shear strength of compacted soil under infiltration condition landslides in residual soil slopes are commonly induced by rainfall infiltration these residual soils are typically in an unsaturated state with negative pore water pressures or matric suctions since the groundwater tables in steep slopes are often deep the net normal and shear stresses of the soil remain essentially constant during rainwater infiltration into the slope failure of the slope during rainfall can be primarily associated with the decrease in the matric suction of the soil the objective of the study was to investigate the strength and deformation characteristics of a residual soil of the bukit timah granitic formation during infiltration that leads to slope failure there were two modified direct shear apparatuses used one apparatus was used for the determination of shear strength under controlled suction conditions while the other apparatus was used for shearing infiltration tests the shearing infiltration test results were compared with the shear strength values obtained from the shearing tests under constant suction the shearing infiltration test results indicate a close relationship between the decreasing matric suction and the increasing displacement rate of the soil specimen at the initial part of the infiltration process there is a rapid reduction in matric suction that is accompanied by little movement in the soil when failure of the soil is imminent the soil movement will accelerate

mechanics of upward propagation of cover collapse sinkholes cover collapse sinkholes occur by failure of the walls of a soil void above cavernous bedrock i examine conditions for failure in compression by crack propagation and coalescence and for failure by sloughing in which pore water pressure produces a net tension perpendicular to the wall of the void compressive failure without relaxation of stress does not explain observed long term stability of thick soils nor failures in thin residual soils if stress relaxation occurs with compressive failure soil voids tend to stabilize and sinkholes are not predicted sloughing failure is not predicted for steady state pore pressure fields even for a perched water table at the surface over a drained void transient pore pressure conditions that could produce sloughing may result from 1 rapid drawdown causing soil consolidation and transient high pore pressure gradients 2 approach of a wetting front in unsaturated soil with high permeability behind the front 3 dissolution of air from bubbles in the soil and exsolution near the void producing a low permeability zone near the void

glaucony and sequence stratigraphy a conceptual framework of distribution in siliciclastic sequences abstract detailed analysis of recent literature on glaucony and selected case studies eocene isle of wight miocene northern apennines shows that the presence of glaucony alone is not diagnostic of a specific systems tract of a depositional sequence a reliable sequence stratigraphic interpretation of glaucony bearing units requires additional information on glaucony including 1 spatial distribution 2 maturity distinction between nascent slightly evolved evolved and highly evolved glaucony and 3 genetic attributes differentiation of autochtonous from allochthonous and intrasequential from extrasequential glaucony autochthonous glaucony is common at various stratigraphic levels in the transgressive systems tract tst and the lower highstand systems tract hst showing an upward increase tst and then decrease hst in abundance and maturity the condensed section can be distinguished from the overlying and underlying deposits by the higher concentration and maturity of glaucony allochthonous intrasequential parautochthonous glaucony can be present in the entire tst hst and lowstand systems tract lst generally showing lower concentration and maturity than its autochthonous counterpart allochthonous extrasequential detrital glaucony is present mainly in the lst its concentration and composition depending on the characteristics of the source horizon the associa ion between autochthonous and allochthonous intrasequential and extrasequential glaucony commonly exists in the lst and in the lower tst

de glauconiarum origine the glauconitic facies is widespread on present day continental shelves from 50 s to 65 n and at water depths between 50 and 500 m and is in particularly great abundance on the upper slope and outer shelf between 200 and 300 m it is also common in many ancient rocks of post late precambrian age it occurs as sand to pebble sized essentially green particles granular facies but also as a surface coating on particles and hardgrounds and as a diffuse impregnation film and diffuse facies we suggest the replacement of the term glauconite which has been interchangeably used to designate a morphological form and a specific mineral by glaucony facies and glauconitic smectite and glauconitic mica as end members of the glauconitic mineral family the widely accepted model of burst and hower for glauconitization requires a degraded micaceous 2 1 layer lattice structure parent clay mineral however detailed analysis of numerous samples of recent glaucony reveals that such a parent substrate is exceptional the model therefore requires modification generally the parent material is carbonate particles argillaceous kaolinitic faecal pellets infillings of foraminiferal tests various mineral grains and rock fragments that pass gradually into the commonly occurring green grains we show that the process of glauconitization is achieved by de novo authigenic growth of automorphous crystallites in the pores of the substrate accompanied by progressive alteration and replacement of the substrate it is this two fold evolution that causes the verdissement of granular substrates macrofossils and hardgrounds the authigenic mineral is an iron rich and potassium poor glauconitic smectite while new smectites are growing into the remaining pore space the earlier smectites are modified by incorporation of potassium producing decreasingly expandable minerals with a non expandable glauconitic mica as the end member this mineralogical diversity of the glauconitic mineral family explains the highly variable physical and chemical properties of glaucony four categories nascent little evolved evolved and highly evolved glaucony are distinguished glauconitization appears to be controlled by a delicate balance between degree of physical confinement of a particle and the amount of ionic exchange between the micro environment and ambient open marine sea water the optimum conditions for glauconitization are those of semi confinement as a result the interior of a grain is more glauconitized than its less confined periphery similarly for identical substrate types large grains 500 m provide more favourable substrates for glauconitization than lesser confined small grains on a larger scale the formation of glaucony is governed by the availability of iron and potassium and the balance between detrital influx and winnowing low accumulation rates expose grains to the open marine environment for sufficiently long times 105 106 years for highly evolved glaucony

instabilities on moraine slopes induced by loss of suction a case history in comparison with saturated conditions negative pore water pressures arising from partial saturation increase the available shear strength on a potential slip surface this additional contribution is lost progressively during infiltration of rainfall leading to instabilities sometimes before full saturation is reached in such cases reliable prediction of the safety factor may be achieved by taking the suction history of the soil into account a combination of field and laboratory tests was carried out recently to investigate the triggering effect of rainfall on shallow slips in alpine moraine slopes the problem is complicated by the strong heterogeneity of these soils with particle sizes varying from silts to boulders the data highlight the influence of suction on the peak shear strength and allow for the calibration of simple models which take into account the dependence of shear strength on the saturation degree an infinite slope stability analysis is performed the results are compared wit

development and morphometry of sinkholes in coastal plains of apulia southern italy preliminary sinkhole susceptibility assessment abstract evolution of coastlines in karst areas may be strongly controlled by dissolution processes which favour the development of surface and subsurface landforms the generation of caves in these environments is commonly favoured by the mixing between fresh and brackish waters the sinkholes resulting from the upward propagation of the caves may interfere with the anthropogenic environment and cause damage to human elements property and activities to highlight the often underestimated importance of karst phenomena in coastal areas we have analyzed a coastal stretch of apulia in southern italy the study area covering an extension of about 6 km 2 is situated in the ionian coast and presents several interesting karst landforms that are generally connected to caves tens of sinkholes were mapped through field surveys multi year aerial photographs dating back to the 1940s and archival research we have performed a morphometric analysis of the sinkholes the analysis describes the main parameters of the sinkholes area length width and depth and the control exerted by the main discontinuity systems in the area the detrimental effects derived from interaction between human environment and these karst landforms is also under consideration a sinkhole susceptibility map which may provide useful information for planners developers and the insurance industry has eventually been produced through application of a decision tree model

sinkhole formation mechanisms and geostatistical based prediction analysis in a mantled karst terrain abstract efforts to evaluate sinkhole formation and quantify the controlling factors are hindered by the lack of historical observations or coarse resolution datasets in many areas we applied recent advances in gis based sinkhole mapping and spatial statistics to comprehensively investigate the factors controlling sinkhole formation in the mantled karst setting of dougherty county georgia sinkholes form at varying spatial and temporal scales within the test site a three stage methodology was conducted firstly 275 sinkholes that formed or were enlarged between 1999 and 2011 were detected by comparing the results of sinkhole inventories derived from two dems acquired in 1999 and 2011 additionally a lidar dem 1 m resolution was used to gather a spatially detailed sinkhole inventory of 3412 sinkholes the sinkhole inventory data was converted into sinkhole density maps for subsequent analyses ordinary least squares ols and geographically weighted regression gwr spatial statistical models were applied to quantify the impact of controlling factors on sinkhole density controlling factors included geologic hydrologic anthropogenic hydrogeologic and geomorphologic variables for the two sinkhole inventory datasets analyzed overburden thickness aquifer fluctuations and proximity to fractures streams and wetlands were the most influential controlling factors on sinkhole formation gwr p values

the glauconite fe illite fe smectite problem a critical review iron silicate minerals are a significant component of sedimentary systems but their modes of formation remain controversial our analysis of published data identifies end member compositions and mixtures and allows us to recognize controls of formation of different mineral species the compositional fields of glaucony fe illite fe al smectites are determined in the m 4si vs fe sum of octahedral cations m interlayer charge solid solutions could exist between these phases the fe al and fe rich clay minerals form two distinct solid solutions the earliest phases to be formed are fe al smectites or berthierine depending on the sedimentation rate reductive microsystems appear in the vicinity of organic debris in unconsolidated sediments the fe is incorporated first in pyrite and then in silicates after oxidation potassium ions diffuse from the sea water sediment interface if not interrupted the diffusion process is active until reaction completion is reached i e formation of fe illite or glauconite or a mineral assemblage berthierine nontronite according to the available al ion amounts in the microsystem mixed layer minerals are formed when the diffusion process is interrupted because of sedimentation compaction or cementation despite the common belief of their value as palaeoenvironment indicators these minerals can form in a variety of environments and over a period of millions of years during sediment burial

a review on natural and human induced geohazards and impacts in karst karst environments are characterized by distinctive landforms related to dissolution and a dominant subsurface drainage the direct connection between the surface and the underlying high permeability aquifers makes karst aquifers extremely vulnerable to pollution a high percentage of the world population depends on these water resources moreover karst terrains frequently underlain by cavernous carbonate and or evaporite rocks may be affected by severe ground instability problems impacts and hazards associated with karst are rapidly increasing as development expands upon these areas without proper planning taking into account the peculiarities of these environments this has led to an escalation of karst related environmental and engineering problems such as sinkholes floods involving highly transmissive aquifers and landslides developed on rocks weakened by karstification the environmental fragility of karst settings together with their endemic hazardous processes have received an increasing attention from the scientific community in the last decades concurrently the interest of planners and decision makers on a safe and sustainable management of karst lands is also growing this work reviews the main natural and human induced hazards characteristic of karst environments with specific focus on sinkholes floods and slope movements and summarizes the main outcomes reached by karst scientists regarding the assessment of environmental impacts and their mitigation

sinkholes in italy first results on the inventory and analysis the italian geological survey apat carried out field surveys and analysis of collapse phenomena sinkholes in italy the main goal of the project is to collect geological geomorphological geochemical and hydrogeological data about the sinkhole prone areas in italy in order to develop a spatial database of the characteristics of each phenomenon the preliminary results of this study provide information on the distribution geological setting and monitoring and remediation actions associated with these natural collapses in italy many italian regions are affected by these natural disasters some of them are caused by karst collapses or anthropic activity however some occur in areas characterized by buried carbonate bedrock up to 190 m as well as by peculiar geological structural and geochemical scenarios in these areas it is not reasonable to ascribe the formation mechanism to karst activity instead these types of cavities quickly develop in terrains with a variable granulometry often in connection with upwelling fluids in this work some natural specific cases have been studied in order to define the relationships between the geology regional tectonic elements mineral spring waters and strong gas vents and the genesis of the sinkholes a first attempt of sinkhole classification is also presented

mg rich ferric illite in marine transgressive and highstand systems tracts examples from the paleoproterozoic semri group central india this paper focusses upon two glauconitic sandstones in the paleoproterozoic deoland formation and chorhat sandstone both belonging to the semri group central india in both the cases glauconitic minerals occur in sandstones deposited in the marine realm within a transgressive systems tract tst for the former unit and within a highstand systems tract hst for the latter the proportion of glauconitic minerals increases in the paleo offshore direction petrography reveals selective early glauconitization of detrital k feldspars along their fringes cleavages and the fractures created by volume expansion during progressive alteration leading to the generation of peloids with small relics of the precursors xrd and mineral chemistry reveal a structure typical of glauconite and more akin to mg rich ferric illite the mineral chemistry of the glauconitic mineral phases remains the same whether the glauconitization process was incipient or at an advanced

