geochemistry and provenance of the middle ordovician austin glen member normanskill formation and the taconian orogeny in new england the austin glen member of the upper middle ordovician normanskill formation is a sandstone shale ysch succession deposited in the foreland of the taconian orogen petrographic major and trace element and nd pb isotopic data provide substantial constraints on its provenance lack of k feldspar and paucity of plagioclase in addition to the dominance of sedimentary rock fragments indicate that the source was dominated by recycled sedimentary components major and trace element data support this conclusion and indicate that the provenance of both shales and sandstones was the same no evidence of an ophiolitic or volcanic component was observed interpretation of nd isotopic characteristics are complicated by a partial resetting of the nd isotope system at about the time of sedimentation but indicate that the provenance of the austin glen member had a long term history of light rare earth element lree enrichment average tdm 1a8 ga furthermore nd isotopic compositions are extremely homogeneous end 8a1 0a6 1 s d n 23 at 450 ma the approximate depositional age indicating either a single source or very well mixed sources 207pb 204pb ratios are variable but within the range of pb isotopic compositions typically described as grenvillian the range of 207pb 204pb is greater than expected for the range of 206pb 204pb and suggests an additional component of pb possibly introduced during diagenesis the immediate source of the austin glen member may have been the accretionary prism that developed as older sediments of the laurentian margin were scraped off the basin oor incorporated within the accretionary prism and shed into the basin no evidence indicating the arrival of an undifferentiated island arc or continental fragment during the taconian orogeny has been found the data acquired during this study can be explained almost exclusively by grenville province source components but with possible additional contributions from older laurentian terranes and late proterozoic rift volcanics that are not readily quanti ed but likely to have been minor accordingly we conclude that the taconian orogeny in new england involved either 1 a continental arc that involved exclusively laurentia 2 collision of a continental block with identical geochemical characteristics as laurentia or 3 essentially no detritus from any exotic colliding block island arc or continental fragment reached the foreland basin at the time of austin glen deposition

residence of ree y th and u in granites and crustal protoliths implications for the chemistry of crustal melts a systematic study with laser ablation icp ms scanning electron microscopy and electron microprobe revealed that 70 95 wt of ree except eu y th and u in granite rocks and crustal protoliths reside within reeythu rich accessories whose nature composition and associations change with the rock aluminosity the accessory assemblage of peraluminous granites migmatites and high grade rocks is composed of monazite xenotime in low ca varieties apatite zircon thorthosilicate uraninite and betafite pyrochlore metaluminous granites have allanite sphene apatite zircon monazite and thorthosilicaie peralkaline granites have aeschinite fergusonite samarskite bastnaesite fluocerite allanite sphene zircon monazite xenotime and th orthosilicate granulite grade garnets are enriched in nd and sm by no less than one order of magnitude with respect to amphibolite grade garnets granulitegrade feldspars are also enriched in lree with respect to amphibolite grade feldspars accessories cause non henrian behaviour of ree y th and u during melt solid partitioning because elevated fractions of monazite xenotime and zircon in common migmatites are included within major minerals their behaviour during anatexis is controlled by that of their host settling curves calculated for a convecting magma show that accessories are too small to settle appreciably being separated from the melt as inclusions within larger minerals biotite has the greatest tendency to include accessories thereby indirectly controlling the geochemistry of ree y th and u we conclude that ree y th and u are unsuitable for petrogenetical modelling of granitoids through equilibrium based trace element fractionation equations

analytical techniques for the separation and sem identification of heavy minerals in mudrocks heavy mineral investigations must be preceded by effective heavy mineral separation identification and determination of mineral compositions provenance determinations by heavy mineral variations and direct measurement of the control of trace elements by heavy minerals in mudrocks has not been possible because of the difficulties in separating heavy minerals from the obscuring mass of the clay matrix the technique to separate identify and determine the variability of heavy minerals in mudrocks presented here is nondestructive and works well with mudrocks of variable induration and maturation from mudstones to shales this methodology uses lithium metatungstate for heavy liquid separations of bulk samples and a combination of optical and scanning electron microscopy sem for identification and quantification of heavy mineral proportions

tectonically buried continent ocean boundary ouachita mountains arkansas a seismic reflection sequence observed at depth beneath the south flank of the benton uplift in arkansas is interpreted to mark the early paleozoic continent ocean boundary the sequence is similar in both external and internal geometry to wedge shaped features commonly observed in the narrow zone separating continental from oceanic basement on modern passive margins and interpreted as layered volcanic sequences it is suggested that slope and rise sediments now exposed in the benton uplift were thrust in a thin skinned fashion over the edge of the north american continent during initial stages of the carboniferous ouachita orogeny but that later uplift and slight northward translation of the continental margin basement occurred in a more thick skinned fashion preserving the boundary wedge intact beneath the earlier thrust sheets

relationships among vitrinite reflectance illite crystallinity and organic geochemistry in carboniferous strata ouachita mountains oklahoma and arkansas the ouachita mountains contain a thick section of carboniferous strata that display an extreme range in thermal maturity as determined by vitrinite reflectance clay mineralogy illite crystallinity and organic geochemistry of shales from those strata are systematically related to thermal maturity shales of the stanley jackfork and atoka formations are predominantly composed of illite and chlorite with minor occurrences of mixed layer clays restricted to samples characterized by mean vitrinite reflectance less than 1 5 and pyrophyllite restricted to samples characterized by mean vitrinite reflectance greater than 2 7 illite crystallinity is significantly related to vitrinite reflectance ro weaver s illite sharpness ratio sr increases with increasing ro log sr 0 28 0 08 ro whereas kubler s illite crystallinity index ci decreases with increasing ro log ci 1 01 0 07 ro plots of bitumen ratio bitumen total organic carbon vs vitrinite reflectance weaver s illite sharpness ratio and kubler s crystallinity index all reveal hydrocarbon generation preservation curves that define submature mature and supermature zones with regard to a liquid hydrocarbon window these results suggest that in the absence of vitrinite illite crystallinity can be used quantitatively to estimate levels of thermal maturity and cautiously to approximate hydrocarbon generation preservation stages of potential source rocks

mudstone petrology of the mesoproterozoic unkar group grand canyon u s a provenance weathering and sediment transport on intracratonic rodinia abstract the synthesis of mudstone petrology and interbedded sandstone detrital zircon geochronology provides insights into the provenance weathering regime hydrodynamic effects and diagenesis of the mesoproterozoic unkar group unkar mudstones were derived largely from the grenville orogen go of southwest texas and the adjacent yavapai mazatzal ym and southern granite rhyolite sgr terranes detrital zircon data indicate distinct pulses of go derived sediment during hakatai and dox formation deposition whereas shinumo sediment contains a larger component of ym and sgr material an increase in plagioclase and biotite abundances in the dox further suggest an orogenic pulse bulk chemistry including elevated cr and ni abundances and ree systematics implicate a heterogeneous provenance for unkar sediment best approximated by a mix of granite or granodiorite with some basalt weathering of unkar sediment as determined from mudstone and crystalline source bulk chemical trends is characterized as moderate cia values between 55 and 70 indicative of a temperate climate in an orogenic setting small less than 10 wt amounts of detrital kaolinite and chlorite are consistent with a moderate temperate weathering regime illite the dominant clay mineral in the unkar group is largely the 2m1 polytype and detrital in origin however it is estimated that 7 of the k in the escalante creek member results from k metasomatism and may form up to 15 wt authigenic 1m or 1md illite the clay size fraction and zircon are the chief contributors to the ree budget in unkar mudstones lithostratigraphic variations in the hree distributions can be attributed partially to variable zircon abundance in the silt size fraction a likely function of hydrodynamic sorting age constraints on the duration of unkar group sedimentation range from 30 to 100 my for the 1100 m conformable shinumo dox succession and result in compacted sedimentation rates of between 1 0 and 3 6 cm 103 yr these rates are comparable to mesozoic foreland basin settings

landform classification and soil distribution in hummocky terrain saskatchewan canada this study presents a classification of distinct three dimensional landform elements and examines the relationship between these landform elements and selected soil morphological properties of udic boroll soils in southern saskatchewan canada the classification is based on defined ranges of three criteria derived from topographic data gradient profile downslope curvature and plan across slope curvature seven landform elements are recognized convergent shoulders divergent shoulders convergent backslopes divergent backslopes convergent footslopes divergent footslopes and level elements all of the elements are easily identified in the field the thicknesses of a horizons and depths to calcium carbonate of the soils were consistently greater in convergent versus divergent elements in the same profile group e g shoulders and showed an overall increase in the sequence shoulders backslopes level footslope elements distinct groups of elements emerge from a statistical analysis of the differences between individual and bivariate means of soil morphological properties associated with each landform element the differences in soil properties among the elements can be largely explained by differences in water movement and distribution in hillslope systems the results of the study highlight the need to consider land surface morphology during the development of research designs for soil related studies

