Glauconite Grains Research Articles

On the radiometric significance of glauconies in studies of provenance: An example of the quaternary marine sequences of the Rio Grande Cone (Pelotas basin, southern Brazil)

The sediments of the Pleistocene-Holocene marine sequences of the Rio Grande Cone (RGC) (offshore Pelotas Basin, southernmost Brazilian Margin) are dominantly composed by muddy facies with thin interspersed sandy layers containing abundant very fine-to coarse green grains, heavy minerals assemblage, shards and planktonic foraminifera. These components contribute for a better understanding of the RGC filling during the Pleistocene-Holocene. However, the aim of this work was focused in the radiometric dating of the green grains as tool for provenance studies in marine sedimentary sequences. Based on Electron Microprobe, Scanning Electron Microprobe, Transmission Electron Microprobe and optical analysis the green grains occur as: (01) yellowish-green grains with smooth surfaces, low K2O and moderate Fe2O3 contents, (02) pale green grains with surfaces slightly fractured with moderate K2O and Fe2O3 contents, and (03) dark green grains characterised by fractured (cracked) surfaces and high of K2O and Fe2O3 contents. These characteristics classified them as glauconitic minerals ranging from glauconitic smectite to glauconitic mica (glauconite) indicating the first (nascent) and intermediate (slightly-evolved and evolved) stages of the glauconitization process. K–Ar radiometric dating indicated ages from 33.2 ± 0.99 to 6.69 ± 0.54 Ma corresponding from Rupelian Stage (Oligocene) to Messinian Stage (Miocene) to these grains. Considering these glauconitic grains within a Quaternary sequence, an allochthonous (detrital) origin was attributed whose probable source areas were older sedimentary sequences exposed on the seafloor along fold-and-thrust belts related to the gravitational collapse of the RGC depocentre. After eroded the glauconitic minerals probably were distributed by countourite currents and deposited within the Quaternary deposits of the RGC.

Sedimentary environment and benthic oxygenation history of the Upper Cretaceous Austin Chalk Group, south Texas: An integrated ichnological, sedimentological and geochemical approach

ABSTRACTOxygen concentration in the ocean is vital for sustaining marine ecosystems. While the potential impacts of deoxygenation on modern oceans are hard to predict, lessons can be learned from better characterizing past geological intervals formed under a greenhouse climate. The greenhouse Cretaceous containing several oceanic anoxic events characterized by widespread oxygen‐deficient water is ideal in this regard. The Austin Chalk Group in south Texas (USA) shows organic‐rich intervals that can be linked to oxygen depletion in the ocean, but the exact bottom water oxygenation conditions have not been estimated. This study aims to reconstruct both sediment interstitial and bottom water oxygenation history during Austin Chalk Group deposition by integrating detailed ichnological, sedimentological and geochemical (X‐ray fluorescence and X‐ray diffraction) analyses, thereby providing a consistent model that may be applicable across a range of marine shelf settings. The 141.12 m Gise #1 core contains a continuous record of the Austin Chalk Group, providing an opportunity for unravelling oxygenation and deoxygenation events. Whereas the anaerobic–exaerobic deposits are essentially nonbioturbated, four oxygen‐related ichnocoenoses are defined, further refining the transition of aerobic to dysaerobic conditions in the sediment interstitial water. Omission surfaces and glauconitic grains, products of current‐induced scouring and condensation, suggest sporadic high‐energy events in the Austin Chalk Group ramp that drove elevated terrestrial inputs. Geochemical data further help to identify anoxic bottom water conditions within the anaerobic facies. Additionally, the lowermost part of the Austin Chalk Group illustrates redox cycles, whereas dilution events characterized by elevated terrestrial input are identified throughout the rest of the Austin Chalk Group. The evolution of oxygenation levels in sediment interstitial water and bottom water disputes the existence of a long‐lasting oxygen‐deficient sea in south Texas. The refined depositional model may be applicable to coeval shelfal settings. Moreover, the results provide insights into variable, evolving palaeoclimatic and palaeoceanographic conditions of the greenhouse Late Cretaceous.