experimental study on the critical triggering condition of soil failure in subsidence sinkholes subsidence sinkholes in karst terrain are a common geological hazard which can lead to natural disasters in the natural and built environment groundwater ingress is the main factor leading to subsidence previous research has focused on the qualitative analysis of the influence of groundwater although limited research into critical triggering conditions of groundwater has been undertaken quantitatively water seepage into soil is the starting condition in the development of subsidence sinkholes this paper focuses on testing the anti permeability strength as the critical triggering condition in the formation of subsidence sinkholes and develops a design and methodology to test its value quantitatively the methodology is applied in an industrial park of guilin china to assess the probability of forming subsidence sinkholes results indicate that there is a low susceptibility to the formation of subsidence sinkholes under current conditions in the ground truth investigation

unusual seawater composition of the late cretaceous tethys imprinted in glauconite of narmada basin central indiaunusual seawater composition of the late cretaceous tethysu bansal et al a detailed investigation of a glauconite bed within the late cretaceous bryozoan limestone formation of the bagh group in central india as well as the study of existing records reveals the existence of a glauconitic sea along the margins of the palaeo tethys ocean during the late cretaceous epoch the authigenic green mineral formed abundantly on shallow seafloors unlike in its modern deep sea counterpart we present an integrated petrographical geochemical and mineralogical investigation of the glauconite within late cretaceous transgressive deposits to highlight its unique geochemistry with moderate fe 2 o 3 and high al 2 o 3 sio 2 mgo as well as k 2 o contents x ray diffractional parameters identify the evolved to high evolved nature of the glauconite while mossbauer spectroscopic study reveals the dominance of fe 3 compared to fe 2 in the atomic structure the rare earth elements ree pattern of glauconite reveals moderate light ree heavy ree lree hree fractionation and weak negative eu anomaly the ce anomaly of the glauconite indicates a sub oxic diagenetic condition we propose that late cretaceous glauconites formed within a shallow marine depositional setting across the tethyan belt because of enhanced supply of k si al fe mg cations through continental weathering under the extant greenhouse climate

postfailure mechanics of landslides laboratory investigation of flowslides in pyroclastic soils of all landslides subaerial flowslides are the most dangerous according to the literature flowslides in saturated granular deposits are caused by static liquefaction induced by loss of stability however the catastrophic flowslides that occurred on steep slopes in campania southern italy in 1998 1999 and 2005 were triggered by rainwater infiltration into shallow deposits of pyroclastic soils which were initially unsaturated starting from the experience collected during the investigations of some of these landslides the writers consider flowslide evolution as a result of a mechanical chain process characterized by saturation increase due to rainwater infiltration mechanical degradation volumetric collapse and static liquefaction culminating in complete fluidization of the soil in the paper this chain process is investigated through wetting tests both in suction controlled triaxial apparatuses and in a well equipped small scale slope model

late cretaceous elasmobranch palaeoecology in nw europe late cretaceous elasmobranch faunas are known from numerous of nw europe localities but their palaeoecological characteristics are still poorly known recent studies on anglo paris basin elasmobranch faunas from phosphatic chalks provided detailed data on the taxonomic composition of these communities results based on multiproxy analyses suggest peculiar conditions for cenomanian faunas with numerous lamniforms and rare nectobenthic taxa indicative of dysoxic conditions changes in turonian faunal composition correlate with a maximum in palaeotemperatures and transgressive environmental conditions the northern coniacian glauconitic palaeoenvironment provided cooler and shallow environments suitable for a few species with probable migration patterns a model is proposed to explain the ecological features of the santonian campanian faunas in which the habitat heterogeneity is the main factor controlling elasmobranch diversity and evenness the dominance of small sized species in santonian campanian faunas is similar to the patterns observed in modern upwelling environments low beta diversity of early campanian faunas suggests that although faunas were from disjunct upwelling erosional channels the number of such palaeoenvironments provided a wide range of habitats allowing species to migrate depending on local ecological conditions the santonian campanian global cooling is synchronous with changes in faunal compositions larger scale palaeoecological palaeoenvironmental and palaeogeographical patterns are proposed based on comparisons with a number of other nw europe elasmobranch faunas

paleoceanography of the eastern indian ocean from odp leg 121 drilling on broken ridge broken ridge in the eastern indian ocean is overlain by about 1 600 m of middle cretaceous to pleistocene tuffaceous and carbonate sediments that record the oceanographic history of southern hemisphere mid to high latitude regions prior to about 42 ma broken ridge formed the northern part of the broad kerguelen broken ridge plateau during the middle eocene this feature was split by the newly forming southeast indian ocean ridge since then broken ridge has drifted north from about 55 to 31 s the lower part of the sedimentary section is characterized by turonian to santonian tuffs that contain abundant glauconite and some carbonate the tuffs record a large but apparently local volcanic input that characterized the central part of broken ridge into the early tertiary maestrichtian shallow water several hundred to 1 000 m depth limestones and cherts accumulated at some of the highest rates ever documented from the open ocean 4 to 5 g cm 2 10 3 yr 1 a complete with all biostratigraphic zones cretaceous tertiary boundary section was recovered from site 752 the first 1 5 m y of the tertiary is characterized by an order of magnitude reduction in the flux of biogenic sediments indicating a period of sharply reduced biological productivity at 55 s following which the carbonate and silica sedimentation rates almost reach the previous high values of the latest cretaceous we recovered a complete section through the paleocene that contains all major fossil groups and is more than 300 m thick perhaps the best pelagic paleocene section encountered in ocean drilling about 42 ma broken ridge was uplifted 2 500 m in response to the intra plateau rifting event subsequent erosion and deposition has resulted in a prominent eocene angular unconformity atop the ridge an oligocene disconformity characterized by a widespread pebble layer probably represents the 30 ma sea level fall the neogene pelagic ooze on broken ridge has been winnowed and thus its grain size provides a direct physical record of the energy of the southern hemisphere drift current in the indian ocean for the past 30 m y

constraining sub seismic deep water stratal elements with electrofacies analysis a case study from the upper cretaceous of the maloy slope offshore norway abstract electrofacies represent rock facies identified from wireline log measurements and allow extrapolation of petrophysical characteristics away from stratigraphic intervals that are calibrated to core this approach has been employed to reduce uncertainty in the identification of the sub seismic depositional elements in the late cenomanian coniacian succession of the northern maloy slope offshore norway core logging permits identification of eleven distinct sedimentary facies that are grouped into four facies associations fa a turbidite sandstones fa b heterolithic siltstones and sandstones fa c debrites and fa d slide and slump deposits each facies association is defined by a distinct combination of petrophysical characteristics including porosity density gamma ray sonic and resistivity using neural network analysis electrofacies are calibrated with sedimentary facies thereby allowing us to map their thickness and stacking patterns within the studied deep water succession we demonstrate that this approach is particularly useful where the presence of glauconite makes the distinction between sandstone from shale rich units difficult using gamma ray logs alone our results indicate that the succession of interest is dominated by debris flows and slide and slump deposits which are commonly poorly imaged on seismic reflection datasets in the northern north sea the methodology presented here can aid the correlation of deep water stratal elements at production and exploration scales in stratigraphic successions that have undergone similar burial histories furthermore this method may help in the identification of mass flow deposits that are present in upper cretaceous deep water systems of the north sea

the problem of glaucony from the shannon sandstone campanian wyoming terra nova 23 100 107 2011 abstract the shannon sandstone one of the most controversial units in the field of stratigraphy was first interpreted as a shelf sand ridge deposit but subsequent studies have furnished different interpretations from lowstand shoreface to incised valley models despite a general consensus among previous workers about the significance of glaucony for shannon interpretation mineralogical characterization of the green grains has never been undertaken identification of glaucony has been restricted to visual inspection accurate characterization of highly glauconitic deposits from the shannon sandstone powder river basin of wyoming section w3 reveals that sedimentological interpretation of the greensands relies mostly upon mistaken mineral identity glaucony appears as a minor component of the rock and proves to be poorly mature and significantly less abundant 0 6 than previously inferred up to 85 characterization of the glauconitic minerals however provides data that contribute to shannon interpretation

biogeochemical effects of atmospheric oxygen concentration phosphorus weathering and sea level stand on oceanic redox chemistry implications for greenhouse climates abstract understanding the key factors influencing the global oceanic redox system is crucial to fully explaining the variations in oceanic chemical dynamics that have occurred throughout the earth s history in order to elucidate the mechanisms behind these variations on geological timescales numerical sensitivity experiments were conducted with respect to the partial pressure of atmospheric molecular oxygen p o 2 the continental shelf area a cs and the riverine input rate of reactive phosphorus to the oceans r p the sensitivity experiment for atmospheric p o 2 indicates that pervasive oceanic anoxia and euxinia appear when p o 2 p o 2 are higher than a previous estimate of 50 pal present atmospheric level due to redox dependent phosphorus cycling the sensitivity experiment regarding the shelf area demonstrates that changes in the shelf area during the phanerozoic significantly affected oceanic oxygenation states by changing marine biogeochemical cycling a large continental shelf acts as an efficient buffer against oceanic eutrophication and prevents the appearance of ocean anoxia euxinia we also found that an enhanced r p is an important mechanism for generation of widespread anoxia euxinia via expansion of both the oxygen minimum zone and coastal deoxygenation although the critical r p value depends significantly on p o 2 a cs and the redox dependent burial efficiency of phosphorus at the sediment water interface our systematic examination of the oceanic redox state under cretaceous greenhouse climatic conditions also supports the above results

sedimentology and palaeogeography of the regressive transgressive kurnub group early cretaceous of jordan abstract the early cretaceous kurnub group of jordan consists of three regressive transgressive fluvial marine depositional sequences in northern jordan recorded here for the first time whereas continental clastics dominated central and southern jordan deposition of the kurnub group started in the late neocomian above a regional angular unconformity by basal conglomerate and sandstone facies association of an alluvial braidplain origin during this time the tethys seaway was located to the north and northwest of jordan which afterwards during the barremian advanced in a south and southeastward direction flooding north jordan and giving rise to a tidal flat coastal swamp sequence following a subsequent regression of the sea unconfined braidplain deposits covered the area the most extensive transgression of the tethys inundated the region during the late aptian and early albian where a mixed siliciclastic carbonate sequence with interbedded inner shelf carbonates and tidal marsh coastal swamp black shales and lignites was deposited the next and last regression took place in the middle albian where a thin meandering river clastic sequence was deposited finally shallow marine sedimentation resumed over the region during the remaining time of the kurnub group which at the same time prepared for the subsequent regional cenomanian transgression upon comparison with global eustatic curves these three incursions of the tethys sea in jordan are to a great extent in accordance with the global sea level fluctuations the various formations of the kurnub group and their informal units that are established here for the first time can readily be correlated with equivalent deposits in adjacent countries the distribution of the shorelines of the barremian aptian and albian on both sides of the dead sea transform offers new evidence for 100 km northward displacement of the arabian plate against the sinai palestine plate

upper cretaceous sequence stratigraphy of the galala plateaux western side of the gulf of suez egypt abstract based on the study of lithology biostratigraphy and analysis of facies this study deduces the occurrence of nine third order upper cretaceous cenomanian maastrichtian depositional sequences which are bounded by eleven sequence boundaries of geographic extent in the galala plateaux situated along the western side of the gulf of suez egypt some of the recorded sequence boundaries e g cenomanian turonian turonian coniacian intra santonian and campanian maastrichtian sequence boundaries are not yet confirmed to eustatic sea level changes fourteen main mixed carbonate siliciclastic facies associations were recognized on a lateral transition between inner to outer ramp settings with apparent subsidence towards the south the tectonic position of the galala plateaux played an important role in the profound complexity of facies changes and the configuration of depositional sequences representing variable time gaps