loss of provenance information through subsurface diagenesis in plio pleistocene sandstones northern gulf of mexico abstract subsurface alteration of plagioclase potassium feldspar and a variety of nonopaque heavy minerals has substantially modified the detrital composition of plio pleistocene sediments in the northern gulf of mexico albitization of plagioclase and dissolution of unstable grains are the two principal mechanisms of grain alteration grain alteration increases progressively with depth and has taken place without the influence of significant amounts of meteoric fluids the degree to which strictly subsurface grain alteration has affected these young sediments suggests that grain assemblages in older rocks should be viewed most skeptically with regard to their state of preservation

alterations in the non clay mineral fraction of pelitic rocks across the diagenetic to low grade metamorphic transition ouachita mountains oklahoma and arkansas abstract the transformation of smectite to illite has been cited by many authors as a source of silica during diagenesis of mudrocks illites themselves however undergo chemical changes as they recrystallize into micas during high grade diagenesis low grade metamorphism average compositions of phyllosilicates from the literature suggest that an equivalent amount of silica is available from transformation of illite to muscovite as from illitization of smectites the fate of silica released by this process has not been reported but could be a major contributor to the silt size quartz population the quartz and feldspar fraction of pelites from the stanley shale mississippian in the ouachita mountains of oklahoma and arkansas was separated using sodium bisulfate fusions the mineralogy and the grainsize distribution of this fraction were determined using standard petrographic and x ray diffraction xrd techniques bulk rock samples were analyzed using x ray fluorescence xrf and instrumental neutron activation analysis inaa methods the data obtained were related to illite crystallinity and vitrinite reflectance as reported by guthrie et al 1986 and houseknecht and matthews 1985 both the percentage of quartz and the mean grain size of the quartz and feldspar fraction increase with greater illite crystallinity values the growth in quartz is especially apparent in the finest size fractions a corresponding decrease in the silica content of the clay mineral fraction is also observed development of quartz polycrystallinity occurs across the same interval whole rock chemical abundances show no statistical correlation with thermal maturity relative to titanium both the major element and the trace element concentrations show little variation rare earth element ratios do not correlate with thermal maturity and remain essentially constant our results are consistent with reported differences between quartz in schists and their shale precursors and suggest that release of silica during diagenesis of phyllosilicates continues after the smectite illite transformation this silica precipitates as quartz within the pelite consistent with the suggestion by blatt 1987 that metapelites are the source of abundant silt size quartz the lack of whole rock chemical variation with thermal maturity implies closed system behavior across much of the pelite to metapelite transition

vent activity in a subduction area nankai wedge the foraminiferal test records we have collected 41 sediment samples from the depths of about 2000 m and 4000 m in the nankai trough area using the submersiblenautile study of these samples has enabled recognition of two main preservation states of planktonic and benthic foraminiferal tests dissolution in all the samples and superimposed encrustation in some of them the distributional pattern of planktonic foraminifera reveals a strong rate of dissolution of the tests among the benthic foraminifers the aragonitic specieshoeglundina elegans shows below 2000 m a corrosion of test surfaces removing parts of growth layers and breakage of last chambers on the basis of pore water chemistry the high rates of dissolution are related to unusual aragonite undersaturation in pore water at the sediment water interface and to expulsion of pore water in open sea water furthermore a peculiar etching of the whole test ofh elegans and encrusted calcitic tests are observed but only in the samples collected near fluid venting manifestations clams worms and shell concretions suggesting a possible relationship between diagenesis and fluids

sandstone provenance of north western sectors of the intracontinental cenozoic qaidam basin western china tectonic vs climatic control abstract sandstone samples from all cenozoic formations of the nonmarine internally drained qaidam basin have been collected for provenance analysis to monitor possible changes in sandstone composition driven either by tectonics or climate provided an appropriate hinterland biotite contents may be a reasonable indicator for aridity moderately sorted sandstones with subangular to subrounded grains from the northwestern part of the qaidam basin are immature indicated by a high proportion of feldspars and lithic fragments nevertheless they have relatively high quartz contents of 29 65 averaging between 40 and 45 the average framework compositions of the formations show only a slight variation over time limited to the oldest and youngest cenozoic formations contents of white mica and biotite are significantly higher in upper portions of the section white mica contents increases from 1 0 to 3 7 and biotite from 0 1 to 1 6 respectively this change can be explained by increasing aridity during neogene and surface uplift of altyn mountains and qimantagh which led to higher relief when plotted on basic variation diagrams total quartz feldspar lithic fragments there is a slight shift from continental block field to orogenic field which might reflect the motion of the altyn tagh fault since oligocene times although climate changed during the cenozoic from arid over semiarid back to arid we could not find any distinct changes in the framework mineral compositions over time that could be related to climatic events few selected mudstones from eocene to lower miocene formations have been geochemically analysed by icp ms all samples display uniform high enrichment in light rees in chondrite normalized diagrams with one exception the ree concentrations are decreasing in a stepwise manner although insignificantly from formation to formation with time due to a diluting effect by carbonate

planktonic foraminifera of the northern indian ocean distribution and preservation in surface sediments in the northern indian ocean planktonic foraminiferal tests accumulate in a wide variety of surface water environments and depositional settings this variability enables us to isolate the effects that surface water ecology and differential dissolution have on the distribution of planktonic foraminifera from 251 geographically widespread surface sediment samples foraminiferal abundance varies from 0 to 104 whole foraminifera in the greater than 150 m fraction per gram dry sediment values 10 characterize the three deep basins of the equatorial indian ocean and the western bay of bengal foraminiferal tests are most abundant on carbonate covered ninety east and carlsberg ridges absolute abundance patterns are mainly controlled by non ecological processes variations in dissolution resistant species rsp with water depth reveal that the foraminiferal lysocline fl varies regionally the fl is deepest 3 800 m in the equatorial region rises abruptly to 3 300 m in the arabian sea and varies from 2 600 m to near 2 000 m moving northward in the bay of bengal deep samples with anomalously low rsp 30 suggest redeposition systematic geographic and depth related variation is observed for the 17 most abundant foraminiferal species dissolution resistant species g menardii g tumida g dutertrei p obliquiloculata generally exhibit a rapid and continuous increase in relative abundance at and below the fl susceptible species g ruber g bulloides g glutinata for example exhibit a rapid and continuous decrease in relative abundance at and below the fl moderately susceptible species g conglobatus g aequilateralis g conglomerata for example rapidly increase in abundance at the fl and systematically decrease with depth below the fl principal components analysis pca of faunal data from minimally dissolved 30 rsp samples reveals important ecologically related species intercorrelations the major biogeographic gradient is the negative covarying relationship between ag bulloides g glutinata species pair and a grouping ofg sacculifer g conglobatus g aequilateralis andg ruber pca of all samples demonstrates how differential dissolution alters this and other species relationships species groupings that incorporateg ruber g menardii andg dutertrei are particularly affected by dissolution comparison of average faunal data from minimally dissolved samples in the northern indian ocean with similar samples from other tropical regions suggests varying environmental factors produce distinct faunas within the tropical ocean for example g bulloides g falconensis andg hexagona are significantly more abundant in northern indian ocean surface sediments while such species asg ruber g sacculifer g dutertrei andp obliquiloculata dominate in other tropical regions

ree distribution in the clay fraction of pelites from the southern apennines italy abstract in order to evaluate whether clay minerals or accessory phases control the ree pattern of the only illite is correlated with ree while a smectite rich sample is characterized by the lowest content in ree strong correlations exist between ree and tio2 nb zr and a less significant one with sr no correlations exist between these elements and y r mode factor analysis indicated that three factors account for 87 of the total variance the first factor var 43 2 seems to express mainly the tendency of some resistate minerals to concentrate ree in the fine fraction the second factor var 30 0 may be related to the effect of circulating fluids responsible for dickite genesis the third factor may be linked to the weathering of micaceous phases the ree do not have a significant weight in the second and third factors resistate minerals appear dominant in controlling at least the lree and nb it is proposed that in the studied samples illite likely conveyed ree via the included minerals

