Glauconite Grains Research Articles

Glauconite of terrigenous-carbonate deposits from the lower Cambrian (Northern Siberia, Olenek uplift)

The detailed mineralogical peculiarities are reported for the first time of the glauconite of the Lower Cambrian (Tommotian stage) extracted from the terrigenous-carbonate deposits at the upper part of the Kessyusa series (the roof of the Mattaia Formation and the lower part of the Chuskuna Formation) as well as basal layers of the overlying limestone, too. Samples were taken from three sections of north-western slope of the Olenek uplift, northern Siberia; their stratigraphic position is given on the basis of modern data [Nagovitsin et al., 2015, and others]. Grains of layer silicates are represented by mica-smectite phyllosilicates with a relatively low content and with an elevated content of smectite layers (<10 and 10–20%, respectively), (the unit-cell parameter b = 9.06–9.12 Å). Micaceous minerals form a range from glauconite to Al-glauconite (КAl = VIAl/(VIFe3+ + VIAl) = 0.11–0.47 и 0.60, respectively; K2O content is 6.80–8.54%. Detailed litho-mineralogical peculiarities of glauconite-bearing sediments are given for the first time. Their primary deposits according to [Marusin, 2016] accumulated in the conditions of the shoreface and the offshore-transition zone of the Siberian epicontinental marine paleobasin. The origin (autogenic, allothigenic) of the studied grains, their secondary changes (rewashed in situ, phosphatization, pyritization, calcitization, ferruginization, etc.) at different stages of lithogenesis are discussed. It is shown that the obtained preliminary Rb-Sr dates (450–320 Ma) were ”rejuvenated”: they do not meet the age values previously adopted for the the Vendian-Lower Cambrian boundary — 541.0 Ma [Gradstein et al., 2012]. This may be due to various secondary alterations of glauconite grains during rewashing, transportation, and also at different stages of diagenesis in primary sediments and after re-deposition, as well as at the stages of catagenesis (deep diagenesis) and hypergenesis of glauconite-bearing rocks.

Geochemistry of uranium and thorium in phosphate deposits at the Syrian coastal area (Al-Haffah and Al-Qaradaha) and their environmental impacts.

The aim of this research was to study the geochemistry of uranium and thorium in phosphate deposits in the upper Cretaceous phosphate deposits in the Syrian coastal area. The study covered three sites, namely Ain Al-Tenah, Ain Laylon, and Al-Mhalbeh. Petrographical study showed that phosphate deposits are of nodular type with micrit to microspaite cement, containing siliceous bone residues, and green grains of glauconite, which are increasing in abundance and volume in the south toward Al-Mhalbeh, reflecting the formation of phosphate in a shallow marine environment. In addition, uranium concentration varied between 3 and 112ppm in Ain Laylon, 4.2-17ppm in Ain Al-Tenah and 5-61ppm in Al-Mhalbeh. Thorium concentration varied between 0.2 and 7.5ppm in Ain Laylon, 0.3-1.4ppm in Ain Al-Tenah and 0.3-4.4ppm in Al-Mhalbeh. The average Th/U ratio in the collected samples was within the range 0.04-0.08 except for five samples which exceeded the value 0.1. Moreover, the 226Ra/238U ratios are lower than unity in all samples, while the 210Pb/238U ratios ranged between 0.4 and 1.2 and the 210Pb/226Ra ratios were found to be higher than unity. On the other hand, the impact of leaching and mobility of uranium and thorium from deposits to the surrounding agriculture fields in the area has been studied using the Radium Equivalent Activity Index (Raeq). The equivalent radium activity was 102Bqkg-1 in Ain Al-Tenah, 403 Bqkg-1 in Ain Laylon, 407 Bqkg-1 in Al-Mhalbeh and 749 Bqkg-1 in agricultural soil samples. However, the data reported in this study can be considered as a baseline data for the phosphate deposits at the coastal area.

Formation and evolution of glauconite in the Demerara Contourite depositional system related to NADW circulation changes during late Quaternary (French Guiana)

The Demerara Plateau is a marginal plateau which forms a bathymetric relief on the sea floor. Here, contourite deposits have been studied in detail, following the recent discovery of contourite sequences likely related to the bottom currents and linked both to contour current and peculiar sea-floor morphology. A chronostratigraphic framework, based on δ18O relative variations and palaeomagnetic events in sediment cores allows correlating sediment processes to current intensity changes and major climate phases (glacial or interglacial). The studied sediments are enriched in glauconitic grains. In addition, the glauconite mineralogical maturity can easily correlate to low sedimentation rate and slightly energetic bottom currents on the seafloor. Based on these data and using the glauconitic authigenic mineral as proxy for inferring the degree of winnowing at the sediment-water interface, we might put forward the hypothesis that the intensity of NADW is higher during the glacial stages and lower during interglacial periods.

