Sequence Of Carbonate Rocks Research Articles

New data on the geological structure and zonality of the Vorontsovka gold field in the Northern Urals

Spatial distribution of gold, copper, and iron ore deposits in the Northern Urals with the largest Turya-Auerbakh ore region is controlled by north-west trending linear zones of a probably fault nature. The influence has been demonstrated of regional factors (including the tectonic, magmatic, and geochemical ones) favoring formation of the large Au-As-Sb-Hg-Tl Vorontsovka deposit located within a volcanogenicsedimentary, substantially carbonate rock sequence. Closely spaced swarms of Devonian pre-ore and Carboniferous post-ore mafic dykes have been identified within the deposit. The primary geochemical halos of the Vorontsovka deposit have a multielement composition and, coupled with the ores, form a thick ore-halo zone confined to the gentle tectonic contact of sandstone-siltstone and limestone units. The main halo-forming elements are zonally distributed in the section. The footwall side of the gold deposit (rear zone) is dominated by Zn, Cd, Cu, Pb, Ag, and Bi; the axial zone, by Sb, Hg, Tl, and As; and the hanging side (frontal zone), by
 As, Zn, Hg, Pb, Ag, (Cu). In the east (closer to the Auerbakh granitoid massif), Ag, Zn, Pb, Mn, Y, Mo, and W relatively accumulate, while in the west (most remotely from the intrusive), Sb, Ba, As, Hg, Co, Ni, and Sn dominate. The 40Ar/39Ar age of ~391.1 million years, obtained for hydromica of the gold-arsenic ores, corresponds to the period of emplacement of granodiorite of the final Auerbakh massif intrusive phase. The conclusion is made on the crucial magmatic contribution to the formation of gold ores of the deposit.

Lithofacies, geochemistry, and sequences of basalt and carbonate rocks of a Middle Permian composite seamount (central Yarlung Zangbo Suture Zone, Tibet): Implications to the incipient opening of the Neo-Tethys Ocean

Lithofacies, geochemistry, and sequences of basalt and carbonate rocks of a Middle Permian composite seamount (central Yarlung Zangbo Suture Zone, Tibet): Implications to the incipient opening of the Neo-Tethys Ocean

Transportation of sediments by floating processes from southern Europe to the coastal regions of eastern Libya: Pumice rock fragments from at Tariyah and Qasr Libya coasts1

Abstract
 Fragments of pumice of various sizes and roundness were found mixed with recent coastal sediments of calcareous sand, calcareous granules, and shells in At Tariyah coast southwest of Benghazi, and in the coastal area of Qasr-Libya, Al Jabal Al Akhdar, northeastern Libya. The source area for the pumice fragments appears to be the active volcanic regions of eastern and southern Sicily; Etna volcano and submarine volcano known as the CampiFlegrei del Mar di Sicilia respectively. 
 The pumice must have traveled a distance of at least 1000km across the Mediterranean Sea as a floating load. 
 The recent coastal sediments of the Al Jabal Al Akhdar area are derived mainly from two different sources; a southern proximal source consisting of a well-exposed sequence of Tertiary carbonate rocks that produced well-sorted sand-size fragments and a northern distal source that produced cobble-size fragments of pumice. 
 The mechanism of transporting sediments by floating as a floating load, from one sedimentary basin to another is completely different from the other well-known and documented methods of bedload and suspended load. Floating fragments can be transported for long distances and finally deposited without appreciable changes in size, roundness, shape, or sorting. Pumice deposited on the eastern coast of Libya indicates that long-distance transport produces minimal or negligible changes in the textural parameters of floating load components.