trace elements in shale as indicators of crustal provenance and terrane accretion in the southern canadian cordillera in this study the trace element geochemistry of shale is used to infer the nature of adjacent crustal blocks during terrane amalgamation and accretion in southern british columbia the geochemistry of about fifty shale samples from one of the best dated stratigraphic sections in the north america cordillera is used to 1 infer proximity to source regions characterized by juvenile ocean arcs continental arcs and ophiolites and 2 address a controversy concerning the timing of terrane amalgamation and accretion this study includes analyses of shale from the entire mesozoic stratigraphic section of the cadwallader terrane and overlying tyaughton basin as well as argillites from the structurally adjacent bridge river complex the mid cretaceous albian strata of the upper taylor creek group show light rare earth lree enrichment la n sm n of 3 0 and anomalously high cr and ni older units upper triassic lower cretaceous that stratigraphically underlie the upper taylor creek group have less lree enrichment high ba n la n ratios and no cr or ni anomaly the mid cretaceous strata were probably derived from a continental arc during a period of uplift and erosion of ultramafic rocks probably ophiolites and the co extensive nature of these sediments suggests accretion of many basement terranes to the edge of a continent the trace element geochemistry of the older strata is similar to that of sediment derived from an oceanic arc however lower cretaceous strata of the relay mountain group may record the incipient collision and progressive closure of this ocean basin the bridge river complex which is dominated by oceanic rocks and is interpreted to be an accretionary complex contains two suites of argillites one of which shows significant lree enrichment and isotopic data suggest a jurassic cretaceous age for these argillites that compose the matrix in this complex leitch et al 1991 we suggest that the bridge river complex was a jurassic cretaceous accretionary complex that formed outboard of the methow section of rocks and was not juxtaposed with the cadwallader terrane and tyaughton basin until the albian when these terranes were accreted to north america paleomagnetic data from these rocks maxson et al 1993 indicate that accretion took place at the latitude of central mexico and that subsequent strike slip faulting brought these terranes to their present position by eocene time

testing provenance diagrams lessons from the well constrained cariaco basin abstract the fine grained sediments of the cariaco basin venezuela of the last 130 ky whose deposition history is well characterized were analyzed geochemically in order to test the validity of sediment bulk geochemistry as an indicator of detrital provenance several binary and ternary diagrams as well as the chemical index of alteration cia were tested for their capacity to discriminate the poorly contrasted detrital sources to the cariaco basin and to describe the temporal evolution of the contributions of these different sources most of the diagrams tested did not allow a good discrimination of sources or when sources were well discriminated did not allow an interpretation of the temporal variations consistent with the known history a relatively good discrimination of sources and a consistent interpretation of temporal variations were however obtained using hf vs th and la yb vs gd yb binary diagrams as well as ti zr th ti zr la and lu hf th ternary diagrams compared to the previous studies of the detrital content of the cariaco basin sediments the geochemical approach permitted the recognition of a sediment contribution eroded from the unare platform and gulf of cariaco during rapid sea level oscillations and the contribution of saharan eolian particles during the younger dryas preboreal and mis6 5 transition the choice of plotted elements was determined after considering carrier minerals so that different elements may be informative in different sedimentary contexts overall mineral sorting during transport appears as a major limit to quantitative estimation of the different contributions in particular mineral sorting leads to the selective enrichment of elements associated with clays al rb th and lree in sediments deposited in the basin unless the geochemical effect of mineral sorting can be measured it appears that quantitative provenance analysis should be performed on fractions of similar grain size instead of bulk sediment

diagenetic modification of sm nd model ages in tertiary sandstones and shales texas gulf coast sm nd model ages of sandstones and shales from the oligocene frio formation of south texas and the paleocene eocene wilcox group of south central texas increase with increasing depth of burial depleted mantle model ages tdm of frio shales increase from ca 800 ma at 1 km of burial to ca 1000 ma at 4km in frio sandstones tdm increases from ca 750 ma at 1 km to over 1200 ma at 4 km of burial in wilcox shales tdm increases from ca 1300 ma to ca 1500 ma over a burial depth of 1 5 to 4 5 km tdm of wilcox sandstones increases from ca 1450 ma at 2 5 km of burial to as much as ca 2000 ma at 4 0 km the sampling scheme employed minimizes but does not eliminate the possibility that these trends in tdm are due to detrital variability close correlation of these trends with diagenetic changes in the rock and evidence of rare earth element mobility preserved in the diagenetic products suggests that diagenesis has modified tdm diagenetic modification of tdm in frio sandstone and wilcox shale is due primarily to loss of radiogenic nd whereas increased 147sm 144nd produces elevated tdm in deeper wilcox sandstones the tdm of frio shales does not change appreciably with depth owing to the opposite effects on tdm of decreased 147sm 144nd and decreased nd 0 loss of radiogenic nd is due primarily to reactions involving unstable volcanic detritus which is more abundant in the frio than in the wilcox decreased 147sm 144nd in authigenic illite and consequent increased 147sm 144nd in pore fluids results in elevated tdm in wilcox and frio sandstones containing late diagenetic cement and in decreased 147sm 144nd in deeper frio shale the similar tdm trends observed in both units which have different detrital characteristics suggest that modification of sm nd model ages in siliciclastic rocks may be commonplace during burial diagenesis

burial diagenesis of argillaceous sediment south texas gulf of mexico sedimentary basin a reexamination cuttings from a well through a thick section of miocene oligocene mudrocks from kenedy county texas spanning a depth range of 2130 to 5490 m 7000 to 18 000 ft have been studied petrographically and geochemically on the basis of whole rock chemical analyses the deepest samples have lost 18 wt and approximately vol mostly as caco3 mineral bound h2o and sio2 but including additional ca as well as sr light rare earth elements ree la ce nd sm fe and li k2o and rb have been added to the deeper rocks the large chemical changes are accompanied mineralogically by loss of detrital calcite kaolinite k feldspar ca plagioclase and muscovite gain of chlorite and albite and continued reaction of smectitic illite smectite i s to more illitic and k rich compositions throughout the entire depth interval of the well the large chemical changes in this thick mud rich interval almost certainly require advection of water free convection to accomplish the mass transfer initial variation in sediment composition is ruled out as a cause of the observed compositional changes with increasing depth because 1 a variety of immobile elements al2o3 tio2 zr hf heavy ree er yb th and sc remain constant relative to each other despite their uneven distribution across various particle size fractions in the sediments 2 deep frio shales are unlike quaternary gulf of mexico sediments or average shales and 3 unreasonable primary mineralogic compositions would be necessary to explain the chemical composition of the deep samples these results indicate that burial diagenesis of argillaceous sediment can be a considerably more open chemical process than is conventionally assumed that it can account for the two major chemical cements calcite and quartz in associated sandstones and that it mirrors secular changes in shales throughout geologic time

effects of chemical weathering and sorting on the petrogenesis of siliciclastic sediments with implications for provenance studies the bulk chemical compositions mineralogy and mineral proportions of sands and muds of the mallacoota basin in southeastern australia reflect the composition of weathering profiles mantling source rocks rather than bedrock muds contain abundant clay minerals that are virtually absent from the source rocks but abundant in the weathering profiles sands are strongly enriched in quartz relative to source rocks even in the headwaters of the fluvial system demonstrating that feldspar destruction occurs by in situ chemical weathering within profiles and before detritus enters the fluvial system k feldspar is proportionally more abundant in fluvial sands than in source rocks because plagioclase is more rapidly destroyed than either quartz or k feldspar in weathering profiles subsequent erosion and sorting produce sands enriched in quartz with high k feldspar plagioclase ratios relative to source rocks the composition of plagioclase incorporated into the fluvial sands is also controlled by chemical weat

an integrated chemo and sequence stratigraphic framework of the early pennsylvanian deepwater outcrops near kirby arkansas usa and its implications on remnant basin tectonics abstract the jackfork group in arkansas u s a is a major training ground for academics students and petroleum industry geoscientists interested in deep water exploration and development several superb outcrop sections are exposed and over the years numerous papers have been published on these rocks the kirby sections in western arkansas provide a unique opportunity to build a complete and continuous sequence stratigraphic framework for early pennsylvanian time in the ancient ouachita basin there are 25 outcrops including 12 roadcuts on highway 27 and 13 measured sections in the baumgartner quarry all the measurements and interpretations on the outcrops were integrated with previous work using modern concepts of deepwater turbidite geology including 1 regional tectonic and sequence stratigraphic framework of the stanley group jackfork group and johns valley shale in the ouachita basin 2 deepwater outcrop characterization and correlation from the degray lake section dierks section and big rock quarry which are on the trend of the depositional fairway 3 chemostrata data from key shale layers which are considered as potential correlative condensed sections twenty five key shale samples from kirby degray and dierks sections have been tested using inductively coupled plasma and mass spectrometry icp ms tests an additional 525 samples were later collected for handheld x ray fluorescence xrf tests for both major and trace elements results of sequence and chemostrata analysis indicate that the entire kirby sections consist of at least three 3rd order sequences from the bottom of the jackfork group to the middle of the johns valley group and over ten 4th order sequences caused by a combined effect of tectonic uplift eustatic sea level change mixed sediment provenance and shifting of depositional fairways when the ouachita basin was transitioning from a passive margin to a remnant marine basin rare earth and trace element results are compared with known tectonic data to further pinpoint the tectonic environment of the ouachita basin during early pennsylvanian time which is dominantly a continental arc setting

