advances in global bioavailable strontium isoscapes abstract strontium isotope ratios 87sr 86sr are a popular tool in provenance applications in archeology forensics paleoecology and environmental sciences using bioavailable 87sr 86sr in provenance studies requires comparing the 87sr 86sr of a sample of interest to that of 87sr 86sr baselines historically these baselines required building empirical datasets from plants or local animals to characterize the 87sr 86sr available to local ecosystems bioavailable 87sr 86sr however researchers are increasingly relying on modeled bioavailable 87sr 86sr maps called isoscapes we review the advantages and limitations of existing approaches to mapping bioavailable 87sr 86sr for provenance studies and propose a globally applicable scalable and editable framework for creating bioavailable 87sr 86sr isoscapes this framework relies on 1 compiling global bioavailable 87sr 86sr data 2 mapping 87sr 86sr variability in rocks 3 leveraging global environmental covariates and 4 applying a random forest regression method that integrates these data to predict bioavailable 87sr 86sr when the random forest model is applied at the global scale it performs well explaining 60 of the variance of the global bioavailable 87sr 86sr dataset and accounts for geological geomorphological and atmospheric controls in data rich regions e g europe the global bioavailable 87sr 86sr isoscape can be successfully extrapolated to broad regions without bioavailable 87sr 86sr data however we also show that this extrapolation may not be valid in exceptionally geologically complex and data poor regions e g madagascar we suggest research directions to improve the accuracy of global bioavailable 87sr 86sr isoscapes which include 1 increasing the collection of bioavailable datasets in data poor regions 2 harmonizing data management practices and metadata collection for bioavailable 87sr 86sr data and 3 relying on advances in remote sensing and geological mapping techniques to improve geological covariates while significant potential to refine 87sr 86sr isoscapes remains the data products provided in this review form a basis for using 87sr 86sr data in large scale provenance studies opening new research avenues in a range of fields

discovery of miocene to early pleistocene deposits on mayaguana bahamas evidence for recent active tectonism on the north american margin we report here the discovery of miocene pliocene and early pleistocene shallow marine carbonates on mayaguana island southeastern bahamas that have so far not been observed on any other bahamian island spanning more than 17 m y but 12 m thick this stratigraphic succession only occurs along the northern coast of the island indicating that the mayaguana bank underwent minor subsidence throughout the late cenozoic and was tilted toward the south during the quaternary in addition to considerably extending the stratigraphic record of the bahamas islands our findings demonstrate that these carbonate banks were at different elevations and subsided at different rates during the neogene the young age of the tilting event detected on mayaguana further shows that parts of the southeastern margin of north america have recently undergone tectonic activity a long way from its actual boundary with the caribbean plate

eaglebine play of the southwestern east texas basin stratigraphic and depositional framework of the upper cretaceous cenomanian turonian woodbine and eagle ford groups the woodbine and eagle ford groups of the southwestern east texas basin compose an emerging play which has generated considerable interest because of its potential for new hydrocarbon production from both sandstone and mudrock reservoirs however the play s stratigraphic and depositional relations are complex and directly relate to the play s exploration challenges productive woodbine and eagle ford sub clarksville sandstones intertongue with a poorly defined subregional mudrock dominated interval that thins southwestward toward the san marcos arch we propose dividing this succession into two intervals 1 the lower unit a high gamma ray unit at the base of this mudrock succession that is inferred to be equivalent to the maness shale of the washita group and to part of the lower eagle ford group on the san marcos arch and 2 an upper unit a basinward thickening zone of consistently lower gamma ray log facies inferred to be equivalent to the woodbine group pepper shale and the eagle ford group of the east texas basin because the cenomanian turonian boundary occurs within the eagle ford group of the east texas basin and the lower eagle ford section of the san marcos arch most of the maness through eagle ford succession exists as a much thinned section on the arch basinwide integration of the woodbine sequence stratigraphic framework shows that the number of fourth order sequences in the unit decreases westward from 14 in the basin axis to no more than 9 in the most active part of the eaglebine play because of their systematic depositional pinch out approaching the western basin margin the eagle ford group consists of three fourth order sequences capped by the sub clarksville sandstones that accumulated after the major late cenomanian early turonian flooding event recorded by a basinwide transgressive systems tract tst at the base of the unit depositional systems of the woodbine group vary within the study area even between stratigraphically adjacent systems on shelf siliciclastic systems include fluvial dominated delta incised valley fill fluvial and nearshore marine and wave dominated delta deposits

evolution of seawater 87sr86sr over the last 400 ka the absence of glacial interglacial cycles abstract fluctuations in the 87 sr 86 sr ratio of seawater accompanying glacial interglacial climate changes have been reported in recent studies but remain highly controversial to investigate these potential fluctuations we present very high precision 13 ppm 87 sr 86 sr measurements on planktonic foraminifera from indian ocean and pacific cores 87 sr 86 sr ratios from three different foraminiferal species are indistinguishable from one another in both core top and 50 ka samples demonstrating that changes due to diagenesis or contamination do not influence the measurements average 87 sr 86 sr ratios for pacific ocean and indian ocean samples are also indistinguishable at three intervals core top 50 ka and 300 370 ka demonstrating that the oceans have remained well mixed with respect to sr also 87 sr 86 sr ratios are not affected by changes in the precleaning of samples measurements from pacific core v28 238 that used in the study of dia et al 1 do not reproduce the cycles seen in the previous study and are statistically well explained by a linear increase in the seawater 87 sr 86 sr ratio it seems likely that an analytical artefact caused the cycles in the previous study measurements from two key sections of core from odp site 758 that used in the study of clemens et al 2 do not reproduce the largest shifts seen in the previous study despite the considerably better precision reported here the apparent cyclicity in the clemens et al 2 data is also suggested to be due to an unknown analytical artefact the 48 measurements presented here are a statistically good fit to a straight line defined by 87sr ppm 0 0613 age ka at the 13 ppm level of precision no evidence for a glacial interglacial variation in the seawater 87 sr 86 sr ratio is seen glacial interglacial variation may still exist but this data constraints its maximum amplitude to 6 9 ppm which would correspond to changes in the riverine sr flux of 30

stratal slicing of miocene pliocene sediments in vermilion block 50 tiger shoal area offshore louisiana many people have viewed modern land surfaces from commercial airplanes and marveled at the form and geometry of geomorphic features such as river channels deltas barrier islands and dune fields these views represent complete images of the modern time surfaces we can classify the depositional nature of features on these images by interpreting their planiform geometry and geographic context in fact modern 3 d seismic technology has made it possible for us to image similar but much older geomorphic or depositional features preserved in the rock record unfortunately although many reservoir scale well to well scale features can be detected in vertical seismic lines few such features can be resolved and interpreted in the vertical perspective because of the data s limited bandwidth only in the horizontal perspective are such depositional features large enough to be resolvable when displayed in map view on geologic time surfaces

tracing dust sources and transport patterns using sr nd and pb isotopes continental dust transported through the atmosphere can be a tracer of atmospheric circulation and transport as well as being a source of information about climate in the dust s source area this information about the provenance of dust transported from desert areas and deposited elsewhere on the oceans and continents can be evaluated using several observational techniques satellite imagery has been used to this end in recent decades and air mass back trajectories have been calculated to trace dust deposits back to their source area another method consists of analysis of the concentration and composition of certain tracers in the dust itself and comparing them to soils and sediments from possible source areas this method has the advantage of being useable for paleo atmospheric circulation and paleo dust transport studies whereas satellite imagery and air mass back trajectories are restricted to relatively recent times we review here different kinds of isotopic tracers that have been used to trace dust provenance but special attention is focused on the use of sr nd and pb isotopes we evaluate their use in studies of both spatially as well as temporally varying continental dust source and transport

genesis of marine terrace soils barbados west indies evidence from mineralogy and geochemistry well developed clay rich soils dominated by interstratified kaolinite smectite are found on the uplifted coral reef terraces on the island of barbados the reef limestone is unlikely to have been the soil parent material however because it is 98 per cent caco3 and geomorphic evidence argues against the 20 m of reef solution required to produce the soils by this process the mineralogy of the sand silt and clay fractions of the soils and trace element geochemistry suggest that aeolian materials carried on the trade winds from africa volcanic ash from the island of st vincent and quartz from tertiary bedrock on the island itself are the parent materials for the soils

miocene chronostratigraphy paleogeography and play framework of the burgos basin southern gulf of mexico this study characterizes miocene chronostratigraphy and plays in the burgos basin and adjacent south texas within an area of approximately 39 700 km2 15 300 mi2 onshore and offshore to the 500 m 1640 ft isobath using greater than 40 000 linear kilometers 25 000 mi of two dimensional seismic lines 115 onshore wells 9 offshore wells and paleontological data we established a correlation framework of 9 key surfaces upper oligocene to lower pliocene representing major probably third order sequence boundaries and maximum flooding surfaces throughout the basin five of the burgos miocene surfaces coincide with regional chronostratigraphic surfaces from the veracruz and laguna madre tuxpan basins thus establishing a consistent correlation framework throughout much of the mexican gulf coast basin twenty miocene plays are defined by four age divisions lower miocene middle miocene upper miocene 1 and upper miocene 2 and four paleogeographic settings unexpanded and expanded shelf proximal slope and distal slope because of proven high productivity in salt bounded basins in the northern gulf of mexico the onlap of strata onto diapirs in the eastern burgos salt province was evaluated as a fifth setting the paleogeographic provinces and onlap areas exhibit characteristic seismic facies stratal geometries and structural relations a characterization of each one of these being key to the overall play evaluation this play framework provides the means for continuing exploration of miocene strata and evaluation of key play elements reservoir presence and quality seal trap source and migration and timing in this structurally complex underexplored basin the relative importance of these play elements varies systematically for each play especially between the onshore shelf plays and the offshore deep water plays where fault complexity and stratigraphic variability are greater

