite the bitumen contains abundant steranes and terpanes and s carotane although most n and i alkanes have been removed which is characteristic of the local crude oil the sterane and triterpane maturity parameters show that the bitumen local crude oil and source rocks are all mature bitumen wallrock relationships suggest that the host sandstone was not completely consolidated at the time of emplacement of the bitumen veins although bitumen emplacement was a relatively late diagenetic event the burial history for the northwest junggar basin shows that hydrocarbon generation from the assumed upper permian source rocks commenced in late triassic early jurassic times and suggests that rapid hydrocarbon generation may have resulted in overpressure contributing to the bitumen emplacement

geoelectric investigations into sandstone moisture regimes implications for rock weathering and the deterioration of san rock art in the golden gate reserve south africa the clarens sandstone in the golden gate reserve south africa is the canvas for a collection of san bushmen rock art dating from neolithic times until as recently as 150 years ago this rock art is under threat from human interference but also to a greater degree from weathering processes on the rock surface the dominant weathering processes occurring in the rock shelters which host the rock art are flaking and honeycombing two rock shelter sites in the reserve have been investigated using electric resistivity tomography ert and supportive methods for measuring surface moisture protimeter and surface hardness equotip these non destructive techniques can be used in situ to assess the extent of weathering within a rock outcrop and are especially suited for investigations in sensitive areas such as rock art sites moisture movement has been mapped and related to the weathering processes observed on the surface the aim of the study is to aid rock art conservation in the golden gate reserve through a better understanding of the driving processes of surface weathering the evidence shows that the extensive flaking and honeycombing found in the rock shelters is most likely caused by water pockets in the near surface zone which are replenished through internal moisture transport driving the superficial weathering processes these weathering processes pose a significant problem rock art in the golden gate reserve shows severe deterioration due to flaking conservation strategies should therefore take internal processes into account as much as their superficial expression

relationships among rainfall runoff and suspended sediment in a small catchment with badlands abstract the araguas catchment of the central spanish pyrenees has been monitored since 2004 to study weathering erosion and the hydrological and sediment response to rainfall events in order to understand the hydromorphological dynamics of a badland area in a relatively humid environment this small catchment 0 45 km2 shows highly active processes of physical and chemical weathering related to seasonal variations in temperature and moisture erosion and sediment transport are widely studied in badlands within mediterranean environments because they represent the dominant sediment source to obtain information about suspended sediment and discharge a gauging station was installed within the araguas catchment during the summer of 2005 the aim of this work is to determine the relationships among rainfall runoff and suspended sediment in this badland area towards this goal we analyze the relationships between suspended sediment concentration and discharge during rainfall events from a hydrological viewpoint the araguas catchment reacts to all rainfall events with torrential flow being the most characteristic hydrological response the results obtained between october 2005 and april 2007 reveal extremely high concentrations of suspended sediment with values frequently exceeding 100 g l 1 and reaching a maximum of 1200 g l 1 three different types of hysteretic loops were observed clockwise 22 events 28 counter clockwise 27 events 34 and figure eight 12 events 15 moreover 23 of events were classified as complex hysteretic loops and removed from the analysis due to their complexity clockwise hysteretic floods are characterized by their long duration and the highest hydrological and sedimentological responses counter clockwise hysteretic floods are characterized by their short duration and moderate hydrological and sediment responses finally figure eight hysteretic floods are related to multiple peaks in suspended sediment coinciding with oscillations in discharge associated with the highest rainfall intensities within each event and moderate hydrological and sediment responses

human impacts on fluvial systems in the mediterranean region the long history of substantial human impacts on the landscape of the mediterranean region and their effects on fluvial systems is documented these effects have included impacts of deforestation and other land use changes agricultural terracing on a wide scale water transfers and irrigation schemes during the 20th century major changes were made directly to channels through channelisation construction of dams of various sizes and extraction of gravel and indirectly by reforestation these changes have caused a major phase of incision on some rivers runoff and soil erosion have been affected by types of crops and agricultural practices as well as by the varying extent of cultivation and grazing some recent agricultural practices involve wholescale relandscaping of the topography and alteration of surface properties of material the importance of analysing the connectivity within different land units and of the spatial position of human activity within a catchment is illustrated the analysis of connectivity is the key to understanding the variability of impact and the extent of propagation of effects

an experimental assessment of the influences on edge damage to lithic artifacts a consideration of edge angle substrate grain size raw material properties and exposed face functional analyses of stone tool assemblages face a number of methodological challenges aside from determining specific uses it can be difficult to know which artifacts in an assemblage were used at all typically retouch is taken as a proxy for indicating past use but ignoring unretouched flakes means excluding the overwhelming majority of most assemblages assessing whether an unretouched flake has been used is complicated edge damage on flakes can be caused by use or by taphonomic processes one of the more important of these processes is trampling experiments have shown that trampling can create damage mimicking retouch and unlike some other taphonomic processes trampling is otherwise difficult to detect one possible solution is to look for patterning in the placement left vs right ventral vs dorsal proximal vs distal of edge damage and recent studies using gis based approaches have shown the utility of this method at an assemblage level here we trampled a set of experimental flakes made from two raw materials on two substrate types and analyzed the edge damage patterns using a newly developed image analysis program that is similar to previous gis based approaches we found that a previously unquantified variable edge angle is strongly correlated with the likelihood of damage thus in circumstances where edge angles are non randomly distributed across flake types trampling damage will be patterned these results have implications for previously published edge damage studies and further indicate that basic flake mechanics need to be considered in studies where function is inferred from edge damage patterns approaches to the archaeological record that employs assemblage level assessments of edge damage must consider a range of factors when inferring behaviors from these patterns

the effect of hammer mass and velocity on flake mass abstract this paper presents the results of controlled fracture experiments designed to investigate the effects on flake mass of varying the mass and velocity of the hammer it was found that the contribution of these two independent variables are almost negligible for a given combination of exterior platform angle and platform thickness though they must be sufficient to initiate production of a flake of a given potential mass

hydro geomorphological consequences of the abandonment of agricultural terraces in the mediterranean region key controlling factors and landscape stability patterns abstract traditional cultivation terraces are one of the most ancient and conspicuous agricultural landscapes in mountain and hilly regions of the mediterranean basin spreading out from asia the first terraces in the mediterranean region date from the bronze age and the classical hellenic and roman periods reaching their greatest spatial extent during the eighteenth and nineteenth centuries under optimum management these systems contribute to the conservation of soil and water resources by increasing infiltration and decreasing sediment yield however traditional management and cultivation ceased on many terraced landscapes of the northern shore mediterranean countries during the twentieth century with variable results an extensive bibliographic review and meta analysis was carried out to explore the main effects of land abandonment of mediterranean agricultural terraces on local hydrological and geomorphological processes our results point to the development of vegetation cover and degradation of terraced structures e g walls terrace risers channels as the main critical factors controlling the hydrological behaviour i e runoff production and hydrological connectivity of abandoned terrace systems severe geomorphological problems in the form of intense surface erosion aggressive piping and gullying occurred under special climatic semi arid climate lithologic dispersive marls and structural high vertical hydraulic gradient conditions dense colonization by vegetation proved to be of major importance for controlling surface erosion vegetation however showed a limited capacity to control the activity of mass movements in most cases mass movements in the form of small soil slips primarily affected long abandoned terraces in hillslope concavities and valley bottom positions that concentrate surface and subsurface water fluxes and show recurrent soil saturation in humid terraced landscapes characterized by high hillslope gradients and terrace risers the most devastating effects of mass movements took place in the form of debris slips and terrace cascading landslides triggered by extreme rainfall a variety of management options non intervention stewardship of natural rewilding processes and active rehabilitation can be applied depending on vegetation development potential site hydro geomorphic vulnerability and local socio economic interests effective conservation approaches will be required to preserve the environmental socio cultural and historical values of these ancient anthropogenic landscapes

