Calcareous Sandstone Research Articles

Vertebrate taphonomy and taphofacies of the Capianga Member, Aliança Formation (Jurassic), Jatobá Basin, Brazil

In addition to the study of sedimentary facies, the reconstruction of paleoenvironments depends on a detailed understanding of the taphonomy of a fossil accumulation. The Capianga Member of the Aliança Formation (Middle to Late Jurassic of the Jatobá Basin, northeastern Brazil) reveals vertebrate fossil accumulations composed predominantly of disarticulated bone and osteoderms, scales, spines and isolated teeth from a lacustrine paleoenvironment. However, the taphonomic history of the accumulation has not yet been studied extensively. The present work aims to interpret taphonomic facies based on lithological data and the systematic collection of fossils from the Capianga Member of the Aliança Formation, located in the northeastern portion of the Jatobá Basin, mainly in the municipality of Ibimirim. Six lithofacies were identified: Fm – massive claystones, Fl – Shale laminated Lt – calcilutites, Lc – calcarenites, Gf – fibrous gypsum and Scl – calciferous sandstones. Two primary taphonomic classes were recognized, consisting essentially of disarticulated elements, including (1) incomplete, semi-complete, or rarely complete bioclasts (such as osteoderms and fish scales) and (2) small-sized, occasionally complete bioclasts (osteoderms and scales) that sometimes compose bonebeds. According to the vertebrate taphonomy characteristics, three taphofacies were identified, with the Taphofacies A and B occurring in calcarenites and the Taphofacies C in calcilutites. The interpretation of these taphofacies reveals a multi-episodic history of the lacustrine environment. The integrated model suggests that the genesis of the identified taphofacies is linked to the action of lowering the water level of the paleolake, as well as the agents responsible for transport and disarticulation. These agents are related to pre-burial sub-aerial exposure, the action of unidirectional turbidity currents in shallow waters, and the likely influence of storms.

Characteristics and Control Factors of a High-Quality Deeply Buried Calcareous Sandstone Reservoir, the Fourth Member of the Upper Xujiahe Formation in the Western Sichuan Basin, China

A special type of sandstone in which carbonate rock fragments (CRFs) dominate the composition developed in the Upper Triassic Xujiahe Formation’s fourth member (Xu4) in the western Sichuan Basin, known as calcareous sandstone. Calcareous sandstones are widely distributed in the western Sichuan and is the main production target of tight sandstone gas in the Sichuan Basin. In this study, thin sections, porosity–permeability testing, scanning electron microscopy, and X-ray diffraction are applied to examine the characteristics and control factors for high-quality reservoirs in the calcareous sandstones, with a view to providing guidance for natural gas exploration and development in calcareous sandstones. The results show that the calcareous sandstone belongs to litharenite, with an average framework grain composition of 30% quartz, 1% feldspar, and 69% rock fragments, while the Xu4 sandstone has a high quartz content (average content of 71%). Primary intergranular pores are the main storage space, and the reservoir quality is quite poor. Under the influence of different parent rock properties of sandstones, there are obvious differences in the composition of framework grains between the calcareous sandstone and the ordinary Xu4 sandstone, which in turn affects the reservoir storage space, diagenesis, and reservoir quality. High-energy depositional conditions, low content of late cements, and the development of fractures are the main controlling factors for the formation of high-quality reservoirs in Xu 4 calcareous sandstones.

Microbialitic third-order Rupelian cycles of the Kuwait Formation, and their global correlative surfaces

