Limestone Layers Research Articles

Chemical, mineralogical and textural properties of the Kope Formation mudstones: How they affect its durability

The Kope Formation is a rock unit that extends over southwest Ohio and adjacent areas of Kentucky and Indiana, USA. It is characterized by meter-scale cycles of mudstones and limestones where thick mudstone is sandwiched between thin limestone layers. Kope Formation mudstones are less durable than the mudstones in the area. They cause abundant slope failures in areas of their outcrops. This study evaluates chemical, mineralogical and textural properties of Kope mudstones to determine why it is less durable. The Two-cycle slake durability index (ID2) was measured on thirty mudstones belonging to three consecutive cycles of the Kope Formation. Chemical composition and mineralogy of Kope mudstones do not show significant relationship with the ID2. Instead, a relationship to fabric was found. Kope mudstones with two main fabric types were observed in the field; laminated mudstones and non-laminated mudstones. Detailed micro-fabric analysis on Kope mudstones was done using the scanning electron microscope. Laminated mudstones with turbostratic fabric showed higher ID2 and lower moisture content than the non-laminated mudstones with matrix fabric. The difference in the ID2 of laminated mudstones and non-laminated mudstones is statistically significant. Both mudstone types exist in many cycles of the Kope Formation. Thus, core samples should be selected from both types for preliminary tests in geotechnical practice, to obtain more accurate estimations of the geotechnical properties of the Kope mudstones. The results and data interpretations of this study can be correlated with the mudstones and shale in different areas of the world. Specifically, a great attention should be paid to the macro and micro textural properties of any rock type regardless of their classification.

Late Pleistocene gastropods from the raised reefal limestone of Jeddah, Saudi Arabia: taxonomic and palaeoenvironmental implications

A temporarily exposed 6-m succession of raised reefal limestone terrace south of Sharm Obhur (Jeddah) was investigated with regard to macrofossil gastropods and their palaeoenvironmental implications. The studied succession consists of two distinct layers. The lower layer consists of white limestone (4 m thick) of Late Pleistocene age, while the upper layer consists of shell-rich calcareous clay (2 m thick) and belongs to the last interglacial marine isotope stage 5e (MIS 5e). Its lithology was correlated with a nearby temporarily exposed 3-m succession, indicating that the deposition of the MIS 5e was not continuous, as indicated by the occurrence of a 0.4-m-thick weathered layer between the lower white limestone and upper calcareous clay. The studied 6-m succession yielded a very rich gastropod fauna with 90 species belonging to 4 subclasses, 5 orders, 16 superfamilies, 33 families and 64 genera. The clayey layer showed higher species richness (65 species) than the limestone layer (18 species), indicating a rapid change in the coral reef environment during the deposition of the interval of MIS 5e. It is assumed that, after the weathering interval, the sea level could not rebound to the same level as it was during the deposition of the white limestone, leading to deposition of calcareous clay in a shallow platform or embayment, allowing proliferation of gastropod species. Littorinimorpha and Neogastropoda species represent about 75% of the total recorded gastropod taxa, whereas Vetigastropoda and Caenogastropoda represent only 25% of the total recorded taxa. Superfamilies Cerithioidea and Stromboidea dominated the clay layer, whereas no particular species dominated the limestone layer.

Geotechnical study for cavity detection in highways using Ground Penetrating Radar, Sulaimani City, Iraqi Kurdistan Region

Construction and extension of a road over the mountainous area have undergone different problems. Several of cavities and voids were encountered during road construction especially when the road is passing through some geological formations containing limestone layers. The annual precipitation in the area under consideration approaches 750 mm. Consequently, numerous cavities of different sizes and depths developed. These cavities reduce support to the ground above when overloaded daily by a large number of heavy tracks and can cause localized collapse of the overlying rocks and deposits. Ground Penetrating Radar (GPR) has selected for detection the locations, extensions and depths of such cavities over a part of the Sulaimani – Said Sadek road passing through the limestone rocks. The GPR survey carried out over six traverses by using high resolution 200 MHZ antenna. 1642 m length covered by the survey. The result shows that GPR was very effectiveness in such high resistivity area, where the rocks are cropping out to the surface and no others geophysical methods have worked correctly. Several cavities were detected have a dimension ranging from 1 to 3 meters, and they located at depths ranging from 0.5 to 6 meters.

