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Ranger Rick's NatureScope is a creative education series dedicated to inspiring in children an understanding and appreciation of the natural world while developing the skills they will need to make responsible decisions about the environment. The topic of this issue is "Geology: The Active Earth." Contents are organized into the following sections: (1) "Earth on the Move," describing information and activities on the structure of the Earth, the theory of plate tectonics, and earthquakes and volcanoes; (2) "Rocks and Minerals," giving information and activities on rock and mineral composition, formation, and classification; (3) "Shaping the Landscape," providing information and activities on forces that wear down landforms and forces that build them up; (4) "Secrets of the Past," offering information and activities on how and where fossils form, what they tell about the past, and how scientists determine the ages of fossils; (5) "People and Geology," providing information and activities on the origins and uses of rocks, minerals, and fossil fuels, and some of the problems caused by their use; and (6) "Appendix," featuring bibliographic and other reference information. (WRM)

The morphology of the landscape on the island of Corsica in the western Mediterranean Sea is transient with a clear topographic asymmetry. The geology of the island can be divided into two units – Hercynian Corsica and Alpine Corsica – with contrasting lithology, climate and structural controls between them. We used topographic analysis to assess the influence of each of these factors on landscape form. Disequilibrium in the landscape is illustrated by analysing χ and Gilbert metrics, which indicate active migration of the drainage divide, along with a new metric that quantifies tributary heights above the main stem channel. The climate in the region has fluctuated dramatically from the Messinian salinity crisis through to Quaternary glaciation. However, analysis of the size and distribution of knickpoints across the island does not reflect specific base-level changes. Instead, the basement structures control valley orientation and the conditioning of the landscape by glaciation exerts strong controls on drainage evolution. [ABSTRACT FROM AUTHOR]

The Stac Fada Member (Stoer Group) is a ∼1.2 Ga melt-rich impact breccia whose source crater and, therefore, proximity remains debated. We present a detailed in situ geochemical dataset for altered impact melt clasts within Stac Fada samples from Bay of Stoer and Second Coast. These altered impact melt clasts are now predominantly composed of clinochlore. Geothermometry of this clinochlore indicates formation temperatures within the ejecta blanket at 188–231°C, in agreement with previous estimates. A positive correlation between platinum group elements Ir, Pt and Rh – apparently independent of Ni – indicates two geochemical sources for platinum group elements enrichment. We propose that these represent an Mg–Ni-rich chondritic impactor and a mafic/ultramafic-layered body within the target lithology. Spatial variation in Ni content suggests that geochemical data, in combination with field observations, may be instrumental in assessing the likely location of the impact crater. [ABSTRACT FROM AUTHOR]

We report the field geology, petrography, and geochemical and geochronological data for two dyke swarms in the Fuegian Andes, with the aim of correlating them with known suites and improving our knowledge of the magmatism of the Late Cretaceous rear arc and its relations with ductile deformation. We provide keys for correlation based on the K2O content of amphiboles. The Trapecio dyke swarm is mildly alkaline and ferriferous, with a zircon U–Pb age of 75 Ma, and therefore belongs to the Fuegian potassic magmatism (78–68 Ma). The Ushuaia peninsula dyke swarm, also known as the Ushuaia Peninsula Andesites, is shown to be high-K, calc-alkaline and magnesian, with new radiometric ages of 87–86 Ma. Although the Ushuaia peninsula dyke swarm exhibits foliation associated with ductile deformation, the Trapecio dyke swarm is post-kinematic and reveals emplacement controlled by the slaty cleavage in the metapelite host. Field and geophysical evidence suggest both swarms overlie small upper crustal plutons that are mostly buried. The variable composition of the dykes suggests a protracted history of dyke injection, mostly fed from deeper reservoirs. Contact metamorphism around both pluton–dyke systems is very weak. By comparison with adjacent plutons, we argue that the main variables controlling the development of the aureole are the small magma volumes and low rates of injection. Supplementary material: Full analytical procedures (Online Resource 1); detailed petrography of the investigated Trapecio dyke swarm samples (Table S1 and Fig. S1) with geochemical data (Table S3 and Fig. S2) (Online Resource 2); extended petrography and photomicrographs (Fig. S3) of the Ushuaia Peninsula Andesite dyke swarm (Online Resource 3); mineral chemistry data (Table S2) and the results of zircon U–Pb and hornblende Ar–Ar age measurements and ratios (Tables S4–S8) (Online Resource 4), and thermobarometric results (Table S9) (Online Resource 5) are available at https://doi.org/10.6084/m9.figshare.c.7097733 [ABSTRACT FROM AUTHOR]

The article explores the significance of Cahokia, an ancient urban center in the eastern woodlands of North America, focusing on its extensive earthen mounds and pottery production. It also discusses the distribution and characteristics of ceramic vessels like Ramey Incised, shedding light on their widespread use and their role in communication and ritual practices within Cahokia and its surrounding areas.

The article discusses the application of petrographic examination in the concrete construction industry, highlighting its role in identifying distress mechanisms, assessing deterioration severity, and serving as the initial step in broader engineering investigations. Petrography utilizes microscopes to analyze concrete constituents, offering valuable insights into concrete performance and aiding in preconstruction planning.