petrology of the bitumen manjak deposits of barbados hydrocarbon migration in an accretionary prism abstract bitumen manjak deposits in barbados are located particularly along fracture planes including faults and also in calcite veins as veinlets vug fillings and bedding parallel seams in sandstones and as matrix to diagenetic carbonates they occur particularly near the margins of the diapiric joes river formation and in immediately adjacent rocks reflecting the role of diapirism in the migration of hydrocarbon bearing fluids the larger bitumen veins trend between e w and ne sw following the strike of fault bounded packets of the accretionary prism the predominant fabric in the basal complex of barbados that is hydrocarbon migration followed the structural grain petrographic relationships of bitumen with chemosynthetic diagenetic carbonates suggest that hydrocarbon migration was a multi stage process the host sediments to the bitumens were not well consolidated and appear to have been in an overpressured state hydrocarbon generation may have contributed to overpressuring and buoyancy enhanced diapirism the association of bitumens with faults and decollement surfaces suggests that the lubricating action of the bitumen helped to accommodate deformation during diapirism and other processes related to the evolution of the accretionary prism widespread impregnation of sandstones in the joes river formation suggests that hydrocarbon migration was primarily by intergranular flow in a state of low confining pressure and did not depend on migration along the fault planes which may be of a later date

variability of the rebound hardness as a proxy for detecting the levels of continuity and isotropy in archaeological quartz abstract the equotip hardness tester is applied to different types of quartz and other lithic raw materials in order to determine if variations in the rebound hardness measured by this device may serve as a proxy for detecting the levels of continuity and isotropy of toolstones continuity the amount of cracks and other internal defects and isotropy the measure of the directional properties of a raw material are known to have important effects on the level of consistency and predictability of fractures which in turn is traditionally considered a main factor for defining the flaking quality of a given raw material the results demonstrate the existence of differences among the raw materials analysed in both the average value and the variability of the rebound hardness while cryptocrystalline samples show the most homogeneous results quartz and metamorphic rocks display a comparatively higher variance in the specific case of quartz such variability seems to be mainly caused by the presence of internal planes and discontinuities while anisotropy although also active had played a comparatively modest role the results achieved by the equotip hardness tester suggest that this device could be successfully used for a basic or preliminary estimating of some of the physical and mechanical properties of stone raw materials therefore it is a potential index test for complementing other more accurate laboratory methods

timing and temperature of decollement on hydrocarbon source rock beds in cyclic lacustrine successions abstract the generation of hydrocarbons causes lubrication of source rock bedding planes which can enhance deformation during basin subsidence and subsequent tectonic events deformation includes decollement i e gravitational sliding of rocks above the lubricated horizon in cyclic sequences such as occur in many lacustrine basins decollement is generally restricted to the organic rich beds of the cycle case studies in lacustrine successions in the devonian orcadian basin scotland and the triassic jurassic hartford deerfield basin usa show that movement of material associated with the decollement surface occurred in the current down dip direction these extensional basins experienced rapid subsidence and a high heat flow such that hydrocarbon generation and therefore decollement occurred early in the basin histories during extension half graben rotation ensured that the beds were dipping during hydrocarbon generation facilitating decollement inversion of the orcadian basin reactivated decollement surfaces involving thrust motion in some cases minerals precipitated in tension cavities associated with decollement yield fluid inclusion homogenization temperatures in the ranges 96 139 c and 85 96 c for the orcadian and hartford deerfield basins respectively these data are consistent with burial into the oil window at depths of between 1 5 and 2 0 km

time and temperature in petroleum formation application of lopatin s method to petroleum exploration n v lopatin in the soviet union has developed a method for taking both time and temperature into account as factors in thermal maturation of kerogen lopatin s time temperature index of maturity tti values correlate with the thermal regimes corresponding to generation and preservation of hydrocarbons because such information is potentially of great interest for oil exploration a calibration and evaluation have been made of lopatin s method within the limitations of the data presently available the following statements can be made 1 the rate of the chemical reactions involved in thermal maturation of organic material appears to double with every 10 c 18 f rise in temperature 2 threshold values of lopatin s time temperature index of maturity tti are 15 onset of oil generation 75 peak oil generation 160 end oil generation 500 40 oil preservation deadline 1 000 50 oil preservation deadline 1 500 wet gas preservation deadline 65 000 dry gas preservation deadline 3 tti values calculated from lopatin reconstructions consistently agree with other maturation parameters commonly used by petroleum geochemists potential applications of lopatin s method for oil exploration include timing of oil generation calculation of volume of hydrocarbons generated within a basin and determination of economic deadlines

how flakes shatter a critical evaluation of quartz fracture analysis despite its worldwide use as a stone tool raw material quartz is known to be a difficult material for archaeologists the main reason for this is the tendency of quartz flakes to fragment during detachment which complicates the use of traditional lithic analyses in this article we present an experimental study of quartz flake fragmentation we evaluate the method called fracture analysis that has been developed and used explicitly for the study of quartz assemblages the method assumes high predictability of quartz flake fragmentation but our experiments show that there is significant variation in fragmentation that fracture analysis does not take into account our results indicate that this variation is partly explained by indenter hardness the relative thickness of the detached flake as well as individual knapper related factors these results undermine the applicability of quartz fracture analysis in its current form in addition we discuss the effects of flake fragmentation on the technological organisation of prehistoric quartz users and suggest that it has affected reduction strategies as well as blank and tool dimensions we also suggest that there should be mobility related differences in archaeological assemblages in terms of the quality of the quartz raw material and that the curation of quartz should be low in relation to better quality raw materials used parallel with it

vein quartz in lithic traditions an analysis based on experimental archaeology abstract worldwide vein quartz was a commonly used raw material for stone tools but this material has proved difficult for archaeologists to analyse because many quartz assemblages appear to be comprised of amorphous pieces not easily recognised as humanly modified or forming tools this paper discusses the analysis of the debitage focusing on the debitage fragmentation rate the debitage break and fragment types and the quantitative analysis of the complete flakes resulting from experimental knapping of quartz which formed part of a project which investigated the use of quartz in irish prehistoric lithic traditions the results have highlighted the complexity involved in analysing quartz assemblages and the significant differences between the debitage products of quartz and chert knapping assemblages while bipolar knapping is generally easy to differentiate from direct percussion it is harder to differentiate between soft and hard hammer percussion

quartz c axis texture mapping of a variscan regional foliation malpica tui unit nw spain abstract mineral assemblages developed under high pressure and low to intermediate temperature conditions h p li t are found in eclogites orthogneisses and metasediments of the malpica tui unit mtu either defining or surrounded by a regional foliation that was mostly re equilibrated under amphibolite to greenschist facies conditions this regional tectonic foliation tracking the exhumation path of the mtu in the context of the variscan collision in sw europe has been studied using the microstructural record in quartz from the different rock types most of the quartz c axis patterns show two distinct asymmetries contained in perpendicular planes which are related to two different non coaxial components of the finite fabric i e the regional foliation and the lineation the asymmetry of deformation inferred from quartz c axis textures suggests that fabric accumulation during exhumation occurred under 3 d general flow departing strongly from the simple shear type this has significant tectonic implications for the interpretation of regional stretching lineations which in the present geodynamic setting of irregular collisional tectonics are not parallel to the direction of general tectonic transport and ultimately to the plate convergence direction