Late Jurassic dinosaur footprints from Chassiron–La Morelière (Oléron Island, western France)

A new dinosaur tracksite was recently discovered in the Upper Jurassic deposits from the Oleron Island (Atlantic Ocean, western France). Tracks are located along the coastline in the tidal area of La Moreliere near “Pointe de Chassiron”. They were observed in situ in an evaporitic interval from the “Purbeck beds” Unit. Sediments consist of calcite recrystallised after gypsum dissolution within limestone layers which are composed of thin laminites. The track-bearing surface shows abundant mud cracks and some ripple marks. Ichnofossils consist of medium-sized tridactyl footprints of theropods forming a narrow trackway. In order to obtain 3D reconstructions of the track-bearing surface, the trackway was scanned with a resolution of 0.5 mm using an Artec Eva 3D white-light scanner. As indicated by the track dimensions, the probable trackmaker is assigned to a medium-sized non-coelurosaur tetanuran, such as a megalosauroid or an allosauroid theropod. The palaeoenvironmental context is interpreted as a tidal flat in an evaporitic basin. In addition to the tridactyl tracks, we report sauropod- and thyreophoran-like tracks on two other surfaces from Chassiron–La Moreliere.

ANALISA POTENSI MINYAK DAN GAS BUMI DENGAN ATRIBUT SEISMIK PADA BATUAN KARBONAT LAPANGAN *ZEFARA* CEKUNGAN SUMATRA SELATAN

ABSTRACT*Zefara* Field formation Baturaja on South Sumatra Basin is a reservoir carbonate and prospective gas. Data used in this research were 3D seismik data, well logs, and geological information. According to geological report known that hidrocarbon traps in research area were limestone lithological layer as stratigraphical trap and faulted anticline as structural trap. The study restricted in effort to make a hydrocarbon accumulation and a potential carbonate reservoir area maps with seismic attribute. All of the data used in this study are 3D seismic data set, well-log data and check-shot data. The result of the analysis are compared to the result derived from log data calculation as a control analysis. Hydrocarbon prospect area generated from seismic attribute and are divided into three compartments. The seismic attribute analysis using RMS amplitude method and instantaneous frequency is very effective to determine hydrocarbon accumulation in *Zefara* field, because low amplitude from Baturaja reservoir. Low amplitude hints low AI, determined high porosity and high hydrocarbon contact (HC). Keyword: Baturaja Formation, RMS amplitude seismic attribute, instantaneous frequency seismic attribute

Cyclostratigraphic analysis of magnetic records for orbital chronology of the Lower Cretaceous Xiagou Formation in Linze, northwestern China

In this study, we report a tuned astronomical time scale for a sedimentary formation in Early Cretaceous – the lower Linze Section located in the Zhangye Basin of the central Hexi Corridor, northwestern China. Based on detailed field investigations, we identified this sediment as the Xiagou Formation, which is widely distributed in the region. A thick, prominent limestone layer crops out in the middle portion of the Linze Section, and can be correlated to a similar limestone layer in the Liupanshan Group, which has been dated via high-resolution magnetostratigraphy. This correlation places an age constraint of around 114Ma for the top of the underlying strata. A total of 1245 samples were collected from the 474-m-thick lower Linze Section, for magnetic susceptibility measurements and cyclostratigraphic analysis. Spectral and continuous wavelet analyses were applied to the low-frequency magnetic susceptibility series and the percentage frequency-dependent magnetic susceptibility series, as well as to specific subsections exhibiting visible rhythmic bedding. A hierarchy of sedimentary cycles was identified, with wavelengths of 21.5–37.0m, 7.5–9.5m, 2.1–4.4m, and 1.4–1.7m. The ratios between these lengths correspond well to the ratios between the durations of Earth's orbital long-eccentricity, short-eccentricity, obliquity, and precession cycles. We interpret these sedimentary cycles to reflect the effects of orbital forcing on sedimentary processes. Using band-pass filtering to specifically extract eccentricity cycles, we established a tuned astronomical time scale for the Xiagou Formation in the lower Linze Section, with a total duration of about 6.1Myr (114.1Ma to 120.2Ma). Based on this timescale, the sedimentation rate of the Xiagou Formation is estimated to be in the range of 62–105m/Myr, with most intervals yielding rates in the 70–80m/Myr range.

