fertilizing potential of volcanic ash in ocean surface water the fertilization potential of newly erupted and well preserved ash from the 2000 hekla eruption in iceland was measured for the first time by flow through experiments as previously shown 1 the north atlantic ocean including the subarctic seas surrounding iceland is the largest net sink of the world s oceans for atmospheric co 2 owing to biological drawdown during summer 2 almost complete consumption of phosphate in chlorophyll rich areas of the north atlantic ocean might limit primary production and 3 in the southern pacific ocean and parts of the equatorial pacific ocean iron might limit primary production we found through laboratory experiments that volcanic ash exposed to seawater initially releases large amounts of adsorbed phosphate 1 7 mmol g 21 h 21 iron 37 0 mmol g 21 h 21 silica 49 5 mmol g 21 h 21 and manganese 1 7 mmol g 21 h 21 dissolution of acid aerosols adsorbed to the surface of the ash caused the high initial release of major and trace elements because of the instantaneous dissolution of adsorbed components when newly erupted volcanic ash comes in contact with the ocean surface water macronutrients and bioactive trace metals are released fast enough to become available to support primary production

linked thrust and strike slip faulting during late cretaceous terrane accretion in the san juan thrust system northwest cascades orogen washington the san juan thrust system makes up the western elements of the late cretaceous northwest cascades orogen of washington a stack of metamorphic nappes with terranes ranging in age from early paleozoic to middle cretaceous the tectonic development of the nappes is an unresolved issue important to understanding plate convergent processes operating in the north american cordillera in the creta ceous as well as at other times two terrane bounding fault zones were studied in this project the lopez and the rosario fault zones the fault zone rocks were affected by two cataclastic plastic late cretaceous deformational events d1 and d2 that included accretion and lateral motion during blueschist facies metamorphic conditions d1 produced upright folds and a subvertical axial planar s1 foliation fabric in the lopez fault zone and southwest vergent folds and gently northeast dipping axial planar s1 foliation in the rosario fault zone in the lopez fault zone d2 produced northwest striking and subvertical strike slip shear zones s2 with dominant sinistral displacements whereas in the rosario fault zone d2 generated low angle s2 shear zones and various slip crenulation fabrics formed by northwest directed thrust motion the d1 fabrics are inferred to be related to initiation of subduction related accretion of the nappes by orogen normal southwest northeast shortening and accretionary tectonics the subsequent d2 fabrics developed as temporally overlapping subduction related low angle thrusts in the rosario fault zone and high angle sinistral strike slip faults in the lopez fault zone in an overall transpressive setting due to oblique convergence this model suggests that the high angle lopez fault zone d2 was located above a gently northeast dipping thrust detachment s2 expressed by the rosario fault zone that allowed the accreted nappes to move parallel to the orogen the kinematic model cannot validate regional scale dextral terrane translation of the san juan thrust system as inferred by paleomagnetic data elsewhere in the western united states but addresses important tectonic processes caused by oblique subduction and changing plate conditions

coastal upwelling and downwelling forcing of circulation in a semi enclosed bay ria de vigo semi enclosed bays in upwelling regions are exposed to forcing related to winds currents and buoyancy over the shelf the influence of this external forcing is moderated by factors such as connectivity to the open ocean shelter by surrounding topography dimensions of the bay and freshwater outflows such bays preferred locations for ports mariculture marine industry recreational activities and coastal settlement present a range of characteristics understanding of which is necessary to their rational management observations in such a semi enclosed bay the ria de vigo in spain are used to characterize the influence of upwelling and downwelling pulses on its circulation in this location near the northern limit of the iberian upwelling system upwelling events dominate during a short summer season and downwelling events the rest of the year the ria response to the external forcing is central to nutrient supply and resultant plankton productivity that supports its high level of cultured mussel production intensive field studies in september 2006 and june 2007 captured a downwelling event and an upwelling event respectively data from eight current profiler moorings and boat based minibat adcp surveys provided an unprecedented quasi synoptic view of the distribution of water masses and circulation patterns in any ria in the outer ria circulation was dominated by the introduction of wind driven alongshore flow from the external continental shelf through the ria entrances and its interaction with the topography in the middle ria circulation was primarily related to the upwelling downwelling cycle with a cool salty and dense lower layer penetrating to the inner ria during upwelling over the shelf a warmer lower salinity and less dense surface layer of coastal waters flowed inward during downwelling without external forcing the inner ria responded primarily to tides and buoyancy changes related to land runoff under both upwelling and downwelling conditions the flushing of the ria involved shelf responses to wind pulses their persistence for a few days was sufficient to allow waters from the continental shelf to penetrate the innermost ria longer term observations supported by numerical modeling are required to confirm the generality of such flushing events in the ria and determine their typical frequency while comparative studies should explore how these scenarios fit into the range of conditions experienced in other semi enclosed bays

role of across shelf currents in the dynamics of harmful dinoflagellate blooms in the northwestern iberian upwelling harmful dinoflagellate blooms are frequent in the rias baixas which are made up of four open bays on the northwest part of the iberian peninsula the relationship between surface currents resulting from wind forcing and the microplankton composition on the shelf offshore of the rias baixas was studied from may 2001 to april 2002 the aim was to assess the role of shelf currents in the dynamics of harmful dinoflagellate blooms in the rias baixas shelf system in summer upwelling favorable northerly winds forced a variable but persistent southwestward flow on the shelf which reverted to an onshore flow following the change to downwellingfavorable southwesterly winds in autumn during winter and spring there was an intense alongshore flow to the north diatoms and dinoflagellates were common components of the microplankton community in summer although diatoms increased their abundance during summer upwelling events a dinoflagellate assemblage was also present on the shelf this dinoflagellate assemblage acquired higher importance during the intermediate periods of upwelling relaxation and during the autumn downwelling in particular when satellite images revealed the accumulation of phytoplankton in a narrow band close to the coast a dinoflagellate bloom of prorocentrum minimum 10 564 cells ml 1 and karenia cf mikimotoi 3 022 cells ml 1 developed in the interior section of the ria de vigo coincident with the onshore flow imposed by the autumn downwelling as these two species were components of the dinoflagellate assemblage present on the shelf in summer it is inferred that downwelling caused their accumulation in the interior section of the ria de vigo

black shale deposition and faunal overturn in the devonian appalachian basin clastic starvation seasonal water column mixing and efficient biolimiting nutrient recycling integrated geochemical data suggest that black shale deposition in the devonian geneseo formation of western new york was initiated by the coincidence of siliciclastic starvation and the intensification of seasonal water column stratification and mixing once established however black shale deposition was maintained through efficient recycling of biolimiting nutrients which enhanced primary productivity recycling efficiency was achieved through a positive feedback loop of oscillating benthic redox conditions that enhanced n and p regeneration from sediments sustained high primary productivity by returning nutrients to the photic zone during mixing and ensured a downward flux of organic matter that drove or enhanced the episodic development of benthic anoxia during stratification this feedback was ultimately disrupted by rising siliciclastic influx which diluted organic matter and restored benthic redox stability the abrupt overturn of diverse long standing appalachian basin marine communities may have been the result of trophic resource destabilization during geneseo deposition

trace element characterisation of cretaceous orange basin hydrocarbon source rocks trace elements in the kerogen fraction of hydrocarbon source rock samples from two wells obtained from the cretaceous units of the orange basin south africa were determined using x ray fluorescence spectrometry in order to determine their distribution and geochemical significances the concentrations of the elements as ce co cu fe mo ni pb and v determined ranged from 0 64 to 47 300 ppm for the samples analysed the total organic carbon toc values indicate that the samples are organic rich but did not show any trend with the distribution of the trace metals except ce mo and pb dendrogram cluster analysis discriminated the samples into three groups on the basis of their level of thermal maturity thermal maturity has a significant effect on the distribution of the trace metals cobalt ni and v ni ratios and cross plots of the absolute values of v and ni indicate that the samples had significant marine organic matter input the v and ni contents and v v ni ratio indicate that the organic matter of the source rocks had been deposited in reducing conditions despite the similarities in the organic matter source input and depositional environment of the organic matter of the samples from the two well cross plots of co ni versus v ni and mo ni versus co ni were able to reveal subtle differences cluster analysis of the samples was also able to reveal the subtle thermal maturity differences of the samples

lithostratigraphy and deep water setting of the upper nanaimo group upper cretaceous outer gulf islands of southwestern british columbia the upper cretaceous nanaimo group consists of extensive shaly units and lenticular bodies of sandstone and conglomerate deposited in neritic to bathyal marine paleoenvironments single sandstone and conglomerate lenses cannot be traced throughout the basin but instead tend to concentrate at particular stratigraphic levels defining crudely sheet like composite units of coarse grained rocks many of the lenticular coarse grained units rest in major channels as deep as about 550 m sand and gravel were generally transported to the west and northwest by sediment gravity flows through these channels into the basin centre recognition of widespread channeling is critical to the definition of formal lithostratigraphic units four formations and two informal members are defined here for the upper nanaimo group the top of the nanaimo group is probably truncated by a major unconformity with local relief of at least 2 km the effect of the unconformity can only be seen by mapping the orientation of offshore rid

wind induced exchange at the entrance to concepcion bay an equatorward facing embayment in central chile abstract hydrographic and underway water velocity profiles were measured at the entrance to concepcion bay an equatorward facing embayment in central chile in order to illustrate the wind induced exchange flow observations took place over a 25 h period 5 6 january 2002 during the austral summer which is characterized by upwelling winds in the region one portion of the observational transect was directly influenced by the wind and the other was protected from such influence by an island the portion of the transect influenced by wind showed a surface layer delimited by a pycnocline moving downwind owing to the direct action of wind stress this surface transport should have caused an onshore decrease of surface elevation that would drive upwind flow below the surface layer the portion of the transect protected by the island was influenced by its wake and perhaps forced by a semidiurnal tide this study is one of the few observational examples of wind induced flow that documents the wind induced exchange pattern under weak internal friction low ekman number this pattern consists of downwind flow in an upper layer delimited by the pycnocline and upwind flow below