properties and durability assessment of glauconitic sandstone a case study on zamel sandstone from the bohemian cretaceous basin czech republic abstract green sandstones from the eastern part of the bohemian cretaceous basin represent the traditional stone cutting material used in the region of eastern bohemia since the 14th century sandstones of the cenomanian age are shallow water marine sediments dominated by pores over 5 m in size the green colour of the sandstone is caused by a content of glauconite with a high proportion of fe 3 in the structure which is very stable under oxidative open air conditions a typical feature of this rock is its rapid absorption and humidity exchange rates between the rock and its immediate environment by vaporization as well as good thermal stability up to temperatures of approximately 550 c the rock is resistant to weathering if recommended conditions are observed when used in construction the rock can be used in external architecture as well as in interiors of modern buildings the data about the properties and stability of the rock published in this paper will serve as a basis for a historical structural survey of buildings for searches of authentic stone deposits for the preservation and restoration of buildings and as a recommendation for conservation work

glaucony from the cretaceous of the sierra de guadarrama central spain and its application in a sequence stratigraphic context detailed sedimentological and geochemical analyses of upper cretaceous glaucony bearing deposits from the middle portion of the castro de fuentiduena formation in central spain enable identification of a multiphase history of glaucony accumulation despite its relatively high maturity k2o 7 glaucony from the transgressive subtidal sandstones has anomalously low concentration in the host rock generally 10 suggesting remobilization from a different source the remarkable thickness of the glaucony bearing horizons concurrently with concentration of glaucony in laminae small size and high degree of roundness and sorting provide further evidence for an allochthonous origin of the green grains in contrast authigenic glaucony from the overlying offshore clays exhibits higher abundance up to 45 and lower maturity k2o 7 and is interpreted to have formed in situ allochthonous glaucony originally developed in more distal areas during a prolonged period of sediment starvation the green grains were then swept away from their place of origin and concentrated into tidal bars and channels within the upper transgressive systems tract of the third order depositional sequence maximum concentration of autochthonous glaucony is recorded at the transition from tidal influenced to offshore deposits this glaucony which is relatively less evolved due to lower time available for maturation is interpreted to reflect the turnaround from transgressive to highstand conditions marking the condensed section of the depositional sequence as postulated by previous sequence stratigraphic models this study documents that allochthonous glaucony can be widespread throughout the transgressive systems tract tst while the condensed section cs typically hosts autochthonous glaucony contrary to the existing literature however this study shows that glaucony from the tst may be even more mature than glaucony from the cs if enough time for maturation during transgression is allowed before the ultimate concentration of the green grains identification of spatial and temporal characteristics of glaucony thus is critical to a reliable sequence stratigraphic interpretation of the glaucony bearing deposits

the influence of urbanization of sinkhole development in central pennsylvania the karsted limestone valleys of central pennsylvania contain two populations of sinkholes solution sinkholes occur in the champlainian limestone units along the margins of the valleys solution sinkholes are permanent parts of the landscape and although a nuisance to construction do not present other problems the second population is the suffosional or soil piping sinkholes these occur on all carbonate rock units including the beekmantown and gatesburg dolomites that comprise the two principal carbonate aquifers in the valley suffosional sinkholes are the principal land use hazard suffosional sinkholes are transient phonomena they occur naturally but are exacerbated by runoff modifications that accompany urbanization suffosional sinkholes are typically 1 5 2 5 m in diameter depending on soil thickness and soil type the vertical transport of soil to form the void space and soil arch that are the precursors to sinkhole collapse is through solutionally widened fractures and cross joints and less often through large vertical openings in the bedrock the limited solution development on the dolomite bedrock combined with soil thickness seldom greater than 2 m limits the size of the sinkholes all aspects of suffosional sinkhole development are shallow processes transport piping void and arch formation and subsequent collapse take place usually less than 10 m below the land surface factors exacerbating sinkhole development include pavement street and roof runoff which accelerates soil transport such seemingly minor activities as replacing high grass and brush with mowed grass is observed to accelerate sinkhole development dewatering of the aquifer is not a major factor in this region

age and origin of albian glauconites and associated clay minerals inferred from a detailed geochemical analysis abstract glauconitic grains are abundant in sandstones and siltstones from albian and cenomanian transition between lower and upper cretaceous formations of southeastern france morphological and crystal chemical data show that the green grains can be considered as glauconite s s with minute amounts of pyrite dolomite calcite and other clay minerals as grain coatings or crack fillings glauconite grains formed early during sedimentation generally from detrital chlorite biotite or clay particles and were found scattered together with other detrital mineral phases muscovite quartz in the silt in which porosity was considerably reduced afterwards by four stages of carbonate calcite dolomite cementation geochemical data especially the fe u and ce contents of the glauconitic grains strongly suggest increasing oxidizing conditions with time in the sedimentation environment the detailed geochemical analyses also allow the pristine glauconite grains to be distinguished from the other clay minerals occurring in the sequence this enabled k ar and rb sr dating of the glauconitic material which yields identical results of 97 9 0 4 and 97 9 3 5 ma respectively these dates point to a synsedimentary origin for the glauconites during the late albian about 97 98 ma the k ar data also indicate that the albian cenomanian boundary should be placed at 96 0 1 9 ma the similarity between the k ar and rb sr ages precludes any further significant pervasive recrystallization of these minerals during burial of the sequence either by heat flux or fluid flow the k ar study of the clay matrix from the same siltstones suggests synsedimentary precipitation of additional clay minerals probably together with the glauconite grains such as mixed layer illite smectite identified in the clay size fraction of the sedimentary succession

subsidence rates and urban damages in alluvial dolines of the central ebro basin ne spain in the central ebro basin alluvial dolines develop on quaternary materials overlying neogene evaporites this process is very active analysing aerial photographs of different years important differences can be observed since the 1970s when the urbanisation of the area took place karst processes have damaged many buildings and infrastructures from the dates of construction and the repair of a number of buildings and pavements we calculate subsidence rates 12 120 mm year moreover we decided to monitor for around 4 years three dolines developed on urban areas to determine their subsidence behaviour a water level device with an error of 2 3 mm was utilised for this purpose the subsidence rates so obtained are 64 5 39 and 21 mm year which fit with the previous data from repaired zones

detecting compositional spatial and temporal attributes of glaucony a tool for provenance research abstract a reliable interpretation of glaucony bearing units requires the characterization of compositional spatial and temporal attributes of glaucony the criteria that can readily determine the differentiation of the various types of glaucony autochthonous parautochthonous or allochthonous intrasequential and detrital or allochthonous extrasequential are discussed in detail autochthonous vs allochthonous glaucony may be often detected on the basis of detailed sedimentological investigations including facies interpretation of glaucony bearing deposits and careful examination of spatial distribution of glaucony textural and morphological features although generally not diagnostic on their own provide a significant contribution to glaucony interpretation the distinction between parautochthonous and detrital glaucony can be sometimes performed by radiometric dating more commonly it requires that compositional attributes of glaucony be matched against those of putative sources glauconies from distinct parent rocks generally have different maturity and carry unique geochemical and mineralogical fingerprints that may contribute definitive data for provenance research previous work on glaucony and examples from units formed in tectonically stable areas cretaceous eocene deposits of paris basin and hampshire basin and active tectonic basin settings miocene strata of southern alps and northern apennines provide the opportunity to discuss the validity of the proposed criteria across different structural domains and emphasize the need for an integrated approach to the study of glaucony

non pelletal glauconite from the campanian qusseir formation egypt implication for glauconitization abstract glauconitization processes proposed in the literatures include the layer lattice theory in which glauconite formed through k uptake by a detrital smectite precursor and the neoformation theory that does not require a smectite like precursor the non pelletal glauconite bed in the uppermost part of the campanian qusseir formation at the abu tartur area and the underlying smectite rich beds provided a potential example for the glauconitization process the glauconite occurs as fine clayey moderately hard and homogeneous bed ranges in thickness from 2 to 3 m under the optical microscope glauconite occurs in a unique morphology as very fine green clayey matrix which differs from the typical pelletal shape of many glauconites under the scanning electron microscope it appears as dense uniform and very fine flakes that are composed of si al fe and k x ray diffraction analysis of both bulk samples and clay fractions indicates that the glauconite bed is composed entirely of glauconite geochemical analysis suggested that the investigated glauconites belong to the 2nd stage of the maturity scale i e moderate maturity or they can be alternatively ranked as evolved chondrite normalized ree patterns exhibit lree enrichment relative to hree la yb n ratios vary from 5 to 8 and slightly negative eu anomalies eu eu from 0 7 to 0 8 clay beds that underlie the glauconite bed are composed of two types of smectites smectite of low k 2 o and fe 2 o 3 contents and smectite of high k 2 o and fe 2 o 3 contents smectite of low k 2 o and fe 2 o 3 contents is considered in this study as the initial precursor of glauconite while smectite of high k 2 o and fe 2 o 3 represents the transitional phase between smectite and glauconite this in turns supports the layer lattice theory in which glauconite formed by k diffusion to a detrital smectite precursor from the sea water due to transgression absence of mixed layer minerals suggests that the diffusion process was active and continuous until reaction completion was reached i e formation of glauconite maturity and ree patterns suggest the possible formation of the studied glauconite probably at shelf environment at approximately 100 m water depth the occurrence of glauconite indicates a marine invasion of the upper part of the qusseir formation which was considered previously as non marine sediments

syndepositional shallow water precipitation of glauconitic minerals abstract numerous studies have demonstrated that glauconitic minerals predominantly form in water depths of mid shelf to upper slope in modern oceans these areas tend to have slow sedimentation rates another commonly cited requisite for glauconitic mineral precipitation cambro ordovician strata from the southwestern us are rich in glauconitic minerals stratigraphic sedimentological and petrographic constraints indicate that the glauconitic minerals are autochthonous in marked contrast to the modern environments of deposition these cambro ordovician strata formed under very shallow water to tidal flat conditions the trough cross stratified deposits of the most glauconitic mineral rich accumulations glaucarenites indicate a high energy environment and probably a normal to high rate of sedimentation the presence of fibroradiated rims of glauconitic minerals on glauconitic mineral pellets echinoderm fragments and quartz grains demonstrates that the cambro ordovician glauconitic minerals precipitated on or in close proximity to the sea floor and prior to calcite precipitation consequently glauconitic minerals must have formed under markedly different conditions in the lower paleozoic than they do today thus the occurrence of glauconitic minerals in the rock record cannot be used a priori as an environmental indicator of either mid shelf and deeper water and or a slow rate of sedimentation

a three dimensional back analysis of the collapse of an underground cavity in soft rocks abstract the assessment of stability of man made underground caves excavated in the past and later on abandoned represents a serious challenge for land and urban planning operations especially for the areas of possible interaction of the caves with overlying structures and infrastructures several areas of southern italy are characterized by the presence of abandoned underground quarries for the extraction of soft calcarenite rocks which now threatens the overlying environment due to the risk of collapse and the consequent generation of sinkholes this work presents a back analysis of a sinkhole occurred in 2011 in the town of marsala caused by the collapse of an underground quarry as a representative case study of these phenomena based on the available geometrical and geological dataset as well as the field observations of the phenomenon in this article the assumptions and the results about the genesis of the 2011 sinkhole as derived from a three dimensional finite element back analysis aimed at reconstructing the stress strain evolution that brought to the ground failure collapse is discussed in particular the 3 d numerical analyses have been performed in order to identify the factors responsible of the genetic mechanism of the sinkhole the finite element analysis has been carried out by accounting for the geotechnical characterization of the marsala calcarenites derived from both specific laboratory tests performed on samples taken from the site and literature data available on the same rock material the numerical results have been then validated by means of the comparison with field observations and also compared with those achieved through a 2 d model of the same case study