Petrogenesis and tectonomagmatic updates on the origin of the igneous rocks in the lower Benue rift, southeastern Nigeria

This work presents updates on the tectonomagmatic origin of igneous rocks in the lower Benue rift based on recent available geochemical data. The igneous rocks occur as volcanic and plutonic rock series. The rock types are basalts and basaltic sills, pyroclastic rocks (tuffs and lapilli tuff), trachytes, trachybasalts, gabbros (stocks), dolerite sills, and dioritic rocks (stocks). The rocks were emplaced within folded sedimentary sequence of shales, subordinate sandstones, and siltstone and carbonate rocks of Asu-River and Eze-Aku Group. Most of the rocks are moderately to highly altered, with the pyroclastic rocks showing higher effects of alteration (LOI 3 to 22 %). Incompatible and immobile elements and less altered rocks with LOI < 3% show that the rocks were derived from mantle enriched source and possibly HIMU signatures. The high ratios of (La/Yb)N 4.40 to 31.55 in the basic rocks and 23.59 to 135.35 in the trachytic rocks show alkaline affinity with sparse tholeiites and garnets in the source region. The rocks were formed by plume uprising in a within-plate setting of intra-continental rift system similar to the South Atlantic Ocean rocks and East African rift. The magnesium number (Mg#) and differences of the spidergrams and rare earth patterns indicate that the rocks are cogenetic, and source is heterogeneous. The depletion of K, P, Th, and Rb and formation of calcites and sericites in the rocks show mobilization probably by interaction with calcareous host rocks in prevailing conditions.

A combined multivariate approach analyzing geochemical data for knowledge discovery: The Vazante – Paracatu Zinc District, Minas Gerais, Brazil

The Vazante Group comprises a Proterozoic sequence of carbonate and siliciclastic rocks located in Minas Gerais, Brazil. It is the host of the Vazante-Paracatu Zinc District, including world-class hypogene zinc silicate deposits, in the southern part, and several Pb – Zn sulfide deposits in the northern part, all hosted in dolomitic rocks. A recent study revealed the occurrence of base metal sulfide mineralization that formed prior to the Brasiliano orogenic event in the siliciclastic rocks (Serra do Garrote Formation) that underlie these dolomite-hosted silicates and sulfide deposits. These siliciclastic rocks were considered as potential sources of elements for the hydrothermal fluids that formed the dolomite-hosted deposits, however there was little evidence of depletion of the source rocks during the orogenic event. In this paper, Random Forest is used in unsupervised mode along with t-distributed Stochastic Neighbor Embedding (t-SNE) and principal component analysis (PCA) over a lithogeochemical dataset of samples of the Serra do Garrote siliciclastic rocks collected throughout the basin to provide insights about processes related to the mineralizing system at the Vazante-Paracatu District.Multivariate analysis reveals that the Serra do Garrote Formation geochemical signature typical of pre-orogenic mineralization. This is characterized by PC1+ with association of Zn, Cd, Cu, Hg, In, V ± Sb, Se, Mo, Re, which corresponds to nearly 60% of the variance in the data. This suggest that these elements are related to a widespread and/or, long-living hydrothermal activity without an efficient mechanism to focus the metal-bearing fluids, causing basin-scale sub-economical Zn and related metal enrichment. Furthermore, PC2 and PC6 distinguish the zones with signatures interpreted to be related to depletion. PC2+ separates Cd-poor sphalerite, which is typical of the generation of sphalerite that occur in zones with textural evidence of remobilization. PC6+ with association of As, organic carbon and S, identified the zones where sphalerite was leached from the pyrite-rich layers. Areas with multivariate signatures of both pre-orogenic enrichment and syn-orogenic depletion in the source siliciclastic rocks include the Vazante-North Extension and Varginha zinc silicate deposits/occurrence, Ambrósia silicate zinc deposit and the Engenho Velho prospect. Preliminary exploration in this prospect revealed hydrothermal alteration typical of the zinc silicate deposits. This study is pioneering in applying these numerical models in possible source rocks to assist in identifying targets for exploration in basins.

