Independent measurement of biogenic silica in sediments by FTIR spectroscopy and PLS regression

We present an independent calibration model for the determination of biogenic silica (BSi) in sediments, developed from analysis of synthetic sediment mixtures and application of Fourier transform infrared spectroscopy (FTIRS) and partial least squares regression (PLSR) modeling. In contrast to current FTIRS applications for quantifying BSi, this new calibration is independent from conventional wet-chemical techniques and their associated measurement uncertainties. This approach also removes the need for developing internal calibrations between the two methods for individual sediments records. For the independent calibration, we produced six series of different synthetic sediment mixtures using two purified diatom extracts, with one extract mixed with quartz sand, calcite, 60/40 quartz/calcite and two different natural sediments, and a second extract mixed with one of the natural sediments. A total of 306 samples—51 samples per series—yielded BSi contents ranging from 0 to 100 %. The resulting PLSR calibration model between the FTIR spectral information and the defined BSi concentration of the synthetic sediment mixtures exhibits a strong cross-validated correlation ( \( {\text{R}}^{ 2}_{\text{cv}} \)  = 0.97) and a low root-mean square error of cross-validation (RMSECV = 4.7 %). Application of the independent calibration to natural lacustrine and marine sediments yields robust BSi reconstructions. At present, the synthetic mixtures do not include the variation in organic matter that occurs in natural samples, which may explain the somewhat lower prediction accuracy of the calibration model for organic-rich samples.     

Contribution of Geophysics to the Management of Water Resources: Case of the Ariana Agricultural Sector (Eastern Mejerda Basin,Tunisia)

In Tunisia, the Mejerda basin is the most important agricultural sector. Identification of additional water sources and good management of current and new resources is required to maintain and increase its productivity. The present study concerns the Ariana region (north-east of Tunisia) covering the eastern part of Mejerda basin. Lithological columns, well logs, vertical electrical soundings, and gravity data were analyzed and interpreted to give more precise information for exploitation of the water resources of the Ariana region. Lithological columns, well logs, and geoelectrical models reveal that the permeable Quaternary alluvial deposits, the Upper Campanian–Lower Maestrichtian, Albian and Barremian limestones, and Valanginian–Hauterivian sandstones are the main aquifers in Ariana. Comparison of geoelectrical cross sections to the Bouguer anomaly map of the Ariana region reveals tectonic influence on the geometry of the aquifers. The folded structures attributed to the Tortonian compressive stress and the tectonic movements in N–S, E–W, NW–SE, and NE–SW directions have resulted in the compartmentalization of Ariana’s aquifers into subsided and raised blocks. This reconstituted geometry of the region influenced the depth of burial of permeable lithologies and inhibited groundwater circulation in some localities.     

Evaluation of Recharge and Groundwater Dynamics of a Shallow Alluvial Aquifer in Central Ganga Basin,Kanpur (India)

Evaluation of recharge and groundwater dynamics of an aquifer is an important step for finding a proper groundwater management scenario. This has been performed on the basis of statistical Kendall Tau test to find a relationship between groundwater levels and hydro-meteorological parameters (e.g., precipitation, temperature, evaporation). Recharge to the aquifer was estimated for identification of critical areas/locations based on the analytical Soil and Water Assessment Tool. Moreover, spatiotemporal variability of groundwater levels has been quantified using space–time variogram. The overall characterization method has been applied to the shallow alluvial aquifer of Kanpur city in India. The analysis was performed using groundwater level data from 56 monitoring piezometer locations in Kanpur from March 2006 to June 2011. Groundwater level shows relatively higher correlation with temperature. Performance of the geostatistical model was evaluated by comparing with the observed values of groundwater level from January 2011 to June 2011 for two scenarios: “with limited spatiotemporal data” and “without spatiotemporal data.” It is evident that spatiotemporal prediction of groundwater level can be performed even for the unmonitored/missing data. This analysis demonstrates the potential applicability of the method for a general aquifer system.     