paleoreconstruction by biological markers abstract during diagenesis and conversion of the original lipid fraction of biological systems to petroleum hydrocarbons the following four basic events needed for paleoreconstruction can be monitored by biological markets 1 sourcing 2 maturation 3 migration and 4 biodegradation actual cases of applying biological markers to petroleum exploration problems in different parts of the world are demonstrated cretaceous and phosphoria sourced oils in the wyoming thrust belt can clearly be distinguished from one another by high quality source fingerprinting of biomarker terpanes using gas chromatography mass spectrometry identification of recently discovered biological markers head to head isoprenoids allows subtle source differentiation between oils from sumatra the degree of crude oil maturation in basins from california alaska russia wyoming and louisiana can be assessed by specific novel biomarker ratios 20s 20r sterane epimers field evidence from such interpretation is confirmed by laboratory pyrolysis of the rock an example of immature sumatra rock is given extensive migration is documented by biomarkers in several oils the effect of biodegradation on biomarker steranes and terpanes is exemlified in a california basin all biological marker results are consistent with the geological setting and add a new dimension in assisting the petroleum explorationist toward paleo reconstruction

the impact of raw material on acheulian large flake production raw material properties and availability have always been considered as having a definitive impact on the morphology size and production technology of acheulian large cutting tools shape and size of the naturally available raw material blocks have been cited as key factors in determining acheulian biface blank production technology as well as tool morphological variability in other words where large blocks of raw material were available africa large flakes were produced and where only smaller cobbles and nodules were to be found europe they become the primary type of blank used in this paper i explore a large body of data collected from acheulian sites from india to morocco and from south africa to england to test this common premise different raw material exploitation patterns as reflected in the bifacial tools in the various assemblages are described and analyzed the results indicate that in large flake based acheulian assemblages raw material constraints did not significantly affect either the blank production process or large cutting tool shape and size variability the acheulian large cutting toolmakers used the rock types available in the vicinity of their site in a sophisticated reduction sequence aimed to produce large cutting tools that are surprisingly similar regardless of the original shape size and type of raw material from which they were produced

relationships between suspended sediment concentrations and discharge in two small research basins in a mountainous mediterranean area vallcebre eastern pyrenees abstract the relationships between suspended sediment concentrations and discharge were studied at the can vila 0 56 km2 and ca l isard 1 32 km2 sub basins of the vallcebre research area eastern pyrenees during a period of 5 years that included 67 events of diverse magnitude abandoned agricultural fields and forests are the main land use in the can vila basin whereas the ca l isard basin is mainly forested though there are also some heavily eroded landscapes badlands the most frequent events were of a single discharge peak although double and multiple peaked events were also recorded clockwise positive hysteretic loops occurred in both catchments mainly during the wet seasons when precipitation was of moderate intensity average of 18 mm h 1 and baseflow before the event was rather high average for ca l isard 8 1 l s 1 km 2 and for can vila 11 76 l s 1 km 2 the bulk of stream discharge came from saturated areas whereas sediments came mainly from the stream channels counter clockwise negative hysteretic loops were much more frequent in the ca l isard basin mainly in summer when rainfall intensity was high average of 32 5 mm h 1 and baseflow was low average for ca l isard 0 94 l s 1 km 2 and for can vila 0 73 l s 1 km 2 most of the water and sediment came from the badlands eight shaped loops occurred in transition periods mainly in the ca l isard basin

erosion in mediterranean landscapes changes and future challenges abstract intense erosion processes are widespread in the mediterranean region and include sheet wash erosion rilling gullying shallow landsliding and the development of large and active badlands in both subhumid and semi arid areas this review analyses the main environmental and human features related to soil erosion processes and the main factors that explain the extreme variability of factors influencing soil erosion particularly recent land use changes the importance of erosion in the mediterranean is related to the long history of human activity in a region characterized by low levels of annual precipitation the occurrence of intense rainstorms and long lasting droughts high evapotranspiration the presence of steep slopes and the occurrence of recent tectonic activity together with the recurrent use of fire overgrazing and farming these factors have resulted in a complex landscape in which intensification and abandonment wealth and poverty can co exist the changing conditions of national and international markets and the evolution of population pressure are now the main drivers explaining land use changes including farmland abandonment in mountain areas the expansion of some subsidized crops to marginal lands and the development of new terraces affected by landslides and intense soil erosion during extreme rainstorm events the occurrence of human related forest fires affecting thousands of hectares each year is a significant problem in both the northern and southern areas of the mediterranean basin here we highlight the rise of new scientific challenges in controlling the negative consequences of soil erosion in the mediterranean region 1 to reduce the effects and extent of forest fires and restructure the spatial organization of abandoned landscapes 2 to provide guidance for making the eu agricultural policy more adapted to the complexity and fragility of mediterranean environments 3 to develop field methods and models to improve the identification of runoff and sediment contributing areas 4 to contribute to the conservation of landscapes i e bench terraced fields having high cultural and productivity values 5 to improve knowledge of the hydrological and geomorphological functioning of badlands with the aim of reducing sediment yield and accessibility 6 to better understand the effect of climate change on soil erosion in the mediterranean region and 7 to improve quantitative information on long term soil erosion

emplacement of bitumen asphaltite veins in the neuquen basin argentina veins of solid bitumen asphaltite have been commercially exploited in the neuquen basin argentina for over 100 yr veins are up to 5 m wide and several kilometers in length over a region of 15 000 km2 these veins were emplaced in fractures both parallel and at high angles to bedding in close proximity to their source rocks in the vaca muerta and agrio formations late jurassic early cretaceous two or more phases of bitumen emplacement can be recognized in several localities structures bearing viscous oil are younger than structures having solid bitumen bitumen emplacement was vigorous and caused brecciation and spalling of the host rocks the bitumen was also viscous and supports rock debris ranging in size from sand grains up to meter scale slabs brecciation bedding parallel injection and wall rock impregnation suggest high fluid pressures during emplacement high fluid pressure may have been engendered by substantial hydrocarbon generation from rich source rocks in a low permeability sequence and probably caused the fractures into which the bitumen migrated the bedding parallel veins facilitated decollement during thrusting that took place during and after bitumen emplacement the timing of emplacement relative to thrusting and oil migration constrains bitumen emplacement to the eocene oligocene

toolstone constraints on knapping skill levallois reduction with two different raw materials lithic raw material constraints are widely assumed to be a determining factor of flaked stone tool morphology but this assumption remains largely untested we conducted a controlled experiment to determine whether a knapper s growing replication skills would be hindered if the toolstone used was switched from large flakes of an easily worked chert to nodules of less tractable one two batches of preferential levallois cores were knapped an earlier series made from standardised large flakes of sediments dominated by chalcedonic quartz followed by a more challenging one using variably shaped cortical nodules of microcrystaline quartz that varies in the completeness of quartz replacement of calcite and dolomite skill level markers were designed to measure the knapper s ability to achieve a series of set goals these were quantified and subjected to statistical testing in all but one test significant increases in skill could be detected from the earlier to the later batch of reductions despite the drop in toolstone quality significant improvements in the consistency of the knapper s output could also be detected however the switch to a more challenging nodular chert did require extra shaping which resulted in more waste this masked visible progress towards producing a less costly core overall our results do not support the assumed primacy of toolstone constraints over other factors in influencing the morphology of flaked stone tools

