Siliciclastic Rocks Research Articles

Provenance of the siliciclastic rocks in the Lower Yangtze region: Implications for Paleozoic tectonic switching of the northeastern South China Block

• Permian zircon U-Pb age spectra are different from those of Silurian and Devonian . • The Silurian-Devonian detritus was from the proximal igneous rocks. • Increased ca. 430 Ma zircons indicates the onset of foreland stage. • The Permian detritus was from the basement of the Cathaysia Block. • Foreland basin was replaced by intraplate basin in Late Paleozoic. Integrated analysis of zircon U-Pb dating, in-situ Lu-Hf and whole-rock geochemical data was performed on Silurian-Permian siliciclastic rocks from the Lower Yangtze region (LYZ), northeastern South China Block, to understand the tectono-sedimentary evolution during the Paleozoic. These rocks have a high chemical index of alteration (CIA = 71.3–91.8) and variable index of compositional variability (ICV = 0.2–3.5), indicating intensive weathering. The high Zr/Sc ratios (12.1–75.3) indicate that their sources contain recycled old sediments. The Silurian and Devonian samples contained abundant detrital zircons with ages of 1.0–0.8 Ga and 460–420 Ma. However, the Permian samples show bimodal age spectra with peaks at ∼ 1800 Ma and 280–260 Ma. Integrated with published geochronological data, the proportion of the 460–420 Ma zircons drastically increased from the Early to Mid-Silurian and decreased in the Early Carboniferous, indicating two tectonic transformations, respectively. Based on these variations and relative paleogeographic data, we suggest three evolution stages with different provenances for the LYZ: (1) from Cambrian to Ordovician, the LYZ region inherited the Cryogenian tectonic framework of South China Block, receiving detritus from East Gondwana. (2) from Silurian to Devonian widespread uplift in South China Block led to the development of an isolated foreland basin with independent sedimentary sources and (3) from Carboniferous to Permian, subduction of the Paleo-Pacific plate exposed the Paleoproterozoic basement of the Cathaysia Block, providing detritus for the LYZ intraplate basin.

Combined U-Pb ages and Lu-Hf systematics of detrital zircons from Early Cambrian Gondwanan siliciclastic rocks in S Turkey: Provenance and correlations with coeval successions in peri-Gondwanan terranes

Detrital U-Pb age peaks and εHf(t) and TDM(Hf) of peri-Gondwanan units of S Turkey indicate that they may have been derived from Neoproterozoic igneous suites in the Sinai Peninsula (Egypt), Israel (Elat) and Eastern Desert (Egypt) part of the Nubian Shield. Early Cambrian siliciclastics in the peri-Gondwanan units of S Turkey consist of quartzites in the Menderes Massif of the Tauride-Anatolide Platform (TAP), meta-quartz arenites in the different Alpine tectonic slivers of the TAP-margin and quartz-arenites in the Southeast Anatolian Autochthon Belt (SAAB). Geochemical data indicate that these sediments are likely to be derived from sedimentary recycling processes in oxic depositional basins within a continental back-arc tectonic setting. They were opened after the formation of the Avalonian-Cadomian magmatic arc. In the TAP, the youngest detrital zircon 238U/206Pb ages are range from 530.6 + 6.3/-12.0 Ma to 549.4 ± 10 Ma and from 551.9 + 7.9/-8.4 Ma to 545.8 ± 11 Ma in the SAAB verifying the Early Cambrian maximum depositional ages for the sampled siliciclastic successions. In the TAP, meta-quartz arenites, Neoproterozoic detrital zircons make up about 75% of the total grains, whereas they constitute about 88 % in the SAAB sedimentary rocks. Tonian zircons in the TAP (>40 %) and SAAB (<32 %) reveal key populations to determine their provenance and the paleotectonic positions of the respective terranes. The combination of U-Pb age and Lu-Hf systematics in the detrital zircons of the TAP and SAAB show that age groups at 535 to 562 Ma and 888 to 3370 Ma are mainly represented by the zircons derived from evolved sources with a limited juvenile component. The predominant zircon age groups between 577 and 854 Ma in the TAP and SAAB, on the other hand, were derived from juvenile to evolved sources. Non-parametric Kolmogorov-Smirnov tests suggest that Early Cambrian successions in the TAP (except Kocaosman-Isparta) may have been located in similar paleogeographic locations with coeval successions in the SAAB during the Early Cambrian. U-Pb geochronology and Lu-Hf systematics of the Early Cambrian successions in the TAP and SAAB indicate that the dominant detrital zircon age groups were mainly sourced and transported to continental back-arc fluvial to shallow marine sedimentary environments from igneous rocks of the Nubian Shield and the Saharan Metacraton by a combination of the glaciers, eolian events and multiple-stage erosional and sedimentary recycling processes during the Early Cambrian (ca 520 Ma). The provenance of the Early Cambrian successions in the TAP and SAAB correlate with the provenance areas of the coeval siliciclastic sequences in Israel and Jordan (Arabian Shield), Iraq and Iran and the peri-Gondwanan Carpathians, rather than the Early Cambrian successions in the central and southern European peri-Gondwanan terranes.