Lutetian to Priabonian dinocyst assemblages from the northwestern Tethyan margin (Adelholzen section, Eastern Alps, Germany)

This paper is the first systematic documentation of Eocene organic-walled dinoflagellate cyst (dinocyst) assemblages from the northwestern shelf of the Tethys. A taxonomic list of the rich and well-preserved dinocyst assemblages found within 28 samples collected at the Adelholzen section in southeastern Germany is presented herein. The sediments accumulated during the Lutetian and Priabonian stages at a ramp-type margin. One-hundred organic-walled dinocyst species were found at the section, which is riddled with unconformities. The composition of the successive dinocyst assemblages reflects the sea-level changes within the depositional area. Areoligera coronata and Cordosphaeridium gracile dominate the assemblage within the glauconite-rich siliciclastic sandstone (lower Adelholzen beds) of the lower transgressive system tract, which spans the calcareous nannoplankton sub-Zones NP15a and NP15b. A hiatus comprising at least c. 1.5 million years truncates these deposits and indicates an erosional episode. Rapid sea-level rise in Biochron NP16 caused a new transgression and the deposition of calcareous marlstone and limestone rich in nummulitids. In this part of the section (middle Adelholzen beds), Homotryblium tenuispinosum is by far the most abundant dinocyst species, and rare but consistent occurrences of Impagidinium spp. suggest a more open marine environment. A lithological shift from limestone to marlstone, a change from nummulitids to discocyclinids, and finally the complete disappearance of larger benthic foraminifera indicates continuous deepening of the environment. An increase in Spiniferites spp., Operculodinium spp., and occurrences of Homotryblium floripes characterize the dinocyst assemblage of this marlstone (upper Adelholzen beds). A 0.5 m thick condensed layer, which consists essentially of iron-coated glauconite grains and scattered phosphate nodules, represents the maximum flooding surface of the transgressive sequence, for which a paleodepth of c. 300 m is assumed. The overlying marlstone (“Stockletten”) of the highstand system tract is punctuated by a hiatus of c. 4.3 million years spanning the entire Bartonian. The stratigraphically important species Rhombodinium longimanum, Rhombodinium perforatum, Distatodinium ellipticum, Nematosphaeropsis labyrinthus and Selenopemphix nephroides have their lowest occurrences in the Priabonian (Zones NP18 and NP19) of the section.

The role of ferrous clays in the interpretation of wettability – a case study

Clean sandstone, with minimal clay content, is expected to be strongly water wet once the rock has been through an effective cleaning process. Even samples containing significant clay minerals are usually expected to be water wet after appropriate cleaning. However, tests carried out on core samples from Fields in three different global locations show mixed indices, even for clean state samples where no aging with crude oil has taken place. A few hypotheses for this behaviour considered herein are: whether the cleaning method was adequate, whether wettability was altered by an external factor, or if wettability was due to mineral composition. This paper presents the results obtained from wettability studies on fresh, clean and restored state core plug samples from three different Fields. Wettability indices were obtained by using the combined Amott-USBM method. Petrography was performed on sample end-trims to investigate the possible presence of halite or barite in the clean state samples, thought to be from drilling fluid infiltration, which should have been removed by the methanol cleaning cycle. This showed no organic material or salt (halite), negating wetting change from inefficient cleaning. From a reactive clays [1] model perspective, these rock samples are considered clean-sand (i.e. illite/ smectites- as total clay content), determined by XRD analysis, are lower than 10%. SEM and XRD results showed the presence of grain-coating chlorite in one sample set and glauconite grains in the others. Only once the unusual wettability indices were obtained was the grain-coating chlorite identified as chamosite by SEM/EDX, which is an iron-rich form of chlorite. The presence of chamosite or glauconite appears to influence the wetting tendency. In summary, USBM vs Amott wettability indices of the analysed samples are consistent between both methods, showing a mixed to oil-wet tendency for all samples where chamosite was identified, regardless of the initial test condition. Samples with glauconite appeared to be more mixed wet after wettability restoration. The results suggest that iron rich clay/mineral content is the main contributor to the oil wet tendency of the evaluated rocks.

Landscape Dynamics in the Caspian Lowlands Since the Last Deglaciation Reconstructed From the Pedosedimentary Sequence of Srednaya Akhtuba, Southern Russia

Surface Kastanozem of the Lower Volga area was first studied as a part of the pedocomplex, with the lower part (148–160 cm) formed in Early Khvalynian Chocolate clays (13–15 ka), the middle part (100–148 cm) in a mixed clay-loess sediment sand, and the upper part (0–100 cm) in loess. This resulted from local aeolian transport, with the source material derived from the rewinding of marine sediments. They are enriched in aggregates of Chocolate clays and glauconitic grains of a fine sand-course silt size and have similar contents of clay minerals. The high salinity of similar types evidences marine genesis for both Chocolate clays and source material for loess sediments. Clay fragments of a sand and silt size are responsible for the heavy texture and high gypsum content of loess. The study of soils with the focus on micromorphology and clay mineralogy allows the identification of the complex character of a shift from marine to sub-areal sedimentation. This shift was accompanied by short breaks in sedimentation, allowing the development of synlithogenic soil horizons of Late Khvalynian, after-Khvanynian, and Boreal time. The features of shallowly buried soil horizons confirm increased aridity after the last deglaciation. Surface Calcic Kastanozem is a full Holocene soil reflecting the present environment. However, it is deeply influenced by shallow buried soil horizons and Chocolate clays.