Groundwater Assessment for Current and Future Water Demand in the Daka Catchment,Northern Region,Ghana

The use of untreated surface water for domestic purposes has resulted in the infection of some people by guinea worm and other water borne diseases in the Northern Region of Ghana. The aim of this study is to assess the current groundwater quantity and quality conditions in the 7,820 km² Daka catchment and project the water demand in 2025. Results of groundwater analyses generally show good water quality for domestic use. Borehole analyses indicate that the catchment’s groundwater system can be characterized by a regolith aquifer underlain by a deeper fractured rock aquifer in some areas. The current per capita water demand is estimated at 40 l/day although 60 l/day is the desired amount, indicating that with the current population of 363,350, the projected water demand for the communities is 21,800 m³/day. With a projected population of 555,500 in 2025, an expected 33,300 m³/day of water is required. The estimated optimum potential groundwater available for use in the catchment is 154 × 10⁶ m³/year (4.24 × 10⁵ m³/day). However, the current total groundwater abstraction is only 8,876 m³/day or 2% of the optimum. In comparison, the projected total current and 2025 water demands are only 5 and 8%, respectively, of the optimum potential groundwater available for use in the catchment. In addition, only 1,780 m³/day (0.65 × 10⁶ m³/year) or 0.06% of the average annual flow of 1,016 × 10⁶ m³/year of the Daka River is treated for domestic use. These figures reveal that a significantly very large water resource potential exists for both surface and groundwater development in the Daka catchment. It is suggested that their development should proceed conjunctively.     

Burial dolomitization driven by modified seawater and basal aquifer‐sourced brines: Insights from the Middle and Upper Devonian of the Western Canadian Sedimentary Basin

Dolomitization in the Western Canadian Sedimentary Basin has been extensively researched, producing vast geochemical datasets. This provides a unique opportunity to assess the regional sources and flux of dolomitizing fluids on a larger scale than previous studies. A meta‐analysis was conducted on stable isotope, strontium isotope (⁸⁷Sr/⁸⁶Sr), fluid inclusion and lithium‐rich formation water data published over 30 years, with new petrographic, X‐ray diffraction, stable isotope and rare‐earth element (REE+Y) data. The Middle to Upper Devonian Swan Hills Formation, Leduc Formation and Wabamun Group contain replacement dolomite (RD) cross‐cut by stylolites, suggesting replacement dolomitization occurred during shallow burial. Stable isotope, REE+Y and ⁸⁷Sr/⁸⁶Sr data indicate RD formed from Devonian seawater, then recrystallized during burial. Apart from the Wabamun Group of the Peace River Arch (PRA), saddle dolomite cement (SDC) is more δ¹⁸O_(PDB) depleted than RD, and cross‐cuts stylolites, suggesting precipitation during deep burial. SDC ⁸⁷Sr/⁸⁶Sr data indicate contributions from ⁸⁷Sr‐rich basinal brines in the West Shale Basin (WSB) and PRA, and authigenic quartz/albite suggests basinal brines interacted with underlying clastic aquifers before ascending faults into carbonate strata. The absence of quartz/albite within dolomites of the East Shale Basin (ESB) suggests dolomitizing fluids only interacted with carbonate strata. We conclude that replacement dolomitization resulted from connate Devonian seawater circulating through aquifers and faults during shallow burial. SDC precipitated during deep burial from basinal brines sourced from basal carbonates (ESB) and clastic aquifers (WSB, PRA). Lithium‐rich formation waters suggest basinal brines originated as residual evapo‐concentrated Middle Devonian seawater that interacted with basal aquifers and ascended faults during the Antler and Laramide Orogenies. These results corroborate those of previous studies but are verified by new integrated analysis of multiple datasets. New insights emphasize the importance of basal aquifers and residual evapo‐concentrated seawater in dolomitization, which is potentially applicable to other regionally dolomitized basins.     