strontium isotopes as tracers of ecosystem processes theory and methods abstract the strontium sr isotope method can be a powerful tool in studies of chemical weathering and soil genesis cation provenance and mobility and the chronostratigraphic correlation of marine sediments it is a sensitive geochemical tracer applicable to large scale ecosystem studies as well as to centimeter scaled examination of cation mobility within a soil profile the 87sr 86sr ratios of natural materials reflect the sources of strontium available during their formation isotopically distinct inputs from precipitation dryfall soil parent material and surface or groundwater allow determination of the relative proportions of those materials entering or leaving an ecosystem the isotopic compositions of labile soil exchange complex and soil solution strontium and sr in vegetation reflect the sources of cations available to plants strontium isotopes can be used to track the biogeochemical cycling of nutrient cations such as calcium the extent of cation contributions from in situ weathering and external additions to soil from dust and rain can also be resolved with this method in this paper we review the geochemistry and isotopic systematics of strontium and discuss the use of this method as a tracer of earth surface processes

insights from stratigraphic modeling mud limited versus sand limited depositional systems quantitative stratigraphic modeling provides new perspectives on the controls on basin fill stacking patterns gross lithology distributions and submarine fan deposition in siliciclastic systems our modeling relates basin fill geometries to the ratio of space creation vs sediment supply facies components differentially distribute sand mud mixtures below rising base level surfaces across a basin profile we model alluvial architecture shoreline position shelf width and the occurrence of turbidite sands as a function of relative base level rise and varying receiving basin geometries slope unconformities and onlapping submarine fans are the erosional and depositional responses to changing basin physiography sediment budgeting reveals two types of siliciclastic systems sand limited systems develop in shallow basins or on basin margin platforms have broad muddy wave graded shelves and are subject to exposure and major basinward shifts of shoreline with minor sea level falls mud limited systems develop during progradation into deep water basins have narrow shelves with turbidites in a base of slope position and are not particularly susceptible to major basinward shifts in facies we emphasize the fundamental importance of basin physiography and lithology budgeting as well as sea level in contrast to eustatically based models in addition to accommodation and sediment supply alluvial architecture and basin depth also act as primary controls on shelf width basin fill geometry and submarine fan deposition

on shelf lower miocene oakville sediment dispersal patterns within a three dimensional sequence stratigraphic architectural framework and implications for deep water reservoirs in the central coastal area of texas through integrating three dimensional seismic and wireline log pattern data we found that the sequence stratigraphic architecture of the lower miocene oakville formation along the central part of the texas gulf coast reveals four third order sequences the lower two containing lowstand lst transgressive tst and highstand systems tracts hst and the upper two appearing to contain only tst and hst these sequences average 1 2 m y in duration the lowstand incised valley fill sandstones are massive as thick as 420 ft 73 m on wireline logs seismic stratal slices demonstrate that the incised valleys are dip oriented and more than 20 mi 32 km wide strata reflections within the incised valleys onlap the sides of the valley the third order tst comprise backstepping high frequency sequences seismic stratal slices and wireline log patterns within the tst suggest deltaic sediment dispersal patterns that appear reworked third order hst comprise aggradational to progradational high frequency sequences and seismic stratal slices and wireline log patterns indicate a variety of depositional environments that we interpreted as deltaic shoreface coastal plain and interdistributary the hst is significantly truncated by the overlying sequence boundary sandstone rich incised valley fills suggest that large amounts of sediment may have been transported through these channels and may have supplied lowstand deposits and associated reservoirs seaward of the previous shelf edge

origin of bermuda s clay rich quaternary paleosols and their paleoclimatic significance red clayey paleosols that are chiefly the product of aerosolic dust deposition are interbedded in the quaternary carbonate formations of the bermuda oceanic island system these paleosols provide a basis for reconstructing quaternary atmospheric circulation patterns in the northwestern atlantic geochemical analyses were performed on representative paleosol samples to identify their parent dust source fine grained fractions were analyzed by energy dispersive x ray fluorescence to determine trace element zr y la ti and nb concentrations and to derive geochemical signatures based on immobile element ratios these ratios were compared with geochemical signatures determined for three possible sources of airborne dust 1 great plains loess 2 mississippi river valley loess and 3 saharan dust the zr y and zr la ratios provided the clearest distinction between the hypothesized dust sources the low ratios in the paleosol b horizons most closely resemble saharan dust in the 2 m size class fraction contributions from the two north american loessial source areas could not be clearly detected thus bermuda paleosols have a predominantly saharan aerosolic dust signature saharan dust deposition on bermuda during successive quaternary glacial periods is consistent with patterns of general circulation models which indicate that during glacial maxima the northeast summer trade winds were stronger than at present and reached latitudes higher than 30on despite lower than present sea surface temperatures in the north atlantic

the characterisation of saharan dusts and nile particulate matter in surface sediments from the levantine basin using sr isotopes abstract the provenance of sediments within the levantine basin of the eastern mediterranean was studied using 87 sr 86 sr isotopic ratios together with major elements measurements were made on the detrital fraction of surface sediments and the two most important sources of detrital matter to the region saharan dust was characterised by an 87 sr 86 sr isotopic ratio in the range 0 7160 0 7192 there was a small systematic decrease in 87 sr 86 sr from west to east which is interpreted as due to a change in the balance of aeolian source material the nile particulate matter had a 87 sr 86 sr isotopic ratio in the range 0 7057 0 7071 87 sr 86 sr isotopic signatures together with sr concentration were used to calculate the contributions made by saharan dust and nile particulate matter to the surface sediments of the levantine basin it was shown that nile derived sediment was dispersed widely across the levantine basin enabling the area affected by retention of sediment behind the aswan dam to be determined

strontium isotopes as indicators of mineral weathering in catchments determination of the 87sr 86sr ratio in rain water stream water soils and rocks in two scottish catchments has provided useful information on mineral weathering over a period of 26 months the 87sr 86sr ratio in rain water had mean values of 0 7095 and 0 7098 n 12 whereas stream water had mean values of 0 7080 n 16 in catchment in devonian andesites with strontium isotope ratios of 0 7117 0 7232 in the rocks and soils and 0 7184 n 16 in catchment of cambrian metamorphic rocks with strontium isotope ratios of 0 7360 0 8218 in the rocks and soils respectively the mineralogy consists predominantly of varying proportions of quartz plagioclase feldspar and k feldspar with some mica and chlorite the fact that the 87sr 86sr ratios in the stream in the andesitic catchment are lower than for the rain water probably indicates preferential weathering of plagioclase feldspar releasing 86sr rather than k feldspar and mica which contain greater amounts of 87sr the 87sr 86sr ratio acts as a tracer for the origin of the solutes in the stream water long term monitoring of the strontium isotope ratio in stream water could be a potential means of detecting relative changes in soil weathering rates due to environmental change

spatial variation of biologically available strontium isotopes 87sr 86sr in an archipelagic setting a case study from the caribbean this paper presents the results of strontium sr isotope analysis of modern and archaeological animal remains and modern plant samples from the caribbean region the goal is to assess if patterns of human mobility can be determined from the archaeological record in an archipelagic setting the range of variability and spatial distribution of biologically available strontium isotope signatures is reported and data evaluated to determine if sufficient heterogeneity exists to permit the identification of mobility despite the presence of potentially large contributions of marine strontium in island and coastal ecosystems the is landscape is divided into several sub regions based on the age and lithology of underlying geology and the variability of

anthropogenic versus natural control on trace element and sr nd pb isotope stratigraphy in peat sediments of southeast florida usa 1500 ad to present abstract analysis of a well dated peat core from blue cypress marsh bcm provides a detailed record of natural and anthropogenic factors that controlled the geochemical cycles of a number of trace elements in florida over the last five centuries the trace elements were divided into natural and anthropogenic groups using concentration trends from the bottom to the top of the core the natural group includes li sc cr co ga ge zr nb cs ba hf y ta th and ree rare earth elements these elements show similar concentrations throughout the core indicating that changes in human activities after european arrival in the new world did not affect their geochemical cycles the anthropogenic group includes pb cu zn v sb sn bi and cd upcore enrichment of these elements indicates enhancement by anthropogenic activities from the early 1500s to present fluxes of the anthropogenic metals to the marsh increased significantly with modern accumulation rates several fold e g v to hundreds of times e g zn greater than pre colonial rates the dominant input mechanism for trace elements from both groups to the marsh has been atmospheric deposition atmospheric input of a number of the elements including the anthropogenic metals was dominated by local sources during the last century for several elements long distant transport may be important for instance ree and nd isotopes provide evidence for long range atmospheric transport dominated by saharan dust the greatest increase in flux of the anthropogenic metals occurred during the 20th century and was caused by changes in the chemical composition of atmospheric deposition entering the marsh increased atmospheric inputs were a consequence of several anthropogenic activities including fossil fuel combustion coal and oil agricultural activities and quarrying and mining operations pb and v exhibit similar trends with peak accumulation rates in 1970 the principal anthropogenic source of v is oil combustion the decline in v accumulation after 1970 in the bcm peat corresponds to the introduction of low sulfur fuels and the change from heavy to distilled oils since the 1970s after the 1920s pb distribution in the peat follows closely the history of alkyl lead consumption in the us which peaked in the 1970s pb isotopes support this inference and furthermore record changes in the ore sources used to produce leaded gasoline idaho ores dominated the peat pb isotope record until the 1960s followed by pb from mississippi valley type deposits from the 1960s to the 1980s enhanced fluxes of cu zn cd sn sb bi and to some extent ni during the last century are likely also related to fossil fuel combustion local agricultural activities may also have influenced the geochemical cycles of cu and zn the peat record shows enhanced u accumulation during the last century possibly related to phosphate mining in western florida sr isotopes in the peat core also reflect anthropogenic influence the 87sr 86sr ratio decreases from natural background values in the basal part of the core to lower values in the upper part of the core the sr isotope shift is probably related to quarrying operations in florida and marks the first time an anthropogenic signal has been detected using the sr isotope record in a peat core