Dissection of relicts of ocean plate stratigraphy (OPS) in orogens could provide important insights into oceanic evolution, orogenic formation and continental growth. Here we describe a study of petrology, geochronology, geochemistry and Sr–Nd isotopes for OPS in the South Qilian Accretionary Belt with the aim of providing new constraints on the evolution of the Proto-Tethys Ocean (PTO). Three types of OPS units were recognized by their differing petrological, geochemical and isotopic features. Type 1 OPS, representing relicts of ocean islands or seamounts, comprises ocean island basalt and gabbro (t = 525 ± 4 Ma, (87Sr/86Sr)i = 0.7035–0.7039 and ε Nd(t) = +3.63 to +4.16) and (siliceous) carbonate rocks. Type 2 OPS, representing fragments of normal oceanic crust, consists of normal mid-ocean ridge basalt (N-MORB) and basaltic andesite ((87Sr/86Sr)i = 0.7059–0.7063 and ε Nd(t) = +6.33 to +7.44), chert and siliceous mudstone. Type 3 OPS could be oceanic plateau-derived and comprises enriched (E)-MORB and dolerite ((87Sr/86Sr)i = 0.7051–0.7064 and ε Nd(t) = +4.81 to +6.24), carbonate–siliceous mudstone and carbonate rock. These OPS units witnessed evolution of the PTO. Using available studies on regional arc-type magmatism and U–Pb geochronological data for detrital zircon in this study, a model of 'trench jam accompanying subduction flip induced by accretion of the OPS' is put forward. Supplementary material: Zircon U–Pb data, whole-rock major and trace element data and a supplementary figure are available at https://doi.org/10.6084/m9.figshare.c.6764637 Thematic collection: This article is part of the Ophiolites, melanges and blueschists collection available at: https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists [ABSTRACT FROM AUTHOR]

Petrology, geochronology and bulk-rock chemistry are combined to investigate the early Neoproterozoic magmatism and Cambrian–Ordovician metamorphism in the northern Swedish Caledonides. This work includes several lithologies of the Mårma terrane in the Seve Nappe Complex exposed in the Kebnekaise region. U–Pb zircon geochronology yielded crystallization ages of 835 ± 8 Ma for a mylonitic orthogneiss, 864 ± 3 Ma for the Vistas Granite and 840 ± 7 Ma for an intruded granitic dyke, whereas a gabbro and a granodiorite intrusion gave U–Pb zircon crystallization ages of 856 ± 3 Ma and 850 ± 1 Ma, respectively. U–Pb monazite dating of the mylonitic orthogneiss gave an upper intercept age of 841 ± 7 Ma and a lower intercept age of 443 ± 20 Ma. Pressure–temperature estimates derived for the mylonitic orthogneiss reveal metamorphic peak-pressure and peak-temperature of 10.5–11.75 kbar and 550–610°C and 7.4–8.1 kbar at 615–675°C, respectively. Metamorphic pressure–temperature estimates for the Vistas Granite yield 6.5–7.5 kbar at 600–625°C. Whole-rock chemistry coupled with U–Pb geochronology indicates that bimodal magmatism was related to attempted rifting of Rodinia between 870 and 840 Ma. Supplementary material: Supplementary figures and tables are available at https://doi.org/10.6084/m9.figshare.c.6675075 Thematic collection: This article is part of the Caledonian Wilson cycle collection available at: https://www.lyellcollection.org/topic/collections/the-caledonian-wilson-cycle [ABSTRACT FROM AUTHOR]

Navarino Island is located in the southernmost part of the Fuegian Andes, south of the Beagle Channel. Its geological record documents the complex tectonic history of Tierra del Fuego, which includes the opening and closure of the Rocas Verdes basin, Cordillera arc collision and subsequent subduction processes. The geology of the island is mostly composed of the Cretaceous Yahgán Formation, a marine metasedimentary sequence, which is intruded by diverse plutons that are mostly exposed on the northwestern tip of the island. We herein present a new dataset that shows the presence of three Cretaceous–earliest Paleocene magmatic suites of active margin magmatism emplaced during the early stage of the Fuegian Andes, which are referred to as (1) the Dientes de Navarino Microdioritic Sills, a suite of pre-tectonic microdioritic sills that formed at c. 101–97 Ma; (2) the Castores Plutonic Complex, a series of pre- to syntectonic gabbroic to tonalitic plutons emplaced at c. 90–87 Ma, and (3) the Samantha Monzonites, a suite of isolated monzonitic to monzodioritic post-tectonic plutons that formed at c. 66–65 Ma. These distinct magmatic episodes are recognized by field observations, geological mapping, petrography and whole-rock geochemistry integrated with amphibole and biotite 40Ar/39Ar and U–Pb LA-ICP-MS. The geochemical compositions of these rocks are consistent with a continental arc setting that existed during the interval c. 101–65 Ma. Whereas the three pulses spatially overlap in Navarino Island, the arc magmatism shows a migration (or expansion) throughout the Late Cretaceous. The locus of the arc then migrates at c. 68–66 Ma towards the SW. We suggest that this trenchward migration at c. 68–66 Ma may be associated with a change in the subduction angle. The three Cretaceous–earliest Paleocene plutonic pulses recorded in Navarino Island formed during the early stages of development of the Fuegian Andes, and are pre-, syn- and post-tectonic with respect to a major compressional event caused by the collision and obduction of the back-arc Rocas Verdes oceanic floor. Supplementary material: A detailed dataset is available at https://doi.org/10.6084/m9.figshare.c.6675416 [ABSTRACT FROM AUTHOR]

Scottish 'Newer Granites' record the evolution of the Caledonides resulting from Iapetus subduction and slab breakoff during the Silurian–Devonian Scandian Orogeny, but relationships between geodynamics, petrogenesis and emplacement are incomplete. Laser ablation U–Pb results from magmatic zircons at the Cluanie Pluton (Northern Highlands) identify clusters of concordant Silurian data points. A cluster with a weighted mean 206Pb/238U age of 431.6 ± 1.3 Ma (2 σ confidence interval, n = 6) records emplacement whilst older points (clustered at 441.8 ± 2.3 Ma, n = 9) record deep crustal hot zone magmatism prior to ascent. The Cluanie Pluton, and its neighbour the c. 428 Ma Clunes tonalite, have adakite-like high Na, Sr/Y, La/Yb and low Mg, Ni and Cr characteristics, and lack mafic facies common in other 'Newer Granites'. These geochemical signatures indicate the tapping of batches of homogenized, evolved magma from the deeper crust. The emplacement age of the Cluanie Pluton confirms volumetrically modest subduction-related magmatism occurred beneath the Northern Highlands before slab breakoff, probably restricted by crustal thickening during the c. 450 Ma Grampian 2 event. Extensive new in situ geochemical–geochronological studies for this terrane may further substantiate the deep crustal hot zone model and the association between Caledonian magmatism and potentially metallogenesis. The term 'Newer Granites' is outdated as it ignores geochronology, petrography and tectonic setting. Hence, 'Caledonian intrusions' would be a more appropriate generic term to cover those bodies related to either Iapetus subduction or to slab breakoff. Supplementary material: Full geochronological, whole rock geochemical and geobarometric data are available at https://doi.org/10.6084/m9.figshare.c.6305927 [ABSTRACT FROM AUTHOR]

