Limestone Range Research Articles

Checklist of land snail species of Gua Rumbang, Sarawak, Malaysian Borneo (Mollusca, Gastropoda), with a description of a new species, Diplommatinarumbangensis sp. nov.

The current study presents an annotated checklist of the land snail species in the vicinity of the limestone hill of Gua (= cave) Rumbang, an outcrop located at the district of Padawan, Sarawak, Malaysian Borneo. The sampling was conducted at the surrounding areas and near the cave's entrance. A total of 62 species, involving 19 families and 38 genera, were recorded. Comparison with previous surveys made in the Bau limestone hills revealed similarities with respect to the species-rich families Diplommatinidae and Cyclophoridae, and the genera Kaliella and Diplommatina, highlighting the regional consistency of the land snail diversity of the Bau-Padawan-Serian cluster. Possibly because of its smaller size, Gua Rumbang is home to two endemic species, while there are eight endemic species in the Bau limestone karsts. This suggests a potential for a significant species diversity within the areas of the limestone ranges that remain to be explored. Nonetheless, the occurrence of endemic species in Gua Rumbang highlights the need to conserve certain areas within the Padawan limestone range since hitherto no protected areas have been proposed in this region. In this checklist, a new species for science is also described, namely, Diplommatinarumbangensissp. nov.

Dolomitization Controlled by Paleogeomorphology in the Epicontinental Sea Environment: A Case Study of the 5th Sub-Member in 5 Member of the Ordovician Majiagou Formation in Daniudi Gas Field, Ordos Basin

The 5th sub-member in 5 Member Ordovician Majiagou Formation in Daniudi Gas Field, Ordos Basin, is deposited in an environment consisting of an ancient epicontinental sea, where very fine crystalline dolostone reservoir has developed. In this study, based on the petrological and geochemical characteristics, the genesis of the dolomite developed in M55 were studied by analyzing the properties and sources of the dolomitization fluids, and the influence of the paleogeomorphology differences on the distribution of dolostone was also discussed in order to clarify the distribution of the dolostone developed in the lime flat of the epicontinental sea. The dolostone of the M55 had a crystal structure, mainly including microcrystalline and very fine crystalline. The content of MgO and CaO in dolomite was negatively correlated, indicating that it was the result of replacement. The dolomite was dark red under cathode luminescence, and the distribution mode of rare earth elements showed the negative anomaly of Ce and Eu, indicating that the dolomitization fluid was sea-sourced fluid. The δ13C, δ18O, and 87Sr/86Sr isotope range of limestone was similar to that of Ordovician seawater in the study area, whereas the δ13C, δ18O, and 87Sr/86Sr of dolostone were obviously more positive than that of limestone. The substitute index of the salinity (Z) of the dolomitization fluid was higher than 122, which is higher than limestone (Z = 120.5), indicating that the dolomitization fluid was slightly evaporated seawater. The wormholes observed on the core and the gypsum in the penecontemporaneous period observed in the thin sections indicated that the dolostone was formed in a period when the sea level was relatively low, and it was the result of seepage–reflux dolomitization. By analyzing the correlation between the thickness of dolostone and the paleogeomorphology of the M55 of the sedimentary period, it was found that the thickness of dolostone at relatively high altitude was significantly larger than that of other areas. The development of dolostone was controlled by sea level, and the local paleogeomorphology controls the distribution of dolostone during the period of low sea level. There were many more limestone–dolostone cycles and larger cumulative thicknesses of dolostone at relatively higher topography. This study provides a theoretical basis for the prediction of the distribution of dolostone reservoirs in the carbonate tidal flat environment dominated by lime flats under the background of the ancient epicontinental sea.