facies analysis and sequence stratigraphy of the cenomanian turonian mixed siliciclastic carbonate sediments in west sinai egypt abstract the unconformity bounded cenomanian turonian succession in west sinai is subdivided into three formations the raha abu qada and wata these rock units were deposited in a mixed siliciclastic carbonate system on a ramp setting the studied ramp only includes inner and mid ramp facies whereas the outer ramp facies occurs in northern sinai four sequence boundaries sb were recognized in the studied formations due to the presence of subaerial exposure or flooding events in the facies stacking pattern the first and last sequence boundaries sb1 and sb4 might be considered as type 1 sequence boundary attributable to the presence of widespread erosion it is difficult to determine type of the second and third sequence boundaries sb2 and sb3 because of their minor unconformity and minimal erosion determination of systems tracts within the wata formation is debatable owing to the action of dolomitization that has destroyed both original components and sedimentary structures the lowstand systems tracts of the recorded sequences are characterized by sandstones siltstones and sandy shales while fossiliferous shale and limestone with oysters prevailed during sea level rise the highstand systems tracts are generally characterized by shallow intertidal and subtidal deposits that are made up of abundant oyster wackestones with benthic foraminifera and ostracods

karst in gypsum and its environmental impact on the middle ebro basin spain the middle ebro basin in characterised by strong evaporitic profiles from the miocene period and in which gypsum formations are predominant these groups of easy solubility produce in many areas typically karstic landforms although there are certain features specific to them the generated landforms appear on the surface as different morphological types of doline which very often develop on the alluvium deposited by the river ebro and its affluents on the agricultural land of the penaflor villamayor area the functional character of karst causes collapse dolines to appear after heavy storms and these are constantly filled in by farmers motorways and roads that cross these areas as also the industrial estates existing on the outskirts of zaragoza are affected by dissolution processes that bring about continual collapses the infiltration of water from unlined canals causes the generation of numerous dolines along canal banks

sinkholes related to discontinuous pumping susceptibility mapping based on geophysical studies the case of crestatx majorca spain the crestatx aquifer is the main source of water supply to the bay of alcudia one of the largest resorts on the island of majorca spain this water has been used since the 1970s using several pumping wells which draw an annual volume of 1 5 hm3 the seasonal exploitation of this karstic aquifer causes a substantial cone of depression with great variations in the piezometric level up to 120 m and dynamic water levels of down to 87 m below sea level at the end of the 1990s several sinkholes and subsidence depressions started being detected in a highly karstified area twenty subsidence and sinkhole morphologies have been inventoried in an area measuring 70 000 m2 with diameters up to 23 m and depth more than 15 m the intense and continuous rainfall during recent years 2008 2010 has considerably accelerated the process increasing the dimensions of existing sinkholes and the appearance of new morphologies by means of electrical tomography techniques a ground study was carried out numerous cavities have been identified in the upper 30 m using a map of the surface morphologies and the geophysical profiles we can determine that the propagation and orientation of the sinkholes lie along three main directions n30 e n130 e and n60 e the first is the most relevant which is parallel to the main tectonic structures in the area the interpretation of the electrical profiles has enabled us to identify the potentially most unstable areas which is an effective tool to assess risk in the area as there are roads and a housing development nearby the high but discontinuous exploitation of the aquifer is considered the main trigger for these sinkholes and subsidence depressions as it causes large variations of pressure and accelerates the dissolution process in the underlying rock

the role of fe on the formation and diagenesis of interstratified glauconite smectite and illite smectite a case study of upper cretaceous shallow water carbonates abstract the widespread formation of interstratified glauconite smectite gl s and illite smectite i s in modern and ancient diagenetic settings records the physicochemical conditions prevailing during clay mineral authigenesis to date however significant gaps in our knowledge persist in respect to the influence of interstitial solution chemistry temperature and reaction kinetics on the evolution of composition mineralogy and microstructure of gl s and i s herein we present a study on the reaction mechanisms and the physicochemical conditions that led to the precipitation of early diagenetic gl s and late diagenetic i s on a stable carbonate platform during the cenomanian at langenstein in the northern german basin the texture and the k ar age 95 0 1 8 ma of the green glauconitized grains revealed that green clay authigenesis progressed in initially organic rich semi confined micromilieus i e in fecal pellets and in foraminifera close to the sediment seawater interface the composition of gl s varied in the range k 0 20 0 74 na 0 0 10 ca 2 0 0 05 0 28 0 75 fe 3 0 63 1 20 fe 2 0 08 0 24 al 3 0 19 0 97 mg 2 0 29 0 52 2 01 2 12 al 3 0 09 0 35 si 4 3 65 3 91 o 10 oh 2 and depended on the rate of aqueous fe 2 and k ion diffusion the micromilieu of glauconitization and on the bulk sedimentation rate the mineralogical microstructural and chemical changes of the ongoing gl s products revealed the following reaction for green clay authigenesis at langenstein fe iii smectite reacted with monosilicic acid goethite and aqueous k mg 2 and fe 2 to form glauconite and aqueous na ca 2 and h ions this process considers complex mineral transformations commonly associated with glauconitization such as early diagenetic oxidation of organic matter and microbial catalyzed dissolution of fe oxy hydroxides carbonates and detrital silicates in contrast the k ar age of i s 68 0 1 6 ma and its compositional variability k 0 29 0 45 na 0 0 10 ca 2 0 0 06 0 30 0 55 fe 3 0 16 0 29 fe 2 0 0 10 al 3 1 37 1 68 mg 2 0 18 0 43 2 00 2 12 al 3 0 17 0 39 si 4 3 61 3 83 o 10 oh 2 indicate a burial diagenetic origin for this mineral phase rather than transformation of illitic clays into i s during weathering under warm and humid climatic conditions the results from kinetic modelling support a diagenetic origin of i s 50 60 i layers and 50 40 s layers and imply its formation by the replacement of pre existing k feldspar at high pore fluid activity k na ratios and at low fe 2 concentrations we propose that the substitution of al 3 for fe 3 fe 2 and mg 2 in the octahedral sheet shifts the stability field of the kaolinite fe al mg smectite fe al mg illite or glauconite triple point to much lower monosilicic acid activities and stabilizes the i s or gl s structure this reaction supports the idea that the bio availability of fe is the rate limiting factor for glauconitization which is not the case for the diagenetic growth of i s whereby the pore water fe 2 concentration may be limited by the competing formation of fe oxy hydroxides and or fe sulfides

single cycle cratonic quartzarenites produced by tropical weathering the nimar sandstone lower cretaceous narmada basin india abstract the world wide turonian marine transgression is represented by a thin a few tens to a few hundreds of metres thick mixed siliciclastic carbonate sequence deposited in the narmada basin presently located across the precambrian shield in central india the area was part of the interior of gondwana in the cretaceous when major changes were initiated leading to the break up of the supercontinent in the absence of any sedimentary record it is difficult to say what happened in the area between the precambrian and the early cretaceous the sandstone petrofacies of the cretaceous sequence of the narmada basin were studied with a view to understanding the nature of the basin and its tectonic setting during an important event which took place on a global scale the studied sandstones are generally quartzarenites composed mainly of several varieties of quartz and some mica rock fragments feldspar and heavy minerals derived from the underlying precambrian basement for the study of provenance of the sandstones in the light of plate tectonics the present study employed the qt f l and qm f lt triangular diagrams of dickinson on the qt f l plots 78 of the studied samples lie in the craton interior field and 22 of the samples lie in the recycled orogen field on the qm f lt plots most samples fall in the craton interior field 75 another 25 fall in the quartzose recycled field the texturally sub mature to immature locally derived quartz rich sandstones do no represent a typical stable platform succession they were derived from uplifted basement and deposited in the nearby narmada rift the ancient humid tropical climate and long residence time in the soil horizon produced quartz rich sands

a southern hemisphere record of global trace metal drawdown and orbital modulation of organic matter burial across the cenomanian turonian boundary ocean drilling program site 1138 kerguelen plateau despite its assumed global nature there are very few detailed stratigraphic records of the late cenomanian to the early turonian oceanic anoxic event 2 from the southern hemisphere a highly resolved record of environmental changes across the cenomanian turonian boundary interval is presented from ocean drilling program site 1138 on the central kerguelen plateau southern indian ocean the new data lead to three key observations firstly detailed biostratigraphy and chemostratigraphy indicate that the record of oceanic anoxic event 2 is not complete with a hiatus spanning the onset of the event a decrease in glauconite and highly weathered clays after the onset of oceanic anoxic event 2 marks the end of the hiatus interval which can be explained by a relative sea level rise that increased sediment accommodation space on the kerguelen plateau margin this change in depositional environment controlled the timing of the delayed peak in organic matter burial during oceanic anoxic event 2 at site 1138 compared with other oceanic anoxic event 2 locations worldwide a second key observation is the presence of cyclic fluctuations in the quantity and composition of organic matter being buried on the central kerguelen plateau throughout the latter stages of oceanic anoxic event 2 and the early turonian a close correspondence between organic matter sedimentary elemental compositions and sediments recording sea floor oxygenation suggests that the cycles were mainly productivity driven phenomena available age control points constrain the periodicity of the coupled changes in sedimentary parameters to ca 15 to 50 ka suggesting a link between carbon burial and astronomically forced climatic variations precession or obliquity in the southern hemisphere mid latitudes both during and after oceanic anoxic event 2 fluctuations that were superimposed on the impact of global scale processes finally trace metal data from the non sulphidic black shale unit at site 1138 provide the first evidence from outside of the proto north atlantic region for a global drawdown of seawater trace metal mo inventories during oceanic anoxic event 2 this article is protected by copyright all rights reserved

the formation of cover collapse sinkholes in north of hamedan iran abstract most sinkholes in the hamedan region central plain in western iran are developed in partially unconsolidated sediments overlying oligo miocene limestone analyses of hydrologic and hydrogeologic conditions from 1988 to 2008 show that conditions were favourable for sinkhole development these sinkholes developed in groundwater discharge areas near the base of karstic oligo miocene limestone in zones with major groundwater circulation thick overburden and a close proximity to deep source carbon dioxide gas high carbon dioxide partial pressures caused by rising gases from pneumatolytic and hydrothermal phase sources renew the aggressiveness of the water in the vicinity of the discharge zone the acidic water dissolves limestone especially along the fractures and joints moreover the presence of large conduits below the surface allows for the transport of unconsolidated sediments and the continual development of sinkholes

shannon sandstone in wyoming a shelf ridge complex reinterpreted as lowstand shoreface deposits abstract the shannon sandstone campanian of wyoming was formerly interpreted as two stacked shelf ridge complexes sand was believed to have been transported from a time equivalent shoreline 110 150 km to the west and reworked or molded into ridges at the depositional site we show that this time equivalent shoreline section at lucerne wyoming consists of not one shoreface sandbody but two superimposed they are both storm dominated and the lower one terminates in beach facies capped by root traces there must have been a rise in relative sea level of at least 14 m to make accommodation space for the second shoreface sandbody in the salt creek area and the adjacent subsurface teapot dome there are two sandier upward facies successions in the lower succession there are abrupt vertical acies contacts between offshore bioturbated sandstones thicker hummocky cross stratified sandstones and coarser cross bedded sandstones there is also evidence that the cross bedded sandstones rest erosively on underlying facies the trace fauna in the sandstones includes macaronichnus segregatis rosselia socialis and ophiomorpha the m segregatis suggests a foreshore or upper shoreface depositional environment and r socialis indicates a lower to middle shoreface neither are characteristic of a shelf ridge complex the abrupt and probably erosive facies contacts along with the trace fauna suggest that the cross bedded sandstones in this succession represent a shoreface deposit that formed during a stage of actively falling relative sea level overlyi g muddy bioturbated sandstones indicate that shoreface deposition was terminated by a transgression the upper sandier upward succession contains facies and trace fauna similar to those of the lower succession and is also interpreted as a prograding shoreface rather than the sand moving 110 150 km from the shoreline and then being molded into shelf ridge complexes at salt creek we suggest that the shoreline moved into the salt creek area as the result of a fall in relative sea level it was transgressed and moved back westward a second fall of relative sea level moved the shoreline back to salt creek and a final transgression terminated shannon deposition