民勤盆地地下水地球化学演化模拟

根据稳定同位素分析,民勤盆地地下水在第四系总体补给环境较现代凉。在200m以下的深层地下水为晚更新世补给的古封存水,表现为还原环境。60m—120m左右的浅层水为古地下水与现代降水的混合水,但古地下水占的成分较多,部分水样为氧化环境。民勤盆地地下水地球化学特征主要形成于山区,在沿途运移过程强烈的蒸发浓缩作用占据主导地位,形成了浅层高矿化盐碱水,深层地下水活跃的阳离子交换作用形成高钠浓度水。通过利用PHREEEQC法对民勤盆地地下水化学进行质量平衡模拟,表明民勤盆地地下水水化学沿水流路径以HCO3^-、SO4^2-、Cl^-、Ca^2 、Na^ 升高为主要特征,方解石、白云石的饱和指数随水流路径有减少趋势,而石膏、芒硝和岩盐的饱和指数有增加的趋势：沿水流途径白云石、CO2、石膏、岩盐和芒硝溶解量逐渐增加是常量离子浓度升高的物质来源。     

Spatial Distribution of Fractures in the Asmari Formation of Iran in Subsurface Environment: Effect of Lithology and Petrophysical Properties

The distribution of fractures and its dependence on lithology and petrophysical properties of rock in the Asmari Formation were examined using three wells data of one of the largest oil fields of southwestern Iran. Fractures were measured on cut cores. Mineral content and petrophysical data were obtained through thin section study and core plug measurement respectively. Influence of mineral composition and petrophysical property of rocks on fracture density was explored statistically. Increasing quartz (sand) and anhydrite content of rocks decrease and dolomite increases the threshold of fracture densities, however no significant relation was observed between calcite content of rock and fracture density. Increasing porosity and permeability of rock decrease the threshold of fracture density in some of the defined lithology groups. There are significant differences between the lithology groups in terms of fracture density, although the results in the three wells are not the same. In whole data, the highest fracture density can be observed in dolostone. Limestone and impure carbonates hold broader spaced fractures and sandstones display the least fracture density. The average fracture densities in the wells are strictly different. These differences are the result of the structural position of the wells and also the trend of the well and fractures. The distribution of fractures in most lithology groups can be explained by the function: , where F is relative frequency, D is fracture density and a, b, and c are constants.     

Temporal changes in the contribution of methane-oxidizing bacteria to the biomass of chironomid larvae determined using stable carbon isotopes and ancient DNA

Freshwater lakes are important sources of methane (CH₄) emissions, by organic matter degradation under anaerobic conditions (methanogenesis). Previous studies suggest that lakes contribute up to 16 % of natural emissions. About 60 % of the CH₄ produced is used as an energy source by methane-oxidizing bacteria (MOB—methanotrophs), which could support higher trophic levels, especially Chironomidae (Diptera). Because biogenic methane has a very low stable carbon isotope value, evidence of methane-derived organic-matter assimilation can be tracked by stable carbon isotope analysis in consumers such as chironomids. In some cases, however, chironomid δ¹³C values are not low enough to unambiguously demonstrate methanotroph assimilation and an alternative line of evidence is required. Analysis of ancient DNA (aDNA) from the methanotroph community preserved in lake sediment provides reliable information about past methane oxidation in freshwater lakes. A combination of these two approaches was used to study a sediment core from the deepest zone of Lake Narlay (Jura, France), which covers the last 1,500 years of sediment accumulation. Results show a significant change ca. AD 1600, with an increase in the proportion of MOB in the total bacteria community, and a decrease in chironomid head-capsule δ¹³C. These trends suggest assimilation of MOB by chironomid larvae, and account for up to 36 % of the chironomid biomass. The data also provide information about the feeding behavior of chironomids, with evidence for preferential assimilation of methanotroph type I and the NC10 phylum. The combination of aDNA analysis and carbon stable isotopes strengthens the reliability of inferences about carbon sources incorporated into chironomid biomass.     

A Revies of: Some Truth with Maps; A Primer on Symbolisation & Design.