Grain-Size Analysis of Ancient Deep-Marine Sediments Using Laser Diffraction

Grain-size analysis of siliciclastic sedimentary rocks provides critical information for interpreting flow dynamics and depositional environments in sedimentary systems and for analysing reservoir quality of sandstone. Methods such as sieving and thin-section analysis are time consuming and unsuited for large sample numbers. Laser diffraction particle analysis is quick and reliable for analysing 100s of samples, assuming successful disaggregation. Here, we evaluate this method utilizing samples from three siliciclastic formations in Northern Italy: the Miocene Castagnola and Marnoso-Arenacea Formations, and the Cretaceous to Palaeocene Gottero Formation, which vary in degree of lithification. We focus on: 1) methods of whole-rock disaggregation; 2) methods of subsampling sediment for laser diffraction analysis; and 3) comparison of thin-section analysis with laser-diffraction particle size analysis. Using an ultrasonic bath and a SELFRAG (high voltage selective fragmentation) as disaggregation tools, this study evaluates separation of whole, undamaged grains subsequently measured by laser diffraction analysis. We show that it is possible to disaggregate ancient, well cemented rocks using an ultrasonic bath. When disaggregating samples with the SELFRAG method, grain-size measurements become less accurate and less precise with increasing sample lithification and increased presence of cement. This is likely a combination of incomplete grain disaggregation in the SELFRAG and heterogeneity within samples. Following disaggregation, we compare sub-sampling methods using a stirrer plate versus a pipette. Both produce accurate analyses, but the stirrer method is the most reliable and replicable. A comparative small subsample method, run as one whole sample with no need for subdivision into aliquots, is found to be reliable and replicable but is more susceptible to heterogeneity within field samples. When comparing laser diffraction results to grain-size volume methods estimated from thin-section analysis, thin-section sand grains are overestimated, and clay/silt grains are inaccurate. These results provide a framework for understanding potential biases introduced through various sample preparation and measurement methods.

Machine learning modeling of permeability in 3D heterogeneous porous media using a novel stochastic pore-scale simulation approach

Accurate predictions of rock permeability is critical for resource exploration and environmental management. To improve on existing approaches to permeability prediction, this study employed a stochastic pore-scale simulation approach. The petrophysical properties needed for the implementation of this approach are porosity and pore size distribution (PSD) of rock samples which can be obtained easily from mercury injection capillary pressure measurements. The approach was tested on four carbonate and five siliciclastic rock cores. To consider a wide range of possible pore connectivity scenarios that can be associated to the same PSD and porosity, the employed stochastic pore-scale simulation approach involves the generation of hundreds of 3D pore microstructures of the same PSD and porosity but different stochastic pore connectivity. Permeability is calculated by averaging the permeability distribution obtained from pore-scale flow simulations through the generated 3D pore microstructures. Permeability estimations were closer to measured permeability with this approach than with five deterministic empirical model equations. Machine learning was used to reduce the required number of pore-scale simulations by 157 times and reproduced permeability estimated from pore-scale flow simulations with a mean absolute percentage error of 10%.

Cretaceous Tethyan subduction in SE Borneo: Geochronological and geochemical constraints from the igneous rocks in the Meratus Complex