New perspectives on lateritic weathering process over karst area – Geochemistry and Si-Li isotopic evidence

Silicon and lithium isotopes are increasingly used to trace current and past weathering processes. Herein, four soil profiles (SL1, SL2, XNC, and DP) in the karst critical zone in southwest China were studied. The bedrock of the SL1, SL2, and XNC profiles are limestone, while the bedrock of the DP profile is shale. By analyzing their major elements, trace elements, and mineral compositions as well as using Si and Li isotope methods, we were able to identify the material source of the laterite in southwest China and study its element behavior and isotope fractionation characteristics during the weathering process. The results show that the δ30Si of the profiles overlying limestone (SL1, SL2, and XNC) range from −0.5‰ to 0.7‰, and those of the δ7Li range from 0.28‰ to 3.54‰, while the profile overlying shale (DP) has a large range of δ30Si variation (from −1.2‰ to 1.1‰). The results reveal a clear inheritance from the underlying bedrock, indicating that the profiles reflect in-situ weathering. Although no obvious relationship exists among the chemical index of alteration (CIA), the δ30Si, and the δ7Li, a significant correlation between δ30Si and δ7Li indicates that the isotope fractionation of the studied profiles is mainly affected by the dissolution and formation of minerals during the weathering process, and the biological effect is relatively small. Further, a diagram of Li/Al versus δ7Li shows a decrease in both Li/Al and δ7Li during weathering.

Chemostratigraphy of the lower Cretaceous Mural Limestone, Rancho Bufalo section, Sonora, Mexico: Implications for OAE 1b

A multidisciplinary approach of the Aptian-Albian Mural Limestone including petrography, geochemistry and stable isotope data is undertaken for the 660-m thick Rancho Bufalo section of northeastern Sonora to characterize source of rare earth elements and to infer paleo-redox conditions. The lithofacies of limestones range from mudstone to boundstone. The unaltered signatures of the δ13C values are confirmed by using Mn and Sr concentrations and their ratios along with the absence of correlation between δ13C and δ18O values. The limestones have large variations in ΣREE and Al2O3 contents (8.0 − 95.8 ppm; 0.45% − 7.10 ppm; respectively). Most limestones show non-seawater-like REE + Y patterns with positive Eu anomalies and negative Ce anomalies. The limestones have positive Ba anomalies in six intervals and most of them were resulted due to weathering and depositional processes and not due to sea level variations. The redox proxies of U, V/Cr and V/(V + Ni) indicate that the bottom water conditions fluctuated from oxic to anoxic. The high-resolution carbon isotope curve reveals four OAE 1 b sub-events: Jacob, Kilian, Paquier, and Leenhardt. The carbon isotope curve of the Rancho Bufalo section is comparable to that of the Cerro Pimas and Peregrina Canyon sections of Mexico.

A strontium isotopic, petrographic, and Ostracoda biostratigraphic study of Middle-Late Miocene sequences: implications of record in the Silifke–Erdemli/Mersin, southern Turkey

In this paper, we present new data on Ostracoda micropaleontology, strontium isotopic ages, and petrology of the Miocene sequences in the Silifke–Erdemli area (Mersin/S. Turkey). Ostracods were investigated in the Middle and Late Miocene units, which are composed of clayey limestone and marl levels, reef limestones, and clay. Fifty-six ostracod species were identified, and a total of two initial levels were defined, one beginning in the Langhian stage, and the second at the end of the Serravallian and beginning of the Tortonian stage. The initial level of the Langhian stage is represented by the Carinocythereis, and the end of the Serravallian–beginning of the Tortonian stage is characterized by the initial level of Cyprideis. These levels have also been compared with other regions in the same stratigraphic levels in Turkey (Adana, Antakya, Mut, Denizli, and Antalya regions) and in areas around Turkey (Egypt, Italy, Greece, Croatia, and other Tethys–Paratethys regions). In addition, the levels identified in this study were also correlated to the planktonic foraminiferal zones identified for this region. The ostracod species identified are Carinocythereis at the initial level and subsequently, Cytherella postdenticulata Oertli, Grinioneis haidingeri minor (Ruggieri), Pokornyella deformis minor (Moyes), Carinocythereis antiquata (Baird), and Paracypris polita Sars; also, the other ostracod species are an initial level of Cyprideis followed by Cyprideis seminulum (Reuss), C. torosa (Jones), Cytheridea acuminata acuminata Bosquet, Miocyprideis sarmatica (Zalanyi), Neomonoceratina interiecta Bonaduce, Ruggieri, Russo and Bismuth, Schneidrella dromas (Schneider), and Krithe monosteracensis (Sequenza). Detailed petrographic analyses were carried out on the studied units. This analysis revealed that the reef limestones are composed of sandy intraclast-biomicrites, intra-packed biosparite, intra-packed biomicrite, microintra-packed micrite, and bioclastic-intramicrites; clayey limestones were rare clayey biomicrites and clayey intraclast-biomicrites. The main purpose of the study was to evaluate micropaleontological samples from the Miocene sequence based on ostracods and strontium dating to determine the precise age ranges. The 87Sr/86Sr ratios obtained from three samples of the limestones range between 0.708849 and 0.708902 and between 0.708868 and 0.708902, respectively. The Miocene sequences have been calibrated to range in age from 9.7 to 11.4 Ma via the strontium isotope ratio.