Origin and paleoenvironmental significance of Al-rich glauconite in the Ediacaran/Cambrian deposits of the Lublin Basin, Poland (SW margin of Baltica)

Geochemical and mineralogical analyses of glauconite from formations deposited at the Ediacaran – Cambrian boundary along the SW margin of Baltica, integrated with sedimentological characteristics of its host-rocks, are discussed in the study. SEM-EDS and XRD studies indicate evolved to a highly evolved stage of maturation of glauconitic grains, i.e. they are characterized by a high K2O content (>6,5%) and only a small amount of smectite within an ordered R > 1 glauconite-smectite (G-S) mixed layered structure. Despite its high K2O content, glauconite shows a low Fe2O3 and high A2O3 content. Such chemical composition is distinctive for Precambrian glauconites that originated from abiotic substrates. We have identified glauconite in fractures of K-feldspar and quartz, indicating that at least some of the evolved/highly evolved glauconite grains have been formed by the replacement of these minerals. We have also recognized a new type of substrate, i.e. clay coatings, which has not been reported in previous publications on glauconite. In our opinion, the green grains characterized by cleavage and higher-order birefringence, usually described as vermicular glauconite, result from glauconitization of clay coatings, rather than biotite or muscovite flakes as previously thought. Clay coatings composed of 2:1 clay minerals, mostly smectites, represent natural parent material for initiation of G-S evolution that does not require considerable structural changes as in case of biotite or muscovite.Results of glauconite investigation compiled with the sedimentary record of the Ediacaran – Cambrian succession of the Lublin Basin allow us to reconstruct the environment of glauconite formation and its subsequent history. Glauconite occurs in quartzitic sandstones that show evidence of deposition in shallow marine, high-energy environments (barrier islands, tidal flats and shoreface), but reveals widespread transport. It was formed in a lagoon environment, which, on the one hand, was an area with a relatively stable sedimentation rate compared to concurrent estuaries or tidal flats, and on the other hand, was close to the area of source material that provided detrital substrates, i.e., feldspars and clay coatings, formed in clay-rich soil horizons on river terrace or delta sediments. The latter substrate appears to be an essential indicator of the environment of glauconite formation, which may occur in close proximity to a river mouth or an actively eroded coastline.

Microscale Petrographic, Trace Element, and Isotopic Constraints on Glauconite Diagenesis in Altered Sedimentary Sequences: Implications for Glauconite Geochronology

AbstractGlauconite is an authigenic clay mineral that is common in marine sedimentary successions. Dating of glauconite to determine the depositional age of sedimentary sequences has a long history but has fallen into disfavor due to the difficulty of obtaining “pure” glauconite separates. Recent advances in sedimentary petrography and reaction cell mass spectrometry permit rapid in situ Rb‐Sr dating of carefully screened glauconite grains. However, glauconite remains susceptible to burial alteration so that successful application of in situ Rb‐Sr glauconite geochronology requires improved, microscale constraints on the impact of postdepositional alteration on glauconite Rb‐Sr systematics and articulation of robust criteria for identifying grains suitable for geochronology. Here, we address these questions by combining SEM‐EDS mineral mapping, geochemical characterization, and in situ Rb‐Sr dating of glauconite grains in partially altered lower Cambrian sedimentary sequences from the Arrowie and Amadeus basins in Australia. Our approach provides information at high spatial resolution, representing new insights into the interplay between source material, burial fluids, and diagenetic processes. Among the different glauconite classes, which we classify based on alteration and inclusion type, only the primary apatite‐bearing “pristine” glauconite returns an age within the error of the expected stratigraphic age. We attribute the preservation of a depositional Rb‐Sr age to the influence of Sr‐rich, alteration‐resistant apatite and the limited permeability of the clay‐rich strata hosting these grains. We conclude that our combined petrographic–geochemical screening approach holds considerable potential for identifying the best preserved glauconite grains for in situ Rb‐Sr geochronology.

Volcanic Origin and Significance of Glauconite Grains in the Upper Cretaceous Austin Chalk Formation in the Balcones Igneous Province, South and Central Texas

Abundant glauconite grains occur in the upper Austin Chalk A and B1 units within the confines of the Balcones Igneous Province (BIP) in the area of the Maverick Basin and San Marcos Arch in Central to South Texas. Controversy exists as to whether the origin of the grains is related to sedimentary hardgrounds or to alteration of volcanic ash and lapilli. The Austin Chalk A and B1 units were deposited contemporaneously with active volcanism (i.e., BIP), and glauconite grains are closely associated with and limited to the area of the BIP. Abundant ash and lapilli are noted near volcanic mounds, where many of these grains are converted to vermiculite and glauconite. It is well established that the BIP pyroclastics underwent alteration in seawater soon after deposition. An unambiguous transition from vermiculite and glauconite-altered volcanic fragments to sand-size glauconite is clearly demonstrated by thin-section and scanning electron microscopy analysis. Grains of glauconite (highly altered ash) deposited away from volcanic mounds have the same origin as those near the mounds. The sand-size glauconite grains can retain internal outlines of gas vesicles and other volcanic microstructures. The misidentification of these volcanic grains as sedimentary-formed glauconite, and not as altered volcanic ash, can lead to misinterpretation of the geologic history and sequence stratigraphy of the upper Austin Chalk section.