Sills are important components of magmatic plumbing systems because of their role in magma storage. Previous studies have indirectly investigated sill propagation and architecture by using laboratory experiments, remote sensing, modelling and theory. However, these studies often struggle to include the complexity of natural systems, which commonly involves strong interplay between hosts and intrusions. To highlight the importance of host rock and magma interaction, we present the results from a study of combined unmanned aerial vehicle and outcrop datasets from a world-class 1.3 km long, 30 m high 3D exposure of a 12 m thick alkaline trachybasalt sill in Mussentuchit Wash, San Rafael Swell, Utah. The sill intruded into Jurassic, dominantly sandy, sedimentary rocks. Results of this study show that the propagation of the Mussentuchit Wash Sill features both fracture-driven and complex non-brittle fluid interaction emplacement, which are strongly influenced by local sedimentology and presence of porewater. Segregated melt emplaced progressively within the sill during emplacement is used to document the evolution of sill inflation. The fracture-driven propagation is initiated along sedimentary discontinuities through hydrofracturing, whereas the non-brittle fluid interaction is caused by the presence of local porewater within the sedimentary host rocks. This suggests that local lithology may exert strong control on the architecture and morphology of sills in sedimentary basins. Supplementary material: Uninterpreted images of the sill are available at https://doi.org/10.6084/m9.figshare.21269265.v1 and are included as DR1. [ABSTRACT FROM AUTHOR]

The article highlights technical and scientific investigations of the Gosford Wellhead, one of the most important Roman sculpture to enter the collection of The Metropolitan Museum of Art. Topics discussed include the wellhead's origin, manufacture, and history. Other topics discussed include the Gosford Wellhead's restoration in the 18th century, the adhesive used in the restoration, and its examination with a petrographic microscope.

DANTE LAURETTA IS SERENE AS HE PREPARES FOR THE 17 SECONDS HE'S WORKED TOWARD FOR THE PAST 16 YEARS. Lauretta, a University of Arizona planetary scientist, is transfixed by a [...]

Igneous sheet-complexes transport magma through the crust, but most studies have focused on single segments of the magma transport system or have low resolution. In the Jameson Land Basin in East Greenland, seismic reflection data and extensive outcrops give unparalleled constraints on mafic intrusions down to 15 km. This dataset shows how sill-complexes develop and how magma is transported from the mantle through sedimentary basins. The feeder zone of the sill-complex is a narrow zone below a basin, where a magmatic underplate body impinges on thinned crust. Magma is transported through the crystalline crust through dykes. Seismic data and published geochemistry indicate that magma is supplied from a magmatic underplate without perceptible storage in crustal magma chambers and crustal assimilation. As magma enters the sedimentary basin, it forms distributed, bowl-shaped sill-complexes throughout the basin. Large magma volumes in sills (4–20 times larger than the Skaergaard Intrusion) and the presence of few dykes highlight the importance of sills in crustal magma transport. On scales smaller than 0.2 km, host-rock lithology, and particularly mudstone tensile strength anisotropy, controls sill architecture in the upper 10 km of the basin, whereas sills are bowl-shaped below the brittle–ductile transition zone. On scales of kilometres and towards basin margins, tectonic stresses and lateral lithological changes dominate architecture of sills. Supplementary material: An uninterpreted and unwarped version of the seismic line in Fig. 4 (DR1), a spreadsheet showing thickness of sills and width of dykes in the study area (DR2), and assumptions and calculations of magma volume (DR3) are available at https://doi.org/10.6084/m9.figshare.c.5670470 [ABSTRACT FROM AUTHOR]

The article focuses on the dacite pumice component in the Tshirege Member of the Bandelier Tuff. The topics discussed include the distribution and characteristics of dacite pumice; its petrography; and whole rock geochemistry, specifically focusing on the different compositional groups of dacite pumice samples and their rare earth element concentrations. Also mentions about thermobarometry records initial crystallization of dacite, uprise and mingling with crystal-rich rhyolite.

This paper presents a detailed provenance analysis of the 6.5 km thick Oligocene-Pliocene foreland succession in the north Dezful embayment in Zagros, Iran. Using petrography, geochemistry and palaeoflow analysis, we determined three provenance shifts during the exhumation of the Zagros orogen. Above the Ahwaz sandstones, sourced from the Arabian craton, a sharp decrease in SiO2/Al2O3, Zr/Sc, Th/Sc, Th/Co and Th/Cr within the Gachsaran Fm. and the appearance of first-cycle sands derived from metamorphic and volcanic rocks at the base of the Aghajari Fm. characterize the onset of exhumation, rising topography and denudation of the Zagros orogenic system during the latest Oligocene and constitute the first shift. The second shift, in the middle Aghajari Fm., is marked by a distinct increase in radiolarian cherts and compatible/incompatible elements, indicating the exhumation of Neotethyan radiolarite-ophiolite allochthonous slices in the High Zagros Zone during the Tortonian (c. 9 Ma). Large quantities of carbonate clasts derived from the nearby growing Izeh Zone anticlines characterize the Messinian (c. 7 Ma) Bakhtyari conglomerates marking the third shift. In conclusion, a detailed hands-on provenance analysis of the clastic sedimentary sequences in the north Dezful embayment enabled us to determine catchment areas and shifts hitherto unstudied, thus contributing to the exhumation history of the Central Zagros orogenic system. [ABSTRACT FROM AUTHOR]