quartz with rhombohedral cleavage from madagascar anhedral quartz slabs from a vein deposit in madagascar showing smooth cleavage planes parallel to positive rhombohedra r l0ll are described only two of the three equivalent pairs ofthe form l0tl show cleavage although ofdiflerent quality smoothness the best developed planes lie parallel to brazil twin lamellae the less well developed planes do not we presume small tectonically induced thermal shocks to be the releasing mechanism for rhombohedral cleavage fractures in combination with hydrolytic weakening and directed stress large smooth cleavage planes were formed since the r faces of quartz are f faces they have a minimum of free surface energy we assume this to be the reason for cleavage parallel to positive rhombohedral faces

stress fields a key to oil migration a coherent oil migration model based on geomechanical considerations includes both the high molecular kerogen structure and the capillary properties of source rocks oil is squeezed from kerogen by compaction following oil generation this squeezing effect should be created by the differential stress maximum compressive stress minus least compressive stress acting on the kerogen which has been chemically broken up by oil formation in sedimentary bodies whose water is at hydrostatic pressure the migration of oil seems to involve two processes 1 lateral transfer by channeling into the more coarsely microporous layers of the source rocks from the oil generation site toward the geologic structure or lower pressured zone and 2 vertical transfer from source rock to eservoir by the opening or reopening of vertical fractures in the few areas such as structural tops where the least compressive stress is slightly greater than or equal to the pore pressure and where the capillary pressure increment 2 ggr r of oil in the microporosity exceeds the tensile strength of the rock in sedimentary bodies whose water is overpressured the pore pressure should be governed by the least compressive stress and thus migration should begin by oil transfers in a system of small open fractures and eventually in larger fractures the theory demonstrates the impossibility of oil being transferred to the reservoir under true tensile conditions negative effective compressive stress and thus explains the large asphaltic veins of southeastern turkey and the well known bitumen veins of the uinta basin

variation in flow and suspended sediment transport in a montane river affected by hydropeaking and instream mining abstract the temporal and spatial variability of water and sediment loads of rivers is controlled by a suite of factors whose individual effects are often difficult to disentangle while land use changes and localised human activities such as instream mining and hydropeaking alter water and sediment transfer tributaries naturally contribute to discharge and sediment load of mainstem rivers and so may help compensate upstream anthropogenic factors the work presented here aimed to assess water and the sediment transfer in a river reach affected by gravel extraction and hydropeaking set against a backdrop of changes to the supply of water and sediment from tributaries discharge and suspended sediment transport were monitored during two average hydrological years at three cross sections along a 10 km reach of the upper river cinca in the southern pyrenees water and sediment loads differed substantially between the reaches the upper reach showed a largely torrential discharge regime controlled mainly by floods and had high but variable water and sediment loads the middle reach was influenced markedly by hydropeaking and tributary inflows which increased its annual water yield four fold suspended sediment load in this reach increased by only 25 compared to upstream indicating that dilution predominated in the lowermost section while discharge remained largely unaltered sediment load increased appreciably as a result of changes to sediment availability from instream mining and inputs from tributaries at the reach scale snowmelt and summer and autumn thunderstorms were responsible for most of the water yield while flood flows determined the magnitude and transport of the sediment load the study highlights that a combination of natural and human factors control the spatial and temporal transfer of water and sediment in river channels and that depending on their geographic location and effect size can result in marked variability even over short downstream distances

seasonal patterns of suspended sediment transport in an abandoned farmland catchment in the central spanish pyrenees the suspended sediment response of a small catchment subjected to farmland abandonment and subsequent plant recolonization was studied in relation to its hydrological functioning the analysis of data over a seven year period demonstrated that suspended sediment yield was greatly influenced by the occurrence of intense low frequency events greater amounts of suspended sediment were exported during spring when the catchment was hydrologically more active rainfall intensity and baseflow at the start of a flood event had a strong influence on the sediment response suggesting that several hydrological processes were active within the catchment ssc suspended sediment concentration q hysteretic loop analysis at the event scale aided understanding of the sedimentological and hydrological behaviour of the catchment during the study period the ssc q loops showed a high degree of seasonality and two main patterns strongly related to catchment wetness were distinguished when the catchment was dry mainly during summer and the beginning of autumn the predominant process was infiltration excess runoff over sparsely vegetated areas close to the main channel under these conditions floods exhibited a counter clockwise hysteretic loop and were characterized by a small streamflow response short duration and high ssc under wet conditions mainly during winter and spring saturation excess runoff was increasingly dominant over vegetated areas under these conditions floods exhibited a clockwise hysteretic loop and were characterized by a larger streamflow response longer duration and higher suspended sediment yield the lower ssc during the falling stage of the hydrograph is likely to be due to dilution effects related to the contribution of clean water resulting from enlargement of the saturated areas together with an increase in the baseflow discharge copyright 2009 john wiley sons ltd

origin of giant vein type bitumen deposits in the northwestern junggar basin nw china implications for fault controlled hydrocarbon accumulation abstract giant vein type bitumen deposits in the wuerhe region within the northwestern junggar basin of nw china are representative examples of similar bitumen deposits that are found in a number of other locations in both china and elsewhere these deposits can provide information on regional tectonics as well as insights into hydrocarbon and bitumen exploration but the origin of the deposits remains unclear this study focuses on determining the origin of the wuerhe bitumen deposit using field petrological and geochemical data results show that the bitumen veins are generally hosted by shallow high angle fault systems located within the nose of the wuerhe fault fold the bitumen is of low maturity and has an organic origin having formed by secondary alteration most likely biodegradation of crude oil sourced from the lower permian fengcheng formation p1f the bitumen contains high concentrations of carotane and gammacerane low concentrations of ts and diasteranes and comprises in ascending order of concentration c20 c21 c23 tricyclic terpanes and c27 c28 c29 regular steranes the bitumen was most likely formed during the early cretaceous under the control of faults a fault controlled model is presented for hydrocarbon migration and accumulation and the subsequent formation of this bitumen within the northwestern junggar basin this model suggests that future hydrocarbon exploration should focus on the cores of fault fold noses and areas of minor fold nose near deep seated fault zones especially where these areas correspond to potential moderate to shallow depth jurassic cretaceous reservoirs the new model should be able to guide exploration in other basins with similar tectonic settings of this study i e superimposed thrusting compression and transtension

isrm suggested method for determination of the schmidt hammer rebound hardness revised version with its portable simple and affordable attributes the schmidt hammer sh is an ideal index apparatus which underlies its increasing popularity and expanding range of applications the sh rebound hardness value r is perhaps the most frequently used index in rock mechanics practice for estimating the uniaxial compressive strength ucs and the modulus of elasticity e of intact rock both in laboratory conditions and in situ the sh is also widely used for estimating the ucs of discontinuity walls and assessing the workability excavatability and boreability of rocks by mechanical means cutting polishing milling crushing and fragmentation processes in quarrying drilling and tunneling