Facies Implication of GERCUS Formation with The Bathymetry and Tectonic Activity of Van-Pyrenean Phases in Haibat-Sultan Mountain, Iraqi Kurdistan Region

The Eocene red clastic strata are represented by molasses facies of Gercus Formation and well exposed at Haibat-Sultan Mountain . A sequence of about 88m thick of the formation is located in the middle part of the Mountain. Detailed investigations including field, petrographic investigations which are linked  between bathymetric fluctuation and depositional environment.  The sequence is generally found to be a shallowing upward facies which start from deep marine (Kolosh Formation) to continental environment passing through shallow marine. Petrographic studies revealed the presence of a high rate of terrigenous grains; the most abundant clasts are sedimentary rock fragments such as limestone and chert. There are less abundant clasts derived from igneous and metamorphic rocks like quartz, feldspar, and micain addition to  authigenic  grains of glauconite are also represented. The pore space between grains are filled by  red clay with carbonate cement. The provenance consisted mainly of  Balambo,Tanjiro,Shiranish,and Aqra Formations while the Igneous and metamorphic grains are reworked from ophiolte and metamorphic ource areas that cropped out on the Hinterland near Iraq-Iran border. Gercus Formation in this area is deposited in four  depositional environments: fluviatile environments( river environment ), alluvial fan (shore line) , delta, and shore face environments. The deposition and fluctuation  influenced by  paleo-slope and regional tectonism of Van–Pyrenean phases. The Middle Part of this Formation interfingers with the Avanah Formation (Carbonate Rocks)  which was deposited during the rising of sea level.

Testing Nano‐Powder and Fused‐Glass Mineral Reference Materials for In SituRb‐Sr Dating of Glauconite, Phlogopite, Biotite and Feldspar via LA‐ICP‐MS/MS

Reference materials (RMs) with well‐characterised composition are necessary for reliable quantification and quality control of isotopic analyses of geological samples. For in situ Rb‐Sr analysis of silicate minerals via laser ablation inductively coupled plasma tandem mass spectrometry (LA‐ICP‐MS/MS) with a collision/reaction cell, there is a general lack of mineral‐specific and matrix‐matched RMs, which limits wider application of this new laser‐based dating technique to certain minerals. In this work, pressed nano‐powder pellets (NP) of four RMs, GL‐O (glauconite), Mica‐Mg (phlogopite), Mica‐Fe (biotite) and FK‐N (K‐feldspar), were analysed and tested for in situ Rb‐Sr dating, complemented by isotope dilution (ID) MC‐ICP‐MS Rb‐Sr analyses of GL‐O and Mica‐Mg. In addition, we attempted to develop alternative flux‐free and fused ‘mineral glasses’ from the above RMs for in situ Rb‐Sr dating applications. Overall, the results of this study showed that among the above RMs only two NP (Mica‐Mg‐NP and GL‐O‐NP) were suitable and robust for in situ dating applications. These two nano‐powder reference materials, Mica‐Mg‐NP and GL‐O‐NP, were thus used as primary RMs to normalise and determine Rb‐Sr ages for three natural minerals: MDC phlogopite and GL‐O glauconite grains, and also Mica‐Fe‐NP (biotite). Our in situ analyses of the above RMs yielded Rb‐Sr ages that are in good agreement (within 8%) of published ages, which suggests that both Mica‐Mg‐NP and GL‐O‐NP are suitable RMs for in situ Rb‐Sr dating of phlogopite, glauconite and biotite. However, using secondary RMs is recommended to monitor the quality of the obtained ages.

Křídové pískovce u Ždírce nad Doubravou (Českomoravská vrchovina): materiál pro gotické sakrální stavby v širokém okolí