The microbialites identified in the Kuwait Formation (also known as the Kuwait Group) at the Jal Az-Zor escarpment were largely misclassified as calcrete beds. Through detailed geological field observations, five distinct microbial beds have been identified and are found to occur at the end of each depositional cycle. Over these cycles, three main facies have been identified; these are bioturbated cross-bedding, calcareous sandstones, and microbial facies. The combination of field and petrographic analyses indicates that these sequences are dominated by siliciclastic facies, with microbial facies primarily manifesting as thrombolites or laminites, with the former being more common. Mineralogical analysis of the microbial facies indicate that over 60% of this facies is composed of calcite, and energy dispersive spectroscopy measured a significant percentage of organic carbon that reached up to 39.3% wt. Scanning electron microscope imagery of the microbial facies identified filamentous bacteria and flagellates as the principal constituents of these microbial assemblages. The bioturbated cross-bedding facies is found to be deposited in an estuarine central bay, the calcareous sandstone facies is deposited in an estuary mouth bar system that transitions laterally into a shoreface setting, and the microbial facies is deposited in a peritidal setting. Strontium isotope (87Sr/86Sr) dating of the five microbial beds indicates that these beds were deposited at 33.99 Ma, 32.6 Ma, 31.5 Ma, 30 Ma, and 29 Ma, respectively, suggesting that the associated sequences are of a Rupelian 3rd order hierarchy. Our analysis correlates the Jal Az-Zor sequences with New Jersey's Oligocene oxygen isotope sequence boundaries and the La2004 obliquity nodes, suggesting a continued uplift rate during the Rupelian age at the studied area. This article challenges the assumption that the Oligocene success is absent in Kuwait and the surrounding region, opening the door for further assessment of these deposits.

A new fusulinid species from the early Permian of northwestern Peninsular Malaysia: Evidence of the Artinskian warming event in the eastern Peri-Gondwanan Sibumasu Block

A new species of Crenulosepta, i.e., Crenulosepta perlisensis Vachard and Fassihi sp. nov., is described from a Cisuralian (Lower Permian) sandy limestones and calcareous sandstones in the Kubang Pasu Formation in northwestern Peninsular Malaysia, which forms part of the Peri-Gondwanan Sibumasu Block. Previous Malaysian authors reported the occurrence of Monodiexodina shiptoni and Monodiexodina sutschanica from the same area. The findings of this study provide a better overview of the Cisuralian fusulinid fauna found in this region. The presence of Crenulosepta confirms that the age of the uppermost part of the Kubang Pasu Formation is Artinskian, rather than extending into the Kungurian as previously recognized. The uppermost part of the Kubang Pasu Formation with its impoverished genus and species diversity is located just above the cold water brachiopods and diamictite beds. It indicates that during the Asselian (earliest Cisuralian), the northwestern Peninsular Malaysia was still part of the Gondwana continental shelf. During the late Early Permian, northwestern Peninsular Malaysia, as part of the eastern Cimmerian Continent, was located in a low latitude subtropical region of the paleo-equatorial tropical Tethyan Realm. The microfacies analysis of the Kubang Pasu Formation suggests a very high-energy, warm shallow marine environment of the inner ramp (e.g., sand shoals and banks).

Facies Analysis and Paleoenvironmental Reconstruction of Ghar Formation in Al-Muthanna Governorate, Southern Iraq

The Oligocene-Miocene succession in Al-Muthanna Governorate of southern Iraq shows significant mixed siliciclastic-carbonate formation. Fourteen samples are collected from two wells and four outcrops in Al-Muthanna area for studying the facies and paleoenvironments of the Ghar Formation. It is mainly composed of sandstone, calcareous sandstone, and carbonate rocks. Six facies associations are identified in the mixed siliciclastic-carbonate deposit: the carbonate type, including sabkha, lagoon, intertidal-subtidal, and lacustrine; the mixed type, including shoreface; and the siliciclastic type, including distributary channels. The major minerals in this formation are quartz, calcite, and dolomite, whereas feldspar and gypsum are the minor minerals. Clay minerals such as Palygorskite and Montmorillonite were also identified. The carbonate rocks of the Ghar Formation reflected deposition in the evaporitic platform (Sabkha), shallow restricted (lagoon), tidal and lacustrine environments. Ghar formation is considered transitional in conditions between a very restricted shallow marine and near-shore environment, whereas the clastic facies in Ghar Formation indicated deposition in the delta front channel.

