modeling regional salinization of the ogallala aquifer southern high plains tx usa two extensive plumes combined area 1000 km 2 have been delineated within the ogallala aquifer in the southern high plains tx usa salinity varies within the plumes spatially and increases with depth cl ranges from 50 to 500 mg l 21 variable density flow modeling using sutra has identified three broad regions of upward cross formational flow from the underlying evaporite units the upward discharge within the modeled plume area is in the range of 10 24 10 25 m 3 day 21 and the tds concentrations are typically 3000 mg l 21 regions of increased salinity identified within the whitehorse group evaporite unit underlying the ogallala aquifer are controlled by the structure and thickness variations relative to the recharge areas distinct flow paths on the order of tens of km to 100 km in length and varying flow velocities indicate that the salinization of the ogallala aquifer has been a slow ongoing process and may represent circulation of waters recharged during pleistocene or earlier times on going pumping has had negligible impact on the salinity distribution in the ogallala aquifer although simulations indicate that the velocity distribution in the underlying units may have been affected to depths of 150 m after 30 years of pumping because the distribution of saline ground water in this region of the ogallala aquifer is heterogeneous careful areal and vertical characterization is warranted prior to any well field development q 2000 elsevier science b v all rights reserved

repeatability of microseism measurements in port hueneme case study abstract microseism measurements can assist in prediction of ground motion amplification and microzonation a series of array measurements were conducted in the port hueneme california area the measurements were repeated and the error of microseism measurements is discussed from the seven individual trials it was possible to show the convergence of microseism measurements and their repeatability the series of array measurements of microseisms used both a soil and a rock reference site the soil site was a site having a well defined boring log a comparison is made between results obtained using a rock and a soil reference site it was found that qualitatively the general dimensionless shape of relative amplification contour plots was similar using both reference sites both reference sites showed the same regions as having higher amplification compared with other lower regions

groundwater recharge circulation and geochemical evolution in the source region of the blue nile river ethiopia geochemical and environmental isotope data were used to gain the first regional picture of groundwater recharge circulation and its hydrochemical evolution in the upper blue nile river basin of ethiopia q mode statistical cluster analysis hca was used to classify water into objective groups and to conduct inverse geochemical modeling among the groups two major structurally deformed regions with distinct groundwater circulation and evolution history were identified these are the lake tana graben ltg and the yerer tullu wellel volcanic lineament zone ytvl silicate hydrolysis accompanied by co2 influx from deeper sources plays a major role in groundwater chemical evolution of the high tds na hco3 type thermal groundwaters of these two regions in the basaltic plateau outside these two zones groundwater recharge takes place rapidly through fractured basalts groundwater flow paths are short and they are characterized by low tds and are ca mg hco3 type waters despite the high altitude mean altitude 2500 masl and the relatively low mean annual air temperature 18 c of the region compared to sahelian africa there is no commensurate depletion in d 18 o compositions of groundwaters of the ethiopian plateau generally the highland areas north and east of the basin are characterized by relatively depleted d 18 o groundwaters altitudinal depletion of d 18 o is 0 1 100 m the meteoric waters of the blue nile river basin have higher d excess compared to the meteoric waters of the ethiopian rift and that of its white nile sister basin which emerges from the equatorial lakes region the geochemically evolved groundwaters of the ytvl and ltg are relatively isotopically depleted when compared to the present day meteoric waters reflecting recharge under colder climate and their high altitude 2005 elsevier ltd all rights reserved 1 background surface water of the blue nile river basin of ethiopia is not widely used for water supply because of its marked seasonality and lack of proper technology to retain it in the basin groundwater is the most important source of water and is the dominant source for domestic

origin and evolution of lunettes on the high plains of texas and new mexico lunettes isolated dunes on the lee side of playa basins are common landforms on the southern high plains of northwest texas and eastern new mexico the dunes contain calcareous 15 40 caco3 sandy loam or loamy sand with minor amounts of sepiolite deposited 25 000 800014c yr b p and derived by deflation of lacustrine carbonate in the basins the dunes also contain low carbonate 0 15 caco3 sand or loamy sand that was deposited 25 000 15 000 yr b p and 8000 5000 yr b p and was derived by deflation that created the basins or deflated from sand deposited in the basins buried soils are common in the lunettes a bk profiles characterize soils formed in the calcareous sandy loam the sandy low carbonate sediments contain a bt profiles in the oldest sand of some dunes and a bw a bt or a btk in the early and middle holocene sand the dune stratigraphy combined with carbon isotope data derived from dated a horizons in lunettes suggests the following scenario for the southern high plains the lunettes began forming as low carbonate sand dunes in the late pleistocene as playa basins were formed or deepened by wind erosion the erosion repeatedly alternated with stability the environment probably was cool and dry but one or more cool and wet intervals 25 000 15 000 yr b p resulted in a rise in the water table and deposition of lacustrine carbonate in the deepest basins there may have been short departures toward warmer and probably toward drier conditions throughout this time episodically dry conditions 15 000 8 000 yr b p resulted in deflation of the carbonate and further dune construction by repeated accretion of calcareous sandy loam or loamy sand the low carbonate sand was deposited during widespread drought and deflation 8000 5000 yr b p the dunes have been largely stable in the late holocene

burial of organic carbon and pyrite sulfur in sediments over phanerozoic time a new theory in present day marine sediments almost all of which are deposited in normal oxygenated seawater rates of burial of organic carbon c and pyrite sulfur s correlate positively and bear a constant ratio to one another c s 3 on a weight basis by contrast calculations based on the isotopic model of garrels and lerman 1981 indicate that at various times during the phanerozoic the worldwide burial ratio must have been considerably different than the present day value this ratio change is caused by the requirement that increases in the worldwide mass of organic carbon must be accompanied by equivalent decreases in the mass of sedimentary pyrite sulfur in order to maintain a roughly constant level of o2 in the atmosphere such apparently contradictory behavior can be explained if the locus of major organic carbon burial has shifted over time from normal marine environments as at present to non marine freshwater or to euxinic environments in the geologic past a shift to predominantly freshwater burial can help explain predicted high c s ratios in permo carboniferous sediments and a shift to euxinic environments can help explain predicted low c s ratios during the early paleozoic it is demonstrated that the three environments today exhibit distinguishably different average c s ratios

playa lake basins on the southern high plains of texas and new mexico part i hydrologic geomorphic and geologic evidence for their development playa lake basins of the southern high plains texas and new mexico may originate wherever water periodically can collect in a surficial depression they expand however by hydrologic and geomorphic processes including 1 dissolution of lithologic carbonates by infiltrating water 2 transport downward of fine grained clastic and organic material by the infiltrating ground water leading to continuing processes of oxidation and carbonate dissolution in the subsurface and 3 eolian removal of clastic material from the floor of playa lakes which at some sites appears to have deepened playa depressions evidence for largely hydrologic processes of playa basin development on the southern high plains includes 1 a geographic occurrence restricted to relatively flat areas of the high plains surface that have poorly developed fluvial drainage and which are underlain by generally unsaturated clastic and calcrete beds 2 a tendency to occur where water collects and infiltrates as along ephemeral streams and lineations suggestive of fracture systems and 3 hydrologic geochemical petrographic and bore hole data which suggest that recharge to the high plains aquifer is principally from playa lakes that various geochemical changes including carbonate dissolution and enhancement of secondary porosity occur as water moves downward through the unsaturated zone beneath playa lakes and that calcrete beds often are missing or significantly dissolved beneath playa floors