The narrow, 40 km long belt of the Cretaceous sediments called „The Dlouhá mez“ has been preserved along the NW-SE-striking Železné hory fault within crystalline rocks in the Eastern Bohemia (Fig. 1). The youngest relic of this belt corresponds to the middle part of Jizera Fm. of middle Turonian age. In the southeastern part of the „Dlouhá mez“ belt, these deposits have fine-grained, glauconitic sandstone nature. Near the town of Ždírec nad Doubravou, the sandstone had been exploited for a long time in several presently abandoned quarries and used as a building material. The old quarry at the margin of Ždírec nad Doubravou was founded in the end of the 13th century, and it was replaced by new quarries between Ždírec nad Doubravou and the village of Nový Studenec in the second half of the 19th century. This sandstone was discovered in four gothic buildings in the wide surroundings of these quarries within the course of the macroscopic investigation by the author. To confirm this discovery, the author carried out microscopic investigation of ten sandstone samples taken both in the quarries and in the gothic buildings. Petrographic features of the sandstone were also specified. Microscopic study confirmed the identical character of all studied samples. The identity of sandstone exploited in the quarries and sandstones used in gothic buildings was also demonstrated by the analysis of total SiO2 content. The sandstone is fine-grained, with matrix-supported texture, variable content of glauconite grains and fragments of silicisponge spicules and rare foraminifera tests. Muscovite and feldspars occur in accessory amounts. The sandstone is silicified and exhibits a porosity from 6–8 to 20 %. The pores with very elongated, needle-like form originated by diagenetic dissolution of silicisponge spicules while the diagenetic quartz penetrated the original clayey and possibly also calcareous matrix. The foraminifera tests were also silicified during this process. Within subordinate thin layers in sandstone, the content of terrigenous quartz grains drops below 25 % (20–22 %) while the content of silicisponges fragments increases to 10–12 %. These layers can be classified as spiculitic, sandy silicite. The sandstone from Ždírec nad Doubravou was documented in two village churches (Krucemburk, Havlíčkova Borová), in a big church in the town of Havlíčkův Brod and in the chapel in the Lipnice Castle in the town of Lipnice nad Sázavou. These buildings originated in the last quarter of the 13th and in the 14th century. These localities are from 4 to 32 km away from the quarries near the town of Ždírec nad Doubravou (Fig. 1). The sandstones were used as ashlar masonry, window jambs and tracery, vault ribs and also in sculptures (figural corbels). A further investigation can probably reveal the Ždírec nad Doubravou sandstone in a higher number of medieval buildings.

Temporal variation in sandstone composition of Miocene Jatiluhur Formation in the Bogor Trough, West Java, Indonesia

Bogor Trough in the West Java are typified by turbidity deposits with the source are mostly characterized by volcanoclastic materials from the southern area. The Trough actually receipt the sediment from both volcanoclastic materials from the south and continental source from the north. But, the discussions of sediments in term of composition and temporal variation are rare to be reported, especially the sediments from the north. This manuscript intends to discuss the temporal variation in detrital compositional and depositional facies of the Neogene sediments that delivered from the north (i.e., Sundaland) into the Bogor Trough, which is represented by Miocene Jatiluhur Formation.
 A total of 36 selected samples have been taken for identifying the minerals using a polarization microscope. Modal analysis of the Gazzi-Dickinson method was applied for this provenance study of sandstones samples, which are consisting largely of quartz and feldspar, then sedimentary rock and volcanic rock fragments, glaucony, mud chips and skeletal fragments.
 Sundaland, a continental block highland area in the north, is interpreted to have been the provenance of sediments of the Jatiluhur Formation, which is also considered to be the source area for the Paleogene sediments. Granitic igneous rocks are interpreted as the source of dominance of monocrystalline quartz grains, or the product of long-distance transport of polycrystalline quartz from metamorphic rocks
 But, however late Miocene samples (upper part of formation) represent that the size and amount of glauconite grains are increasing, and texturally mud supported. Volcanic rocks materials are also observed. The upper part of Jatiluhur Formation records the starvation of sediment discharge into the basin, which has been also promoted for development of carbonate reef Klapanunggal Formation in the self-margin setting, and suggesting that the basin have directly received or indirectly some contemporaneous volcanic provenances sediment from the southern area.

Maturation stages of glauconites: A combined electron microprobe, Raman, and thermogravimetric study

Glauconite mineral is one of the most sensitive indicators of low sedimentation rate in the marine environment. The time of residence of glauconites at the sea bottom before burial is reflected by their so-called maturity that is differentiated based on their K2O content.The present work aims to investigate the evolution of glauconites during the transition toward the highly evolved level. Complementary electron microprobe, Raman, and Thermogravimetric analysis were performed on glauconitic grains from the Belluno basin (N Italy) with different K2O content in order to verify whether the level of glauconites evolution affects the results of these surveys.The obtained results show that Raman spectra are sensitive to the grade of glauconite maturations. First, spectra of mature glauconites are more structured, due to the lower degree of Al substitution in the octahedral sites.Moreover, the position of the strongest Raman peak (Si–Ob–Si mode) at ∼700 cm−1 shows two contrasting behaviors in the early (K2O <8%) and late (K2O> 8%) stages of glauconites maturation, respectively. TGA measurements reveals that the presence of interlayer water is also related to the state of glauconites maturations. The obtained results were explained in the light of different isomorphic substitutions occurring at octahedral level in the mature and non-mature glauconites, thus allowing to obtain a deeper insight onto the mechanism of glauconites evolution.

