Lacustrine Materials Research Articles

Effect of Various Aspects of Joints on Permeability of Jointed Glacial Till, Northeastern Ohio

ABSTRACT Glacial till bluffs along Lake Erie's shoreline, northeastern Ohio, contain three sets of joints that influence the hydraulic behavior of till mass like joints in rock influence the hydraulic behavior of rock mass. According to the Unified Soil Classification System, the till classifies as low plasticity silt to low plasticity clay, with a clay content of 36–41 percent. Mineralogically, it consists of quartz, illite, and kaolinite. The joints in till are either open or filled with sand, silt, or both from the overlying lacustrine material or with disintegrated till from the joint walls. We used double-ring infiltration and dye tests to estimate field permeability. Laboratory permeability tests were performed on dry and saturated samples of till material, with manually created joints that were either kept open or filled with sand or disintegrated till material to simulate field conditions. Field and laboratory test results showed that permeability of jointed till depended upon whether the joints were open or filled, the nature of the joint-filling material, and the water content of the till (dry versus saturated) and that permeability generally decreased with increasing test time. Dry samples exhibited a substantially larger decrease in permeability than saturated samples, with the largest decrease occurring during the first 24 hours. Open joints in dry samples collapsed during the test procedure, and the permeability of these samples was generally similar to the permeability of the collapsed till material. Permeability tests on saturated samples with open joints were inconclusive. We present a comparison of field and laboratory test results.

Characteristics of Source Rocks and Genetic Origins of Natural Gas in Deep Formations, Gudian Depression, Songliao Basin, NE China

Numerous large gas fields with large proven reserves occur in the deep formations of Songliao Basin, NE China. However, some challenges remain as follows: (1) the main source rock is poorly studied and (2) the origins and genetic types of the natural gases are controversial. In this study, these problems can be addressed by the research of the paleoenvironments during shale deposition, the organic matter sources, the source rock potential, the gas origin and genetic type, and gas–source correlations. The redox conditions of the water column during the Huoshiling to Yingcheng depositions were transitional (suboxidizing to subreducing) environments, and the Huoshiling deposition corresponded to reducing conditions. The paleosalinity of water was brackish to fresh from Huoshiling to Yingcheng depositions. The organic matters of the Huoshiling–Yingcheng shales mainly originated from terrigenous and/or lacustrine materials. The shales are evaluated as the fair to good source rock potential, and the Huoshiling is the best. The gases in the Huoshiling and Shahezi were mainly organic and thermogenic origins, with some inorganic origins. The gases of organic origins are mainly the mixed sources of coal-derived and oil-associated gases and are predominant products of secondary cracking, suggesting the well gas exploration potential in deep formations of Songliao Basin. The gases in the Shahezi formation are predominantly sourced by the Shahezi shales, indicating an approaching-source accumulation.

The Isotope Composition, Nature, and Main Mechanisms of Formation of Different Types and Subtypes of Salt Lakes in Transbaikalia

Abstract —More than a hundred lakes, groundwater, rivers, and precipitation of their catchments have been studied in Transbaikalia. The chemical composition of natural waters and the mineral composition of rocks and lacustrine bottom sediments have been analyzed. The isotope composition of waters, the isotope ratios in dissolved and deposited carbonates and in bacterial mats, and the content of heavy oxygen in the aluminosilicate fraction of bottom sediments and rocks in catchments have been determined. It is shown that all secondary minerals inherit the oxygen isotope composition of water, but their oxygen is isotopically much heavier than the water oxygen, because the water–rock interaction leads to the fractionation of oxygen and the transition of its heavy isotope into secondary carbonates and aluminosilicates. Bacterial mats using oxygen of carbon dioxide ions for their vital activity are also enriched in its heavy isotope. We have established that the water of soda lakes, being less saline than other lake waters, is more enriched in heavy oxygen isotope. Mineral analysis of lacustrine bottom sediments and material from sedimentation traps revealed chemogenic carbonates and secondary aluminosilicates. The performed thermodynamic calculations confirm their possible formation in lakes. It is shown that the lake water is in equilibrium not only with carbonates, clays, and hydromica but also with zeolites, and the most alkaline and mineralized water is in equilibrium with albite. The bottom sediments of soda lakes have a greater portion of clays and carbonates than those of fresh, chloride, and sulfate waters. The enrichment of salt lake waters with heavy isotopes is due not only to evaporation but also to the water–rock interaction. The contribution of aluminosilicate hydrolysis to oxygen fractionation is confirmed by the direct dependence of the “oxygen shift” value on pH, whose value is determined by the degree of the above interaction. We have established that the diversity of the chemical and isotope compositions of lake waters is due to their multifactorial formation related to the different degrees of lake water evaporation, the different mineralization of organic matter, and the different duration of the interaction of lake waters and groundwater with rocks.