Lithofacies, Facies Association, and Depositional Environment of 34-1, 33-6, and 33-4 Sandstone, Wida Field, Gita Member, Talang Akar Formation, Asri Basin, Offshore Southeast Sumatra

Three Gita Member reservoirs 34-1, 33-6, and 33-4 produce from solution gas drive with rapid pressure decline and low recovery factor. After successful oil production enhancements through waterflooding injections prompt the need for a reservoir model in further field development. Before such models were built reservoir characterization was carried out to determine facies and depositional environment for facies modeling. The study integrated core, wireline log, petrophysical logs, seismic attribute, petrography, etc. Next, well correlation was carried out to distribute stratigraphic markers. Finally, seismic attribute and well correlation were integrated to construct pie chart and depositional environment map. External geometry from seismic attribute revealed distributary channel with point bars which act as reservoir and consist of medium-fine grained planar tabular cross bedding sandstone, mud drapes sandstone, and ripple-wavy lamination sandstone. The wireline log showed fining-upward pattern and core displayed abundant channel rip up clasts, sharp or erosional contact with underlying lithology. Frequent mud drapes found within channel sandstone indicate tidal influence in proximity to marine environment probably in lower delta plain. Channels are trending west-east (34-1) and north-south (33-6 and 33-4). Other facies associations are shallow marine, swamp, interdistributary bay, and tidally influenced interdistributary bay. Shallow marine FA consists of skeletal limestone (Lm), calcareous mudstone, and calcareous sandstone (Sc). Rootlet mudstone (Fb) and interlamination of carbonaceous mudstone with very fine-grain sandstone (Fl) formed interdistributary bay FA. Swamp FA consists of coal and coaly mudstone. Tidally influenced interdistributary bay FA consists of carbonaceous laminated mudstone high in carbon (Flb), intensely bioturbated carbonaceous mudstone (Flb), very finely laminated mudstone-very fine grain sandstone (Fl) and black fissile shale (Fm).

Experimental study on the comparison of mechanical properties of different types of glutenite in the Ma'nan area

This study delves into the mechanical properties of various rock types found in glutenite reservoirs in the Ma'nan area of the Xinjiang oilfield. It bridges a knowledge gap by exploring the mechanical deformation and failure patterns among different glutenite types. Employing porosity-permeability tests, ultrasonic wave velocity measurements, and triaxial compression tests, this research scrutinizes physical parameters, mechanical properties, deformation, and failure modes of dolomitic sandstone, calcareous coarse sandstone, calcareous fine siltstone, and glutenite. Results highlight a porosity increase from dolomitic sandstone to glutenite, with calcareous coarse sandstone having the lowest permeability and glutenite the highest. Shear wave velocity is greater in dolomitic sandstone and calcareous coarse sandstone compared to calcareous fine siltstone, while longitudinal wave velocity is higher in dolomitic sandstone than in glutenite. Deformation behavior varies: dolomitic sandstone is primarily elastic, and calcareous sandstone and glutenite show elastoplastic characteristics. Dolomitic sandstone boasts the highest compressive strength, elastic modulus, and Poisson's ratio. Calcareous fine siltstone's compressive strength and elastic modulus fall below dolomitic sandstone, while the Poisson's ratio of calcareous coarse sandstone is three-quarters that of dolomitic sandstone. Main failure modes observed are shear failure in dolomitic sandstone, calcareous coarse sandstone, and glutenite, and axial splitting failure in calcareous fine siltstone. Microscopic analyses, including environmental scanning electron microscopy and mineral composition, shed light on the mechanical differences among the rocks. In sum, this research yields crucial insights into the mechanical traits of glutenite reservoir rocks, essential for optimizing hydraulic fracturing strategies in such reservoirs.

Shallow-water whale-fall communities: Evidence from the middle–late Eocene basilosaurid whale bones, Wadi El-Hitan, Fayum, Egypt

The present study examines the basilosaurid whale bone specimens collected from the Sandouk El-Borneta section, Wadi El-Hitan (Valley of Whales), Fayum, Egypt. These specimens are embedded in highly fossiliferous calcareous sandstones of the middle Eocene Gehannam and the upper Eocene Birket Qarun formations. These whale bones display some post-mortem alterations, representing good signs of at least three distinct stages in what is called the whale fall. The co-occurrence of shark, ray, and crocodile fossil specimens with the examined whale bones may indicate the first mobile-scavenger stage. Borings of the siboglinid polychaete genus Osedax represent the most common worm type that deeply bioeroded the whale bones, contributing to their rapid degradation, and representing the enrichment-opportunist stage. These fossil traces of the bone-eating worm Osedax represent the first record in the Eocene Epoch regionally and inter-regionally, filling the gap between the Late Cretaceous and the Oligocene occurrences. Subsequently, the studied whale bones served as hard substrates for some calcareous tube-dwelling encrusting polychaetes, balanoid barnacles, sheet‐like cheilostome bryozoans, and scleractinian corals. Furthermore, a bioerosion structure produced by polychaete annelids was also observed. The presence of these sclerobionts assemblage confirms the well-developed final reef stage with prolonged exposure and colonisation of these whale bones prior to final burial. Based on the recorded post-mortem alterations, together with other sedimentological and palaeontological data, the studied whale bones were deposited in a shallow open marine bay to sheltered gulf environments, which were characterised by low depositional energy, low to moderate rate of sedimentation, and high surface water productivity.