Quaternary Glauconitization on Gulf of Guinea, Glauconite Factory: Overview of and New Data on Tropical Atlantic Continental Shelves and Deep Slopes

For a long time, particular attention was paid to glauconitization in the surficial sediments lying on the outer continental shelves of present oceans. Subsequently, the processes observed and analyzed may have served as models for studies of glauconite in Cenozoic or even Mesozoic shelf deposits. Access to the sedimentary domains of deep oceans, particularly those of contouritic accumulation fields, has made it possible to discover unexpected processes of glauconitization. Thus, the long-term prevalence of control using fairly high-temperature water has become obsolete, and the prerequisite influence of continental flows has come to be considered on a new scale. Frequently, sediments from contouritic accumulation provide a condensed and undisturbed sedimentary record without periods of sediment erosion. Glauconitic grains could possibly integrate the signatures of bottom-water masses over prolonged periods of time, which, while preventing their use in high-resolution studies, would provide an effective means of yielding reliable average estimates on past εNd signatures of bottom-water masses. In this regard, glauconitic grains are probably better-suited to paleoceanographic reconstructions than foraminifera and leached Fe-oxyhydroxide fractions, which appear to be influenced by sediment redistribution and the presence of terrestrial continental Fe-oxides, respectively. Direct methodological access to the compositions of the semi-confined microenvironments of neoformation has largely renewed the information, chemical or crystallographic, that was previously, and for a long time, restricted to macromeasurements. The various granular supports (mudclasts, fecal pellets, and foraminifera infillings) include inherited 1:1 clays (or Te-Oc; i.e., clay minerals consisting of one tetrahedral sheet and one octahedral sheet, such as kaolinite) that are gradually replaced by 2:1 clays (Te-Oc-Te) dominated first by smectite, and then by glauconite. In small pores, the water’s activity is diminished; as a consequence, the precipitation of a great number of mineral species is thereby made easier, and their stability domains are changed. A specific methodological approach allows the study of the mineralogy and chemistry of the fine-scale mineral phases and to avoid the global aspect of the analytical methods previously used in the initial studies. Wide-field micrographs taken at a mean direct magnification of 100.000 show the intimate and characteristic organization of the main phases that occur in a single grain. One or several “fine” (about 10 nanometers in scale) microchemical analyses can be recorded, and directly coupled with each interesting and well-identified structure image observed in HRTEM.

Revisiting Glauconite Geochronology: Lessons Learned from In Situ Radiometric Dating of a Glauconite-Rich Cretaceous Shelfal Sequence

The scarcity of well-preserved and directly dateable sedimentary sequences is a major impediment to inferring the Earth’s paleo-environmental evolution. The authigenic mineral glauconite can potentially provide absolute stratigraphic ages for sedimentary sequences and constraints on paleo-depositional conditions. This requires improved approaches for measuring and interpreting glauconite formation ages. Here, glauconite from a Cretaceous shelfal sequence (Langenstein, northern Germany) was characterized using petrographical, geochemical (EMP), andmineralogical (XRD) screening methods before in situ Rb-Sr dating via LA-ICP-MS/MS. The obtained glauconite ages (~101 to 97 Ma) partly overlap with the depositional age of the Langenstein sequence (±3 Ma), but without the expected stratigraphic age progression, which we attribute to detrital and diagenetic illitic phase impurities inside the glauconites. Using a novel age deconvolution approach, which combines the new Rb-Sr dataset with published K-Ar ages, we recalculate the glauconite bulk ages to obtain stratigraphically significant ‘pure’ glauconite ages (~100 to 96 Ma). Thus, our results show that pristine ages can be preserved in mineralogically complex glauconite grains even under burial diagenetic conditions (T &lt; 65 °C; &lt;1500 m depth), confirming that glauconite could be a suitable archive for paleo-environmental reconstructions and direct sediment dating.

Occurrence and origin of glauconite in the Cambro-Ordovician Bliss Formation of southern New Mexico and West Texas (U.S.A.)