influence of paleoenvironmental factors on preservation of organic matter in middle cretaceous greenhorn formation pueblo colorado sedimentological and geochemical studies of the upper cretaceous hartland shale and overlying bridge creek limestone members of the greenhorn formation reveal close associations between abundance of current induced sedimentary structures extent of bioturbation and type of preserved organic matter abundant hydrogen rich organic matter 4 5 wt and low sulfur to organic carbon ratios are characteristic of the laminated facies which lack current induced sedimentary structures sparse hydrogen poor organic matter 0 1 0 5 wt and relatively high sulfur to organic carbon ratios are characteristic of the bioturbated facies which contain numerous sedimentary structures indicative of currents the concentration of oxygen in the benthic environment and the degree of bio urbation of the sediment apparently were determined principally by the rate that oxygen was supplied advectively by currents rather than by the rate of oxygen consumption by decomposition thus paleoclimatic and paleo oceanographic factors that influenced mixing and current strength in the water column profoundly affected the amount and type of organic matter preserved in these units it is proposed that episodes of high river discharge lead to density stratification of the water column and in turn to quiescent oxygen depleted bottom water and high preservation of organic matter thus accounting for the intermittent widespread deposition of organic rich strata during maximum transgression and depth of the greenhorn sea the lateral association of voluminous deltaic deposits with dee water black shales in other elongate or restricted marine basins may have causes similar to those envisioned for the hartland shale and bridge creek limestone members

the assessment of ree patterns and 143nd 144nd ratios in fish remains abstract the ree content and isotopic composition of sr and nd have been determined in fish teeth ranging in age from the trias to the present and from various localities mostly around the atlantic these measurements have been carried out on selachian and teleost remains from the same locality in togo and show no appreciable difference which suggests with the help of a mass balance calculation of the ce anomaly that diagenetic effects are not responsible for the ree enrichment of biogenic phosphates one group of fossil teeth has about 3 times the ree abundances of shale and a shale normalized pattern with a minimum at sm it is thought to reflect deposition in the open sea environment a second group has ree concentration about 10 times higher than the first group with either a regular light ree enrichment or more frequently a maximum in the middle ree both being probably indicative of deposition in estuarine or near shore conditions the shape of the ree spectra and the size of the ce anomaly can be used semi quantitatively to determine the depth of deposition the results presented here on late cretaceous eocene fish teeth samples from morocco reflect an increasing influx of deep waters with a lowla yb ratio and strong negative ce anomaly which agrees well with the evolution of sediment chemistry and microfauna associations in contrast nd is typical of the water mass in which the fish debris decayed examples of nearly isolated basins identified with nd isotopes include the south atlantic prior to the lutetian nd 13 5 the miocene persian gulf nd 3 1 and bolivia during the late cretaceous nd 12 8 togo and guinea bissau results suggest that in the south atlantic the meridional oceanic circulation had not started before 45 ma ago combination of ree and nd data suggests that the assignment of jurassic cretaceous samples measured so far to open sea water masses is still ambiguous

the inorganic geochemistry of cretaceous black shales dsdp leg 41 in comparison to modern upwelling sediments from the gulf of california

upper cenomanian lower turonian sea level rise and its consequences on the adriatic dinaric carbonate platform the adriatic carbonate platform existed throughout most of the mesozoic as an isolated intraoceanic carbonate platform it is characterized by what has been traditionally labelled a continuous shallow marine carbonate sedimentation without terrigenous influences however global sea level changes left unequivocal imprints in the continuous carbonate record thus proving that the carbonate platform sensitively responded to sea level fluctuations this paper focuses on the relatively short cenomanian turonian drowning event which temporarily submerged the platform below the euphotic zone and which is related here to the well known global cenomanian turonian sea level highstand this drowning episode is characterized by the abrupt disappearance of numerous shallow water benthic invertebrate taxa and by an abundant occurrence of planktonic organisms including calcispheres and primitive planktonic foraminifera near the middle of the turonian the platform regime was re established correlating with the global fall in sea level the situation is different only at the south west margin of the platform where pelagic sedimentation initiated near the end of the cenomanian continues into the santonian and probably marks the adriatic trough the drowning began earlier in the middle cenomanian in those areas nearer to the north east margin of the platform the area of what is today central croatia and then progressed gradually towards the more interior areas of the platform the middle dalmatian islands which were drowned near the end of the cenomanian

multivariate indications between environment and ground water recharge in a sedimentary drainage basin in northwestern china abstract a paucity of studies on the interaction between environment and ground water recharge severely restricts the ability of people to assess future water resources under changing environment in this study an effort to explore the relationship between the arid environment and ground water recharge was carried out using multivariate statistical techniques in a sedimentary drainage basin the jungar in northwestern china hierarchical cluster analysis hca and principal components analysis pca were performed based on hydrogeochemical data to assess the ground water recharge and its governing factors observation of the hca and pca analytical results revealed a division of seven clusters c1 to c7 and three principal components pc1 to pc3 which explained 59 6 16 6 and 10 9 of the variance respectively and thus accounted for the majority of the total variance in the original dataset based on these q mode hca clusters and r mode pac scores dominant environmental processes influencing recharge regimes were identified i e geogenic geomorphoclimatic and anthropogenic which separated the recharge regimes into four zones zone i to zone iv zones i and ii c4 c1 were associated to elevated hydroclimate degree coupled to low salinity zone iii c2 c3 was associated to moderately elevated salinity and evidently elevated contamination but coupled to low hydroclimate degree zone iv c5 c6 c7 was associated mainly to elevated salinity coupled to low or inverse hydroclimate degree it revealed that the geogenic processes are more significant 60 than the geomorphoclimatic 17 and anthropogenic 11 processes as a result the overall recharge process is rather heterogeneous and is strongly environment dominated in the jungar drainage system compared with other watersheds in arid environment a distinctive feature of the jungar waters is that they are affected by a combination of natural and non natural events rather than following a steady and continuous geological evolution these will continue to influence the recharge regime of the jungar for a long time due to its steady tectonics and arid climate however changing rainfall but not snow is becoming the key factor driving changes in ground water resources in this drainage system as results of the decades of warming and humidification in northwestern china

organic rich sedimentation at the cenomanian turonian boundary in oceanic and coastal basins in the north atlantic and tethys one of the most striking results of the deep sea drilling project is the proof that organic rich sediments have a widespread geographical distribution during the period from upper cenomanian to middle turonian such sediments were drilled at north atlantic dsdp sites 105 135 137 138 367 398 551 603 they are also present from outcrops or oil wells on the shelf of the african continental margin senegal tarfaya and agadir basins in the tethys former alboran block southern spain algeria tunisia and umbrian apennines italy and in the north sea although these sediments have different lithologies and depositional environments from shelf areas to the deep sea their study mainly based on organic geochemistry with additional data on sedimentology biostratigraphy and palaeo bathymetry suggests that a unique pulse of organogenic accumulation characterizes the cenomanian turonian boundary event ctbe the content and type of organic matter are related to the depositional environment and organic preservation the organogenic accumulation is distributed according to various trends off the african continental margin the organic content increases from onshore areas to the shelf casamance area and moreover increases also in deep sea areas with a gradual transition from terrestrial type iii to marine type ii the best preservation of the organic matter being in the deepest areas i e site 367 off the american continental margin site 603 shows the same toc and type of organic matter as at site 105 the ctbe is also well recorded in the northern part of the atlantic celtic margin north sea by a drastic lithological change black shales within chalks but the type of organic matter is mainly terrestrial in the tethyan area the organic matter is of marine origin and well preserved results are compared with those of pratt 1984 from the western interior basin of the usa different hypotheses to explain this synchronous widespread accumulation of organic matter are discussed 1986 the geological society