cenozoic thermal evolution and tectonics of the coast mountains of british columbia 1 fission track dating apparent uplift rates and patterns of uplift the high relief of the coast mountains of british columbia has been produced in part by rapid late neogene uplift the relationship of this uplift to the presently diverse and complex plate tectonic regime off the west coast of british columbia however is not clear cut to study this problem the areal patterns rates and total amounts of cenozoic uplift from 50 to 55 n have been determined by using fission track dating of zircon and apatite separated from rocks collected at high and low altitudes along several traverses through the mountains accepting closure temperatures of 105 c 10 c and 175 c 20 c for apatite and zircon respectively and a likely closure temperature difference between zircon and apatite of 70 15 c paleogeothermal gradients have been measured at kemano c km 35 ma ago and near ocean falls king island c km 20 ma ago subcrustal heat flow is suggested to have significantly increased in the late neogene near king island uplift rates in the axial part of the northern 52 55 n coast mountains were 0 1 0 2 km ma from 25 to 15 ma ago this uplift was temporally and tectonically related to part of the subsidence in the adjacent queen charlotte basin uplift rates increased somewhat in the late miocene to about 0 4 km ma probably due to passage of the anahim hot spot beneath the area late miocene recent erosion in the north 52 55 n has reduced summit altitudes and been more extensive than farther south despite this relicts of miocene river valleys and topography are still locally preserved partly beneath 7 10 ma basalts the area of the present southern 50 to 52 n coast mountains was near sea level and experienced very low uplift rates 0 5 km ma of the southern coast mountains the profile of this uplift was broadly plateaulike and this uplift led to the inversion of the miocene coastal topography middle cenozoic uplift from 52 to 55 n was probably the result of denudation and diminishing uplift after the terminal paleocene eocene orogenic episode which grossly thickened the crust this middle cenozoic erosion resulted in the restoration of a normal crustal thickness late neogene uplift in the coast mountains was the result of thermal expansion in the mantle caused by a mantle hot spot near 53 n and changes in the geometry of the subducted slab farther south

continuous hydrocarbon accumulation over a large area as a distinguishing characteristic of unconventional petroleum the ordos basin north central china abstract global petroleum exploration is currently undergoing a strategic shift from conventional to unconventional hydrocarbon resources unconventional hydrocarbons in tight reservoirs show characteristics distinct from those of conventional hydrocarbon sources hosted in structural and stratigraphic traps the characteristic features include the following a hydrocarbon source and reservoir coexist porosity and permeability are ultra low nano pore throats are widely distributed hydrocarbon bearing reservoir bodies are continuously distributed there is no obvious trap boundary buoyancy and hydrodynamics have only a minor effect and darcy s law does not apply phase separation is poor there is no uniform oil gas water interface or pressure system and oil or gas saturation varies examples of unconventional hydrocarbon accumulations are the mesozoic tight sandstone oil province and the upper paleozoic tight sandstone gas province in the ordos basin north central china generally continuous hydrocarbon accumulation over a large area is a distinguishing characteristic of unconventional hydrocarbon sources because of the great potential of unconventional petroleum resources it is believed that research on such resources will be at the forefront of the future development of petroleum geology

geochemistry of archean shales from the pilbara supergroup western australia archean clastic sedimentary rocks are well exposed in the pilbara block of western australia shales from turbidites in the gorge creek group ca 3 4 ae and shales from the whim creek group ca 2 7 ae have been examined the gorge creek group samples characterized by muscovite quartzchlorite mineralogy are enriched in incompatible elements k th u lree by factors of about two when compared to younger archean shales from the yilgarn block alkali and alkaline earth elements are depleted in a systematic fashion according to size when compared with an estimate of archean upper crust abundances this depletion is less notable in the whim creek group such a pattern indicates the source of these rocks underwent a rather severe episode of weathering the gorge creek group also has fairly high b content 85 29 ppm which may indicate normal marine conditions during deposition rare earth element ree patterns for the pilbara samples are characterized by light ree enrichment lanybn 7 5 and no or very slight eu depletion eueu 0 82 0 99 a source comprised of about 80 felsic igneous rocks without large negative eu anomalies felsic volcanics tonalites trondhjemites and 20 mafic ultramafic volcanics is indicated by the trace element data very high abundances of cr and ni cannot be explained by any reasonable provenance model and a secondary enrichment process is called for

a modern vs permian black shale the hydrography primary productivity and water column chemistry of deposition the sediment currently accumulating in the cariaco basin on the continental shelf of venezuela has an elevated organic carbon content of approximately 5 is accumulating under o2 depleted bottom water conditions so42 reduction is composed dominantly of foraminiferal calcite diatomaceous silica clay and silt and is dark greenish gray in color upon lithification it will become a black shale recent studies have established the hydrography of the basin and the level of primary productivity and bottom water redox conditions these properties are used to model accumulation rates of cd cr cu mo ni v and zn on the seafloor the model rates agree closely with measured rates for the uppermost surface sediment the model is applied to the meade peak phosphatic shale member of the phosphoria formation a phosphate deposit of permian age in the northwest united states it too has all of the requisite properties of a black shale although the deposit is a world class phosphorite it is composed mostly of phosphatic mudstone and siltstone chert limestone and dolomite it has organic carbon concentrations of up to 15 is strongly enriched in several trace elements above a terrigenous contribution and is black the trace element accumulation defines a mean primary productivity in the photic zone of the phosphoria basin as moderate at 500 g m 2 year 1 organic carbon comparable to primary productivity in the cariaco basin the source of nutrient enriched water that was imported into the phosphoria basin upwelled into the photic zone and supported primary productivity was an o2 minimum zone of the open ocean the depth range over which the water was imported would have been between approximately 100 and 600 m the mean residence time of bottom water in the basin was approximately 4 years vs 100 years in the cariaco basin the bottom water was o2 depleted but it was denitrifying or no3 reducing rather than so42 reducing

observations of upwelling and relaxation events in the northern monterey bay during august 2000 1 the interplay between the point ano nuevo upwelling center an offshore anticyclonic mesoscale eddy and the waters of the monterey bay was studied during a series of up and downwelling favorable wind events during august 2000 the upwelling events were characterized by the appearance of cold salty water at point ano nuevo at the north end of the bay that subsequently spread southward across the mouth of the bay as the winds continued during the downwelling relaxation events the surface current and temperature response was dominated by the onshore translation of the offshore eddy and by local surface heating in the bay itself the circulation within the bay was cyclonic during both wind regimes but slightly more barotropic under poleward forcing the icon model a nested data assimilating sigma coordinate model was used to simulate the upwelling and relaxation events and calculate the subsurface current and density fields the model reproduced the dominant current and temperature patterns outside the bay including the southward flowing upwelling filament the movement of the offshore eddy the poleward flow off point sur and the circulation within the bay the model salinity fields at the surface and 100 m levels show that during upwelling the bay was filled with higher salinity water stemming from the point ano nuevo upwelling center to the north during downwelling the source water for both the surface and 100 m levels was the colder fresher california current water offshore which had advected southward well past point pinos during the previous upwelling event

sedimentary rocks and crustal evolution tectonic setting and secular trends a significant change in the composition of turbidites deposited at active tectonic settings is seen at the archean post archean transition in comparison to post archean active margin turbidites archean greenstone turbidites exhibit more uniform th sc ratios but with a similar average greater hree depletion gd n yb n 2 less eu depletion eu eu mostly 0 85 and an absence of low th u ratios th u 3 these data indicate that differing mantle sources and or conditions of mantle melting existed during the archean and that intracrustally differentiated rocks older cratons or young differentiated arcs were relatively unimportant as provenance components for archean turbidites in contrast some sedimentary rocks preserved in archean platformal sequences of high grade terranes display significant negative eu anomalies similar to the majority of post archean shales indicating that the general process of cratonization including intracrustal differentiation has taken place since at least 3

surface waters of the nw iberian margin upwelling on the shelf versus outwelling of upwelled waters from the rias baixas abstract a set of hydrographic surveys were carried out in the ria of vigo nw spain at 2 4 d intervals during four 2 3 week periods in 1997 covering contrasting seasons residual exchange fluxes with the adjacent shelf were estimated with a 2 d non steady state salinity temperature weighted box model exchange fluxes consist of a steady state term dependent on the variability of continental runoff and a non steady state term dependent on the time changes of density gradients in the embayment more than 95 of the short time scale variability of the exchange fluxes in the middle and outer ria can be explained by the non steady state term that in turns is correlated r 2 75 with the offshore ekman transport conversely 96 of the variability of exchange fluxes in the inner ria rely on the steady state term the outer and middle ria are under the direct influence of coastal upwelling which enhances the positive residual circulation pattern by an order of magnitude from 10 2 to 10 3 m 3 s 1 on the contrary downwelling provokes a reversal of the circulation in the outer ria the position of the downwelling front along the embayment depends on the relative importance of ekman transport q x m 3 s 1 km 1 and continental runoff r m 3 s 1 when q x r 7 2 the reversal of the circulation affects the middle ria our results are representative for the rias baixas four large coastal indentations in nw spain during the upwelling season spring and summer 60 of shelf surface waters off the rias baixas consist of fresh eastern north atlantic central water enacw upwelled in situ the remaining 40 consists of upwelled enacw that previously enters the rias and it is subsequently outwelled after thermohaline modification during the downwelling season autumn and winter 40 of the warm and salty oceanic subtropic surface water which piled on the shelf by the predominant southerly winds enters the rias

palaeoclimatic evolution during eocene and its influence on oil shale mineralisation fushun basin china the fushun basin is a small explored coal and oil shale bearing cenozoic fault basin in the liaoning province northeast china the basin mainly consists of eocene swamp to lacustrine deposits of the guchengzi to xilutian formation and contains the biggest opencast oil shale mine in asia this mine has provided an ideal opportunity to undertake palaeoclimate reconstruction in this basin based on a single geological profile and the analyses of 93 samples using various approaches namely field geological observation clay mineralogical and geochemical sr ba sr cu stable c and o isotope analyses all of which were compared with palaeobotanical data the eocene climate of fushun basin evolved from warm temperate to north subtropical and generally changed from warm humid to subhumid semiarid paleoclimatic and geochemical parameters shows that the very warm and humid climate during jijuntun formation increased the initial productivity of lake water and caused a steady stratification of the lake water then caused oxygen lack in the bottom of water productivity of the lake provides the mean origin of organic matters for oil shale formation and steady anoxic environment is beneficial for the conservation of organic matters

apatite fission track dating of the cowichan fold and thrust system southern vancouver island british columbia the cowichan fold and thrust system on southern vancouver island comprises a linked system of folds and thrust faults in crystalline and sedimentary rocks of the wrangellia terrane and its sedimentary cover the upper cretaceous nanaimo group and upper paleocene to lower eocene sandstones of the chuckanut formation apatite fission track analysis indicates that cooling below the closure temperature of fission track retention in apatite 100 20 c for both the island plutonic suite from the wrangellian basement and the nanaimo group occurred at 50 40 ma middle eocene thrusting is interpreted to have occurred immediately prior to this time in the middle eocene but after post cretaceous regional burial of the turonian to maastrichtian nanaimo group and deposition of upper paleocene and lower eocene sandstones which are involved in the deformation these timing constraints support the hypothesized temporal linkage between contraction and uplift of wrangellia during the middle eocene and continued margin normal contraction of the pacific rim terrane the crescent terrane at 45 ma