Ignition and explosion parameters of Colombian coals

The explosivity of coal in Colombia is usually determined by chemical analysis based on the volatile ratio. To improve the assessment of the explosivity of those coals that have led to numerous explosions in Colombian mines, 22 coals from the department of Antioquia were analyzed. Flammability characteristic parameters were determined, such as minimum temperatures and energy for ignition and the lower explosive limit. Also explosion data, ie. Pmax and Kmax values were obtained. In addition, the susceptibility to spontaneous combustion was studied by thermogravimetry and differential scanning calorimetry, together with chemical attack with hydrogen peroxide and also measuring the temperature of ignition of flammable volatiles. Finally the effect of particle size and the percentage range of limestone needed for inerting coal under two different granulometries were determined.

Impact of Hydrated Lime on Cracking Performance of Asphalt Mixtures with Oxidation and Cyclic Pore Pressure

This research was conducted to evaluate the impact of hydrated lime (HL) on the cracking performance of asphalt mixtures for a broad range of aggregate types, including granites and limestones. A recently developed conditioning procedure, long-term oven aging (LTOA) plus cyclic pore pressure conditioning (CPPC), was employed to simulate the effects of long-term field aging on asphalt mixtures. The energy ratio (ER) approach, which took into account mixture properties that were known to be closely related to cracking and was calibrated with cores taken from field-aged pavements throughout Florida, was used to evaluate the cracking performance of untreated and lime-treated mixtures. The results show that the introduction of HL appeared to mitigate the detrimental effects of oxidative aging and moisture (LTOA plus CPPC) on the damage and fracture-related properties of granite and limestone mixtures. This effect resulted in better cracking performance of these mixtures. Further analysis based on comparison of initial construction costs of conventional pavement structures revealed that the use of HL could result in lower costs to achieve pavements with the same level of good performance. Furthermore, this research showed that the equivalent ER criterion proposed and implemented in the cost analysis could effectively assess the impact of HL modification.

Typification D'Androsace pubescens DC. (Primulaceae)

Abstract Jacquemoud, F. D. Jordan (2015). Typification of Androsace pubescens DC. (Primulaceae). Candollea 70: 237–239. In French, English and French abstracts. DOI: http://dx.doi.org/10.15553/c2015v702a9 The name Androsace pubescens DC. (Primulaceae) is typified by designating a neotype in the “Prodromus” herbarium (G-DC). In order to follow as close as possible the original description and the protologue, the selected specimen comes from a limestone range near to the locus classicus and holds white flowers and an indumentum with simple hairs.

Petrography, lithofacies and depositional environment of carbonate-clastic strata in part of the north-western Douala Basin, Cameroon

The lithofacies, petrofacies and sedimentary environments of carbonate-siliciclastic strata of the Tertiary Nkapa Formation have been examined. This paper provides new data on the carbonates whose location and composite thicknesses of outcrop lithologies represent an important segment of the broader West-Central African Platform. The main carbonate outcropping belt is along the Bongoue River and its tributaries. Field and petrographic investigations reveal that carbonates in the study area consist of a number of lithologically distinct facies. These facies are non-skeletal to skeletal in composition including olithic, perlithic, bioclastic and marly limestones which occur in alternation with sandstones and shales. The studied limestones were mostly grain-supported exhibiting textures that range from grainstone, packstone to wackestone. Non-skeletal bioclasts are mainly made up of superficial and composite ooids, and peloids showing grainstone and packstone texture, respectively. The ooids have grain diameter varying from 0.1 to 1.5 mm. The pellets are of faecal origin. The bioclastic limestones are characterised with a packstone to wackestone texture (fifty–fifty), typically associated with nodules and abundant skeletal fragments suggesting deposition in shallow marine barrier reef settings. This interpretation is further supported by the presence of worm tubes in the limestones. Micritic and sparry calcite cement and opaque grains (FeS2) make up the matrix and infill within skeletal fragments. The limestones range from abundant biosparites to minor biomicrites.The marly limestones are characterised with a wacke-to-packstone texture, mainly made up of abundant lithoclasts and minor bioclasts indicating their deposition in areas closer to the continent with large influx of terrigenous clastic material. Sandstones are mostly sublitharenites (>75 %) with minor litharenites (≤25 %). The different lithofacies (carbonates, sandstones, shales) investigated demonstrate that these sediments were deposited in a wide range of environments that varies from continental shelve zones, shallow marine (reef related) to relatively deep marine environments.