ABSTRACTIn southern New Mexico and West Texas, USA, the Late Cambrian–Early Ordovician Bliss Formation is a relatively thin and dominantly siliciclastic succession that was deposited on the Proterozoic basement during a major global transgression. The Bliss Formation can be divided into two members: 1) a lower, coarser-grained member composed mostly of sandstone (quartz arenite and subarkose) that lacks glauconite and calcite cement, and 2) an upper, finer-grained member that includes glauconitic sandstone, arkosic sandstone, and mixed siliciclastic–carbonate siltstone to fine-grained sandstone, intercalated with thin carbonate beds of grainstone, packstone, and rudstone. Iron oolite and oolitic sandstone are locally exposed at the base of the upper member. Sandstone of the lower member represents upper-shoreface to foreshore deposits, whereas sedimentary structures in the upper member indicate deposition in a middle- to lower-shoreface setting, and locally in a tidal-flat environment. Intercalated carbonate beds are storm layers (tempestites). Glauconite grains are abundant in the upper member as mostly rounded to well-rounded, spheroidal to ovoidal pellets. Two types of glauconite grains are present: homogeneous, dark green grains with high K2O contents (&amp;gt; 8 wt.%; stage 4) and mottled pellets composed of a mixture of glauconite and apatite. Glauconite of the Bliss Formation is not autochthonous as proposed by earlier workers, but of allochthonous (parautochthonous) origin. Thus, the glauconite grains were reworked from deeper shelf environments in northern Mexico to the south and were transported and deposited under regressive–transgressive conditions. Mottled glauconite grains formed by the reworking of phosphatized and glauconitized micritic sediments during regression and were transported and deposited by storm-induced currents, particularly in storm layers during transgressive events. Homogeneous, mature glauconite grains probably were derived from the reworking of glauconitized fecal pellets or completely glauconitized micritic sediments during regressive–transgressive cycles. The world-wide occurrence of glauconite in Cambrian–Early Ordovician sediments indicates that glauconite formation during that period can be considered as a “global event.”

Neodymium Isotopes in Glauconite for Palaeoceanographic Reconstructions at Continental Margins: A Preliminary Investigation From Demerara Rise

Contourite sediment accumulations at continental margins are related to strong bottom water circulation, where intense winnowing can result in neoformation of authigenic grains of glauconite at the seafloor. In this study, we investigated whether such glauconite grains could faithfully record ambient bottom-water neodymium (Nd) isotopic compositions, and hence be used as paleoceanographic archives. To this purpose, we measured Nd isotopic compositions (εNd) in a series of glauconitic grains, foraminiferal assemblages, leached Fe-Mn oxyhydroxide phases, and detrital clays separated from a contourite sediment record at the Demerara slope off French Guiana (IG-KSF-11; 2370 m water depth), at a location where the present-day εNd distribution along the water column is well characterised. We show that the εNd composition of core-top glauconite grains (−12.0 ± 0.5) agrees with the expected NADW-like seawater signature at the same location and water depth (−11.6 ± 0.3), while departing from measured εNd values for corresponding detrital clays (−11.3 ± 0.2), foraminiferal (−10.9 ± 0.2), and Fe-Mn oxyhydroxide fractions (−9.2 ± 0.2). This finding indicates that glauconitic grains at this particular location are probably best suited for paleoceanographic reconstructions than foraminifera and leached Fe-oxyhydroxide fractions, which appear to be influenced by sediment redistribution and the presence of terrestrial continental Fe-oxides, respectively. Using rare earth elements (REE), we tentatively propose that the acquisition of seawater Nd isotopic signatures by glauconite is controlled by the presence of authigenic REE-bearing phosphate-rich phases intertwined within clay mineral sheets, while confirming previous findings that the process of glauconitisation results in the progressive loss of REE within glauconitic grains. Preliminary paleoceanographic implications suggest strengthened bottom-water circulation of the glacial analogue of NADW at this particular location and water depth, with a εNd signature (between −10.8 and −11.5) similar to that of modern NADW.

Glaukonite from Deposits of Different Age in Mountain Crimea

The article describes glauconites, which in stratigraphic section of the Crimean Mountains, are mainly localized among Alb-Cenomanian, Maastricht-Danian and Eocene deposits. The study of isolated mono fractions made possible to identify the characteristics of glauconites of different ages and different generations. Three generations are distinguished, reflecting a sequential series of glauconite transformation at different stages of sedimentary rock formation. Generations differ in density, electromagnetic, structural, and chemical properties. Together, they allow to consider glauconites as heterogeneous illite formations with a variable content of swelling smectite layers, replaced by “hard” illite packets. This led to stabilization of the glauconites structure and their self-purification from Mn, Ti, V, Cr, Ni, Co, Cu, Zn. At different stratigraphic levels glauconites also differ in trace contaminants. In Alb-Cenomanian glauconites V, Cu, Zn accumulate above Clark. Danian varieties are enriched in Cr and a little in V, and Eocene glauconites - Mn, Ni, Co, and B. The glauconites formation was an intermittent, multi-stage, recycling process. Their main mass was formed during diagenetic crystallization of Al-Fe-Si gel. The process was repeatedly interrupted by sediments’ rewashing and roiling by waves and currents. Then the glauconites formation renewed again in the form of microconcretions or of outgrowths, coatings, and shells over rewashed glauconite grains. The maximum concentration of glauconite occurred at elevated offshore areas during erosion and rewashing of glauconite-containing sediments, as well as in depressions below the wave erosion base. Diagenetic glauconite formation was optimally combined with the accumulation of glauconite grains, transported by sea heaving and currents.