Stratigraphic revision and structure of Sierra Plomosa, Chihuahua

New geological mapping and U-Pb dating of detrital zircons and volcanic rocks permit stratigraphic revision and interpretation of pre- Late Permian deformation in the Sierra Plomosa area, located 95 km east of the city of Chihuahua and at comparable distance to the southwest of the border town Ojinaga. The Plomosas area forms the central part of a north-northwest trending uplifted block ranging from Placer de Guadalupe at the north, to the cerro Carrizalillo at the south. Along this elevated block, Precambrian crystalline basement rocks are exposed, as well as lower Paleozoic rocks belonging to the southern platform of Laurentia and upper Paleozoic to lower Mesozoic clastic and volcaniclastic rocks. The main structures in the area are north-northwest trending folds and thrust faults showing a west-southwest vergence or tectonic transport, being the age of this deformation, necessarily pre-Late Permian, given the occurrence of an erosional and angular unconformity between strongly deformed pre-Permian strata and less deformed Permian-Triassic clastic and volcaniclastic deposits which contain Archean (3,022–2,513Ma), Paleoproterozoic (2,461–1,601Ma), Mesoproterozoic (1,592–1,013Ma), Neoproterozoic (994–546Ma) and Paleozoic (533–252Ma) detrital zircon populations, with maximum depositional ages calculated between 252 and 244 Ma and isolated concordant zircons as young as 227 to 223 Ma. In the middle part of the permo-triasic succession, a Permian rhyolitic flow or ignimbrite was previously reported on the basis of a lead alpha age, however, during the present research this rock yielded an Early Jurassic age of 183.3+2.2/–2.7 Ma. On the basis of petrographic features and field relations, the rhyolite is interpreted as an ash flow tuff or ignimbrite, similar to other rhyolitic flows observed in the area. Such flows are concordant to bedding and several clasts of this rock are present in strata overlying the rhyolite. All Paleozoic rocks, including the top of the Permian and Lower Triassic, underlie clastic and volcaniclastic Jurassic rocks of shallow marine origin. In the area was also documented an erosional, locally angular unconformity which separates a Lower Jurassic unit from a Middle (?) to Upper Jurassic unit with previously reported Late Jurassic fauna in the upper part of the succession. Limestone layers in the upper part of the Jurassic succession, are recrystallized as marbles, especially in the area of the Plomosas mine, where both the metamorphism of these limestones and the presence of stratabound ore bodies of lead and zinc seem to be related to thrusting with a tectonic transport to the southwest and northwest, that placed very fractured Permian sandstones and siltstones over the Upper Jurassic rocks. The faulting is possibly associated with transpression along the so-called Plomosas lineament and transcurrent faulting, described as a left lateral shear of the basement whose regional trace lies along the eastern front of the sierra. Finally south of the Sierra Plomosa, in the northeast trending Sierra de Santo Domingo Carboniferous and Permian limestone are thrust over Jurassic sandstones and shale. This thrust fault also cuts a rhyolitic dyke of probable Oligocene age and can be considered as a very late laramide shortening contractive structure, possibly related to transpressive deformation along the Plomosas lineament and its interaction with the uplifted Cerro Carrizalillo block 15 km to the South of Plomosas.

Re-explanation relation between limestone layers and coal seam thickness of the Taiyuan Formation in Shanxi Province

Based on the strata, lithologic association and coal-bearing property – using the method of synthetic correlation – the relation between limestone layers and the thick coal seam of the Taiyuan Form...