History of studying the south of the West Siberian oil and gas province and the Trans-Urals

The article briefly covers the entire period of the Trans-Urals exploration, including Kurgan region. We report the main historical events of the process of prospecting for oil and gas. As a result of geological exploration, the industrial oil content of Cretaceous and Jurassic sediments have been identified, and powerful sequences of carbonate rocks of the pre-Jurassic age in Vagay-Ishim depression (the territory of Kurgan region) have been developed. It should be noted that the discovered sequences of carbonate rocks under favorable structural and tectonic conditions could be productive for oil and gas.

Geobiology of the Paleoproterozoic Belcher Group, Nunavut, Canada

The ~2.0-1.8 Ga (billion years old) Belcher Group on the Belcher Islands in Nunavut provide a unique opportunity for studying Paleoproterozoic geobiology. The Belcher Group includes a sequence of low metamorphic grade peritidal carbonate rocks that preserve putative microbiota, as first described by Hofmann and Jackson (1969). Microbial mats, including stromatolites, are abundant in the peritidal carbonate succession. Additionally, morphologies possibly related to blue-green algae were first described in granular iron formation rocks of the Belcher Group by Moore (1918). The Belcher Group microbiota are a group of simple organisms, believed to be prokaryotic in nature. Microbiota morphologies include ellipsoids, spheroids, and filamentous chains of cells interpreted by previous workers to represent blue-green algae and acritarchs. Some microstructures are questionably biogenic and might be abiotic. The most significant field studies on the Belcher Group occurred from the late 1950s to the early 1980s, which provides the geological context for this study. This project aims to build on the previous work of H. Hofmann and others in the ‘60s and bring these microbiota into a modern context, drawing on the analytical advancements of the last 50 years. The main goal of the project is to determine if there is evidence that the microbiota are perhaps eukaryotic organisms. The emergence of eukaryotes is arguably the most significant geobiological event in Earth history, with eukaryotic cells believed to have evolved around 1.6 Ga (Knoll et al. 2006; Javaux and Lepot 2018), but some contentious fossils interpreted to represent eukaryotes have been dated to as early as 2.2 Ga (Retallack et al. 2013). In North America, the oldest discovered eukaryotic remains are around 1.5 Ga (Adam et al. 2017). If eukaryotic fossils were to be discovered in the Belcher Group, this would make them the oldest occurrence in North America. To test the hypothesis, samples from the microbiota-containing units were collected on the Belcher Islands. Both light microscopy and a collection of modern analytical techniques will be used to obtain high resolution images and chemical signatures of the microbiota and their biosignatures. Preliminary data from petrography, Raman Spectroscopy, and X-ray Photoelectron Spectroscopy (XPS) will be presented. Both Raman spectroscopy and XPS have been used as characterization tools in other studies looking at microbiota and organic matter remains (Qu et al. 2018; Arnarson and Keil 2001). Raman collects molecular and structural data from the sample, while XPS collects elemental chemical data. Both techniques are therefore particularly useful for identifying and characterizing organic carbon, which is the base of organic matter.&#x0D;

