Limestone Formation Research Articles

Mineralogy Impact on Acid Fracture Design in Naturally Fractured Carbonates.

The impacts of a natural fracture on the propagation of a hydraulic fracture has been extensively studied in the past decade. However, there were only minor attempts to understand the impact of natural fractures on acid distribution during acid fracturing. This study provides an understanding of the impact of natural fractures on acid fracturing designs in limestone and dolomite formations. A built-in-house model that solves fracture propagation, acid transport and dissolution, heat transfer, and reservoir productivity was utilized. A sensitivity analysis was conducted to investigate the impact of temperature, injection rate, and acid type. One of the significant differences between limestone and dolomite is the dissolution profile in the hydraulic fracture. The maximum dissolution happens close to the wellbore in limestone, but far from the wellbore in dolomite at low acid temperatures. Also, the hydraulic fracture in dolomite could have lower conductivity (i.e., permeability) compared to the intersecting natural fractures, which is not usually the case in limestone. Hence, the productivity enhancement by acid fracturing in limestone formation is higher than in dolomite. In general, natural fractures reduce productivity, and their negative impact is more significant in dolomite. The sensitivity study showed that the acid temperature significantly impacts fractured well productivity of dolomite, especially at high reservoir permeability where higher dissolution is desired. It is observed that the optimum injection rate that maximizes productivity is much higher in limestone than in dolomite. Also, acid retardation does not positively impact the productivity of dolomite compared to limestone; however, high viscosity might be needed to keep the hydraulic fracture open. This is the first study to reveal mineralogy's impact on acid fracture performance in naturally fractured carbonates.

Mineralogical and geochemical characterization of the Wonosari formation limestone at Gunungkidul Indonesia as preliminary investigation of Portland cement raw material

Mineralogical and geochemical investigations were carried out to determine the characteristics of limestone in the Wonosari Formation and to suggest its depositional environment and a preliminary study for the properties of Portland Cement. The study was conducted at Ponjong Area, Gunungkidul Regency, Daerah Istimewa Yogyakarta, Indonesia. The outcrop in this study area is composed of Wonosari layered limestone. Based on the facies interpretation in the research area, there are three depositional units: packstone, wackstone, and grainstone. This area’s depositional environment is the back reef lagoon and sand apron zones that are not related to the open sea. According to XRF data, limestone showed a reasonably high composition of CaO compounds, about 53.78% - 59.09%. Most limestone samples were classified as good quality as Portland Cement Raw Material due to CaO content >49%. The MgO, SiO2, Al2O3, Fe2O3, SO3, K2O, Na2O, TiO2, and P2O5 compounds also fulfil the Indonesian National Standard (SNI-15-2049-2004). Geochemical content shows limestone has a higher grain percentage than the matrix. The utilization of limestone in research area are expected to be a reference for the development of natural resources in the future that pay attention to the environment for mutual sustainability.

A unique suit of Wuchiapingian marine red beds in central China representing a specific paleogeography and paleoclimate association

Marine red beds (MRBs) as a special geological phenomenon have been considered relevant to specific palaeogeographic or paleoclimatic conditions. The Wuchiapingian Yundoutan Formation in Xikou, Shaanxi, Central China is characterized by a huge thick succession of red limestones, which is a unique deposition among marine strata of China during the Wuchiapingian. The lithology, mineralogy, and geochemistry features of the Yundoutan Formation MRBs were analyzed by using techniques of field measurement, polarized optical microscope, field emission scanning electron microscope (FESEM), diffuse absorbance spectroscopy (DAS), X-ray diffraction (XRD), and geochemical analysis, which were used to discuss their origin and palaeogeographic and paleoclimatic responses. The results show that the stain mineral for the MRBs is mainly weakly-crystalline hematite which can not be observed in the FESEM but was detected from the DAS first derivative spectra with featured peaks around 570 nm. The similar trend of Fe with refractory elements and the strong positive correlation between Fe and Al suggest Fe is mainly a terrestrial source. Limestones of the Yundoutan Formation contain different colors including red, light gray, and dark gray. Red limestones have comparable contents of Fe with dark gray limestones, which are larger than that of light gray limestones, but they are depleted in redox-sensitive elements (Cr, Ni, Cu, Zn, Mo, U) and riched in Fe(III) compared with dark gray limestones. Those indicate that the formation of red limestones needs both enough terrestrial Fe and strong oxic conditions. A mechanism proposed for the formation of red limestones was that Fe was transported from the highlands, which were then deposited under a strong oxic environment and transformed into hematite. We suggest the Wuchiapingian MRBs formed in Central China represent a unique paleogeography and palaeoclimate association. During that time, the study area attached to the northern margin of the United North China-Qinling Block received terrestrial materials from its northward highlands, which provided Fe under a warm climate. Meanwhile, the study area located between the South and North China blocks was on the narrow seaway connecting the Palaeotethys and Panthalassa, which produced relatively fast exchanging rates of seawater and thus a high content of oxygen that can easily transform terrestrial-sourced Fe into hematite. The gradual transition among color-different limestones may be driven by the changes in rainfall that influenced river transportation on terrestrial materials or sea-level changes that influenced the redox state of the water-sediment interface.