paleoredox variations in ancient oceans recorded by rare earth elements in fossil apatite abstract rare earth element concentrations in biogenic apatite of conodonts fish debris and inarticulate brachiopods were determined in over 200 samples from cambrian to modern sediments tests for experimental bias caused by the chemicals used to separate fossils from the rock matrix and for interlaboratory interexperiment or interspecies related variations clearly show that no resolvable fractionation of ree occurs incorporation of ree in biogenic apatite of recent fish debris occurs near the sediment water interface soon after deposition and reflects characteristics of seawater the original ree signature apparently survives subsequent burial and diagenesis cerium variations in fish debris from modern environments are controlled by redox potential ce is fractionated by co precipitation with metallic oxides under oxidizing conditions this fractionation produces a negative ce anomaly ce anom in seawater that is reflected in the sedimented fish debris conversely no fractionation of ce occurs under reducing conditions resulting in ce concentrations that are normal to enriched in anoxic seawater and fish debris deposited under local or basinwide anoxic conditions extrapolation of observations of the redox control of ce anom in modern oceans to fossil apatite indicates that anoxic conditions were prevalent in lower paleozoic and lower triassic oceans whereas in the upper paleozoic the world ocean was generally oxidizing

sinkhole susceptibility mapping using the analytical hierarchy process ahp and magnitude frequency relationships a case study in hamadan province iran abstract since 1989 an increasing number of sinkhole occurrences have been reported in the kabudar ahang and razan qahavand subcatchments krq of hamadan province western iran the sinkhole related subsidence phenomenon poses a significant threat for people and human structures including sensitive facilities like the hamadan power plant groundwater over exploitation from the thick alluvial cover and the underlying cavernous limestone has been identified as the main factor involved in sinkhole development a sinkhole susceptibility model was produced in a gis environment applying the analytical hierarchy process ahp approach and considering a selection of eight factors each categorized into five classes distance to faults df water level decline wld groundwater exploitation ge penetration of deep wells into karst bedrock pka distance to deep wells ddw groundwater alkalinity ga bedrock lithology bl and alluvium thickness at relative weights were preliminarily assigned to each factor and to their different classes through systematic pairwise comparisons based on expert judgment the resulting sinkhole susceptibility index ssi values were then classified into four susceptibility classes low moderate high and very high susceptibility subsequently the model was refined through a trial and error process involving changes in the relative weights and iterative evaluation of the prediction capability independent evaluation of the final model indicates that 55 and 45 of the subsidence events fall within the very high and high susceptibility zones respectively the results of this study show that ahp can be a useful approach for susceptibility assessment if data on the main controlling factors have sufficient accuracy and spatial coverage the limitations of the model are partly related to the difficulty of gathering data on some important geological factors due to their hidden nature the magnitude and frequency relationship constructed with the 41 sinkholes with chronological and morphometric data indicates maximum recurrence intervals of 1 17 2 14 and 4 18 years for sinkholes with major axial lengths equal to or higher than 10 m 20 m and 30 m respectively

a transgressive storm and fair weather wave dominated shelf sequence cretaceous nimar formation chakrud madhya pradesh india abstract the lithologic assemblage of the cretaceous nimar formation in the area around chakrud madhya pradesh india has been classified in five marine facies a polymictic conglomerate resting on granite basement largely representing a lag deposit b coarse grained pebbly sandstone with normal and reverse coarse tail grading and also frequency grading c sandstone with alternate hummocky cross stratified and small scale wave rippled units d mudstone and e limestone facies c bears the definite stamp of alternations between storm and fair weather waves probable parameters of the fair weather waves have been determined from the grain size and morphometric parameters of the wave ripples the depth of the generation of the wave corresponds to a modern mid shelf region facies b shows gradational contact with facies c and was deposited shoreward above fair weather wave base bed shear stresses calculated from variable grain size parameters within individual cross laminae indicate that the nature of the current that deposited the pebbly sands was similar to that of storm currents it has been postulated that storm ebb surges initially moved as fluid gravity flows pushing ahead the bed loads and eventually turned into density currents farther offshore carrying most of the sediment in suspension the other two facies d and e were deposited largely below storm wave base the overall fining upward sequence reflects gradual deepening of the basin local aberrations in the facies sequence as represented by short phase coarsening upward sequences suggest temporary reversals of this trend

the distinctive compositional evolution of glauconite in the cretaceous ukra hill member kutch basin india and its implications abstract an integrated study involving sedimentology mineral chemistry and spectroscopy highlights a distinctive compositional evolution of cretaceous glauconite within the ukra hill member glauconite occurs at the top part of transgressive systems tract deposits built on a marine shelf the concentration of glauconite steadily increases towards the maximum flooding surface maximizing around 50 and sharply falls at the onset of progradation unlike most phanerozoic examples ukra glauconite forms by the variable degree of replacement of quartz feldspar and mica grains xrd feg sem and spectroscopy of glauconite pellets indicate an evolved stage of maturation mossbauer spectroscopy reflects a minor substitution of al3 fe3 total in tetrahedral sites and significant substitution of the same in octahedral sites a consistently high value of k2o as well as fe2o3 contradicts the two popular theories layer lattice and verdissement and support replacement origin of glauconite in a high asi and high ak pore water environment incipiently formed glauconite records a marginal increase in k2o content accompanied by release of al2o3 and sio2 to form evolved glauconite pellets those forming within quartz grains involve an addition of fe2o3 total content during maturation the minimal increase in k2o content of incipiently formed glauconite best exhibited by those formed within quartz grains is possibly related to stratigraphic condensation compositional evolution like this is exhibited by precambrian glauconites involving abiotic substrates but is unusual for the phanerozoic original k2o and fe2o3 total content of glauconites is reduced around peripheries and fractures during diagenesis adding to compositional variability

sequence stratigraphic significance of sedimentary cycles and shell concentrations in the aitamir formation albian cenomanian kopet dagh basin northeastern iran abstract albian cenomanian siliciclastic shallow marine sediments of the aitamir formation kopet dagh basin northeastern iran form strongly asymmetric fining coarsening upward cycles which are interpreted as recording changes in relative sea level deepening shallowing cycles these cycles correspond to depositional sequences in which deposits of the lowstand systems tract are not present the sequence boundary coinciding with the transgressive surface shell concentrations are found in distinct positions within the depositional sequence as transgressive lags at the base of the transgressive systems tract tst in the maximum flooding zone mfz and at or close to the top of the highstand systems tract hst they are dominated by bivalves mainly oysters and or ammonites and differ from each other in a number of stratigraphic sedimentologic palaeoecological and taphonomic features such as species diversity preservation quality orientation percentage of disarticulation and degree of biogenic alteration characteristic features of concentrations at the base of the tsts are moderate time averaging distinct basal erosional surface sorting a chaotic to preferred convex up orientation and nearly total disarticulation of shells they are suggestive of an environment in which reworking and local transport was frequent events similar features are shown by concentrations near the tops of the hsts except that the shells were largely concentrated in lenses rather than in beds as in the transgressive lags associated sedimentary structures indicate deposition above fair weather wave base in a high energy environment concentrations occurring in the mfz in contrast are autochthonous and highly time averaged having accumulated during times of low rates of sedimentation below storm wave base this is supported by their high preservation quality comparatively high percentage of articulated shells shells of infaunal organisms commonly preserved in life position high glauconite content and biogenic alteration being the most important taphonomic features

sinkholes subsidence and subrosion on the eastern shore of the dead sea as revealed by a close range photogrammetric survey abstract ground subsidence and sinkhole collapse are phenomena affecting regions of karst geology worldwide the rapid development of such phenomena around the dead sea in the last four decades poses a major geological hazard to the local population agriculture and industry nonetheless many aspects of this hazard are still incompletely described and understood especially on the eastern dead sea shore in this work we present a first low altitude our analysis reveals a kilometer scale sinuous depression bound partly by flexure and partly by non tectonic faults the estimated minimum volume loss of this subsided zone is 1 83 106 m3 with an average subsidence rate of 0 21 m yr 1 over the last 25 years sinkholes in the surveyed area are localized mainly within this depression the sinkholes are commonly elliptically shaped mean eccentricity 1 31 and clustered nearest neighbor ratio 0 69 their morphologies and orientations depend on the type of sediment they form in in mud sinkholes have a low depth to diameter ratio 0 14 and a long axis azimuth of nne ne in alluvium sinkholes have a higher ratio 0 4 and are orientated nnw n from field work we identify actively evolving artesian springs and channelized sediment laden groundwater flows that appear locally in the main depression consequently subrosion i e subsurface mechanical erosion is identified as a key physical process in addition to dissolution behind the subsidence and sinkhole hazard furthermore satellite image analysis links the development of the sinuous depression and sinkhole formation at ghor al haditha to preferential groundwater flow paths along ancient and current wadi riverbeds

a multicriteria approach to karst subsidence hazard mapping supported by weights of evidence analysis soil subsidence collapse is a major geohazard occurring in karst regions it occurs as suffosion or dropout sinkholes developing in the overburden overlying karst less frequently it corresponds to a breakdown of karst void ceiling i e collapse sinkhole this hazard can cause significant engineering challenges therefore decision makers require the elaboration of methodologies for reliable predictions of such hazards e g karst subsidence susceptibility and hazards maps planning strategies priority areas for detailed investigations this study aims at developing a methodological framework for the evaluation of potential conditioning factors controlling the occurrence of sinkholes in a context of limestone karst potential conditioning factors are first determined based on underlying physical processes for different geological contexts barren and mantled karsts then the relevance of each factor is evaluated against a set of representative karst subsidence locations using the weight of evidence theory and relevant factors are tested for independence relevant and independent factors are finally weighed and combined together i e superimposed to achieve karst subsidence susceptibility models the best model i e the one showing the highest predictability is determined by a receiver operating characteristic roc curve analysis which is performed using a set of independent and representative karst subsidence locations the method is applied to one case study where mantled karst setting prevails val d orleans south of paris results show higher susceptibility in mantled karst with significant role of the overburden lithology presence absence of low permeability layer and position of the karst piezometric surface within the overburden the limited area of barren karst shows a low susceptibility although this approach was developed for a specific karst context it can easily be replicated in other karst contexts e g interstratal karst chalk or evaporitic karsts which are known to be highly susceptible to karst subsidence even if some of the conditioning factors will be different

stability analyses of rainfall induced landslides the slope stability issues concerning rainfall induced slope failures are investigated and presented specifically the effect of both negative and positive pore water pressures on the stability of initially unsaturated slopes are carefully explained and coupled with infinite slope analysis methods in order to present a predictive formulation of slope failures that occur as a result of rainfall events the formulation serves as a baseline analysis method for evaluating potentially unstable soil slopes that are subject to surface infiltration and explains the various triggering mechanisms that may occur based on individual combinations of the slope geometry soil strength and infiltration parameters a procedural method is outlined for utilizing the analytical formulation to predict the change in the factor of safety for a slope subject to infiltration and a detailed analysis of a case study is presented to verify the method quantitative statements are made concerning the time and depth of failure in relationship to the soil slope and rainfall parameters