Impact of the geological structures on the groundwater potential using geophysical techniques in West Bani Mazar area, El Minia – Western Desert, Egypt

Establishment of the new agricultural projects in west Bani Mazar area, El Minia, Egypt needs a good knowledge about groundwater. Groundwater serves as the unique source of water supplies in the study area. Vertical Electrical Sounding technique is a convenient tool for groundwater exploration. This technique was utilized to illustrate the geoelectric succession, vertical and spatial extensions of the encountered layers, depth to water bearing layers and the structures affecting these layers. Profiling technique was carried out along a grid pattern using different half current electrode spacings (150 m, 300 m and 500 m) to clarify changes in resistivity values throughout the study area at different depths. Geoelectric layers B1 and B2 of the saturated zone are suitable for groundwater extraction in the study area. The resistivity values of the geoelectric layer B1 decrease towards the West direction, they decrease from 23.0 Ωm to 16.0 Ωm; and its thicknesses increase towards the SE direction from 12.0 m to 18.0 m. Whereas, the resistivity values of the geoelectric layer B2 decrease towards the NW direction from 40.0 Ωm to 26.5 Ωm; and its thicknesses vary from 34.0 m to 40.0 m. The depths to the upper surface of the water bearing layer B1 increase towards the NW direction from 44.0 m to 89.4 m. Based on the results obtained from the Vertical Electrical Soundings, four two-dimensional resistivity imaging profiles were measured at the selected sites. These 2-D resistivity profiles aim to determine depths to the water bearing layers, their thicknesses and the shallow structure. The inverted models of these profiles matched with the geoelectric sequence at these sites. In addition, a normal fault is detected at the northwestern part of the study area.According to the results obtained from this study it is clear that the groundwater in the area under consideration is occurred in the fractured limestone layers that belong to Eocene Age. Resistivity values of the water bearing layers increase with depth as a result of decreasing fracture density; and these values decreased towards the northwestern direction due to their proximity from the fault zone. The groundwater potential of these layers depends mainly on the lithologic composition and the geological structures affecting these layers. The secondary porosity of these limestone layers depends mainly on the degree of fracturing and fissuring. The proper sites to drill new productive wells were recommended, and the obtained data from drilling new well in the southeastern part of the study area coincide with the interpreted data of the different geophysical techniques.

Audio-magnetotelluric surveys to constrain the origin of a network of narrow synclines in Eocene limestone, Western Desert, Egypt

Recent work with high resolution satellite imagery has revealed a network of narrow synclines developed during the Oligocene or Miocene over tens of thousands of square kilometers in Eocene limestone of the Thebes Group in the Western Desert of Egypt. The synclines are non-tectonic, and their scale and geometry strongly resemble sag synclines in Qatar that were produced by dissolution of subsurface evaporites and resulting sag of overlying layers. Evaporite dissolution cannot explain the Egypt synclines, because subsurface evaporites of any significance have never been reported in this part of Egypt. In this study, we use audio-magnetotelluric surveys to illuminate the subsurface under the synclines in order to constrain possible models for their formation. We suspected karst dissolution at depth, and, given a modern water table depth of over 400 m, we expected that dry fracture networks and void spaces under the synclines might result in higher electrical resistivities than surrounding coherent limestone. We also anticipated a significant change from high to low resistivity at the contact between the Thebes Group and the underlying Esna Shale at depths of 400 m or more. Instead, we found localized low resistivity zones extending from about 50-100 m below the surface to depths of more than 400 m that are strongly correlated with synclines. We suggest that these localized low resistivity zones are filled with artesian groundwater that has insufficient hydraulic head to rise to the modern topographic surface and that is localized in subsurface voids and collapse breccias produced by dissolution. Sag of overlying limestone layers is a reasonable model for syncline formation but, given the Oligocene/Miocene age of the synclines, dissolution and sag would be unrelated to young groundwater processes.