geochemical characteristics in the longmaxi formation early silurian of south china implications for organic matter accumulation abstract the organic rich early silurian sediments longmaxi formation on the yangtze platform are considered to be one of the main source rocks in south china in order to investigate the mechanism of organic accumulation multiple geochemical proxies including redox parameters s c and trace element ratios productivity indices p and ba contents and clastic influx indicator ti al ratios are presented here from the hehua section yichang hubei province the longmaxi sediments have high toc contents 3 00 10 85 avg 5 63 low pyrite sulfur contents 0 42 1 14 avg 0 59 high p 0 02 0 44 avg 0 12 and ba contents 576 65 2542 43 ppm avg 1592 17 ppm calculated s c th u ni co v cr and v v ni ratios are 0 05 0 24 avg 0 12 0 23 9 86 avg 2 30 2 65 46 24 avg 15 46 0 27 14 42 avg 3 75 and 0 36 0 96 avg 0 75 respectively s c and trace element ratios together with pyrite morphology suggest dysoxic anoxic conditions prevailed during deposition of the longmaxi intervals which was mainly caused by a worldwide marine transgression after the melting of gondwana glaciation productivity proxies indicate that the organic rich longmaxi sediments were deposited in moderate to high primary productivity water columns the consistent ti al ratios suggest a rather homogeneous nature for the detrital supply geochemical data provide a good constraint on the accumulation of organic matter and relevant oceanic environment anoxic conditions together with relatively high productivity were likely responsible for the accumulation of organic rich sediments during the longmaxi interval

the skipjack island fault zone an active transcurrent structure within the upper plate of the cascadia subduction complex abstract the skipjack island fault zone has been mapped in the san juan islands between vancouver island canada and the washington state mainland usa a decade ago interpretation of multibeam sonar seafloor imagery revealed that skipjack island an east west striking sedimentary bedrock outcrop was a fault controlled structural feature a major fault separates skipjack island from a deformed sedimentary bedrock outcrop on the seafloor to the north recently the skipjack island fault zone s morphology and extent have been explored both to the west and east of the island using multibeam echosounder bathymetry seismic reflection profiles and sediment cores the character of the skipjack island fault zone is well defined locally by the interpreted seismic reflection profiles which show active faults that displace sediments deposited since the last glacial maximum the central part of the fault zone near skipjack island appears as a near vertical structure in the shallow subsurface that has been subjected to left lateral motion as evidenced by a bedrock exposure on the seabed north of the island where folded strata bend eastward against the fault the result of drag from fault motion interpretations of recent geophysical data suggest an extension of the skipjack island fault zone farther to the west where it trends towards and possibly connects with the fulford fault on vancouver island and to the east where it either terminates north of lummi island or continues eastward onto the mainland the skipjack island fault zone is interpreted to be the northern boundary of the san juan archipelago with the devils mountain fault zone being the southern boundary both fault zones represent the longest continuous faults of the san juan archipelago this newly mapped fault zone and its zone of deformation to the north may represent the northern boundary of the cascadia forearc potential sesimicity of the skipjack island fault zone and its proximity to the steep unstable northeastern side of orcas island and the southern front of the fraser river delta poses a geohazads problem in the form of earthquakes landslides submarine slides and tsunamis

continental weathering and redox conditions during the early toarcian oceanic anoxic event in the northwestern tethys insight from the posidonia shale section in the swiss jura mountains abstract the geochemistry and mineralogy of organic rich sediments of the rietheim succession in northern switzerland were studied to evaluate the main impacts of the early toarcian oceanic anoxic event t oae 183 ma ago on the depositional environment in the nw tethys ocean the geochemical data obtained notably 13corg 13ccaco3 rock eval pyrolysis toccff support the hypothesis that the negative c isotope excursion at the onset of the t oae mainly reflects a major perturbation in the global carbon cycle rather than local environmental changes e g basinal restriction productivity rock eval pyrolysis and 13corg 15ntotal crossplots indicate that the organic matter was primarily of marine origin during the t oae and deposited in an epicontinental sea setting detrital proxies notably detritus index siliciclastic balance and ln al2o3 na2o suggest that the elevated pco2 levels and greenhouse climate prevailing during the t oae induced significant acceleration of the hydrologic cycle and an increase in continental chemical weathering rates redox sensitive proxies relative pyrite contents organic and sulfide balances v v ni ratios trace elements enrichment factors trace element toc co variation patterns and toc ptotal molar ratios indicate that the rietheim posidonia shale sediments accumulated under oxic to dysoxic bottom water conditions with more reducing conditions during the t oae anoxic and possibly euxinic these changes in redox conditions were probably induced by substantial thermohaline stratification driven by enhanced freshwater input and the recurrent influx of brackish arctic seawater into the nw tethys through the viking corridor in agreement with previous sedimentological and geochemical evidences from the nw tethys ocean in the studied succession such conditions were perhaps also responsible for sequestration of most of the regenerated p in the deeper water column by adsorption and or co precipitation into authigenic phases overall the major palaeoenvironmental changes documented in this study provide a robust example of earth s possible responses to the rapid onset of extreme greenhouse conditions

organic facies and maturation of jurassic cretaceous rocks and possible oil source rock correlation based on pyrolysis of asphaltenes scotian basin canada abstract this paper establishes source rock characterization and oil oil and oil source rock correlations of selected organic rich shale source rocks and selected light oils and condensates from jurassic and cretaceous formations of the scotian basin multiple source rocks of kerogen types iia oil prone iia iib oil and condensate prone iib condensate and gas prone iii gas prone and iv nonsource are identified in various stratigraphic horizons vitrinite reflectance and t inmax data indicate variable maturation histories in different parts of the basin which are related to differences in lithology related heat conductivity and the presence of older sediments closer to areas of rifting multiple linear regression and cluster analyses of aromatic hydrocarbon ratios reveal two oil families some kerogen type iib rock extracts match many of the light oil and condensates in terms of the aromatic hydrocarbon distributions a second family of oils could not be correlated with any of the analyzed source rock extracts pyrolysis gas chromatography of asphaltenes from the cohasset a 52 and sable island 3h 58 wells are significantly different in n alkane aromatics and phenol content the asphaltene pyrolyzates of samples from venture b 52 and s desbarres o 76 have a high aromatic content low content of n alkanes and high phenol values s desbarres which is typical of a terrestial source they correlate well with one another and also with sable island light oil the n triumph g 43 whole rock and extract asphaltene pyrolyzates are dominated by normal hydrocarbons with aromatic phenolic and thiophenic compounds in low concentrations suggesting an algal source algal type organic matter may have made a contribution to the cohasset petroleum as its asphaltene pyrolyzate is also dominated by normal hydrocarbons

controls on trace metal authigenic enrichment in reducing sediments insights from modern oxygen deficient settings any effort to reconstruct earth history using variations in authigenic enrichments of redox sensitive and biogeochemically important trace metals must rest on a fundamental understanding of their modern oceanic and sedimentary geochemistry further unravelling the multiple controls on sedimentary enrichments requires a multi element approach of the range of metals studied most is known about the behavior of fe mn and mo in this study we compare the authigenic enrichment patterns of these elements with a group whose behavior is not as well defined cd cu zn and ni in three oxygen poor settings the black sea the cariaco basin venezuela and the peru margin these three settings span a range of biogeochemical environments allowing us to isolate the different controls on sedimentary enrichment our approach relying on the covariation of elemental enrichment factors ef defined for element x as efx x al sample x al lithogenic has previously been applied to mo and u to elucidate paleoenvironmental information on for example benthic redox conditions the particulate shuttle and the evolution of water mass chemistry we find two key controls on trace metal enrichment first the concentration of an element in the lithogenic background sediment used in calculating efx controls the magnitude of potential enrichment maximum enrichment factors of 376 and 800 are calculated for mo 1 ppm in detrital sediments and cd 0 3 ppm respectively compared to values not greater than 17 in any setting for the other five metals 45 ppm to 4 5 wt in detrital sediments second there is a relationship between the aqueous concentration of the element in overlying seawater and its degree of enrichment in the sediment we further identify four important processes for delivery of trace metals to the sediment these are 1 cellular uptake especially important for zn and cd 2 interaction co precipitation with sulfide mo cu and cd 3 passive scavenging via the traditional particulate shuttle mo ni and cu and 4 an association with the benthic fe redox shuttle mn ni finally we summarize the oceanic mass balance of cd and mo and place the first constraints on the contribution of reducing sediments to the oceanic mass balance of cu zn and ni we show that reducing sediments are the ultimate repository for up to half the total output flux of these elements from the oceanic dissolved pool

strontium content of ostracods indicates lacustrine palaeosalinity individual non marine ostracod valves contain sr in proportion to the sr content of their host lake water two commonly coexisting large planktonic species mytilocypris praenuncia and australocypris robusta have a sr distribution coefficient kd sr ca of 0 082 which is independent of temperature in the range 10 18 c if the relationship between salinity and the sr content of a hydrologically simple lake is known palaeosalinities can be calculated from fossil ostracods we present here palaeosalinities for the past 10 000 yr for lake keilambete victoria calculated from ostracod sr ca of fossil material which are in striking agreement with independent interpretations of palaeosalinity the range of salinity spans 14 95 we also show that a reliable quantitative continuous indicator of lacustrine palaeosalinity is important for the elucidation of continental palaeoenvironments for palaeoclimatology and archaeology and ocean continent climatic correlations and interactions

timing of collision of the north and south china blocks controversy and reconciliation the qinling orogen was formed by the joining of the north and south china blocks but the timing of their integration has been debated for more than a decade the controversies obviously stem from different approaches to reconstruction of the integration history two contrasting lines of evidence yield two different ages for collision of the north and south china blocks middle paleozoic and late triassic the shangdan suture within the qinling was regarded in previous studies as the trace along which the north and south china blocks collided our studies however demonstrate that there are two sutures within the qinling the well documented shangdan suture and the newly discovered mianlue suture we show in this paper that the late proterozoic to early mesozoic evolution of the qinling involved interactions between the north china block the north and south qinling orogens and the south china block the middle paleozoic collision along the shangdan suture as constrained by some evidence accreted only the south qinling orogen to the southern part i e the north qinling of the north china block contemporaneous rifting of the south china block and subsequent drifting separated the south qinling from the south china block during the middle to late paleozoic the separation of the south from the north china blocks is supported by other evidence in particular geomagnetic data evidently it was the late triassic collision of the south china block with the south qinling orogen along the mianlue suture that led to final integration of the north and south china blocks