• The igneous rocks in the Meratus Complex mainly formed at ∼115–140 Ma. • The Cretaceous Meratus mafic rocks originated from the slab-related wedge mantle. • The Cretaceous granitoids represent the product of wedge-originated juvenile crust. • Meratus Complex has a NW-Australian affinity and formed in an fore-arc setting. • The Meratus Neotethyan Ocean subducted beneath the Argo fragment until ∼100 Ma. SE Borneo lies at the junction of the Pacific and Tethyan realms. The Mesozoic geological record of the region is dominated by convergent plate margin activity, although the geological details and its broader role in the SE Asia evolution are poorly documented. This paper presents geochronological, whole-rock elemental and Sr-Nd-Pb isotopic data on the igneous rocks from the Meratus Complex in SE Borneo. The Meratus ophiolite might form at the Late Jurassic-Early Cretaceous (∼150–115 Ma), and the spatially-associated Haruyan Volcanics, Belawayan granitoids and their equivalents generated in the Early Cretaceous (∼140–107 Ma). The Haruyan and Pitap formations and their equivalents are dominated by Early Cretaceous (∼140–115 Ma) volcanic rocks and late Early Cretaceous (∼115–100 Ma) siliciclastic rocks, respectively. The mafic-intermediate igneous rocks in the Meratus Complex are characterized by MgO = 2.04–13.20 wt%, TiO 2 = 0.48–1.51 wt%, Nb/La = 0.09–0.42, ε Nd (t) = +4.6–+7.7, ( 206 Pb/ 204 Pb) i = 18.15–18.61, ( 207 Pb/ 204 Pb) i = 15.41–15.63 and ( 208 Pb/ 204 Pb) i = 38.03–38.63, and originated from the slab-related mantle wedge. The granitoids share similar elemental ratios and Sr-Nd-Pb isotopic compositions with the coeval mafic rocks, with Nb/La = 0.20–0.30, ε Nd (t) = +4.8–+6.0, Δ8/4 = 26.2–38.8 and Δ 7/4 = 5.0–7.7, representing the products of the wedge-originated juvenile crust. Synthesis of all data reveals a NW-Australian affinity for SE Borneo. The Early Cretaceous fore-arc tectonic setting extends southerly into the Bantimala (SW Sulawesi) and Luk Ulo (Central Java), constituting a united Early Cretaceous Central Indonesian accretionary zone. The Meratus Ocean subducted beneath the Argo fragment since ∼140 Ma and likely assembled with the Sundaland margin at ∼100 Ma in response to the Neotethyan consumption.

New data on the stratigraphy of the Middle Jurassic siliciclastic rocks from the West Balkan Mountains (West Bulgaria)

The present study is a contribution to the lithostratigraphy of Middle Jurassic strata in the area of the Zimevitsa Plateau (West Balkan Mts, West Bulgaria). Based on its lithological and regional properties, the Dobravitsa Member is distinguished from the surrounding rocks of the Etropole Formation. The new member consists of alternating shales, siltstones and fine-grained sandstones. It also contains abundant siderite and calcite concretions, which are distributed in discrete stratigraphic horizons in both the mudrocks and coarser lithologies. Fossils are extremely rare. Poorly preserved ammonites and belemnites are found only. Based on several ammonite finds, the Dobravitsa Member of the Etropole Formation is assigned to a narrow stratigraphic interval of the lower Bajocian (unlimited, probably lower part of the Witchellia laeviuscula Zone). Although it has restricted lateral distribution, which is exclusively confined to its type-area, the Dobravitsa Member has a proper place in the formal Bulgarian Jurassic lithostratigraphic scheme, as it represents a discernible atypical development of the Etropole Formation in the West Balkan Mts region. Another emphasis of this study is laid on concretions from the Etropole Formation. Besides siderite and calcite concretions, a few examples of iron oxyhydroxide concretions, from localities outside the Zimevitsa Plateau area, are also described. The latter are also an atypical component of the Etropole Formation, which deserves a further special study and systematization, as it implies unknown history of this lithofacies, in both depositional and diagenetic terms.

Distribution, morphology and composition of mesophotic ‘reefs’ on the Amazon Continental Margin

The geomorphology of the Amazon Continental Margin (ACM) is highly heterogeneous and includes a variety of reef-like formations found in deep-water along the shelf-slope transition. The ACM has been divided into three Sectors (Northern, Central and Southern) according to the distribution of the carbonate producers and the ‘reefs’, influenced by the Amazon River plume. Here, we characterize these structures that were sampled with a manned submersible and multibeam surveys to depths of up to 230 m, exploring their relationship with the Amazon river plume and changing sea level following the Last Glacial Maximum (LGM). The shelf-slope transition and a deeper shelf break in the Northern Sector of the Brazilian portion of the ACM carry a series of prominent high-relief structures (HRS) that experience a strong fluvial influence. The tops of these features are between 110 and 165 m depths and seem to have originated during lowstands, through erosion of Pleistocene sandstones. Siliciclastic and carbonate deposits accumulated on the tops of these features in shallow waters during the LGM and early deglaciation and were gradually submerged by rising sea level and subsidence. A thin layer of encrusting organisms, coralline algae, sponges, bryozoans and serpulids presently colonizes most of these surfaces at the sites sampled and contributes to the aggregation of thin fine-grained siliciclastic deposits. The Central Sector, off the river mouth, is associated with long-term sediment accumulation and lacks a shelf break. Nevertheless, living benthic communities occur on rock outcrops. The Southern Sector is less influenced by the river plume and includes a shallower shelf-break and a prominent canyon. The surveyed outcrops of Pleistocene carbonate and siliciclastic rocks at 180 m carry thin covers of a benthic community dominated by sponges and coralline algae, which is responsible for the accumulation of a thin (up to a few centimeters) deposit of carbonate bioclasts, quartz sand and mud on the rocky substrate. Thus, the ‘reefs’ of the outer shelf and mesophotic Amazon margin are typically eroded older rocks, colonized by encrusting organisms during the LGM and deglaciation forming a carbonate veneer, which now support a mesophotic community.