In this article, we present a geographically explicit agent-based model (ABM), loosely coupled with vector geographical information systems (GISs), which explicitly captures and uses geometric data and socioeconomic attributes in the simulation process. The ability to represent the urban environment as a series of points, lines, and polygons not only allows one to represent a range of different-sized features such as buildings or larger areas portrayed as the urban environment but is a move away from many ABMs utilizing GIS that are rooted in grid-based structures. We apply this model to the study of residential segregation, specifically creating a Schelling (1971 Schelling, T.C. 1971. Dynamic models of segregation. Journal of Mathematical Sociology, 1(1): 143–186. [Taylor &; Francis Online] , [Google Scholar]) type of model within a hypothetical cityscape, thus demonstrating how this approach can be used for linking vector-based GIS and agent-based modeling. A selection of simulation experiments are presented, highlighting the inner workings of the model and how aggregate patterns of segregation can emerge from the mild tastes and preferences of individual agents interacting locally over time. Furthermore, the article suggests how this model could be extended and demonstrates the importance of explicit geographical space in the modeling process.     

Evaluating environmental drivers of Holocene changes in water chemistry and aquatic biota composition at Lake Loitsana,NE Finland

This study presents a detailed analysis of geochemical and biotic proxies in a lake sediment profile to assess the effects of local and regional environmental drivers on the Holocene development of Lake Loitsana, situated in the northern boreal forest of NE Finland. Multi-proxy studies, in particular those that include a detailed plant macrofossil record, from the part of the northern boreal zone of Fennoscandia which has not been affected by treeline fluctuations, are scarce and few of these records date back to the earliest part of the Holocene. A 9-m sediment sequence of gyttja overlying silts representing the last c. 10,700 cal year, allowed for a high-resolution study with emphasis on the early to mid-Holocene lake history. The lacustrine sediments were studied using lithology, loss-on-ignition and C/N ratios, micro- and macro-fossils of aquatic and wetland taxa, diatoms, chironomids and accelerator mass spectrometry ¹⁴C dating on terrestrial plant macrofossils. Our study shows that the local development at Loitsana was complex and included a distinct glacial lake phase and subsequent drainage, a history of fluvial input affected by nearby wetland expansion, and lake infilling in an eventual esker-fed shallow lake. Enhanced trophic conditions, due to morphometric eutrophication, are recorded as Glacial Lake Sokli drained and open water conditions became restricted to a relatively small Lake Loitsana depression. pH appears to have been stable throughout the Holocene with a well-buffered lake due to the local carbonatite bedrock (Sokli Carbonatite Massif). The fossil assemblage changes are best explained by a complex mixture of drivers, including water-body conditions (i.e. depth, turbidity and turbulence), rate of sediment input, and the general infilling of the lake, highlighting the need to carefully evaluate the possible influence of such local factors as palaeoenvironmental conditions are reconstructed based on aquatic proxies.     

Use of fine-scale stratigraphy and chemostratigraphy to evaluate conditions of deposition and preservation of a Triassic Lagerst?tte, south-central Virginia

The rich, fossiliferous Triassic sediments exposed in the Virginia Solite Quarry include a 34-mm-thick “insect layer” that is notable for detailed preservation of soft-bodied invertebrate and vertebrate remains. We describe this unique Konservat-Lagerst?tte and use sedimentologic and geochemical analyses to interpret the environmental conditions necessary to preserve such delicate fossils. This work is among the first attempts to apply detailed geochemical/stratigraphic analysis to the study of Lagerst?tten and we report on a 332-mm-thick section that includes the insect layer and the rocks immediately below and above it. Our analysis successfully constrains various aspects of the depositional and diagenetic history of the Lagerst?tte and permits a detailed analysis of changing conditions prior to, during, and after deposition. Geochemical and sedimentologic analyses of the insect layer and surrounding lithologies reveal a change from siliciclastic-dominated layers (Unit 1) to dolomite-siliciclastic laminites above (Unit 2 and the insect layer), separated by a boundary dolostone layer that is traceable for over 200 m. We interpret this sedimentary shift as the initial stages in the transgression of a shallow, saline, alkaline rift-basin lake over lake margin deposits. The absence of bioturbation by plants and benthic organisms, as well as a lack of predation on the insects, is not explained by significant water depth, but is instead more reasonably considered a result of the chemistry of the water at the lake margin, affected by groundwater seeps, which provided F-, Mg-, and Ca-rich fluids. Although the initial conditions of preservation are remarkable, it is equally impressive that the fossils survived extensive diagenesis, e.g. dissolution of quartz and coarsening of dolomite.     