major and trace element geochemistry of the lacustrine organic rich shales from the upper triassic chang 7 member in the southwestern ordos basin china implications for paleoenvironment and organic matter accumulation abstract lacustrine organic rich shales are widespread in the upper triassic yanchang formation chang 7 member of the ordos basin however information on the short term climate evolution within the chang 7 member is still lacking and the mechanism of organic accumulation in the shales remains controversial to address these issues this study analyzes the palaeoenvironment and depositional setting of different intervals in the chang 7 member of the southwestern ordos basin and constrains the main control factors on accumulation and preservation of organic matter based on organic major and trace element data the lower chang 73 shale which contains a high abundance of thermally mature type i and ii kerogen has excellent original hydrocarbon generative potential the lower chang 73 interval has the most humid climatic condition the strongest weathering condition a euxinic bottom water condition a high paleo productivity and a low terrigenous input during the period of upper chang 73 and chang 72 the climate became somewhat drier and hotter which was marked by relatively weak weathering conditions suboxic to anoxic conditions low paleoproductivity and high terrigenous input the chang 71 was characterized by a moderately humid climate moderate weathering conditions paleoproductivity and terrigenous input the relationship among the primary productivity redox conditions clastic influx indicators and toc content suggests that primary productivity was the most critical factor controlling the enrichment of organic matter the high primary productivity during the early chang 73 interval was probably driven by the deposition of volcanic ash and was influenced by marine incursion events a warm and humid paleoclimate combined with input of volcanic ash and seawater resulted in eutrophic nutrient rich and stratified surface water during the early chang 73 period which led to algal blooms with high primary productivity a stratified water column with high primary productivity together with oxygen deficit bottom water conditions and low terrigenous input resulted in the greatest enrichment of organic matter in the lower part of chang 73 shale

major trace and platinum group element geochemistry of the upper triassic nonmarine hot shales in the ordos basin central china abstract the upper triassic chang 7 non marine hot shales have been proven to contribute to mesozoic oil reservoirs in the ordos basin central china these shales have been studied extensively in sedimentology petrology and organic geochemistry however the factors controlling the development of the shales are still ambiguously constrained this paper presents the major trace and platinum group elements pges data to address these issues the chemical index of alteration cia chemical index of weathering ciw c values and clay mineral compositions indicate that the chang 7 hot shales were developed in a humid paleoclimate the indicators of redox conditions eu eu ce ce ce anom u u th v v ni and v cr suggest that the chang 7 hot shales were developed under anoxic environment uranium enrichment average 46 10 ppm is an important distinguished signature of the chang 7 hot shales which was mainly related to synchronous volcanic ash sediments and or possibly hydrothermal fluids the pge concentrations of the chang 7 hot shales were reported for the first time here and can be subdivided into two groups the total abundances of the group one samples are relatively lower and derived mainly from detrital minerals while the group two samples are relatively higher and are also likely linked to the synchronous volcanic ash sediments and or possibly hydrothermal fluids combined with the regional geological setting we tentatively propose that the tectonics is the major control on the development of the chang 7 hot shales

rapid response to coastal upwelling in a semienclosed bay bays estuaries forced by local wind show bidirectional exchange flow when forced by remote q3 wind they exhibit unidirectional flow adjustment to coastal sea level acoustic doppler current profiler observations over 1 year show that the ria de vigo iberian upwelling responds to coastal wind events with bidirectional exchange flow the duration of the upwelling and downwelling events estimated from the current variability was 3 3 days and 2 6 days respectively vectorial correlations reveal a rapid response to upwelling downwelling in which currents lag local wind by 6 h and remote wind by 14 h less than the ekman spinup 17 8 h this rapidity arises from the ria s narrowness nonrotational local response equatorward orientation additive remote and local wind responses depth greater than the ekman depth penetration of shelf circulation into the interior and vertical stratification shear reinforcing shelf circulation similar rapid responses are expected in other narrow bays where local and remote winds act together and stratification enhances bidirectional flow

effects of winds on stratification and circulation in a partially mixed estuary 1 numerical experiments are conducted to investigate how axial winds affect stratification and circulation in the partially mixed estuary of chesapeake bay in the absence of rotational effects stratification in the estuary decreases following both down estuary and up estuary winds but stratification experiences larger reduction and takes longer to recover under up estuary winds in the presence of rotational effects wind driven lateral circulations cause the lateral straining of density field and weaken the shear in the along channel flows under the down estuary winds a counterclockwise lateral circulation steepens isopycnals in the cross channel sections while the coriolis force acting on it decelerates the downwind current in the surface layer and the upwind directed current in the bottom layer under the up estuary winds a clockwise lateral circulation flattens isopycnals in the cross channel sections and reduces the shear between the surface and bottom currents hence in the presence of rotational effects the lateral straining offsets the effects of longitudinal straining such that the asymmetry in stratification reduction is significantly reduced between the down estuary and up estuary winds regime diagrams based on wedderburn w and kelvin ke numbers are constructed to summarize the net effects of winds on estuarine stratification during both wind perturbation and postwind adjustment periods

the influence of source rock type chemical weathering and sorting on the geochemistry of clastic sediments from the quetico metasedimentary belt superior province canada abstract the geochemistry of clastic sediments is controlled by at least four factors source rock composition weathering of the source rocks sorting of the weathered detritus and post depositional alteration during diagenesis and metamorphism in order to evaluate the relative importance of these factors major trace and rare earth element contents were determined for distal and proximal clastic turbidites from the archaean quetico metasedimentary belt the degree of metamorphism of the samples ranges from middle greenschist to upper amphibolite facies simple mixing of archaean mafic and acidic rocks of similar composition to those found in the adjacent granite greenstone terrains will account for the tio2 feot mgo cr sc y and hree contents of the clastic turbidites the metasediments are enriched in lree relative to the mafic acidic rock mixing line indicating that the acidic source was enriched in the lree compared to archaean terrains from other parts of the world some quetico turbidites have an additional fe rich source component possibly a chemical sediment incorporated at the time of turbidite slumping cao na2o k2o rb and sr form trends on bivariant plots that are oblique to the mafic acidic rock mixing line and hence cannot be accounted for by simple mixing of the source rocks chemical weathering of feldspars prior to deposition can account for cao na2o k2o rb and sr trends since cao na2o and sr are lost to the weathering solutions and k2o and rb are retained on the product clays the higher na 2 o cao k 2 o na 2 o rb k 2 o and sr cao ratios but lower cao content of the distal samples suggest that they were derived from a bulk sediment that had experienced a greater degree of chemical weathering than the proximal sediments sorting is the factor that most strongly influences the composition of individual samples within the proximal sample group the coarse grained metagraywackes with their higher quartz feldspar and heavy mineral contents are enriched in sio2 cao na2o sr lree zr and hf relative to the fine grained clay rich metapelites metapelites are enriched in tio2 al2o3 feot mgo k2o cr zn sc y hree cs and rb as a result of their higher clay contents thus the use of clastic sediment compositions in determining average crustal compositions e g for the ree can only give satisfactory results when all grain size fractions are sampled in their correct relative proportions the chemical differences observed between the high and low grade samples can be accounted for by source rock type chemical weathering of the source rocks or sorting post depositional element mobility does not appear to be an important factor in determining the composition of the quetico metasediments

internal tide dissipation mixing and vertical nitrate flux at the shelf edge of ne new zealand an internal tide on the ne shelf of new zealand was observed with a combination of moored temperature loggers and current meters and vertical profiling with a microstructure probe internal tide energy flux across the shelf edge was calculated to be 400 w m with considerable variability driven by the passage of a storm through the region energy associated with the internal tide was significantly greater than the energy of the barotropic tide or of inertial shear dissipation of the internal tide calculated from the energy loss between two of the moorings was estimated to be 15 10 mw m 2 the associated vertical eddy diffusivity was 4 3 x 10 4 m 2 s 1 the microstructure observations indicated internal tide driven vertical diffusivities at the nitracline of 7 x 10 4 m 2 s 1 the observations of vertical eddy diffusivities are combined with measurements of the vertical nitrate gradient to suggest that mixing driven by the internal tide is the dominant mechanism for driving diapycnal nutrient supply during summer the calculated flux of about 12 mmol n m 2 d 1 into the photic zone is suggested to drive significant new subsurface production throughout the summer amounting to a possible contribution to annual new production on the shelf of 100 g c m 2

remagnetization during cretaceous normal superchron in eastern san juan islands wa implications for tectonic history abstract the eastern san juan islands expose an island arc ophiolite sequence and one or more ocean floor terranes cover rocks of the former including red radiolarian tuff and arc derived sandstone have no penetrative fabric and lack high pressure minerals in contrast pillow basalts and ribbon cherts of the latter are strongly deformed and the overlying metagraywacke is folded with a penetrative axial plane cleavage all ocean floor rocks have aragonite in veins indicative of higher pressure conditions than experienced by the island arc rocks a downward magnetization is common to the ocean floor rocks consistent with widespread remagnetization during the cretaceous normal superchron this magnetization is carried by magnetite and in red rocks by hematite fluid flow during or after deformation and high p metamorphism likely facilitated remagnetization at low temperature the magnetic directions are somewhat scattered but most are moderately to steeply down to the southeast they are far from directions expected with or without northward transport of baja bc rotation of observed directions into agreement with those expected for either present or more southerly locations also rotate structural elements in the host rocks three alternative rotation histories explored here all produce structural reconstructions that differ considerably from the present structure a tectonic history of the eastern san juan islands based on any of these reconstructions would be superior to one based on present attitudes of structures this is because at least a constraint that the restored paleomagnetic directions match a paleomagnetic field direction is satisfied choices among alternative reconstructions would become clearer with better understanding of relative ages of specific structures and their magnetizations improved geologic understanding of the regional setting where the rocks could have been deformed and remagnetized would also help

surface water subduction during a downwelling event in a semienclosed bay the ria de vigo is a bay strongly influenced by upwelling downwelling cycles along the adjacent coast of nw iberia moored and ship board observations during september 2006 showed that subduction initially associated with an estuarine circulation strengthened when a strong downwelling circulation resulting from northward wind over the coastal ocean was generated in the outer ria causing ambient waters to be advected outward in the lower layer incoming surface waters confined the estuarine circulation to the shallow interior and displaced isopleths downward through the water column at 10 m d 1 as the estuarine circulation retreated inward strong flow convergence developed between middle and inner ria in the layer above 15 m while divergence developed beneath the convergence increased through the period of downwelling favorable wind at a rate consistent with the observed isopleth displacement velocities the coefficient of turbulent diffusion kt from a microstructure profiler indicated that mixing was strong in the estuarine circulation and subsequently in the downwelling zone where localized instabilities and temperature salinity inversions were observed during the downwelling concentrations of phytoplankton including potentially harmful species increased especially in the middle and inner ria as a result of inward advection subduction and the ability of the dinoflagellates to maintain their position in the water column by swimming in the course of the 5 day event the water mass of all but the innermost ria was flushed completely and replaced by waters originating in the coastally trapped poleward flow along the atlantic coastline this article is protected by copyright all rights reserved