Антибактериальные свойства биологически активного композита на основе глауконита

Glauconite, a natural aluminosilicate, exhibits good sorption properties, is an affordable, cheap material, and has the prospect of being used in construction, ecology, medicine, cosmetology, animal husbandry, poultry farming, agriculture, etc. An urgent task is to study the sorption activity of glauconite in the Beloozersky deposit in the Saratov region in relation to biologically active substances for the creation of antimicrobial composites. The elemental composition and surface morphology of glauconite grains are determined. The sorption capacity of glauconite with respect to the pharmaceutical preparation rivanol based on acridine dye and the degree of its extraction from aqueous solutions were determined by spectrophotometry. A composite was obtained by sorption immobilization and analyzed for antimicrobial activity in relation to the standard strains of Staphylococcus aureus ATCC 6538 P and Escherichia coli ATCC 25922. An improvement in the antimicrobial properties of the immobilized preparation was revealed in comparison with an aqueous solution. The best effect of the composite in relation to Staphylococcus aureus ATCC 6538 P was determined compared to Escherichia coli ATCC 25922. The results of these studies can find practical application in veterinary medicine, poultry farming, agriculture, medicine, etc.

Green Glauconitic Marl Bed As A Sequence Stratigraphical Key For Interpretation Of Contact Between Qamchuqa And Bekhme Formations In Bekhal Area, Kurdistan Region, NE Iraq

This study incorporates a study of stratigraphy and sedimentology of the green glauconitic marl bed between Qamchuqa and Bekhme Formations in selected section of the Iraqi Kurdistan region. The studied area is located in Gali Garukaju near Rwanduz in Erbil Governorate, northeastern Iraq. Instead of Basal Conglomerate bed, the thin beds of green glauconitic marl occurs along the contact between Qamchuqa and Bekhme Formations in the studied section. Six samples were collected from this section, two samples for XRD and four samples for petrography analysis. Samples for XRD and petrographic analysis were taken from green glauconitic marl beds at the contact between two formations and from upper contact of Qamchuqa Formation and lower contact of Bekhme Formation. XRD analysis data proved the presence of glauconite in green marl bed. General petrographic observations of other remaining four samples in thin sections reveal that the upper contact of Qamchuqa Formation and lower contact of Bekhme Formation are dolomite and dolomitic limestone. The dolomite bed represents type 1 or type 2 depending on the thickness and extension of dolomite bed. Color, morphology, maturity and abundance of glauconite grain were the dominant factors used in the determination of the surface between the two formations. The result emphasizes that the surface was not a gradational surface consisting of low stand and condensed system tract (LST/CS). Two factors, color and morphology, of glauconite grains were analyzed by binocular microscope under reflected light. The morphology of most glauconite grains in this section is ovoidal and tabular with green to dark green in color. Based on these two factors the glauconite grains were within stages 3 and 4 of McCracken et al. (1996) classification and can be interpreted as evolved and high evolved in view of maturity. The presence, increase in concentration and mature grains of glauconite (evolved and high evolved) in marl beds at lower part of Bekhme Formation indicate transgressive or maximum flooding surfaces.

Structural and Crystal-Chemical Features and Rb–Sr Age of Globular Glauconite in the Ust-Il’ya Formation (Lower Riphean, Anabar Uplift)

For the first time, mineralogical, structural, crystal-chemical and isotope-geochronological data were obtained for a glauconite sample from the Lower Riphean Ust-Il’ya Formation on the Magan River (western slope of the Anabar Massif, northern Siberia). It has been established that glauconite from the lenticular layer of friable glauconitite (glauconite grains ≥80%) contains two populations of mixed-layer crystals, in which mica layers (93%) alternate with either smectite-type (7%) or vermiculite-type layers (7%) with the short-range order factor R = 3. The ratio KAl = (VIAl / (VIFe3+ + VIAl) equal to 0.45 allows identifying the micaceous mineral as glauconite with the unit-cell parameter b = 9.065 A and K2O content of 8.29%. Comparison of new data with the previously obtained mineralogical and crystal-chemical characteristics of Ust-Il’ya glauconites from the Kotuikan River section (2.5 km above the Il’ya River mouth), located 65 km south of the Magan River section, showed both similarities and differences. Analysis of the crystal-chemical heterogeneity of Kotuikan glauconite samples from rocks of different lithological types revealed peculiarities in the distribution of individual mica varieties composing the glauconite globules. Isotopic dating of glauconite from the Magan River section was performed in combination with simulation of the distribution of octahedral cations and comparison of the results obtained with Mossbauer and infrared (IR) spectroscopy data. Such an approach combined with the mineralogical and crystal-chemical analyses contributes to correct interpretation of the stratigraphic significance of isotope data. The results obtained provide grounds for the conclusion that isotopic dates of glauconite from the Magan section (1474 ± 21 Ma) coincides within the error limit with the earlier Rb–Sr and K–Ar dating of the Ust-Il’ya Formation (1485 ± 13 and 1459 ± 20 Ma, respectively) based on the glauconite in the Kotuikan section (Zaitseva et al., 2016). The former value marks the stage of early diagenesis of sediments and is suitable for estimating the age of this formation.