Mineralogical and Thermoluminescence Characterizations of the River Sediments from Tamilnadu, India

In this study, the mineralogical characterizations of the sediments have been carried out using Fourier Transform Infrared (FTIR) spectroscopic and XRD technique. The extinction co-efficient and crystallinity index are calculated to know the relative distribution of major minerals and crystalline nature of quartz, respectively. From the FTIR and XRD techniques, the minerals, such as quartz, microcline feldspar, orthoclase feldspar, kaolinite, calcite, gibbsite, montmorillonite, smectite, palygorskite, organic carbon, zircon, monazite, montmorillonite, and hornblende are identified. Thermoluminescence (TL) behavior of the sediments has been studied through the measurements of both Natural Thermoluminescence (NTL) and Artificial Thermoluminescence (ATL). Correlation analysis has been carried out among the parameters obtained from both mineral and TL analyses to know the existing interrelations. The obtained correlations are discussed, and it is suggested that the NTL and ATL measurements of the sediments show the valuable information about the sedimentation process. Thus, we conclude that the TL is the easiest tool to find out the sedimentation of the river.     

Policy Change and Venue Choices: Field Burning in Idaho and Washington

Grass seed farmers have burned their fields in Idaho and Washington State for decades. Field burning, however, creates small particulate matter air pollution, thus engendering a growing public backlash by the 1990s that manifested itself in new clean air advocacy groups. The new groups’ push for policy change eventually met with significant success in both cases. How did each set of advocates approach the challenge of policy change? More specifically, what kinds of policy venues did each group choose and why? This research uses the cases to explore and explain each clean air group's choices vis-à-vis hypotheses of venue choice. Three hypotheses are tested—Schattschneider's (1960 Schattschneider , E. E. 1960 . The semisovereign people . New York , NY : Holt, Rinehart, and Winston . [Google Scholar]) “expanded scope of conflict” thesis, ACF's (Sabatier and Jenkins-Smith 1999 Sabatier , P. , and H. Jenkins-Smith . 1999 . The advocacy coalition framework: An assessment . In Theories of the policy process , ed. P. A. Sabatier , 117 – 166 . Boulder , CO : Westview Press . [Google Scholar]) contention that groups strategically apply their resources in order to increase the likelihood of achieving their primary goal(s), and Pralle's (2003 Pralle , S. B. 2003 . Venue shopping, political strategy, and policy change . J. Public Policy 23 : 233 – 260 .[Crossref] , [Google Scholar], 2010 Pralle , S. B. 2010 . Shopping around: Environmental organizations and the search for policy venues . In Advocacy organizations and collective action , ed. A. Prakash and M. K. Gugerty , 177 – 203 . Cambridge , MA : Cambridge University Press .[Crossref] , [Google Scholar]) thesis that internal group constraints deter groups from moving into new venues.     

Geochemistry of groundwater in front of a warm‐based glacier in Southeast Greenland

Groundwater in front of warm‐based glaciers is likely to become a more integrated part of the future proglacial hydrological system at high latitudes due to global warming. Here, we present the first monitoring results of shallow groundwater chemistry and geochemical fingerprinting of glacier meltwater in front of a warm‐based glacier in Southeast Greenland (Mittivakkat Gletscher, 65° 41′ N, 37° 48′ W). The groundwater temperature, electrical conductivity and pressure head were monitored from August 2009 to August 2011, and water samples were collected in 2009 and analyzed for major ions and water isotopes (δD, δ¹⁸O). The 2 yrs of monitoring revealed that major outbursts of glacier water during the ablation season flushed the proglacial aquifer and determined the groundwater quality for the next 2–8 weeks until stable chemical conditions were reached again. Water isotope composition shows that isotopic fractionation occurs in both groundwater and glacier meltwater, but fractionation due to evaporation from near‐surface soil moisture prior to infiltration has the most significant effect. This study shows that groundwater in Low Arctic Greenland is likely to possess a combined geochemical and isotopic composition, which is distinguishable from other water sources in the proglacial environment. However, the shallow groundwater composition at a given time is highly dependent on major outbursts of glacier water in the previous months.     