Cretaceous-Tertiary (K-T) boundary evaporites in the Malatya Basin, eastern Turkey

The Malatya basin is situated on the Anatolid-Torid plate of the Neo-Tethys Sea. Evaporites were deposited in the northwestern part of the Malatya basin, which is referred to as the Hekimhan sub-basin. Although the Gunduzbey sub-basin in the southeastern Malatya basin has coeval deposits, it contains no evaporate deposits. The evaporite is most likely the result of the last transgressive–regressive cycle of the Late Cretaceous Sea. The pre-evaporitic unit is represented by the carbonate platform deposit of the Loftusia banks, which partly underwent dolomitization and overlies the deep marine sediments. Celestite-bearing algal limestone was deposited directly below the gypsum-dominated evaporate unit in association with the organic-rich mudstone. Evaporite sedimentation took place in various types of environments, such as marginal shallow subaqueous with the association of sabkha–coastal lagoon and deeper subaqueous. It is assumed that the tectonic evolution of the basin margin, which occurred during the latest stage of the Cretaceous regression, was responsible for the environmental restriction leading to evaporate sedimentation under arid/semiarid climatic conditions. The 87Sr/86Sr ratios obtained from 38 samples of the gypsum and celestite-bearing limestones (11 samples) range between 0.707817 and 0.707980 and between 0.707783 and 0.707864, respectively. The δ34S values range from +19.5 to +22.4 ‰, and the δ18O values range from +9.6 to +12.7 ‰. These isotopic signatures correspond to that of Late Cretaceous/Early Paleocene (Cretaceous-Tertiary boundary) marine water. However, celestite exhibit(s) relatively higher δ34S and 87Sr/86Sr values than expected marine values, which could be a result of contribution of diagenetic fluid into the celestite-precipitated environment.

Fundamental Study of Indirect vs Direct Sulfation under Fluidized Bed Conditions

Direct dry sorbent injection is a relatively simple and low-cost process for the capture of SO2 emissions, particularly for in-bed capture during fluidized bed combustion. SO2 capture by limestone may be accomplished by either direct or indirect sulfation, depending on gas-phase environment and operating conditions. In this paper, a combination of thermogravimetric analysis (TGA) and a bench-scale bubbling fluidized bed reactor were used to study sulfation, calcination and carbonation behavior of limestone at different CO2 concentrations and various temperatures to identify the relative contributions of indirect and direct sulfation reactions under air- or oxy-fired fluidized bed combustion conditions. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy analyses were also used to help identify product layer microstructure and composition. A significant temperature dependence on the sulfation of limestone was seen under oxy-fired conditions (when direct sulfation dominates); however, limited temperature dependence was seen for air-fired conditions (where indirect sulfation dominates). A distinct CaSO4 product layer is seen in SEM images for the air-firing condition that can significantly inhibit gas transport into internal pores. No such distinct product layer was seen for oxy-firing conditions. For the size range of limestone used in this study (600 to 1000 mu m), indirect sulfation (dominant under air-fired conditions) appeared to be strongly limited by diffusion, whereas direct sulfation (dominant under oxy-fired conditions) was mainly under kinetic control or a mixture of kinetic and diffusion control.