Ichnological evidence of marine incursions in the lacustrine–palustrine Bembridge Limestone Formation (Eocene), Isle of Wight, southern England

Trace fossils are described from the Eocene Bembridge Limestone Formation from the Isle of Wight and used to constrain the paleoenvironmental interpretation. The lacustrine–palustrine succession contains three limestone beds, which are separated by clay and marl. The middle and upper limestone beds reveal complex burrow systems developed at their top. Based on their characteristics, these burrow systems are assigned to the ichnotaxon Balanoglossites triadicus Mägdefrau, which is associated with the shallow superficial grooves Sulcolithos variabilis Knaust. B. triadicus is a common marine trace fossil mainly known from shallow-marine carbonate successions throughout the Phanerozoic. It is accompanied by other marine ichnotaxa such as Arachnostega gastrochaenae Bertling, Gastrochaenolites isp. aff. G. ornatus Kelly and Bromley, Spongeliomorpha iberica Saporta and Thalassinoides suevicus (Rieth). This ichnological evidence confirms the occurrence of short-term marginal-marine incursions in a predominantly lacustrine to palustrine environment.

EOCHEMICAL, MINERALOGICAL AND DIAGENETIC CHARACTERISTICS OF MARINE CHERT IN THE HATAY REGION, S-TURKEY: ITS ORIGIN AND DEPOSITIONAL ENVIRONMENT

Trace elements and rare earth elements (REEs) were studied to determine the formation of chert and siliceous limestones, which are predominantly observed in the Okçular formation. Cherts are divided into four types according to their varying forms depending on the deposition and diagenesis stages: (Type-I) layered cherts formed by direct precipitation from sea water, (Type-II) nodular cherts with rim formed by replacement, (Type-III) homogeneous chert nodules without rim, (Type-IV) chert micro nodules with high porosity. The porosity of stylolite-fracture networks and the chemical composition of seawater played a role in the formation of different types and sizes in cherts. The rim of Type II nodular cherts has significant color changes and porosity up to 20%. Anomalies of major and trace elements, especially La, Y, Sc, Ce, Th, U and Gd values, indicate direct deposition and replacement of early diagenetic pelagic deposits of cherts in the oxidized marine environment. Total (REE)+Y values, high LREE/HREE ratio and low Ce values indicate that dissolved seawater of chemical or biogenetic origin has a role in silicification. According to the similarity of the hierarchical cluster analysis of the chemical contents of the Okçular formation and the ophiolites, the silicon in the chert formation originates from the ophiolites.