lacustrine source rock deposition in response to co evolution of environments and organisms controlled by tectonic subsidence and climate bohai bay basin china three paleogene syn rift intervals from the bohai bay basin the most petroliferous basin in china were analyzed with sedimentological and geochemical techniques to characterize the lateral source rock heterogeneities to reveal the environmental and ecological changes through geologic time and to construct depositional models for lacustrine source rocks under different tectonic and climatic conditions the third es3 and first es1 members of the eocene shahejie formation and the oligocene dongying formation ed display widely variable total organic carbon contents hydrogen indices and visual kerogen compositions suggesting changes in organic facies from deep to marginal sediments carefully selected deep lake facies samples from any interval however display fairly uniform biomarker composition these three intervals have distinctly different biomarker assemblages which indicate weakly alkaline freshwater lakes with a moderately deep thermocline during es3 deposition alkaline saline lakes with shallow chemocline during es1 deposition and acidic freshwater lakes with deep unstable thermocline during the deposition of the dongying formation such environmental changes corresponded to changes in subsidence rate and paleoclimate from rapid subsidence and wet climate during es3 deposition through slow subsidence and arid climate during es1 deposition to rapid subsidence and wet climate during ed deposition and resulted in synchronous changes in terrigenous organic matter input phytoplankton community and primary productivity the co evolution of environments and organisms controlled by tectonic subsidence and climate accounted for the deposition and distribution of high quality lacustrine source rocks with distinctly different geochemical characteristics most rift basins experienced changes in subsidence rates and possibly changes in climates during their syn rift evolutions the models constructed in this paper may have important implications for source rock prediction in other lacustrine rift basins

organic geochemistry and reservoir characterization of the organic matter rich calcilutite in the shulu sag bohai bay basin north china abstract although extensive studies have been conducted on unconventional mudstone shales reservoirs in recent years little work has been performed on unconventional tight organic matter rich fine grained carbonate reservoirs the shulu sag is located in the southwestern corner of the jizhong depression in the bohai bay basin and filled with 400 1000 m of eocene lacustrine organic matter rich carbonates the study of the organic matter rich calcilutite in the shulu sag will provide a good opportunity to improve our knowledge of unconventional tight oil in north china the dominant minerals of calcilutite rocks in the shulu sag are carbonates including calcite and dolomite with an average of 61 5 wt the carbonate particles are predominantly in the clay to silt size range three lithofacies were identified laminated calcilutite massive calcilutite and calcisiltite calcilutite the calcilutite rocks including all the three lithofacies in the third unit of the shahejie formation in the eocene es3 have total organic carbon toc values ranging from 0 12 to 7 97 wt with an average of 1 66 wt most of the analyzed samples have good very good or excellent hydrocarbon potential the organic matter in the shulu samples is predominantly of type i to type ii kerogen with minor amounts of type iii kerogen the temperature of maximum yield of pyrolysate tmax values range from 424 to 452 c with an average of 444 c indicating most of samples are thermally mature with respect to oil generation the calcilutite samples have the free hydrocarbons s1 values from 0 03 to 2 32 mg hc g rock with an average of 0 5 mg hc g rock the hydrocarbons cracked from kerogen s2 yield values in the range of 0 08 57 08 mg hc g rock with an average of 9 06 mg hc g rock and hydrogen index hi values in the range of 55 749 mg hc g toc with an average of 464 mg hc g toc the organic rich calcilutite of the shulu sag has very good source rock generative potential and have obtained thermal maturity levels equivalent to the oil window the pores in the shulu calcilutite are of various types and sizes and were divided into three types 1 pores within organic matter 2 interparticle pores between detrital or authigenic particles and 3 intraparticle pores within detrital grains or crystals fractures in the shulu calcilutite are parallel to bedding high angle and vertical having a significant effect on hydrocarbon migration and production the organic matter and dolomite contents are the main factors that control calcilutite reservoir quality in the shulu sag

revised ages of blueschist metamorphism and the youngest pre thrusting rocks in the san juan islands washington new ages of rocks in the san juan islands northwest washington significantly change our understanding of the evolution of the san juan islands thrust system re examination of foraminifera bearing mudstones at richardson on lopez island indicates a late aptian 112 115 ma not late albian 100 ma age as currently presented in the literature the age brackets of thrusting marked by these pre thrusting mudstones and 84 ma post thrusting sedimentary rocks span a much longer period than previously thought diminishing controls on rates of displacement in the thrust system and the timing of regional deformation in western washington new 40 ar 39 ar plateau ages of phengite in blueschist facies meta volcanic rock also at richardson are 124 0 7 ma 2 late barremian these blueschist facies volcanic rocks are in fault contact with the fossiliferous mudstones therefore the blueschist facies metamorphism at richardson previously inferred to be associated with the thrusting now appears to have occurred prior to thrusting further the ar ages demonstrate that blueschist facies fabric formed earlier than the thrust event and is therefore not directly useful in analyzing the thrusting kinematics the richardson 40 ar 39 ar age is similar to isotopic ages found in the eastern san juan islands and in the shuksan blueschist terrane in the northwest cascades and thus fits into an emerging regional age pattern of blueschist facies metamorphism during late jurassic early cretaceous up to barremian but not late albian cenomanian if this pattern is more broadly confirmed for the san juan islands all the blueschist facies metamorphism can be regarded as having formed in subduction zones elsewhere along the continental margin rather than in the anomalous setting of an on land thrust system as in the san juan islands resume de nouveaux ges pour les roches des iles san juan dans le nord ouest de l etat de washington changent profondement notre comprehension de l evolution du systeme de chevauchement san juan un reexamen des mudstones foraminiferes a richardson sur l ile lopez indique un ge aptien tardif 112 115 ma et non albien tardif 100 ma tel qu indique actuellement dans la litterature les plages d ges pour le chevauchement marquees par ces mudstones precedant le chevauchement et des roches sedimentaires 84 ma posterieures au chevauchement couvrent une periode beaucoup plus grande que stipulee anterieurement diminuant les controles sur les taux de deplacement dans le systeme de chevauchement et le moment de la deformation regionale dans l ouest de l etat de washington de nouveaux ges plateaux 40 ar 39 ar de la phengite dans des roches volcaniques au facies des schistes bleus aussi a richardson datent

multiple controls on the preservation of organic matter in devonian mississippian marine black shales geochemical and petrographic evidence geochemical and petrographic analysis of an interval of black shales between the huron shale member of the new albany shale upper devonian famennian and the sunbury shale lower mississippian tournaisian suggests that multiple controls influenced the accumulation of organic matter stratigraphic trends were determined following detailed analysis of a core from the central appalachian basin d6 montgomery county ky specifically c s fe relationships mo v v ni ni co and v cr were used to assess paleo redox conditions during sediment accumulation the role of clastic input was evaluated using ti al k al and si al and c p was used as a proxy for paleoproductivity the terrestrial to marine maceral ratio t m vitrinite plus inertinite alginite plus bituminite was used to evaluate changes in om source c s fe relationships and trace element ratios suggest anoxic conditions prevailed during deposition of much of the upper part of this interval however bottom water conditions were intermittently dysoxic during accumulation of the huron shale member and possibly dysoxic to marginally oxic during accumulation of the lowermost huron shale member productivity appears to have been an important factor in the accumulation of corg and high c p ratios are consistent with a productivity anoxia feedback mechanism in addition nutrients from increased terrestrial weathering may have contributed to enhanced productivity variations in sediment influx may also have influenced corg concentrations through sediment starvation one of the more significant observations in this work is an increase in terrestrial om inertinite and vitrinite up section which may reflect vegetative changes occurring on land during this time interval most of this increase is due to inertinite much of which appears to be fusinitic in origin and hence may be fossil charcoal this latter observation has implications for the expansion of land plants into drier niches and for late devonian atmospheric oxygen levels introduction of more resistant terrestrial om to anoxic basins may have been an important factor in the preservation of high carbon 10 intervals especially in the cleveland member of the new albany shale upper devonian famennian and the sunbury shale lower mississippian tournaisian

the ciw index a new chemical index of weathering abstract a new chemical index of weathering that can be applied to modern soils and precambrian paleosis is proposed ciw al2o3 the value of this index increases as the degree of weathering increases and the difference between ciw index values of the silicate parent rock and soil or sediment reflects the amount of weathering experienced by the weathered material

dynamics of oxygen depletion in the nearshore of a coastal embayment of the southern benguela upwelling system acquisition of high resolution time series of water column and bottom dissolved oxygen do concentrations inform the dynamics of oxygen depletion in st helena bay in the southern benguela upwelling system at several scales of variability the bay is characterized by seasonally recurrent hypoxia 1 42 ml l 1 associated with a deep pool of oxygen depleted water and episodic anoxia 0 02 ml l 1 driven by the nearshore 20 m isobath decay of red tide coastal wind forcing influences do concentrations in the nearshore through its influence on bay productivity and the development of red tides through shoreward advection of the bottom pool of oxygen depleted water as determined by the upwelling downwelling cycle and through its control of water column stratification and mixing a seasonal decline in bottom do concentrations of 1 2 ml l 1 occurs with a concurrent expansion of the bottom pool of oxygen depleted water in st helena bay upwelling of this water into the nearshore causes severe drops in do concentration 0 2 ml l 1 particularly during end of season upwelling resulting in a significant narrowing of the habitable zone episodic anoxia through the entire water column is caused by localized degradation of red tides within the confines of the shallow nearshore environment oxygenation of the nearshore is achieved by ventilation of the water column particularly with the onset of winter mixing no notable changes are evident in comparing recent measures of bottom do concentrations in st helena bay to data collected in the late 1950s and early 1960s