Geology, mineralogy, geochemistry, and depositional environment of a Late Miocene/Pliocene fluviolacustrine succession, Cappadocian Volcanic Province, central Anatolia, Turkey

This paper investigates the mineralogy, geochemistry, and depositional environment of Late Miocene/Pliocene fluviolacustrine deposits, including multiple ignimbrite levels and andesitic and basaltic lavas, within the Cappadocian Volcanic Province (CVP) of central Anatolia, Turkey. Palaeosols and calcretes formed within these terrestrial sedimentary rocks under near-surface or surface conditions. The palaeosols are composed predominantly of smectite ± illite with feldspar, quartz, calcite, opal-CT, and amphibole, and the calcretes mainly of calcite with minor feldspar, quartz, and accessory smectite ± palygorskite. The palygorskite occurs on and between the calcite crystals in the calcretes and at the edges of smectite flakes within the palaeosols, indicating an in situ formation from evaporated alkaline water rich in Si and Mg and poor in Al under arid or seasonally arid climatic conditions. In the palaeosols and calcretes, negative Ba, Nb, Ce, Sr, and Ti anomalies and an enrichment of light rare earth elements relative to medium rare earth elements and heavy rare earth elements, with a distinct negative Eu anomaly, likely reflect the alteration of feldspars and amphiboles in the ignimbrite. The alteration of the ignimbrites caused the depletion of SiO2, Al2O3+Fe2O3, TiO2, and K2O through the precipitation of smectite ± illite in the palaeosols and CaO in the form of calcite in the calcretes. The delta18O values of the calcretes and limestones range from –8.71‰ to –10.71‰, which are mainly related to the involvement of high-elevation meteoric water, whereas the delta13C values for the same rocks vary between –1.97‰ and 5.71‰. The positive delta13C values for the limestones reflect calcite precipitation in isotopic equilibrium with meteoric water in a lake. The slightly negative delta13C values of the lacustrine limestone carbonates may indicate precipitation from a relatively thick water column and an inflow of surface or groundwater through the ignimbrites with high Ba/Sr values. Conversely, the calcrete delta13C values (3.0‰ to 4.97‰) may suggest a pedogenic origin with low plant respiration rates and a predominance of C4 plants. Based on stable oxygen isotope values from the lake sediments and calcretes, this study suggests that the global warming trend that followed the Late Miocene continued into the Pliocene within the CVP.

Foraminifers and conodonts from the late Viséan to early Bashkirian succession in the Saharan Tindouf Basin (southern Morocco): biostratigraphic refinements and implications for correlations in the western Palaeotethys

The Carboniferous succession in the Tindouf Basin of southern Morocco, North Africa, displays Mississippian to Early Pennsylvanian marine beds, followed by Pennsylvanian continental deposits. The marine beds comprise a shallow water cyclic platform sequence, dominated by shales and fine-grained sandstones with thin but laterally persistent limestone/dolostone beds. Foraminiferal assemblages have been studied in the limestone beds in several sections from the Djebel Ouarkziz range in the northern limb of the Tindouf Syncline; they indicate that the age of the limestones range from late Asbian (late Viséan) to Krasnopolyanian (early Bashkirian). The foraminiferal assemblages are abundant and diverse, and much richer in diversity than those suggested by previous studies in the region, as well as for other areas of the western Palaeotethys. The richest assemblages are recorded in the Serpukhovian but, unusually, they contain several taxa which appear much earlier in Western European basins (in the latest Viséan). In contrast, conodont assemblages are scarce due to the shallow-water facies, although some important taxa are recorded in the youngest limestones. Copyright © 2013 John Wiley & Sons, Ltd.

Characterizations of the CCUS Attributes of a High-priority CO2 Storage Site in Wyoming, USA