Another piece in the puzzle of mantis shrimp evolution – fossils from the Early Jurassic Osteno Lagerstätte of Northern Italy

Mantis shrimps (Stomatopoda Latreille, 1817) are marine predatory crustaceans of the group Hoplocarida Calman, 1904 with an interesting, though incompletely known, evolutionary history. Here we introduce a new species of fossil mantis shrimps, Ostenosculda teruzzii n. gen., n. sp. from the Early Jurassic (Sinemurian) limestone formation of Osteno (Northern Italy). We present distinctive features that characterize the specimens as a new species, such as a unique arrangement of maxillipeds 2-5 (maxilliped 2 is the major raptorial appendage). We also present a phylogenetic systematic interpretation of the species based on the available features of morphology and body organisation. The unusual arrangement of the maxillipeds appears to represent a plesiomorphic condition relative to extant mantis shrimps: the maxillipeds are arranged in an almost straight anterior-posterior line, with rather large distances between them. This contrasts with extant forms and slightly younger fossils of about 150 million years old lithographic limestones (Late Jurassic) where further anterior maxillipeds are inserting far laterally and further posterior ones more medially, with very small distances between the next posterior ones. The herein studied specimens are the first of their kind to be confirmed for this period and geographical region and further close gaps in our understanding of the evolution of mantis shrimps.

Quantitative analysis of species distribution of the Mississippian Zaphrentites delanouei group from the Vale of Glamorgan, UK

The evolutionary process of anagenesis is thought to control distributions of members of the Zaphrentites delanouei species group, the Tournaisian‐Viséan solitary rugose corals, within the Carboniferous Limestone. We present alternative interpretations specific to the Friars Point Limestone Formation, which point to composite evolutionary processes closer to anacladogenesis. We use a Markov Chain Monte Carlo process to organize fossils into matrices representing states of concurrence, where concurrence is the number of species coexisting in each bed. We analyse their distributions according to transitions between states. Data testing by matrix multiplication shows whether stochastic equilibrium or convergence is reached, to determine probabilities of species coexistence. Taking the probabilities from the Markov Chain Monte Carlo process to represent the first generation of a branching process, we proceed to calculate the second to fourth generations. Finally, we model these values in a Galton–Watson process to determine the likelihood of ultimate extinction, and whether the species belong to the same population without immigration or emigration. Results show that the species distribution is both anagenetic (0.725) and cladogenetic (0.275). Therefore, we define the evolutionary process as anacladogenetic with the potential for up to eight species in addition to the six defined in the literature. This represents some evidence for a population unaffected by immigration or emigration, with a high likelihood of ultimate extinction for most localities. We deduce that second or third‐generation concurrences are a requisite for survival, even with anacladogenesis. As an environmental corollary, the amplification of extinction rates was exacerbated within a regressive marine system, and our techniques will allow further exploration of evolutionary mechanisms and energy within coral ecosystems.

A review of the water resources of Ghana in a changing climate and anthropogenic stresses

An extensive narrative review approach is adopted to present existing information on the consumptive and non-consumptive uses and their related issues, such as floods and droughts, climate and the environment in Ghana. Total annual rainfall in the country ranges between 800 mm/y (south-east coat) and 2,000 mm/y (south-west coast) with a bimodal and mono-modal patterns in the south and north, respectively. Annual total runoff from the 3 river systems (the Volta river system, the South-western river system and the Coastal river system) in Ghana is estimated at 40 billion m3 out of about 53 billion renewable freshwater resources. Groundwater yields ranges from 6 m3/h in the Volta basin sedimentary formations to 180 m3/h in the limestone formations. It is estimated that the total water withdrawal as a percentage of total renewable water resources is about 2%. At an average per capita consumption of water of 50 l/p/d, estimated daily water demand for the 2021 population of 31 million people stands at about 566 million m3/y. Current water supply systems are overstretched and it is further estimated that about US $ 240 million is required per year as capital expenditure in urban and rural water supply. Moreover, climate change is projected to increase the scarcity of water in future. Wastewater generated through domestic and industrial uses including storm water in urban Ghana is estimated at about 760 million m3/y. Ghana's irrigation potential to reduce climate change impact on agriculture is put at between 0.36 and 2.9 million ha, accounting for about 66.4% of the consumptive water withdrawal. Estimated water demand for cattle, sheep and goats in 2010 was put at about 22 million m3/y. Other services obtained from surface water are the provision of fish (the Volta Lake is estimated to contributes to 16% of total catch in Ghana); hydropower generation accounting for about 40% of total power installed capacity (Akosombo = 1,020 MW, Kpong = 160 MW, and Bui = 404 MW); water transportation (notably on the Volta Lake); tourist attractions [are 550 km Ghana's shoreline that has about 90 lagoons, the Volta Lake, the lower Volta (e.g., Sogakope, Ada) and some other inland waters like Lake Bosumtwi] and wetlands (recognized by RAMSAR convention of 1971) In the legal context, water governance issues are handled by various institutions created by Acts of Parliament.