The geodynamic regime(s) that predominated during the Archean remains controversial, with the plethora of competing models largely informed by the felsic lithologies. Ultramafic-mafic rocks displaying distinctive geochemical signatures are formed in a range of Phanerozoic geotectonic environments. These rocks have high melting points, making them potentially useful tools for investigating Archean geodynamic processes in highly metamorphosed regions. We present the results of field mapping, petrography, traditional bulk-rock geochemistry and platinum group element geochemistry for 12 ultramafic-mafic bodies in the Lewisian Gneiss Complex, which is a highly metamorphosed fragment of the North Atlantic Craton in NW Scotland. Our data indicate that most of these occurrences are layered intrusions emplaced into the tonalite-trondhjemite-granodiorite-dominated crust prior to polyphase metamorphism, representing a significant re-evaluation of the magmatic evolution of the Lewisian Gneiss Complex. Of the other occurrences, two remain ambiguous, but one (Loch an Daimh Mor) has some geochemical affinity with abyssal/orogenic peridotites and may represent a fragment of Archean mantle, although further investigation is required. The ultramafic-mafic bodies in the Lewisian Gneiss Complex thus represent more than one type of event/process. Compared with the tonalite-trondhjemite-granodiorite host rocks, these lithologies may preserve evidence of protolith origin(s), with potential to illuminate the tectonic setting(s) and geodynamic regimes of the early Earth. [ABSTRACT FROM AUTHOR]

The article offers information associated with using reservoir description and regional geology to recognize problematic nonreservoir facies in Equatorial and South Atlantic Margin Basins. Topics discussed include comparison of predicted lithologies and/or composite log data with rockbased petrographic information in multiple sedimentary basins, extensive industry and academic evaluation of core and sidewall core samples from wells drilled in pre-Salt carbonate reservoirs.

Coke is an important raw material in the steel industry, and its quality directly influences the smelting of iron and steel. To improve coal quality and reduce coal blending costs, we need to predict the coke quality and optimize the coal blending scheme. In this paper, we propose a modeling and optimization method based on the characteristics of the coal blending and coking process. First, we establish a model for predicting coke quality from coking petrography data, based on Gaussian functions and Xgboost-SVR. The model has two components. In the first part, we analyze the key characteristics of the coal blending and coke process, and extract features of the vitrinite reflectance distribution with Gaussian functions. In the second part, we use Xgboost to select a representative feature subset, and then use support vector regression (SVR) to create a model for predicting coal quality. Next, we formulate a multi-constraint optimization problem to describe the coal blending costs, and solve it using a modified particle swarm optimization. Finally, we demonstrate the effectiveness of our modeling and optimization method by applying it to actual process data. This shows that our proposed method can improve prediction performance and reduce the coal blending costs. [ABSTRACT FROM AUTHOR]

The Tabacquito batholith (Frontal Cordillera, western Argentina), is mainly composed of shallowly emplaced granodiorite to minor monzogranite with abundant mafic microgranular enclaves. New sensitive high-resolution ion microprobe U–Pb zircon ages of c. 337 Ma (biotite granodiorite) and c. 284 Ma (mafic dyke) along with previously published geochronological data suggest that a long-lived magmatic system formed through at least two magmatic pulses at c. 337 and c. 322 Ma with later superimposition of Permian magmatism. The Tabacquito granitoids are metaluminous, calc-alkalic and magnesian with I-type affinity. Elevated Th/Nb, Y/Nb and La/Nb ratios along with negative Nb–Ta and positive Pb anomalies are consistent with a continental arc setting. Hf, Nd and Sr isotopic composition of the Tabacquito granitoids suggests that their source could result from mixing of an old felsic crustal component and a juvenile mafic to intermediate component. New geochronological and geochemical data together with published data reveal a continuous arc setting from the Carboniferous to the Permian in Argentina, and important magmatic compositional variations through time and space controlled by episodic fluctuations in the subduction angle of the oceanic plate. Reported and compiled data allow us to infer the continuity of the Carboniferous magmatic arc along the west margin of Gondwana. Supplementary material: Detailed petrography, analytical methods and data, zircon cathodoluminescence images and supplementary figures are available at https://doi.org/10.6084/m9.figshare.c.4763993 [ABSTRACT FROM AUTHOR]

Sediment provenance analysis is important in reconstructing chronological and spatial relationships between source area erosion/exhumation and sediment deposition in adjacent basins. Here we provide new provenance data from conglomerate clast populations, sandstone petrography, heavy mineral assemblages and U–Pb detrital zircon geochronology from the 9 km-thick, Siluro-Devonian Lower Old Red Sandstone (LORS), northern Midland Valley Basin (MVB), Scotland. The MVB developed in the foreland to the Caledonian Orogeny and comprises a mixed succession of conglomerate and pebbly sandstone interbedded with volcanic lithologies. Analysis of 554 samples (137 petrographical thin sections across 22 formations/members; 390 conglomerate clast recordings across 7 locations; 17 heavy mineral and 10 detrital zircon samples) from the entire succession shows a proximal, consistent source or sources located to the east or NE. These results indicate that sediment derived directly from areas of Scandian uplift of Norwegian lithologies is unlikely to have made a significant contribution to the LORS of the northern MVB and the provenance instead lies more proximally in both the neighbouring Dalradian Supergroup metasedimentary rocks and other contemporaneous lithologies. The coarse-grained nature of the sedimentary rocks suggests consistent and continued uplift of these lithologies throughout deposition of the LORS. Integration of these provenance techniques allows robust interpretation of basin fill from a tectonically rejuvenating source in the Caledonian foreland. Supplementary material: MVB LORS palaeocurrent data; List of sample locations is available at https://doi.org/10.6084/m9.figshare.c.4661966 [ABSTRACT FROM AUTHOR]