Petrographic characteristics of deep marine turbidite sandstones of the Upper Cretaceous Tanjero Formation, Northwestern Sulaimaniyah, Iraq: implications for provenance and tectonic setting

This study was carried out to determine the sedimentary provenance of Upper Cretaceous turbidites of Tanjero Formation. The sandstone portion of the unit has been examined based on field and laboratory studies. Seven sections were measured and described in detail on the perfectly cropped out part of the unit at the southern limb of the Sulaimaniyah Syncline. The thickness of the measured sections varies from 120 m to 192 m. The measured sections start from the top of the underlying Shiranish Formation to the syncline axis in the Tanjero Formation. For petrographic analysis sixty- nine representative rock samples were collected. Modal analysis and ternary diagrams point out that, the sandstones are calclithite (litharenite), very fine to medium grained in size consisting of chert, siltstone, mudstone, radiolarian chert and radiolarian mudstone fragments, angular to subangular in shape, very poorly to moderately sorted, transported over short distances and represent submature stage. Grain contact types and high contact index (4.7) indicate moderate to tightly packing, moderate compaction. Transported broken neritic fossil shells, moderately rounded glauconite grains, and undefinable fossils in the altered carbonate rock fragments indicate that the tectonic provenance, lithic recycle category, composed of not only the clastics as interpreted in previous studies derived from Lower Cretaceous Qulqula (radiolarian) Formation which represents deep marine, but also it revealed that a sedimentary formation must also exist in the source area, which is the Lower Cretaceous Balambo Formation.

Stratigraphic setting of fossil log sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA

The outcrop belt of the Upper Jurassic Morrison Formation in the northeastern Uinta Basin and southeastern flank of the Uinta Mountains is particularly rich in dinosaurian and non-dinosaurian faunas, as well as in fossil plants. The discovery of several well-preserved, relatively intact, fossil logs at several locations in Rainbow Draw and one location in Miners Draw, both near Dinosaur National Monument (Utah), has provided an opportunity to study the local paleobotany, stratigraphy, and sedimentology of the Morrison Formation in northeastern Utah. The Morrison Formation in northeastern Utah consists of four members. In ascending chronostratigraphic order, they are the Windy Hill, Tidwell, Salt Wash, and Brushy Basin Members. The lithology (including the presenceof glauconite grains) and fossil assemblage of the lower two members (Windy Hill and Tidwell) indicate a marine to marginal marine (coastal plain) depositional environment, whereas the lithology, fossil flora and faunaassemblage of the upper two members (Salt Wash and Brushy Basin) indicate a fluvial–lacustrine depositional environment. At least 10 fossil log sites in Rainbow Draw have been documented so far, and geologic mapping indicates that the logs and wood all occur in the same stratigraphic interval within the Salt Wash Member, approximately 17 to 27 m above the base of the member. The unit containing the logs and wood is about 11 m thick and consists of very fine to fine-grained sandstone and siltstone with indistinct bedding and no discernible sedimentary features.The logs are siliceous, some have a coaly exterior, and they range in exposed length from 0.5 to 11 m and reach diameters up to 1.1 m. In the Miners Draw area, a single siliceous log is documented in the upper part of the Salt Wash Member within a silty sandstone unit that is 4 m thick; its exposed length is about 6 m. Although the correlation of the Miners Draw log-bearing interval to the interval in Rainbow Draw is uncertain, both units are lithologically similar and both occur in the upper part of the Salt Wash Member. The logs have been identified as araucariaceous conifers that pertain to the same taxon originally described as Araucarioxylon hoodii Tidwell et Medlyn 1993 from Mt. Ellen in the Henry Mountains of southern Utah. Concurrent systematic work will prompt a nomenclatural transfer of this species to the genus Agathoxylon. Based on the abundance of large fossil logs and wood in the same stratigraphic interval in Rainbow Draw, wehypothesize that the area was covered by stands of moderately large trees of araucariaceous conifers. The sedimentological evidence suggests that the trees were not transported far from their original site of growth before they were deposited in a low-energy floodplain environment.