New records and specimens to the Badenian fish fauna of Nyirád (Hungary), including the first report of Galeocerdo cuvier from the Middle Miocene of Europe

The Nyirád I. outcrop is extremely rich in fossils of marine vertebrates, including chondrichthyans, osteichthyans and marine mammals. Rarely, remains of terrestrial vertebrates are also found. The present paper adds important data to the vertebrate faunal list of the two Badenian formations of the outcrop, namely the Pusztamiske and Leitha Limestone Formations. Altogether, remains of 38 chondrichthyan and 13 osteichthyan taxa, cetaceans and two terrestrial tetrapods have been documented from the outcrop so far. The most important new result is the occurrence of teeth most similar to those of the tiger shark Galeocerdo cuvier. Th is data provides the first evidence from the Badenian of the Central Paratethys for the co-existence of two species of the genus Galeocerdo in the same habitat. With 141 figures and 1 table.

Geochemistry and petrogenesis of Late Permian basalts from the Sichuan Basin, SW China: Implications for the geodynamics of the Emeishan mantle plume

Plume-lithosphere interactions are significant in the formation of Large Igneous Provinces (LIPs). The Permian Emeishan Large Igneous Province (ELIP) is considered to be the result of a mantle plume. The Emeishan flood basalts comprise a major part of the ELIP and they define three zones: the inner, intermediate and outer zones. Both high-Ti and low-Ti basalts are present in the inner zone, whereas only high-Ti basalts are found in the intermediate zone and outer zone. However, there are only sparse outcrops in the outer zone, and so geochemical data on basalts from the outer zone are rare and the role of plume-lithosphere interaction in the petrogenesis of volcanic rocks in the outer zone remains poorly understood. In the Sichuan basin, the Basalt Formation is found between the Permian Maokou Formation limestone and the Longtan Formation marl in some drill cores as well as in outcrops in the basin. This relationship demonstrates that the basaltic layer in the basin is part of the Emeishan flood basalts. These basalts have TiO2 contents of 3.7–4.2 wt% and Ti/Y ratios of 604–720, being high-Ti sub-alkaline basalts. They display chondrite-normalized rare earth elements (REE) patterns enriched in light rare earth elements (LREE) relative to heavy rare earth elements (HREE) and have elevated large ion lithophile elements (LILE) and high field strength elements (HFSE). Lead isotope ratios are high (206Pb/204Pb(t) = 18.102–18.392, 207Pb/204Pb(t) = 15.578–15.606, 208Pb/204Pb(t) = 38.410–38.850), and εNd(t) values are −0.38 ∼ 1.17. Detailed petrology and geochemistry suggest that the high-Ti basalts from the Sichuan Basin did not experience significant contamination of crustal and lithospheric mantle material during the ascent of magma. We infer that these basalts resulted from low-degree melting of the plume mantle source and underwent fractional crystallization of clinopyroxene. The distribution and petrogenesis of the Sichuan Basin basalts in the outer zone are different from those of the basalts in the inner zone and there are clearly different plume-lithosphere interactions in different parts of the ELIP. In the inner zone, the temperature of the lithosphere mantle was markedly elevated due to underplating of the mantle plume, causing a substantial quantity of lithosphere mantle melting and the initial formation of low-Ti basalts. This was followed by melting of the mantle plume and the formation of high-Ti basalts. In the outer zone, lower temperatures further from the plume centre were insufficient to generate extensive melting of the lithospheric mantle. Consequently, only the mantle plume melted in the outer zone, resulting in the formation of high-Ti basalts with minimal lithospheric input.