Soil development trajectories, chemical weathering and pedogenic mineral (trans)formation on glauconitic calcarenites in a Mediterranean area

Glauconite forms in shallow marine basins under oxic to suboxic conditions. It is an Fe-rich sheet silicate often found in calcareous sandstones. How soils evolve on glauconitic sandstones (calcarenite) is poorly addressed: therefore, we investigated the evolutional trajectories. These soils should be enriched in Fe, depleted in K and contain kaolinite and smectite resulting from weathering. We investigated 11 soil profiles on glauconitic calcarenite in a Mediterranean area. The elemental contents, fractions of Fe and Al, soil mineralogy, magnetic susceptibility and stable isotopic composition (C, O) of the bulk soil and carbonates were analysed to explore pedogenesis.The carbonates reflect a former marine basin having onshore organic matter resulting from freshwater input. With soil formation, the primary carbonates were replaced by pedogenic carbonates having a lower δ13C and δ18O signal. Several sites were influenced by human activity since ancient times, reflected by the magnetic susceptibility. The shallow soils had a low weathering degree (CIA of 55 to 70). The better developed Vertisols exhibited a CIA value of up to 85. All soils contained smectite and quartz and, depending on the weathering degree, calcite. Kaolinite formation was connected to high Ca, K, Mg and Na losses. The high oxalate- and dithionite-extractable Fe contents are explained by glauconite weathering. Kaolinite is inherited from the parent material but also actively forms in the soils probably through precipitation from soil water. Due to the presence of smectite and oxyhydroxides the soils sequester a high amount of soil organic carbon (up to 30 kg/m2). Topography exerts a distinct influence on weathering and soil formation. Deepest soils and an advanced weathering stage were measured on footslope sites and shallow soils having a low weathering degree on crest/shoulder sites. Soils on glauconitic calcarenite represent a unique weathering environment that should be investigated even more at the micro-scale.

PENNSYLVANIAN CONODONTS AND MICROFACIES FROM NORTHEASTERN MEXICO (TAMATÁN GROUP, CIUDAD VICTORIA BLOCK)

The biostratigraphic analysis of the Paleozoic sedimentary successions in Mexico is crucial for understanding their age, depositional setting, and paleogeographic implications. This study examined conodonts and microfacies of calcareous strata within the Del Monte Formation of the Tamatán Group in northeastern Mexico. Field observations have led to the identification of three units within the Del Monte Formation: Unit 1, characterized by calcareous sandstone, bioclastic limestone, shale, occasional conglomerate, and dolomitized beds; Unit 2, consisting of conglomerate and/or breccia associated with debris flows; and Unit 3 including turbiditic sandstone and shale. Conodonts were only recognized in Unit 1, with such genera as Idiognathoides, Neognathodus, Idiognathodus and less frequently, Streptognathodus, Adetognathus, and Diplognathodus. The faunal associations include Idiognathoides cf. Id. corrugatus Harris & Hollingsworth, 1933, Idiognathoides sulcatus sulcatus Higgins & Bouckaert, 1968, Idiognathoides convexus (Ellison & Graves, 1941), Idiognathoides asiaticus Nigmadganov & Nemyrovskaya, 1992, Neognathodus cf. N. atokaensis Grayson, 1984, Neognathodus aff. bothrops Merrill, 1972, Neognathodus nataliae Alekseev & Gerelzezeg, 2001 (in Alekseev & Goreva 2001), Streptognathodus parvus Dunn, 1966, Idiognathodus incurvus Dunn, 1966, and Idiognathodus aff. delicatus Gunnell, 1931, suggesting Morrowan and Atokan (Pennsylvanian) ages for the dolomitic limestone and grainstone beds. Five types of microfacies (MF) and several marine facies zone (FZ) have been detected: MF1-bioclastic grainstone and MF2-wackestone deposited at the platform margin (FZ 6 and FZ 7), MF3-dolomitized wackestone representing an inner restricted platform (FZ 8), MF4-mudstone from a deeper water zone (FZ 4), and MF5-siliciclastic beds with bioclasts indicating a high-energy barrier associated with a platform margin (FZ 6). The findings confirm a shallow to deep platform and imply a connection among Mexican peri-Gondwanan basins, including the Tamatán Basin, indicating similarities in sedimentary facies and/or depositional environments linked to the Rheic Ocean during the Early to Middle Pennsylvanian.