Optimizing uncertainty reduction in evaluations of geological CO2 storage site scenarios requires a robust database that allows an accurate reconstruction of the targeted storage rock/fluid volume, especially with respect to spatial heterogeneity. Previous numerical simulations of the Rock Springs Uplift site (southwest Wyoming, USA) relied on a generalized regional database to populate a homogenous rock/fluid volume based on average reservoir properties. The results from this approach yielded general insights into injection/storage characteristics but lacked specificity, resulting in performance assessments plagued by substantial uncertainty. To move from idealistic, highly generalized assessments to realistic, low-risk assessments of the Rock Springs Uplift, it was necessary to acquire high-resolution data specific to the storage site of interest (carbonate and sandstone reservoirs, and confining layers in an 8km × 8km area). The foundation of the new database is a 4,000-meter-deep stratigraphic test well, an 8km × 8km 3-D seismic survey, 290 meters of high-quality core, a specialized log suite, fluid samples, and a diverse set of analytical laboratory measurements. These data made it possible to correlate seismic attributes with observations from log suites, a VSP survey, core, fluid samples, and laboratory analyses, including continuous permeability scans. From seismic data, 3-D spatial distribution volumes of reservoir and confining layer properties were constructed that represent geological heterogeneity at the targeted CO2 storage site. Consequently, the latest numerical simulations and performance assessments are characterized by substantially lower geological uncertainties.The new CO2 plume migration simulations for a set of defined CO2 injection rates and volumes occupy larger rock/fluid volumes and display pronounced marginal irregularities when compared to early simulations derived from homogenous reservoir parameter volumes. The spatial distributions of the injected CO2 plumes in previous simulations are conical with few marginal irregularities, whereas in the new simulations, the CO2 plumes occupy a larger up-dip volume and display pronounced marginal irregularities. These irregularities denote zones of higher porosity and permeability, such as collapsed breccias associated with karst zones and/or dolomitized grainstone zones in the Madison Limestone.Using the new numerical simulations which include heterogeneous rock/fluid parameter distributions, it is apparent that in all injection/storage scenarios of > 1 Mt/year CO2, substantial displaced fluid production/treatment is essential to manage pressure and maintain the integrity of confining layers. The total dissolved solids concentrations of the formation fluids retrieved from the Madison Limestone range from 80,000 to 90,000ppm, and will necessitate customized water treatment strategies and facilities at the surface. The new data and upgraded evaluations demonstrate that the Rock Springs Uplift in southwestern Wyoming remains an outstanding large-scale geological CO2 storage site, and provides a realistic basis for designing commercial CO2 injection/storage operations on the Uplift.The 2010 U.S. Environmental Protection Agency Greenhouse Gas Reporting Program reports that in the Greater Green River Basin of southwest Wyoming, the CO2 emissions from stationary sources (sources that emit more than 25,000 tons of CO2 per year) total 29+ million tons annually, or approximately 50 percent of Wyoming's annual CO2 emissions. These CO2 sources include coal-fired power plants, gas and trona processing plants, pipeline compression stations, chemical production facilities, and gas-field complexes, among others. The Rock Springs Uplift in the center of the Greater Green River Basin is ideally located to serve as a large-scale commercial geological CO2 storage facility for half of all of Wyoming's industrial CO2 emissions. The new numerical simulations suggest that the Madison Limestone has the ability to permanently store the annual CO2 emissions from stationary sources in the Greater Green River Basin for 130 years (i.e., a total of 3.8 billion tons). The overlying Paleozoic Weber Sandstone on the Rock Springs Uplift has additional commercial-scale CO2 storage capacity.The Rock Springs Uplift has the attributes to serve as a regional CO2 storage site, and importantly, this site could be used as a storage/surge tank to supply CO2 to EOR projects throughout Wyoming.

Birth and demise of a Middle Jurassic isolated shallow-marine carbonate platform on a tilted fault block: Example from the Southern Iberian continental palaeomargin