depositional settings and history of the lower miocene fleming group refugio county texas as defined using seismic geomorphology abstract a study of the lower miocene fleming group in refugio county texas from 3 d seismic and wireline log data documents continuous strandplain and associated lower coastal plain fluvial systems along a wave dominated shoreline this study delineates and characterizes through the interpretation of seismic attributes and seismic geomorphology maps from 15 horizons three principal styles of stratal patterns 1 parallel and subparallel strike continuous sets of beach ridge and swale deposits within a strandplain system that prograded at least 12 km 2 sinuous channel belts in a coeval mixed load meanderbelt system and 3 acoustically dim nearly featureless seismic attribute patterns that record homogenous and topographically subdued shallow marine mudstones associated with transgressive marine deposits and flooding surfaces holocene depositional analogs for these lower miocene sandy strandplain deposits include the nayarit coastline in mexico whereas the lower coastal plain between galveston and corpus christi texas serves as an appropriate analog for mixed load meanderbelt systems the lower miocene coastline in refugio county consists of a regressive phase that was punctuated by two transgressive phases these episodes of marine transgression correspond to the anahuac formation and the marginulina a shale respectively succeeding events record complex amalgamated beach ridge deposits and coeval fluvial channel systems that exhibit patterns of channel migration erosion incision and downdip fusion of channel belts this study concludes that potential reservoir geometries and architectures in the lower miocene succession are much more complex than previously inferred the result of rapidly fluctuating and evolving strike fed shoreline systems and contemporaneous fluvial dip dispersal systems some manifested by shore parallel trends confined in swales improved reservoir development strategies in this prolific hydrocarbon bearing play should be guided by distribution of sandy depositional elements and the paleogeographic setting

spatial variation of strontium isotopes 87sr 86sr in the maya region a tool for tracking ancient human migration strontium isotope ratios 87sr 86sr in human bones and teeth have become a useful tool to study migration and sedentism of individuals from archaeological contexts here we analyzed 87sr 86sr of water bedrock soils and plants across a broad geographic region to test the potential of this method in the ancient maya area our aims were two fold first to test if the sources of dietary strontium i e plants and water in humans reflect the 87sr 86sr ratio of exposed bedrock and second to determine whether the ranges of 87sr 86sr values were sufficiently distinct among the principal maya geocultural areas to infer past migration we identified five distinct subregions on the basis of geologic maps and evaluated the variability of 87sr 86sr values values given as mean 87sr 86sr 2 standard deviations number of samples 1 northern lowlands 0 70888 0 00066 n 16 2 southern lowlands 0 70770 0 00052 n 86 3 volcanic highlands and pacific coast 0 70415 0 00023 n 34 4 metamorphic province 0 70743 0 00572 n 50 and 5 the maya mountains of belize 0 71327 0 00167 n 3 although the sample size is small and overlap exists in 87sr 86sr values among some subregions most areas can be readily distinguished from one another on the basis of strontium isotopes these subregional 87sr 86sr differences provide archaeologists with a powerful tool to recognize geographic outliers in ancient maya burials and thereby test hypotheses concerning the origin of specific individuals inferred population migration patterns and the possibility of outside cultural influences in the maya region

mesozoic cenozoic unroofing of the southern appalachian basin apatite fission track evidence from middle pennsylvanian sandstones apatite fission track ages 137 pm 8 to 92 pm 7 ma and mean etchable track lengths 12 1 pm 1 8 to 12 9 pm 1 3 mu m are reported for 10 sandstones from the breathitt formation middle pennsylvanian at the northern end of the pine mountain overthrust in kentucky and virginia because all of the apatite fission track ages are 150 200 m y younger than the depositional age fission tracks that formed in the detrital apatite prior to deposition have been totally annealed thus maximum temperatures attained by these samples exceeded 110 pm 20 circ c the length distribution of etchable horizontally confined fission tracks precludes rapid 10 c m y cooling through the zone of partial annealing 60 125 c assuming a geothermal gradient of 25 pm 5 circ c km and a mean surface temperature of 15 c sandstones at the northern end of the pine mountain overthrust underwent slow erosional unroofing of 4 pm 1 km since the early cretaceous average rate of 28 pm 6 m m y the age t

middle eocene through basal miocene sequence bio stratigraphy of the western gulf coast region abstract this study documents the stratigraphic occurrence of calcareous nannofloral pulses in the middle and upper eocene oligocene and basal miocene of the gulf coastal plain of texas and louisiana the identified floral pulses characterized by high abundance and diversity peaks approximate regional foraminiferal tops and when plotted to the geologic time scale of w a berggren d v kent c c swisher iii and m p aubry 1995 sepm special publication 54 129 212 their relative magnitudes show a sinuous pattern imaging the third order cycles of b u haq j hardenbol and p r vail 1988 sepm special publication 42 71 108 results of comparison suggest that the reklaw is correlated to the third order sequence ta3 1 queen city to ta3 2 and weches to ta3 3 the sparta and cook mountain consist of three sequences correlated to ta3 4 ta3 5 and ta3 6 the lower yegua consists of two sequences correlated to ta4 1 and ta4 2 the upper yegua is correlated to ta4 3 the jackson to ta4 4 and the vicksburg to ta4 5 the lower frio section with regional anomalina bilateralis was developed during the lowest sea level cycle tb1 1 in the oligocene two clusters of floral pulses in younger frio sections are correlated to tb1 2 and tb1 3 two younger clusters of floral pulses in the anahuac are correlated to tb1 4 and tb1 5 ages of these third order sequences are re evaluated based on occurrences of the calcareous nannofossil markers recorded in corresponding floral pulses

strontium isotopes in trees as an indicator for calcium availability summary the increasing acidification and impoverishment of soil poses a great environmental problem today and in the future and is exemplified by the decreased availability of calcium in the soil pool unfortunately budgeting the inputs and outputs of calcium in the soil vegetation ecosystem is a very laborious task some of the fluxes are internal in the ecosystem and cannot be measured explicitely like weathering of primary minerals however since strontium and calcium exhibit similar geochemical behaviour it is possible to make an estimation of the calcium content in different media in the soil vegetation eco system using natural strontium isotopes preliminary analyses of water precipitation throughfall runoff soil water soil mineral matter and biological material trees mussel shells show that the use of the strontium isotope ratio 87 sr 86 sr is a powerful tool in estimating and understanding environmental changes

high frequency 4th order sequence stratigraphy of early miocene deltaic shorelines offshore texas and louisiana abstract well logs and 3d seismic reflection data are integrated to image lower miocene depocenters of the upper texas and westernmost louisiana coastal and offshore areas although previously interpreted at a large scale 3rd order cycles the detailed stratigraphy and depositional history of the early miocene succession has not been fully developed the upper lower miocene interval from robulus l mfs10 to amphistegina b mfs9 has been further subdivided into five 4th order cycles each 200 300 m thick to provide finer scale stratigraphic detail and interpretation of depositional environments results of the finer scale correlations are presented in a series of sandstone percent maps overall the maps display a strike elongate sub parallel to the present day coastline orientation for the sandstone bodies which thin to the southeast basinward net sandstone thickness is relatively low in older cycles and increases in younger cycles suggesting an overall progradation of the deltaic system into the mapped area through time continued marine regression and southward movement of the shoreline are also confirmed by seismic amplitude maps after a major transgression associated with robulus l deltaic progradation occurred under rising sea level conditions deltaic sediments prograded southward and sandstone brought to the upper texas coast was distributed laterally by longshore currents to form strandplain coast lines maximum regression occurred during the interval mfs9 2 to mfs9 3 when a deltaic depocenter formed offshore texas in east high island area however sandstone thickness progressively decreased laterally to the east offshore louisiana where more shale was present and marine processes reworked deltaic derived sandstones into shore parallel bars there was a clear retreat of the shoreline during the youngest cycle marking the beginning of transgression associated with amphistegina b detailed stratigraphic interpretation at a 4th order scale shows more variability in the dominant shoreline processes during early miocene than previously thought recognition of sedimentary systems variability at a 4th order scale is critical for improved hydrocarbon exploration and in understanding potential future co2 storage in the area

mapping 87sr 86sr variations in bedrock and water for large scale provenance studies abstract although variation in 87sr 86sr has been widely pursued as a tracer of provenance in environmental studies forensics archeology and food traceability accurate methods for mapping variations in environmental 87sr 86sr at regional scale are not available in this paper we build upon earlier efforts to model 87sr 86sr in bedrock by developing gis based models for sr isotopes in rock and water that include the combined effects of lithology and time using published data we fit lithology specific model parameters for generalized equations describing the concentration of radiogenic sr in silicate and carbonate rocks the new model explained more than 50 of the observed variance in measured sr isotope values from independent global databases of igneous metaigneous and carbonate rocks but performed more poorly explaining 33 of the variance for sedimentary and metasedimentary rocks in comparison a previously applied model formulation that did not include lithology specific parameters explained only 20 and 8 of the observed variance for igneous and sedimentary rocks respectively and exhibited an inverse relationship with measured carbonate rock values building upon the bedrock model we also developed and applied equations to predict the contribution of different rock types to 87sr 86sr variations in water as a function of their weathering rates and strontium content the resulting water model was compared to data from 68 catchments and shown to give more accurate predictions of stream water 87sr 86sr r2 0 70 than models that did not include lithological weathering parameters we applied these models to produce maps isoscapes predicting 87sr 86sr in bedrock and water across the contiguous usa and compared the mapped sr isotope distributions to data on sr isotope ratios of us marijuana crops although the maps produced here are demonstrably imperfect and leave significant scope for further refinement they provide an enhanced framework for lithology based sr isotope modeling and offer a baseline for provenance studies by constraining the 87sr 86sr in strontium sources at regional scales

mineralogical evidence for a local volcanic origin of the parent material of bermuda quaternary paleosols the alternation of carbonate deposits and paleosols compose the emerged part of the bermuda archipelago the pedological units present a complex and diversified mineralogy former studies demonstrated that the paleosols are not primarily a product of the unique dissolution of the surrounding carbonates but contain a massive input of allochthonous non carbonate detrital material researchers during more than the past three decades have attributed this flux of insoluble residues ir to saharan dusts we carried out systematic field and mineralogical analyses on the quaternary paleosols from the bermuda archipelago their mineralogical assemblage predominantly includes carbonates clay minerals kaolinite chlorite and chlorite vermiculite phosphates and aluminium and iron oxides hydroxides this assemblage is strikingly close to the mineralogy of the weathered volcanic substrate of bermuda but noticeably different from the mineralogy of saharan dust moreover we found volcanic lithoclasts in numerous paleosol profiles all over the archipelago and in all the recorded time intervals we thus consider the volcanic seamount underlying bermuda as the main source of non carbonate minerals detected in the paleosols this hypothesis further resolves the anomalous maturity of bermudan paleosols compared to their southern counterparts in the bahamas and barbados