Chapter 2 Structural development of the Arabian Intrashelf Basin region

Abstract This chapter summarizes the tectonic events that have affected the region of the Arabian Intrashelf Basin and the development of the intrashelf basin. Precambrian–Infracambrian fault systems provided a structural framework, which was later reactivated during the Late Paleozoic. Further development along the structural trends continued in the Triassic and Early Jurassic with the development of an Early Jurassic tectonically controlled intrashelf basin. The accommodation space was filled with Dhruma Formation carbonates by the early Bathonian, resulting in a broad and fairly flat platform. A crucial factor is how suppressed tectonism was during the Mid- and Late Jurassic. The intrashelf basin developed on the broad, tectonically stable Tethyan passive margin continental shelf 200--300 km distant from the Tethyan outer shelf edge. During the Mid- and Late Jurassic, this tectonic stability provided the foundation for a broad, stable Tethyan continental shelf region at least 1000 × 1200 km in area, far removed from siliciclastic sources, within which the huge Arabian Intrashelf Basin formed and the sequences of carbonate rocks and evaporites that created the Jurassic hydrocarbon system were deposited. Tectonism during the Mid- to Late Jurassic evolution of the Arabian Intrashelf Basin initially included only moderate subsidence. There was subtle uplift along some of the structural trends in the Late Jurassic and uplift and westwards structural tilt along the Tethys oceanic margin. Relatively stable tectonism continued after the Jurassic and was a major factor in the accumulation of the vast reserves of Jurassic sourced oil. Tectonic stability prevented major faulting and structural compartmentalization of the basin features, which provided large areas for hydrocarbon migration as the large and broad anticlines developed into the huge structural traps. The lack of major faulting limited the movement of burial fluids, preserving the early formed porosity and the regionally extensive seals. The present day structures primarily developed from the Late Cretaceous to Miocene as the Tethys Ocean closed.

A multi-instrumental geochemical approach to assess the environmental impact of CO2-rich gas emissions in a densely populated area: The case of Cava dei Selci (Latium, Italy)

The Colli Albani volcanic complex (Lazio, Italy) hosts areas characterized by anomalously high emissions of CO2-rich gases (e.g. Tivoli, Cava dei Selci, Tor Caldara, Solforata). The source of these gases is a regional aquifer within the Mesozoic carbonate rock sequences. These degassing zones release significant concentrations of H2S and other toxic gases (e.g. GEM: Gaseous Elemental Mercury, and Rn) and represent a serious hazard for local inhabitants, especially for those living at Cava dei Selci (near Rome, Italy), where the emitting areas are nested inside residential neighborhoods. In April 2016, a comprehensive geochemical survey was carried out in an abandoned stone quarry nearby the urban settlement aimed to: (i) investigate the gas composition from both punctual discharges and anomalously high diffuse soil degassing sites, and (ii) evaluate their environmental impact on the local air quality. The spatial distribution of the soil CO2 fluxes was mainly dependent on the local geostructural setting, whereas shallow secondary processes (e.g. oxidation and gas-water interaction) likely represent the main controlling factor on reactive and/or water-soluble gas species, such as CH4 and H2S. The total output of CO2 from the abandoned stone quarry accounted for 0.53% of total CO2 discharged from the whole Colli Albani volcanic district. The naturally emitted toxic gases (e.g. CO2, H2S, CH4, GEM) largely affect the air quality and pose a serious threat for the health of the local residents. A mobile multi-instrumental station able to continuously and simultaneously acquire CO2, H2S, SO2, CH4, GEM and CO was deployed to verify the concentrations of both the main deep-originated gas compounds and potential secondary gaseous contaminants (i.e. SO2) around and inside the urban settlement most exposed to the lethal gases. Hydrogen sulfide was found to be the most impacting gas, occasionally exceeding the 24-h air quality guideline for ambient air and causing odor annoyance at a distance up to more than 250 m downwind from the emitting area. In poorly ventilated basements, toxic gas accumulations up to hazardous levels were measured, producing anomalous outdoor air concentrations at the street level in front of the descending vehicular access to private garages and relatively far from the main emitting area. The geochemical survey, carried out via mobile station and soil gas measurements, resulted to be particularly efficient for evaluating the potential effects caused by gas emissions in inhabited areas. The multi-measurement approach adopted in the present study is of paramount importance for managing future urban development plans.