denitrification in the recharge area and discharge area of a transient agricultural nitrate plume in a glacial outwash sand aquifer minnesota 1 recharge rates of nitrate no3 to groundwater beneath agricultural land commonly are greater than discharge rates of no3 in nearby streams but local controls of no3 distribution in the subsurface generally are poorly known groundwater dating cfc 3h was combined with chemical ions and gases and stable isotope n s and c analyses to resolve the effects of land use changes flow patterns and water aquifer reactions on the distributions of o2 no3 so4 and other constituents in a two dimensional vertical section leading from upland cultivated fields to a riparian wetland and stream in a glacial outwash sand aquifer near princeton minnesota within this section a plume of oxic no3 rich groundwater was present at shallow depths beneath the fields and part of the wetland but terminated before reaching the stream or the wetland surface groundwater dating and hydraulic measurements indicate travel times in the local flow system of 0 to 40 years with stratified recharge beneath the fields downward diversion of the shallow no3 bearing plume by semiconfining organic rich valley filling sediments under the wetland and upward discharge across the valley and stream bottom the concentrations and 15n values of no3 and n2 indicate that the no3 plume section was bounded in three directions by a curvilinear zone of active denitrification that limited its progress however when recalculated to remove the effects of denitrification the data also indicate changes in both the concentrations and 15n values of no3 that was recharged in the past isotope data and mass balance calculations indicate that fes2 and other ferrous fe phases were the major electron donors for denitrification in at least two settings 1 within the glacial fluvial aquifer sediments beneath the recharge and discharge areas and 2 along the bottom of the valley filling sediments in the discharge area combined results indicate that the shape and progress of the oxic no3 plume termination were controlled by a combination of 1 historical and spatial variations in land use practices 2 contrast in groundwater flow patterns between the agricultural recharge area and riparian wetland discharge area and 3 distribution and abundance of electron donors in both the sand aquifer and valley filling sediments the data are consistent with slow migration of redox zones through the aquifer in response to recharging oxic groundwater during holocene time then an order of magnitude increase in the flux of electron acceptors as a result of agricultural no3 contamination in the late twentieth century to which the redox zone configuration still may be adjusting the importance of denitrification for no3 movement through formerly glaciated terrains should depend on the source areas and depositional environments of the glacial sediments as well as geomorphology and recent stream valley sediment history

complex holocene lunette dune development south africa implications for paleoclimate and models of pan development in arid regions closed depressions pan or playa basins are very common landscape features in arid or formerly arid regions many have associated downwind dune assemblages lunettes that have been explained in terms of deflation of sediments from the basin these widespread features have also been used as proxies of late quaternary rainfall and atmospheric circulation change we use a detailed program of optically stimulated luminescence dating at witpan south africa to show that lunette construction may be rapid and spatially complex this study presents 33 ages from 9 sample sites on the dune that show how accumulation of the present dune largely occurred over the past 2 k y but with marked sectoral variability in accumulation rates and timing variability is attributed largely to local sediment supply factors geochemical analysis shows that primary deflation from the pan has not contributed significantly to the construction of much of the current lunette most sand is derived from recycling of older lunette sediments preserved today at only a few locations and from neighboring linear dunes these findings if representative of lunettes in other localities have marked implications for the types of paleoclimatic information that these features may yield

hydrogeology and geochemistry of the ogallala aquifer southern high plains the ogallala aquifer which underlies the southern high plains consists of saturated sediments of the ogallala formation neogene that are deposited mainly as a set of humid type alluvial fans derived from the rocky mountains the ogallala aquifer the main source of water for the high plains of texas and new mexico has been severely depleted by extensive pumpage the hydrology and geochemistry of the aquifer are controlled by the surface topography of the underlying formations and by the thickness and permeability of the alluvial fan deposits axes of three major alluvial fans trend from northwest to southeast the fans have increased thickness and permeability compared with interfan areas flow lines follow the orientation of the alluvial fans along these major axes the saturated section is thick and the chemical composition is relatively constant ca hco3 to mixed cation hco3 water depleted in 18o d and tritium external effects on the chemical composition are less pronounced the aquifer is thinner and less permeable in areas between major fan axes and along the caprock escarpment in these areas groundwater can discharge from aquifers in the cretaceous triassic and permian formations into the ogallala formation cross formational movement of water and low permeabilities in the ogallala formation result in varying hydrochemical facies and in isotopic compositions that differ from those of the major depositional areas areas where upward cross formational flow occurs are evident by the presence of permeable contacts between the ogallala and the underlying formations water level head differences and chemical and isotopic similarities secondary factors that locally affect the chemical composition of ogallala formation groundwater include contamination from evaporating saline lakes agricultural chemicals and fertilizers and oil field brines impact of chemicals and brines may increase in the future because much of these contaminants may still be moving through the unsaturated zone toward the water table

field study of spatial variability in unsaturated flow beneath and adjacent to playas we quantified unsaturated flow beneath playa and adjacent interplaya settings at a site in the southern high plains united states to resolve issues related to where and how water moves through the unsaturated zone this is the first study in which the data density 39 boreholes and the variety of techniques used physical chemical and isotopic were sufficient to quantify spatial variability in unsaturated flow water contents water potentials and tritium eoneentrations were much higher and chloride eoneentrations were much lower beneath playas than in interplaya settings which indicated that playas focus recharge these results refute previous hypotheses that playas act as evaporation pans or that recharge is restricted to the annular region around playas water fluxes estimated from environmental tracers ranged from 60 to 120 mm yr 1 beneath playas and were 0 1 mm yr 1 during the past 2000 5000 years beneath natural interplaya areas not subjected to ponding to evaluate the apparent inconsistency between high recharge rates and thick clay layers beneath playas we applied bromide and fd c blue dye to evaluate flow processes these applied tracer experiments showed preferential flow along roots and desiccation cracks through structured clays in the shallow subsurface in playas

groundwater chemistry patterns in the phreatic aquifer of the central belgian coastal plain the holocene geological evolution of the belgian coastal plain is dominated by a transgression of the north sea silting up of the coastal plain and human intervention impoldering this has led to a typical pattern in groundwater quality which is discussed here for the central part of the coastal plain therefore a database with available groundwater samples is composed water type according to the stuyfzand classification is determined and different hydrosomes and their hydrochemical facies are identified based on this the origin and evolution of the water types is explained using piper plots and geochemical calculations with phreeqc before the impoldering salinising and freshening conditions alternated with a general salinisation of the aquifer after about 3400 bp this results in a dominance of brackish and salt nacl subtypes which are still found in the deeper part of the aquifer the subsequent impoldering resulted in an major freshening of the aquifer leading to nahco3 mghco3 and cahco3 subtypes overall mixing cation exchange carbonate mineral dissolution and oxidation of organic matter are identified as the major processes determining the general water quality the close link between geological evolution water quality and what is still observable today is illustrated with this example of the belgian coastal plain

cyclic fluctuations of anoxia during cretaceous time in the south atlantic ocean abstract the holes of the dsdp ipod program in the south atlantic ocean document two major anoxic events during oxfordian to middle albian times and secondly from late cenomanian to santonian times the black shales formed during these two anoxic events differ in their rhythmicity and origin during lower cretaceous time the anoxic conditions resulted from the confined euxinic nature of the basins the rhythmicity of these black shales probably does not result from a global phenomenon climatic or tectono eustatic but from local conditions resulting from the slender dimensions of the young ocean basin s the diversity and the diachroneity of the deposits from the south to the north precisely reflect the dynamics of the oceanic spreading during upper cretaceous time the anoxic conditions fluctuated in relation to a mid water oxygen minimum zone the rhythmicity of black shale deposition seems to result from a global phenomenon because of the widespread occurrence of the event in the south atlantic ocean the cyclic fluctuations of anoxia were due to cyclic variations in the depth of the mid water oxygen minimum zone there is no simple process to explain such rhythmicity it probably results from the interplay of the three main variables which characterize the oceans at the time of the cenomanian turonian boundary the increased rate of sea floor spreading high sea levels and low water circulation

late quaternary sedimentology and geochronology of small playas on the southern high plains texas and new mexico u s a abstract playas are small circular basins forming a ubiquitous component of the southern high plains landscape they are filled with carbonaceous mud deposited since the terminal pleistocene the stratigraphy and geochronology of 30 playas was investigated to better understand the paleoenvironmental record of basin filling at the base of the fill in some playas is a well sorted eolian sand dated between 13 000 and 11 000 14c yr bp the beginning of mud deposition representing aggradation of eolian dust on a moist vegetated playa floor was largely between 12 000 and 10 500 14c yr bp playa filling slowed 9000 to 4000 14c yr bp probably due to dry conditions increased 4000 to 2000 14c yr bp then slowed again eolian sand and loam likely representing regional aridity accumulated in some basins episodically just prior to 10 700 14c yr bp between 8600 and 4700 14c yr bp and at 1300 14c yr bp stable c isotopes from one basin indicate that the playa was inundated only seasonally throughout the record beginning 11 500 14c yr bp the phytolith record in that basin indicates an abrupt shift toward cooling 11 400 to 11 200 14c yr bp and then increasing importance of xeric adapted c4 grasses through the holocene