The evolutionary history of the NW Yangtze Block is important in interpreting its location and relationship with the Rodinia supercontinent. Although a Neoproterozoic arc-related tectonothermal event is recognized in the Micangshan area of the NW Yangtze Block, its timing and P–T conditions are poorly constrained. We address this issue by focusing on the garnet–biotite gneiss that represents the main lithology of the Huodiya Group on the NW margin of the Yangtze Block. This gneiss is predominantly composed of garnet, biotite, feldspar and quartz. The peak mineral assemblage in the matrix consists of garnet + biotite + quartz + plagioclase + K-feldspar. The retrograde stage is characterized by embayed rims of the garnet and its associated biotite in the matrix. The P–T conditions in the peak and retrograde stages are constrained to 7–8 kbar and c. 710°C and 5–6 kbar and 650–675°C, respectively, and suggest that 4–5 vol.% melt was produced during an upper amphibolite–granulite facies metamorphic event. The first report of monazite U–Pb dating in the Huodiya Group of the Micangshan area yielded a weighted mean 206Pb/238U age of 802 ± 5 Ma. The studied samples contained detrital igneous zircons with 206Pb/238U dates >800 Ma, whereas the metamorphic zircons yielded a weighted mean 206Pb/238U age of 797 ± 9 Ma. Based on the compressional tectonic environment and previous studies, we propose that the Yangtze Block was probably located on the periphery of the Rodinia supercontinent. Supplementary material: The analytical methods are summarized in Supplementary Text File 1. Representative mineral composition and the results of U–Pb isotopic analyses of monazites and zircons are presented in supplementary table 1–7. The results of trace element concentrations in garnets are presented in Supplementary table 8. https://doi.org/10.6084/m9.figshare.c.4698356 [ABSTRACT FROM AUTHOR]

This paper investigates transport mechanisms involving carbonate cementation in Eocene, tight-oil sandstones in Bohai Bay Basin, China, to determine potential mass transfer between adjacent mudstones and sandstones. Evidence from petrology, geochemistry, and numerical modeling suggests two generations of carbonate cementation: (1) early nonferroan calcite (formed at 28°C-41°C) and dolomite (formed at 45°C-63°C); and (2) later ferroan calcite (formed at 105°C-124°C) and ankerite (formed at 101°C-137°C). Based on a one-dimensional model for a coupled sandstone-mudstone system under low and high temperatures, different distribution patterns of carbonate cements reflect episodic concentration gradients that led to diffusive transport of bicarbonate species during progressive burial. Firstly, extensive precipitation of early nonferroan calcite followed by dolomite at or near mudstone-sandstone contacts resulted from initial concentration gradients related to different compositions in primary mineral assemblages. Secondly, introduction of aqueous CO2 from adjacent mudstones into sandstones resulted in dissolution of early nonferroan carbonates and led to diffusive transport of bicarbonate species. These bicarbonate species were incorporated with Fe2+ and subsequently reprecipitated as ferroan carbonate minerals at distances greater than 2 m (>6.6 ft) from sandstone-mudstone contacts. Therefore, short-distance diffusive transport is inferred to have been the predominant transport mechanism associated with carbonate cementation. Large-scale mass transfer between sandstones and adjacent mudstones occurred in a relatively open geochemical system on a very local scale. Numerical model results show that low porosity zones (2.6%-5.1%) exhibit coherence with high abundances of carbonate cements (13.9%-21.2%). Tightly cemented intervals were created by different generations of carbonate cementation and resulted in destruction of sandstone reservoir porosity. [ABSTRACT FROM AUTHOR]

A recent study conducted by researchers at Yangtze University in Wuhan, China, explored the characteristics of Chang 7 shale oil from the Longdong area in the Ordos Basin. The study utilized various techniques such as organic geochemistry experiments, X-ray diffraction, and nuclear magnetic resonance to analyze the pore structure and oil occurrence in the shale samples. The findings revealed the presence of different types of pores, with micropores and mesopores being the main contributors to the total pore specific surface area. The study also identified factors influencing the occurrence of free oil and established an occurrence model. The research concluded that the proportion of free oil is negatively correlated with clay mineral content and total organic carbon, but positively correlated with saturated hydrocarbon content and the volume of pores larger than 20 nm. These findings could be valuable in identifying favorable shale oil target areas. [Extracted from the article]

Scientists have been forced to reconsider how they identify life in the most ancient rocks on earth--and elsewhere in the solar system. Prehistoric creatures left seemingly endless proof of their existence fossilized in age-old rocks. These signs of life are unmistakably distinct from their stony tombs. But the more ancient the creature, the more obscure its grave. High-powered microscopes enabled geologists to detect apparent fossils in earthly rocks an astonishing 3.465 billion years old--as close as tangible fossils may ever take us to the time when simple inorganic molecules first self-replicated and began selectively interacting with their environment, defining life's earliest moments. By 1996 techniques for measuring slight variations in the chemical makeup of carbon samples seemed to solidify previous hints that life existed at least 365 million years earlier. That same year the stunning announcement that a meteorite found in Antarctica was carrying 3.9-billion-year old biosignatures from Mars further energized scientists, who grew more confident in their ability to detect past life from faint traces in rocks. In early 2002 confidence over the widely accepted views on earthly evidence experienced a similar meltdown. A flurry of research has cast serious doubt on interpretations of the earth's two oldest geologic records of life, in Greenland and Australia. Some evaluations of the geology suggest that the rocks formed in environments where life never could have thrived. Others question whether lifeless chemistry might have been able to mimic the special traces of carbon or even the shapes of microscopic fossils--rendering these clues useless as biosignatures. The revisionist analyses are fueling an ongoing debate over how anyone can ever be sure of correctly identifying primitive life on earth--or elsewhere in the solar system. INSETS: Biosignatures at a Glance;Martian Magnets.