Submarine hydrothermal contribution for the extreme element accumulation during the early Cambrian, South China

Throughout the geological history of the Earth, submarine hydrothermal activity has played an important role in seawater chemistry, biological evolution and enrichment of metals in the Earth crust. However, the prospect of hydrothermal activity for extreme element accumulation during the early Cambrian, a key geological period, in South China has not been well-constrained. This study reports geochemical (e.g. REE and Sr isotope) investigations of a coarse-grained limestone layer and associated calcite veins in Zunyi and Nayong areas, Guizhou Province, to constrain the hydrothermal activity and evaluate the significance of hydrothermal contribution to extreme element accumulation during the early Cambrian, South China. Our results reveal positive Eu anomalies and higher initial 87Sr/86Sr ratios (0.7083–0.7150) for carbonate samples than those of early Cambrian seawater, indicating the presence of hydrothermal processes. Combined with constraints from the spatial relationships and coincidence with adjacent mineralization, these hydrothermal processes provide the most probable contribution for polymetallic Ni–Mo–PGE mineralization. Furthermore, there are abundant hydrothermal dolomite and barite-calcite veins in the dolostone of the Dengying Formation, indicating the occurrence of a variety of hydrothermal fluids. Overall, multi-stage hydrothermal pulses with different fluid compositions spanned the Ediacaran–Cambrian transition in South China. In particular, these hydrothermal fluids with positive Eu anomalies and enriched radiogenic Sr, originating from Proterozoic mafic/ultramafic rocks, may have flowed through the underlying Precambrian silicate clastic rocks (e.g., Xiajiang, Banxi and Lengjiaxi Groups) and may have been crucial for the marine environment, biological diversity and extreme element accumulation during the early Cambrian, South China.

Geochemical signature of paleofluids in microstructures from Main Fault in the Opalinus Clay of the Mont Terri rock laboratory, Switzerland

The present study reports on elemental and Sr isotopic analyses of calcite and associated celestite infillings of various microtectonic features collected mostly in the Main Fault of the Opalinus Clay from Mont Terri rock laboratory. Based on a detailed microstructural description of veins, slickensides, scaly clay aggregates and gouges, the geochemical signatures of the infillings were compared to those of the leachates from undeformed Opalinus Clay, and to the calcite from veins crosscutting Hauptrogenstein, Passwang and Staffelegg Formations above and below the Opalinus Clay. Vein calcite and celestite from Main Fault yield identical 87Sr/86Sr ratios that are also close to those recorded in the Opalinus Clay matrix inside the Main Fault, but different from those of the diffuse Opalinus Clay calcite outside the fault. These varied 87Sr/86Sr ratios of the diffuse calcite evidence a lack of interaction among the associated connate waters and the flowing fluids characterized by a homogeneous Sr signature. The 87Sr/86Sr homogeneity at 0.70774 ± 0.00001 (2σ) for the infillings of most microstructures in the Main Fault, as well as of veins from nearby limestone layer and sediments around the Opalinus Clay, claims for an “infinite” homogeneous marine supply, whereas the gouge infillings apparently interacted with a fluid chemically more complex. According to the known regional paleogeographic evolution, two seawater supplies were inferred and documented in the Delemont Basin: either during the Priabonian (38–34 Ma ago) from western Bresse graben, and/or during the Rupelian (34–28 Ma ago) from northern Rhine Graben. The Rupelian seawater that yields a mean 87Sr/86Sr signature significantly higher than those of the microstructural infillings seems not to be the appropriate source. Alternatively, Priabonian seawater yields a mean 87Sr/86Sr ratio precisely matching that of the leachates from diffuse calcite of the Opalinus Clay inside the Main Fault, as well as that of its microstructures and the same features of the sediments above and below. To envision a Priabonian seawater supply, there is a need for its storage without a significant evolution in its Sr isotopic composition until the final deformation of the area. The paleo-hydrogeological context calls for a possible infiltration of the seawater into a limestone karst located above the Opalinus Clay that could have acted as the storage reservoir. The karstic nature of this reservoir also explains why the 87Sr/86Sr of the fluids was not modified significantly until expulsion. An alternative storage could have been provided by the regional faulting system that developed during the contemporary regional rifting of the Rhine Graben. The fluid expulsion started along these extensional faults during the further Upper Eocene–Lower Oligocene rifting phase. Later, the thin-skinned deformation of the Jura Belt affected the Mont Terri region in the form of the Main Fault, probably between approximately 9 and 4 Ma on the basis of preliminary K–Ar ages of nanometer-sized authigenic illite crystals recovered from gouge samples.