Anabar–Lena Composite Tectono-Sedimentary Element, northern East Siberia

Abstract The Anabar–Lena Composite Tectono-Sedimentary Element (AL CTSE) is located in northern East Siberia extending for c. 700 km along the Laptev Sea coast between the Khatanga Bay and Lena River delta. The AL CTSE consists of rocks from the Mesoproterozoic to Late Cretaceous in age with the total thickness reaching 14 km. It evolved through the following tectonic settings: (1) Meso-Early Neoproterozoic intracratonic basin; (2) Ediacaran–Early Devonian passive margin; (3) Middle Devonian–Early Carboniferous rift; (4) late Early Carboniferous–latest Jurassic passive margin; (5) Permian foreland basin; (6) Triassic to Jurassic continental platform basin; and (7) latest Jurassic–earliest Late Cretaceous foreland basin. Proterozoic and lower–middle Paleozoic successions are composed mainly of carbonate rocks, while siliciclastic rocks dominate upper Paleozoic and Mesozoic sections. Several petroleum systems are assumed in the AL CTSE. Permian source rocks and Triassic sandstone reservoirs are the most important play elements. The presence of several mature source rock units and abundant oil and gas shows (both in wells and in outcrops), including the giant Olenek Bitumen Field, suggests that further exploration in this area may result in economic discoveries.

Tracing southern Gondwanan sedimentary paths: A case study of northern Namibian late Palaeozoic sedimentary rocks

AbstractThe northern Namibian Karoo‐aged successions are part of a Gondwana‐wide sedimentary system emerging at the Carboniferous–Permian boundary and existing for more than 50 Ma. The Karoo Supergroup sedimentary successions are of importance in understanding the evolution of the Karoo rift system. This study presents new whole‐rock geochemical data combined with detrital zircon morphology as well as U−Pb ages and Lu−Hf composition of late Palaeozoic siliciclastic rocks of the Namibian Huab Basin and Kunene area (south‐west Africa). Inferred by youngest detrital zircon U−Pb ages the Verbrande Berg Formation (lower Ecca Group) yields a Sakmarian to Asselian maximum depositional age, whereas the overlying Tsarabis Formation yields an Artinskian maximum depositional age. These ages coincide with the end of the Dwyka ice age and an overall warming and a contemporaneous evolution of the Karoo I rift system across southern Gondwana. The zircon age distribution of the investigated samples yields clusters ranging between ca 500 to 650 Ma (Cambrian–late Neoproterozoic), ca 950 to 1200 Ma (early Neoproterozoic–Mesoproterozoic) and ca 1800 to 1900 Ma (Palaeoproterozoic). Their rounded shapes characterize the zircon grains of the Kunene area and the lower Huab Basin section, whereas upper Huab Basin strata yield mostly unrounded grains. The rounded nature of zircon grains with a diverse U−Pb age spectrum putatively points towards sediment homogenization and multiple recycling stages during the deposition of the sediments and large catchment areas of the depositing rivers. As suggested by zircon grains with a low roundness value and a single Palaeoproterozoic age cluster, the upper Huab Basin successions were probably deposited under drier climatic conditions, small catchment areas and limited sedimentary homogenization. Therefore, the southern Gondwana sedimentary transport and homogenization system may change over time and is dependent on the climate prevailing during deposition. This study shows that the laws of detrital zircon are very complex and are yet to be explored.