Soil chronosequence and biosequence on old lake sediments of the Burdur Lake in Turkey

The Burdur Lake is located in the southwest of Turkey, and its area has decreased by 40% from 211 km2 in 1975 to 126 km2 in 2019. In this study, we investigated how the soil has changed in the lacustrine material. Three soil profiles were sampled from the former lakebed (chronosequence profiles: P1, 2007; P2, 1994; and P3, 1975), and three soil profiles under different land use types (biosequence profiles: P4, native forest vegetation; P5, agriculture; and P6, lakebed) were sampled. The chronosequence and biosequence soil profiles represented various distances from the Burdur Lake and showed different stages of lacustrine evolution. Soil electrical conductivity (EC; 18.1 to 0.4 dS m–1), exchangeable Na+ (34.7 to 1.4 cmol kg–1) and K+ (0.61 to 0.56 cmol kg–1), and water-soluble Cl– (70.3 to 2.1 cmol L–1) and SO24– (275.9 to 25.0 cmol L–1) decreased with increasing distance from the Burdur Lake, whereas the A horizon thickness (10 to 48 cm), structure formation (0 to 48 cm), gleization-oxidation depth (0 to 79 cm), and montmorillonite and organic matter (OM; 25.9 to 46.0 g kg–1) contents increased in the chronosequence soil profiles. The formation of P3 in the chronosequence and P5 in the biosequence soil profiles increased due to longer exposure to pedogenic processes (time, land use, vegetation, etc.). Changes in EC, exchangeable cation (Na+ and K+) and water-soluble anion (Cl– and SO24–) concentrations of the salt-enriched horizon, OM, gleization-oxidation depth, A horizon thickness, and structure formation of the chronosequence and biosequence soil profiles (especially the topsoil horizon) were highly related to the distance from the Burdur Lake, time, and land use.

Burdur Gölü’ndeki seviye değişimi sonucunda ortaya çıkan lakustrin materyalin zamansal ve mekansal değişimi

Türkiye’nin Göller Bölgesinde yer alan ve Ramsar sulak alanı olan Burdur Gölü, son yıllarda dramatik bir şekilde hızla kurumaktadır. Bu çalışmanın amacı; son 42 yılda (1975-2017) Burdur Göl seviyesinin azalması ile bazı iklimsel parametreler arasındaki ilişkiyi değerlendirmek ve karasal ortama çıkan lakustrin materyallerin zamana bağlı konumsal ve alansal dağılımlarını tespit etmektir. Burdur Gölü seviyesinin azalması üzerinde etkisi olan iklim ve diğer faktörler sonucunda; göl seviyesinin 13.74 m alçaldığı (-% 2) ve göl alanının 211 km2’den 130 km2’ye kadar (-% 38.39) gerilediği tespit edilmiştir. Ortaya çıkan lakustrin materyalin konumsal dağılımları ise; daha düşük ortalama eğime (% 0.12) sahip Kuzey Doğu Sahili’nde (KDS) yoğunluk göstermektedir. Burdur Gölü’nün su seviyesinin azalması ile iklimsel parametreler arasındaki ilişki incelendiğinde; göl seviyesindeki azalma ile en güçlü ilişkinin sıcaklık (-0.637**) ve toplam buharlaşma (-0.603**) arasında olduğu tespit edilmiştir. Yıllık toplam yağış miktarı ile göl seviyesinin azalması arasında, herhangi bir ilişki tespit edilememiştir. Bu sonuçlara göre, Burdur Gölü’nün kurumasında etkili olduğu düşünülen iklim faktörlerine müdahale ederek göl havzasının su bilançosu üzerindeki baskının azaltılması pek mümkün görünmemektedir. Bu sebeple Burdur Gölü’nün devamlılığını sağlamak için, hatalı arazi kullanımı ve hatalı tarımsal üretim deseni üzerinde gerekli yasal düzenlemelerin acilen yapılması gerekmektedir.