late cretaceous fluvial megafan and axial river systems in the southern cordilleran foreland basin drip tank member of straight cliffs formation and adjacent strata southern utah u s a abstract the upper cretaceous lower campanian drip tank member of the straight cliffs formation in the grand staircase region of southern utah is an upward coarsening sandstone rich low sinuosity fluvial deposit in the cordilleran foreland basin the drip tank member thins from 75 m to 30 m eastward across the basin foredeep approximately parallel to its dominant eastward sediment dispersal direction and thins southward along the foredeep to as little as 17 m near its southern outcrop extent along modern cliff lines it overlies and underlies mudstone rich fluvial strata of the john henry member of the straight cliffs formation and lower member of the wahweap formation respectively both of which were deposited by northeast flowing rivers the john henry drip tank contact lies in an interfingering progradational stratigraphic transition from medium grained lenticular sandstone bodies to tabular coarse grained amalgamated sandstone bodies the contact with the overlying wahweap formation is locally a prominent surface of erosion or sediment reworking sandstone petrography and detrital zircon age populations of the strata indicate detrital sources in basement south of the foreland basin thrust sheets to the west and magmatic arc rocks to the southwest the uppermost part of the john henry member contains as much as 10 feldspar and abundant 1 84 1 60 ga detrital zircons derived from yavapai mazatzal basement rocks in the mogollon highlands the drip tank member ranges from quartzarenite to chert bearing sublitharenite with grenville 1 2 1 1 ga neoproterozoic and early paleozoic detrital zircons derived from proterozoic through jurassic strata exposed in the sevier orogenic belt lower member wahweap litharenites contain abundant thrust belt derived detrital carbonate grains absent from compositionally mature drip tank sandstones as well as a broad range of zircon ages the drip tank member constitutes deposits of a sand rich fluvial megafan or distributive fluvial system that displaced a subjacent but partly time equivalent axial fluvial system eastward as the megafan driven in part by seasonally high discharge fed by monsoonal precipitation prograded across the basin foredeep a thick amalgamated fan axis succession present in northern exposures contrasts with a thinner fan flank succession in southern localities tabular sixth order lithosomes each containing channels on the order of 7 m deep define three individual fluvial fans or fan lobes in the megafan system younger wahweap fluvial channels eroded uppermost drip tank deposits of the fan axis and fan flank transverse fan progradation across the foredeep recorded falling accommodation sediment supply in an aggradational to progradational systems tract erosion and reworking of the upper fan surface record decreased accommodation sediment bypass and erosion prior to reoccupation of the foredeep by the wahweap axial fluvial system the upper contact of the drip tank member is thus the primary sequence boundary in this multi component fluvial system and the lower wahweap represents transitional systems tract deposits accumulated as accommodation sediment supply increased

mapping and defining sources of variability in bioavailable strontium isotope ratios in the eastern mediterranean abstract the relative contributions of bedrock and atmospheric sources to bioavailable strontium sr pools in local soils was studied in northern israel and the golan regions through intensive systematic sampling of modern plants and invertebrates to produce a map of modern bioavailable strontium isotope ratios 87 sr 86 sr for regional reconstructions of human and animal mobility patterns the study investigates sources of variability in bioavailable 87 sr 86 sr ratios in particular the intra and inter site range of variation in plant 87 sr 86 sr ratios the range of 87 sr 86 sr ratios of plants growing on marine sedimentary versus volcanic geologies the differences between ligneous and non ligneous plants with varying growth and water utilization strategies and the relative contribution of atmospheric sr sources from different soil and vegetation types and climatic zones results indicate predictable variation in 87 sr 86 sr ratios inter and intra site differences in bioavailable 87 sr 86 sr ratios average of 0 00025 while the range of 87 sr 86 sr ratios measured regionally in plants and invertebrates is 0 7090 in pleistocene calcareous sandstone and 0 7074 in mid pleistocene volcanic pyroclast the 87 sr 86 sr ratios measured in plants growing on volcanic bedrock show time dependent increases in atmospheric deposition relative to bedrock weathering the 87 sr 86 sr ratios measured in plants growing on renzina soils depends on precipitation the spacing between bedrock 87 sr 86 sr ratios and plants is highest in wet conditions and decreases in dry conditions the 87 sr 86 sr ratios measured in plants growing on terra rossa soils is relatively constant 0 7085 regardless of precipitation ligneous plants are typically closer to bedrock 87 sr 86 sr ratios than non ligneous plants since the bioavailable 87 sr 86 sr ratios currently measured in the region reflect a mix of both exogenous and endogenous sources changes in the relative contribution of exogenous sources can cause variation over time precipitation the age of the bedrock and the overall sr concentration must to be taken into consideration when interpreting geographical variation in strontium isotopes throughout a region because these factors can change through time we recommend that sr data from time periods older than the holocene be interpreted with caution

geochemical evidence of saharan dust parent material for soils developed on quaternary limestones of caribbean and western atlantic islands abstract most previous workers have regarded the insoluble residues of high purity quaternary limestones coral reefs and oolites as the most important parent material for well developed clay rich soils on caribbean and western atlantic islands but this genetic mechanism requires unreasonable amounts of limestone solution in quaternary time other possible parent materials from external sources are volcanic ash from the lesser antilles island arc and saharan dust carried across the atlantic ocean on the northeast trade winds soils on quaternary coral terraces and carbonate eolianites on barbados jamaica the florida keys united states and new providence island bahamas were studied to determine which if either external source was important caribbean volcanic ashes and saharan dust can be clearly distinguished using ratios of relatively immobile elements al 2 o 3 tio 2 ti y ti zr and ti th comparison of these ratios in 25 soils where estimated ages range from 125 000 to about 870 000 yr shows that saharan dust is the most important parent material for soils on all islands these results indicate that the northeast trade winds have been an important component of the regional climatology for much of the quaterary saharan dust may also be an important parent material for caribbean island bauxites of much greater age

genetic stratigraphic sequences in basin analysis ii application to northwest gulf of mexico cenozoic basin the northwest gulf of mexico cenozoic sedimentary wedge illustrates the application of genetic stratigraphic sequence analysis and documents several general conclusions 1 sequences defined by regional marine flooding are the principal genetic stratigraphic units of the basin fill continental margins are characterized by repetitive episodes of basin margin offlap punctuated by periods of transgression and marine flooding of the depositional platform 2 continental margin outbuilding is concentrated at one or more shelf edge deltaic depocenters separated by interdeltaic bights depocenters remain fixed during a depositional episode but commonly relocate during transgression and flooding 3 a distinct syndepositional structural style in prograding continental margins results in sporadic uplift of a basin fringing peripheral bulge and accentuates preservation of shelf margin facies along zones of extensional normal faulting and enhanced subsidence 4 genetic stratigraphic sequences commonly reflect an evolving interplay among two or even three variables for example early cenozoic gulf sequences are most closely related to tectonic events of the intraplate source terrane which in turn affect rate and location of sediment supply and basin margin response to loading late cenozoic sequences more closely reflect proposed eustatic cycles

miocene sequence biostratigraphy of the northern gulf of mexico abstract calcareous nannofossil abundance and diversity curves have been successfully used for biostratigraphic sequence modeling in the gulf of mexico miocene well data from the trend reveal that floral pulses characterized by high abundance and diversity correspond to regional foraminiferal tops these pulses vary greatly in magnitude in the studied wells and when plotted on a time track show a sinuous pattern imaging the third order cycles of haq et al 1988 results indicate that floral pulses of regional significance in the miocene of the gulf of mexico are a counterpart of transgressive systems tracts of fourth order sequences correlations of these pulses foraminiferal tops and eustatic cycle curves first proposed by jiang and watkins 1992 are updated in this study the results link biostratigraphy with sequence stratigraphy and will assist in integrating micropaleontologic data in sequence stratigraphic modeling

variable hfsrnd radiogenic isotopic compositions in a saharan dust storm over the atlantic implications for dust flux to oceans ice sheets and the terrestrial biosphere isotopic characterization of aerosol mineral particles atmospheric dust of varying sizes is essential in classifying source areas and for determining the source of dust deposited over oceans and icesheets however the effect of atmospheric transport on radiogenic isotopic compositions is not well constrained making provenance interpretation difficult in order to investigate the isotopic variability of 176hf 177hf 87sr 86sr and 143nd 144nd we analyzed eight airborne dust samples in two size fractions collected along a cross atlantic transect through a dust storm originating in the sahara in late 2002 past measurements of 176hf 177hf 87sr 86sr and 143nd 144nd of dust have focused primarily on coarse sized particles 30 m whereas far field deposition is primarily finer particles 2 m strontium or neodymium isotopic sorting based on distance is not evident in our dataset however the combined isotopic ratios of the dust collected suggest a saharan origin hafnium isotopic compositions show an east to west trend towards more radiogenic compositions across the atlantic suggesting grain and mineral sorting during dust transport along the 4000 km transect transport models with variable dust particle diameter and wind speed demonstrate the preferential depletion of the high density mineral zircon during transport of dust from the source area the transport model combined with a simple two component mixing model show that the hf isotopic composition changes can be explained by the loss of the mineral zircon during transport modeling of this zircon effect with distance from the dust source in the hf isotopic composition of marine terrestrial and glacial dust deposits may reveal additional information concerning dust transport and sources in the geologic past

spatial variations in biosphere 87sr 86sr in britain abstract strontium isotopes are a powerful tool for investigating the geographical origins of people and animals but assignment of provenance requires reference maps and databases this paper presents a map of strontium isotope variations across britain for use in archaeological and other studies and is produced by direct measurement of strontium isotope compositions of biosphere components predominantly plants the map characterizes the biosphere signature of specific lithologies a technique that is applicable worldwide marine derived strontium from both rainwater and coastal sea splash and spray is an important contribution to the british biosphere particularly on the western seaboard which is subject to high rainfall and prevailing westerly winds supplementary material methods full data table and full size version of figure 1b are available at http www geolsoc org uk sup18388