Renaming and Rebranding within U.S. and Canadian Geography Departments, 1990–2014

Between 2000 and 2014, more than thirty geography departments adopted revised or new names, with some entirely dropping geography. Although renaming and rebranding efforts are not new to higher education, the rapid pace at which geography department names have changed raises questions about the discipline's identity and health. We examine the renaming trend within geography programs together with intended and unexpected factors as perceived by faculty. Specifically, we look at the renaming and rebranding trend within the context of four pillars offered by Pattison (1964 Pattison, W. D. 1964. The four traditions of geography. Journal of Geography 63 (5): 211–16.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) to define geography's principal academic domains—earth-science, man–land, area/regional studies, and spatial traditions.     

Fluid inclusions as constraints in a three‐dimensional hydro‐thermo‐mechanical model of the Paris basin,France

Fluid inclusion homogenization temperatures and three‐dimensional hydro‐thermo‐mechanical modelling were combined to constrain fluid flow, solute and heat transport in the Paris basin, France, focusing on the two main petroleum reservoirs i.e. the Dogger and the Triassic (Keuper) formations. The average homogenization temperatures of two‐phase aqueous inclusions in different samples range from 66 °C to 88 °C in the Dogger calcite cement, from 106 °C to 118 °C in the Keuper dolomite cement and from 89 °C to 126 °C in the Keuper quartz and K‐feldspar cements. The maximum homogenization temperatures for inclusions in the Keuper quartz and K‐feldspar cements were 17–47 °C higher than present‐day temperatures in the boreholes at similar depths. Processes that might explain higher temperatures in the past were examined through numerical simulations and sensitivity tests. A warmer climate in the Late Cretaceous–Early Tertiary resulted in a temperature rise of only 8 °C. Late Cretaceous chalk had a thermal blanketing effect that resulted in simulated temperatures as high as 15–20 °C above the present day ones. An additional 300 m deposition and subsequent erosion of chalk, not taken into account so far, has to be considered to simulate the high palaeo‐temperatures recorded by fluid inclusions in both reservoirs. In view of the simulated thermal history of the basin, in the Keuper, an age of about 85 Ma is consistent with quartz/K‐feldspar temperatures and an age of about 65 Ma is in agreement with the precipitation temperature of the dolomite cement. Our models suggest an age of about 50 Ma for the Dogger calcite cementation.     

Extended weights of evidence modeling for the pseudo-estimation of metal grades

The weights of evidence modeling (WEM) for binary patterns is extended to take account of general categorical variables. The extension makes it possible to use the weights of evidence model in estimating the conditional probability distributions of metal grades. First, the target feature is converted into a set of binary target indicators. Second, the posterior probabilities are estimated for each of the target categories. Third, the estimates are combined to yield the posterior probability distribution of the target feature. Finally, the pseudometal estimates are derived from the probability distribution. The metal grade estimates are prefixed with pseudo, because the estimates are created from indirect evidence (explanatory variables). The pseudo-estimates provide a unique quantitative means to the delineation of exploration targets. This advantage reduces the ambiguities of target selection based solely on probability estimates. In order to use the generalized WEM, continuous geoscience attributes must be converted into categorical variables by means of optimal segmentation based on the target attribute of interest. The segmentation may be viewed as a process of defining evidence of the target feature. The extended weights of evidence model is demonstrated on a case study to select gold targets of Carlin type. The dataset used in the modeling includes apparent resistivity fields, soil geochemical samples, lithological and alteration information, and structural data.     