constraints on the accumulation of organic matter in upper ordovician lower silurian black shales from the lower yangtze region south china abstract the late ordovician to early silurian o s was an important period in which many significant geological events occurred during the o s transition organic rich black shales were widely deposited and became important unconventional energy sources paleoproductivity detrital input and redox conditions are the three major factors controlling organic matter om accumulation although the effect of each factor is relatively clear the complex influences of these factors remain poorly understood specifically the evolution of these factors and the corresponding influence on the accumulation of om during the o s transition has not yet been systematically investigated this paper investigates the constraints on om accumulation in o s transition black shales from the lower yangtze region based on graptolite fossil identification zircon u pb dating and geochemical analyses of a well sequenced drilling profile the results show that i the sy 1 core sequence was well constrained from graptolite zones wf2 447 62 ma to lm5 441 57 ma across the o s boundary with decreasing sedimentation rates srs in the upper katian wf2 to wf3 and increasing srs in the lower rhuddanian ii complementary volcanic inputs katian and rhuddanian and upwelling events hirnantian exerted strong control over paleoproductivity iii orogenic processes in south china controlled detrital inputs and redox conditions iv om accumulation in the lower yangtze area across the o s transition occurred in three stages in stage 1 wf2 wf3 strong volcanism boosted productivity whereas om preservation was not favored in the oxic environment in stage 2 wf4 lm3 upwelling and volcanism resulted in high productivity and provided the optimal configurations for om enrichment in stage 3 lm4 and later rare om was preserved due to terrestrial dilution and unfavorable preservation conditions eventually wf4 lm3 became the prominent om rich biozones due to the effective coordination of the controlling factors namely upwelling volcanism and redox conditions

detrital chromian spinel compositions used to reconstruct the tectonic setting of provenance implications for orogeny in the canadian cordillera abstract detrital chromian spinel is an important accessory mineral in chert and volcanic lithic sandstones from the northern bowser basin microprobe analyses show that bowser basin detrital chromian spinels have cr cr al between 0 21 and 0 89 mg mg fe2 between 0 24 and 0 70 and fe3 fe3 al cr values below 0 12 comparison with spinels from literature on ultramafic rocks indicates that the compositional range of the detrital spinels closely matches that of spinels from alpine type peridotites emplaced by obduction of marginal basin crust and island arc complexes furthermore bowser basin spinels are compositionally distinct from spinels derived from either mid ocean ridge stratiform ultramafic complex or alaskan type peridotite the composition of the detrital spinel demonstrates that the source for bowser basin sediments included extensive alpine type peridotite which probably originated as marginal sea lithosphere in addition there is no evidence for material derived from mid ocean ridge alaskan type peridotites or stratiform complexes this provenance interpretation is in agreement with earlier interpretations that related chert pebbles in the bowser basin to chert rich strata of the cache creek terrane and is consistent with the detrital modal analysis of sandstones which calls for a source terrane consisting of obducted oceanic crust and island arc the chemistry of the detrital spinels further suggests the source area was eroded prior to emplacement of alaskan type peridotites or any regional gree schist or higher grade metamorphic events thus microprobe compositional analysis of detrital spinels adds important detail to the provenance interpretation that is not available through analysis of detrital modes alone the inference that marginal basin lithosphere rather than material derived from mid ocean ridges was the sediment source suggests that the obducted source terranes were closely associated with north america

a petrographic approach for evaluating trace element mobility in a black shale abstract at the time of deposition black shales record geochemical information related to the provenance and conditions of deposition for that rock these initial geochemical conditions are susceptible to alteration and overprinting by the aggressive processes of black shale diagenesis in this study we evaluate a sequence of ordovician black shales from the southern welsh basin for the presence of such a diagenetic overprint through use of cathodoluminescence backscattered electron imaging reflected light microscopy fission tracks and microprobe elemental mapping we can discern textural relationships with in the welsh black shales the relationships observed constrain a paragenetic sequence and overall diagenetic history including the early diagenetic formation of pyrite apatite rare earth element ree rich and carbonate and later formation of diagenetic monazite ree u rich and late stage carbonate the chemical reactions necessary to produce this mineral sequence require postdepositional redistribution of ree including changing cerium anomalies ce ce and uranium as a result ree u and their associated isotopic systems sm nd and u pb can reflect a diagenetic overprint rather than the source area and depositional conditions the paragenetic sequence described in this study records several postdepositional changes in the whole rock mineralogy among these changes are the formation of ree rich apatite and ree and u rich monazite the formation of these phases requires that ree and u are being redistributed on at least a mineral scale and that the initial depositional and provenance information recorded by the whole rock has been disturbed therefore the approach used in this study to carefully characterize the paragenetic sequence from the llandeilo caradoc black shales should be considered necessary in order to fully evaluate the usefulness of trace element proxies susceptible to diagenetic redistribution

geochemical identification of clastic sediment provenance from known sources of similar geology the cretaceous scotian basin canada abstract this study tests the effectiveness of a geochemical approach in identifying provenance in a basin where different sources do not show strongly contrasting geology petrological studies indicate that at least three distinct rivers draining reactivated horsts of the appalachian orogen supplied sediment to the lower cretaceous deltaic sandstones and mudrocks in the offshore scotian basin ninety five samples mostly from conventional core were analyzed for 44 major and trace elements the data were first screened for variability unrelated to provenance including changes in elemental abundance due to weathering and diagenesis and the effects of grain size and sorting on element variation the effect of hydraulic sorting was distinguished from the effects of concentration of ultrastable heavy minerals from polycyclic sources multivariate statistical analysis by principal component analysis pca was used to test the hypothesis of three discrete sources suggested by the petrologic model major element pca on sandstones discriminated the sources but results from trace element pca required further investigation using element biplots to understand their significance only a few elements were found to be diagnostic of different sources namely k rb sr u th nb and ti with the latter two of value only for sandstones all of these are elements that are abundant in the granites of the appalachians most published geochemical discrimination diagrams did a poor job of distinguishing the three petrographically recognized sources in other basins with quite different hinterland geology other elements are known to be of value in discriminating provenance thus it is unlikely that a globally applicable set of elemental discriminants can identify terrigenous sediment sources rather systematic investigation is needed that evaluates processes such as diagenesis and sorting and then tests geographic and stratigraphic variability in bulk geochemistry informed by at least semiquantitative petrographic data

late ordovician early silurian continental collisional orogeny in southern mexico and its bearing on gondwana laurentia connections new zircon and monazite u pb data tectonic mapping and petrologic studies in key units of the acatlan complex show a previously undocumented phase of continental collision orogeny of late ordovician early silurian age in southern mexico the event involved the partial eclogitization of oceanic lithosphere and continental crust which traveled westward more than 200 km over siliciclastic metasedimentary rocks of the trench forearc of an opposing continental margin the overriding eastern margin was the oaxaquia microplate attached to gondwana and the western overridden margin is considered to have been the eastern margin of laurentia this event which we name the acatecan orogeny was roughly synchronous with the possible closure of iapetus along the appalachian margin which involved according to current models either the docking of peri gondwanan terranes such as avalonia and carolina or the direct collision between gondwana and laurentia the permanence of oaxaquia in northwestern gondwana until the end of the silurian as suggested by tremadocian to silurian marine faunas in the cover of oaxaquia is more consistent with the direct collision of gondwana and laurentia at the end of the ordovician forming the acatlan complex between

tertiary volcanic rocks and the potassium content of gulf coast shales the smoking gun the majority of tertiary volcanic rocks of the western united states and mexico are alkaline in composition and may contain as much as 50 wt equivalent k feldspar emplacement of these volcanic strata is coeval with tertiary shale deposition in the texas gulf coast and they previously have been identified as likely sources of sediment for gulf coast shales evaluation of chemical trends in gulf coast shales particularly k 2 o indicates changes in sediment composition in the lower eocene oligocene and near the oligocene miocene boundary in particular there is a 250 increase in k 2 o content from 2 wt to 5 wt from the late eocene to the early oligocene gulf coast shale bulk rock compositions are consistent with a tertiary volcanic source estimates of erosion and mass balance calculations suggest that in the south texas gulf coast the oligocene frio formation may contain between 60 and 85 volcanic detritus and coeval frio shales to the north contain 25 vertical and lateral compositional variations highlight variable abundances of source detritus and the effects of weathering and depositional processes on gulf coast shale composition trends of increasing k 2 o content with depth in gulf coast shales previously have been interpreted to result from open system diagenesis and k metasomatism at depth the data presented herein suggest instead that these trends result from variable provenance and the influx of large volumes of tertiary alkaline volcanic material therefore diagenetic models that invoke a homogeneous initial shale composition and open system behavior may be invalid