Engineering Geological Study of Road Tunnel Along Siddhartha Highway Between Butwal and Dobhan Siwaliks Group, West-central Nepal

The Siddhartha Highway is a critical economic artery in Nepal, providing a vital trade link with China and India. However, this roadway has been beset by the frequent occurrence of rock falls and dry landslides, which can cause severe damage and disruption. The main causes of these issues are differential weathering patterns of the rocks, activation of the Main Frontal Thrust (MFT), and a young mountain chain with fragile geology. Because of road instability, the road tunnel has been proposed to prevent damage. The proposed tunnel road passes between the chainage of 29+000 and 30+370 in the rocks of the Lower and Middle Siwaliks. The Lower Siwaliks are composed of thick to thin-bedded shale, mudstone and calcareous sandstone whereas the Middle Siwaliks are represented by presence of friable sandstone, shale and mudstone. The rock mass of this section varies from poor rock to extremely poor rock with RMR values ranging from 29 to 45 and Q values ranging from 0.19 to 1.11. The support system for each class is derived according to RMR and Q-value. The kinematic analysis reveals the potential of wedge failure at the southern portal of the road tunnel, whereas the northern portal has shown a low potential for failure.

Hydrogeology of the small island: a case study of Pisang island, West Coast Regency, Lampung province

Pisang Island has an area of 1.5 km2. The issue on small islands pertains to the quality and quantity of water. This is related to an increasing population and growing water demand. This research aims to address the sustainability of water resources. Therefore, a hydrogeological concept is required to assess and predict potential water resources to maintain the quality and quantity of water. The methodology used in this research includes geological mapping, measurement of rock resistivity, hydrometeorological analysis, and water quality testing. The research indicates that the lithologies of Pisang Island calcareous gravelly sand, calcareous sandstone, and porous limestone. The aquifer system on Pisang Island is unconfined. The aquifer was spread throughout the island with varying thicknesses. The lithology of calcareous gravelly sand is found in the island’s northern part, with a thickness ranging from 15 to 90 m. Calcareous sandstone is located in fold slopes of 3 to 5 m thickness. Porous limestone is distributed across the island, with a 30–170 m thickness. Pisang Island has an annual rainfall of 3,101.93 mm/year, evapotranspiration of 2,017.91 mm/year, and infiltration of 511.23 mm/year. The groundwater flow pattern moves from high elevations in hilly areas to low elevations in coastal areas.

From the Mountain and the Sea: Provenance of the Stones of the Prehistoric La Pastora Tholos (Valencina de la Concepción, Seville, Spain)

La Pastora tholos is the most complete and characteristic megalithic monument of the Valencina de la Concepción-Castilleja de Guzmán mega-site. This monument was built using three types of rock, each with different functions and coming from three different places: Paleozoic quartzarenite, granite, and Tertiary calcareous sandstone. A detailed petrological study of the rocks of the tholos and outcrops of similar rocks in the surroundings has been carried out, locating the possible source areas in areas at least 30 km to the N of the monument for the quartzarenite, 15 km for the granite, and 15 km to the S for the sandstone. Therefore, the community that built the monument has a high knowledge of the nature by, which allows them to locate these resources, and a sufficient social organization to exploit them and move them to the mega-site. In this sense, the layout of the outcrops suggests the possible use of boats or rafts to facilitate their displacement, or at least part of their movement.