Effect of diagenetic events on limestone reservoir quality: Case study of Parigi formation, Northwest Java basin

Limestone is a sedimentary rock with high heterogeneity. This is triggered by diagenetic processes that affect the quality of limestone during its formation. The high uncertainty in limestone porosity values is also influenced by diagenetic processes. The Parigi Formation is a carbonate rock located in the Northwest Java Basin and has been proven to be a carbonate reservoir rock. Petrographic analysis was conducted to observe the appearance resulting from diagenetic processes. The studied area's limestone has two facies: clastic facies and reef facies. The limestone of clastic facies is white to greyish, consisting of skeletal fragments or shell fragments, with some places contains fragmented coral fragments. It is grain-supported, massive, poorly sorted, with fragment sizes ranging from 1mm-8mm and in some places 10cm-20cm. The reef facies of limestone are generally white to greyish colour, compact/massive, without cavities, and shows the body structure of coral/reef. The processes occurring in the Parigi Formation limestone, based on thin-section data, include cementation and neomorphism, which are commonly found in thin section LP 7 and LP 10. Cementation and neomorphism lead to a decrease in porosity in the limestone. Samples LP 1 - LP 5 show extensive dissolution, resulting in vuggy cavities/porosity. These limestone samples have high porosity values. The transformation of fossils into new crystals or recrystallization processes also reduces the limestone's porosity. Some samples also show that the cavities in the Parigi Formation limestone have been filled by calcite cements, thus closing the pores. This leads to poor quality limestone. In conclusion, the heterogeneous nature of limestone is significantly influenced by diagenetic processes. Petrographic analysis of the Parigi Formation limestone revealed the occurrence of cementation, neomorphism, dissolution, and recrystallization processes, all of which have implications for porosity and reservoir quality.

Carbonate platform architecture and carbon isotope stratigraphy from the neoproterozoic Narji limestone formation, Kurnool Group, India: Decoding clues of relative sea level fluctuations

From a detail process-based facies and facies association analysis in a spatio-temporal framework, a rimmed shelf platform geometry is proposed for the Neoproterozoic Narji Limestone Formation, Kurnool Group, India. Ten carbonate facies types were delineated and clubbed under seven facies associations belonging to four different paleogeographic settings viz. Forereef (intertidal to shallow subtidal and shallow to deep subtidal), peritidal reef and back-reef lagoon. Whereas crinkly microbial laminites with subordinate domal stromatolites constitute the reef part, the fore slope deposition in the platform largely remained tide-and storm-dominated. Grey to black colored pyrite bearing bedded limestone-shale alternation without any current or wave imprint represents the back-reef lagoon deposition. A high carbonate saturation and productivity in the Narji inner and mid shelf is suggested from an overall dominance of microalgal laminite and microdigitate stromatolites over columnar stromatolites. From documentation of decimeter-to meter-thick shallowing-upward depositional hemicycles, embedded within an overall aggradational Narji lithosuccession, a combined control of sea level and carbonate productivity is inferred in course of Narji sedimentation. A short-duration medium-to large-scale rise in the base level led to the aggradation in shallow water rim of the Narji platform margin; interruption of this overall motif by short thickening- and shallowing-upward progradational hemicycles bear testimony for higher productivity in the Narji mid-to inner shelf areas. The present study intends to correlate shallowing-upward hemicycles with keep-up to catch-up depositional cycles with signature of apparent sea level fall. The control of relative base level variation in Narji depositional history is strengthened with multiple signatures including secular δ13C composition, total organic carbon (TOC) content and siliciclastic content documented from the entire Narji litho-succession.