carbonaceous substances associated with the paleoproterozoic natural nuclear fission reactors of oklo gabon paragenesis thermal maturation and carbon isotopic and trace element compositions field relationships textural and reflectance characteristics and carbon isotopic compositions indicate that at least eight different categories of carbonaceous substances cs occur in the black shales uranium ores and fossil nuclear fission reactors of oklo the categories include kerogens of the mikouloungou coal in the fa formation the c1 pelites of the fa formation the black shale of the fb formation and bitumens present in veinlets in the basal black shale of the fb formation in the fa formation in normal ore and in hydraulic fractures in and near the fossil reactors and in late dolerite dikes bitumen migration occurred at oklo during at least three intervals 1 ca 2 0 ga ago when petroleum liquids derivatives of which are preserved as solid bitumen were generated by thermal maturation of black shale kerogen 2 ca 1 968 50 ma ago when 15 or more pockets of uranium ore achieved criticality and 3 977 to 981 27 ma ago when dolerite dikes intruded radionuclide migration occurred during intervals 2 and 3 bitumenization trends established for organic matter which has undergone thermal maturation fail to discriminate between heat affected and normally matured cs at oklo in and near oklo reactors where several types of solid bitumen commonly occur in close association carbon of the youngest low reflectance bitumen is isotopically heavier than that of older high reflectance bitumen due to thermal cracking this process together with enhanced radiolysis of bitumen in and near the reactors have combined to increase its 13c avg 25 8 compared to that of bitumen samples in normal ore avg 35 5 distant from the reactors graphitized bitumen inhibited migration of 235u and some fission products in uraninite of the natural reactors however alkaline earth elements such as ba sr and mo and alkaline elements rb and cs not compatible in the uo2 crystalline structure have migrated in hydrothermal solutions and in the once fluid oklo bitumens in situ analysis of solid bitumens by laser ablation icp ms detects differences in trace element composition developed as a result of their varying geological histories and evolutionary trends

non destructive testing for the assessment of granite decay in heritage structures compared to quarry stone several types of granite found in two architectural heritage monuments were assessed with two non destructive portable techniques schmidt hammer rebound and ultrasound velocity vp similar assessments were conducted on the rock from which the granite was originally quarried for comparison the results obtained which revealed the existence of a direct correlation constitute a useful indication of decay particularly if the approximate dates of construction are known and conversely if they are not such stone assessments may provide a rough estimate of when the structure was built both of these convenient portable and non destructive techniques may be used as reliable indicators of the degree of stone decay

application of the shetran basin scale landslide sediment yield model to the llobregat basin spanish pyrenees the first application of the shetran basin scale landslide erosion and sediment yield model is carried out for a major landsliding event in the upper 505 km2 of the llobregat basin in the eastern spanish pyrenees in november 1982 the model simulates the spatial distribution of shallow landslides and their sediment yield acknowledging uncertainty in the model parameter evaluation the aim of the application was not to reproduce the observed occurrence of landslides as accurately as possible with one simulation but to bracket the observed pattern with several simulations representing uncertainty in the key input conditions bounds on the landslide simulations were thus determined as a function of uncertainty in the vegetation root cohesion used in the model factor of safety calculations the resulting upper bound considerably overestimates the observed pattern 17 000 landslides compared with an observation of around 700 but it reproduces several of the principal clusters in the observed pattern the lower bound contains around 500 landslides the sediment yield estimates 2670 14 630 t km 2 are comparable to measurements elsewhere in the pyrenees for extreme events the results demonstrate an ability to simulate the basin scale landslide response to a rainfall event and the resulting sediment yield they also highlight the need for further research in setting the uncertainty bounds and in avoiding large overestimates of landslide occurrence arising in part from a current inability to model small scale controls for a basin of the given size copyright 2006 john wiley sons ltd

recognizing and quantifying expulsion of oil from the woodford formation and age equivalent rocks in oklahoma and arkansas accumulations of oil in fractures stylolites burrows sandstone lenses and chert nodules deeply embedded within organic rich mature oil source beds of late devonian early mississippian age are considered prima facie evidence of internal migration and expulsion most oil migrated internally and was expelled as a separate phase within a given section in which chert and black shale are interbedded contain the same type of organic matter and have reached the same level of thermal maturity black shales typically contain less hydrocarbons per weight percent toc than cherts the observed differences represent the amount of oil expelled from the black shales and range from 10 to 15 mg g toc for total bitumen 7 to 8 mg g toc for saturated hydrocarbons and 11 mg g toc for volatile hydrocarbons approximately 27 33 of the oil generated in these source rocks was calculated to have been expelled in the main oil producing region of central and southern oklahoma 22 billion bbl of bitumen and 16 billion bbl of saturated hydrocarbons were estimated to have been expelled from the woodford formation relatively efficient separate phase oil expulsion may be characteristic of very rich oil source rocks like those reported here such rocks would reach effective oil saturation and begin to expel oil as a separate phase at a relatively early stage of generation timing and efficiency of oil expulsion must then be influenced by the concentration and type of organic matter in the source rock because these factors determine the volume of oil generated and hence the time when a source rock becomes oil saturated

geochemistry and origin of organic rich sediment veins in fractured granitic basement helmsdale sutherlandshire uk abstract black sediment veins up to 2 cm width penetrate the caledonian helmsdale granite in the vicinity of the helmsdale fault onshore moray firth the black colour and geochemistry of the veins reflect a high content of organic carbon both devonian and jurassic shales are conceivable available sources but sterane compositions relate the organic matter to the jurassic shales a content of extractable organic matter higher than in the shales suggests that the carbon in the veins represents oil rather than mechanically mobilized shale the oil was present during sediment vein emplacement the veins were emplaced forcefully which may reflect high fluid pressure associated with post jurassic movement on the helmsdale fault

solute generation and transfer from a chemically reactive alpine glacial proglacial system the environs of the glacier de tsanfleuron switzerland was used as a study site to investigate the controls on the relative efficiency of solute generation and removal from glacial and proglacial environments here a 1500 m wide glacier forefield consists of a karstic limestone plateau flanked to the north by a till floored valley bedrocks and glacial debris are composed of chemically reactive pure and impure mesozoic and tertiary limestones with accessory pyrite spot sampling of ice snow and meltwaters in the late melt season was supplemented by systematic measurements of the main meltstream including during periods of rainfall and simple laboratory leaching and weathering experiments isotopic parameters were used to investigate water sources most meltwater and glacier ice samples lay close to a meteoric water line d 8 3 18o 14 defined by waters from small tributary streams heavy isotopic excursions of bulk meltwater chemistry were caused by rainfall events recovering within days to a 18o baseline around 12 permil no regular diurnal variations in 18 o were apparent the atmosphere is the source of cl and most na but the bulk of other solutes are generated in the environment ion loads of up to 1 meq l 1 are rapidly attained by calcite dissolution over periods of weeks to months pyrite oxidation generates sulphate and acidity that drives further calcite dissolution low water rock ratio weathering environments have characteristically high so42 mg2 sr2 and ratios of these species to calcium the characteristic cation ratios are influenced by non congruent calcite dissolution the ratio of sulphate to other species is highest where water rock contact times are highest although this relationship is complicated by spatial variations in pyrite abundance meltstream time series illustrate that 90 per cent of daily ion yields in fine weather are concentrated in the 12 h time period of higher discharge ion yields increase downstream mainly by a combination of dissolution of calcareous suspended sediment and input from tributaries and seepage from the till banks rainstorms lead to increased solute concentrations and resulting hourly fluxes can match daily fine weather ion fluxes excess nitrate appears to be largely sourced from the proglacial surface the capacity of the proglacial environment for yielding significant subsurface water as a result of the storm seems low unlike non glacial environments this implies that most of the excess solutes mobilized by storms comes from subglacial sources increased efficiency of yield of solutes from low water rock ratio subglacial weathering environments persists after the isotopic signature of the rainfall event has died away a simple conceptual model of the sources of water and solutes agrees with conclusions from attempts at hydrograph separation that mixing of water reservoirs of fixed solute composition cannot be used for quantitative descriptions of the system estimated annual solute yields 17 ton per km2 per m precipitation are high but cannot be readily expressed in purely areal terms because of likely significant losses to the underlying karstic system a tentative conclusion is that the proglacial environment is overall less efficient at producing solutes than the glacial environment but more information is required on processes in the early melt season to substantiate this statement copyright 1999 john wiley sons ltd