beyond whole rock geochemistry of shales the importance of assessing mineralogic controls for revealing tectonic discriminants of multiple sediment sources for the ouachita mountain flysch deposits the origin of the ouachita mountains has been the focus of significant debate for decades considerable confusion also exists concerning the provenance of the carboniferous flysch of the ouachitas trace element geochemistry of shales from the stanley group delineates the provenance of the sediments and provides clues to the plate tectonic evolution of the southern continental margin during mississippian time th sc and cr th ratios indicate a cratonic source for the majority of the stanley group sedimentary rocks however in several samples low th sc ratios and high cr th ratios suggest a contribution from a mafic source using element ratio diagrams all of the samples plot along a curve consistent with a two component mixing model consisting of a dominant felsic and a subordinate mafic source the heavy mineral fraction of these shales sequester many of the trace elements used in whole rock studies monazite is ubiquitous in trace amounts and is the probable site for much of the rare earth elements in the whole rock the occurrence of monazite almost exclusively in sialic igneous rocks implies that sm nd isotopic signatures are not sensitive to sediment input from more mafic sources in some stanley shale samples chromite and mn oxides were identified and positively identify an oceanic crustal component as a source of stanley group sediment the results of this study emphasize the importance of determining the mineralogic sites of trace elements and realization of specific mineralogic contributions from mafic or sialic tectonic provenances

nd isotopic constraints on sediment sources of the ouachita marathon fold belt nd isotopes for the overthrust deep marine ouachita marathon sedimentary assemblage of arkansas oklahoma and west texas and associated paleozoic shelf and foreland deposits resolve into three distinct populations 1 lower to middle ordovician nd 13 to 16 average t dm 2 0 ga 2 upper ordovician to pennsylvanian nd 6 to 10 average t dm 1 6 ga and 3 mississippian tuffs nd 1 to 3 average t dm 1 1 ga a rapid shift in nd from 15 passive margin shales to 7 orogenic turbidites in the ouachita assemblage at ca 450 ma implies termination of craton dominated sources and the emergence of the appalachian orogen as the primary source of sediment for sea floor lying south of north america this connection is reinforced by nd isotopes in ordovician silurian turbidites from both the ouachita assemblage and the southern appalachian sevier martinsburg taconic foredeep which are identical nd 7 to 9 the post 450 ma ouachita assemblage falls along a single nd isotopic trend that significantly is not deflected by onset of carboniferous flysch nd 7 to 10 sedimentation nor by associated regional volcanism the less negative nd 2 of mississippian ash flow tuffs that erupted from arc s to the south probably resulted from isotopic mixing of old precambrian crust with young mantle derived components within a continental margin arc there is little isotopic trace element or petrographic evidence for any significant volcaniclastic detritus in the carboniferous turbidites indicating that volcanic arc sources were minimal nd isotopes in fluvio deltaic strata of the ouachita appalachian foreland and continental interior that is arkoma illinois and black warrior basins nd 7 to 10 imply that continental margin pathways and interior basins received the same detritus as the ouachita trough by pennsylvanian time these data are consistent with a composite carboniferous ouachita submarine fan complex built down the axis of a remnant ocean basin from varied mature immature delivery systems tapping dominantly appalachian fold thrust belt sources to the east graham et al 1975 carboniferous turbidites from the marathon fold belt west texas which are isotopically similar nd 8 to 11 to ouachita turbidites may have been ultimately derived from similar sources however they probably do not represent merely distal turbidites of a ouachita fan complex it is suggested that dominantly appalachian derived detritus augmented by uplifted plutonic and fold thrust belt sources south of the marathon basin was swept up into subduction complexes on the north side of the approaching arc and recycled along the collision zone

the use of magnetic susceptibility to measure long term soil redistribution abstract several studies have documented the severity of recent soil erosion on the canadian prairies where cultivation started about a century ago little quantitative information is available on erosion before 1960 this study attempts to quantify post and pre 1960 soil erosion in a small cultivated basin near saskatoon saskatchewan canada by measuring 137cs and magnetic susceptibility distribution with depth soil cores were collected along six transects three across closed depressions and three across the drainage channel in the cultivated field and one transect across an uncultivated depression the cores were sliced into 3 cm layers and the soil analyzed for 137cs and organic and inorganic c high variability in with depth in eroding areas as indicated by 137cs made it impossible to use to quantify past soil losses in these locations however these eroding upper and middle slope positions have a much higher than lower slope areas where soil deposition occurs and where the variability in with depth could be used to estimate soil deposition estimating soil deposition from the vs depth profiles was more successful in the closed depressions than in the drainage channel where the profiles may reflect the variable source areas of the materials rather than the pedological conditions the data indicated that soil deposition since 1960 has been about 30 to 50 of that prior to 1960 this suggests that soil deposition rates and by implication soil erosion rates have been relatively steady since cultivation of these soils started although there are clear indications that the spatial pattern of deposition has varied

nankai trough japan trench and kuril trench geochemistry of fluids sampled by submersible nautile abstract deep water samples collected during the kaiko project are often associated with biological communities located on geological structures favorable to fluid venting the evidence of fluid venting are the temperature anomalies the decrease in sulfate concentrations the content in methane and the lowc 1 c 2 c 3 ratio of light hydrocarbons because of large dilution by ambiant seawater during sampling it is difficult to compute the composition of the advected end member pore fluid part of this fluid should originate in the petroleum window i e at temperature about 60 c modeling the upward flow of water taking into account the anomalies of temperature measured on the seafloor and the geochemical anomalies leads to non steady state advection of the pore fluid the occurrence of a deep component in the fluid has implications for the geological and tectonic models of the subduction zones off japan

a contour based topographic model for hydrological and ecological applications a digital model for discretizing three dimensional terrain into small irregularly shaped polygons or elements based on contour lines and their orthogonals is described from this subdivision the model estimates a number of topographic attributes for each element including the total upslope contributing area element area slope and aspect this form of discretization of a catchment produces natural units for problems involving water flow as either a surface or subsurface flow phenomenon the model therefore has wide potential application for representing the three dimensionality of natural terrain and water flow processes in the fields of hydrology sedimentology and geomorphology three example applications are presented and discussed they are the prediction of zones of surface saturation the prediction of the distribution of potential daily solar radiation and the prediction of zones of erosion and deposition in a catchment

late wisconsinan and holocene history of southwestern saskatchewan the late wisconsinan laurentide ice sheet reached the limit of glaciation along the north facing slope of the unglaciated part of the cypress hills nunatak but elsewhere around the cypress hills and wood mountain uplands of southwestern saskatchewan it did not reach the limit of glaciation an interval of deglaciation was followed by a readvance of the ice sheet about 15 ka to a position near the late wisconsinan limit and was marked by strong flow of keewatin ice from the north and weaker flow of hudson ice from the northeast final deglaciation resulted in the formation of glacial lakes around the cypress hills nunatak a network of ice marginal and subglacial trenches presently occupied by the frenchman valley and its tributaries was formed when these lakes drained along over and under ice towards the western part of the wood mountain upland to the east the main trench joined an ancestral part of frenchman valley along the ice free southern slopes of wood mountain upland meltwater from the ic

zircon typology combined with smnd whole rock isotope analysis to study brioverian sediments from the armorican massif the identification of source materials contributing to mature terrigenous clastic deposits is made difficult due to a lack of useful discriminant criteria sm nd isotope analysis can provide some indication of the present of mantle derived constituents in clastic rocks however since this method is based on whole rock samples it is only possible to obtain the averaged composition of the different source materials involved moreover sm nd isotope systematics can be strongly influenced by the presence of heavy minerals rich in rare earth elements and or displaying isotopic ratios very different to the sedimentary host in this manner 0 1 of zircon or 0 01 of monazite from an extraneous source is sufficient to modify significatively the sm nd signature of the whole rock the typological study of zircon populations is an extremely valuable tool especially since this mineral is highly resistant and exhibits a morphology controlled by the physical and chemical conditions under which it crystallized zircons that have been reworked in a sedimentary deposit display typologies that make it possible to identify the different igneous rock types present in the source region moreover the typological study can be associated with a single grain pb pb dating this twofold approach was applied to brioverian sedimentary rocks neoproterozoic iii to early palaeozoic in age from the central brittany domain armorican massif nw france it is proposed that these deposits inherited a major component from juvenile crustal materials end 540 1 4 to 6 3 reflecting the presence of igneous precursors with a dominantly mantle derived origin zircon sub types s19 s20 s24 s25 etc to which was added another component of crustal anatectic affinity zircon sub types s2 s6 s7 etc two igneous source regions are identified on the basis of the present study the anatectic granitic massifs of the mancellian batholith 540 ma along with a coeval ignimbritic suite of end proterozoic eocambrian age and the syn and post tectonic dioritic massifs 590 to 530 ma apart from these main sources of clastic supply it is very likely that sporadic contributions arose from basic to intermediate volcanic activity of mantle origin linked to the cadomian orogeny and from the icartian basement