evolution and extinction of maastrichtian late cretaceous cephalopods from the lopez de bertodano formation seymour island antarctica one of the most expanded records to contain the final fortunes of ammonoid cephalopods is within the lopez de bertodano formation of seymour island james ross basin antarctica located at 65 south now and during the cretaceous this sequence is the highest southern latitude onshore outcrop containing the cretaceous paleogene k pg transition we present comprehensive new biostratigraphic range data for 14 ammonite and one nautiloid species based on the collection of 700 macrofossils from high resolution sampling of parallel sedimentary sections dated maastrichtian to earliest danian in age across southern seymour island we find evidence for only a single abrupt pulse of cephalopod extinction at the end of the cretaceous when the final seven ammonite species disappeared consistent with most evidence globally in the lead up to the k pg extinction in the james ross basin starting during the campanian ammonite diversity decreased overall but the number of endemic taxa belonging to the family kossmaticeratidae actually increased this pattern continued into the maastrichtian and may be facies controlled linked to changes in sea level and seawater temperature during the early maastrichtian ammonite diversity dropped significantly with only two species recorded from the basal lopez de bertodano formation on seymour island the subsequent diversification of endemic taxa and reappearance of long ranging widespread species into the basin resulted in an increase in ammonite diversity and abundance during the mid maastrichtian this was coincident with an apparent period of warming temperatures and sea level rise interpreted from palynology and sedimentology perhaps reflecting a high latitude expression of the mid maastrichtian event late maastrichtian diversity levels remained stable despite reported climatic and environmental variation ammonite diversity patterns during the maastrichtian parallel those of microfossil species such as nannofossil and planktonic foraminifera suggesting that dynamic climatic and environmental changes affected many planktonic and nektonic organisms during the latest cretaceous however we suggest that these perturbations had a minimal effect on overall diversity prior to the catastrophic extinction event at the k pg boundary

the role of hydrogeology in solution subsidence development and its environmental impacts a case study for sazlica nigde turkey solution subsidence and other types of collapse failures developed in the vicinity of sazlica have been a major source of environmental problems such as groundwater pollution soil erosion and foundation failures extensive pumping of water from the lake dipsiz during irrigation seasons creates landslide developments at the shores of the lake five stages of landslide development were observed in the unconsolidated soils around lake dipsiz bowl shaped solution subsidence features with depths from 1 to 3 m and diameters between 1 and 60 m were formed due to excess pumping and recharge and discharge features of unconfined aquifer the pumping activities must be controlled to prevent further environmental problems lake dipsiz and other subsidence developments are the groundwater exposure areas highly vulnerable to contamination the proposed remedies for overcoming the environmental problems are the establishment of conservation areas around such natural features ceasing the removal of top soil controlling the urbanization and keeping the livestock farming away from the areas susceptible to pollution

evaluating and comparing methods of sinkhole susceptibility mapping in the ebro valley evaporite karst ne spain abstract multiple sinkhole susceptibility models have been generated in three study areas of the ebro valley evaporite karst ne spain applying different methods nearest neighbour distance sinkhole density heuristic scoring system and probabilistic analysis for each sinkhole type separately cover collapse sinkholes cover and bedrock collapse sinkholes and cover and bedrock sagging sinkholes the quantitative and independent evaluation of the predictive capability of the models reveals that 1 the most reliable susceptibility models are those derived from the nearest neighbour distance and sinkhole density these models can be generated in a simple and rapid way from detailed geomorphological maps 2 the reliability of the nearest neighbour distance and density models is conditioned by the degree of clustering of the sinkholes consequently the karst areas in which sinkholes show a higher clustering are a priori more favourable for predicting new occurrences 3 the predictive capability of the best models obtained in this research is significantly higher 12 5 82 5 than that of the heuristic sinkhole susceptibility model incorporated into the general urban plan for the municipality of zaragoza although the probabilistic approach provides lower quality results than the methods based on sinkhole proximity and density it helps to identify the most significant factors and select the most effective mitigation strategies and may be applied to model susceptibility in different future scenarios

late cretaceous transgression on a cimmerian high neka valley eastern alborz iran a geodynamic event recorded by glauconitic sands abstract in the neka valley eastern alborz iran glaucony bearing marine sediments of early middle santonian age directly overlie palaeozoic to triassic units deformed during the eo cimmerian orogenic event late triassic the upper cretaceous open marine sediments were deposited on a flat surface lacking any evidence of pedogenesis the geochemical and morphological features of glaucony grains which characterize the base 1 to 1 5 m of the upper cretaceous succession indicate an autochthonous origin of the highly evolved glaucony denoting a long lasting period of low sedimentation rate the development of glaucony in the observed stratigraphic position is indicative of a rapid drowning of the former cimmerian relief that cannot be explained by a eustatic rise alone the palaeo depth needed for the development of glaucony and for the presence of the observed bathyal foraminifera assemblages is greater than the maximum eustatic excursion documented in the cretaceous the occurrence of glaucony in this stratigraphic position reflects thus an important episode of increased subsidence rates related to a geodynamic event framed in a time interval of major plate reorganization in the complex puzzle of the iranian plates the subsidence event that caused the development of the glauconitic horizon in the neka valley could likely represent the effect of a santonian stage of the complex and long lasting story of the opening of the caspian sea

model of seawater composition for the phanerozoic we present an inverse model of phanerozoic seawater com position calibrated against updated paleoseawater compositions from fluid inclusions in marine halites the model considers step wise alteration of seawater composition via 1 variable input of river water 2 variable rates of alteration of seawater through reactions at mid ocean ridges and 3 variable rates of alteration of seawater through reactions on ridge flanks and across the ocean floor in general the model achieves agreement with paleoseawater fluid inclusion data for na 1 c a 2 1 s o 4 2 2 and k 1 particularly when variable runoff is considered variable rates of basalt seawater interactions at both ridges and ridge flanks are required to understand the evolution of seawater particularly the observed near constant concentration of k 1 through time

anatomy and origin of a cretaceous phosphorite greensand giant egypt late cretaceous epicontinental phosphorites porcelanites cherts dark coloured shales glauconitic sandstones and bioclastic and fine grained carbonate rocks in egypt are examined in terms of their overall depositional and diagenetic framework and stable isotopic and organic geochemical characteristics two main depositional realms are interpreted and correlated through sequence stratigraphic analysis 1 a shallow hemipelagic environment accompanying initial stages of marine transgression and conducive to the formation of organic carbon rich shales biosiliceous sediments and thick phosphorites and 2 a relatively high energy depositional regime accompanying sea level fall during which deltas advanced glauconites were reworked seaward and prograding oyster banks became periodically exposed to episodes of fresh water diagenesis thereby promoting solution collapse phenomena in associated cherts lenticular to massive phosphorites are viewed as the result of current winnowing and concentration of authigenic grains initially precipitated in associated reducing shales and biosiliceous sediments in eastern egypt the phosphorites form winnowed lag layers some of which may have been redeposited down slope in structural lows in the west these sands were concentrated into giant phosphorite sand waves built by reworking of penecontemporaneously deposited phosphatic muds during marine transgression carbon isotopic results substantiate interpretations from modern deposits for limitation of phosphate mineral precipitation with depth in sediments as a result of lattice poisoning however direct desorption of phosphorus to pore waters from detrital iron oxyhydroxide phases also may have been important in the cretaceous setting the iron reduced in this process being available for incorporation in glauconites the main locus for authigenic glauconite precipitation appears to be where iron fluxes from regions of lateritic weathering were highest and near the boundary between oxygenated and reduced waters this study suggests a model for the common coexistence of glauconites and phosphorites in the geological record although upwelling is often advocated as the origin of nearly all giant phosphorite deposits we suggest that some of these may have been strongly influenced by fluvially derived phosphorus borne on particulates and desorbed from these compounds upon flocculation and or reduction in bottom waters or pore waters

dimorphism and a new record of barroisiceras de grossouvre ammonoidea from the coniacian of bagh central india barroisiceras de grossouvre was hitherto unknown in india b onilahyense basse which elsewhere belongs exclusively to the coniacian has been recorded from the bryozoan limestone formation of central india this find as well as the presence of another time diagnostic coniacian ammonite placenticeras kaffrarium etheridge and two inoceramid bivalves inoceramus mytiloides incertus jimbo and i platyceramus mantelli barrois mercey in the underlying horizons help in resolving the long standing problem of the age of the bagh group b onilahyense shows wide intraspecific variability and overlaps morphometrically with the late turonian type species b haberfellneri hauer they may be conspecific the present species has been found to be sexually dimorphic a phenomenon previously not well recognised in the subfamily barroisiceratinae as in many late cretaceous ammonites dimorphism is manifest mainly by differences in relative adult sizes and in strength of ornamentation the microconch being sma

origin and sequence stratigraphic implications of high alumina glauconite within the lower quartzite vindhyan supergroup abstract an integrated field petrographical and geochemical investigation reveals a shallow marine dys oxic depositional setting for the glauconite at the top of the mesoproterozoic lower quartzite member of the vindhyan supergroup a thorough facies and paleogeographic analysis indicates a storm influenced shallow subtidal depositional condition for the glauconitic sandstone occupying the mid level of a transgressive systems tract tst deposit which is capped by the maximum flooding zone mfz the x ray diffractional parameters confirm the evolved character of the glauconite the mineral chemical analysis indicates the glauconite is enriched in k2o mgo and al2o3 and depleted in fe2o3 total compared to the phanerozoic variety it formed by the pseudomorphic replacement of the k feldspar by the addition of fe2o3 at consistently high content of k2o unlike most phanerozoic examples the elevated level of h3sio4 cl k na mg and fe possibly derived by the continental weathering and or contemporary volcanism facilitated the glauconitization process the high content of mg in the glauconite corresponds to the mg rich mesoproterozoic seawater a dys oxic depositional condition associated with a major marine flooding surface favoured the formation of glauconite while the onset of anoxic regime caused the disappearance of glauconite and the deposition of pyritiferous and carbonaceous shale in the overlying condensed zone deposits

bioevents and redox conditions around the cenomanian turonian anoxic event in central mexico abstract the xilitla section of central mexico western margin of the proto north atlantic is characterized by pelagic sediments enriched in marine organic matter using biostratigraphic and radiometric data it was dated at the latest cenomanian earliest turonian transition we identified an interval coeval with the faunal turnover associated with the oceanic anoxic event 2 oae 2 recording the heterohelix shift and the filament event for the first time in mexico an integral analysis of sedimentary facies pyrite and geochemical proxies reveals vertically variable redox conditions with prevailing anoxic to dysoxic bottom waters along with phosphorous and manganese depletion the highest content of total organic carbon and of certain redox sensitive trace elements rstes is found during part of the anoxic event confirming more uniform and constant oxygen depleted conditions this interval is also characterized by a significant enrichment in biogenic barium and elevated toc ntot ratios suggesting a link between productivity and anoxia sulfur isotope fractionation has a maximum value within the anoxic event favored by the increase in the flux of organic matter and intensified through sulfur recycling highly bioturbated beds representing short lived episodes of oxic conditions are intermittent within the oae 2 and become more frequent in the early turonian this study proposes a model similar to that of modern upwelling regions high marine productivity controlled organic matter burial and oxygenation at the seafloor varying between anoxic laminated facies with small pyrite framboids and dysoxic conditions bedding parallel bioturbated facies with inoceramid bivalves and large pyrite framboids interrupted by short term well oxygenated episodes thoroughly bioturbated facies with common benthic foraminifera general low oxygen conditions led to the formation of glauconite and pyrite bacterially mediated the enrichment of redox sensitive trace elements in sediments cd zn v and cr scavenged by organic matter and ni mo pb co and re by pyrite and resulted in mn and p depletion

applying a weighted random forests method to extract karst sinkholes from lidar data summary detailed mapping of sinkholes provides critical information for mitigating sinkhole hazards and understanding groundwater and surface water interactions in karst terrains lidar light detection and ranging measures the earth s surface in high resolution and high density and has shown great potentials to drastically improve locating and delineating sinkholes however processing lidar data to extract sinkholes requires separating sinkholes from other depressions which can be laborious because of the sheer number of the depressions commonly generated from lidar data in this study we applied the random forests a machine learning method to automatically separate sinkholes from other depressions in a karst region in central kentucky the sinkhole extraction random forest was grown on a training dataset built from an area where lidar derived depressions were manually classified through a visual inspection and field verification process based on the geometry of depressions as well as natural and human factors related to sinkholes 11 parameters were selected as predictive variables to form the dataset because the training dataset was imbalanced with the majority of depressions being non sinkholes a weighted random forests method was used to improve the accuracy of predicting sinkholes the weighted random forest achieved an average accuracy of 89 95 for the training dataset demonstrating that the random forest can be an effective sinkhole classifier testing of the random forest in another area however resulted in moderate success with an average accuracy rate of 73 96 this study suggests that an automatic sinkhole extraction procedure like the random forest classifier can significantly reduce time and labor costs and makes its more tractable to map sinkholes using lidar data for large areas however the random forests method cannot totally replace manual procedures such as visual inspection and field verification