Identification and analysis of low-molecular-weight dissolved organic carbon in subglacial basal ice ecosystems by ion chromatography

Abstract. Determining the concentration and composition of dissolved organic carbon (DOC) in glacial ecosystems is important for assessments of in situ microbial activity and contributions to wider biogeochemical cycles. Nonetheless, there is limited knowledge of the abundance and character of DOC in basal ice and the subglacial environment and a lack of quantitative data on low-molecular-weight (LMW) DOC components, which are believed to be highly bioavailable to microorganisms. We investigated the abundance and composition of DOC in basal ice via a molecular-level DOC analysis. Spectrofluorometry and a novel ion chromatographic method, which has been little utilized in glacial science for LMW-DOC determinations, were employed to identify and quantify the major LMW fractions (free amino acids, carbohydrates, and carboxylic acids) in basal ice from four glaciers, each with a different type of overridden material (i.e. the pre-entrainment sedimentary type such as lacustrine material or palaeosols). Basal ice from Joyce Glacier (Antarctica) was unique in that 98 % of the LMW-DOC was derived from the extremely diverse free amino acid (FAA) pool, comprising 14 FAAs. LMW-DOC concentrations in basal ice were dependent on the bioavailability of the overridden organic carbon (OC), which in turn was influenced by the type of overridden material. Mean LMW-DOC concentrations in basal ice from Russell Glacier (Greenland), Finsterwalderbreen (Svalbard), and Engabreen (Norway) were low (0–417 nM C), attributed to the relatively refractory nature of the OC in the overridden palaeosols and bedrock. In contrast, mean LMW-DOC concentrations were an order of magnitude higher (4430 nM C) in basal ice from Joyce Glacier, a reflection of the high bioavailability of the overridden lacustrine material (> 17 % of the sediment OC comprised extractable carbohydrates, a proxy for bioavailable OC). We find that the overridden material may act as a direct (via abiotic leaching) and indirect (via microbial cycling) source of DOC to the subglacial environment and provides a range of LMW-DOC compounds that may stimulate microbial activity in wet subglacial sediments.

Analysis of the variation of the compressibility index (Cc) of volcanic clays and its application to estimate subsidence in lacustrine areas

Abstract. An analysis of the deformation conditions of lacustrine materials deposited at three sites in the volcanic valley of the Mexico City is presented. Currently geotechnical studies assume that compressibility of granular materials decreases in depth due to the lithostatic load. That means that the deeper the sample the more rigid is supposed to be, this assumption should be demonstrated by a decreased Compression Index (Cc) in depth. Studies indicate that Mexico City clays exhibit brittle behaviour, and have high water content, low shear strength and variable Cc values. Furthermore, groundwater withdrawal below the city causes a differential decrease in pore pressure, which is related to the physical properties of granular materials (hydraulic conductivity, grain size distribution) and conditions of formation. Our results show that Cc for fine grain materials (lacustrine) can be vertically variable, particularly when soils and sediments are the product of different volcanic materials. Lateral and vertical variations in the distribution of the fluvio-lacustrine materials, especially in basins with recent volcanic activity, may be assessed by Cc index variations. These variations can also be related to differential deformation, nucleation and propagation of fractures and need to be considered when modelling land subsidence.