analysis of marine environmental conditions based onmolybdenum uranium covariation applications to mesozoic paleoceanography article i nfo article history accepted 13 september 2011 available online 17 september 2011 patterns of uranium molybdenum covariation in marine sediments have the potential to provide insights re garding depositional conditions and processes in paleoceanographic systems specifically such patterns can be used to assess bottom water redox conditions the operation of metal oxyhydroxide particulate shuttles in the water column and the degree of water mass restriction the utility of this paleoenvironmental proxy is due to the differential geochemical behavior of u and mo 1 uptake of authigenic u by marine sediments begins at the fe ii fe iii redox boundary i e suboxic conditions whereas authigenic mo enrichment re quires the presence of h2s i e euxinic conditions and 2 transfer of aqueous mo to the sediment may be enhanced through particulate shuttles whereas aqueous u is unaffected by this process in the present study we examine u mo covariation in organic rich sediments deposited mostly in the western tethyan region during oceanic anoxic events oaes of early jurassic to late cretaceous age our analysis generally confirms existing interpretations of redox conditions in these formations but provides significant new insights regard ing water mass restriction and the operation of particulate shuttles in depositional systems these insights will help to address contentious issues pertaining to the character and origin of mesozoic oaes such as the degree to which regional paleoceanographic factors controlled the development of the oaes

arc parallel extension and fluid flow in an ancient accretionary wedge the san juan islands washington structural analysis of the lopez structural complex a major late cretaceous terrane bounding fault zone in the san juan thrust system reveals a sequence of events that provides insight into accretionary wedge mechanics and regional tectonics after formation of regional ductile flattening and shear related fabrics the area was crosscut by brittle structures including 1 southwest vergent thrusts 2 extension veins and normal faults related to northwest southeast extension and 3 conjugate strike slip structures that record northwest southeast extension and northeast southwest shortening aragonite bearing veins are associated with thrust and normal faults but only rarely with strike slip faults high pressure low temperature hp lt minerals constrain the conditions for brittle deformation to 20 km and

fission track dating of the tectonic development of the san juan islands washington the san juan islands of washington state form a geologically complex province located between the north cascades vancouver island and the olympic peninsula we have obtained 53 fission track dates from the san juan islands province that help constrain its late paleozoic to early cenozoic tectonic and sedimentary history and its relationship to neighboring geologic terranes the san juan islands can be divided into two main blocks separated by the haro fault south of the haro fault complexly deformed metamorphosed and probably exotic early paleozoic to early late cretaceous rocks form four imbricate thrust plates separated by south and east dipping late early to late cretaceous thrust faults reset zircon fission track dates indicate that thrusting may have produced an upside down geothermal gradient in the uppermost plate the decatur terrane if present this gradient was probably produced by conductive or frictional heating associated with a now eroded overlying thrust fault and hot thrust plate

modeling the residual circulation of a coastal embayment affected by wind driven upwelling circulation of the ria de vigo nw spain 1 the barotropic and baroclinic nontidal circulations of the ria de vigo nw spain are studied using the three dimensional finite difference model hamsom hamburg shelf ocean model the external forcing acting on the system includes winds freshwater inflow in the inner part of the ria and all over its surface and heat exchange with the atmosphere modeled velocity is compared with data from an aanderaa dcm12 acoustic doppler current meter at one site of the ria and predicted salinity and temperature fields contrasted with seabird conductivity temperature depth data along the main channel of the ria all predicted current salinity and temperature fields are in good agreement with experimental data a new residual circulation pattern of the ria de vigo and its dependence on coastal winds is described according to this pattern the typical estuarine two layer circulation overlays in the outer part of the ria with a lateral circulation resulting in a three dimensional dynamics the lateral circulation is induced by interaction between the southward northward alongshore coastal jet associated with upwelling downwelling winds and the topographic configuration of the ria

an inshore poleward current in the nw of the iberian peninsula detected from satellite images and its relation withg catenatum and d acuminata blooms in the galician rias abstract toxic gymnodinium catenatum blooms usually occur in the galician rias at the end of the upwelling season which necessitates a ban on harvesting shellfish extraction with subsequent economic losses for this sector one of the possible causes cited in the literature is the advection of populations from outside the area but no evidence was available to substantiate this oceanographic conditions at the end of the upwelling season in the nw coast of the iberian peninsula 39 43 n have been studied for the years 1986 1990 1995 and 1998 sea surface temperature data from satellite images wind data drifter tracks and in situ oceanic data from the galician rias have been combined to clarify the oceanographic structures in the area at the commencement of the blooms on the inner shelf an inshore poleward current advecting warm water has been identified after the cessation of upwelling on the middle and outer shelf a tongue of cold water as a remnant of the previous upwelling continued to move southward on the slope and offshore the poleward counter current reported by several authors was detected carrying warm oceanic water northwards it is suggested that the inshore poleward current not previously reported in the literature could advect initial populations of dinoflagellates to the rias from northern portuguese waters this would explain why blooms such as g catenatum have been found usually in portuguese waters several weeks before the galician rias showing an apparent northward movement but cells of this toxic dinoflagellate species have not been found in waters of the offshore poleward counter current

distribution of phosphorus in sediments from tomales bay california abstract the distribution of phosphorus among six sequentially extracted fractions was determined in suspended load and bottom sediments from lagunitas creek and tomales bay california the sequential extraction scheme was a modification of the sedex scheme of ruttenberg 1992 using the surfactant sodium dodecyl sulfate sds to extract organic phosphorus sds effectively removed organic phosphorus from sediments with little interference from inorganic phosphorus containing phases the distribution of phosphorus in the sequentially extracted fractions was similar in suspended load and bottom sediments collected from lagunitas creek and the bay the concentration of phosphorus in cdb extractable iron oxide phases was below detection in all samples most of the phosphorus 70 80 contained in these sediments was found in the organic and residual phases porewaters from sediment cores were analyzed for dissolved inorganic carbon ammonium phosphate sulfate iron calcium and fluoride within bay sediments porewaters were depleted in phosphate relative to dissolved inorganic carbon and ammonium suggesting that phosphate released from organic matter decomposition is being removed from the porewaters sequential extraction results suggest that approximately 15 of the phosphate released from organic matter decomposition could be removed from the porewaters by adsorption into the exchangeable phosphorus fraction and an additional 3 may be precipitated as authigenic phosphate minerals the remaining phosphate 82 released from organic matter decomposition must be either taken up within the sediment mixed layer 0 40 cm or escapes to the overlying water column

axial wind effects on stratification and longitudinal salt transport in an idealized partially mixed estuary abstract a 3d hydrodynamic model regional ocean model system roms is used to investigate how axial wind influences stratification and to explore the associated longitudinal salt transport in partially mixed estuaries the model is configured to represent a straight estuarine channel connecting to a shelf sea the results confirm that wind straining of the along channel salinity gradient exerts an important control on stratification two governing parameters are identified the wedderburn number w defined as the ratio of wind stress to axial baroclinic pressure gradient force and the ratio of an entrainment depth to water depth hs h here w controls the effectiveness of wind straining which promotes increases decreases in stratification during down estuary up estuary wind the ratio hs h determines the portion of the water column affected by direct wind mixing while stratification is always reduced by up estuary wind stratification shows an increase then decrease transition when down estuar

glacial interglacial variability in the eastern tropical north pacific oxygen minimum zone recorded by redox sensitive trace metals 1 changes in the intensity of the oxygen minimum zone omz in the eastern tropical north pacific over the past 140 kyr are recorded as enrichments and depletions of redox sensitive metals in sediments of two piston cores one within and one below the modern omz from the continental margin off mazatlan mexico 22 41 n 106 28 w concentrations of al 7 7 0 6 ti 0 37 0 03 fe 3 1 0 25 mn 320 31 ppm and ba 560 82 ppm in core nh15p within the omz at 420 m water depth were relatively constant over the last 110 kyr in contrast concentrations of cd 4 8 2 ppm cu 29 8 9 1 ppm u 9 1 3 7 ppm mo 12 1 5 0 ppm v 138 2 51 9 ppm and re 45 8 25 5 ppb were all at least 30 higher in interglacial stages compared to glacial stages concentrations of al 7 4 0 3 ti 0 35 0 03 fe 3 5 0 4 and mn 385 77 ppm in core nh22p below the omz at 2025 m water depth were comparable to those in core nh15p while concentrations of ba 1662 292 ppm were about a factor of three higher in contrast concentrations of cd 0 9 0 3 ppm u 6 6 0 9 ppm mo 3 2 1 2 ppm v 81 8 10 1 ppm and re 25 4 12 ppb were lower in sediments of comparable age than the concentrations of these same metals in the omz core and the differences in their concentrations over glacial interglacial cycles were less pronounced than those in shallower core comparison of the nonlithogenic fraction of metals in the sediments with their estimated contribution from plankton suggests that organic matter is probably the major source of cu ba and perhaps cd to the sediment whereas the indirect effects of organic carbon and low bottom water oxygen concentrations on sediment redox state appear to be more important controls on the distributions u re mo and v changes in the depth at which re and mo precipitated in the sediments and in the re mo ratio suggest that the redox state of the surface sediment and overlying water at both core depths varied over time re and mo removal depths were shallower and re mo ratios were lower at the omz site than in deeper water suggesting that a more reducing environment prevailed over time at the shallower site although the redox state of the waters and sediment at both sites varied over glacial interglacial cycles the omz likely was never anoxic in the last 140 kyr this variability in redox state could be attributed to changes in regional export productivity changes in ocean circulation or a combination of both processes a paleoproductivity reconstruction from biogenic ba data suggests that glacial productivity was considerable lower than it was during interglacial stages model results suggest that the oxygen penetration depth an indicator of sediment redox state changed less than 1 cm as a result of the change in productivity changes in oxygen penetration depth estimated from re and u removal depths are significantly larger suggesting that changes in ventilation are a more important control on sediment redox state overall trace metal results confirm the tight coupling between ocean circulation marine productivity and global change

secular distribution of biogenic silica through the phanerozoic comparison of silica replaced fossils and bedded cherts at the series level abstract the modern marine silica cycle is dominated by silica secreting phytoplankton principally diatoms but this cycle has evolved considerably during the phanerozoic we analyzed the temporal distribution of silica replaced fossils and bedded chert to determine the influence of factors such as extinctions and climate change on siliceous facies trends in silica replacement of fossils match faunal radiations during the ordovician and siluro devonian with peaks in silica replacement in the late ordovician and middle devonian corresponding to peaks in the abundance and diversity of siliceous sponges sharp drops in the abundance of silica replaced fossils and or bedded cherts coincide with four of the five major mass extinctions no discernible decrease marks the extinction at the end of the triassic we expected peaks in bedded chert deposition during glacial episodes because enhanced ocean circulation should favor more and stronger upwelling orogenic episodes which may trigger continental glaciati