Mineralogical characteristics of upper Jurassic Mikulov Marls, the Czech Republic, in relation to their thermal maturity

The Upper Jurassic Marls of Mikulov present a formation that is considered to be the most promising strata to produce hydrocarbons in the Vienna basin. The marls are composed of dark pelagic marlstones that frequently contain layers of limestone with thickness reaching several hundreds of meters. Twenty-seven core samples from selected wells located in the south-eastern portion of the Czech Republic representing depths ranging from 2300 to 4500m were analyzed by x-ray diffraction to assess bulk mineralogy and the progress of smectite illitization.Bulk mineralogy of the Mikulov Marls comprises carbonates (mean value=54.4 mass%), clay minerals (26.6 mass%), quartz (15.0 mass%), and feldspar (1.6 mean%). In the decreasing order, the clay mineral fraction is composed of illite/mica, kaolinite, illite-smectite, and chlorite. The amount of smectite in illite-smectite decreases with depth from 70% to 28%. There is a change from random to ordered interstratification at the depth of 3300m. The transition from short-range ordering (R1) to long-range ordering (R3) occurs at depths greater than 4,500m.There was a good correspondence between thermal maturity parameters: the percentage of smectite in illite-smectite structures and vitrinite reflectance as a parameter of organic matter. The increase of the metamorphic grade was compared in respect to the geothermal gradient with adjacent basins.

Pillar Burst Assessment Based on Large-scale Numerical Modeling

Stress concentration is a direct result of stress redistribution around an excavation, that may lead to rock bursting under specific geomechanical conditions. This paper presents a case-study of a rockburst that took place in the shaft station area of the Provence coal mine in Southern France. The mined coal seam has a 2.5 m thickness and a 10° dip angle. The rockburst occurred in 1993 at the shaft station level, where it is surrounded by several longwall panels that were excavated between 1984 and 1994. The area of the shaft station is at 1000 m depth. A very thin layer of stiff limestone occupied the middle of the exploited coal seam. A large-scale finite difference numerical model of the mine has been constructed by using FLAC3D. The model simulates the area of the shaft with its irregular pillars and the longwall panels excavated between 1984 and 1993. The excavations were performed in two steps. Firstly, the galleries of the shaft station area were excavated in order to determine their effect on the failed pillar. Then, the longwall panels were excavated year by year to detect the stress and strain energy increments induced on the pillars. The origin of the rockburst was analysed based on different rockburst criteria. The results show that the vertical stress increased in the shaft station pillars due to excavation of longwall panels. In addition, we found that the small pillars have higher burst tendency than the large ones. Finally, the Burst Potential Index (BPI) was found to be able to estimate the pillar burst tendency based on the energy storage rate (ESR), however, this criterion (BPI) is based on calculating the stress and the energy changes in the vertical direction only.

Source rock formation evaluation using TOC & Ro log model based on well-log data procesing: study case of Ngimbang formation, North East Java basin

Ngimbang Formation is known as one major source of hydrocarbon supply in the North Eastern Java Basin. Aged Mid-Eocene, Ngimbang is dominated by sedimentary clastic rocks mostly shale, shaly sandstone, and thick layers of limestone (CD Limestone), with thin layers of coal. Although, laboratory analyses show the Ngimbang Formation to be a relatively rich source-rocks, such data are typically too limited to regionally quantify the distribution of organic matter. To adequately sample the formation both horizontally and vertically on a basin–wide scale, large number of costly and time consuming laboratory analyses would be required. Such analyses are prone to errors from a number of sources, and core data are frequently not available at key locations. In this paper, the authors established four TOC (Total Organic Carbon Content) logging calculation models; Passey, Schmoker-Hester, Meyer-Nederloff, and Decker/Density Model by considering the geology of Ngimbang. Well data along with its available core data was used to determine the most suitable model to be applied in the well AFA-1, as well as to compare the accuracy of these TOC model values. The result shows good correlation using Decker (TOC) Model and Mallick-Raju (Ro- Vitrinite Reflectance) Model. Two source rocks potential zones were detected by these log models.