geochemical and lithium isotope tracking of dissolved solid sources in permian basin carbonate reservoir and overlying aquifer waters at an enhanced oil recovery site northwest texas usa abstract geochemistry and lithium isotope compositions 7li of permian basin produced water and potable groundwater from overlying aquifers at an enhanced oil recovery eor site in gaines county northwest texas are used to evaluate the effects of brine groundwater rock interactions identify sources of dissolved solids and characterize fluid flow and mixing processes 7li values per mil deviations from the lsvec standard 7li 6li ratio for produced water from dolostones of the san andres formation ranged from 10 9 to 15 6 and fall within the range of formation waters from other sandstone carbonate reservoir rocks in north america europe and the middle east these differ from produced waters from hydraulically fractured shales from the u s appalachian basin including the marcellus shale which tend to have lower 7li values and higher li cl possibly indicating greater interaction with a terrigenous component the san andres produced water chemistry and li isotope ratios are consistent with neogene meteoric water interacting with marine and continentally derived evaporites e g portions of the guadalupian salado formation as well as other terrestrial sources along the flow path groundwater from the triassic dockum group santa rosa aquifer 7li range of 20 6 to 23 5 is isotopically distinct from waters from the overlying ogallala formation 10 6 to 16 5 and the deeper san andres formation indicative of hydrologic isolation from both meteoric recharge and from deeper brines in the field area in addition to tracking groundwater brine mixing and water rock interaction temporal changes in the 7li composition of deep groundwater in the study area has potential use in the early detection of upward or injection induced brine migration prior to its incursion into the sensitive overlying ogallala aquifer

a euxinic southern north atlantic ocean during the cenomanian turonian oceanic anoxic event abstract during mid cretaceous times large amounts of organic carbon corg became sequestered in black shales possibly due to oceanic anoxic events characterized by the development of an extended oxygen minimum zone omz here we provide the first direct evidence for an open ocean omz in the cenomanian turonian c t southern north atlantic and in fact show that the base of the photic zone was euxinic as revealed by molecular fossils from photosynthetic green sulfur bacteria in c t black shales this together with evidence for bottom water anoxia and accumulation of redox sensitive trace metals and hydrogen rich organic matter indicates a continuously euxinic water column concurrent with the high corg accumulation rates which are 15 150 times greater in the southern than in the northern north atlantic and the low biological productivity this suggests that preservation controlled the accumulation of corg in c t black shales

separation and location of microseism sources 1 microseisms are ground vibrations caused largely by ocean gravity waves multiple spatially separate noise sources may be coincidentally active a method for source separation and individual wavefield retrieval of microseisms using a single pair of seismic stations is introduced and a method of back azimuth estimation assuming rayleigh wave arrivals of microseisms is described these methods are combined to separate and locate sources of microseisms in a synthetic model and then applied to field microseismic recordings from ireland in the northeast atlantic it is shown that source separation is an important step prior to location for both accurate microseism locations and microseisms wavefield studies

recharge into southern high plains aquifer possible mechanisms unresolved questions the high plains aquifer in the southern high plains texas and new mexico consisting of tertiary cretaceous and triassic formations has traditionally been considered to be recharged by its uppermost water bearing unit the tertiary ogallala aquifer this article provides hydrologic chemical and isotopic evidence that in the southern high plains 1 cretaceous rocks actually contain independent recharge sources 2 triassic rocks cannot currently be recharged by the ogallala aquifer in significant quantities and 3 in places both cretaceous and triassic aquifers recharge the overlying ogallala aquifer on the basis of chemical and isotopic data playa lakes seem to act as the predominant recharge source of the ogallala aquifer suggesting recharge rates greater than 30 mm yr as opposed to the much lower rates reported by others the cretaceous aquifers are being recharged by cross formational flow from the ogallala aquifer but also from overlying quaternary sands and the underlying triassic aquifer in eastern new mexico current recharge into the triassic aquifer may be insignificant

cenomanian turonian carbonate and organic carbon isotope records biostratigraphy and provenance of a key section in ne sicily italy palaeoceanographic and palaeogeographic implications abstract in eastern sicily a series of highly organic rich black shales occur as exotic blocks 100 m across floating in tectonized sediments argille varicolori unit containing olistoliths of cretaceous palaeogene age a 19 metre section through one of these blocks near the town of novara di sicilia includes cyclically bedded black shales marlstones and claystones which have been dated using planktonic foraminiferal and nannofossil biostratigraphy on this basis the section is assigned to the latest cenomanian and clearly represents a manifestation of the oceanic anoxic event characteristic of that interval total organic carbon values range up to 23 and the relatively high hydrogen indices record the presence of marine organic matter of low thermal maturity high resolution carbonate and organic carbon isotope curves are comparable with those recorded elsewhere in indicating a significant positive excursion and confirm that in the novara di sicilia section the black shales are latest cenomanian in age by comparison with cenomanian turonian black shales exposed elsewhere in italy calabianca section western sicily livello bonarelli bottaccione gorge gubbio marche umbria the section of novara di sicilia is different in being more stratigraphically expanded however this section from eastern sicily does resemble extremely closely coeval sediments cropping out in tunisia and morocco this association is taken as evidence that the argille varicolori unit includes elements that were initially deposited on the north african shelf during cretaceous time

identification of sulfate sources in groundwater using isotope analysis and modeling of flood irrigation with waters of different quality in the jinghuiqu district of china the main objective of this study was to identify the main sources and processes that control so42 groundwater concentrations in the jinghuiqu irrigation district of china using isotope analysis lysimeter irrigation experiments and numerical modeling were used to assess the impact of long term irrigation practices on sulfate transport when different sources of irrigation water were used so42 concentrations in the groundwater of the entire irrigation area increased significantly from the years 1990 a mean value was 4 8 mmol l 1 to 2009 a mean value was 9 84 mmol l 1 the 34s so42 values ranging from 5 27 to 10 69 indicated that sulfates in groundwater were initially predominantly derived from dissolution of minerals however no soluble sulfate minerals gypsum and or mirabilite were detected after 1990 to better understand this seeming anomaly water content and so42 data were collected before and after the field irrigation experiment and analyzed using the hydrus 1d and hp1 software packages the experimental data were also used to assess sulfate leaching when different sources of irrigation water were used under current irrigation practices the dissolved sulfate concentrations in the soil profile increased significantly when groundwater was used for infiltration compared to the use of surface water irrigation water sources had a great impact on the increase of sulfate concentrations in the shallow groundwater especially when groundwater with elevated concentrations was used for irrigation

a study of the soluble and insoluble organic matter from the livello bonarelli a cretaceous black shale deposit in the central apennines italy abstract pyrolysis mass spectrometry of extracted sediments from the livello bonarelli a thinly laminated carbonate poor sedimentary unit at the cenomanian turonian boundary indicates significant differences between the samples microscopic investigations and pyrolysis gas chromatography show a main contribution from marine organic matter for all samples the composition of the extractable hydrocarbons becomes more complex with increasing organic carbon content of the sediments indicating increasing anoxicity in the environment of sedimentation organic geochemical analyses combined with sedimentological and paleontological data show that the livello bonarelli could have been deposited in a paleoenvironment similar to that recently proposed for the pleistocene mediterranean sapropels with an intermittent influx of fresh water leading to stagnation and a high productivity of marine organic matter caused by the transported nutrients