The Stac Fada Member of the Mesoproterozoic Stoer Group (Torridon Supergroup) in NW Scotland is a proximal ejecta blanket surrounding an unidentified asteroid impact crater. A combination of field observations of the ejecta deposit and underlying strata, the geographical distribution of terrane-identified basement clasts found embedded in the impactite, and anisotropy of magnetic susceptibility of the impact melt rocks at different locations can constrain the crater location to be about 15–20 km WNW of Enard Bay and thus buried under Mesozoic sediments in The Minch. Syncompressional structures within the suevite at Stattic Point give a clear indication of a southeasterly direction of mass motion. The signatures of two different terranes within the Lewisian gneiss help identify the origin of clasts found in the impactite at three locations. These clasts are unshocked and interpreted as having been swept up by the density current post-impact; their geographical distribution provides an important clue to ejecta emplacement pathways crossing the Assynt and Gruinard terranes. Anisotropy of magnetic susceptibility is used to measure flow direction in pyroclastic density current deposits and is applied here to derive a direction of motion for the impactoclastic density current. It provides good agreement with the other independent methods. [ABSTRACT FROM AUTHOR]

This article presents information about several social developments around the world, as of September 13, 1877. The Fifth Annual Report of the Boston Board of Health contains valuable suggestions with regard to the sewerage of the city; the treatment of tramps; and the advisability of providing a public ambulance for the removal of persons falling sick in the streets. Clarence King, of the United States Geological Survey of the Fortieth Parallel, has just issued Vol. vi. of his report to the Chief of Engineers, "Microscopical Petrography," by Ferdinand Zirkel. A school of drawing and painting has been established in Boston in connection with the Boston Museum of Fine Arts, but under a different management.

The history of subduction below the Aegean region and western Anatolia is hampered by a lack of comprehension of the correlations between the Cyclades and the Menderes Massif. The Dodecanese Archipelago, which is critical for this discussion, has received very little attention so far. This study is focused on the island of Leros, where two tectonometamorphic units can be observed: the upper Marina unit and the lower Temenia unit. The field study, including new field mapping and structural observations, reveals that the Temenia unit has been exhumed under the Marina unit through a top-to-the-NE ductile shearing followed by a top-to-the-SW brittle deformation cutting the Temenia-Marina contact. The description of metamorphic aragonite and blue amphibole, complemented by Raman spectroscopy on carbonaceous material (RSCM) thermometry, reveals that the Temenia unit has been buried to at least 20 km depth along a cold metamorphic gradient. In terms of lithology and palaeogeographical affinities, the cover of the Marina unit is similar to the Lycian Nappes, which rest on top of the Menderes Massif and belong to the northern margin of the Pelagonian domain. The Temenia unit can then be compared with the Lower Cycladic Blueschists Nappe, which could in turn be correlated with the cover of the Menderes Massif, which has also recorded an HP-LT metamorphic overprint. [ABSTRACT FROM AUTHOR]

The Gruf complex in the Lepontine Alps is one of the rare occurrences of Phanerozoic ultra-high temperature (UHT) metamorphism in the world, but its age is still a matter of debate. Herewe present LA-ICPMS dating in a petrographic context of zircon and monazite from a UHT restitic granulite. Zircons and monazites are both included in large crystals and in retrograde symplectites. In such restitic rocks, partial melting or fluid interactions are unlikely, precluding resetting of the monazite chronometers. Zircon cores yield Permian ages, which are interpreted as the age of charnockitization. They are sometimes surrounded by a narrow rim at 32 Ma. Monazites are strongly zoned, but all yield a 31.8 ± 0.3 Ma age interpreted as the time of complete (re-)crystallization during the UHT paragenesis. We propose that the zircons dated a post-Hercynian metamorphism which is responsible for the widespread formation of granulites in the Southern Alps and the crust differentiation. This fluidabsent melting event produced refractory lithologies, such as restites in charnockites. We suggest that Gruf UHT paragenesis is alpine in age and crystallized from these refractory lithologies. We conclude that the lower restitic crust produced in the Permian had the ability to achieve UHT conditions during the fast exhumation and heating related to lithospheric thinning in Alpine time. [ABSTRACT FROM AUTHOR]

The volumetric relationship between the intrusive and extrusive components of volcanic fields is difficult to constrain. This is because either the erupted products are commonly eroded or the intrusions are concealed by overburden. Three-dimensional seismic data therefore offer a unique opportunity to study ancient volcanic provinces, as these datasets can image both components without the need for erosional dissection. This study is based on 3D seismic data from the Bight Basin Igneous Complex (BBIC), a volcanic province constructed within a sedimentary basin, offshore southern Australia. We demonstrate that the BBIC contains abundant sills and laccoliths emplaced within deltaic sediments. The intrusions have a total volume of 92-111 km³, and the lava flows and volcanoes have a combined volume of 66-76 km³ (Dense Rock Equivalent). This indicates that the ratio of intrusive:extrusive products for the BBIC is between 1:1 and 2:1. The architecture of the BBIC contrasts markedly with the neighbouring Newer Volcanics Province (NVP), which lacks abundant sills and laccoliths. Because lava flows and volcanoes in the NVP were dominantly fed by dykes hosted in basement rock, we suggest that subsurface lithology plays an important role in causing sill formation and determining the total volume of magma stored in the subsurface. [ABSTRACT FROM AUTHOR]

The article offers information on the petroleum exploration in the Upper Devonian Birdbear and Duperow Formations in North Dakota. Topics discussed include the stratigraphy of the region, including the prevalence of marine carbonates and evaporites; the lithology of both the formations; and the petroleum production from both the formations.