Geophysical Assessment of the Upper Dja Series Using Electrical Resistivity Data

The upper Dja series consists of carbonates and shales deposits that date 580 ± 150 Ma. Petrography and mineral chemistry studies helped to differentiate this series into many sequences including massive limestone layers with calcite (CaO3) contents of about 30 to 42%. In order to determine the subsurface distribution of these sequences, a geophysical prospection campaign was carried out in which a total of 24 vertical resistivity soundings were recorded over a surface area of 9 km2. The processing and interpretation of data using the IX1D and OpendTect modeling tools permitted the distinction of two massive limestone layers in the upper Dja series. The first layer of about 10 to 35 m thick and outcrop in few places is characterized by resistivity ranging between 1110 and 2377 Ωm, while the second layer located beyond 50 m deep is separated by a very conductive clay stone layer with a capped thickness of 15 to 35 m. 3D modeling of the top and base of these formations indicates that, the whole Upper Dja series of about 190 m thick presents folded structure. These results can constitute a useful base of information in regards to a large scale economic study of the Upper Dja limestone series.

Ground-Based Hyperspectral Image Analysis of the Lower Mississippian (Osagean) Reeds Spring Formation Rocks in Southwestern Missouri

Ground-based hyperspectral imaging is fairly new for studying near-vertical rock exposures where airborne or satellite-based imaging fail to provide useful information. In this study, ground-based hyperspectral image analysis was performed on a roadcut, where diagenetic tripolite facies is observed in southwestern Missouri. Laboratory-based reflectance spectroscopy and hyperspectral image analyses were also performed on collected samples. Image classification was performed using Spectral Feature Fitting (SFF) and Mixture-tuned Match Filtering (MTMF) with laboratory- and image-derived end-member spectra. SFF provided thorough yet detailed classification, whereas MTMF provided information on the relative abundances of the lithologies. Ground-based hyperspectral imaging demonstrated its potential to aid geological studies providing valuable information on mineralogical and lithological variations rapidly and with two-dimensional continuity in inaccessible rock faces of near-vertical outcrops. The results showed decreasing tripolite abundance going downward in the investigated vertical succession. Also, a leaching pattern has been observed such that persistent and continuous limestone layers become lenses and patches towards the upper portion of the outcrop. These observations show that the effect of tripolitization decreases when going deeper in the succession, suggesting that the fluid responsible for the weathering of siliceous precursors may have been flowing from top to bottom and thus have had a meteoric origin.

Contribution A La Caracterisation Diagraphique Des Depots Carbonates Du Cretace Du Bassin Sedimentaire De Cote D’ivoire

To know the petrophysical characteristics associated with sedimentary facies gammay ray logs providing information on the natural radioactivity of sedimentary rocks and the sonic logs which document on facies and petrophysical variations rocks were studied. This study focused on three (3) wells (BH-X, DH-X and MR-X) bored in the offshore basin of Abidjan margin (Côte d’Ivoire) for which the lithogy is constituted of clay alternating with sand an sandstone at the base surmounted by limestone and marls which are covered by clay series. It reveals that two deposits phases occurred during the carbonate sedimentation. Through the gamma ray logs, it appears that the clay phases have low radioactivity, which often progress to average values. This radioactivity recorded in clays would be linked to the low organic matter content and leaching reworked elements. In marl phases radioactivity is medium to high indicating a high content of uranium, thorium and potassium deriving from clay minerals. The gamma ray log varies significantly in limestone phases reflecting the heterogeneity of deposits. Strong radioactivity values in some limestone layers are related to their homogeneity and the present of organic matter. Fluctuations result from long-term changes in submarine hydrothermal flow and may indicate significant variations in facies (crystalline limestone, marl and clay). There are more or less dolomitised layers alternating with more homogeneous chemical limestone benches, biogenic limestone debris of organisms and past clay. The sonic log has two phases in the marl and limestone interval. In the marl phase, the acoustic wave velocity is almost constant, but in the limestone phase velocities fluctuate. Indeed, marl interval contains heterogeneous deposits. Generally the velocity is still low in impermeable and little porous clay. In marls, relatively high propagation velocity implies that they are less penetrable as clays because of the presence of fluid. The sonic log fluctuations in the limestone stage reflect the heterogeneity of deposits. Calcareous layers generally have a shorter time of wave propagation, suggesting that they are indurated, recrystallized and homogeneous. By against certain layers are poorly penetrable and show the presence of fluid. The limestone is fractured, so more porous than clay and marl. The porosity may be related to diagenesis after being dessoluted.