Application of ERT, IP and VLF-EM Methods to Investigate Landslide-Prone Structures at Archaeological Sites in Lamreh, Aceh Besar, Indonesia

Since the 21st century, Lamreh, Aceh Besar Regency, Indonesia played an important role during the maritime silk route at the gate of the Malacca strait. This article investigates the subsurface structure of landslide-prone areas in cultural heritage based on 2D resistivity, chargeability and current density models of ERT, IP and VLF-EM methods, respectively. Field data measurements were carried out on 2 crossing profiles along the cliff suspected of experiencing landslides. The length of each profile is 220 with 4 m distance between stations. The 2D models reveal that the subsurface geological structure of Lamreh is composed of a mixed layer of clastic sediment and volcanic material at the top, followed by a layer of calcareous sandstone, and volcanic breccia at the bottom. The 3 layers are most easily distinguished in the resistivity model. The topmost layer is permeable but dry, i.e., characterized by a more resistive layer in the models. While the second layer is characterized by an intermediate conductivity and the bottom layer is highly conductive. The conductivity in these 2 layers is influenced by the degree of water content within the rocks. The chargeability models derived from IP data can distinguish between the dry layer on the surface and the saturated layer below. Meanwhile, the current density models obtained from VLF-EM data have proven the presence of fractures and faults along the profiles due to weathering as also seen in the resistivity models. HIGHLIGHTS Investigation of subsurface structure in landslide-prone area of Lamreh, Aceh Besar Regency, Indonesia, a cultural heritage site with historical significance in the maritime silk route. Utilization of 2D resistivity, chargeability and current density models (ERT, IP and VLF-EM) to analyze the subsurface structure. Field data measurements conducted on 2 crossing profiles along the suspected landslide cliff, with a profile length of 220 and 4 m station distance. Subsurface geological structure of Lamreh identified as a mixed layer of clastic sediment and volcanic material at the top, followed by calcareous sandstone and volcanic breccia at the bottom. Resistivity models most effectively distinguish the 3 layers, highlighting permeable but dry top layer, intermediate conductivity in the second layer, and high conductivity in the bottom layer influenced by water content. Chargeability and current density models confirm surface dryness and presence of fractures and faults due to weathering GRAPHICAL ABSTRACT

ВИЗНАЧЕННЯ ЕФЕКТИВНОЇ ПОРИСТОСТІ ПОРІД-КОЛЕКТОРІВ ЗА ДАНИМИ СТРУКТУРИ ЇХ ПУСТОТНОГО ПРОСТОРУ У ВІЗЕЙСЬКИХ І ТУРНЕЙСЬКИХ ВІДКЛАДАХ БЕРЕЗІВСЬКОГО РОДОВИЩА

Background. Currently, it is quite important to track the patterns of the internal structure of reservoirs with their physical properties. The analysis of well-logging data in the well 203 of the Berezivske field of the Dnipro-Donetsk depression is necessary to assess the prospectivity of complexly structured reservoirs. Methods. The methodology for studying the void space structure in complexly structured reservoirs involved several stages: interpretation of well logging data; determination of parameters for the initial mathematical model of the reservoir; inversion of data from acoustic surveys into a curve of the distribution of different void formats; evaluation of reservoir rock types with determination of their effective porosity. Results. Based on the data of compressional and shear wave velocities, as well as density, three distinct rock groups were identified: compacted sandstone, calcareous sandstone and limestone. The initial approximation was obtained for each rock sample, including the set of void formats and their concentration within the reservoir layers. Direct analysis of the resulting data by the authors revealed that the most optimal void formats for the investigated intervals are: for intergranular voids – 0.07 to 0.9; for transitional voids and microcracks – 0.05 to 0.077; for microcracks – 0.007 to 0.0019; for caverns – 4 to 8. Based on the research results, it has been established that granular-cavernous porosity (39,2 %) and fracturedcavernous-granular porosity (29,5 %) are prevailing types of reservoirs. Conclusions. The calculated values of the void formats were used for these formations to quantitatively assess effective porosity based on the obtained data and specific electrical resistivity values at different depths of investigation. The resulting approximation of α = 0.6996 was selected, which reduced the error in calculating the effective porosity of reservoir rocks. The obtained results have demonstrated that the proposed methodologies are essential for understanding and quantitatively assessing the void space structure and filtration-capacitive properties of reservoir rocks, particularly when we are facing with a limited well logging data and restrictive core sampling.