Thermal Spring System Plumbing across a Major Normal Fault: Pah Tempe, Utah, USA

Abstract Faults, including their cores and associated fracture zones, can play an important role in controlling the flow of ground water. Pah Tempe Hot Springs at Timpoweap Canyon in southwestern Utah provides excellent exposures of the damage zone of a major normal fault and associated groundwater discharge. This includes numerous point discharges of ~40°C Na-Cl water into the Virgin River along a ~500 m stretch of the footwall damage zone of the Hurricane fault, part of the greater Wasatch-Hurricane fault system. An impermeable fault core and fine-grained rocks in the hanging wall impede cross-fault flow and force thermal waters to rise to the surface. The spectacular canyon-wall exposures permit an investigation of a fractured bedrock vadose zone as an analogue to subjacent aquifers. Photogrammetry (visual and infrared) enabled the mapping of discrete inflow locations, as well as permeable discontinuities in the canyon walls. Geochemistry, including reaction-path models, defined plausible chemical evolution pathways of thermal waters, whereas high-resolution geophysical surveys provided information on subsurface disruption and the depth to bedrock beneath Virgin River channel alluvium. The synthesis of these approaches indicates that permeable pathways in fractured carbonate rocks exhibit heterogeneous patterns. Some rock volumes contain abundant permeable fractures, bedding-plane partings, and solution cavities. Yet, within such volumes, one fracture may be permeable, whereas another only a few cm away may not. On a large scale (tens of meters), entire volumes of bedrock may be impermeable. Geophysical studies can shed light on gross fracture patterns in the bedrock aquifer but are incapable of showing which features accommodate flow. Patterns of permeability in the thick vadose zone may be the best predictor of subjacent flow paths in the aquifer. Thermal waters represent the leakage of deep brines or the mixing of Virgin River underflow with deep brines. Carbonate rocks exhibit self-organization where stochastic distribution of fracture apertures channel flow into wider features that channel additional flow. In turn, these features self-widen through solution weathering. By contrast, siliciclastic and basement rocks are not nearly as prone to dissolution. Thus, fluxes are partitioned into north-south fractures that will tend to have aperture in this east-west extending region. The results of this study help improve the conceptualization of flow systems near fault zones, and the methods employed may be a template applicable to the study of other systems.

The influence of black shale weathering on riverine barium isotopes

Barium and its isotopes are receiving growing interest in their capacity to record the variation of the oceanic biological pump through geological timescales. Nonetheless, only little is known about the continental sources and processes that can drive the Ba flux and isotope composition to the ocean. Whereas the role of processes such as secondary phase formation, sorption and biological uptake on Ba isotopes has been recently investigated, the potential of various rock sources in producing a range of Ba isotope compositions remains poorly known. In particular, black shales often exhibit enrichment in Ba that might potentially be associated with various Ba isotope signatures.In this study, we report the isotope composition of Ba in rivers with different relative contribution of black shale rocks in their catchments, located in the Mackenzie Basin (Northwest Canada). Both the dissolved and solid loads of the Mackenzie tributaries are enriched in heavy Ba isotopes with respect to the continental crust, which is consistent with an additional source to the weathering of igneous and siliciclastic rocks. Although the dissolved Ba abundance is partially driven by weathering processes, the river dissolved Ba isotope composition rather reflects a binary mixing between 1) a “classical” siliciclastic source (with a Ba isotope composition close to that of the upper continental crust δ138Ba ∼ 0.15 ± 0.05‰) and 2) an isotopically heavier source especially present in the Mackenzie Mountains (with a δ138Ba ∼ 0.40‰). The positive relationships between dissolved δ138Ba and radiogenic osmium isotope ratios, as well as with sulphuric acid production, indicate that the heavy Ba source is tightly linked to the weathering of black shale. Although the exact reason for such heavy Ba isotope signatures remains elusive, this study emphasises the potential of black shale weathering in shifting the Ba isotope composition of the dissolved flux to the ocean towards heavier values.

Petro-Mineralogical and Geochemical Evaluation of Glauconitic Rocks of the Ukra Member (Bhuj Formation), Kutch Basin, India

AbstractGlauconites occurring within the Ukra Member of Kutch Basin have remained unexplored in terms of their economic significance. The present study aimed to present a detailed physicochemical characterization of glauconite occurring in the siliciclastic rocks of Guneri and Umarsar area of the Kutch district, Gujarat, India to explore their economic potential. The study involved an integrated petrographical, mineralogical, and geochemical investigation of glauconitic rocks to highlight the occurrence, nature, and maturity of glauconite. The characterization was carried out using X-ray diffraction (XRD), X-ray fluorescence (XRF), and electron probe microanalysis (EPMA) combined with energy dispersive X-ray (EDX), Field emission gun scanning electron microscopy (FEG-SEM), Fourier-transform infrared spectroscopy (FTIR), and inductively coupled plasma mass spectroscopy (ICP-MS). Petrographic and bulk XRD analysis revealed that the glauconite occurs as green pellets constituting ~30 and 40% of the glauconitic sandstone and shale, respectively. Whole-rock analysis showed that the value of K2O varies considerably from 3.93 wt.% (sandstone) to 5.63 wt.% (shale). Mineral chemistry indicated the distinctive chemical composition of glauconite pellets containing 7.4–8.4 wt.% of K2O. The parameters, such as the distance between the (001) and (020) peaks and the large K2O content (~8 wt.%) of the glauconite fraction reflect an evolved to highly evolved stage of maturation. The morphological and spectral signatures further support the high degree of maturation in glauconites. Trace-element analysis implied that the glauconitic sandstone and shale contain elements such as Zn, Mn, Cu, Co, Mo, and Ni, which serve as essential micronutrients for plants. These data sets collectively constitute part of a preliminary study which is prerequisite to beneficiation, but further evaluation of its potential as a potash fertilizer also is needed.