Recognition and strength characterization of platy limestone layers in the Classical Karst quarries (NE Italy)

This paper shows the results of research investigations carried out along the karst plateau located in the Trieste and Gorizia counties (NE Italy), with special emphasis on limestone quarries. Field surveys allowed the recognition, identification and mapping of quarries characterized by the presence of Platy Limestone (PL). The latter is characterized by a single discontinuity set with spacing not exceeding 10 cm. For this reason, the geometry of PL rock masses provided, for a long time, slabs easy to be excavated. PL was widely used by locals for roofs of buildings situated mainly in the rural surroundings of Trieste. The research envisaged a multidisciplinary approach, which also included the definition of the main geometrical features of PL quarries, the state of activity and the geotechnical properties of PL rock mass. Particular attention was devoted to the definition of PL intact rock strength, which is major rock property. Intact rock strength determines the strength of the rock slab and therefore its geomechanical quality. The outputs of this paper can motivate local authority to protect PL and promote its use for the restoration of historical buildings

Mineral composition and geochemical characteristics of the Li-Ga-rich coals in the Buertaohai-Tianjiashipan mining district, Jungar Coalfield, Inner Mongolia

The coals from the Jungar Coalfield, Inner Mongolia, China, have been found to be enriched in Ga and Li. These are valuable metals that are potentially recoverable from coals and/or coal combustion residues. Based on fifteen roof/floor/parting samples collected from one borehole and one hundred and forty one bulk coal samples collected from three boreholes in the Buertaohai-Tianjiashipan coal mining district, Jungar Coalfield, this paper reports new data on the mineral compositions and geochemical characteristics of the Jungar Li-Ga-rich coals, and provides new evidence for the origin and mode of occurrence of Al, Ga and Li in these coals.The main mineral phases occurring in the coals are kaolinite, boehmite, calcite, with small proportions of quartz, pyrite, ankerite, siderite, and trace amounts of microcline and rectorite. An unusual mineral phase, svanbergite (SrAl3(PO4)(SO4)(OH)6) also occurs as a main mineral constituent in the studied coals. The mineral phases in the roof/floor/parting samples are dominantly kaolinite, with a small proportion of quartz. Kaolinite is of both terrigenous and authigenic origin, which were possibly derived from terrigenous Yinshan Oldland sediment-source region and/or from recrystallization during the coal formation process. Boehmite and svanbergite are primarily of authigenic origin, and were dominantly derived from the weathered bauxite sediment-source region. Calcite may have formed by dissolution of limestone layers close to the margin of coal basin and subsequent deposition of the Ca or Mg-rich carbonates in the cells/fractures of the coal seams. Sulfide minerals in fractures may have been precipitated from epithermal fluids. Rectorite was probably formed by the reaction of kaolinite with epigenetic low-temperature hydrothermal fluids during diagenesis.Compared to common Chinese and worldwide coals, the studied Jungar coals are much more enriched in Al (4.4–6.1%), Li (70–79mg/kg), and Ga (14–19mg/kg). Titanium, P, Sr, Zr, Nb, Th, Ta, Hf, and rare earth elements (REEs) are also enriched in the studied coals to some extent. Aluminum in the coals mainly occurs in the form of kaolinite and boehmite, whereas, lithium may be associated with aluminosilicate minerals (kaolinite and illite if present) as well as svanbergite. Gallium principally occurs in kaolinite, and to a lesser extent, svanbergite. Strontium, P, and LREEs (La, Ce, and Rr, Nd and Sm) mainly present in svanbergite. The source of Li and Ga in Jungar coals is most likely from the Yinshan Oldland region, but there is also a possibility of migration from bauxite of the Benxi formation.