absence of saharan dust influence on the strontium isotope ratios on modern trees from the bahamas and turks and caicos islands we report on strontium 87 sr 86 sr isotope results from 91 modern trees growing on the bahamas and turks and caicos islands the average 87 sr 86 sr ratio of 0 709169 0 000010 is consistent with the late quaternary limestone of the islands and with the modern ocean value the absence of any detectable influence of 87 sr enriched saharan dust is notable given the known contribution of this material to both past and recent soils of the caribbean our results indicate that the impact of saharan dust to the modern biosphere of the bahamian archipelago is at least an order of magnitude less than modeled in currently available strontium isoscapes for the circum caribbean we suggest that the bioavailability of sr in saharan dust may be considerably less than previously thought nevertheless further work could usefully be carried out in the bahamian archipelago on plants with different rooting depths growing on different soil types and on limestone of different ages our results have particular relevance for the refinement of existing strontium isoscapes and the archaeological provenience of artifacts animals and people in the circum caribbean

sequence stratigraphic distribution of coaly rocks fundamental controls and paralic examples significant volumes of terrigenous organic matter can be preserved to form coals only when and where the overall increase in accommodation approximately equals the production rate of peat accommodation is a function of subsidence and base level for mires base level is very specifically the groundwater table in paralic settings the groundwater table is strongly controlled by sea level and the precipitation evaporation ratio peat accumulates over a range of rates but always with a definite maximum rate set by original organic productivity and space available below depositional base level groundwater table below a threshold accommodation rate nonzero no continuous peats accumulate due to falling or low groundwater table sedimentary bypass and extensive erosion by fluvial channels this is typical of upper highstand lowstand fan and basal lowstand wedge systems tracts higher accommodation rates provide relatively stable conditions with rising groundwater tables mires initiate and copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received september 7 1995 revised manuscript received november 25 1996 final acceptance may 5 1997 2exxon production research company 3120 buffalo speedway houston texas 77096 3exxon production research company 3120 buffalo speedway houston texas 77096 present address conoco inc p o box 2197 houston texas 77252 we benefited from the input and assistance of many people of special assistance were the teams involved in collaborative studies with esso australia and esso malaysia p moore m sloan j emmett b burns a partridge s creaney hanif hussein r hill r lovell and m feeley we also thank the rock springs team r beauboeuf p mclaughlin w devlin a carroll y y chen g grabowski jr k miskell gerhardt m farley r webster and j schwalbach group members d curry and j yeakel were always helpful we also enjoyed and profited from many discussions of these concepts with our colleagues outside exxon c diessel r boyd k shanley b zaitlin p mccabe m hendricks a cohen and m kirschbaum we thank the reviewers of company reports whose careful comments on several generations of this work improved it s creaney m feeley j van wagoner f wehr j yeakel and a young f weber and j zullig provided extensive management support k linke translated our sketches into the fine figures herein we value all the help

neodymium and strontium isotopic constraints on soil sources in barbados west indies abstract neodymium and strontium isotopic compositions and sm nd ratios are used to constrain the sources of silicate rich soils developed on uplifted pleistocene coral reef limestones on barbados west indies the geographic and geologic setting of barbados facilitates the application of these tracers to the evaluation of the following soil sources 1 pleistocene reef limestone regolith 2 tertiary carbonate rocks sandstones and mudstones that are exposed in northeastern barbados 3 volcanic ash erupted from the lesser antilles arc 4 saharan dust transported by trade winds and 5 fertilizer the soils have nd values that range from 6 6 to 1 9 87 sr 86 sr values of 0 70890 to 0 71067 and sm nd ratios of 0 223 0 260 the pleistocene limestone component is the most significant source of sr in the soils and a negligible source of nd comparison of sm and nd concentrations and neodymium isotopic compositions of soil samples that are weathered to varying extents indicates that sm and nd are relatively unfractionated and retained in the soils during weathering nd and sm nd variations in the soils therefore primarily reflect the compositions and proportions of the silicate sources mass balance calculations based on sm nd systematics require that the silicate soil components contain between 30 85 volcanic ash with the remaining silicate fraction comprised of old continentally derived sediment in contrast to sm and nd sr is mobilized and removed from the soils during weathering strontium from volcanic and carbonate sources is preferentially removed relative to continental silicate sources the strontium isotopic compositions of the soils therefore reflect the combined effects of the degree of weathering and the compositions and proportions of the soil sources mass balance calculations indicate that at least 35 60 of the initial sr in the soils has been removed by weathering these results illustrate 1 the utility of radiogenic isotopes in identifying and quantifying soil sources and weathering processes 2 the compositional influence of numerous sources on soils even those developed in a relatively isolated area such as barbados and 3 the domination of barbados soil sm nd systematics by nonregolith eolian components

high frequency miocene sequence stratigraphy offshore louisiana cycle framework and influence on production distribution in a mature shelf province the regressive miocene succession of offshore louisiana comprises 10 third order sequences and no fewer than 58 fourth order sequences which average approximately 1 1 and 0 19 m y in duration respectively comparable to durations measured in the gulf coast basin and basins worldwide upper lower to middle miocene distal third order sequences comprise mostly lowstand prograding wedge slope fan and basin floor fan deposits in contrast middle to upper miocene medial sequences record progressively more landward systems tracts 1 the lateral transition between on shelf incised valley fills and the proximal parts of basinward thickening lowstand prograding wedges and 2 cyclic on shelf highstand and transgressive systems tracts upper miocene inner shelf and marginal marine systems tracts and more abundant incised valleys dominate the thinner proximal third order sequences this genetic framework has a major influence on hydrocarbon distribution although a strong structural trapping component is present in the fields more than 90 of cumulative production originates where fourth order systems tracts stack to form third order lowstand systems tracts in all 10 third order sequences the development of a high frequency sequence framework for the prolific miocene succession and the discovery that hydrocarbons are pooled within the miocene third order lowstand systems tracts yield a focused model for the development of abundant undiscovered miocene reserves in the mature northern gulf of mexico shelf province

depositional styles from miocene through pleistocene in the north central gulf of mexico an historical reconstruction abstract the minerals management service u s department of the interior has recently classified the producible sands from the approximately 1 100 fields across the northern gulf of mexico into groups of genetically related plays defined by production chronostratigraphy lithostratigraphy and structure each field was assigned a structural code and each producible sand was classified by depositional environment correlation of the type logs with biostratigraphic and seismic data established 13 chronozones from lower miocene to upper pleistocene sands within each chronozone were classified as transgressive aggradational progradational or submarine fan facies hydrocarbon plays encompassing all discovered resources were mapped for each chronozone this paper describes the distribution and continuity of hydrocarbon plays in the louisiana ocs comprised of discovered resources in sands deposited by the ancestral mississippi river delta pronounced changes in depositional styles and hydrocarbon prone areas are observed from the lower miocene through the pleistocene as the ancestral mississippi river delta migrated basinward and across offshore louisiana lower miocene hydrocarbon plays are restricted to the western portion of the louisiana shelf a marked eastward migration of the depocenters occurred in middle miocene during the upper miocene the depocenter began migrating to the west and extended significantly basinward throughout the pliocene and pleistocene the depocenter migrated basinward and westward the distributions of known hydrocarbon plays provide an organized framework for exploration analogs

role of sea level forced sedimentary processes on the distribution of organic carbon rich marine sediments a review of the late quaternary sapropels in the mediterranean sea abstract the 124 ka to present sapropel s5 s1 series in the eastern mediterranean sea correspond to the last glacial interglacial period and permit detailed investigation of 5th order sedimentary frequencies the sapropel layers are clustered in high frequency milankovian cycle that occur within sequence stratigraphic 4th order cycles of late pleistocene holocene sea level oscillations the sea level changes had an amplitude exceeding 120 m and have been correlated to the glacial interglacial cycles modulated by the 100 ka eccentricity using published data we examined occurrences of the complete s5 s1 series in the mediterranean sea and then we focussed on two stratigraphic sequences in the central adriatic shelf and middle adriatic depression where sapropels s5 and s1 were deposited during periods of sea level rise recorded by the transgressive systems tract marine isotopic stage 5 and 1 respectively sapropels s4 and s3 were deposited during the highstand systems tract that developed throughout mis 5 of the late pleistocene sequence sapropel s2 should have been deposited during the warm mis 3 3 and followed the mis 4 sea level drop when sediment supply was enhanced during the late highstand and falling stage of sea level of the late pleistocene sequence the pronounced mis 2 cold stage led to a lowstand and to the regional erosional surface sequence boundary we also compared the adriatic sapropel s5 s2 sequence 4th order to the mid pliocene cluster o sequence 3rd order in both cases sapropels are well formed before the increase of sediment supply due to progradation of the shelf wedge that occurs in the late high stand and initial falling stage in sea level finally we considered the influence of sea level lowering which could cause a weakening of north adriatic deep water formation therefore influencing the mediterranean deep water circulation this condition would favour oxygen depletion but it does not correspond to a well developed sapropel as in the case of s2 based on the assumption that productivity increases related to insolation play a dominant role in their sedimentation sapropel s2 is the result of low amplitude insolation maxima that were unable to generate a productivity increase leading to the burial of conspicuous amount of organic matter therefore in the adriatic sea the absence of the s2 sapropel is correlated to the high sedimentation rate diluting the signal whereas in the eastern mediterranean basin this sapropel is virtually absent because of a weak orbital forcing combined with oxidation that erased its record

the importance of sea spray to the cation budget of a coastal hawaiian soil a strontium isotope approach soil nutrients such as ca mg and k are traditionally thought to be derived primarily from rock weathering here we show that sea spray is a significant source of nutrient elements to modern and buried soils developed on 30 000 year old pahala ash deposits 50 m from the coast at south point hawaii the soil profiles evolved in a semi arid climate and have always been above sea level and the water table rhizoliths fossilized root traces and horizontal laminated carbonate sheets found in buried soils are composed of high mg calcite up to 14 mol mgco3 differences in strontium isotopic composition between marine aerosols 87sr 86sr 0 7092 and tephra parent material 0 7035 allow quantification of cation sources to the labile soil reservoir and to pedogenic carbonate mixing equations indicate that 50 80 of labile soil sr and approximately half of carbonate sr was derived from marine sources using the sr isotopic signatures and sr ca ratios of seawater and tephra as end members we determined that up to 2 3 of the ca in the labile reservoir and up to 1 3 of ca in the carbonates has a marine origin carbonate 87sr 86sr ratios are fairly constant with depth but labile 87sr 86sr ratios indicate decreasing sea spray aerosol influence with depth this trend could be due either to sequestering of aerosol derived sr in the upper part of the profile or to lower aerosol input in the past due to lower sea level the unusual occurrence of high mg pedogenic calcite probably results from high labile mg ca ratios during earlier stages of weathering coupled with rapid calcite precipitation during soil pore water evaporation