another look at rare earth elements in shales linear correlation and mass balance considerations indicate that clays are more important than zircon or other heavy minerals in hosting both light and heavy ree in cratonic shales considering the uniformity of the eu anomaly and ree distributions in cratonic shales it seems likely that detritus is thoroughly mixed during weathering and sediment transport and that the ree patterns in shales reflect the average ree pattern of the sources regardless of the ratio of clays to heavy minerals in the shales shales suspended river loads and near shore marine sediments all have broadly similar ree patterns and reported hree depletions in the latter two groups may reflect incomplete dissolution of heavy minerals during sample preparation ree distributions in shales and suspended river loads determined by inna are similar to those in average upper continent crust and ree distributions in shale averages nasc and paas seem to be reasonably representative of the average composition of post archean upper continental crust

geochemistry of the tenryu canyon deep sea fan biological community kaiko abstract the tenryu canyon deep sea fan biological community is characterized by both reduced and oxidized sediments in the immediate vicinity of the pore water vents the upper sediments in contact with the clams are reduced the organic matter is enriched in sulfur and inorganic sulfides fe cu zn are forming towards the outer fringes of the communities the sediment is oxidized and metals generally associated with ferro manganese oxides are concentrated several metals cd pb mo show distributions which are strongly influenced by the metabolism of the clam colony comparison of water and sediment geochemistry leads to the conclusion that there should be a downward flux of oxygenated seawater on the boundaries of the colony and an upward flux of chemically more reduced deep pore water at the location of the colony trace metals anomalies as well as 15n anomalies of organic matter may be useful to prospect for extinct venting areas in ancient subduction zones

the cr th ratio in precambrian pelites from the kaapvaal craton as an index of craton evolution the cr th ratio in precambrian pelites from the kaapvaal craton in southern africa correlates with pelite th sc and co th ratios and appears to monitor changes in source composition it is a more sensitive indicator of provenance than other commonly used ratios including eu eu la yb and th u pelite cr th ratios are controlled most strongly by the effects of local provenance and local tectonics secular decreases in this ratio the most prominent of which occurred at 2 4 2 3 ga in pelites of the kaapvaal craton record rapid uplift exposing granite decreases in the ratio reflect increases in the abundance of komatiite basalt in sediment sources in response to arc collisions rift hotspot volcanism or intracratonic uplift of older greenstones relatively constant cr th ratios appear to require widespread uplift or and efficient sediment mixing during tectonic stability changes in cr th ratio of kaapvaal pelites reflect a complex tectonic history of the craton from about 3 3 ga to 1 8 ga and do not favor single stage cratonization in the late archean

a holocene soil geomorphic record from the ham site near frontier southwestern saskatchewan the soil geomorphic evolution of a hillslope in hummocky moraine terrain in one of the most arid parts of the palliser triangle is reconstructed from ca 12 600 bp to the present a transect from a moraine plateau into an internally drained basin provided evidence for seven postglacial landscape cycles each cycle includes a phase of land surface instability marked by erosional and depositional imprints and a phase of stability marked by pedologic imprints five cycles of slope wash dominated erosion left behind four superposed downslope thickening and downslope fining sediment mantles and were followed by two eolian cycles each of which left behind a loess mantle that accumulated from a local loess dispersal system accumulation of long range calcareous dust coincided with each of these loess cycles the five complete buried soil catenas and the surficial catena have systematic textural differentiation reflecting the preceding geomorphic regimen and color differentiation reflecting the soil draina

a record of glacial aridity and milankovitch scale fluctuations in atmospheric dust from the pennsylvanian tropics abstract atmospheric dust is an important climatic agent as well as a valuable climatic archive this study documents systematic variations in a single upper pennsylvanian shallow water carbonate buildup of the midland basin west texas that was isolated from fluvio deltaic input and consists almost entirely of carbonate bounded by sequence boundaries thin 0 02 to 1 m intervals of dark pyritic siliciclastic mudrock with subtle pedogenic features occur commonly at the sequence boundaries and are interpreted as loessite deposited during lowstands primarily on the basis of paleogeographic isolation of the buildup the silicate mineral fraction smf extracted from the underlying carbonate which includes quartz clay and trace feldspars and heavy minerals varies in concentration weight from 0 015 to 6 69 in the carbonate this smf contains both fine grained detrital and authigenic silica interpreted to be eolian on the basis of geochemical petrographic and grain size characteristics as well as paleogeography hence the smf is considered a proxy for atmospheric dust whole rock geochemistry suggests that the dust was at least partly derived from uplifts of the ancestral rocky mountains with a possible minor contribution from active volcanic centers located to the present day south and southwest the estimated mean accumulation rate mar of dust in highstand carbonate facies full interglacial relative to carbonate facies that formed during relative fall in sea level suggest that dust flux increased 4 to 10 times accompanying the transition to glacial conditions mars in the siliciclastic mudrock which accumulated at lowstand full glacial to incipient transgression suggest glacial phase increases in dust flux of nearly 400 to 4000 times relative to full interglacial conditions spectral analyses of dust abundance through the study section show variations consistent with milankovitch forcing

ophiolitic source rocks for taconic age flysch trace element evidence flysch generated along the appalachian orogen during the ordovician taconic orogeny ranges in age from late arenig to early caradoc allochthonous flysch and from late llanvirn to ashgill autochthonous flysch sandstones in these units are dominantly lithic arenites with a heavy mineral suite containing common to abundant mg rich chromite north of the canada united states border the only reasonable sources for the chromite were the lower ultramafic units of obducted ophiolites trace element analyses cr ni v cu ti zr y of flysch sandstones indicate a striking increase in cr and ni concentrations from the united states appalachians to the canadian appalachians in the united states units cr is in the range of 10 to 50 ppm canadian flysch units average an order of magnitude more cr these results suggest that ophiolite obduction either did not occur or was of minor importance during the taconic orogeny in the united states appalachians the difference in ophiolite abundance between the canadian and united states appalachians suggests a fundamental difference in tectonic style along the orogen a feature that must be accommodated by plate tectonic models new models will probably need to consider both obliquity of subduction and geological complexity of the ordovician collision zone in order to explain the spatial distribution of obducted ophiolite sheets

inorganic geochemistry of the type caradoc series sandbian to middle katian upper ordovician onny valley shropshire uk the geochemistry and petrology of the type section of the caradoc series in the onny valley indicate that it was deposited on a marginal basin continental shelf similar to the western side of the present sea of japan the lower beds form a transgressive regressive sequence in which the rocks become less mature upwards all the coarser sediments above the basal quartzites and conglomerates are greywackes in which the apparent muddy and ferrous matrix is due to the breakdown of unstable minerals and particles higher values of na 2 o and na k ratios are found in the coarser shallow water sandstones of the horderley sandstone formation and decrease markedly in the succeeding beds accompanied by an increase in k 2 o higher values of carbonate corrected and hence related other major and minor elements like sio 2 cao p 2 o 5 mno and most trace elements correlate with the transgressive systems and maximum flooding surfaces of the three sequences recognized where they are related to condensation at those horizons chemical indices of alteration cia suggest that the horderley sandstone formation underwent greater predepositional physical weathering than lower and higher beds which is compatible with the petrography and were deposited during a cool phase within overall warm sandbian katian times trace element ratios suggest an oxic to suboxic depositional environment

geochemistry of mississippian tuffs from the ouachita mountains and implications for the tectonics of the ouachita orogen oklahoma and arkansas the ouachita orogeny was the result of plate convergence at the southern margin of the north american continent although the nature of the converging southern plate and the direction of subduction remain uncertain the presence of areally extensive tuff layers interbedded with shale in the mississippian stanley group of the ouachita mountains oklahoma and arkansas provides the potential to define the tectonic environment of volcanism from the geochemistry of the tuffs and thereby delimit the subduction configuration the tuffs contain relic primary magmatic quartz plagioclase and alkali feldspar and range from crystal to vitric rich mineralogical sorting and diagenetic effects have caused chemical variability within individual tuff units but overall the tuffs have retained their primary igneous geochemical characteristics the beavers bend and hatton tuffs are geochemically very similar and are more evolved higher sio2 rb th ree lower sr ba than the mud creek tuff the stratigraphically equivalent sabine rhyolite is geochemically distinct from the tuffs having less fractionated rare earth element ree patterns and different trace element ratios both the ouachita tuffs and sabine rhyolite have the geochemical characteristics of subduction related magmas for example strong depletion of nb and ta relative to other incompatible trace elements consideration of trace element systematics in the tuffs compared to those of modern high silica volcanic rocks from different subduction related tectonic settings suggests a continental arc origin and implies southward subduction beneath a southern continent during carboniferous ocean basin closure