Деякі пізньокрейдові аглютиновані види форамініфер Північної окраїни Донбасу

The article describes four species of agglutinated foraminifers belonging to three genera (Verneuilina, Orbignyna, and Spiroplectammina) three superfamilies (Verneuilinoidea, Ataxophragmoidea, and Spiroplectamminoidea) and two orders (Ataxophragmiida and Ammodiscida, suborder Textulariina). Benthic species of foraminifers play an important role in the stratigraphic subdivision of the Upper Cretaceous deposits of the Northern outskirts of Donbas and correlation with adjacent territories, as they make up the most part of the assemblage in the samples. For this region, the foraminifera species Verneuilina muensteri Reuss, 1854, Orbignyna variabilis (d’Orbigny, 1840), Orbignyna pinguis Woloschyna, 1961, and Spiroplectammina baudouiniana (d’Orbigny, 1840) were monographically described for the first time. For each species of foraminifers, a detailed description of shell morphology is given. According to the biozonal scale of the Upper Cretaceous deposits of the East European Platform, Verneuilina muensteri is one of the characteristic species of the Upper Turonian Gavelinella moniliformis s. l. foraminifer zone, the species Orbignyna variabilis is typical for the Upper Santonian Gavelinella stelligera zone, and the species Orbignyna pinguis is characteristic of the Upper Campanian Globorotalites emdyensis zone. The species Spiroplectammina baudouiniana is also described. The stratigraphic and lateral distribution of each species of agglutinated foraminifers is indicated, and the deposits and sections of the Northern outskirts of Donbas in which they occurred are indicated. A schematic map of the region is presented, showing the studied sections in which shells of these species were found. These species are found in the rocks of the Shyroka, Yelanchyk, Kryva Luka, Sydorove, Konoplyanivka, and Kamianyi Brid formations of the Northern outskirts of Donbas, which are represented by chalk, marls, and calcareous sandstones. The work presents images of foraminifer species taken with a scanning electron microscope JSM-6490LV (JEOL Ltd., Japan). The article deepens our knowledge of some agglutinated foraminifers from the Upper Cretaceous deposits of the Northern outskirts of Donbas, which are characteristic species of the zone, contributing to further solving the issues of stratigraphy and correlation of these deposits.

Facies and trace fossils of the Upper Cretaceous Sillakudi Formation (Cauvery Basin, S. India) and their palaeoenvironmental significance

The Sillakudi Formation is a sandstone-dominated succession bounded by unconformities. It represents the oldest unit of the Ariyalur Group deposited during the Campanian under fully established passive margin depositional conditions. The present study is an attempt to interpret the depositional palaeoenvironment of Sillakudi Formation based on its trace fossil content, supported by sedimentological evidences. Detailed sedimentological and ichnological observations were undertaken in multiple traverses and spot locations across the Sillakudi Formation. The Sillakudi Formation is subdivided into four facies associations, each represented by a distinct ichnology and environment of deposition. Unit 1 comprises conglomerates grading upwards into pebbly sandstones almost devoid of trace fossils except a few Planolites isp. indicating a high-energy foreshore-to-shoreface environment. Unit 2 consists of glauconitic sandstones with Ophiomorpha nodosa, O. annulata, Thalassinoides isp. and Skolithos linearis, belonging to the Skolithos ichnofacies indicating deposition in shoreface to offshore transition environments. Unit 3 comprises pebbly to very coarse-grained massive sandstones, characterised by an almost monospecific Skolithos ichnofacies indicating rapid colonisation of beds in a delta-front associated debris flows and calcareous sandstones alternating with claystones containing a diverse Cruziana ichnofacies with an ichnoassemblage comprising of Trichichnus isp., Scolicia prisca var. laminites, S. ?prisca, S. vertebralis, Palaeophycus tubularis, Planolites beverleyensis, P. montanus, Taenidium isp., Thalassinoides suevicus, Ophiomorpha isp., Chondrites isp. and Phycodes isp., pointing towards deposition in calmer, possibly dysoxic outer shelf prodeltaic environments. Unit 4 has pebbly to gritty cross-bedded sandstones exhibiting the development of networks of Thalassinoides isp. and Ophiomorpha isp., indicating shallow sub-tidal to intertidal conditions of deposition. The overall succession is interpreted to show initial deepening followed by shallowing.