Reconstruction of a paleotemperature record from 0.3–3.7ka for subtropical South China using lacustrine branched GDGTs from Huguangyan Maar

Abstract The concentrations of glycerol dialkyl glycerol tetraethers (GDGTs) in catchment soils, suspended particulate matter (SPM), lake bottom sediments, and sediment cores from Huguangyan Maar, subtropical South China, were investigated. The distribution of isoprenoid GDGTs has GDGT-0/crenachaol > 2 and therefore the widely used TEX 86 is precluded from being used for the calculation of lake water temperature in this lake. The total concentration of branched GDGTs (br-GDGTs) in the soils, SPM, and lake bottom sediments ranged from 91.3–223.7 ng/g, 17.8–41.4 ng/L, and 864.2–2008.6 ng/g, respectively. The molecular composition of br-GDGTs, MBT values (methylation of br-GDGTs), and CBT values (the cyclization ratio of br-GDGTs) in the catchment soils differ from those in lake materials. This difference indicates that br-GDGTs in the lake are largely produced in situ . Based on the global lake-specific MBT/CBT–MAT (mean air temperature) calibration, the air temperature was reconstructed for lacustrine material in Huguangyan Maar. The estimates fall in the range 23.2–23.8 °C, similar to the average value of local MAT for the preceding 45 years. The paleotemperature history of Huguangyan Maar was reconstructed using br-GDGTs extracted from a sediment core spanning the period 0.3–3.7 ka, and ranged from 24.6 to 26.3 °C. The temperature pattern of Huguangyan Maar based on the global lake-specific MBT/CBT–MAT resembles those recorded in East China using numerous indicators. The pattern consists of five cool and four warm periods, including two distinct phases within the Medieval Warm Period (900–1300 AD), the coldest temperature in the Little Ice Age (1550–1850 AD) and reveals even finer temperature variations than other indicators. This new method based on br-GDGTs, produced in situ in the subtropical lacustrine environment, provides a new sensitive and precise paleotemperature proxy for lacustrine sediments for which other GDGT-based proxies are not applicable.

Helping Cities Manage Stormwater Runoff: A Day in the Life of Bill Shuster

Helping Cities Manage Stormwater Runoff: A Day in the Life of Bill Shuster

Holocene subaqueous paleoseismology of Lake Tahoe

Gravity-flow deposits recovered in a suite of sediment cores in Lake Tahoe were examined to determine if the event deposits were triggered by strong shaking from earthquakes on active faults within and in close proximity to the Lake Tahoe Basin. The acoustic character and distribution of individual lacustrine deposits as well as potential source regions were constrained by high-resolution seismic Chirp reflection and multibeam bathymetric data. Between 14 and 17 Holocene event deposits have been identified in Lake Tahoe, and examination of their source areas suggests they originated from different initiation points along the steep margin, with some being synchronous around the basin, as opposed to flood-related deposits. Lithologic characteristics, magnetic susceptibility, carbon and nitrogen isotopic signatures, opal content, and 14 C dating indicate that these event deposits are reworked lacustrine material. Radiocarbon dates indicate that the emplacement of these event deposit sediments correlates well with the late Holocene paleoseismic earthquake record developed for the Tahoe Basin. When taken alone, the causality of these events may appear ambiguous, but when the evidence is examined comprehensively, it suggests that strong shaking may likely have been the primary trigger for many of the event deposits observed in the lake throughout the Holocene. For example, four event deposits are assigned to Tahoe Basin faults. The most recent earthquakes occurred on the Incline Village fault (between 630 and 120 cal. yr B.P.); the southern segment of the West Tahoe fault (between 4510 and 4070 cal. yr B.P.); on the central and northern segments of the West Tahoe fault (5600–5330 cal. yr B.P.); and on the West Tahoe fault (between 7890 and 7190 cal. yr B.P.). The oldest of the four associated Tahoe Basin events coincides with the beginning of an extended period when Lake Tahoe was likely not spilling or spilling intermittently, and this suggests that active faulting and footwall uplift cut off the outlet at this time, exaggerating drought conditions downstream. Likewise, the event between 5600 and 5330 cal. yr B.P. on the West Tahoe fault may have exaggerated a smaller drought reflected downstream in Pyramid Lake. This event may also be the most recent event (MRE) on the largest segment of the West Tahoe fault. If correct, the period since the last rupture is approximately twice the estimated average recurrence interval for the Rubicon segment of the West Tahoe fault. A more complete Holocene record of strong shaking greatly extends the paleoseismic record in the region and indicates a combined recurrence interval of between 750 and 800 yr for all faults in the region.