The unique Cambro-Ordovician silicic large igneous province of NW Gondwana: Catastrophic melting of a thinned crust

Cambro–Ordovician silicic magmatism in the Central Iberian Zone of the Iberian Massif (Ollo de Sapo Formation, OSF) constitutes a voluminous and geochemically atypical magmatic event that formed preceding the breakup of the northern margin of Gondwana. To date, and due to uncommon geochemical signatures, such as a high Fe, Mg content compared to anatectic melts and the departing from the calc-alkaline trends, the origin of such magmatic event is not fully understood. Herein, we report a data-analysis of geochemistry linking magmas and source compositions. The analysis of the combined data from multiple studies ascribes the geochemistry of the OSF rocks to a combination of extensive melting of Ediacaran metasiliciclastic rocks and a Ca-rich component. It is hypothesized that fluids released by crystallization of mafic magmas contributed to partial melting of a thick metasedimentary pile represented by Ediacaran siliciclastic rocks. Such melting event gave rise to a mobile nebulite or migma, which was able to extrude and form the super-eruption or “flare-up” that characterizes Cambro-Ordovician silicic magmatism at the Gondwana margin. Fast, catastrophic crustal melting with large-scale restite entrainment, triggered by the influx of mafic magma-derived fluids, are considered the main cause of the unique features of this Cambro-Ordovician atypical silicic large igneous province of Gondwana.

The provenance of coarse-grained turbidite sandstones in the Kırkgeçit Formation(western part of the Elazığ Basin-east Turkey)

Modal analysis of sandstones for conglomerate rich marine basins is useful for investigating the provenance types surrounded by plate tectonics. Different kinds of siliciclastic rocks are important indicators for defining the paleogeography and geotectonic conditions of the sedimentary basin by provenance analysis. This paper, which focuses on the petrography and provenance of conglomerate rich turbidite systems, is one of the rarest studies on the sedimentary characteristics in the scientific literature. In this context, the study was carried out in the western part of the Elazığ Basin. The Middle Eocene?Oligocene basin infill called the Kırkgeçit Formation is characterised by the conglomerate rich submarine channel deposits and coarse-grained turbidite sandstones. Petrographically, the coarse-grained sandstones of the Kırkgeçit Formation are composed of litharenite and rarely feldspathic litharenite, lithic arkose and rock fragments. Mostly the components are derived from volcanic and plutonic rocks of the Elazığ Magmatites. Fossils and fossil fragments are transported from the shallow part of the western Elazığ Basin. The components transported from metamorphic rock fragments, which are rarely observed in the sandstone samples, are composed of recrystallized limestones and derived from Keban Metamorphites in the northern part of the basin. The provenance studies and petrographic analyses indicated that the conglomerate rich channels and coarse-grained sediments of turbidite sandstones in the Kırkgeçit Formation were plotted mostly to the recycled orogenic and undissected arc type source rocks. Therefore, this type of source rocks has been reflected as a back-arc basin deposit during Middle- Upper Eocene. The geotectonic evolution of the western Elazığ Basin has also supported this remark.

Tupi Nodes pilot: A successful 4D seismic case for Brazilian presalt reservoirs

The oil and gas industry has established 4D seismic as a key tool to maximize oil recovery and operational safety in siliciclastic and low- to medium-stiffness carbonate reservoirs. However, for the stiffer carbonate reservoirs of the Brazilian presalt, the value of 4D seismic is still under debate. Tupi Field has been the stage of a pioneering 4D seismic project to field test the time-lapse technique's ability in monitoring production and water-alternating-gas (WAG) injection in the Brazilian presalt. Ocean-bottom node (OBN) technology was applied for the first time in the ultra-deep waters of Santos Basin, leading to the Tupi Nodes pilot project. We started with feasibility studies to forecast the presalt carbonate time-lapse responses. The minerals that constitute these carbonate rocks have an incompressibility modulus that is generally twice as large as those of siliciclastic rocks. This translates into discrete 4D signals that require enhanced seismic acquisition and processing techniques to be correctly detected and mapped. Consequently, two OBN seismic acquisitions were carried out. Time-lapse processing included the application of top-of-the-line processing tools, such as interbed multiple attenuation. The resulting 4D amplitude images demonstrate good signal-to-noise ratio, supporting both static and dynamic interpretations that are compatible with injection and production histories. To unlock the potential of 4D quantitative interpretation and the future employment of 4D-assisted history-matching workflows, we conducted a 4D seismic inversion test. Acoustic impedance variations of about 1.5% are reliably distinguishable beyond the immediate vicinity of the wells. These 4D OBN seismic surveys and interpretations will assist in identifying oil-bypassed targets for infill wells and calibrating WAG cycles, increasing oil recovery. We anticipate that studies of the entire Brazilian presalt section will greatly benefit from the results and conclusions already reached for Tupi Field.