Subbetic Middle Jurassic oolitic limestones of the Jabalcuz Formation crop out in San Cristóbal hill, near Jaén city (Andalucía, Spain), between hemipelagic limestone and marl successions. The Jabalcuz limestones range in facies from calcareous breccias and micritic limestones to white cross-bedded oolitic limestones. Recent erosion has exhumed a Jurassic isolated shallow-water carbonate platform on the San Cristóbal hill. This shallow platform developed on a tilted fault block. An almost continuous, laterally extensive outcrop reveals tectono-sedimentary features distinctive of block-tilting in the different margins of the fault block. The studied sections represent various palaeogeographic positions in the ancient shallow-water carbonate platform and basin transition. This exceptional outcrop allows to decipher the triggering mechanisms of the birth, evolution, and drowning of this Jurassic isolated shallow-water carbonate platform. Two shallowing-upward depositional sequences separated by flooding surfaces can be distinguished on two different sides of the fault block. In the southeastern part of the outcrop, proximal sections grade vertically from distal talus fault breccias, with bivalve and serpulid buildup intercalations, to white cross-bedded oolitic limestones defining the lowermost depositional sequence. Upwards, overlying a flooding surface, the second sequence with oolitic limestones prograding over micritic deposits is recorded. In the southwest, oolitic, peloidal, and more distal micritic facies alternate, with notable southeastern progradation of oolitic facies in the upper part of the section, which represents the upper depositional sequence. The top of this second depositional sequence is another flooding surface recorded by the sedimentation of marls with radiolarians from the overlying formation.In the northwestern outcrops, the two depositional sequences are also almost completely preserved and can be differentiated. A 100m-thick succession composed of a basal slumped unit of micritic and peloidal limestones overlain by cross-bedded oolitic limestones represents the lowermost sequence. The superposition of a newer slumped unit of micritic and peloidal limestones on the cross-bedded oolitic limestones defines the lower part of the uppermost depositional sequence. Finally, the central sections are less thick and comprise a facies succession consisting almost entirely of oolitic limestones.Locally, oolitic limestones often show cross-bedding and prograding clinoforms. The cross-bedding has centrifugal directions around the perimeter outcrops of San Cristóbal hill, whereas in the centre palaeocurrents are highly variable. The sense of the palaeoslopes as deduced from slumps also fits with a centrifugal pattern. Finally, in the southwestern outcrops, the demise of the carbonate platform is marked by backstepping oolitic facies, the presence of lumachelle facies, and onlapping hemipelagic facies.All the data point to the birth, evolution, and drowning of an isolated shallow-water carbonate platform that developed on a tilted fault block. The fault-block tilting controlled the development of talus breccias in the southeastern part and of slumps in the northwest-dipping hangingwall ramp. In the shallowest environments produced by the tilting (uppermost part of the fault block), a shallow-marine carbonate platform developed. Carbonate production (mainly oolitic) kept up with relative sea-level fluctuations and extended the platform at least to the northwest, southeast, and southwest based on observable data. Finally, tectonics and sea-level fluctuations drowned this carbonate platform.

A Breakthrough in Controlling Lost Circulation in a Pay Zone by Optimizing the Particle Size Distribution of Shellfish and Limestone Chips

The most common drilling problem experienced by drilling engineers is lost circulation, which results in great expense to oil companies because of either drilling fluid supply or subsequent drilling problems like pipe sticking. It becomes more challenging when dealing with heavy mud weights as high as 165 pounds per cubic feet (pcf). To resolve this problem, lost circulation materials (LCMs) are added to the drilling fluid in order to diminish mud loss rate to an acceptable level. Different types of LCMs in use in the drilling industry are employed based on the circumstance. The situation becomes worse when drilling in the reservoir section. In such intervals, the added materials should have the capability to be off the formation when the well is put on back flow or they should be soluble in acid in order to prevent reservoir impairment and reduction in productivity. In this study, it is tried to find the optimum size range of limestone and shellfish for use as LCMs in fractured and loose formations. Six different sizes of limestone and six different sizes of shellfish were used with four various slots and sleeves (simulating distinctive formations) for assessment of loss stopping efficiency. An oil-based mud in a bridging material testing apparatus was utilized at several differential pressures and temperature of 16°C, but because in overbalanced drilling a differential pressure of 200 psi is more likely to be employed, tests were conducted at a pressure of 200 Psig. After performing numerous tests with different sizes of LCMs, a remarkable decrease in mud loss was observed when using a particular size of LCM according to formation type and optimum LCM concentration.