tobago west indies a fragment of a mesozoic oceanic island arc petrochemical evidence the pre cenozoic rocks of tobago west indies represent an exceptional cross section through a portion of a composite mesozoic arc system other parts of which may be found in the villa de cura klippe the aruba blanquilla island chain and perhaps in the western cordillera of colombia and ecuador the geochemical data from tobago presented in this paper provide a basis from which a regional view of the petrologic character of the accreted mesozoic arc of the southern caribbean mountain system can be deduced the mesozoic rocks of tobago can be divided into four main groups the north coast schist the ultramafic to mafic plutonic complex the tobago volcanic group and late mafic dykes rocks of the north coast schist served as wallrock for the plutonic volcanic dyke complex which evolved during the mid cretaceous geochemical and nd and sr isotopic data presented demonstrate the oceanic island arc character of all the pre cenozoic rocks of the island all suites span the calc alkaline and tholeiitic regions on discrimination diagrams rare earth element ree patterns for the north coast schist tobago volcanic group and plutonic suite are essentially identical and are moderately lree enriched la yb 1 1 2 7 the dykes exhibit the most unevolved ree patterns and are interpreted as most closely representative of parental liquid compositions initial nd 6 6 to 9 4 and 87 sr 86 sr 0 70303 0 70364 for all samples except north coast schist and tobago volcanic group argillites are similar in value and overall range to other oceanic island arcs limited isotopic data from argillite samples from tobago suggest an important change in the continental derived sediment contribution during mesozoic arc growth nd isotopic data from north coast schist siliceous argillite indicate virtually no continental detritus in this neocomian sediment while nd isotopic data from the tobago volcanic group argillite suggest a definite continental contribution during albian arc growth

from seismic stratigraphy to seismic sedimentology a sensible transition abstract the concept of seismic stratigraphy was developed during the 1970 s based on 2 d seismic technology utilizing reflection terminations configurations and external forms interpreted from multiple seismic profiles geologists could analyze seismic facies within depositional sequence boundaries and infer regional scale depositional environments and depositional history three dimensional seismic data provide spatially dense high resolution horizontal reflection patterns for improving seismic facies analysis and make seismic sedimentology a reality a step beyond seismic stratigraphy seismic sedimentology is the study of depositional facies lithology and architecture by using the relationships between spatial reflection patterns and the morphology of depositional systems a major obstacle facing seismic interpreters used to be their inability to pick reservoir scale depositional surfaces on vertical seismic profiles this problem has been largely resolved by a technique called stratal slicing stratal slicing tries to pick depositional surfaces by proportionally slicing between two reference seismic events stratal slices from two 3 d seismic volumes in louisiana illustrate that seismic sedimentology can significantly improve seismic facies analysis by 1 reducing ambiguity in seismic facies and lithologic interpretation 2 increasing vertical resolution from the third order sequence 100 m to the reservoir 10 m level and 3 helping identify reservoir scale depositional architecture

impact of regional variation in detrital mineral composition on reservoir quality in deep to ultradeep lower miocene sandstones western gulf of mexico abstract future exploration in lower miocene sandstones in the gulf of mexico will focus increasingly at depths greater than 4 5 km and reservoir quality will be a critical risk factor in these deep to ultradeep reservoirs the goal of this study was to understand the variation in reservoir quality of lower miocene sandstones across the western gulf of mexico to do this we examined regional variation in detrital mineral composition diagenesis and reservoir quality in five areas 1 louisiana 2 upper texas coast 3 lower texas coast 4 burgos basin mexico and 5 veracruz basin mexico using petrographic and petrophysical data from depths of 0 9 7 2 km there are strong variations in mineralogical composition within the study area lower miocene sandstones from offshore louisiana have an average composition of quartz 86 feldspar 12 and rock fragments 2 q 86 f 12 r 2 feldspar and rock fragment content increase southward as source areas shifted to include volcanic and carbonate rocks composition of samples from offshore texas ranges from q 67 f 24 r 9 in the upper texas coast to q 58 f 24 r 19 in the lower texas coast lower miocene sandstones from the onshore burgos basin northern mexico have an average composition of q 54 f 22 r 23 whereas sandstones from the veracruz basin southern mexico contain the highest proportion of rock fragments q 33 f 12 r 55 main diagenetic events in quartz rich lower miocene sandstones in louisiana were mechanical compaction and precipitation of quartz cement compactional porosity loss increased to the south with increasing rock fragment content calcite is the most abundant cement in the south and is strongly related to reservoir quality loss at moderate burial depths the best reservoir quality occurs in quartz rich sandstones in louisiana and decreases with increasing lithic content in texas and mexico porosity is higher in louisiana and upper texas than in lower texas and mexico at all depths and temperatures but at depths 5 km and temperatures 175 c porosity differences are lessened the lower miocene sandstone trend in the western gulf of mexico from louisiana to mexico is an example of the importance of variation in detrital mineralogy as a control on diagenesis and reservoir quality

origins of peri saharan dust deposits traced by their nd and sr isotopic composition abstract isotopic ratios of sr and nd can be used as very precise tracers in conjunction with mineralogical geochemical tracers and climatic models to identify the origins of dust deposit and to quantify their fluxes both today and throughout the last climati cycles this technique is useful for constraining aeolian transport and atmospheric circulation trajectories from desert sources and over the oceans the present work concerns dust deposits surrounding the saharan desert on the canary islands the african fraction of the dust deposits displays isotopic values which are typical of moroccan origin on the other hand tunisian loesses have been derived from the northern part of the sahara in this case tracers are sensitive enough to distinguish between center saharan shield origin and peri saharan secondary sources allowing us to distinguish between transport due to the trade winds vs the harmattan or mediterranean wind regimes

precise chronology of the last interglacial period 234u 230th data from fossil coral reefs in the bahamas a detailed study of 238 u 234 u 230 th ages was made for different coral species from two bahamian reefs to determine the time scale of the sea level high during the last interglacial period using recently developed mass spectrometric techniques for the measurement of u and th isotopes thirty seven coral samples were analyzed in replicate typical errors at 125 ky are 1 5 ky 2 and 3 ky time intervals appear to be well resolved this high precision permits detailed chronologic study with time resolution adequate to define stages of the reef s history these data demonstrate that the time between transgression and regression of the ocean in the last interglacial was about 12 ky after which sea level fell rapidly at more than 2 m ky the high sea level stand began possibly by 132 ky and certainly by 129 ky ago when sea level reached 6 m above present mean low sea level high sea level was sustained until 120 ky and then fell rapidly this time period covers the milankovitch insolation peak at 65 n but is not sharply defined and the sea level high lasted from about 4 ky before the insolation peak to 8 ky after it we find no evidence for a double peak of sea level rise in the last interglacial episode that is high stands at both 125 and 142 ky there appears to be some discrepancy between this precise chronology for a coral reef on a tectonically stable platform and the chronology assigned to deep sea sediments the present results show that the duration of the last interglacial led to a 12 ky period of high sea level stand which is much longer than the insolation peak the study area consists of two sizeable bank barrier coral reefs of sangamon age that crop out along the coast northwest of cockburn town on san salvador island and at devil s point on great inagua island the initial stage of reef development is not revealed at either site but the main parts of both reefs are well preserved at cockburn town the beginning of the reef was marked by colonization of acropora palmata on hardground areas and possibly other corals at 132 ky ago patch reefs at the southeastern flank of the developing reef were growing by 129 to 126 ky ago by 126 to 123 ky ago the crest of the reef was formed by the frame building coral a palmata and associated patch reefs flourished along its flanks a palmata coral heads grew upward to a mean low sea level 6 m above the present one the reef began to decline as sea level dropped at about 123 to 120 ky ago near two measured profiles at devil s point the top of a rubblestone dominated by a cervicornis and patch reef corals preserved in growth position have been beveled off and represent an ancient wave cut surface 230 th ages on corals below and above this surface indicate that it was cut at about 125 1 ky ago

the first large scale bioavailable sr isotope map of china and its implication for provenance studies abstract strontium isotope ratio 87sr 86sr has been widely used to trace human migrations across geologically distinct landscapes in archaeological and forensic sciences 87sr 86sr based provenance studies require a detailed strontium reference map to make valid interpretations of mobility patterns for a given region in this study we first review the previous development for 87sr 86sr isoscapes relevant to research on migration and then present the first map of bioavailable 87sr 86sr ratios for china based on 1935 measurements on biosphere samples collated from published research and supplemented by our targeted collection strategy the results show that 87sr 86sr ratios in china span a large range and exhibit regional patterns largely dependent on the divergent geological conditions of each of china s tectonic blocks we further combine river water 87sr 86sr ratios with lithology integrated elemental data and chemical weathering rates to determine which dominant weathering patterns e g silicate carbonate or evaporite have the most significant influence on 87sr 86sr ratios the low ranges of 87sr 86sr ratios 0 7125 appear in the cathaysia block as well as some orogenic belts and the southeastern margin of the tibetan plateau likely due to the influence of the metamorphic rocks and granitoid sources additionally topography differential weathering among lithologies and eolian deposits e g loess are also significant factors that influence 87sr 86sr ratios in china our study reveals that the large variation of 87sr 86sr ratios across china is predominately driven by geological conditions revealing that future sr isotope provenance studies can shed on ancient and historical migrations in china