Lost circulation pattern in the vug-fractured limestone formation

Due to numerous leakage zones, such as vugs, fractures, and caves appearing in carbonate rocks, lost circulation, the main issue, restricts safe and effective drilling. The lost circulation pattern of the vug-fractured limestone formation has been extensively studied using the Mishrif formation of the H oilfield in the Middle East as the research sample. The equivalent physical models of three different types of leakage zones, including vug, natural fracture, and induced fracture, were built based on the interpretation of FMI (Formation MicroScanner Image) logging. By embedding discrete fractures into a variable permeability matrix and solving it using the finite element method (FEM), a three-dimensional fluid–solid coupling mathematical model of mud loss rate was established. The study focused on the effects of drilling fluid performance parameters on lost circulation as well as the parameters of the single leakage zone (vug, natural fracture, or induced fracture) on lost circulation. Additionally mentioned were the variable characteristics of mud loss rate and cumulative mud loss volume in various combined ways of leakage zones. The findings indicate that there are considerable differences in how various types of leakage zones affect lost circulation properties. Fractures, particularly induced fractures, can result in more severe lost circulation than those brought on by vug for the creation of a single leaking zone. Mud loss rate and cumulative mud loss volume are greatly influenced by fracture width and dissolved radius, both of which have thresholds. Due to the enhanced flow conductivity, the lost circulation is more severe the more complicated the leakage zone combination mode is. The numerical model developed in this research provides a new perspective on how to analyze the lost circulation pattern of vug-fractured limestone formations and provides theoretical direction for lost circulation control of drilling in this kind of formation.

Spatial distributions of microbial diversity in the contaminated deep groundwater: A case study of the Huaibei coalfield

The impact of coal mining activities on the structure of groundwater microbial communities in coal mining areas has gradually received academic attention. In this study, hydrochemical analysis and sequencing of the V4 region of the 16S rRNA gene were carried out using groundwater samples from the fourth aquifer in the loose layer of Cenozoic, the sandstone fissure aquifer in the coal measure strata of Permian, the Carboniferous Taiyuan Formation limestone aquifer, and the Ordovician limestone aquifer, at depths of 250 m, 600 m, 750 m, and 1000 m in monitoring wells. Results showed that the operational taxonomy units (OTUs) in the deep groundwater ecosystem were clustered distinguishably between the contaminated and the uncontaminated aquifers. The microbial community alpha-diversity of groundwater was significantly correlated with depth, and the richness of microbial community composition decreased with increasing depth. Proteobacteria (34.41%–97.41%), was found to be the dominant phylum, Gammaproteobacteria (10.05%–92.06%) was the dominant class and “Unassigned” (4.12%–64.72%) was dominant at the genus level. The number of endemic bacteria in the four aquifers was 1, 33, 99 and 11, respectively. It was also found that F−, oxidation-reduction potential (ORP), and TOC were the main environmental variables affecting the groundwater all OTUs, abundant OTUs, and rare OTUs, respectively. These results indicate that the activity of rare OTU subcommunities increases gradually with increasing aquifer depth and that mining significantly enriched Thiovirga in deep groundwater. In addition, it was found that with the increase of depth, the effect of ORP on microbial community abundance decreased. This study deepens our understanding of the evolution characteristics of microbial communities in deep groundwater in coal mining areas. The unique characteristics of microbial communities characteristics of four aquifers with different depths provide a microbial perspective for understanding the characteristics of deep aquifers.

An integrated palynofacies, geochemical and petrophysical analysis for characterizing mixed organic-rich carbonate and shale rocks of Dhulian oilfield Potwar Basin, Pakistan: Insights for multiple source and reservoir rocks evaluation

The current study aimed to evaluate potential of multiple source and reservoir rocks of Potwar Basin, Pakistan. This study presents palynological, geochemical, and petrophysical data from source and reservoir rocks of Eocene and Paleocene sequences of the Dhulian oilfield. A total of 34 well cutting samples from two wells and four fresh outcrop samples were studied. Results of total organic carbon and Rock-Eval pyrolysis of the Sakesar Formation sediments shows good to very good TOC contents, whereas the Patala Formation sediments from well A shows very good to excellent and very good TOC contents in well B. S2 values of both formations’ samples showed fair to good generation potential. Both formations appear mature and have primarily type III and mixed type II-III kerogen with good gas-generation potential. Palynological analyses are in agreement with the pyrolysis data and showed that sediments have type III kerogen in the oil/gas window having excellent gas generation potential. Three kerogen assemblages were identified: palynomorphs, phytoclasts, and amorphous organic matter. Petrophysical analysis of the Chorgali Formation limestone showed an average porosity of ∼10.6%, with an average water saturation of ∼33.72%, and an average hydrocarbon saturation of ∼66.28%, thus indicating average to good reservoir potential. The findings of this research will help and guide exploration and production companies in the Potwar Basin in terms of source rock organic richness and maturity.