Age constraints on the Neoproterozoic Baikal Group from combined Sr isotopes and Pb–Pb dating of carbonates from the Baikal type section, southeastern Siberia

Depositional ages for the middle part of the Neoproterozoic sedimentary succession exposed along Lake Baikal in the southern margin of the Siberian Platform have been constrained by the application of Sr isotope chemostratigraphy and Pb–Pb dating of carbonate rocks. The thick siliciclastic–carbonate Baikal Group is the type section of the regional Siberian succession. Although many of the Baikal Group carbonate rocks have undergone pervasive dolomitization by mixed meteoric-marine fluids, oolitic limestones in the 800-m-thick carbonate member of the Uluntui Formation preserve primary textures and high Sr contents (up to 3200ppm), suggesting that aragonite might have been the original precursor. The 87Sr/86Sr in the least altered high-Sr limestones (Mg/Ca<0.08 and δ18O>−8‰ PDB) range within 0.70842–0.70876, values we interpret as representing the best proxy for coeval seawater. Stepwise dissolution using 0.5N HBr was applied to enrich samples in primary carbonate from the Uluntui Formation and nine data points from the five least altered, high-Sr limestones yielded a Pb–Pb isochron age of 560±30Ma with MSWD=0.6 and probability=0.8. This age matches that inferred from Sr isotope stratigraphy (580–550Ma) and further supports the inference that the Baikal paleobasin was connected to the contemporary oceans. Our Sr chemostratigraphy and Pb–Pb isochron age of the Uluntui limestones cast doubt on previously proposed correlations of the Baikal Group as late Mesoproterozoic to Cryogenian. Instead, the data indicate that the entire siliciclastic–carbonate succession of the Baikal Group was most likely deposited during the Ediacaran (or Vendian, of the Russian Stratigraphic Scale).

The Wyoming carbon underground storage project: Geologic characterization of the Moxa Arch and Rock Springs Uplift

The Wyoming carbon underground storage project: Geologic characterization of the Moxa Arch and Rock Springs Uplift

Investigating the spatial and temporal boundaries of Hortonian and Hewlettian runoff in Northern Mexico

Summary Soil surface features strongly determine whether rain water will infiltrate or runoff. This results in a segregation between several kinds of hydrological functioning of hillslopes and catchments. Using a deterministic model, it is attempted to define the spatial and temporal boundaries of Hortonian (infiltration excess runoff) and Hewlettian (saturation excess overland flow) hydrological behaviour. The model allows to calculate the role of the antecedent precipitation index and the soil water holding capacity in the runoff yield. These factors depend on soil hydrodynamic properties. In Northern Mexico, data collected in four experimental networks are used: one in the sub-humid Western Sierra Madre, one in its semi-arid foothill, one in the centre of the endoreic Bolson de Mapimi (the southern part of Chihuahuan desert) and the last one on the southern edge of the latter, in a limestone range. There is a regional distribution of these parameters because of rainfall distribution and overall because of the whole ecological context. The value of α parameter (which determines the depletion time of soil water content) and the proportion of bare soils are the most important explaining factors of geographical segregation between Hortonian and Hewlettian contexts. This study determines that the Western Sierra Madre, with its temperate climate, is mostly characterized by a Hewlettian hydrology, despite an increase in Hortonian behaviour due particularly to land degradation. Inversely, as it is well known, Hortonian runoff dominates completely the semi-arid and arid areas; however in certain circumstances, saturation excess overland flow can appear due to landscape or local roughness, and local or temporal possibility to infiltrate a great proportion of rainwater, i.e. during low intensity–large duration events (hurricanes crossing the mountains, winter rainy events linked to El Nino Southern Oscillation configuration).

Color changes in architectural limestones from pollution and cleaning

AbstractThis article investigates the impact of sulfur dioxide attack, deposition of dark particles in urban environments and laser cleaning with Nd:YAG 1064 nm on color change in a range of ornamental limestones. We have used the CIELAB and CIELCH systems to compare the relative importance of the variation of each coordinate for the color change. Sulfur dioxide and dark particle deposition seems to increase the chroma, most particularly in the yellow component. Particle deposition also leads to an obvious darkening of stone surfaces. Laser irradiation at 1064 nm affects the red component of limestone, particularly if they already possess a reddish color. In general, the more intense the original color of the stone the greater are the chromatic changes, but the direction change of the color‐parameter affected by a particular process remains the same. It has always been apparent in an atmosphere heavily polluted with soot that the main changes to light‐colored stones are the exponential decrease in the parameter L* (darkening–blackening). This has important aesthetic and social implications. However, in the near future it may be that in cleaner atmospheres, perhaps more dominated by organic pollutants, a yellowing process may be of greater concern. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 320–331, 2007