sr isotope evidence for population movement within the hebridean norse community of nw scotland the excavation at cnip isle of lewis scotland of the largest and only known family cemetery from the early norse period in the hebrides provided a unique opportunity to use sr isotope analysis to examine the origins of people who may have been norwegian vikings sr isotope analysis permits direct investigation of a person s place of origin rather than indirectly through acquired cultural and artefactual affiliations sr isotope data suggest that the norse group at cnip was of mixed origins the majority were consistent with indigenous origins but two individuals of middle age and different sex were immigrants they were however not from norway but were raised separately most probably on tertiary volcanic rocks e g the inner hebrides or ne ireland or for the female on marine carbonate rocks

floral pulses foraminiferal peaks and inferred sequences in the miocene of the northern gulf of mexico abstract investigation of miocene calcareous nannofloral pulses in 10 deep wells from the northern part of the west cameron and neighbouring ocs areas offshore south western louisiana gulf of mexico shows that nannoplankton pulses closely match previously determined foraminiferal peaks a framework of correlation has been constructed for these pulses and foraminiferal peaks and they have been successfully tied to the third order eustatic cycles although essentially confirming the cycles of haq et al 1988 these data suggest the following conclusions 1 the tb1 tb2 supercycle boundary coincides with the top of the anahuac in the basal miocene downdip the boundary is recognized at the lower limit of the lowstand correlated with cristellaria r 2 of the six third order cycles in tb2 tb2 4 is the most prominent it persists from 17 4 to 14 0 m y bp and the condensed interval is correlated with robulus 43 tb2 3 is relatively brief as it persists for only about 1 3 million years 18 7 to 17 4 m y bp deposits of this cycle correlated with robulus chambersi and discorbis b are often missing or incomplete in the study area the subjacent cycle tb2 2 is stratigraphically above siphonina davisi and its condensed interval is correlated with the second marginulina a peak 3 the condensed interval of tb2 5 corresponds to cristellaria i and that of tb2 6 to textularia w the tb2 tb3 supercycle boundary coincides with the upper limit of globorotalia fohsi robusta that berggren et al 1985 dated 11 5 m y bp 4 the most significant sea level drop during miocene time occurred in cycle tb3 1 this drop resulted in the absence of most of nanno zone nn8 in the study area downdip sediments of this cycle are successionally characterized by from top to bottom bolivina thalmani discorbis 12b textularia l cibicides inflata bigenerina 2 and cibicides carstensi 5 the transgressive systems tract of tb3 2 is successionally characterized by cristellaria k amphistegina e and cyclammina 3 other upper miocene markers bigenerina a robulus e textularia 6 and textularia x occurred during the highstand of this cycle 6 sediments of the youngest miocene cycle tb3 3 are missing in the study area due to deep erosion during lowstand of tb3 4 in the early pliocene the lower pliocene encountered in five of the 10 studied wells was also analysed the data suggest that the condensed interval of the lower pliocene cycle tb3 4 is correlated with the buliminella 1 peak and that of tb3 5 with globigerina nepenthes

interpretive advantages of 90 phase wavelets part 2 seismic applications we examine field seismic data to test the benefits of 90 phase wavelets in thin bed interpretation that are predicted by seismic modeling in part 1 of this paper in an interbedded sandstone shale miocene succession in the gulf of mexico basin a 90 phase shift of nearly zero phase seismic data significantly improves lithologic and stratigraphic interpretation a match between seismic and acoustic impedance ai profiles results in a better tie between seismic amplitude traces and lithology indicative logs better geometric imaging of ai units that does not use dual polarity seismic events results in easier and more accurate reservoir delineation less amplitude distortion and the stratigraphy independent nature of thin bed interference significantly improves stratigraphic resolution and seismic stratigraphic profiling for a ricker like wavelet having small side lobes stratigraphic resolution of 90 phase data is considerably higher than that of zero phase data in this specific case stratigraphic re

holocene saharan dust deposition on the cape verde islands sedimentological and nd sr isotopic evidence holocene aeolian silts deposited on the cape verde islands provide information about the origin of african palaeodusts that have fallen on the north eastern atlantic ocean over the last 10 000 years sedimentological composition indicates that most of these aeolian silts are unquestionably of continental origin their sr and nd isotopic composition identifies a saharan origin suggesting transport by harmattan winds we estimate that saharan dust comprises 75 95 of material in these holocene silts the rest coming from the weathering of local basaltic bedrock

seawater sr isotope variation over the past 300 kyr and influence of global climate cycles the past 300 000 years have been characterized by glacial inter glacial fluctuations accompanied by glacio eustatic changes in sea level and changes in continental erosion arising from varying low latitude rainfall and river drainage here we use measurements of strontium isotopes in foraminifera and corals to place limits on variations in the sr isotope composition of sea water in response to these changing inputs we find small variations of about 20 p p m in the 87sr 86sr ratio which for the foraminiferal record seem to follow a cycle close to the 100 kyr periodicity seen for a number of other climate related phenomena these are superimposed on a general increase in87sr 86sr through the cenozoic to the present on short timescales these changes are likely to be controlled by variations in the global riverine sr flux and thus by weathering rates rather than in the hydrothermal sr flux at mid ocean ridges we show that transient variations over a 50 kyr timescale can be explained on the basis of the present day global drainage system in conjunction with the perturbations expected to accompany climate changes over the past 300 kyr

investigating equid mobility in miocene florida usa using strontium isotope ratios abstract despite extensive research on the evolutionary history and ecology of horses surprisingly little is known about the daily and seasonal movements i e mobility of extinct species we used strontium isotope ratios 87sr 86sr in tooth enamel to estimate mobility patterns of equids from two miocene fossil sites in northern florida usa thomas farm ca 18 ma and love bone bed ca 9 5 9 ma the species included in our sample have a range of body sizes 45 252 kg and reconstructed diets gomphotheres and tapirs from love bone bed were also included to represent browsers based on modern species behavior we predicted small bodied and browsing taxa living in closed habitats had limited mobility and 87sr 86sr similar to local northern florida limestone we anticipated larger bodied and grazing taxa living in open environments had increased mobility with higher and more variable 87sr 86sr reflecting larger movements across differing geologies contrary to expectations the majority of taxa at both sites have higher 87sr 86sr than expected for local eocene bedrock and instead are similar to contemporary late oligocene to mid miocene seawater the most plausible explanation for these findings is that most individuals foraged close to the paleo coastline where vegetation would have been influenced by marine derived strontium via sea spray or precipitation tapirs have considerably higher and more variable 87sr 86sr than horses or gomphotheres at love bone bed which may reflect foraging on aquatic vegetation in the river channel that is preserved at the site our results suggest that horses were relatively sedentary in florida even during their peak radiation

strontium isotopes and nutrient sourcing in a semi arid woodland sr isotopes are widely used as a tracer of sr and ca in surficial systems basalt flows ranging in age from 3 ka kiloyears ago to 200 ka from el malpais national monument emnm new mexico provide an ideal setting to examine strontium and hence calcium cycling by plants in a semi arid woodland to gauge plant dependence on atmospheric dust versus local weathering products for strontium and calcium we measured 87sr 86sr ratios in local bedrock and soils and compared them to leaf wood cellulose of four different conifers a deciduous tree three shrubs an annual c4 grass and a lichen sampling sites varied by parent material limestone sandstone granite and basalt and age quaternary to precambrian providing a wide range in end member 87sr 86sr ratios whereas the target plant species varied in physiognomy life history and rooting depth on non basalt parent material the contribution from dust changed with the supply of weatherable sr bearing minerals in local bedrock soils developed on paleozoic limestone showed significant bedrock contributions on basalts the sr budget of soils at emnm is dominated by atmospheric dust on young 3 ka flows incorporates a mixture of basalt dust in 9 ka flows and is basalt dominated in 120 ka flows this is unlike the pattern observed in tropical soils developed on basalt in hawaii where basalt weathering dominates the sr inventory of the youngest soils and aerosols dominate in older deeply weathered soils this contrast is mainly due to different water rock w r ratios bedrock subjected to high w r over short periods is quickly 10 ka depleted in sr and ca except for the ongoing replenishment from aerosols in arid settings where w r are lower soil sr is still abundantly available first from dust and increasingly from bedrock even after 120 ka for plants 87sr 86sr variations within and across sites at emnp showed that evergreen trees varied most in 87sr 86sr ratios shrubs were least dependent on eolian input of sr and both foliage density and rooting depths influence soil sr pools

siliciclastic sequence stratigraphy and petroleum geology where to from here modern sequence stratigraphy has its roots in the development of seismic stratigraphy in the late 1960s to middle 1970s peter r vail and his colleagues at exxon production research company developed stratigraphic techniques and principles based on time stratigraphic rather than rock stratigraphic lithostratigraphic relationships using multi fold seismic reflection data seismic stratigraphic units called depositional sequences were recognized within which the strata seemed conformable and free of any internal stratal discontinuities based on global seismic stratigraphic observations these workers inferred a eustatic signal and developed global sea level curves despite shortcomings the sequence stratigraphic approach represents a powerful geological tool at the field development scale improved reservoir source and seal prediction can enhance petroleum recovery at the exploration scale this approach can be instrumental in developing new play concepts in both mature and frontier basins to realize the full potential of this method earlier conceptual models must be substantiated and modified 80 refs 2 tabs

petrography stable isotope geochemistry and diagenesis of miocene sandstones vermilion block 31 offshore louisiana abstract sandstones from three conventional cores between depths of 11 140 and 14 910 feet currently have an average composition of q86f10r4 but have lost approximately 5 percent feldspar to replacement by carbonates and to dissolution like other deeply buried gulf coast sandtones plagioclase is being albitized and k feldspar is dissolving patterns of feldspar distsribution in the deeper cores suggest that tight cementation by calcite retarded feldspar diagenesis and that waters of different composition or temperature must have invaded different sandstone beds in close proximity calcite quartz and chlorite are most responsible for causing deterioration of reservoir quality calcite volume averages 4 8 percent and occludes all pores in samples containing more than 5 percent calcite textural relations and isotopic data indicate that calcite precipitated over a broad temperature range and from fluids of variable composition during burial the 87sr 86sr ratio of cements is consistent with the derivation of the sr from coeval or only very slightly older skeletal material prior to extensive silicate reactions the volume of quartz cement ranges from 0 to 14 percent mean 5 and is selective to coarser cleaner sandstones that had the highest permeability 18o values of quartz overgrowths 34 2 smow suggest that quartz cement precipitated between temperatures of 35 to 50 c from water having a 18o of about 3 1 5 silica for quartz cement was largely imported because there is negligible pressure solution of silicate grains and the amount of silica released from feldspar alteration is insufficient to account for the present quartz volume chlorite is not abundant and its diagenesis is complex including two stages of precipitation and a later stage of dissolution the first episode of precipitation formed thin grain coats that rarely inhibited quartz cementation a later episode partly filled both primary and secondary pores and strongly influenced permeability total thin section porosity ranges from 0 to 31 percent and averages 16 percent of total pores 75 percent are intergranular 17 percent are oversize pores inferred to have formed by feldspar dissolution 6 percent are intragranular pores 1 percent are oversize pores developed by fossil dissolution and a trace are micropores within clay clasts glauconite rocks fragments and clay cements