Provenance of the Paleozoic to Mesozoic Siliciclastic Rocks of the Istanbul Zone Constrains the Timing of the Rheic Ocean Closure in the Eastern Mediterranean Region

AbstractThe Intra‐Pontide Suture between the Istanbul and Sakarya zones was regarded debatably either as a Neotethyan Suture or a trace of the Rheic Suture in Turkey. Here, we present U‐Pb ages and Lu‐Hf isotopic compositions of detrital zircons from the Silurian to Triassic sandstones of the Istanbul Zone. Upper Silurian‐Lower Devonian sandstone is dominated by Mesoproterozoic zircons (1950–900 Ma), with subordinate peaks at the latest Neoproterozoic to Silurian (750–420 Ma) and mid‐Archean (2850–2750 Ma) confirming their Avalonian affinity. Detrital zircon ages from Carboniferous‐Triassic sandstones show major peaks at Carboniferous‐Early Permian (360–270 Ma) and Late Neoproterozoic–Cambrian (750–480 Ma) while Mesoproterozoic zircons are insignificant. The εHf(t) values of the detrital zircons exhibit a wide range from −21.3 to +11.7, and over 62% of zircon grains have negative values, largely coinciding with those of the Paleozoic igneous rocks in the Sakarya Zone. The Istanbul Zone is devoid of Carboniferous igneous and/or metamorphic rocks. Therefore, abundant Carboniferous zircons and the disappearance of the Mesoproterozoic zircons in the Carboniferous‐Triassic sandstones of the Istanbul Zone require juxtaposition with a continental domain similar to the Sakarya and Strandja zones, which are characterized by widespread Carboniferous magmatism. We suggest that the Intra‐Pontide Suture represents the trace of the Rheic Suture in Turkey, along which Avalonia and Armorica collided during the Early Carboniferous.

Petrography and Geochemistry of Dolomites of Samanasuk Formation, Dara Adam Khel Section, Kohat Ranges, Pakistan

Replacement dolomite occurs in Jurassic Samanasuk Formation in Dara Adam khel area of Kohat ranges, North-Western Himalayas, Pakistan. This study, for the first time, document the process of dolomitization and evolution of strata bound dolomitic bodies. Field investigation, petrography and geochemistry helped in unraveling the formation of several dolomitic bodies. Petrographically dolomites comprises of: (1) medium grain crystalline planer subhedral dolomite (Dol-I); (2) fine grained crystalline anhedral non-planer dolomite rhombs (Dol-II); (3) medium to coarse grained crystalline subhedral-anhedral non-planer dolomite (Dol-III) and coarse to very coarse grained crystalline saddle dolomite cements (SD). The saddle dolomites (SD) postdate the replacement dolomites and precede telogenetic calcite (TC) cements. Stable O and C isotope analysis shows that these dolomites have δ18Ovpdb ranging from -4.09% to -10.4 whereas the δ13Cvpdb ranges from +0.8 to +2.51. Major and trace elements data show that Sr concentrations of 145.5 to 173 ppm; Fe contents of 2198 to 8215 ppm; and Mn contents of 93.5 to 411 ppm. Petrographically replacive dolomites, saddle dolomite, and δ18Ovpdb values depicts neomorphism of replacement dolomites that were formed earlier were exposed to late dolomitizing fluids. As a result of basin uplift during the Himalayan orogeny in Eocene time, dolomitization event was stopped through occurrence of meteoric water. The Main Boundary Thrust (MBT) and its splays were most likely essential conduits that channelized dolomitizing fluids from siliciclastic rocks that were buried deeply into the Jurassic carbonates rocks, leading to more extreme dolomitization.