Gastrochaenolites as Palaeoenvironmental Information Traps: The Case of the Tholos of La Pastora (Valencina de la Concepción, SW Spain)

ABSTRACT In the Mio-Pliocene calcareous sandstone slabs used as capstones at La Pastora tholos in the Copper Age megasite of Valencina de la Concepción-Castilleja de Guzmán (SW Spain), marine bioerosion structures produced in the 3rd millennium BCE were recognised. In this work, we focus on the perforations made by the lithophage bivalve Petricola lithophaga, called Gastrochaenolites, specifically on its functionality as a ‘trap’ of sediment of the environment where they were produced and of which there are no observable outcrops. The microfaunal content consisting of planktonic and benthic foraminifera as well as ostracods was studied. It was possible to infer the palaeoenvironmental conditions of the place where the slabs were quarried, c. 4700–4600 years ago, which correspond to a wide marine bay. The presence of benthic foraminifera like Astrononium stelligerum, Elphidum crispum, Ammonia beccarii and ostracods like Loxoconcha elliptica and Cytherois fischeri implies that the sector of the bay had a water temperature of no more than 20°C, a bathymetry between 0 and 25 m of depth. Also, episodes of fluvial influence caused a variation in water salinity between 30 and 35‰, attested by the presence of euryhaline species of ostracods from low energy environments and clay substrates, thus confirming estuarine conditions.

Rutile to tourmaline index – a tool for the recognition of the hydrodynamics of the depositional environment; a case study from the Campanian Szozdy Delta System, SE Poland

The newly discovered mid-Campanian Szozdy Delta System (Roztocze Hills, SE Poland) located in the southern part of the Polish Cretaceous Basin, at the northern edge of the Łysogóry-Dobrogea Land, has revealed interesting features concerning the relationship between the abundance of rutile and tourmaline. A distinct inverse relationship between rutile and tourmaline can be readily recognised in the succeeding units of the tripartite cyclothems (calcareous mudstone, calcareous sandstone, and calcareous gaize) representing the submarine part of the Szozdy Delta System. In the Szozdy section, both minerals are of similar shape (highly rounded), durability, and size; they are, however, characterised by markedly different densities. Therefore, it might be expected that these two mineral phases will be strongly dependent, both vertically and spatially, on the local energy of the sedimentary environment hydrodynamic power that existed during the deposition of the succeeding units of the cyclothems. The lighter tourmaline was likely transported further to the more quiescent prodelta environment, rendering the prodelta facies overrepresented in this mineral, whereas the heavier rutile was deposited closer to the river discharge. Such relative change in the abundance of these two mineral phases, emphasised by a standardised Z-score statistics, is referred here to as rutile to tourmaline index (RuTidx). Accordingly, as the RuTidx increases, the hydrodynamic power in the sedimentary environment increases as well. Since these two mineral phases are comparatively immune to alteration during the sedimentary cycle, the RuTidx is considered here to be an independent tool in recognising the hydrodynamics of the depositional environments of any age.

Jabal Al-Qarah, Saudi Arabia—from a Local Tourist Spot and Cultural World Heritage to a Geoheritage Site of Possible Global Relevance

Jabal Al-Qarah in the eastern part of Saudi Arabia is a flat-topped residual hill (mesa) built of calcareous sandstones, mudstones, and marls of Miocene age. It is located within the World Heritage property of Al-Ahsa Oasis, but geoheritage values were not considered in the nomination and remained overlooked. The locality is famous for its systems of maze caves developed along deep fractures by mainly mechanical erosion and wall/roof collapses. They illustrate the origin of non-karstic caves through the action of underground flows, redirected from the surface via sinkholes and open cracks. Hillsides of Jabal Al-Qarah show evidence of various types of mass movements, including spectacular collapses of harder overlying strata after denudation of weaker strata beneath caused loss of vertical support. Thus, the mesa may become a key locality to understand slope development in layered successions and the role of subsurface flows in the global context. The site also has considerable potential to develop geotourism, as an added value to the already recognized cultural assets of the oasis and scenic qualities.