fission track evidence for late triassic oceanic crust in the french occidental alps five zircons and one apatite from plutonic rocks of the ophiolitic sequence from the piemontese zone western alps southeast france have been dated by the fission track method the ages obtained indicate that the minimum age of the alpine oceanic crust in this zone is between 192 6 and 212 8 m y late triassic liassic consideration of the available data on fission track retention conditions in zircons and pressure temperature conditions allowed by the high pressure mineralogic assemblages of the rocks leads to the conclusion that in the external part of the piemontese zone the temperature duration conditions of the high pressure alpine metamorphism were inadequate to significantly reset the zircons9 fission track clock suggesting a short lived metamorphic event

exchange fluxes between the ria de vigo and the shelf a bidirectional flow forced by remote wind 1 in the ria de vigo western coast of the iberian peninsula the seasonal pattern associated with shelf winds at these latitudes produces upwelling downwelling episodes that affect the residual circulation the aim of this paper is to go deeply into the interaction between remote winds and the dynamics of the ria aided by an inverse model in the galician r ias the box models inverse models have been developed from a two dimensional 2 d point of view since the classical baroclinic residual circulation in positive estuaries has a vertical distribution freshwater outflow through the surface layer and inflow through the bottom layer however recent work in the ria de vigo has shown the existence of a 3 d residual circulation in the seaward region of the ria during upwelling downwelling conditions a coastal jet enters leaves the ria through the northern mouth and leaves enters through the southern mouth the inverse model developed in this paper is a 3 d kinematic box model based on tracer and volume balances with the constraint of nonnegative vertical exchange coefficients the fluxes obtained confirm during some periods the 3 d residual circulation overlying the classical 2 d scheme it is shown how the 3 d pattern affects the inner ria causing transversal differences in the flow field in addition the model results have been helpful in the discussion of a possible barotropic bidirectional flow associated with remote winds the results have set the basis for the existence of a bidirectional flow originated by a barotropic interaction with the shelf upwelling

turbulence in an estuarine embayment observations from beatrix bay new zealand 1 this study characterizes turbulence in a stratified estuarine embayment using measurements of temperature gradient microstructure the water column was generally strongly stratified with only moderate tidal forcing dissipation levels and turbulence length scales in the surface mixing layer the pycnocline the fluid interior and the benthic boundary layer were measured and compared with expectations based on previous work in different systems parameters important for modeling including the measured dissipation ratio d and the gradient richardson number rig were calculated the observations highlight a number of points 1 the lack of strong tidal flows means that buoyancy effects in estuarine embayments are more important than in the estuary proper 2 the combination of reduced tidal mixing and interacting thermohaline stratification suggests the importance in certain situations of diffusive convection 3 despite the shallow depths 40 m a number of hydrodynamic regimes vertically adjacent to one another exist resulting in a highly variable distribution of turbulence properties

stratigraphy depositional setting and tectonic significance of the clastic cover to the fidalgo ophiolite san juan islands washington the san juan islands of northwest washington state comprise a diverse assemblage of paleozoic and mesozoic terranes amalgamated during a regional cretaceous orogenic event detailed tectono stratigraphy of the sedimentary cover to the fidalgo complex indicates the presence of several stratigraphically distinct units which are described and formalized in this paper the fidalgo complex and its sedimentary cover are the structurally highest rocks in the san juan thrust system the fidalgo complex is a highly disrupted middle to upper jurassic ophiolite with arc related intrusives volcanics and sediments the trump unit is an informally named sequence of siliceous sediments volcanic graywacke and minor volcanics that occurs at the stratigraphically highest portion of the fidalgo complex complex facies lithologies and provenance indicate that deposition of this oxfordian to upper tithonian unit occurred in an arc proximal setting the upper tithonian and younger lummi group elevated here lies depos

the eocene southern vancouver island orocline a response to seamount accretion and the cause of fold and thrust belt and extensional basin formation abstract a deflection of the fault controlled southwestern coastline of vancouver island suggests the presence of a minor orocline with a southern crustal block south of barkley sound alberni inlet rotated 20 counterclockwise relative to a northern fixed crustal block about a pole of rotation located northeast of port alberni in this paper two models of orocline development one of pure block rotation and one of pure bending are proposed the predictions of these models are tested against available geological maps structural orientation data identified regions of extension and contraction and paleomagnetic data structural orientation and paleomagnetic data are consistent with 18 of post late cretaceous counter clockwise rotation of the southern crustal block relative to the northern fixed crustal block a southward increase in the magnitude of rotation evident in the structural orientation data argues for a model of bending both bending and block rotation models predict the development of a zone of contraction along the northeast margin of the southern crustal block coincident with the location of the eocene cowichan fold and thrust belt that diminishes northward toward the pole of rotation as predicted the fold and thrust belt is characterized by a northerly decrease in the amount of shortening from 30 at the south end of the thrust belt to 0 shortening north of port alberni the northerly decrease in shortening is complemented by a north to south change in structural style from cylindrical to conical folds and finally to planar undeformed strata the model of block rotation predicts the presence of a zone of extension extending southwest from the zone of rotation coincident with the location of eocene extensional structures within barkley sound and with horst and graben structures in the offshore eocene to miocene tofino basin extension is less than predicted by a model of pure block rotation and suggests that much of the oroclinal rotation was accommodated by bending timing constraints indicate that orocline development was coeval with and resulted from the eocene accretion of seamounts of the crescent terrane these findings demonstrate that oroclinal orogeny the buckling of a linear crustal beam about vertical axes of rotation can significantly impact the geometry structure and character of an orogenic belt even where the buckles are minor

rare earth and major element geochemistry of eocene fine grained sediments in oil shale and coal bearing layers of the meihe basin northeast china abstract the meihe basin is a paleogene pull apart basin long flame coal lignite and oil shale are coexisting energy resources deposited in this basin ninety seven samples including oil shales coals brown to gray silt and mudstone have been collected from the oil shale and coal bearing layers to discover the rare earth element geochemistry the total ree contents of oil shales and coals are 137 256 g g and 64 152 g g respectively the chondrite normalized patterns of oil shales and coals show lree enrichments hree deficits negative eu anomalies and negligible ce anomalies the chemical index of alteration cia as well as some trace elements is often used to reflect the paleoenvironment at the time of deposition the results show that fine grained sediments in both layers were deposited in dysoxic to oxic conditions and in a warm and humid climate and coals were deposited in a warmer and more humid climate than oil shales oil shales and coals are both in the early stage of diagenesis and of terrigenous origin besides diagrams of some major trace and rare earth elements show that the fine grained sediments of both layers in the meihe basin are mainly from the felsic volcanic rocks and granite and that their source rocks are mostly deposited in the continental inland arc setting the analysis of major elements shows that si al k and ti in both layers are found mainly in a mixed clay mineral assemblage and that si is also found in quartz sodium occurs primarily in clay minerals whereas ca is found mainly in the organic matter in the coal bearing layer iron is mainly controlled by organic matter rather than detrital minerals in contrast in the oil shale bearing layer neither detrital minerals nor organic matter exert a control on the iron content analyzing the relationship between rare earth elements and major elements shows that rees in the oil shales and the coals are both of terrigenous origin and are mainly controlled by detrital minerals rather than by organic matter in both layers rees have no relationship with fine grained phosphates and during the weathering process the rees were not very mobile and were resistant to fractionation

short timescale thermohaline variability and residual circulation in the central segment of the coastal upwelling system of the ria de vigo northwest spain during four contrasting periods 1 sixteen hydrographic surveys were carried out in the middle segment of the ria de vigo northwest spain at 3 to 4 day intervals during february april july and september 2002 four surveys per period simultaneously an acoustic doppler current profiler adcp mooring recorded the velocity profile combination of direct current measurements with the output of an inverse model based on the time course of the distributions of salinity and temperature allowed an objective analysis of the effect of the meteorological forces on the hydrodynamics of the ria remote shelf winds explained more than 65 of the variability of the subtidal circulation which responded immediately to this forcing lag time 2 days shelf winds created a simple two layered circulation pattern with a surface outgoing current under northerly winds and a surface ingoing current under southerly winds a three layered circulation developed during the transitions from northerly to southerly winds and vice versa at the same time an empirical orthogonal function eof analysis demonstrated the lack of contribution of local winds to the subtidal dynamics of the ria continental runoff and heat exchange with the atmosphere explained less than 5 and 25 of the variability observed in the subtidal circulation of the ria de vigo

tidal exchange at the bay ocean boundary for bays and inlets with narrow entrances tidal exchange with the ocean is often characterized by an ebb flood asymmetry in which the ebb flow exits the bay as a jet while the flood flow is drawn in approximately as a radial sink a process often termed tidal pumping in this paper the importance of tidal pumping in controlling the exchange of water at the bay ocean boundary is examined based on observations at the mouth of san diego bay the observations are novel in combining the use of shipboard acoustic doppler current measurements with a unique bay water tracer technique to provide visualization of the exchange as well as exchange budgets visualization of the tidal evolution of flow and tracers suggests that in accordance with the classical tidal pumping model the horizontal dynamics at the mouth of san diego bay are governed by an asymmetry between the jet like nature of the ebb flow and the sink like nature of the flood flow this asymmetry results in strong tidal velocity and phase gradients similar to those observed in previous numerical modeling studies a one dimensional trajectory model based on the observations indicates that the combined influence of the residual circulation and offshore gradients in the tidal velocity and phase provides the mechanism by which water from the bay is exchanged with water from the ocean both bottom friction and thermal gradients affect the dynamics of the vertical exchange the resulting asymmetry in the offshore flow leads to a vertical mode of pumping similar to that observed in the horizontal view this horizontal and vertical pumping of the offshore flow is shown to produce a strong correlation between the sectionally averaged velocity and bay water concentration resulting in a significant net tidal exchange between the bay and ocean