tectonic context of fluid venting at the toe of the eastern nankai accretionary prism evidence for a shallow detachment fault during the kaiko nankai diving cruise the peak of the venting activity was located near the top of the very first anticline the most prominent morphological feature between the mid slope 3870 m and the apex of the fold 3770 m is a 20 m high cliff cutting through subhorizontal massive mudstones affected by numerous joints the trend of this scarp is oblique to the fold axis and structurally controlled along two sharply defined nne sse and e w directions fresh talus and blocks found locally suggest active tectonics and recent erosion intense deformation is evident from strongly tilted strata restricted to the base of the cliff that we interpret as an upslope thrust at the scale of seabeam mapping this thrust can be followed eastward for more than 5 km along the 3820 m isobath two seismic lines recorded during one of the pre site surveys show deformation at shallow depth including small scale folding and thrusting affecting only the wedge shaped top sequence deeper layers can be traced continuously below this sequence we conclude that the boundary between the piggy back basin and the frontal fold turbidites acts as a shallow detachment fault and interpret the base of the cliff as the outcrop of the fault dense colonies ofcalyptogena clams and strongly nonlinear thermal gradients locate the major peak of fluid activity at the edge of the plateau above the main cliff scattered biological colonies as well as white bacterial mats and cemented chimneys were also found in a narrow belt along the base of the cliff fluid activity is thus closely related to the shallow detachment fault fluid being expelled both at the outcrop of the fault and above it through the overlying strata possibly using the very dense joint network

elemental mobility in phosphatic shales during concretion growth and implications for provenance analysis shale normalized rare earth element ree patterns record variable redox conditions in coprolitic phosphorite concretions and their host shales from the pennsylvanian age cyclothems in the u s midwestern states of oklahoma kansas nebraska iowa and ohio as well as the mississippian age fayetteville shale of arkansas shale normalized enrichments in middle ree mree developed as the phosphatic concretions lithified under reducing conditions in pore waters of organic rich muds depletions in mree sm ho in host shales correspond to the mree enrichments in some nearby concretions rare and weak negative cerium depletions in both reworked and unreworked phosphorite concretions suggest exposure to oxygenated waters positive europium anomalies in thick phosphorite coatings on coprolitic phosphorite concretion cores suggest extreme reduction during lithification of the phosphorite coating flat ree patterns in both host shales and phosphorite concretions probably reflect detrital influence phosphate diagenesis can affect the trace element chemistry of black shale enough to alter provenance signals overall enrichment in ree in phosphorite relative to host shale suggests movement of ree as does the mree enriched phosphorite near the mree depleted host shale diagenetically mobile ree can affect la th sc relationships used in provenance analysis the extent of the diagenetic modification of la th sc distribution is related to the amount of p2o5 present typical la th sc distribution in host shale results when p2o5 values are below 0 5 high la abundance substantially skews la th sc distribution when p2o5 is above 5 0 but when p2o5 is between 0 5 and 5 0 the extent of the effect is unclear oxides of aluminum and other major elements may be useful in recording detrital influence and proximity to the shoreline in phosphorite concretions most of the concretions nearest to shoreline sources of detrital input have both flat ree patterns and elevated values of al2o3 al2o3 fe2o3

seafloor manifestations of fluid seepage at the top of a 2000 metre deep ridge in the eastern nankai accretionary wedge long lived venting and tectonic implications abstract the results of the 1989 kaiko nankai diving cruise to the eastern nankai accretionary wedge show that a narrow corridor on the top of a 2000 m deep ridge is characterized by concentrated surface manifestations of fluid seepage and chaotic outcrop orientations suggesting active faulting along a right lateral shear zone modern biological indicators of fluid venting include bivalve vesicomyid species and vestimentiferan tube worms ancient manifestations of fluid venting consist of similar vesicomyid species found in 20 and 150 ka concretions this suggests relatively constant biotypes carbonate deposits including fossil cemented shells were observed near active sites either as paving stones diffuse seepage and cementation cut by channels or as pinnacles local seepage and cementation despite its proximity less than 15 km a nearby 3800 m deep site where substantial fluid discharge occurs seems to be completely separate from the 2000 m deep ridge site the 3800 m deep site differs from its shallower counterpart in terms of its seafloor manifestations and the composition of its fluids the sediment at the top of the ridge ranges in age around 500 300 ka which attests that the transition from a depositional to an erosional stage was younger than 800 ka but older than 200 ka this transition can be due to either the incorporation of this unit from the trench fill into the accretionary wedge front or the uplift of a slope basin the first hypothesis leads to a 2 5 cm yr minimum progradation rate associated with a 2 5 mm yr minimum uplift rate from the paleotrench to the present ridge the second hypothesis implies a recent uplift of a piggy back basin at a minimum rate of 1 mm yr

comparison of isotopic and petrographic provenance indicators in sediments from tertiary continental basins of new mexico abstract isotopic variations of nd in sedimentary rocks provide a new tool for provenance determination we have compared the isotopic technique with classic petrographic indicators of provenance in sediments from two tertiary basins of the rio grande rift north central new mexico the siliciclastic sediments in these basins were derived from varying proportions of precambrian basement and oligocene volcanic rocks which are isotopically and petrographically distinct in the analyzed sediments a good correspondence exists between petrographic and isotopic provenance indicators the data also suggest that the isotopic tracer is more sensitive to minor detrital input from a second source than is the framework petrology the similar sm nd ratios for all analyzed sediments and the identical isot pic values of interlayered mudstone and sandstone indicate that no significant fractionation of sm and nd occurs during the formation of the sediments thus the nd model ages of the sediments preserve the crust formation age of the source the sr isotopic and concentration data show trends generally similar to the nd data but they do not indicate the sedimentary provenance as clearly this ambiguity is a consequence of strong rb sr source heterogeneities and rb sr fractionation during the sedimentary cycle

rare earth element distributions among minerals in a granodiorite and their petrogenetic implications a study of the distribution of lanthanide rare earths in a granodiorite from the eastern peninsular ranges batholith southern california reveals that a large fraction of the ree in this rock resides in the accessory phases sphene and allanite the minerals plagioclase alkali feldspar biotite epidote and apatite each contribute approximately 1 or less of each ree to the whole rock with the exception of eu for which plagioclase contributes 7 sphene and allanite together contain 80 to 95 of each ree each of these phases is zoned in ree concentration with substantial decreases from core to margin textural observations argue for relatively early saturation and precipitation of sphene and allanite in the magma ree zoning trends in sphene and allanite and unexpectedly low ree concentrations in largely later crystallizing minerals such as feldspar indicate that the precipitation of sphene and allanite significantly reduced ree concentrations in residual melts these results illustrate the potential that sphene and allanite have for controlling the behavior of ree in granitic magmas available information collectively suggest that the sampled granodiorite existed as a complete melt that the ree contained in the assemblage of phases were derived by direct crystallization from the melt and that the melt behaved essentially as a closed system once crystallization of the phases now present began close correspondences between the major and trace element chemistries of the granodiorite and phenocryst poor lavas from similar tectonic settings support these conclusions the ree pattern of the granodiorite melt appears to have originated at depth and is characteristic of its source regions and derivation mechanism the high liquidus temperature of a granodiorite melt 1000 c indicates the importance of mantle derived components within the sources of batholithic magmas in the peninsular ranges

water and solute transfer between a prairie wetland and adjacent uplands 2 chloride cycle the quality of water in lakes and wetlands depends on the exchange of solutes with adjacent uplands in many prairie wetlands the input of water is dominated by snowmelt runoff and the outputis dominated by groundwater flow we use chloride as a tracer to quantify the mass transfer processes associated with surface runoff and groundwater flow between a wetland in saskatchewan canada and the surrounding upland snowmelt runoff transports 4 5 kg yr 1 of chloride from the upland to the wetland most of this chloride infiltrates under the wetland and moves laterally to the upland with shallow groundwater under the upland chloride moves upward in the vadose zone with soil water and accumulates near the surface as water is consumed by evapotranspiration part of this chloride mixes with snowmelt runoff and moves back to the wetland therefore chloride is cycled between the wetland and the upland at an approximate rate of 5 kg yr 1 the chloride cycle occurs within 5 6 m of the ground surface a small amount of chloride escapes from the cycle with the downward flow of groundwater into the deep aquifer the estimated flux of chloride leaving the cycle is 0 1 0 6 kg yr 1 which is of the same order of magnitude as the rate at which the catchment receives atmospheric deposition of chloride because the atmospheric input is reasonably well known over the prairie region the concentration of chloride in groundwater under recharge wetlands can be used to estimate the recharge rate of deep aquifers