Sedimentological sequence and depositional evolutionary model of Lower Triassic carbonate rocks in the South Yellow Sea Basin

ABSTRACT Based on well logging and seismic data, combined with a comparative analysis of drilling data in the Lower Yangtze region, the sequence stratigraphic framework of the Qinglong Formation was established and divided into four third-order sequences. Each sequence is mainly composed of the transgress system tract (TST) and the high-stand system tract (HST). According to the lithology, logging curve and seismic reflection structure, the sedimentary filling characteristics and evolution law for the sequence are analyzed. The results show that each sequence is dominated by a half-cycle decline of sea level, and the rise-fall of sea level controls the distribution and evolution of sedimentary systems within the sequence. During the relative sea-level rise, sedimentation rates slow down and muddy sediments are developed. The characteristics of condensing intervals on the flooding surface are very obvious, and continental shelf and open platform deposition are mainly developed. During the relative decline of sea level, the thickness of sediments increased. The main developments were restricted platform and platform shoal environment, and locally developed evaporation platform environment.

Gastropods of the Gilmore City Formation (Lower Mississippian) of North-Central Iowa: Part 1, Geology and Systematics of Bellerophontoidea and Euomphaloidea

The Gilmore City Formation of north-central Iowa represents an upward-shoaling sequence of carbonate rocks ranging from normal marine conditions in the lower portion of the section to prograding oolite shoals at the top. At most exposures, the formation contains an abundant and diverse fauna that has been used in several attempts to correlate the Gilmore City with the Mississippian type section. Results of biostratigraphic correlation indicate that the Gilmore City Formation spans the Kinderhook-Osage boundary, occupying a position that, in the Mississippian type section, is represented by an unconformity. Gilmore City fossils actually have closer affinities with Cordilleran faunas than with those of the Midcontinent.The gastropods constitute one of the most abundant and diverse faunal elements of the Gilmore City Formation, consisting of more than 75 species representing about 50 genera and subgenera. This first part deals only with the Bellerophontoidea and Euomphaloidea. Described and illustrated species include the bellerophontoideans Bellerophon (Bellerophon) panneus White, 1862, Bellerophon (Bellerophon) meeki? Koninck, 1883, Waagenella spergenensis (Gordon and Yochelson, 1983), Waagenella sp. cf. Waagenella spergenensis (Gordon and Yochelson, 1983), Waagenella sp. indet., Retispira sp. cf. Retispira exilis (Koninck, 1883), and Euphemites rollinsi, new species; and the euomphaloideans Euomphalus springvalensis White, 1877a, Euomphalus luxus White, 1877b, Euomphalus ammon White and Whitfield, 1862, Straparollus obtectus, new species, and Serpulospira paradoxus (Winchell, 1864).

Carbon isotopes, stratigraphy, and environmental change: the Middle–Upper Cambrian Positive Excursion (SPICE) in Port au Port Group, western Newfoundland, Canada

In many basins, Upper Cambrian carbonate successions display intervals with a positive carbon isotope excursion (CIE) of up to +5‰. In North America, this marks the boundary between the Sauk II–III super-sequences. A Steptoean positive carbon isotope excursion (SPICE) locality previously identified in the Port au Port peninsula, western Newfoundland, has been revisited and an additional potential SPICE locality found. In both locations, a CIE is found to be associated with a prominent bioherm and sandstone layer within a sequence of carbonate rocks. At March Point columnar stromatolites occur, whereas at Felix Cove thrombolites can be seen. In the latter, the sandstone immediately overlies the thrombolites coincident with the CIE, whereas at March Point a dolomitized grainstone occurs above the stromatolites. The sandstone at this locality post-dates the CIE. Although lower than the SPICE in some localities, a positive CIE is present in both sections: March Point (+1.1‰) and Felix Cove (+1.8‰). Additionally, δ13Corgrises from −30.0‰ to −22.0‰ at March Point and from −27‰ to −24.0‰ at Felix Cove and, in accordance with previously published work, we suggest that this could be the SPICE. Comparison of the stratigraphy and petrography between the two localities suggest that both depositional and diagenetic factors could have influenced the nature of the interpreted SPICE in Newfoundland. It is also possible that the local carbon isotopic signature may have been influenced by a semi-restricted depositional and early diagenetic environment related to the paleogeographic configuration rather than the global marine excursion.