investigation of sinkholes spatial distribution using the weights of evidence method and gis in the vicinity of karapinar konya turkey abstract there are many sinkholes 182 in the vicinity of karapinar approximately 20 large sinkholes 10 m in diameter were formed within the obruk plateau between 1970 and 2012 the formation of sinkholes is the most important geological hazard in the study area because they can damage engineering structures settlements agricultural areas and eventually be a source of casualties to date no study has been conducted on the distribution of sinkholes in this region in this study the spatial distribution of the sinkholes and the factors controlling sinkhole development were studied through the use of geographical information systems using a sinkhole inventory and a spatial database containing information on the topography geology hydrogeology and land use initially 182 sinkholes were identified in the area by examining the digital elevation model produced for this study the sinkholes were verified in the field thirty two factor maps were produced to investigate their relationship with sinkholes using the weights of evidence method the sinkholes are mainly related to dissolution of the neogene age lacustrine insuyu formation consisting of limestone and clayey limestone sinkhole frequency increases in the vicinity of drainages 2000 3000 m and faults

distinctive compositional characteristics and evolutionary trend of precambrian glaucony example from bhalukona formation chhattisgarh basin india abstract up to 20 of framework quartz and feldspar grains in wave reworked sandstones in the precambrian bhalukona formation central india are replaced by glaucony which is characterized by high k2o al2o3 mgo and low total fe2o3 content textural evidence indicates that incipient glaucony within cleavages and fractures of detrital grains evolved to pellets k2o content of glaucony remains high av 8 despite its low total fe2o3 content glaucony evolved with addition of total fe2o3 at a constant k2o during the course of maturation al2o3 was released while total fe2o3 mgo and sio2 were added to the glaucony structure glaucony originated in a high ak and high asi pore water environment by pseudomorphic replacement of grains continental weathering related supply of fe mg k and si facilitated glaucony formation in shallow marine sediments the origin evolution and geochemistry of shallow marine originated precambrian glaucony completely differ from those of their phanerozoic counterpart

unusual occurrence of glauconite in a shallow lagoonal environment lower cretaceous northern aquitaine basin sw france some minerals are considered to be representative of specific natural environments among them glauconite is considered to be formed in marine deep platform conditions however the term glauconitic is misused to designate green minerals formed in marine outer shelf environments x ray diffraction scanning electron microscopy and energy dispersive x ray analyses of individual green materials were carried out leading to the identification of glauconite in the purbeckian facies green glauconite grains predominantly occur as burrow fills and occasionally as faecal pellet replacements two depositional environments have been identified from bottom to top of the succession 1 an argillaceous dolomitic lagoonal sediment formed in saline shallow water 2 a marl limestone alternation deposited in a brackish water estuary the crystallochemical properties of the glauconites change abruptly these findings show that glauconite may form in coastal environments and not only in mid shelf to upper deep water platform environments as classically assumed moreover the glauconite composition changes with the chemical conditions imposed by the local environment

designing foundations around sinkholes there is an increasing awareness among developers and owners of the need to conduct subsurface exploration studies before planning a project the use of geophysical methods in subsurface exploration has been established to be valuable in locating sinkhole activity and suggesting pro active measures however the value of geophysical exploration to supplement geotechnical investigation has not yet been stressed primarily out of cost concerns ground penetrating radar and electrical resistivity tests which were used to determine void spaces below proposed buildings are gaining wider acceptance as a result of information obtained from geophysical tests foundation designs were modified to use post tensioned mats or to include grouting an improved grouting technique that controls the volume of grout being pumped is also discussed this paper is an attempt to document some case studies which resulted in making design improvements to mitigate the effects of known sub surface solution activity these case studies illustrate the use of geophysical exploration methods in adding value to the engineered design

substrate control on formation and maturation of glauconites in the middle eocene harudi formation western kutch india formation and maturation of glauconites within the early middle eocene harudi formation built up in a lagoon to shelf transition in western kutch india is addressed taking recourse to a combined sedimentological micropalaeontological and mineralogical investigation the glauconite is authigenic and its occurrence coincides with maximum flooding the glauconite is more matured within the fecal pellets and is less matured within the intra particle pores of bioclasts namely foraminifera ostracoda gastropoda and bryozoa sem eds xrd and geochemical studies clearly document that the infilling within the intra particle pores of bioclasts belong to nascent to slightly evolved glauconite 5 wt k2o while the pellet belongs to slightly evolved to evolved glauconite 5 7 wt k2o based on chemical characteristics and sem investigations the glauconitization process can be best explained by the verdissement theory the glauconite possibly formed as initial authigenic glauconitic smectite precipitates while the pellet matured subsequently by addition of k the process was hindered in case of infillings the maturation process also involved addition of si and release of al with or without release of mg the glauconite maturation was facilitated in case of fecal pellets because of higher porosity inter granular nature of pores and availability of necessary elements in semi confined micro environments in contrast the maturation was aborted at an early stage in case of infillings because of the minute closed nature of the pores and prevalent alkaline conditions not allowing dissolution of calcitic tests a low negative cerium anomaly suggests glauconite formation in sub oxic micro environments created by decay of organic matters within the fecal pellets and bioclasts a clear case of substratum control on glauconitization becomes apparent

responses of cover collapse sinkholes to groundwater changes a case study of early warning of soil cave and sinkhole activity on datansha island in guangzhou china in karst areas of quaternary sediments fissures and solution channels through soluble rocks provide unseen conduits for the vertical movement of surface water into the underlying karst aquifers this downward flow may also transport overburden material which can result in the formation of soil caves and ground loss called cover collapse sinkholes because of the concealed development of such soil caves and generally complicated geological conditions the prediction of soil cave development and sinkhole activity is far from perfect this study focused on the early warning of soil cave and sinkhole development by monitoring groundwater level decline based on the improved terzaghi loosening pressure theory and using excess pore water pressure two types of critical groundwater level decline are discussed the first denoted as 0 is the critical groundwater level decline related to soil cave formation and evolution the second denoted as ht is the critical groundwater level decline related to soil cave roof collapse this method of groundwater monitoring for the early warning of soil cave and sinkhole development is currently being applied on datansha island in guangzhou china

eustatic and palaeoenvironmental assessment of the mid cretaceous bathurst island group of the money shoals platform northern australia abstract the cretaceous system of the money shoals platform consists of the bathurst island group which is extensively developed on the continental borderland of northern australia the platform experienced a simple post cretaceous tectonic history and in its southern part the bathurst island group is nonconformable on precambrian basement an ideal circumstance for evaluating eustacy and palaeoenvironmental succession the group records a long term sea level cycle of late aptian mid turonian age its lowest part represents a transgressive systems tract developed on a pediment surface of very low local and regional relief compositionally mature glauconitic sandstone and radiolarian mudstone are characteristic facies indicative of terrigenous sediment starvation for the shallow transgressive sea which received wind driven plankton bearing currents from the shelf edge 400 km to the north a district scale nodular phosphorite horizon and associated highly condensed section capping the transgressive suite represents the culmination of deepening it is succeeded by a shelfal mudstone succession comprising the bulk of the bathurst island group and interpreted as a highstand systems tract clay mineralogy of this and the underlying radiolarian mudstone is uniform and dominated by smectite mixed layer species of poor crystallinity the clay assemblage is attributed to a pedigenic origin associated with weathering of moderate intensity on a poorly drained low relief landscape the upper part of the group comprises bioturbated glauconitic and quartzose sandstone displaying sedimentary evidence of high energy depositional conditions consistent with regression it is viewed as a prograding aggrading shelf margin systems tract which accumulated under circumstances of declining accommodation a disconformity at the top of the group cut on strata of mid turonian age completed the sedimentary cycle calculated sedimentation rates indicate a major change in detrital sediment supply broadly coincident with the passage from transgressive to highstand systems tract and unrelated to eustacy the change is attributed to mid cretaceous landscape rejuvenation it is also reflected in the late albian cenomanian sedimentary record of the epicontinental great artesian basin where enhanced sediment supply likewise overprinted and obscured the eustatic signature mid cretaceous landscape rejuvenation reflected in the sedimentary record broadly correlates with evidence of uplift in eastern and southern australia now recognised from fission track studies it also correlates with a widely recognised palaeomagnetic overprint attributed to a mid cretaceous thermal event affecting the crust of southern and eastern australia although short term third order sea level cycles are not apparent for the bathurst island group three eustatic episodes related to global patterns can be recognised late aptian transgressive onlap early albian maximum flooding and late turonian regression

analysis of sinkhole triggering mechanisms in the hinterland of naples southern italy abstract this paper deals with the analysis and verification of the most frequently occurring triggering mechanisms for sinkholes in urban areas over mine caves the study analyzes the phenomena observed in the hinterland of naples italy where intense historical mining activity has left several shallow underground man made caves and tunnels collapse generally occurs due to the presence of an underground void with or without involving the failure of the cave roof the triggering is mainly due to the increase in water content in the soil due to anthropogenic causes such as leakages from aqueducts and sewerage systems in this study the stability condition of underground man made caves was assessed through a parametric analysis based on a database of the geometry of the caves the mechanical parameters assumed in the analyses were obtained from several stratigraphic logs in situ tests and laboratory investigations the findings permitted a case study to be identified for 2d numerical analysis two triggering mechanisms scenarios were investigated in order to back analyze field observations the results reproduce the width and depth of observed phenomena and suggest that sinkhole risk mitigation in urban areas can be obtained first and foremost with enhanced knowledge of cave and tunnel networks and also with proper maintenance of buried pipelines

formation of shallow water glaucony in weakly oxygenated precambrian ocean an example from the mesoproterozoic tieling formation in north china abstract authigenic glaucony precipitation in phanerozoic oceans takes place mostly in middle shelf to upper slope environments with low depositional rate or sediment starvation precambrian glaucony however is more common in stratigraphic successions deposited from shallower water environments with high and variable depositional rates this phenomenon has long been noticed in literature but the controlling factors of shallow water glaucony precipitation in precambrian oceans have not been adequately investigated to better understand the glauconitization processes in precambrian oceans we have conducted an integrated study of the glaucony in stromatolitic carbonates of the mesoproterozoic tieling formation ca 1437 ma in north china using sedimentological mineralogical and geochemical data obtained from field observations petrography xrd sem quantitative eds and icp ms analyses macro and microscopic observations show that the tieling glaucony fills voids of varying sizes and shapes and records different maturation stages of glauconitization geochemical analyses show that the tieling glaucony has high k 2 o avg 8 but low and variable total fe 2 o 3 tfe 2 o 3 contents 1 92 13 65 wt the tfe 2 o 3 contents increase with maturation of glaucony titration results show that the tieling glaucony contains both fe 3 and fe 2 ions but has fe 2 fe 3 ratios much higher than that of the phanerozoic glaucony ree results of glaucony hosting carbonates show weak negative and positive ce anomalies with average ce ce ratio close to 1 0 suggesting carbonate precipitation near the redoxcline of fe mn oxides all these features suggest that the tieling glaucony was precipitated in seawater around the fe redoxcline where both fe 2 and fe 3 were available throughout the glaucony maturation stages high fe 2 fe 3 ratios in the depositional environments led to fe 2 occupation at octahedral sites of glaucony and negative charges on octahedrons which resulted in high k content to balance the negative charges on octahedrons and low tfe 2 o 3 limited by dioctahedral structure the formation of the tieling glaucony and other similar precambrian glauconies is likely controlled by low oxygen concentration in seawater and a shallow redoxcline that controls the availability of fe and k cations during initial precipitation and maturation of glaucony the shift of authigenic glaucony precipitation from shallow water in the precambrian to deep water in the phanerozoic may record the deepening of ocean chemocline in response to increased ocean oxygenation