stress dependent morphological features on fracture surfaces of quartz and glass abstract stress dependent morphological features have been found on tensile fracture surfaces of natural brazilian quartz and synthetic quartz specimens which were flexed in air at room temperature these features are similar to stress dependent morphological features found on fracture surfaces of pyrex soda lime and lead glass when deformed in similar experiments for glass the relevant morphological feature is the fracture mirror a planar region surrounding the initial flaw stress dependent index features chosen for measurement in quartz depend upon the crystallographic orientation on the fracture surface their development is related to the crack system energy but in contrast to glass the features are not directly related to crack branching the experimental results follow an equation of the form a f r 1 2 where f is the fracture stress r is the size of a particular morphological feature e g the mirror radius in the case of glass and a is a constant from the magnitudes of a and the fracture toughness determined in these experiments we conclude that the natural brazilian quartz used in this study has significantly higher resistance to fracture than synthetic quartz

small basin response in a mediterranean mountainous abandoned farming area research design and preliminary results abstract a 36 ha basin named cal parisa has been studied since early 1988 in the eastern pyrenees spain this basin was selected as a representative of extensive areas on clayey bedrock formerly used for farming nowadays almost abandoned where badlands are of great importance as far as sediment production is concerned as we are interested in the hydrological behaviour of terraced areas and badland areas could strongly modify the hydrological and sediment response the basin is devoid of badlands but has some bedrock scars and small gullies severe geoecological disturbances were produced in it by agricultural land use in the past the basin was deforested topography was terraced and the drainage net was increased by ditching monitoring design is based on two measuring stations one at the main outlet and the other in a 16 ha sub basin and two sampling stations at the outlets of the two main sub basins a weather station and four rain recorders preliminary data show a hydrological response fully controlled by antecedent moisture conditions suggesting that soils have high infiltration capacities and that runoff is generated by saturation overland flow delayed flow being less significant stream water samples show relatively high dissolved solids concentrations dominated by calcium bicarbonate and suspended sediments concentrations about ten times less than dissolved ones as a consequence of the strong sediment conveyance discontinuities observed in the field

correlating river terrace remnants using an equotip hardness tester an example from the mino river northwestern iberian peninsula abstract this paper describes a new method to distinguish river terrace levels based on clast hardness and degree of weathering measured with an equotip hardness tester the technique was applied to a series of terraces on the mino river in the northwestern iberian peninsula where the lack of suitable material high degree of weathering and intense iron cementation precluded routine dating detailed mapping demonstrated that terrace sediments occupy a range of altitudes that make assignment to a specific terrace and or correlation between levels difficult statistical analysis of the equotip hardness data from quartzite clasts using k means clustering allowed four probable terrace levels to be identified a series of t tests generally supported these groupings a fifth lowermost terrace level was not included in the analysis because of limited exposure above a reservoir clast hardness and degree of terrace weathering were generally consistent with progressive river downcutting the occurrence of faulted sediments however suggested that terrace elevations were modified locally by post depositional tectonic movements which may explain why probable younger terraces in some sectors of the mino river are at higher elevations than older terraces in adjacent sectors the equotip tester helped to resolve stratigraphic uncertainties and to assign deposits to specific terrace levels and was found to be a useful tool to distinguish and correlate river terraces

a new technique for non destructive field measurement of rock surface strength an application of the equotip hardness tester to weathering studies tafone like depressions have developed on the aoshima sandstone blocks used for a masonry bridge pier in the coastal spray zone a thin layer of partial granular disintegration was found on the surface in depressions to evaluate quantitatively the strength of the thin weathered layer the hardness was measured at the surface of the sandstone blocks using both an equotip hardness tester and an l type schmidt hammer comparison of the two testing results indicates that the equotip hardness value is more sensitive in evaluating the strength of a thin layer of weathered surface rock than the schmidt hardness value by applying two methods i e both the repeated impact method and the single impact method the equotip tester can evaluate the strengths of fresh internal and weathered surficial portions of rocks having a thin weathering layer comparison of the two strengths enables evaluation of strength reduction due to weathering copyright 2007 john wiley sons ltd

fibrous calcite veins overpressures and primary oil migration the fibrous calcite veins found parallel to the bedding of certain shales may have been formed during burial as a consequence of overpressuring their presence could even be indicative of former overpressures this suggestion if it can be upheld carries implications for theories of primary oil migration

frequency magnitude relationships for precipitation stream flow and sediment load events in a small mediterranean basin vallcebre basin eastern pyrenees abstract precipitation discharge and suspended sediment concentrations were continuously measured during 10 years 1995 2004 at the ca l isard sub basin 1 32 km 2 of the vallcebre experimental catchments daily precipitation record is 22 years long when the ranks of the events obtained with the diverse variables considered precipitation depth peak discharge runoff depth suspended sediment concentration and sediment load were compared the results confirmed the complexity of the response of the catchment and demonstrated that precipitation is an irregular criterion for ranking the main sediment transporting events when the partial duration series corresponding to the 10 major events were analysed daily precipitation peak discharge and sediment concentration series showed good fits with log normal distributions but event precipitation runoff and sediment load series needed bi modal log normal distributions this behaviour may be attributed to the fact that event mass magnitudes depend not only on event intensity but also on its duration

raw material quality and prepared core technologies in northeast asia the design and assembly of lithic toolkits is mediated by a number of factors including the abundance and quality of raw materials available in general low raw material abundance and high raw material quality are thought to lead to formal tool designs whereas high raw material abundance and low raw material quality lead to informal designs low raw material quality is seen as the overriding factor producing informal tool designs even where low raw material abundance would favour formal designs in north china the predominance of simple flake and core technologies based on relatively poor quality raw materials and the near absence of sophisticated prepared core technologies seems to corroborate the importance of raw material quality in toolkit design recent studies of a late pleistocene lithic assemblage from the lower grotto at tsagaan agui cave mongolia suggest however that raw material quality is not an absolute constraint on the development of sophisticated core reduction strategies levallois like and other prepared core forms based on large flake blanks are conspicuous in the lower grotto assemblage despite the poor quality of raw material available at the site contrary to expectations these core forms appear to have developed directly in response to poor raw material quality the implication is that raw material quality alone cannot explain the apparent technological simplicity of the north chinese middle and upper paleolithic