deformation structures and an alteration zone linked to deposition of volcanogenic sulphate in an ancient playa oligocene of nebraska usa historic sulphur rich volcanic eruptions have altered global climate for as much as five years and much larger events are known from the geologic record at scotts bluff nebraska early oligocene strata of the lower arikaree group contain a tephra bed with abundant calcite pseudomorphs after gypsum previous work has shown sulphate from the pseudomorphs in this tephra bears a high 17 o anomaly indicative of oxidation of sulphur gases by ozone or hydrogen peroxide in the atmosphere possible sources of the tephra were caldera eruptions at about 28 ma in the san juan volcanic field of southwestern colorado 500 km sw of the study site and the eastern great basin 1000 km wsw the present sedimentological study shows that tephra and volcanogenic sulphate were deposited and preserved within a small surfacedischarging playa that developed on the irregular upper surface of aeolian siltstones of the subjacent white river group sulphate solutions including perhaps sulphuric acid percolated downward within the vadose zone dissolving early formed smectite cement within underlying volcaniclastic sandstones reddening these rocks along an irregular alteration front preserved fine scale stratification within the sandstones precludes the possibility that reddening took place during pedogenesis displacive growth of gypsum at the playa centre folded tephra beds and forced tephra into underlying sandstones forming elongate cones the large mass fraction of gypsum now replaced by calcite in the playa sediments suggests a huge long distance delivery of sulphate aerosols some of the sulphate and tephra may have come from the same eruption or the fine grained tephra may simply have aided preservation of dry fog sulphate derived from an unrelated effusive eruption of lava

middle holocene drought on the southern high plains abstract the climate of the southern high plains during the middle holocene is indicated by data from a variety of sources stratigraphic geomorphic and pedologic research at six localities in draws several dune sites and one playa lake basin show that widespread eolian erosion and sedimentation began in some areas by 9000 yr b p and culminated 6000 4500 yr b p probably because of warmer drier conditions that reduced the vegetative cover archaeological investigations at three sites provide evidence for the excavation of wells at this time apparently because of a declining water table studies of a few vertebrate and invertebrate faunas also indicate warming and drying in the middle holocene climate models and very limited isotopic data from bison bone suggest that summers in the middle holocene were warmer than present with reduced effective precipitation all lines of evidence indicate that the southern high plains was subjected to prolonged drought in the middle holocene with a maximum between 6500 and 4500 yr b p conforming climatically and chronologically to the altithermal

phosphorus cycling from the margin to abyssal depths in the proto atlantic during oceanic anoxic event 2 abstract phosphorus p burial during the cenomanian turonian oceanic anoxic event oae 2 93 55 ma was studied using sediment records from four sites in the proto atlantic ocean the sites represent a variety of depositional settings from the continental margin and slope to the abyssal plain strong links between changing marine conditions during oae 2 and p cycling were observed in black shale sections on the continental margin and slope sedimentary p contents and p mars increased around the onset of oae 2 which may reflect enhanced productivity and p burial partly in the form of biogenic apatite fish debris during the main stage of oae 2 phosphorus was efficiently regenerated from the sediment resulting in p depleted sediments and high organic c corg total p ratios the increased availability of dissolved p may have helped to sustain high productivity during oae 2 the termination of oae 2 was associated with a strong recovery of p burial efficiency in the sediment sedimentary records from the two deep sites do not reveal such close links between different stages of oae 2 and the characteristics of p cycling here oae 2 was a period with maximum deposition of relatively thin black shale intervals that alternate with more oxic deep sea sediments the black shale layers record enhanced p regeneration from organic matter and in some cases p enrichment relative to the oxic sediments detailed chemical p fractionation was performed on sediment from all sites but the results were found to mostly reflect diagenesis and sample handling artifacts in these ancient sediments total p concentrations and the corg total p ratio appear to be the most robust indicators of p cycling and regeneration

ocean wide stagnation episode in the late cretaceous in this paper we report that marine sediment locations spread over a wide area contain evidence of an anoxic interval during the mid cretaceous here called the cenomanian turonian black shale horizon ctbsh the occurrence of laminated carbonaceous shales with marine organic matter in an unoxidized state implies deposition and early diagenesis in anaerobic environments the stratigraphic record above and below the ctbsh in environments as different as the deep north atlantic ocean and marginal and epicontinental seas over enormous areas in north america north africa and northwestern europe is characterized by a stratigraphic gap a disconformity or a continuous but strongly condensed stratigraphic section the anoxic layer coincides in time with the maximum extension of a worldwide marine transgression of eustatic origin recorded on continental margins1 as well as on various cratons2 no simple model has yet been found to explain the occurrence of the ctbsh in such a wide range of depth and palaeoenvironmental conditions

after the deluge mediterranean stagnation and sapropel formation in an east mediterranean marine core the upper sapropel begins soon after the start of a global event a very heavy precipitation which occurred in the equatorial latitudes during the late glacial early holocene this heavy precipitation in africa channelled by the nile river across 35 of latitude produced a low salinity surface layer in the east mediterranean in this confined basin with high bottom salinity the steep salinity gradient stratified the water column the stagnant bottom waters triggered the sapropel formation cretaceous sapropels in the tropical oceans may result from the same chain of events in warm humid climates with contrasting wet and dry seasonal rhythm

geologic and hydrologic controls on the movement of water through a thick heterogeneous unsaturated zone underlying an intermittent stream in the western mojave desert southern california 1 a two dimensional axially symmetric unsaturated flow model was developed to test hypotheses about geologic and hydrologic controls on the movement of water through the thick heterogeneous unsaturated zone underlying oro grande wash in the mojave desert california heterogeneity within the unsaturated zone was simulated with multiple realizations of subsurface geology estimated on the basis of transition probability markov chain statistics model results show lateral spreading of water away from the wash was best approximated by realizations that include thin horizontally extensive clay layers that impede the downward movement of water there was a wide range in model responses for these realizations and the movement of water through unsaturated zones containing thin horizontally extensive clay layers may be more difficult to predict than water movement through unsaturated zones where clay layers are less extensive for realizations having less extensive clay layers the range of model responses decreased with time and model results became increasingly similar as water encountered larger volumes of material

the cenomanian turonian oceanic anoxic event ii palaeoceanographic controls on organic matter production and preservation correlation of the 13c spike with the well dated occurrences of strata rich in organic carbon detailed in schlanger et al this volume indicates that a global episode of intense organic carbon orgc burial took place during the latest cenomanian earliest turonian oceanic anoxic event oae a plenus through i labiatus macrofossil zones and upper r cushmani trz through w archecretacea prz foraminiferal zones over a period of no more than 1 million years m y the shape of the 13c curve indicates that rates of orgc burial gradually increased in the early part of the late cenomanian increased more rapidly in the later cenomanian and levelled off at peak values in latest cenomanian early turonian time during the maximum rate of orgc burial the 13c values decreased nearly to pre late cenomanian levels in the early to middle turonian the decrease in 13c reflects decreasing rates of orgc burial following the cenomanian turonian oceanic anoxic event as well as the probable oxidation and return of significant amounts of orgc to the oceans following regression and re oxygenation of much of the deeper water masses in contact with the seafloor

euxinia and primary production in late cretaceous eastern equatorial atlantic surface waters fostered orbitally driven formation of marine black shales 1 oceanic anoxic events oae in the cretaceous represent major perturbations in the global climate and ocean system characterized by widespread deposition of organic carbon in the ocean the causes and effects of these events are poorly constrained mainly because of the lack of high resolution marine records here we report the distribution of molecular markers from a millennial scale record of coniacian santonian black shale oae 3 from ocean drilling program site 959 in the deep ivorian basin in the eastern equatorial atlantic highly branched isoprenoids and alkenone derived organic compounds indicate that diatoms and calcareous nanoplankton were important primary producers changes in redox sensitive trace metal accumulation and biomarkers of green sulfur bacteria provide evidence for extreme variations in redox conditions with intervals of lower photic zone euxinia pze accordingly oxygen in the coniacian santonian tropical atlantic was absent as during the cenomanian turonian boundary oae 2 but over more restricted geographic area and more limited time intervals we hypothesize that pze was a common phenomenon typical in large areas of tropical continental margins these conditions fostered sequestration of atmospheric co2 and thus helped cause the positive excursion in 13c of carbonate documented in higher latitude marine records