Geological constraints on cave development in the plateau-gorge karst of South China (Wulong, Chongqing)

The Houping Tiankeng cluster is a part of the South China Karst UNESCO World Natural Heritage Site. Within the distinctive Wulong plateau-gorge karst, >200km of cave passages have been documented to date. This paper focuses on detailed tectonic and morphological research on the Luo Shui Kong cave, enriched with U-series dating of speleothems and complemented by morphometric analysis of the San Wang Dong and Er Wang Dong caves. All of these caves exhibit three regional levels of cave development: 1) 1040–1020m a.s.l.; 2) 900–840m a.s.l.; and 3) 740–660m a.s.l. The Houping Tiankeng area is a carbonate rock sequence several hundred meters thick, overlain by the less soluble Lower Ordovician strata, limiting recharge points to faults exposing underlying easily soluble formations. This leads to the domination of concentrated, high-volume inflow and thus results in caves of large volume in the plateau-gorge karst. Shafts connecting the surface with cave passages located underneath formed along faults, changing the hydrogeological pattern through karst water capture and remodeling of existing conduits, albeit mainly by increasing their overall dimensions rather than by deepening them. The most favorable structures for cave-level development are two sets of joints conjugated with gently inclined bedding. Since these joints are characterized by a small vertical extent, downward development is limited. Hence, most of the passages are wide but not deep canyons and typical of a water-table cave pattern. Places where the fault plane is eroded from the surface and where, at the same time, an underneath cave chamber ceiling expands upwards are particularly predisposed to the formation of a tiankeng.

High temperature gas–solid reactions in calc–silicate Cu–Au skarn formation; Ertsberg, Papua Province, Indonesia

The 2.7–3 Ma Ertsberg East Skarn System (Indonesia), adjacent to the giant Grasberg Porphyry Copper deposit, is part of the world’s largest system of Cu–Au skarn deposits. Published fluid inclusion and stable isotope data show that it formed through the flux of magma-derived fluid through contact metamorphosed carbonate rock sequences at temperatures well above 600° C and pressures of less than 50 MPa. Under these conditions, the fluid has very low density and the properties of a gas. Combining a range of micro-analytical techniques, high-resolution QEMSCAN mineral mapping and computer-assisted X-ray micro-tomography, an array of coupled gas–solid reactions may be identified that controlled reactive mass transfer through the ~ 1 km3 hydrothermal skarn system. Vacancy-driven mineral chemisorption reactions are identified as a new type of reactive transport process for high-temperature skarn alteration. These gas–solid reactions are maintained by the interaction of unsatisfied bonds on mineral surfaces and dipolar gas-phase reactants such as SO2 and HCl that are continuously supplied through open fractures and intergranular diffusion. Principal reactions are (a) incongruent dissolution of almandine-grossular to andradite and anorthite (an alteration mineral not previously recognized at Ertsberg), and (b) sulfation of anorthite to anhydrite. These sulfation reactions also generate reduced sulfur with consequent co-deposition of metal sulfides. Diopside undergoes similar reactions with deposition of Fe-enriched pyroxene in crypto-veins and vein selvedges. The loss of calcium from contact metamorphic garnet to form vein anhydrite necessarily results in Fe-enrichment of wallrock, and does not require Fe-addition from a vein fluid as is commonly assumed.

Hydrogeological, Hydrogeochemical and Isotope Geochemical Faetures of Thermal Waters in Kuşadası, Turkey

In this study, the hydrogeological, hydrogeochemical and isotopic signatures of the thermal waters in Kuşadası and surroundings will be presented. In the study area, the basement rocks are impermeable Paleozoic mica schists of the Menderes Massif. The Mesozoic marbles are ascribed either to groundwater aquifers or to thermal waters reservoirs. These rocks are covered by the Kuşadası formation consisting of a sequence of claystones, conglomerates and carbonate rocks. This upper Kuşadası formation plays an important role as cap rocks. The existence of active faults and basic volcanic rocks of Pliocene age points to the existence of high heat flows and geothermal gradients. As a youngest geological formation, the alluvium is a very good aquifer. Nowadays, there is the risk of sea water intrusion into the local groundwaters due to the drop of groundwater table caused by groundwater overexploitation in the study area.