Feldspar dissolution, quartz cementation, and clay cementation are significant diagenetic processes in deep-water fan feldspar-rich sandstones in the Shengtuo area, Dongying sag (East China). The timing and origin of these water-rock interactions as well as the paleofluids in which relevant chemical reactions occurred were deduced using data from microscopy, fluid-inclusion microthermometry, oxygen-isotope microanalysis, and trace-element microanalysis. Three distinct, separate episodes of quartz overgrowths (referred to as Ql, Q2, and Q3) were distinguished by cathodoluminescence microscopy. The Ql quartz, identified in all porous sandstones from 2500 to 3600 m (8200 to 11,800 ft), was formed at approximately 100°C-115°C (212°F-239°F) before oil filled the reservoirs. The Q2 quartz was mainly precipitated at 115°C-130°C (239°F-275°F), accompanying or slightly postdating the main phase of oil filling, and was identified in samples from 2800 to 3600 m (9200 to 11,800 ft). The Q3 quartz was only identified in sandstones buried deeper than 3500 m (11,400 ft) and was likely precipitated in the Quaternary when temperature exceeded 130°C-135°C (266°F-275°F). Secondary ion mass spectrometry oxygen-isotope microanalyses yielded δ18Ovsmow (Vienna standard mean ocean water) values ranging from 21.42%o to 24.35%ofor Q1 quartz, from 22.03%o to 24.99%ofor Q2 quartz, and from 21.72%o to 22.9l%ofor Q3 quartz. A mass-balance calculation and quantitative petrography data of the amount of leached feldspars and associated secondary minerals suggest that the internal feldspar dissolution is likely the primary source for the authigenic clays and quartz cements in these sandstones. Positive δ18O(water) values (+0.5%o to +4.5%o VSMOW) of quartz-forming waters indicate that quartz cementation and feldspar dissolution occurred in a geochemical system with a limited volume of diagenetically modified connate water. The variations of δ18O(cements) and trace-element compositions from Q1 quartz to Q2 quartz in individual overgrowth suggest that hydrocarbon filling changed the chemistry of the pore fluid significantly; further, δ18O(water) values of the pore water increased by approximately 2%o VSMOW after oil filling. Meteoric freshwater did not contribute to quartz cementation and simultaneous feldspar dissolution. The detected CO2 and hydrocarbons in fluid inclusions in the quartz cements, the existence of CO2 in hydrocarbon-rich natural gas, and the pyrobitumen in the feldspar-hosted pores suggest that acids derived from organic matter (kerogen in source rocks and hydrocarbons in reservoirs) probably have promoted the extensive subsurface leaching reactions of feldspars in these sandstones. The ongoing development of Q2 and Q3 quartz suggests that quartz precipitation did not cease after oil filling. Further, diagenetic reactions likely have proceeded from water-rock interactions to hydrocarbon-water-rock interactions. [ABSTRACT FROM AUTHOR]

The Early to Middle Jurassic Stø Formation (Toarcian to Bajocian) was deposited in a relatively shallow (10 s of meter deep) epicontinental sea in northern Pangea and represents one of the most prolific reservoir intervals in the Barents Sea basin. It comprises a condensed, predominantly shallow marine succession characterized by long hiatuses and erosional reworking with several horizons of extraformational pebble grade conglomerate. Six distinct facies associations describe sedimentological environments ranging from transgressive, tidal, fluvial and regressive shoreface. Deposits are interpreted and correlated within three sequence stratigraphic units (SI to SIII) which reflect variations in relative sea-level during an overall transgression of the basin. Interpreted depositional systems show subtle variations in petrographic character, but provenance analyses reveal different sedimentary sources. Thirteen core samples distributed geographically and stratigraphically were analysed for detrital zircon U-Pb geochronology. Data show that the Southwestern Barents Sea Basin (SWBSB) was dominated by mixing of reworked material and coarse grained sediment supply from extrabasinal source areas including a Caledonian provenance in the southwest and a Fennoscandian provenance to the southeast. Intra-basinal erosion of underlying strata with Triassic zircon grains dominate in northern parts of the basin. [ABSTRACT FROM AUTHOR]

Some of the world's largest oilfields contain reservoirs in Lower Cretaceous (Hauterivian-Albian) clastic successions of the Middle East. They comprise sandstone-prone intervals of hundreds of metres thickness deposited in nonmarine to paralic settings on a very shallow gradient, otherwise carbonate-dominated, passive margin. This study integrates petrography, X-ray powder diffraction, heavy mineral analysis, mineral chemistry, zircon geochronology and palaeodrainage basin scale calculations to determine the likely provenance of the clastic deposits. Regional geological considerations are then used to suggest the likely driving mechanisms for the clastic influx. The sediments are highly texturally and chemically mature with low-diversity heavy mineral assemblages, suggesting extensive weathering and sediment recycling. The mixture of heavy minerals derived from metapelitic, metamafic and granitic domains at variable metamorphic grades is consistent with erosion of a complex heterogeneous basement or recycling of multiple earlier cycle sediments. Comparison with published data suggests an Arabian Shield provenance, with input from Precambrian basement and Palaeozoic sedimentary cover both possible. This is consistent with drainage basin scaling calculations. Large-scale tectonic reorganization associated with opening of the South and Equatorial Atlantic together with mantle plume related uplift in the northern Arabian Shield is postulated as the main driving mechanism of clastic influx. [ABSTRACT FROM AUTHOR]

Geological well logs (conventional well logs, electrical and sonic image logs and nuclear magnetic resonance [NMR] logs) are integrated to build the predictable models of the carbonate reservoirs. Keywords: Beijing; People's Republic of China; Asia; Chemicals and Chemistry; Alkalies; Anions; Carbonates; Carbonic Acid; Diagnostics and Screening; Health and Medicine; Nuclear Magnetic Resonance EN Beijing People's Republic of China Asia Chemicals and Chemistry Alkalies Anions Carbonates Carbonic Acid Diagnostics and Screening Health and Medicine Nuclear Magnetic Resonance 1575 1575 1 05/02/23 20230505 NES 230505 2023 MAY 5 (NewsRx) -- By a News Reporter-Staff News Editor at Health & Medicine Week -- Current study results on Chemicals and Chemistry have been published. [Extracted from the article]