the nature distribution and formation of pans in arid zones abstract pans closed depressions are a widespread feature of many of the world s drylands by using literature survey air photographs topographic maps orbital photographs and imagery combined with field work it is possible to describe the major areas where these features occur their distribution is controlled to a great extent by the availability of susceptible surfaces they also develop in certain particular environmental settings palaeolacustrine basins palaeodrainages interdunes and on coastal plains many of the pans have a distinctive morphology while on their lee sides they may have lunette dunes many processes combine to create and maintain pans and these can be considered in a general model which has certain key elements the first of these is that the area should not be one where fluvial processes are fully integrated it should also not be one where aeolian accumulation is such as to infill any irregularities in the land s surface if these two predisposing conditions are fulfilled then under dryland conditions if susceptible surfaces are present there are various circumstances that may lead to hollow development and enlargement although in some cases such processes as solution suffosion and animal activities may play a role we believe that the predominant reason why pans have the characteristics that they do including their shapes lunettes alignments etc is that they result from the operation of the twin processes of salt weathering and aeolian deflation

long term 1960 2010 trends in groundwater contamination and salinization in the ogallala aquifer in texas summary although numerous studies have expounded on depletion of the ogallala aquifer very few researchers have studied groundwater quality therein which relates to the usability of available groundwater resources the objective of this study was to elucidate regional trends in groundwater quality and salinization in the ogallala aquifer underlying 49 counties and two groundwater management areas gma 1 and 2 in texas on a decadal scale between 1960 and 2010 contrasting groundwater quality distinguished gma 1 northern ogallala from gma 2 southern ogallala and shallow wells depth 50 m wells the gma 2 was characterized by pronounced groundwater nitrate no 3 contamination accompanied by elevated levels of sulfate so 4 2 chloride cl and salinity tds marked by an abundance of mixed cation so 4 cl and na cl facies in contrast ca mg hco 3 and ca hco 3 facies prevailed in gma 1 with substantially lower salinization so 4 2 cl and no 3 contamination in shallow wells more abundant in gma 2 about 80 and 32 of observations exceeded the united state environmental protection agency s secondary maximum contaminant level smcl 500 mg l 1 for total dissolved solids tds and mcl 44 mg l 1 for no 3 respectively in the 2000s 2000 2010 with progressive increases in both parameters since the 1960s 1960 1969 majority 60 of the shallow observations since the 1980s 1980 1989 have exceeded the natural background of 11 mg l 1 of no 3 indicating anthropogenic sources the no 3 contamination was more apparent in domestic wells indicating substantial human health risk groundwater salinization in this aquifer resulted from a combination of natural e g upwelling of highly mineralized groundwater from the underlying formations seepage from playas and saline plumes and evaporative enrichment and anthropogenic processes irrigated agriculture and hydrocarbon exploration activities natural processes were largely aggravated by anthropogenic practices such as lowering of hydraulic heads in the ogallala aquifer due to prolonged irrigational pumping inducing cross formational flow from underlying highly mineralized older formations edwards trinity high plains which led to groundwater mixing between the formations and rise in salinity levels in the ogallala aquifer over time

controls on the regional scale salinization of the ogallala aquifer southern high plains texas usa an extensive saline plume 250 km 2 within the regionally important unconfined aquifer in the neogene ogallala formation overlies the panhandle oil and gas field in the southern high plains texas usa relative to upgradient ogallala water the plume waters have d 18 o 6 7 to 8 8 and d d 42 to 88 values that tend to be depleted and have higher cl 150 mg l and so4 75 mg l concentrations various end member mixing models suggest that the plume composition reflects the presence of paleowaters recharged during middle to late wisconsinan time rather than salinization associated with petroleum production paleowaters probably mixed with salt dissolution zone waters from the underlying upper permian formations before discharging upward into the ogallala formation cross formational discharge is controlled primarily by the geometry of the underlying units as influenced by the amarillo uplift pinch out of the laterally adjoining confined aquifer in the triassic dockum group variations in the saturated thickness of the ogallala aquifer and the presence of potential pathways related to salt dissolution 2000 elsevier science ltd all rights reserved

late quaternary environmental reconstructions of playa lunette system evolution on the central high plains of kansas united states playas are small ephemeral wetlands found throughout semiarid and arid regions around the world lunettes are dunes that form downwind of some large playas two playa lunette systems on the high plains were investigated to reconstruct paleoenvironments during playa lunette system evolution both playa lunette systems are composed of sediment spanning 40 k y with earliest deposits accumulating during at least marine isotope stage mis 3 and possibly starting as early as mis 5 the gilman canyon formation pedocomplex dating between 42 and 28 ka dominates this period and is ubiquitous throughout the playa lunette systems climate during mis 3 was similar to modern with warm temperatures low effective moisture and playa floors exposed long enough to allow pedogenesis during mis 2 climate was relatively cool with higher effective precipitation and playas were inundated for longer periods the regionally expressed brady soil of the pleistocene holocene transition caps these deposits and dates between 11 8 and 9 4 ka during the pleistocene holocene transition climate warmed yet moisture availability remained relatively high several distinct shifts in 13 c identify rapid climate changes associated with the bolling allerod younger dryas chronosequence warming continued into the holocene though moisture availability was highly variable holocene soils are common and date between 8 3 and 3 6 ka playa lunette system stratigraphy represents a continuum of the upland loess sequence though deposits are altered by playa hydrology geomorphic processes alternated between dissolution and fluvial eolian driven processes as climate changed and playas developed due to the aggradational environment and sensitivity of these systems high resolution records of environmental change throughout their evolution are preserved

carbon and oxygen isotope stratigraphy of the english chalk and italian scaglia and its palaeoclimatic significance a detailed carbon and oxygen isotope stratigraphy has been generated from upper cretaceous coastal chalk sections in southern england east kent culver cliff isle of wight eastbourne and seaford head sussex norfolk coast and the british geological survey bgs trunch borehole norfolk data are also presented from a section through the scaglia facies exposed near gubbio italian apennines wherever possible the sampling interval has been one metre or less both the chalk and scaglia carbon isotopic curves show minor positive excursions in the mid cenomanian mid and high turonian basal coniacian and highest santonian lowest campanian there is a negative excursion high in the campanian in chalk sections that span that interval the well documented cenomanian turonian boundary spike is also well displayed as is a broad positive excursion centred on the upper coniacian a number of these positive excursions correlate with records of organic carbon rich deposition in the atlantic ocean and elsewhere the remarkable similarity in the carbon isotope curves from england and italy enables cross referencing of macrofossil and microfossil zones and pinpoints considerable discrepancy in the relative positions of the turonian coniacian and santonian stages the oxygen isotope values of the various chalk sections although showing different absolute values that are presumably diagenesis dependent show nonetheless a consistent trend the east kent section which is very poorly lithified indicates a warming up to the cenomanian turonian boundary interval then cooling thereafter regional organic carbon burial documented for this period is credited with causing drawdown of co 2 and initiating climatic deterioration inverse greenhouse effect data from other parts of the world are consistent with the hypothesis that the cenomanian turonian temperature optimum was a global phenomenon and that this interval represents a major turning point in the climatic history of the earth