biological marker composition of typical source rocks and related crude oils of terrestrial origin in the people s republic of china a review abstract typical source rocks and related crude oils of terrestrial origin in china come from five major environments a sedimentary formations in large lake basins in china s interior plate b lacustrine clastic rocks in fault subsidence basins c saline lake strata in fault subsidence basins d lagoonal lacustrine volcano clastic rocks in intermontane basins and e paralic coal bearing formations of the platform facies each has its specific biomarker characteristics as follows 1 environment a is poor in gammacerane and triterpane of higher plant origin 2 environment b contains abundant biomarkers especially hopanoid and steroid hydrocarbons with some triterpanes of higher plant origin 3 environment c has extremely high amounts of phytane and series of s compounds with high ratios of phytane pristane and gammacerane c30 hopane and sometimes high even carbon predominance of n alkanes 4 environment d contains abundant isoprenoid alkanes and carotanes carotane and carotane and 5 environment e is rich in biomarkers of high plants such as diterpenoid and aromatized terpenoid hydrocarbons

how mudrock and soil physical properties influence badland formation at vallcebre pre pyrenees ne spain abstract soils regoliths and their parent materials were investigated in relation to the development of badlands in the pre pyrenees in ne spain on late cretaceous mudrocks under a mountain mediterranean climate whilst all the soils in the area which are developed on mudrocks show a good structure and support a dense plant cover the bare parent materials slake very rapidly giving rise to badlands characterized by high erosion rates several physical chemical mineralogical and micromorphological properties of soils regoliths and related parent materials were analyzed in order to explain their different susceptibility to erosion and to determine which of all these properties are better related to such erosive behaviour only micromorphological and porosity properties were able to explain the erosion susceptibility whilst mineralogical chemical and physico chemical specific surface area properties were not among the aggregate stability tests performed to estimate the relationships of soil components with the susceptibility to erosion the emerson test for macroaggregate evaluation was particularly well suited although no good correlation was found between the emerson test classes and organic matter content we observed that the degree of slaking in organic rich horizons was always lower than in subsurface horizons and regoliths consequently as far as organic rich aggregates are present in the soil surface the influence of water in producing slaking swelling and then erosion will be minimum however when regoliths and rocks are uncovered the influence of water in these particular materials through freeze drying and swell shrinking will give rise to mudrock desintegration leading to accelerated erosion

shooting out the slate working with flaked arrowheads made on thin layered rocks although there are many archaeological and ethnographic evidences for the use of slate and similar rocks for flaking purpose they raised little interest among specialists leading to a general ignorance of specific problems associated with these raw materials starting from the study of several neolithic and chalcolithic slate collections of the western iberia the mechanical properties of slate and its impact on knapping process has been defined subsequently manufacturing and use of slate and phyllite projectiles have been undertaken the results show that the ease with which these materials break into sheets of uniform thickness and morphology would provide an ideal basis for a fast and easy manufacture of arrowheads in addition these projectiles have shown a penetration capability and resistance statistically equivalent to those made on more standard materials i e chalcedony or rock crystal therefore slate and other rocks with a high degree of fissility would have been very attractive to prehistoric knappers endeavouring to make arrowheads

crystallographic orientation of microcracks in quartz and inferred deformation processes a study on gneisses from the german continental deep drilling project ktb abstract this study was carried out on four gneiss samples from the german continental deep drilling project ktb taken at depths between 556 and 8633 m the crystallographic orientation of microcracks in quartz was determined by a combination of the electron channelling pattern method ecp and u stage microscopy the distinct preferred crystallographic orientations of various crack generations point to different processes of crack initiation and propagation which partly seem to be depth dependent for older healed cracks a crystalplastic initiation due to dislocation pile up and related lattice distortion is indicated by cracking normal to prominent slip directions which are a at lower or c at comparatively higher temperatures in contrast younger open cracks preferentially formed on crystallographic planes with low surface energy rhombs and prisms which is interpreted in terms of pure elastic crack mechanisms because of the thermoelastic anisotropy of quartz internal stresses resulting from thermal contraction during cooling may be the main driving force for the initiation or further propagation of cracks parallel to the c axis crack propagation preferentially affects grains with crystal lattices and operating crack mechanisms being in a direction appropriate to the applied external tectonic stresses this selective cracking explains why cracks also show constant orientations with respect to geographic directions up to regional dimensions

fluid inclusion constraints on temperatures of petroleum migration from authigenic quartz in bitumen veins abstract solid bitumens in fracture systems commonly contain microscopic crystals of authigenic quartz which were precipitated coevally with the bitumen early in the paragenesis of the fracture fillings the quartz contains primary fluid inclusions both aqueous and hydrocarbon yielding homogenization temperatures particularly in the range 95 130 c indicating minimum temperatures of entrapment during petroleum migration volumes of up to 50 entrained quartz and a predominance of aqueous inclusions indicate that the petroleum fluid had a substantial aqueous component

a simple analysis of oil induced fracturing in sedimentary rocks abstract geometric form of kerogen patches control oil induced fracturing in impermeable source rocks thin elongate kerogen flakes cause lateral fracturing kerogen has to occur in spherical or cylindrical forms to induce vertical fractures if length to width ratio of kerogen flakes is sufficiently large then lateral fractures are definitely initiated during oil generation in impermeable source rock oil and rock compressibilities and lateral to vertical stress ratio are decisive factors in vertical fracturing in impermeable rocks lateral to vertical stress ratio is generally higher than the maximum for oil induced vertical fracturing in tectonically relaxed sedimentary basins oil generation cannot initiate vertical fractures except when the lateral to vertical stress ratio is reduced below critical level either by tectonic tension or erosion of overburden when the source rock is permeable then the rate of oil seepage from kerogen into the surrounding rock is crucial in fracture initiation oil induced fractures cannot form unless permeability and hence rate of oil seepage from kerogen into the surrounding rock is non existent or negligible most source rocks have some permeability therefore oil induced fracture initiation should be a rare phenomenon

effect of crystal preferred orientations on the thermal diffusivity of quartz polycrystalline aggregates at high temperature article i nfo thermal diffusivity of synthetic quartz single crystals and natural polycrystalline aggregates were measured using a modified angstrom method at ambient pressure and up to 800 c in order to investigate the effect of crystal preferred orientation on thermal diffusivityof quartz rich rocks the thermal diffusivitytensorof quartz was determined by measuring the thermal diffusivity of an oriented synthetic quartz single crystal along the 100 and 001 directions a naturally deformed fine grained quartzite mylonite was used to compare the single crystalproperties with aggregate properties using thecrystal preferred orientations cpo measuredby the electron back scattered diffraction ebsd method and the measured thermal diffusivity tensor of quartz the three dimensional aggregate thermal diffusivity was modelled using volume averaging models in order to test the validity of these models that are only based on the properties of the constituent minerals the thermal diffusivity was then measured on oriented cores as a function of temperature along three orthogonal directions parallel to the x lineation y z pole to foliation structural frame both modelled and direct measurement of thermal diffusivity show an anisotropy of thermal diffusivity heat transport being more effective parallel to y direction and less effective parallel to the lineation x direction thermal diffusivities measured in a given direction on the natural rock are lower by less than 10 than the modelled thermal diffusivity in the same direction showing that rock imperfections have a weak effect on heat transport in addition the modelled thermal diffusivity anisotropy based on the characterization of crystal orientations and thermal diffusivity tensor shows a good agreement with measurements in both and stability field this validation of the petrophysical simulation allows for evaluating the 3d thermal diffusivity of quartz rich rocks in different crustal conditions the 3d thermal diffusivity of five naturally deformed quartzites displaying quartz fabrics expected in different crustal pressure and temperature ranges were simulated the resulting thermal diffusivity anisotropies of quartzites range between 40 and 10 depending on temperature crystallographic fabric patterns and fabric strength under crustal conditions quartzites deformed in the granulite facies display a high thermal diffusivity in the xz foliation plane whereas quartzites deformed in greenschist facies have highest thermal diffusivity in the z direction normal to the foliation plane