terrain controls on depressional soil distribution in a hummocky morainal landscape in hummocky morainal landscapes soil distribution in well drained landscape positions tends to follow a consistent pattern soils in depressions however are more difficult to predict reliably this study had two objectives 1 to determine the parent material and landscape properties controlling the formation of the different depressional soils and 2 to use these controls to identify quantitative terrain based predictors of soil type in depressions only two terrain attributes specific dispersal area sda and elevation relative to open water bodies were required to distinguish three main soil groups gley recharge non gley recharge and discharge soils specific dispersal area is the downslope area draining flow from a given grid cell gley recharge soils occur primarily at points with sda of less than 2 m2 m 1 regardless of elevation within a given site because most of the runoff flowing to a point with very low sda values will pond or infiltrate vertically rather than flow downslope non gley recharge soils and discharge soils both occur at points with sda of greater than 2 m2 m 1 the majority of the non gley recharge soils occur above 5 m elevation relative to an open water body and the majority of the discharge soils occur below 5 m elevation relative to an open water body reflecting the importance of solute cycling in the development of discharge conditions buried and depositional soils could not be predicted from current terrain attributes because their profile characteristics were derived from the paleosurface

comparative geochemistry of pleistocene and paleoproterozoic huronian glaciogenic laminated deposits relevance to crustal and atmospheric composition in the last 2 3 ga abstract comparison of the major and trace element geochemistry of glaciogenic laminated deposits of pleistocene and paleoproterozoic age from an area north of lake huron ontario has revealed differences and similarities that may provide insight into the erosional history of part of the archean superior province of the canadian shield during the last 2 ga and some aspects of the evolution of the earth s atmosphere both the major element and trace element compositions of the ancient and recent glacial deposits are very similar the paleoproterozoic mudstones are however enriched in fe and u characteristics that may reflect the oxygen content of the archean early paleoproterozoic atmosphere hydrosphere system strong ca depletion is exhibited by the paleoproterozoic glaciogenic argillites but is absent from the pleistocene samples the proterozoic argillites have slightly higher values for a chemical index of alteration than those of pleistocene muds these characteristics may reflect the acid natur

tectonic significance of the cold seepage zones in the eastern nankai accretionary wedge an outcome of the 15 years kaiko projects abstract the tectonic significance of the cold fluid venting in the eastern nankai accretionary wedge has been elucidated based upon results of precise mapping and submersible observation executed since 1984 under the french japanese cooperative projects kaiko i ii kaiko nankai and kaiko tokai in conjunction with studies of the japan trench sagami bay and other regions the very sharp boundary of benthic communities associated with temperature anomalies indicates the occurrence of focused upflow of nutrient rich fluids through cracks in the carbonate crust existing on a near surface horizon of permeable sediment the linear alignment of venting zones is a surface expression of the shallow detachment faults methane rich fluids expelled from the conduit along a fault migrate in the overlying permeable sediment and react with circulating sea water containing sulfate to produce hydrogen sulfide and carbonate precipitate en echelon or zigzag patterns of the cracks are developed in the carbonate crust under the influence of tectonic shear stress it has been concluded that bivalve communities grow on a thin veneer of sediment above the cracks of carbonate through which fluid containing hydrogen sulfide diluted with sea water flows out on the other hand bacterial mats seem to flourish either on thin sediment overlying the fault conduit or over a thick cover of sediment without carbonate crust in the former case bivalves cannot grow because venting fluids are too dense with methane and hydrogen sulfide to maintain the oxygen rich condition of the bottom water in the western nankai trough fine grained less permeable sediment cover seems to prevent circulation of fluids whereas methane appears to be widespread in the deeper sedimentary layer there major distinctions in modes of seepage among sites are presumed to be caused by 1 the tectonic regime causing channels of upward fluid venting 2 rates and composition of venting fluids affected by mixing rates of sea water and 3 the permeability and thickness of the near bottom sediment

water flow in a hummocky landscape in central saskatchewan canada i distribution of water and soils abstract water flow in a hummocky landscape is highly variable in time and space the purpose of the study is to use a classification system based on landscape surface form to delineate areas with similar hydrologic properties the study was conducted in a hummocky landscape with a closed drainage pattern in the black soil zone of saskatchewan the sites consisted of three closed drainage basins 80 150 m across surrounding individual temporary sloughs the distribution of water in the landscape was inferred from in situ electrical conductivity and soil morphological properties including thickness of a and eluviated horizons and depth to calcium carbonate in situ electrical conductivity was strongly correlated with the depth of water in the top 1 2 m of the soil the sites were divided on the basis of landscape surface form into lower slope upper slope and saddle positions which accounted for 30 50 and 20 of the cultivated areas of the basins respectively the lower slope positions were well leached of soluble salts and had high water contents thick a horizons gleyed and or eluviated horizons and thick zones of calcium carbonate depletion the upper slope positions had limited leaching of soluble salts low water contents thin a horizons lacked eluviated horizons and calcium carbonate was present either at shallow depths or at the soil surface the properties of the saddle positions were intermediate between the upper and lower slope positions the spatial distribution of water in the landscape persisted over time due to the redistribution of water in the landscape by topography

digital elevation model networks demon a model of flow over hillslopes for computation of contributing and dispersal areas current algorithms for computing contributing areas from a rectangular grid digital elevation model dem use the flow routing model of o callaghan and mark 1984 which has two major restrictions 1 flow which originates over a two dimensional pixel is treated as a point source nondimensional and is projected downslope by a line one dimensional moore and grayson 1991 and 2 the flow direction in each pixel is restricted to eight possibilities we show that large errors in the computed contributing areas result for any terrain topography divergent convergent or planar we present a new model called digital elevation model networks demon which avoids the above problems by representing flow in two dimensions and directed by aspect demon allows computation of both contributing and dispersal areas demon offers the main advantage of contour based models e g moore et al 1988 the representation of varying flow width over nonplanar topography while having the convenience of using rectangular grid dems

thermal maturity of carboniferous strata ouachita mountains the ouachita mountains a relatively untested potential hydrocarbon province contain a thick paleozoic section of apparently favorable source beds reservoir beds and trap configurations to estimate the thermal maturity of these strata vitrinite reflectance was measured on 89 samples collected mostly from carboniferous rocks from throughout the ouachita outcrop area thermal maturity contours generally parallel structural grain in the western two thirds of the ouachitas reflectance values in oil range from 3 0 in the core area in oklahoma and from about 1 0 to 3 0 in analogous positions in arkansas older strata on upthrown sides of thrust faults are more thermally mature than younger strata on downthrown sides in the eastern one third of the outcrop belt thermal maturities are significantly higher 2 0 5 0 ro and thermal maturity contours cut obliquely across structural grain strata on either side of thrust faults display identical levels of maturity in the western two thirds of the ouachitas sedimentary and tectonic burial have been the major influences of thermal maturation although a mesozoic thermal overprint has increased levels of maturity in arkansas throughout this area strata are within the oil and wet gas windows the anomalous levels and patterns of thermal maturity in the eastern third of the ouachitas are probably the result of a thermal overprint related to mesozoic rifting and intrusive activity in the mississippi embayment this thermal overprint has elevated the maturity of strata in most of this area above the level of hydrocarbon preservation although maturities within the dry gas window are retained locally

the prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models the accuracy of the predictions of distributed hydrological models must depend in part on the proper specification of flow pathways this paper examines some of the problems of deriving flow pathways from raster digital terrain data in the context of hydrological predictions using topmodel distributed moisture status is predicted in topmodel on the basis of spatial indices that depend on flow path definition the sensitivity of this index to flow path algorithm and grid size is examined for the case where the surface topography is a good indicator of local hydraulic gradients a strategy for the case where downslope subsurface flow pathways may deviate from those indicated by the surface topography is described with an example application

southern provenance of upper jackfork sandstone southern ouachita mountains cathodoluminescence petrology the source urea of the upper jackfork sandstone of the southern ouachita mountains of arkansas has been located by means of cathodoluminescence cl of quartz in conjunction with standard petrography comparison of frequency distributions of quartz cl colors between the jackfork and approximately coeval sandstones of the black warrior basin detected genetically based affinities which were not apparent by inspection of gross petrology the upper jackfork was derived from the same source area as the parkwood formation of the black warrior basin of alabama the parkwood is known to have come from the south and so the jackfork did also the jackfork represents a deep water lithologic equivalent of the deltaic and nearshore marine parkwood deposited as turbidites in the deeper water of the ouachita trough