Elastic Properties of Pannonian Basin Limestone under Different Saturation Conditions

Understanding elastic properties of reservoir rocks is essential for seismic modeling under different saturation conditions as well as lithology discrimination. Experiments on elastic properties of limestones are significantly less published compared to siliciclastic sedimentary rocks. The current study presents the results of laboratory measurements on Pannonian Basin limestone cores. The research was carried out for the first time for a hydrocarbon reservoir in the Bjelovar Depression, located in the southern part of the Pannonian Basin. Ultrasonic velocity measurements and determination of dynamic elastic properties were performed on limestone plugs, in dry and saturated condition under different confining pressure steps. Based on the results obtained in laboratory conditions, an empirical relationship between shear wave velocity (Vs) and compressional wave velocity (Vp) has been defined. The saturated samples show an effect of shear modulus weakening, while three samples have a shear modulus strengthening effect. Two models were used in the interpretation of the measured data, the Kuster and Toksöz and the Xu-Payne model. The results show that the Xu-Payne model describes the data well and the dominant pore type system in the limestone samples can been identified. The interpretation revealed an interparticle pore system with a fraction of microcracks from 20% to 35%. The results have helped to understand the elastic properties of limestones from the southern part of the Pannonian Basin, which are necessary for any process of reservoir characterization, such as porosity distribution and permeability variation.

Rare earth elements geochemistry, O and S isotopic compositions, and microthermometric data of barite from the Kuh–Ghalagheh deposit, Markazi Province, Iran

The Kuh–Ghalagheh barite deposit is located 43 km southwest of the city of Mahallat in Markazi Province, Iran. The barite mineralization occurs as a stratabound, lenticular massive orebody in siliciclastic rocks of Eocene age. Barite is accompanied by calcite, Fe- and Mn-oxides, quartz, and minor malachite. The concentration of total REEs (∑REE) is very low in barite, ranging from 0.38 to 6.26 ppm. Chondrite-normalized REE patterns show enrichment of LREE relative to HREE, and dominantly negative La, Gd, and Ce anomalies. The δ18O and δ34S isotopic values of the barite samples fall within narrow ranges of +4.0 to +5.6‰ and +26.2 to +27.8‰, respectively, which do not match those of contemporaneous seawater (Eocene). This suggests that isotopically modified seawater sulfate is the source of oxygen and sulfur in barite. Three types of aqueous, aqueous–carbonic, and carbonic fluid inclusions were found in barite, suggesting that two immiscible fluids (aqueous and carbonic) were involved in the deposition of barite. Salinity values in the aqueous fluid inclusions ranged from 1.57 to 13.40 wt% NaCl equivalent. The aqueous–carbonic inclusions have salinity values ranging from 9.43 to 16.84 wt% NaCl equivalent. The salinity ranges of the aqueous and aqueous–carbonic inclusions show that two fluids have mixed, one with moderate salinity (>15 wt% NaCl equivalent) from basinal origin and a second with low salinity (<5 wt% NaCl equivalent) from seawater. The broad homogenization temperature ranges of 130–258 °C for aqueous and 118–290 °C for aqueous–carbonic inclusions do not represent the actual temperatures of the trapped fluids, but were generated by thermal re-equilibration of the inclusions due to deep burial of barite. The available data are consistent with a cold seeps model for barite formation in the Kuh–Ghalagheh deposit. The entry of Ba-rich basinal brines into the sedimentary basin resulted in the reaction of Ba with seawater sulfate, and the deposition of barite in siliciclastic sediments.

The Depositional Environments in the Cilento Offshore (Southern Tyrrhenian Sea, Italy) Based on Marine Geological Data

The depositional environments offshore of the Cilento Promontory have been reconstructed based on the geological studies performed in the frame of the marine geological mapping of the geological sheet n. 502 “Agropoli”. The littoral environment (toe-of-coastal cliff deposits and submerged beach deposits), the inner continental shelf environment (inner shelf deposits and bioclastic deposits), the outer continental shelf environment (outer shelf deposits and bioclastic deposits), the lowstand system tract and the Pleistocene relict marine units have been singled out. The littoral, inner shelf and outer shelf environments have been interpreted as the highstand system tract of the Late Quaternary depositional sequence. This sequence overlies the Cenozoic substratum (ssi unit), composed of Cenozoic siliciclastic rocks, genetically related with the Cilento Flysch. On the inner shelf four main seismo-stratigraphic units, overlying the undifferentiated acoustic basement have been recognized based on the geological interpretation of seismic profiles. On the outer shelf, palimpsest deposits of emerged to submerged beach and forming elongated dunes have been recognized on sub-bottom profiles and calibrated with gravity core data collected in previous papers. The sedimentological analysis of sea bottom samples has shown the occurrence of several grain sizes occurring in this portion of the Cilento offshore.