perspectives on the sequence stratigraphy of continental strata this report is the result of a working group on continental sequence stratigraphy that was set up at the 1991 nuna conference in banff canada to date sequence stratigraphic concepts have been applied mainly to the marine realm but unconformity bounded units have long been recognized in nonmarine strata successful application of sequence stratigraphic concepts to continental strata requires careful consideration of controls on base level and sediment supply as with shallow marine environments relative sea level can be considered as the stratigraphic as well as the geomorphic base level for coastal nonmarine settings farther inland stratigraphic base level which determines accommodation space is more complex and takes various forms such as the graded profile for fluvial strata groundwater tables for some eolian strata and lake level for some intermontane sediments sediment supply is also generally a more complex variable for nonmarine environments than in the marine realm because of the proximity to the source area the influence of climate and tectonism on sediment supply can clearly be seen in many continental sediments the fact that the major controls of climate tectonism and eustasy are somewhat interdependent and that a change in one parameter will most likely be reflected in others is also more readily apparent in continental strata although in its infancy sequence stratigraphic concepts have been applied to a wide variety of continental settings in attempts to explain variations in facies architecture of particular interest are studies that have linked fluvial architecture on coastal plains to variations in relative sea level as indicated by coeval marine strata and studies of lacustrine environments that show marked variation in facies between highstand and lowstand deposits the application of sequence stratigraphy to continental strata will likely result in the development of better correlation techniques and models that better predict the location and nature of fluvial and eolian reservoirs

linked sequence stratigraphy and tectonics in the sichuan continental foreland basin upper triassic xujiahe formation southwest china abstract intracontinental subduction of the south china block below the north china block in the late triassic resulted in formation of the transpressional sichuan foreland basin on the south china block the upper triassic xujiahe formation was deposited in this basin and consists of an eastward tapering wedge of predominantly continental siliciclastic sedimentary rocks that are up to 3 5 km thick in the western foredeep depocenter and thin onto the forebulge and into backbulge depocenters five facies associations a e make up the xujiahe formation and these are interpreted respectively as alluvial fan transverse and longitudinal braided river meandering river overbank or shallow lacustrine and deltaic deposits this study establishes a sequence stratigraphic framework for the xujiahe formation which is subdivided into four sequences sq1 2 3 and 4 sequence boundaries are recognized on the basis of facies tract dislocations and associated fluvial rejuvenation and incision and systems tracts are identified based on their constituent facies associations and changes in architectural style and sediment body geometries typical sequences consist of early to late transgressive systems tract deposits related to a progressive increase in accommodation and represented by facies associations a b and c that grade upwards into facies association d regionally extensive and vertically stacked coal seams define maximum accommodation and are overlain by early highstand systems tract deposits represented by facies associations d e and c late highstand systems tract deposits are rare because of erosion below sequence boundaries sequence development in the xujiahe formation is attributed to active and quiescent phases of thrust loading events and is closely related to the tectonic evolution of the basin the sichuan basin experienced three periods of thrust loading and lithospheric flexure sq1 lower sq2 and sq3 two periods of stress relaxation and basin widening upper sq 2 and sq3 and one phase of isostatic rebound sq4 paleogeographic reconstruction of the sichuan basin in the late triassic indicates that the longmen mountains to the west consisting of metamorphic sedimentary and pre neoproterozoic basement granitoid rocks was the major source of sediment to the foredeep depocenter subordinate sediment sources were the xuefeng mountains to the east to backbulge depocenters and the micang mountains to the northwest during the late history of the basin this study has demonstrated the viability of sequence stratigraphic analysis in continental successions in a foreland basin and the influence of thrust loading on sequence development

the geology of eleuthera island bahamas a rosetta stone of quaternary stratigraphy and sea level history abstract a 5 km stretch of coastline in north eleuthera reveals a long and detailed stratigraphy that includes all known surficial limestone units in the bahamas and supplements the record with several previously unrecognized ones eight paleosol bounded limestone parasequences comprise at least six interglacial periods the lithostratigraphy demonstrates cyclicity at several frequencies 10 5 10 4 20 40 ka and 10 3 years and displays a variety of distal to proximal shoreline facies indicative of shifting depocenters associated with changing sea levels stratigraphy petrology pedology and whole rock aminostratigraphy are used to correlate units and subunits among the 12 described sections amino acid ratios are also converted to absolute age estimates which support the lithostratigraphy the parasequences are correlated with marine oxygen isotope stages 1 to 13 or older evidence of middle pleistocene highstands are abundant in the eleutheran stratigraphy including paleo sea levels of decreasing age at 2 m 7 m 20 m associated with stages 11 and or 9 and two near present highstands during stage 7 a complex sea level history is associated with substage 5e while substage 5a is represented by near shore aggradation of coastal dune complexes in eleuthera and throughout the bahamas concordance of sea level deposits between bermuda and the bahamas reinforce their tectonic stability while the abundance of highstand evidence during the middle pleistocene contradicts suggestions that platform subsidence has obscured all evidence of these events below present sea level the high resolution late quaternary stratigraphy of eleuthera is unrivaled among geologic records from stable carbonate coastlines and thereby offers a rosetta stone for interpretation of the quaternary evolution of the bahamas and sea level history over the past 500 ka

sequence stratigraphic relationships and facies architecture of turonian campanian strata kaiparowits plateau south central utah outcrop study of the straight cliffs formation in the kaiparowits plateau allows examination of facies tract development within a sequence stratigraphic framework this approach provides a new perspective to regional chronostratigraphic and lithostratigraphic relationships of turonian through campanian strata these strata are arranged in geometric patterns that can be related to lowstand transgressive and highstand system tracts

changing sources of base cations during ecosystem development hawaiian islands 87 sr 86 sr evidence from a soil chronosequence in the hawaiian islands demonstrates that the atmosphere supplies 85 of putatively rock derived sr in older sites initially bedrock is the dominant source for sr and other lithophile elements such as ca but high rates of weathering and leaching of the substrate by 20 ka lead to a shift to atmospheric sources the loss of weathering inputs coincides with other physio chemical changes in the soil and results in a steep decline of base cations in the soil pool while these patterns imply the potential for limitation of biological productivity by low base cation supply the atmosphere provides a supply of base cations in excess of nutritional needs even after nearly all rock derived base cations have been leached from the soil this raises the possibility that p limitation in terrestrial ecosystems may develop at least as much because of low rates of atmospheric deposition of p relative to ca k and other rock derived elements as because of its chemical interaction in soil

geochemical evidence for african dust inputs to soils of western atlantic islands barbados the bahamas and florida 1 we studied soils on high purity limestones of quaternary age on the western atlantic ocean islands of barbados the florida keys and the bahamas potential soil parent materials in this region external to the carbonate substrate include volcanic ash from the island of st vincent near barbados volcanic ash from the islands of dominica and st lucia somewhat farther from barbados the fine grained component of distal loess from the lower mississippi river valley and wind transported dust from africa these four parent materials can be differentiated using trace elements sc cr th and zr and rare earth elements that have minimal mobility in the soil forming environment barbados soils have compositions that indicate a complex derivation volcanic ash from the island of st vincent appears to have been the most important influence but african dust is a significant contributor and even mississippi river valley loess may be a very minor contributor to barbados soils soils on the florida keys and islands in the bahamas appear to have developed mostly from african dust but mississippi river valley loess may be a significant contributor our results indicate that inputs of african dust are more important to the genesis of soils on islands in the western atlantic ocean than previously supposed we hypothesize that african dust may also be a major contributor to soils on other islands of the caribbean and to soils in northern south america central america mexico and the southeastern united states dust inputs to subtropical and tropical soils in this region increase both nutrient holding capacity and nutrient status and thus may be critical in sustaining vegetation

87sr 86sr ratios in modern and fossil food webs of the sterkfontein valley implications for early hominid habitat preference this research addresses the potential contribution of strontium isotopes to the reconstruction of early hominid behavior at the swartkrans site in the sterkfontein valley of gauteng provence formally known as the transvaal south africa we report that while there is considerable variability in the 87sr 86sr of whole soils within a 15 km radius of this site available soil and grassland plant 87sr 86sr is much less variable and generally above 0 730 this value is higher more radiogenic than the 87sr 86sr of plants growing within the greenbelt surrounding the blaaubank stream adjacent to swartkrans and streamwater itself 0 721 the difference between grassland and riparian strontium isotope composition suggests a method for determining habitat utilization by early hominids in this study a geological explanation for a natural difference between blaaubank stream and grassland sr is suggested based on relatively less radiogenic sr having lower 87sr 86sr values in the carbonate component of the local dolomite when compared to other nearby geological formations the explanation was tested initially using a top down approach in which the 87sr 86sr ratios of water soil and plants from the entire blaaubank catchment were measured next a bottom up approach was used to examine swartkrans member i faunal species known to have obtained their sr from well defined habitats the results are that 1 pollution is not the explanation for the relatively low 87sr 86sr ratios of the blaaubank stream 2 swartkrans member i carbonate has a similar 87sr 86sr to that of modern blaaubank water indicating that relationships seen today existed in the pleistocene and 3 pleistocene riparian fauna have relatively low 87sr 86sr ratios when compared to fauna adapted to drier habitats together these results make it possible to interpret the strontium isotope composition of pleistocene early hominids from swartkrans in terms of habitat utilization