the haslam formation a late santonian early campanian forearc basin deposit in the insular belt of southwestern british columbia and adjacent washington abstract the upper cretaceous santonian lower campanian haslam formation nanaimo group of southern vancouver island and the gulf islands of british columbia and the san juan islands of washington includes 1 inner submarine fan facies consisting of channel axis conglomerate and sandstone intercalated with channel margin and interchannel turbidites and 2 outer submarine fan and basin plain facies consisting of fan lobe and lobe fringe turbidites thin bedded turbidites and shales outer submarine fan facies are more common in the lower part of the formation and in the westernmost exposures on vancouver island whereas inner submarine fan facies characterize the upper part of the haslam in the san juan islands and are more common throughout the formation to the east and southeast these ubmarine fan facies were deposited in a forearc basin on rocks of the wrangellia exotic terrane seaward of the cretaceous magmatic arc in the coastal plutonic belt the haslam submarine fan complex prograded to the northwest or west into the forearc basin the sediment supplied to the fan was derived from terrane to the east and south where metasedimentary sedimentary metavolcanic and volcanic rocks were the dominant source areas during the late santonian and early campanian haslam sandstone and conglomerate records the first appearance of sediment from the east in the nanaimo basin older upper cretaceous santonian rocks of the nanaimo group the comox formation were derived in large part from upper paleozoic to lower mesozoic volcanic and metavolcanic rocks and jurassic plutonic rocks of the insular belt later nanaimo formations campanian maestrichtian that overlie the haslam were derived from low grade metamorphic and plutonic sources with only minor input of volcanic and sedimentary material thus three petrologic intervals can be recognized in the nanaimo group on southern vancouver island the gulf islands and the san juan islands the santonian interval comox formation characterized by sediment derived from the insular belt the late santonian early campanian interval haslam formation characterized by sediment derived from a sedimentary and subordinate volcanic source to the east and the campanian maestrichtian interval extension to gabriola formations derived from a low grade metamorphic and crystalline source to the east paleocurrent dispersal atterns are similar for the haslam and extension gabriola intervals which suggests that sediment supplied to the forearc basin was derived from uplifted subduction magmatic arc complexes that were probably related to the sourthern margin of the insular belt and were deformed when the magmatic arc shifted westward in the mid cretaceous the petrologic intervals are interpreted to reflect unroofing of this source terrane although other interpretations are possible if transcurrent faulting was active in this region in the late cretaceous

experimental investigation of thermal maturation on shale reservoir properties from hydrous pyrolysis of chang 7 shale ordos basin abstract thermal maturity has a significant impact on hydrocarbon generation and the storage capacity within shales but explicit and quantitative characterization of that impact on continental shales is scarce to better understand how thermal maturation affects the organic and inorganic changes of the continental shale reservoirs hydrous pyrolysis was performed to simulate the maturation process toc rock eval and adsorption isotherms tests were used to obtain various geochemical parameters of the shale solid residues the results indicate that with pyrolysis temperature increasing from ambient temperature to 550 c the vitrinite reflectance increases from 0 5 to 2 5 ro and the toc total organic carbon loss weight reaches 25 regarding porosity the fraction of micro to meso pores in the shale increases with an increase in the pyrolysis temperature whereas the macro pores do not change significantly the total amount of gas adsorption does not necessarily increase as the toc is consumed but the gas adsorption capacity per unit of toc increases with increasing thermal maturity our finding provides theoretical modelling for identifying shale gas development prospective zones according to thermal maturity mapping and for predicting quantitatively the geochemical and inorganic changes that occur with thermal evolution

the controls on the major and trace element evolution of shales siltstones and sandstones of ordovician to tertiary age in the wet mountains region colorado u s a a vertical section of shales siltstones and sandstones from ordovician to eocene age in a limited geographic area east of the wet mountains and sangre de cristo mountains in colorado have been analyzed for major elements and a variety of trace element concentrations including the ree in addition the petrography of the sandstones has been determined the quartz rich arenites contain considerably lower concentrations of most elements relative to coexisting shales or siltstones at the same outcrop the arkosic sandstones contain similar to lower concentrations of most elements compared to coexisting shales or siltstones in the same area accordingly the average concentrations of al2o3 fe2o3 mgo tio2 loi rb th co sc cr cs nb y and ree are significantly lower in all sandstones relative to all shales and siltstones the exceptions are sio2 na2o and ba concentrations and the eu eu lasc and thsc ratios as they are higher in the sandstones than the shales and siltstones there is no significant difference in the mno cao k2o and sr concentrations or the sollaco thco lani crth and lalucn ratios of the average sandstones relative to the shales and siltstones many of these differences may be related to the higher quartz and feldspar and lower clay mineral amounts in the sandstones than in the shales and siltstones for example average lasc thsc eueu and lalucn ratios of th arkosic sandstones tend to be higher than the coexisting shales and siltstones due to enrichment of the arkoses in feldspar relative to the other minerals e g eueu 0 82 0 19 in average arkoses in the trinidad vermejo raton poison canyon and cuchara formations eueu 0 63 0 19 in average shales and siltstones in the same formations in addition the elemental concentrations and ratios are more variable for most elements in the sandstones than the shales and siltstones this suggests that the shales are rapidly homogenized near the source the elemental fractionation in the arkosic sandstones due to enrichment of feldspar relative to other minerals suggests that they are poorer indicators of provenance that the associated shales whereas the more homogeneous elemental distributions in the shales and siltstones suggest that they may be better indicators of provenance than the sandstones nevertheless the elemental ratios that are most similar in the sandstones and in the shales and siltstones are consistent with their derivation from similar average intermediate to silicic source rocks

spatial variation in sediment fluxes redox conditions and productivity in the permian triassic panthalassic ocean abstract two permian triassic boundary sections in central japan provide a rare window into environmental conditions within the panthalassic ocean which encompassed more than half the earth s surface at 252 ma integration of petrographic geochemical and time series data provides new insights regarding the fluxes of major and trace components to the sediment as well as environmental conditions in both the deep and intermediate water masses at each study site the ubara section was located in a high productivity peri equatorial location whereas the gujo hachiman section was located in a moderate productivity location at some distance from the paleoequator an upward transition from gray organic poor cherts to black siliceous mudstones at both sites occurred in conjunction with increased primary productivity intensified euxinia within the oxygen minimum zone omz and decimation of the radiolarian zooplankton community euxinia in the omz of the equatorial panthalassic ocean developed episodically for a 200 250 kyr interval during the late permian followed by an abrupt intensification and lateral expansion of the omz around the permian triassic boundary throughout the study interval bottom waters at both sites remained mostly suboxic a finding that counters hypotheses of development of a superanoxic permo triassic deep ocean as a consequence of stagnation of oceanic overturning circulation

influence of water column anoxia on the burial and preservation of carbon and phosphorus in marine shales abstract organic p and organic c concentrations were measured in several well characterized phanerozoic marine shale sequences with the primary focus being the camp run member of the devonian mississippian new albany shale sequences were selected with close spatial association of bioturbated and laminated sediments which reflect deposition from oxic and anoxic waters respectively average organic c p mole ratios calculated from the data are 150 for bioturbated shales and 3900 for the laminated shales of the new albany differences in the extent and mechanisms of early diagenesis related to the oxygenation of waters at the sediment water interface can account for the c p ratios of buried organic matter low c p ratios of bioturbated sediments are attributed to 1 1 the increased ability of bacteria to store p in well oxygenated environments which leads to the production of low c p ratio bacterial biomass and 2 2 the extensive oxidation of sedimentary organic matter resulting in the formation of residual organic phases with low c p ratios high organic c p ratios of laminated sediments are explained by a combination of 1 1 the limited ability of bacteria to store p under anoxic conditions 2 2 extensive p regeneration from sedimentary organic matter 3 3 enhanced c preservation relative to the bioturbated shales it is also shown that relative to organic c laminated shales are not as effective a p sink as are bioturbated shales this provides a mechanism in anoxic environments for burying large quantities of organic matter without simultaneously sequestering the p needed to sustain further productivity

provenance and depositional environment of rhenohercynian synorogenic greywackes from the giessen nappe germany the giessen nappe of the south eastern rhenish massif can be subdivided into a northern group and southern group of frasnian lower carboniferous greywackes that differ slightly in their sedimentology clast petrography heavy mineral assemblages and bulk geochemistry

relationship between inferred redox potential of the depositional environment and geochemistry of the upper pennsylvanian missourian stark shale member of the dennis limestone wabaunsee county kansas u s a analyses of 21 samples collected from a core of the 52 8 cm thick stark shale member of the dennis limestone in wabaunsee county kansas demonstrate four cycles with two orders of magnitude variations in contents of cd mo p v and zn and order of magnitude variations in contents of organic carbon cr ni se and u the observed variability in amounts and or ratios of many metals and amounts and compositions of the organic matter appear related to the cause and degree of water column stratification and the resulting absence presence of dissolved o2 or h2s high cd mo u v zn and s contents a high degree of pyritization dop 0 75 0 88 and high high v v ni 0 84 0 89 indicate the presence of h2s in a strongly stratified water column intermediate contents of metals and s intermediate dop 0 67 0 75 and intermediate v v ni 054 0 82 indicate a less strongly stratified anoxic water column whereas low metal contents and low v v ni 0 46 0 60 indicate a weakly stratified dysoxic water column high p contents at the top of the organic matter rich intervals within the stark shale member indicate that phosphate precipitation was enhanced near the boundary between anoxic and dysoxic water compositions relatively abundant terrestrial organic matter in intervals deposited from the more strongly stratified h2s bearing water column indicates a combined halocline thermocline with the fresher near surface water the transport mode for the terrestrial organic matter the predominance of algal organic matter in intervals deposited from a less strongly stratified water column indicates the absence of the halocline and the presence of the more generally established thermocline relatively low amounts of degraded hydrogen poor organic matter characterize intervals deposited in a weakly stratified dysoxic water column the inferred variability in chemistry of the depositional environments may be related to climate variations and or minor changes in sea level during the general phase of deeper water deposition responsible for this widespread shale member

geochemical characteristics redox conditions and organic matter accumulation of marine oil shale from the changliang mountain area northern tibet china abstract the organic rich changliang mountain oil shale located in the north qiangtang depression northern tibet is considered to be excellent mineral resource in china the changliang mountain oil shale reported here was deposited in a tidal flat lagoon environment and is characterized by black thin layered oil shales intercalated with dark gray marls here we present geochemical data from the changliang mountain oil shale profile in order to investigate the mechanism of organic matter om accumulation and to establish the formation model for the marine oil shale deposition total organic carbon toc values range from 2 96 to 23 47 in the oil shale samples while the marl samples contains low toc contents ranging from 0 06 to 0 21 in the organic rich oil shale sediments many redox indicators including mo al ratios v cr ratios th u ratios ni co ratios and the relationship of mo to toc suggest a deposition under dysoxic to anoxic environments subsequently the bottom water evolved into an oxic water body when the organic poor marls were deposited however the negative and or weak relationship between toc and productivity indices p ti and ba al indicates that om accumulation was not controlled mainly by primary productivity but dysoxic anoxic bottom water environment a stratified water column may be initiated by the supply of fresh water from the continent nearby combining with warm and humid climate which is beneficial to the reproduction of marine organisms the death and bury of these organisms could lead to the formation of dysoxic anoxic bottom waters and enhance the preservation of om in this study a preservation model of the changliang mountain oil shale was established the model implies that excellent preservation is the major controlling factor for om enrichment in the oil shale layer in addition factors such as mixed deposition with clay minerals and detrital matter input cannot be ignored for their influence on om enrichment