Local soil knowledge and management of Anthrosols: A case study in Teoloyucan, Mexico

The irrigation district “Los Insurgentes” was established within the region of Lake Zumpango as a means to control frequent flooding events in Mexico City during the 70s, and as reception area for recharging the subsoil moisture and the development of agricultural land. Nonetheless, the irrigation district mostly stored sewage, and all of the dredged saline lacustrine material was placed on parcels adjacent to the lake burying the original soils. Since then, the farmers have significantly influenced the formation of soil on their lands through wastewater managements. The objectives were to establish the influence of management practices on soil properties, and to determine how the addition of lacustrine sediment, wastewater and amendments are reflected in both local and scientific soil classification. A soil survey was carried out taking into account the local soil knowledge, and soil management and irrigation practices information were obtained through interviews. Also physical and chemical analyses were conducted. The main contributions of farmers to the reclamation of saline soil with low agricultural productivity include the use of wastewater, the use of differing irrigation frequencies with various crops and materials added to existing soil, and the appropriate combination of amendments (manure and soils). These soil management's strategies have strongly modified the soil properties which are now expressed as different anthropogenic horizons (hydragric, terric, and hortic). They are now classified as Anthrosols. This case study shows how human beings are able to adapt to degraded environments and to produce knowledge and strategies for transforming their surrounding landscape.

Shells and other Marine Material from Tikal

Las excavaciones en Tikal, Petén, Guatemala, han producido una gran cantidad de material marino y lacustre. Todo el material marino tuvo que ser importado desde Tikal, un sitio navegable.

Development and Rainfed Paddy Soils Potency Derived from Lacustrine Material in Paguyaman, Gorontalo

Rainfed paddy soils that are derived from lacustrine and include of E4 agroclimatic zone have many unique properties and potentially for paddy and corn plantations. This sreseach was aimed to: (1) study the soil development of rainfed paddy soils derived from lacustrine and (2) evaluate rainfed paddy soils potency for paddy and corn in Paguyaman. Soil samples were taken from three profiles according to toposequent, and they were analyzed in laboratory. Data were analyzed with descriptive-quantitative analysis. Furthermore, assessment on rainfed paddy soils potency was conducted with land suitability analysis using parametric approach. Results indicate that all pedon had evolved with B horizons structurization. However, pedon located on the summit slope was more developed and intensely weathered than those of the shoulder and foot slopes.The main pedogenesis in all pedons were through elluviation, illuviation, lessivage, pedoturbation, and gleization processes. The main factors of pedogenesis were climate, age (time) and topography factors. Therefore, P1 pedons are classified as Ustic Endoaquerts, fine, smectitic, isohypertermic; P2 as Vertic Endoaquepts, fine, smectitic, isohypertermic; and P3 as Vertic Epiaquepts, fine, smectitic, isohypertermic. Based on the potentials of the land, the highest of land suitability class (LSC) of land utilization type (LUT) local paddy was highly suitable (S1), while the lowest one was not suitable with nutrient availability as the limiting factor (Nna). The highest LCS of paddy-corn LUT was marginally suitable with water availability as the limiting factor (S3wa), while the lower LSC was not suitable with nutrient availabily as the limiting factor (Nna). Keywords: Corn, lacustrine, land suitability, paddy, rainfed paddy soil

Mineralogical effect on the pozzolanic reactivity of a Mexican lacustrine soil

Clay minerals have been used as natural pozzolans with the aim of reducing CO 2 emissions, and densifying the matrix with hydration products in pastes and mortars. This study assesses the pozzolanic reactivity of a natural lacustrine material in its natural and thermally-treated states. The influence of mineralogical characteristics on the physicochemical and mechanical properties of pastes and mortars with a level of replacement of 20% was evaluated. Studies of crystallography, chemical analysis, morphology, mineralogical phases, particle size distribution and enthalpy were conducted. The results indicate that thermally-activated systems have better structure and develop a more homogeneous matrix. It was observed that poorly-crystalline mineralogical impurities do not influence the pozzolanic reactivity; moreover, the PAI (pozzolanic reactivity index) was in the order 86.59% in mortar systems including thermally-treated material, which is a much higher value when compared to only 41.92% obtained when the material was in its natural state.