Geological Assessment of the Khor Kharfot Sediments, Western Dhofar Region, Sultanate of Oman

Khor Kharfot is part of a coastal estuarine wetland system located in the western part of the Dhofar Governorate preserving a pristine ecosystem supporting a distinct vegetation and animal habitat. A sand barrier along the khor (local term for wetlands) mouth controls the mixing of fresh and marine water in the enclosed lagoon. In order to understand the geological controls on the khor formation, a geological map of the khor barrier and inlet area is prepared. The khor is bounded by Cretaceous and Tertiary carbonate rock sequences which are cut by a number of faults. The khor mouth and barrier are comprised of late Holocene deposits divided into seven units including i) beach sand, ii) beach sand mixed with wadi gravels, iii) scree and coastal dunes, iv) lagoon, v) soil and boulders, vi) wadi gravels, and vii) talus. The khor developed as an open estuary which changed to a barrier dominated lagoon due to falling fresh water supplies as a consequence of dwindling Khareef rains. The lagoon water is brackish due to the mixing of fresh and marine water and supports a distinct flora and fauna.

Sustainable yield of the Colle Quartara carbonate aquifer in the Southern Lepini Mountains (Central Italy)

The present research is aimed to contribute to the groundwater resource sustainable management of a carbonate aquifer in a test area of the Lepini Mountains (Central Italy). This aquifer constitutes a major exploited groundwater body of central Apennines. At regional scale, the hydrogeological features of the Lepini hydrostructure are well known. The present study focuses on a portion of the Lepini Mountains where important tapping-works for drinking water supply are in activity (about 1.2 m3/s). New investigations were carried out including: meteo-climatic analysis, spring discharge and hydrometric time series processing, pumping test result interpretation. In addition, a detailed lithostratigraphical and structural survey of a portion of the Lepini hydrostructure at 1:10,000 scale was performed also examining the dense network of discontinuities affecting the carbonate aquifer. Extensional Plio-Pleistocene tectonic activity displaced the carbonate rock sequence under the Pontina Plain, where the carbonate aquifer is confined. The investigation results have allowed the reconstruction of the hydrogeological conceptual model of the studied portion of carbonate massif. Given the scale of the study and the results of the investigation, the carbonate aquifer can be treated as an equivalent porous medium, and the simplified numerical model of the aquifer was constructed with the code MODFLOW-2005. The numerical model, still now under continuous implementation, produced first results on the current withdrawal sustainability, allowing evaluation of possible alternative exploitation scenarios of the carbonate aquifer also considering the probably not significant flow exchanges with the Pontina Plain aquifer.

Lower Triassic anachronistic facies capping the Qinghai-Tibet Plateau seamount: Implications for the extension of extraordinary oceanic conditions deep into the interior Tethys Ocean

The Bayan Har area, situated in the northeast of the Qinghai-Tibetan Plateau, has long been regarded as a deep-water turbidite basin during Early Triassic. However, a sequence of Lower Triassic shallow-water carbonate rocks has been documented from the region, indicating the existence of isolated seamount carbonate platforms in the basin. The seamount carbonate platform sediments differ from synchronous deep basin flysch sediments, and consist of shallow-water oncoids, ooids and cortoids. Microfacies studies reveal that the oncoids have a thick cortex comprised of irregular, non-concentric and partially overlapping micritic laminae and contain abundant well-preserved foraminifera, indicating a relatively low-energy environment in subtidal settings. Ooids exhibit thinner and more regular concentric laminations, which are interpreted to have formed by frequent overgrowth while rolling in a relatively high-energy setting. Cortoids are predominantly composed of tiny fossil fragments and intraclasts with a micritic envelope, indicating a shallow-marine warm water environment located in the intertidal or supertidal zone. Ooids in the Bayan Har area differ from those found on stable platforms, in that they sometimes nucleated onto volcanic quartz grains, reflecting an unstable tectonic setting that was frequently affected by volcanic activity. Widespread ooids and other microbial carbonates formed in the Early Triassic have been regarded anachronistic facies that are indicative of harsh marine conditions. Most Lower Triassic anachronistic facies are distributed along the shallow margin of the Tethys Ocean and the western margin of Pangea; however, Bayan Har was located in the center of the Palaeo-Tethys. The discovery of oncoids and oolites capping a seamount in this area provides strong evidence that extraordinary marine conditions spread far into the interior of the Palaeo-Tethys Ocean.