groundwater control on the suspended sediment load in the na borges river mallorca spain abstract groundwater dominance has important effects on the hydrological and geomorphological characteristics of river systems low suspended sediment concentrations and high water clarity are expected because significant inputs of sediment free spring water dilute the suspended sediment generated by storms however in many mediterranean rivers groundwater dominance is characterised by seasonal alternations of influent and effluent discharge involving significant variability on the sediment transport regimes such areas are often subject to soil and water conservation practices over the centuries that have reduced the sediment contribution from agricultural fields and favour subsurface flow to rivers moreover urbanisation during the twentieth century has changed the catchment hydrology and altered basic river processes due to its flashy regime in this context we monitored suspended sediment fluxes during a two year period in the na borges river a lowland agricultural catchment 319 km 2 on the island of mallorca balearic islands the suspended sediment concentration ssc was lower when the base flow index i e relative proportion of baseflow compared to stormflow bfi was higher therefore strong seasonal contrasts explain the high ssc coefficient of variation which is clearly related to dilution effects associated with different groundwater and surface water seasonal interactions a lack of correlation in the q ssc rating curves shows that factors other than discharge control sediment transport as a result at the event scale multiple regressions illustrate that groundwater and surface water interactions are involved in the sedimentary response of flood events in the winter the stability of baseflow driven by groundwater contributions and agricultural and urban spills causes hydraulic variables i e maximum discharge to exert the most important control on events whereas in the summer it is necessary to accumulate important volumes of rainfall creating a minimum of wet conditions in the catchment to activate hydrological pathways and deliver sediment to the drainage network the bfi is also related to sediment delivery processes as the loads are higher with lower bfi corroborating the fact that most sediment movement is caused by stormflow and its related factors overall suspended sediment yields were very low i e 2 yr 1 at all measuring sites such values are the consequence of the limited sediment delivery attributable to soil conservation practices low surface runoff coefficients and specific geomorphic features of groundwater dominated rivers such as low drainage density low gradient steep valley walls and flat valley floors

present day stress orientations and tectonic provinces of the nw borneo collisional margin received 23 september 2009 revised 17 may 2010 accepted 9 june 2010 published 16 october 2010 1 borehole failure observed on image and dipmeter logs from 55 petroleum wells across the nw borneo collisional margin were used to determine maximum horizontal stress sh orientations combined with seismic and outcrop data they define seven tectonic provinces the baram delta deepwater fold thrust belt exhibits three tectonic provinces its inner shelf inverted province sh is nw se margin normal its outer shelf extension province sh is ne sw margin parallel and its slope to basin floor compression province sh is nw se margin normal in the inverted province sh reflects inversion of deltaic normal faults the sh orientations in the extension and compression provinces reflect deltaic gravitational tectonics the shale and minibasin provinces have been recognized in offshore sabah in the shale province sh is n010 e which aligns around the boundary of a massif of mobile shale currently no data are available to determine sh in the minibasin province in the balingian province sh is ese wnw reflecting ese absolute sunda plate motions due to the absence of a thick detachment seen elsewhere in nw borneo the central luconia province demonstrates poorly constrained and variable sh orientations these seven provinces result from the heterogeneous structural and stratigraphic development of the nw borneo margin and formed due to complex collisional tectonics and the varied distribution and thicknesses of stratigraphic packages

short and long term studies of sediment dynamics in a small humid mountain mediterranean basin with badlands abstract badland landscapes are the main sediment sources in the vallcebre area eastern pyrenees catalonia spain short term studies up to 3 years long carried out between 1980 and 1994 were used to estimate the rates of both denudation on bare surfaces and sediment production at the plot scale to analyse the seasonal dynamics of bedrock weathering and regolith behaviour and to study the relationships between geomorphic activity and herbaceous plant colonisation since 1990 stream flow and suspended sediment loads have been monitored using three gauging stations equipped with infrared backscattering turbidimeters ultra sonic beam attenuation solids sensors and automatic water samplers the combination of the two different approaches has been useful for a better perception of the dynamics of the badland systems and to assess the long term contribution of these areas to the basin sediment loads badland erosion at the event scale for a period of 15 years was simulated with the kineros2 model and allowed the long term comparison between badland erosion and sediment yield at the small basin scale badlands are the main source of sediment in the basin for most of the events but infrequent runoff events cause the removal of sediment stores and the activation of other sediment sources the analysis of the uncertainty of sediment yield measurements for a range of record durations demonstrated that long records are needed for obtaining acceptable results due to the high interannual variability relatively low cost short term geomorphic observations may provide information useful for assessing the long term sediment production in these basins with badland areas only if the observations are used to implement a model able to simulate long term observations

diagenesis and reservoir potential of permian triassic fluvial lacustrine sandstones in the southern junggar basin northwestern china the junggar basin is one of the largest oil producing areas in china and contains upper permian lacustrine oil shales with some of the greatest hydrocarbon potental in the world in this study we present the diagenetic characteristics of permian triassic sandstones from the southern junggar basin and evaluate their reservoir potential the uppermost permian and lower triassic cangfanggou group in the southern junggar basin is characterized by alternating fluvial and lacustrine deposits whereas the middle upper triassic xiaoquangou group was deposited predominantly in a lacustrine environment fluvial and deltaic sedimentation was subordinate the sandstones of the cangfanggou and xiaoquangou groups are volcanic litharenites their detrital modes and textures of volcanic fragments suggest a primarily andesitic basaltic volcanic arc provenance early diagenesis of the sandstones is characterized by nonferroan calcite cementation grain coating pore lining clay minerals and the initial dissolution of detrital grains authigenic quartz pore filling phyllosilicates pore filling grain replacive zeolites albitized detrital plagioclase authigenic k feldspar copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received april 15 1996 revised manuscript received november 4 1996 final acceptance may 2 1997 2department of earth sciences university of western ontario london ontario n6a 5b7 canada 3school of geosciences queen s university of belfast belfast bt7 1nn united kingdom this work was done at the queen s university of belfast with funding from exxon bhp mobil and itotal which we gratefully acknowledge the karamay institute of petroleum exploration and development generously provided borehole samples geng ansong at the institute of geochemistry guangzhou academia sinica and zhou yisheng at the xinjiang institute of petroleum are thanked for assistance with field work and for valuable discussions special thanks go to the staff of the electron microscopy unit at the queen s university of belfast we also thank a h ruffell and s r lawrence for their constructive comments on an earlier version of the manuscript stable isotope analysis and ongoing research concerning the junggar basin at the university of western ontario have been supported by the natural science and engineering research council of canada the manuscript benefited substantially from critical commentary by kevin t biddle suzanne kairo w r kaiser and an anonymous reviewer