Introduction: Toward More Inclusive and Comparative Perspectives in the Histories of Geographical Knowledge

Over the past three decades, feminist historiography of geography has begun to situate women's contribution to the production of geographical knowledge within the histories of geography, at times against the conviction of skeptical colleagues. In this Focus Section introduction, we renew Domosh's (1991a Domosh, M. 1991a. Beyond the frontiers of geographical knowledge. Transactions of the Institute of British Geographers 16 (4): 488–90.[Crossref], [Web of Science ®] , [Google Scholar], 1991b ———. 1991b. Toward a feminist historiography of geography. Transactions of the Institute of British Geographers 16 (1): 95–104.[Crossref], [Web of Science ®] , [Google Scholar]) call for creating more inclusive feminist histories of geography by situating the three focus section articles on the careers and contributions of women in twentieth-century geographical practice and knowledge production in the United Kingdom and the United States within wider debates about diverse, unfamiliar, and previously hidden aspects of geographical knowledge production. We argue that feminist historiography of geography and feminist historical geography could benefit from continuously diversifying inclusive and comparative research perspectives, and from unlocking diverse archives, to enhance understanding of why and how some male and some female gatekeepers have been more supportive of women than others.     

A reconnaissance study of oxygen, hydrogen and strontium isotopes in geochemically diverse lakes, Western Nebraska, USA

Reconnaissance ¹⁸O,, D, and ⁸⁷Sr data for fifteen lakes in the Western Lakes Region of the Sand Hills of Nebraska indicate dynamic hydrologic systems. The rather narrow range of ⁸⁷Sr from lake water (1.1 to 2.1) and groundwater (0.9 to 1.7) indicates that the groundwater is generally unradiogenic. Groundwater residence times and relatively unradiogenic volcanic ash within the dune sediments control the ⁸⁷Sr values. Based on the mutual variations of ¹⁸O and D, the lakes can be divided into three groups. In Group 1, both ¹⁸O and D values increase from spring to fall. The ¹⁸O and D values in Group 2 decreased from spring to fall. Group 3 are ephemeral lakes that went dry some time during 1992. The data and isotopic modeling show that variations in the ratio of evaporation relative to groundwater inflow, local humidity conditions, and the _a has substantial influence on the isotopic composition. In addition, isotopic behavior in ephemeral lakes can be rather unusual because of the changing activities of water and mineral precipitation and redissolution. The annual and interannual isotopic variability of these lakes which is reflected in the paleonvironmental indicators may be the rule rather than the exception in these types of systems.     

Physicochemical, mineralogical, and geochemical characteristics of lacustrine sediments of the Konya Basin, Turkey, and their significance in relation to climatic change

Physicochemical, mineralogical, and geochemical characteristics of 279 highly calcareous lacustrine sediment samples obtained from a 30 m drilling core in the western part of the Great Konya Basin, Turkey were studied. The sediments have a predominance of silt and clay fractions with a median diameter of 3–5 μm. Vertical changes of the amounts of water soluble components, gypsum, carbonates, and non-salt minerals such as quartz, feldspars, and layer silicates in the sediments suggest that there were climatic changes in the Konya Basin. The dominant clay mineral is smectite followed by kaolinite, illite, and palygorskite. The oxygen isotopic (δ¹⁸O) ratios of six quartz samples from the Konya sediments, a terra rossa soil beside Lake Bey ehir gölü and paleosols at the foot of Mt. Erciyes Da ranged from +18.1 to +20.6‰. The dominant clay minerals and δ¹⁸O ratios suggest that part of quartz and coexisting layer silicates is of long-range transported and/or local aeolian dust origin from arid and semi-arid regions such as North Africa, Israel, and the surroundings. The relatively high deposition rate might be due to aeolian dust input and/or the sediment input introduced by the rivers such as the Çar amba river from the Toros (Taurus) mountains. The vertical distributions of electro-conductivity, amounts of water soluble and non-salt components, and the gypsum content of the sediments suggest that gypsum-rich layers were formed under shallow, saline waters, possibly associated with warm to hot and dry environments such as the Last Interglacial epoch and the Early Holocene. The sediments characterized by relatively high amounts of non-salt sediments, in which gypsum did not accumulate, could be deeper water phases formed under the cold and/or wet environments such as the Glacial epochs.