alluvial dolines in the central ebro basin spain a spatial and developmental hazard analysis abstract alluvial dolines are abundant in quaternary terraces and pediments overlying neogene gypsum in the zaragoza area central ebro basin spatial analysis and experimental simulation show that sulphate content in the groundwater grain size of the detrital cover topography of the tertiary quaternary boundary annual variation of the water table and thickness of the detrital cover are the main factors controlling their development taking into account these variables a theoretical spatial hazard model has been elaborated expressed as a mathematical equation and a hazard map both experiments and field data show a high correspondance between two basic mechanisms of evacuation and subsidence dragging slow subsidence and collapse of cavities and two basic types of morphology and internal structure of dolines basin doline funnel structure and well doline vault structures respectively a genetic classification of dolines and some evolutionary patterns based on these criteria are developed historical changes observed in doline distribution as well as field surveys of urban damage and microtopographic profiles allow us to evaluate the present day activity of dolines local subsidence rates measured in urban areas range from 2 5 to 10 cm year although doline generation and reactivation in the whole area tend to be compensated by filling by human activity

glaucony from the eocene of the isle of wight southern uk implications for basin analysis and sequence stratigraphic interpretation the lower middle eocene sequence of the hampshire basin which includes an alternation of sands silts and clays interpreted as fluvial to open marine deposits is exposed at two locations on the western alum bay and eastern whitecliff bay margin of the isle of wight glaucony is encountered throughout the study units sand clay alternations of lagoonal origin and estuarine channel fill sands include less than 10 of predominantly poorly evolved allochthonous glaucony shelf silts and sands generally comprise more than 20 of evolved mostly autochthonous glaucony vertical changes in maturity of glaucony confirm the trend predicted by recent models indicating an overall upward increase in the transgressive systems tracts and decrease in the highstand systems tracts with maximum values in coincidence with the condensed sections where a remarkable peak in glaucony concentration is invariably recorded comparison of glaucony characteristics at different sites of depositional sequences shows a slight increase in maturity and abundance from the proximal to the distal areas this lateral tendency is interpreted to reflect more suitable conditions for glauconitization in open marine environments than in shallow waters despite documented intrasequential variability of glaucony characteristics glaucony assemblages from distinct depositional sequences may be generally identified on the basis of more pronounced differences in maturity consequently glaucony attributes can be used as an index for characterization of third order sedimentary cycles

compositional variability of glauconites within the upper cretaceous karai shale formation cauvery basin india implications for evaluation of stratigraphic condensation abstract a detailed mineral chemical investigation of glauconite within the condensed section deposits of the cretaceous karai shale formation cauvery basin india reflects a wide spectrum in chemical composition related to origin and evolution in different substrates stratigraphic condensation and post depositional alteration fe and mg rich glauconite comprising up to 60 of the sedimentary rocks occurs as replaced forms of fecal pellets as infillings within pores and chambers of bioclasts including those of foraminifera ostracoda bryozoa and algae and as altered forms of mica exhibiting vermiforms authigenic precipitation of k and fe poor glauconite followed by addition of fe and k into the lattice and concomitant release of al and si explains the origin of glauconite pellets and infillings the origin of glauconite vermiforms in partly degraded mica involves only the second stage of fe and k addition glauconite pellets and vermiforms exhibit sharply defined alteration zones along peripheries to form rims and in proximity to cracks or cleavages with reduced k2o and fe2o3 total and enhanced al2o3 and sio2 related to late stage meteoric water actions cores of glauconite pellets and unaltered zones of vermiforms reflect evolved characteristics with 6 k2o typical of a condensed section while other glauconite varieties occurring at the same stratigraphic level exhibit slightly evolved nature not consonant with stratigraphic condensation increasing abundance of glauconite pellets from the bottom to the top of the transgressive systems tract accompanied by slight increase in k2o within their cores reflects the effect of stratigraphic condensation on the evolution of glauconite high fe2o3 total content of glauconite in the karai shale formation may be related to upwelling although the fe may be contributed partly by the biotite substrate mossbauer spectroscopy of glauconites reveals significant total fe substitution in both tetrahedral and octahedral sites detailed mineral chemical analysis enables us to distinguish stratigraphically significant glauconite within the karai shale formation from the rest of the glauconite notwithstanding its wide compositional range

authigenic dolomite cementation in the upper cretaceous phosphate formation western desert egypt abstract the upper cretaceous phosphate formation in the western desert of egypt displays a characteristic facies association that includes marine phosphorites interbedded with black shales and glauconitic sandstones the upper part of the formation is characterized by the presence of thin phosphatic beds which are filled extensively with disordered and non stoichiometric mean mgco3 41 4 0 34 mol authigenic dolomite cement sem and the back scattered images of these coarse crystalline dolomite cements reveal that they display planar euhedral crystal boundaries polymodal crystal size distribution and variable inclusion pattern the relatively low and wide ranged 18o 0 87 to 4 15 vpdb values of the dolomite cements coupled with their depleted sr mean 187 26 ppm and high iron and manganese values mean 6851 554 ppm and 11599 229 ppm respectively invoke that they were formed from mixed hypo saline fluids within a mixing marine meteoric zone probably during a low stand period at the vicinity of the maastrichtian early tertiary unconformity meanwhile their negative 13c 1 31 to 3 56 vpdb values argue for a possible involvement of isotopically light carbon derived from degradation of organic matter during their precipitation

natural and human induced sinkholes in gypsum terrain and associated environmental problems in ne spain the central ebro basin comprises thick evaporite materials whose high solubility produces typically karstic landforms the sinkhole morphology developed in the overlying alluvium has been studied using gravimetry and ground penetrating radar gpr on stream terraces as well as analyzing the evolution of sinkhole morphologies observed in aerial photographs taken in 1928 1957 and 1985 the sinkhole morphologies give some idea of possible subsurface processes as well as an indication of the final mechanisms involve in sinkhole development on stream terraces and cover pediments the most commonly encountered dolines are bowl shaped in their morphology with both diffuse and scarped edges in contrast dolines developed in the gypsiferous silt infilled valleys have a funnel and well shaped morphology the diffuse edged bowl shaped dolines are developed through the progressive subsidence of the alluvial cover due to washing down of alluvial particles through small voids and cracks into deeper subsurface caves resulting in a decrease alluvial density future compaction of the alluvial cover will produce surface subsidences this type of dolines are associated with negative gravity anomalies in contrast the scarped edge dolines are formed by the sudden collapse of a cavity roof the cavities and cracks formed in the gypsum karst may migrate to the surface through the alluvial deposits by piping and they may subsequently collapse in this instance the cavities can be detected by both gravity and gpr anomalies where the voids are not deeper than 4 5 m from the surface these processes forming sinkholes can be enhanced by man induced changes in the groundwater hydrologic regime by both inflows due to irrigation ditch losses or pipe leakages and by outflows from pumping activities

the impact of groundwater drawdown and vacuum pressure on sinkhole development physical laboratory models abstract a considerable proportion of the damaging sinkholes worldwide correspond to human induced subsidence events related to groundwater withdrawal and the associated water table decline e g aquifer overexploitation dewatering for mining buoyancy loss in pre existing cavity roofs is generally claimed to be the main underlying physical mechanism it has been also postulated that rapid water table drawdowns may create a vacuum effect in the subsurface and contribute to enhance sinkhole activity in karstic terrains with a low effective porosity cover our laboratory physical model explores the role played by vacuum pressure induced water table drops with different magnitudes and rates on sinkhole development simulating an invariable mantled karst comprising cavernous bedrock and a low permeability cover the multiple tests performed include real time monitoring of the water level drawdown magnitude duration rate the negative air pressures in the bedrock cavity and the cover and several features of the subsidence phenomena deformation style size magnitude rate the main findings derived from the test results include 1 vacuum pressure may trigger the development of cover collapse sinkholes in areas with low permeability covers 2 different water table decline patterns magnitude duration rate may result in different subsidence styles or rheological behaviours sagging versus collapse 3 ground fissuring frequently related to extension at the margin of sagging depressions may cancel or significantly diminish the vacuum effect 4 an overall direct relationship between the water table decline rate and the subsidence rate some possible strategies are proposed to ameliorate the adverse effect of the negative air pressure on sinkhole hazard which most probably has a local impact restricted by the concurrence of rapid water drawdowns and low permeability covers

poroelastic analysis of cover collapse sinkhole formation by piezometric surface drawdown where the water table is above the soil rock contact in karst regions cover collapse sinkholes in the soil and soft sediment above the rock commonly occur as a result of drawdown of the piezometric surface in the karst aquifer transient stresses and pore pressures around soil voids at the soil rock contact can cause hydraulic fracturing of the soil near the wall of the void after the first such fracture successive sloughing of soil propagates the soil void rapidly to the surface resulting in a cover collapse sinkhole sinkhole formation by this mechanism should be strongly a function of rate and magnitude of piezometric surface drawdown permeability and tensile strength of the soil and the size depth and geometry of the initial soil void large soil voids and those with walls that are partly planar or of low curvature are most susceptible to hydraulic fracture and the resulting progression to sinkhole formation

application of limit plasticity to the stability of sinkholes abstract a solution is obtained using classical plasticity theory and the method of characteristics to evaluate the stability of soils adjacent to a cylindrical void the soil strength contains both cohesive and frictional components which allows the solution to be used to evaluate the drained stability of residual soils overlying cavitose bedrock the method yields a lower bound solution for the magnitude of a surface loading required to cause instability of the system and provides a description of the slip line defining the failure zone the results are compared in dimensionless terms for various combinations of cavity diameter and overburden thickness for a given overburden thickness small cavities are more stable than large cavities however for a given cavity diameter large overburden thicknesses are shown to be more stable than small thicknesses this is contrary to conventional slope stability where stability generally decreases with increasing height the difference is attributed to the role of a circumferential stress component in the axisymmetric solution which may be significant for small diameter cavities equations are suggested for the determinaton of the vertical stress required to generate an instability and for estimation of the size or surface extent of damage these results have significance in soil stability analyses in karst terrain and in the construction of deep foundations such as drilled shafts the improvement of methods to detect and measure voids in soil fischer and canace 1989 will make this method particularly attractive

mechanism of drying induced rebound movements in a soil slope in sai kung hong kong abstract this paper reports on a study conducted during 1992 1995 on the progressive movement of a slope in sai kung hong kong in spite of the fact that significant downslope movement was triggered during the rainy seasons the field data show that remarkable rebound in the uphill direction was mobilized during dry season when the groundwater level dropped this paper focuses on such rebound deformation which is due to the drying of the soils to investigate the mechanism of the rebound deformation a two dimensional finite element model of the slope was established and a series of hydraulic and mechanical analyses were conducted it is found that the volumetric contractive behaviour caused by the increase in suction within the unsaturated soil zones and the reduction in pore pressure in the submerged soils due to the lowering of groundwater level induced the rebound deformation moreover the water retention properties of the unsaturated soil zones can also strongly influence such deformation

a preliminary sinkhole raveling chart abstract sinkholes are a major geohazard in karst areas where soluble carbonate bedrock exists downward seepage resulting from the groundwater recharge continuously erode cover soils into cavities within the underlying bedrock resulting in raveling of cover soils identifying these raveled soils or zones is critial in preventing and mitigating the sinkhole collapse in this study a proof of concept was performed to demonstrate the concept of a sinkhole raveling chart that can quantify the severity levels of raveling the raveling chart is constructed based on cone penetration test cpt data collected through multiple sinkhole active sites in central florida a preliminary analysis e g data preparation grouping and zoning was carried out to construct the prototype sinkhole raveling chart this prototype raveling chart as a function of tip resistance qc and sleeve friction fs could delineate not only the raveled and non raveled zones but also the areas that correspond to different levels of raveling severity