Sedimentary facies, depositional environment, and sequence stratigraphy of Oligocene–Miocene shallow water carbonate from the Rig Mountain, Zagros basin (SW Iran)

This study investigates the depositional environment and sequence stratigraphy of the Asmari Formation that is exposed at the Rig anticline in the Izeh zone of the Zagros foreland basin with a thickness of 374 m as a sequence of thin, medium, thick, and massive carbonate rocks. The Asmari Formation is Oligocene–Early Miocene (Burdigalian) in age at the study area. In this area 12 microfacies are distinguished on the basis of their depositional texture, petrographic analysis, and fauna. These facies deposited in four major depositional environment including tidal flat, lagoon, shoal, and basin. The Asmari Formation represents sedimentation on a homoclinal carbonate ramp system. Based on the microfacies analysis, sequence stratigraphic studies, and distribution of planktonic and benthic foraminifera, six third-order sequences, three in Oligocene (Rupelian, Early Chattian, and Late Chattian in age) and three in Miocene (Early Aquitanian, Late Aquitanian, and Early Burdigalian in age), in Rig mountain section were identified.

Palaeomagnetism and rock magnetism of the Permian redbeds from the Velebit Mt. (Karst Dinarides, Croatia): dating of the early Alpine tectonics in the Western Dinarides by a secondary magnetization

The studied area of the Velebit Mt., a part of the Adria microplate, belonged to a NE margin of Gondwana during the Carboniferous and Permian. While the Carboniferous to the Early Permian was characterised by deposition of clastic rocks, younger sedimentation was dominated by a thick sequence of carbonate rocks. The Lower Permian deposits of the core part of the Velebit Mt. at Košna and Crne Grede localities were investigated using palaeomagnetic and rock magnetic measurements. The main remanence carriers were recognized as haematite with an increasing contribution of SP/SD magnetite in younger subsections. The AMS fabric with low anisotropy ratio (1–3%) is strongly oblate at Košna and weakly prolate at Crne Grede, reflecting differences in the contribution of magnetic phases.A significant remagnetization of the Permian rocks, as proved by results of a conglomerate test, probably caused by a combination of elevated temperatures and fluid migration, may be assigned to burial-related processes that affected the rocks before the final uplift of the Dinarides. Characteristic remanent magnetizations recorded in haematite are apparently similar to the Permian direction for Africa (shallow inclination with NNW declination), as expected for Velebit Mt. coordinates. Paradoxically, this orientation is observed in situ within the almost vertically dipping beds. We explain this relationship assuming a syn-folding Cretaceous remagnetization of the rocks at their subhorizontal position (ca. 30°S), in which a mean vector of the secondary remanence overlaps with the Cretaceous direction, expected for Africa at the Velebit Mt. geographical coordinates. Consequently, our results indirectly point to the Cretaceous time of incipient stages of the Dinaric tectonism, and suggest African geotectonic affinity of the Velebit rocks. No important vertical-axis rotation is implied by our results, in contrast to previously published data. The puzzling complete remagnetization carried by haematite at relatively low-to-moderate temperatures is also discussed.