The Permian Khuff-C reservoir in Saudi Arabia is known for its lateral and vertical heterogeneity caused mainly by dolomitization. Detailed petrographic analysis of 600 thin sections, from six cored wells, revealed three main replacive dolomite fabrics: (1] fabric-preserving mimetic (FPM), (2) fabric-preserving nonmimetic (FPNM), and (3) fabric-destructive (FD) dolomites. Crystal sizes are mostly less than or equal to 20 pm for FPM dolomite, less than or equal to 50 pm for FPNM dolomite, and less than or equal to 100 pm for FD dolomite. The FPM dolomite decreases in abundance, and FPNM dolomite increases in abundance, with increasing grain content of the facies. The ξ18O values of dolostones (although considered an obsolete term, dolostone is used here to mean rock containing ≤80% dolomite) indicate early dolomitization at low temperatures in Permian seawater or evaporated seawater, with landward facies (mudstone and wackestone) generally dolomitized by more evaporated waters and seaward grainy facies generally dolomitized by less evaporated, more normal marine seawaters. Stratigraphic variations in the dolostones' ξ18O values track with facies variations through fourth-order depositional sequences and indicate that different stratigraphic bodies of dolomite formed from seawaters with different degrees of evaporation. The ξ13C values of the dolostones exhibit temporal trends inherited from the precursor limestones. Variations in the lateral and vertical abundance of dolomite and dolomite fabrics, in the propensity for each facies to be dolomitized, and in the dolomites' oxygen isotopic values all suggest that multiple dolomitization events occurred in the Khuff-C reservoir as depositional cycles accumulated, with some dolostones overprinted by younger events. Average porosities of grain-rich dolostones are greater than those of mud-rich dolostones, indicating that depositional facies preordained porosity distribution within the dolostones. However, the more evaporated the dolomitizing fluid, the more likely dolomitization resulted in lower porosity regardless of facies. [ABSTRACT FROM AUTHOR]

During the first semester of 2017, Poás Volcano, in the Central American Volcanic Arc (CAVA) initiated a period of volcanic unrest that included high energy phreatomagmatic and magmatic eruptions. The most notable eruptions occurred on April 14th and April 22nd of 2017, which produced abundant ashes and ballistic materials in the form of blocks and bombs. Here, we present results from the petrographic analyses conducted in the collected material from the largest eruptions of April 2017. Mineral textures observed on the petrographic analyses show evidence of reactivation and fragmentation of a crystal mush in the magma chamber, triggering re-melting episodes, volatile exsolution, and an increase in the pressure of the system, all of which are expected conditions during an eruption episode. Our analyses done on juvenile and non-juvenile material suggest that processes of magma mingling and injections of new batches of material of different compositions have played an important role throughout previous eruptions and likely in the current phase of volcanic activity in Poás. [ABSTRACT FROM AUTHOR]

Seismic reflection data allow for the 3D imaging of monogenetic edifices and their corresponding plumbing systems. This is a powerful tool in understanding how monogenetic volcanoes are fed and how pre-existing crustal structures can act as the primary influence on their spatial and temporal distribution. This study examines the structure and lithology of host-rock as an influence on edifice alignment and provides insight into the structure of shallow, sub-volcanic monogenetic plumbing systems. The anticlinal Ben Nevis Structure, located in the northerly extent of the Faroe-Shetland Basin, NE Atlantic Margin, was uplifted during the Late Cretaceous and Early Paleocene by the emplacement of a laccolith and a series of branching sills fed by a central conduit. Seismic data reveal that multiple intrusions migrated up the flanks of the Ben Nevis Structure after its formation, c. 58.4 Ma (Kettla-equivalent), and fed a series of scoria cones and submarine volcanic cones. These monogenetic edifices are distributed around the crest of the Ben Nevis Structure. The edifices are fed from a complex network of sills and transgressive sheets, involving lateral magma migration of tens of kilometres before extrusion at the surface. This work highlights the importance of underlying basin structures in influencing the sites and development of subaerial monogenetic fields, and the importance of lateral magma flow within volcanic systems. [ABSTRACT FROM AUTHOR]

New U-Pb zircon ages from rhyolite samples of the Fishguard Volcanic Group, SW Wales, confirm a Middle Ordovician (Darriwilian) age for the group. One of the samples is from Craig Rhos-y-felin, which has recently been identified on petrological and geochemical grounds as the source of much of the debitage (struck flakes) at Stonehenge. Analysis of a Stonehenge rhyolite fragment yields an age comparable with that of the Craig Rhos-y-felin sample. Another Stonehenge fragment, thought to come from orthostat (standing stone) 48 and on petrographical grounds to be derived from the Fishguard Volcanic Group (but not Craig Rhos-y-felin), yields an age also consistent with a Fishguard Volcanic Group source. [ABSTRACT FROM AUTHOR]

Low-maturity Boquillas Formation (Eagle Ford Formation-equivalent) organic-lean calcareous mudrock samples collected from outcrop were heated in gold tubes under confining pressure to investigate the evolution of organic matter (OM) pores and mineral pores. The majority of OM in the Boquillas samples was migrated petroleum (bitumen) based on evidence from geochemical analyses, solvent extraction, and scanning electron microscopy (SEM) petrography. The SEM images showed several diagenetic events--including framboidal pyrite precipitation and euhedral calcite, quartz, kaolinite, and chlorite cementation--that were all interpreted to have occurred prior to petroleum expulsion and pore-scale to bed-scale petroleum (bitumen) migration. Two major pore types were present prior to heating: primary mineral pores and modified mineral pores with migrated relic OM. From heating experiments, pores were found to be associated with stages of OM maturation. During the bitumen generation stage, modified mineral pores were dominant, and primary interparticle and intraparticle pores were present. During the oil generation stage, modified mineral pores with isopachous OM rim were observed to be the most abundant pore type. During the gas generation stage, both modified mineral pores and nanometer-sized spongy OM pores were predominant. We interpreted the occurrence of modified mineral pores to be the result of (1) oil and gas filled or partially filled voids that developed during petroleum migration and water expulsion; (2) voids after removing of oil, gas, and water during sample preparation; and (3) trapping of water molecules. The formation of these nanopores was interpreted to be related to gas generation and structural rearrangement of OM. [ABSTRACT FROM AUTHOR]