A late Holocene paleoclimatic history of Lake Tanganyika, East Africa

A nearshore core (LT03-05) from the north basin of Lake Tanganyika provides diatom, pollen, and sedimentary time series covering the last ca. 3800 yr at 15–36 yr resolution. A chronology supported by 21 AMS dates on terrestrial and lacustrine materials allows us to account for ancient carbon effects on 14C ages and to propose refinements of the region's climatic history. Conditions drier than those of today were followed after ca. 3.30 ka by an overall wetting trend. Several century-scale climate variations were superimposed upon that trend, with exceptionally rainy conditions occurring 1.70–1.40 ka, 1.15–0.90 ka, 0.70–0.55 ka, and 0.35–0.20 ka. Around 0.55–0.35 ka, during the Spörer sunspot minimum, drier conditions developed in the northern Tanganyika basin while more humid conditions were registered at Lakes Victoria and Naivasha. This indicates significant variability in the nature and distribution of near-equatorial rainfall anomalies during much of the Little Ice Age.

Redistributed lacustrine detritus as a spatial subsidy of biological resources for soils in an Antarctic dry valley

We have characterised the distribution of lacustrine detritus stranded around a lake in a small Antarctic dry valley associated with fluctuations in lake level, quantified the wind-blown detritus presumed to have derived from lacustrine detritus and collected in sediment traps, and characterised samples of the detritus. Our aim was to understand better the processes responsible for transferring resources between lakes and the soils in Antarctic dry valleys. Stranded lacustrine detritus formed approximately parallel concentric lines identifiable to at least 37 m from the lake edge consistent with fluctuations in lake level having contributed to it having been stranded above the lake level. This detritus had δ 13C and δ 15N signatures characteristic of lacustrine material. It showed a trend of declining potential decomposition rate, measured in a laboratory bioassay after addition of water, with increasing horizontal distance from the present lake, consistent with the highest strandlines representing the oldest material. The amount of wind-blown detritus collected in sediment traps placed up to 80 m from the lake edge was equivalent to a gross mean flux of 306 mg organic C m − 2 year −1 and 32 mg total N m − 2 year − 1 . The amounts of wind-blown detritus organic C and total N were greatest furthest from the lake, however, because the detritus was collected in interception traps we cannot estimate the amount that would have been further redistributed. This intercepted detritus also had δ 13C and δ 15N signatures characteristic of lacustrine material and there was no trend in potential decomposition rate with distance from the lake. However, after addition of water, wind-blown detritus decomposed faster than the detritus from the strandlines, consistent with its decomposition having been arrested by desiccation. These observations suggest that inputs of organic resources of lacustrine origin, including possibly viable organisms carried with the detritus, make a localized spatial subsidy of biological resources for soil microbial communities in Antarctic dry valleys and thereby represent a trophic link between sites of primary production and indigenous soil heterotrophs.

Clay minerals as provenance indicators in continental lacustrine sequences: the Leza Formation, early Cretaceous, Cameros Basin, northern Spain

AbstractVariations in clay mineral assemblages, changes in Kübler index (KI), and the chemical composition of chlorites are used to identify source areas in the lacustrine materials in the Lower Cretaceous Leza Limestone Formation of the Cameros Basin, northern Spain. This formation has fairly homogeneous lithological characteristics and facies associations which do not allow for identification and characterization of local source areas. The Arnedillo lithosome of the Leza Limestone Formation contains a clay mineral association (Mg-chlorite, illite and smectite) indicative of its provenance. Chlorite composition and illite KI values indicate that these minerals were formed at temperatures higher than those reached by the Leza Formation which indicates its detrital origin. The similarity in the Mg-chlorite composition between the Arnedillo lithosome and the Keuper sediments of the area indicates that these materials acted as a local source area. This implies that Triassic sediments were exposed, at least locally, at the time of deposition of the Leza Formation. The presence of smectite in the Leza Formation is related to a retrograde diagenesis event that altered the Mg-chlorites in some samples.