lithostratigraphy and geochronology of fills in small playa basins on the southern high plains united states playa basins are small depressions typically 1 5 km 2 on the southern high plains of northwestern texas and eastern new mexico there are about 25 000 playas in the region they lie on the blackwater draw formation pleistocene a widespread eolian deposit and locally on the ogallala formation miocene pliocene understanding the lithostratigraphy and chronostratigraphy of the fill in the basins is important because it should 1 provide clues to the origin and evolution of playas which have been long debated 2 yield a paleoenvironmental record for the region and 3 aid in understanding the history and future of the regional aquifer because playas are the principal source of recharge data from 19 playa basins combined with published data from 4 other basins show that the basin fill is composed of six distinctive facies 1 lacustrine mud 2 lacustrine carbonate 3 lacustrine delta deposits 4 eolian sand and silt 5 eolian loam and 6 accretionary eolian deposits blackwater draw formation mud deposited under ponded conditions is the most common facies and is the surficial deposit on the floors of most playas often producing vertisols the carbonate was precipitated under lacustrine conditions and is another common facies and surface deposit delta deposits are common near the basin margins well sorted layers of eolian sand and silt and poorly sorted eolian loam occur locally above within or below the lacustrine deposits the modern basins in all study areas are locally or completely inset into the blackwater draw formation supporting the interpretation that the basins are at least in part erosional features in larger basins with thicker fills generally coincident with thicker blackwater draw formation the formation interfingers with the lacustrine fill dating is based on radiocarbon ages from the fill in 12 basins and from lunettes adjacent to 5 basins all dated basins were present at the end of the pleistocene and some were present in some form throughout the pleistocene lacustrine mud and other clastic deposits accumulated in the late quaternary and locally much earlier showing that at least some basins contained water throughout the time of human occupation of the region dating of eolian sediments supports other data indicative of aridity and wind deflation in the early and late holocene the lacustrine carbonate is late pleistocene or older and its paleoenvironmental significance is unknown these lithostratigraphic and chronostratigraphic relationships show that some basins have a prolonged history as depressions persisting in more or less the same location as the high plains surface aggraded by eolian addition blackwater draw formation throughout the pleistocene sizes of the basins varied through time as they were encroached upon by the blackwater draw formation enlarged by fluvial lake margin and eolian erosion were filled and reexposed or were buried some basins are newly formed on the high plains surface and have no apparent predecessors the only evidence for subsidence beneath the basins is gently warped fill in the basins on the northern margin of the region known to be affected by salt dissolution in paleozoic bedrock pedogenic carbonates typically are absent from or beneath the basin fill due to focused recharge through the basins playa basins probably have been a ubiquitous component of the high plains landscape through much of the quaternary

warm saline bottom water in the ancient ocean considerable isotopic evidence indicates that oceanic bottom water was much warmer in the geological past a simple convection model driven by multiple turbulent buoyant plumes and observations of present deep water formation have led to the development of a theory for the formation of warm saline bottom water it is suggested that changes in the size and configuration of marginal seas in net evaporation zones due to lithospheric plate motions and eustatic sea level change caused these seas to become sources of warm saline bottom water evidence from the palaeotemperature record and palaeogeography during the late cretaceous is used to reinforce the hypothesis climatic and chemical consequences of the formation of warm saline bottom water are discussed

earth motion caused by local atmospheric pressure changes summary observations have been made of the local atmospheric pressure field and the long period seismic noise fields both on the surface of the earth and in a mine at a depth of 183 metres the observations show that during windy intervals and in the period range 20 100 s there is a strong correlation between local atmospheric pressure changes and the noise recorded by a vertical seismograph located on the surface in contrast over the same range of periods there is no correlation between the seismic noise recorded in the mine and local atmospheric pressure changes except during the passage of acoustic waves it is shown that the noise in this pass band is not due to the buoyant response of the seismograph but is caused by the motion of the earth responding to atmospheric pressure changes

integrated depositional model for the cenomanian turonian organic rich strata in north africa abstract during the late cenomanian early turonian c t oceanic anoxic event oae2 organic rich strata was deposited in rift shelf basins and slopes across north africa and in deep sea basins of the adjacent oceans based on a review of published and unpublished information this paper documents the distribution and organic richness of c t strata across the whole region within a palaeogeographic framework and systematically analyses the conditions and processes which controlled their deposition previously the c t in north africa has been most intensively studied in southern morocco tarfaya and tunisia only little data is availabe for other parts of north africa namely algeria libya and egypt because distribution of c t corg strata there becomes more patchy a general decrease in peak organic richness and black shale thickness occurs from west to east partly as a result of upwelling along the moroccan atlantic coast and the absence of upwelling in the eastern mediterranean area furthermore in the confined central atlantic the oxygen minimum zone omz in many places reached down to the deep sea floor 3 4 km while the lower limit of the omz along the north african tethys was much shallower and underlain by oxic water masses as documented by high resolution biostratigraphic and chemostratigraphic data c t black shale deposition in most areas outside the upwelling zone are restricted to a strong eustatic latest cenomanian transgressive phase triggered by this sea level rise the omz impinged onto the north african continental shelf and the margins of intrashelf basins which mostly formed during the early cretaceous as halfgrabens important units containing c t organic rich strata in the region are the atlantic tarfaya black shales morocco western sahara black shales and phtanites in the moroccan and algerian atlas the bahloul fm in the se constantine basin and in northern and central tunisia the etel fm in the sirte basin the al hilal fm in cyrenaica libya the abu roash fm in the abu gharadig and fayium basins western desert egypt the daliyya fm along the ne sinai palestine isreal coast and the shueib fm in west central jordan

further evidence for the development of photic zone euxinic conditions during mesozoic oceanic anoxic events periods in earth history characterized by extensive organic carbon deposition so called oceanic anoxic events oaes are the subject of considerable scrutiny insight into the extent of anoxic conditions in the water column has been provided by the reported occurrence of derivatives of isorenieratene a carotenoid found only in green sulphur bacteria and thus indicative of photic zone euxinia i e a water column containing free h 2 s in north atlantic deep sea sediments deposited during the cenomanian turonian boundary oae2 bonarelli event in this study we have used the distributions of chlorophyll and bacteriochlorophyll degradation products maleimides 1 h pyrrole 2 5 diones and high molecular weight porphyrins to examine further the cenomanian turonian boundary oae2 as well as other oaes of the early toarcian posidonienschiefer event and early aptian selli event in particular methyl isobutyl me i bu maleimide on structural grounds appears to be diagnostic of green sulphur bacteria this compound occurs in five of seven examined marls that record the early toarcian oae marche umbria italy further expanding the geographical range of toarcian sediments where evidence for photic zone euxinic conditions has been found me i bu maleimide occurs in three of six black shales spanning the livello selli marche umbria italy the type locality for the aptian oae1a providing the first evidence for photic zone euxinic conditions during this event with respect to the cenomanian turonian oae maleimide evidence for photic zone euxinic conditions was found in all the north atlantic sites investigated including those characterized by relatively organic lean sediments several tethyan sites and one site off western australia these data indicate that euxinic conditions were common in the water column during mesozoic oceanic anoxic events

palaeoceanography saline water sinking ninety five million years ago ocean bottom waters were much warmer than at present some of this warmth could have come from the proto north atlantic s continental shelves after the balmy surface waters became increasingly salty through evaporation

hydrogeochemical processes involved in salt dissolution zones texas panhandle u s a permian evaporite deposits have been extensively dissolved beneath the perimeter of the southern high plains in the texas panhandle hydrologic and geochemical data were collected from six test wells to determine hydrogeochemical processes involved and the source and flow paths of ground water moving in salt dissolution zones geochemical similarities and hydraulic head relationships indicate that ground water dissolving halite and anhydrite moves downward from aquifers in post permian formations and follows flow paths influenced by topography holocene salt dissolution rates probably are lower than tertiary and pleistocene rates owing to regional changes in physiography and climate that probably decreased the amount of recharge to salt dissolution zones present as well as palaeohydrologic ground water velocities and salt dissolution rates are probably less beneath the southern high plains than in adjacent peripheral salt dissolution zones because of lower hydraulic conductivities and lower hydraulic head gradients salinities in peripheral salt dissolution zones are low 67 000 to 95 000 mg l 1 despite high solubility of halite reflecting relatively open circulation of ground water in interior salt dissolution zones beneath the southern high plains ground water circulation is low and water composition tends to reach halite saturation

the cenomanian turonian oceanic anoxic event i stratigraphy and distribution of organic carbon rich beds and the marine δ13c excursion marine strata deposited during late cenomanian and early turonian time display lithological faunal and geochemical characteristics which indicate that significant parts of the world ocean were periodically oxygen deficient at or very close to the cenomanian turonian boundary between 90 5 and 91 5ma ago oxygen deficiencies were particularly marked over a period of 1ma this short lived episode of oceanic oxygen deficiency has been termed the cenomanian turonian oceanic anoxic event oae the widespread distribution of anoxic sediments deposited synchronously during such a short lived event indicates that such sediments are not simply the product of coincidental local climatic or basinal water mass characteristics but are the result of a global expansion and intensification of the cenomanian turonian oxygen minimum zone related to feedback between sea level rise and regional palaeoceanography the palaeoceanography of the cenomanian turonian oae is discussed in detail in a companion paper by arthur et al 1987 from authors