Metallogenic process of Permian Taiping karstic bauxite deposit in Youjiang Basin, China

More than 1 billion tons of bauxite was formed on the karstic surface of the Permian Maokou Formation limestone in the western Guangxi area of Youjiang Basin (YB). However, its formation mechanism is still a matter of debate. In this study, the Taiping bauxite deposit, a representative large deposit in this area, was selected to carry out detailed mineral microanalysis and pyrite sulfur isotope analysis to further understand the metallogenic process of bauxite in this region. Taiping bauxite contains two layers: the lower bauxite layer and the upper claystone layer. Bauxite ore was mainly composed of diaspore, pyrite, anatase, kaolinite, minor pyrophyllite, parisite, and bastnäsite. Small amounts of detrital moissanite, native boron, and zircon were also found in the ore. The claystone was dominated by kaolinite, diaspore, pyrite, and chlorite. The occurrence of detrital zircon, moissanite, and native boron suggests that they were most likely derived from volcanic ash or lava, further confirming the contribution of volcanoes. The mineral assemblages of diaspore, pyrite, anatase, parisite, and bastnäsite in the bauxite ore indicate alkaline and reducing depositional environments. The extensive development of ovoid microorganisms and the significant negative δ34S values of pyrite (−42.80 ‰ to −12.54 ‰) indicate that microorganisms were involved in the formation of bauxite. This view was further confirmed by the wide development of fine pyrite (∼1 μm) cemented by cryptocrystalline diaspore in the ore. Extensive volcanism promotes the weathering of parent rocks, releasing Al3+, Fe3+, Ti4+, and REE3+ ions into the weathering system. Under strongly acidic and oxidizing conditions in the upper part of the weathering profile, these ions can migrate downward until they reach an alkaline and reducing environment on the carbonate surface. A large amount of diaspore, pyrite, anatase, parisite, and bastnäsite was formed near the karstic surface with the participation of microorganisms. Epigenetic modifications were also evident in the widespread development of kaolinite and pyrophyllite formed by the silicification of diaspore.

The origin and transfer of water and solutes in peatlands: A multi tracer assessment in the carbonated Jura Mountains

AbstractPeatlands provide a large panel of socio‐ecosystemic services such as biodiversity, water and carbon storage and amenities. Hydrological and geochemical interactions between peats and their surroundings are expected to be favoured in mountainous areas, which are nowadays increasingly sensitive to climate changes. In order to provide an integrated scheme of potential interactions, this study evaluates spatio‐temporal patterns of environmental tracers (87Sr/86Sr, δ18O/δ2H, elemental ratios) during high‐ and low‐flow periods in the largest peatland complex of the Jura Mountains (France). Systematically depleted δ18O/δ2H values in the deepest peat pore waters suggest contrasted dynamics and origins, both compatible with either preferential winter recharge or supply from adjacent high‐elevation areas. Combined with strontium isotopes (87Sr/86Sr), we show that these water fluxes are purveyors of solutes derived from water‐rock interactions, modified by mixing, evapotranspiration and dilution with local meteoric inputs. An end member mixing analysis of the peat pore water solute composition is consistent with a major contribution of carbonates from the regional Cretaceous limestone formations, located beneath fluvio‐glacial Quaternary deposits underlying the peat. This contribution implies a significant upward water flux from the underlying syncline that could reach a sufficient hydraulic head thanks to recharge from an adjacent regional anticline. These multiscale (anticline‐syncline, syncline‐peatland, peatland‐surface) constraints allow us to propose a relevant scheme for the hydrogeochemical functioning of the peatland, enabling an improved understanding of the current high socio‐ecosystemic value of the area, and the potential future evolution of the related services.

Discovery of Late Mississippian (late Serpukhovian)-Early Pennsylvanian (earliest Bashkirian?) foraminiferal assemblages from the Sanandaj-Sirjan Zone, Iran: Biostratigraphic and palaeoenvironmental implications.