The effects of a crude oil spill on microbiological indices of soil biological quality

The effects of a crude oil spill and remediation on the biological quality of an agricultural soil were examined based on three microbiological indices: microbial biomass carbon (MBC), dehydrogenase activity (DHA) and microbial metabolic diversity (MMD). The soils in both contaminated and uncontaminated plots were clay loam Gleyed Rego Black Chernozems developed from lacustrine materials overlying till. The four remedial treatments consisted of: meadow bromegrass (Bromus biebersteinii. Rohman and Schult), alfalfa (Medicago sativa L. ‘Algonquin’), fallow with wheat straw incorporation (SF) and unamended fallow (UFSP). An unamended fallow on adjacent uncontaminated land served as a control (UFCON). The spill had a statistically significant, negative effect on MBC and MMD (P = 0.01 and 0.05, respectively). Although a negative effect on DHA was not significant (P = 0.05), the results show evident trends. The forage treatments were, overall, significantly more effective than the SF treatment in restoring soil biological quality in hydrocarbon contaminated soil to control levels. Based on overall trends only, bromegrass had the greatest effect on soil biological quality relative to the UFSP, followed by alfalfa. The incorporation of wheat straw did not significantly affect any of the examined microbial indices. Key words: Crude oil contamination, soil microbial biomass, dehydrogenase activity, microbial metabolic diversity, soil biological quality

Estudio sedimentar10 del neogeno de la subcuenca de Alcolea de Calatrava (Ciudad Real, España)

The sub-basin of «Alcolea de Calatrava~ (Ciudad Real, Spain) is composed exclusively of Neogene and Quaternary deposits, the first consisting of detrital, palustrine and lacustrine materials, notably influenced by the volcanism of the region (volcanism of «Campo de Calatrava»). These Neogene materials have been arranged in three informal stratigraphic units: detrital, carbonate and detrital-carbonate; which follows one another in a gradual way except the latter, limited underneath by a discontinuity related to volcanic collapses. Altogether these units represent a sedimentary succession which starts with the accumulation of alluvial fan deposits that evolve laterally and vertically to marshy sediments with more or less subaerial exposure features and finally to lacustrine sediments of small extent, which correspond to ancient ponds installed inside the depressions formed by volcanic collapses. The important mammal locality of «Las Higueruelas » is located in one of these depressions.

Role of Soil Joints in Causing Bluff Erosion Along the Lake Erie Shoreline, Northeast Ohio

Bluff erosion along the Lake Erie shoreline in Ohio is a major environmental problem causing extensive damage to homes, agricultural land, and lakeshore roads. The most extensive erosion takes place in areas where the bluffs are made of well-jointed, overeonsolidated, glacial till material (CL; ML-CL) that is overlain by lacustrine silts (ML) or silty clays (CL). In order to investigate the effect of soil joints on bluff erosion, four sites, all characterized by the presence of well-developed joints, were selected between Painesville, Ohio, and the Ohio-Pennsylvania border. The detailed line survey technique was used to measure orientations and other aspects (continuity, spacing, surface features, aperture, nature of infilling material, presence or absence of water) of the joints at the four sites. Erosion rates were monitored on a bi-weekly basis for a period of one year, using equally spaced pegs on the bluff face. Photographs were taken frequently to aid in monitoring of bluff erosion. Results indicate that bluff erosion in the study area is greatly influenced by the presence of joints in the glacial till. The joints enhance erosion by providing pathways for water movement in both horizontal and vertical directions which, in turn, leads to widening of the joint openings and piping of the overlying silty material. The buildup of pore pressure along the joints, after a prolonged rainfall or a sudden snowmelt, also contributes to bluff instability. In the toe area, wave attack results in the formation of notches, cavities, and concave zones. Erosion at the bluff toe, accelerated by soil joints, initiates block falls and planar slides along the pre-existing joint surfaces above the toe area. The slump and flow type failures that occur in the overlying lacustrine material are a consequence of the joint-promoted failures in the underlying till. Thus, any remedial measures that are undertaken to minimize bluff erosion along Lake Erie must take into account the effect of soil joints.