hydrochemical characteristics of aquifers near sutherland in the western karoo south africa the western karoo depends entirely on groundwater for domestic and agricultural use an understanding of the chemical evolution of the groundwater provides insight into the interaction of water with the environment and contributes to better resource management descriptive statistics correlation matrices and factor analysis together with stable isotope data were used to gain an understanding of the hydrochemical processes of the groundwaters in the fractured rocks around sutherland in the western karoo the main processes influencing the groundwater chemistry are salinisation mineral precipitation and dissolution cation exchange and human activity the stable isotope data indicate that the infiltration of evaporated water is partly responsible for the occurrence of saline subsurface waters the ionic oxygen and hydrogen stable isotope composition of the groundwaters suggests that the effects of localised topography are one of the overriding factors controlling the groundwater chemistry in higher lying areas ca hco3 2 type waters are prevalent while in topographical flat areas nacl type waters dominate in areas where water collects close to or at the surface saline soils are formed from these areas salts are leached to the subsurface during significant recharge periods these findings are important in that they contribute to the identification of suitable locations for developing groundwater resources that could yield a relatively better quality water q 2001 elsevier science b v all rights reserved

the cenomanian turonian anoxic event in europe an organic geochemical study received 14 october 1988 revised 14august 1989 accepted 31 august 1989 thirty two sediment samples mainly black shales from cenomanian turonian organic rich sequences in europe and tunisia were examined by organic geochemical techniques the results of molecular analyses indicate that all the black shales are dominated by marine derived organic matter from both algal and bacterial sources with only a minor terrestrial component oxygen deficient conditions prevailed during the deposition of the black shales although interbedded non laminated organic lean horizons indicate that oxygen deficiency was intermittent at some sites the presence of 17cx h 18c h 211 h 28 30 bisnorhopane in some black shale samples from shallow shelf areas may be evidence for severely oxygen depleted conditions possibly in association with upwelling and an oxygen minimum layer overall the organic geochemical data are in agreement with a depositional model whereby an oxygen minimum layer developed in response to high surface productivity this oxygen minimum layer may have extended over a considerable thickness of the water column 1000 m in some areas we report the first observation of an a ring methylated c29 hopane namely methyl 17e h 18 h 211 h 28 30 bisnorhopane the environmental significance of this compound cannot yet be assessed although in the sample in which it occurs the direct parallel between the carbon number distribution of the hopanes and that of the methylhopanes suggests either that they have the same biological origin or that methylation of hopanoids may have occurred possibly during diagenesis

hydrologic issues in arid unsaturated systems and implications for contaminant transport analysis of unsaturated flow and transport in arid regions is important not only in water resource evaluation but in contaminant transport as well partic ularly in siting waste disposal facilities and in remediat ing contaminated sites the water fluxes under consid eration have a magnitude close to the errors inherent in measuring or in calculating these water fluxes which makes it difficult to resolve basic issues such as direction and rate of water movement and controls on unsaturated flow the purpose of this paper is to review these issues on the basis of unsaturated zone studies in arid settings because individual techniques for estimating water fluxes in the unsaturated zone have limitations a variety of physical measurements and environmental tracers should be used to provide multiple independent lines of evidence to quantify flow and transport in arid regions the direction and rate of water flow are affected not only by hydraulic head gradients but also by temperature and air pressure gradients the similarity of water fluxes in a variety of settings in the southwestern united states indicates that vegetative cover may be one of the pri mary controls on the magnitude of water flow in the unsaturated zone however our understanding of the role of plants is limited most unsaturated flow in arid systems is focused beneath topographic depressions and diffuse flow is limited thick unsaturated sections and low water fluxes typical of many arid regions result in preservation of paleoclimatic variations in water flux and suggest that deep vadose zones may be out of equilib rium with current climate whereas water movement along preferred pathways is common in humid sites field studies that demonstrate preferential flow are restricted mostly to fractured rocks and root zones in arid regions results of field studies of preferential flow in humid sites generally restricted to the upper 1 2 m because of shallow water tables cannot be applied readily to thick vadose zones in arid regions

wide angle triangulation array study of simultaneous primary microseism sources persistent low frequency noise between 10 and 200 mhz due to storm systems is commonly observed as microseisms on seismic records from land and ocean bottom detectors we report on an analysis of 20 second microseisms recorded simultaneously on two land based long period arrays the alaskan long period array and the large aperture seismic array during november 1973 azimuths of approach are determined by applying frequency wave number analysis and beam forming techniques to coherent bandpass filtered samples of the microseismic noise field recorded by the arrays microseismic source azimuths exhibit sufficient stability over periods of one hour to permit determination of reliable source locations by triangulation with the two arrays locations for two microseism noise sources associated with two separate atlantic and pacific pelagic storms were found simultaneously with these methods in both cases the microseismic noise source appears to be associated with nearshore processes although the gross spectral character of the microseisms displays the commonly observed primary and double frequency microseism peaks slight spectral differences are apparent for the two noise sources

delineation of hydrochemical facies distribution in a regional groundwater system by means of fuzzy c means clustering 1 in this paper classification of a large hydrochemical data set more than 600 water samples and 11 hydrochemical variables from southeastern california by fuzzy c means fcm and hierarchical cluster analysis hca clustering techniques is performed and its application to hydrochemical facies delineation is discussed results from both fcm and hca clustering produced cluster centers prototypes that can be used to identify the physical and chemical processes creating the variations in the water chemistries there are several advantages to fcm and it is concluded that fcm as an exploratory data analysis technique is potentially useful in establishing hydrochemical facies distribution and may provide a better tool than hca for clustering large data sets when overlapping or continuous clusters exist index terms 1806 hydrology chemistry of fresh water 1829 hydrology groundwater hydrology 1831 hydrology groundwater quality 1871 hydrology surface water quality keywords clustering techniques fuzzy logic fuzzy c means hydrochemical facies hydrochemistry inverse modeling

organic facies and thermal maturity of late aptian to early cenomanian shelf deposits northern sinai egypt abstract organic petrologic and geochemical investigations were carried out on late aptian to early cenomanian mid cretaceous sediments recovered from the paleoshelf of the northern sinai egypt the organic facies and thermal maturity of sedimentary organic matter were evaluated with regard to maximum burial depth results from organic geochemical analyses c org n tot rock eval pyrolysis performed on kerogen concentrates indicate the dominance of hydrogen depleted organic matter of either terrestrial or degraded marine origin kerogen typing reveals a mixture of type iii and iv maceral analyses conducted on concentrates support geochemical results showing variable proportions of vitrinite migrabitumen graphite and traces of inertinite vitrinite and inertinite are considered to be of autochthonous or parautochthonous origin indicating at least partly humid paleoclimatic conditions in the hinterland this assumption is also supported by the occurrence of graphite which points to aquatic transport from the southerly exposed precambrian basement the presence of migrabitumen presumably relates to migrated hydrocarbons from underlying organic carbon rich jurassic strata the organic facies of mid cretaceous deposits from the northern sinai indicates a proximal fluvio deltaic or oxic shelf environment equivalent to organic facies types c d according to jones jones r w 1987 organic facies in brooks j welte d h eds advances in petroleum geochemistry academic press london pp 1 80 t max data obtained from rock eval pyrolysis reveal an immature level for organic matter 350 c to 425 c although these values are probably depressed due to the presence of migrabitumen since vitrinite is very scarce in kerogen concentrates reflectance measurements were also performed on migrabitumen the best correlation of both types of reflectance data was obtained when migrabitumen data were corrected following the approach of jacob jacob h 1989 classification structure genesis and practical importance of natural solid oil bitumen int j coal geology 11 pp 65 79 reflectance values range between 0 6 to 0 7 rm equivalent to high volatile bituminous coalification stages since there is no indication for an abnormal geothermal gradient along the ne african margin a maximum burial depth between 1 2 km and 2 0 km is estimated for the mid cretaceous strata of the northern sinai