This study reports the new discovery of relatively abundant foraminiferal faunas from the upper Serpukhovian-lowermost Bashkirian? of the Ghaleh Formation in the Shahreza region of the Sanandaj-Sirjan Zone, Iran. Four successive assemblages spanning the upper Serpukhovian-lowermost Bashkirian? are proposed: (1) Assemblage with Biseriella minima and Eostaffellina paraprotvae; (2) Assemblage with Bradyina cribrostomata; (3) Assemblage with Parastaffella utkaensa and Plectostaffella spp., (4) Assemblage with Plectostaffella ex gr. varvariensis. The newly discovered foraminiferal assemblages of the Sanandaj-Sirjan Zone have some species in common with assemblages of the Russian Platform, Donets Basin, Urals, and Western Europe. Ikensieformis aff. mirifica, and Eostaffella igoi, and a new species Ikensieformis persiaensis sp. nov. are described. The microfacies analysis of the Ghaleh Formation limestones suggests a moderate to high-energy shallow marine warm environment, more likely of the inner ramp.

Geology, geomorphology and geochronology of the coseismic? Emad Deh rock avalanche associated with a growing anticline and a rising salt diapir, Zagros Mountains, Iran

This work documents for the first time the prehistoric, but morphologically pristine, Emad Deh rock avalanche of the Zagros Mountains. The ca. 420 Mm3 rock avalanche was initiated as a rockslide on a dip slope affecting a weak unit of marls with interbedded limestones overlain by a thick and competent limestone formation. The slope is located on the northern limb of the growing Gavbast Anticline and at the edge of the inflating Gavbast Dome, related to a buried salt diapir of Hormuz salt. The unconfined rock avalanche deposits, covering 32 km2, were accumulated on coalescing alluvial fans and a floodplain environment. The depositional lobe shows sectors with distinctive morphological features attributable to the variable flow-depositional behavior of the debris stream, controlled by the nature of the substrate: (1) proximal continuous breccia flanked by levees; (2) intermediate depression; and (3) flat-topped polygonal hills and conical hills. A morphometric and spatial distribution analysis has been performed with the 550 conical hills (hummocks) mapped in the distal sector. The rock avalanche, with 914 m of maximal height drop (H) and 9280 m of runout (L), displays an extraordinarily high mobility (H/L index of 0.09), that can be attributed to the combined effect of dynamic rock fragmentation and basal lubrication by the soft substrate in the floodplain. Relief rejuvenation and slope over-steepening related to the growth of the anticline and the inflation of the Gavbast Dome are considered the main long-term preparatory factors that shifted the slope to a state of marginal stability. The slope failure was likely triggered by a large M ≥ 6.5–7 earthquake at ca. 5.4 ka, as indicated by OSL ages obtained from folded alluvium situated just beneath the rock avalanche deposit. The source of the earthquake was probably a blind reverse fault situated beneath the asymmetric Gavbast Anticline, as support the structural and geomorphic features of the fold. The identification and dating of large coseismic landslides in the Zagros Mountains, where large earthquakes are rarely accompanied by primary surface ruptures, could help to improve both landslide and seismic hazard assessments.

MIDDLE TRIASSIC (ANISIAN) CEPHALOPODS FROM THE MECSEK MOUNTAINS, HUNGARY

Recent nautiloid and ammonoid finds from the Middle Triassic Zuhánya Limestone Formation in the Mecsek Mountains (south Hungary) proved that the formation encompasses the whole Pelsonian and the lower Illyrian substages of the Anisian Stage. On the basis of 11 identified ammonoid species, the Balatonicus and Trinodosus zones have a complete record. The stratigraphical position of the Zuhánya Limestone on the whole corresponds to the Felsőörs Limestone in the Balaton Highland. The palaeobiogeographical evaluation of the cephalopod fauna showed that the elements of the nautilid fauna point mostly to Germanic and partly to Sephardic affinity. On the other hand, the ammonoid fauna has no Germanic elements; most of the species are Alpine in character, while the species Procladiscites brancoi indicates Dinaridic connection, or at least an occasional appearance of pelagic organisms. These results endorse the previous palaeogeographical assumption and suggest that during the Middle Triassic the Mecsek succession was situated along the European shelf, between the Vindelician-Bohemian Land and the open Tethyan Ocean.