Lithostratigraphy and geochemical characterization of limestone deposits around Kushimaga Area in Yobe Of North-Eastern Nigeria

This study presents detailed petrographic and chemical compositional characteristic of limestone deposits for possible industrial uses and specifications. The study area falls within the Gongola basin, North-eastern Nigeria. Core limestone samples were collected from four boreholes at the depth of approximately 25 metres each in Kushimaga area around Gulani in Yobe state; north-eastern Nigeria. Lithological units were observed in the following sequence; topsoil and clay with an average thickness of 1.513m, limestone 5.553m, shale 7.853m respectively. Eleven limestone samples were selected from the boreholes for petrography and chemical analysis (Fluorescence Spectroscopy analysis). From the petrograhic studies the limestone samples are composed (visual estimate) of over 95% calcite, trace amounts of colourless already recrystallized fossil of planktonic forams and mollusc, weakly deformed greenish grains of glauconite about 0.2 to 0.3 mm in grain size, traces of opaque, isotropic, high relief iron oxide minerals with 0.03 to 0.5 mm grains sizes are present disseminated in the form of limonite. Traces of quartz and feldspar grains of silt size class were also noted in thin sections. With less than 10% grains the samples are classified as mudstone. The results of chemical analyses of limestone shows a range values of SiO 2 , 10.05wt% to 32.00wt% , CaO, 21.00wt% to 53.99wt%, MgO, 0.35wt% to 1.00wt%, Al 2 O 3 , 2.15wt% to 12.69wt%, Fe 2 O 3 , 1.28wt% to 4.90wt%, Na 2 O, 0.002wt% to 0.18wt%, K 2 O, 0.9wt% to 1.96wt%, TiO 2 , 0.21wt% to 1.00wt%, P 2 O 5 , 0.17wt% to 0.69wt%, MnO, 0.21wt% to 0.55wt%, loss on ignition, 21.98% to 36.87%, while the result of chemical classification of the limestone show a range of Ca/Mg, 23.33% to 125.68% and Mg/Ca, 0.00% to 0.04% of the Kushimaga limestone. However, the limestone beds of the research area were compared with other standard chemical industrial specifications. The study revealed that the limestone around Kushimaga area satisfies the chemical factors for Portland cement production but falls below the standard chemical specifications for other industrial uses; glass, sugar and Paint pigments and filler productions. Keywords: Argillaceous, bivariant, core, lithology, petrography and stratigraphy

Glauconite Sand from the Terrace of the Patagonian Continental Slope, Southwestern Atlantic

This brief communication describes the first finding of glauconite sand alternating with calcareous foraminiferal–coccolithic ooze on the Piedra Buena contourite terrace of the Patagonian continental slope at a depth of 2327 m. It is suggested that the fine-sand glauconite grains were supplied from the shelf during glaciations, rewashed and sorted by alongslope (contour) currents of the Circumpolar Antarctic waters with the formation of sandy glauconite contourites.

Roasting-leaching experiments on glauconitic rocks of Bakchar ironstone deposit (Western Siberia) for evaluation their fertilizer potential

Abstract This study examines factors favouring optimal release of potassium from a glauconitic rock by moderate roasting-leaching. Sieving and electromagnetic separation of oolitic iron ore deposit increases the concentration of glauconite grains substantially. Roasting and chemical leaching of this concentrate enhances the release of potassium as interlayer structures of glauconite collapses. This study records the percentage of potassium recovered from glauconite under different experimental conditions, viz., temperature, reaction time, concentration as well as volume of HCl and stages involved in the leaching treatment. Leaching of glauconite without roasting results a low recovery (

Glauconite-bearing sedimentary phosphorites from the Tébessa region (eastern Algeria): Evidence of REE enrichment and geochemical constraints on their origin

Rare earth element (REE) analyses are reported on glauconite-bearing phosphorites from northeastern Algeria. These rocks of Paleocene-Eocene age are located in the Eastern part of the Saharan Atlas, where two localities were investigated: the Djebel El Kouif in the north and the Kef Essenoun in the south. The latter belongs to the world-class Djebel Onk mining deposit. Petrographic examination indicates that phosphorite from the main layer of the Kef Essenoun deposit has a significant abundance in glauconite grains, while their occurrence in the Djebel El Kouif is restricted to the basal levels. In both deposits, glauconite grains are richer in REEs than other co-existing particles (pellets, coprolites, enameloid and dentine of marine fish teeth), but the glauconites of the Kef Essenoun deposit exhibit significantly higher REE concentration (min = 654 ppm, max = 1760 ppm, average = 1146 ppm) than those of Djebel El Kouif deposit (min = 543 ppm, max = 623 ppm, average = 584 ppm). The whole-rock REE concentrations also show substantial differences between the two deposits and the REE enrichment in the Kef Essenoun main sub-layer is more likely the result of the high glauconite content. PAAS normalized-REE patterns of the glauconite grains display similar patterns between the northern and southern localities with weak negative Ce anomalies and slight middle REE enrichments. On the other hand, the pellets and whole phosphorite grains from the northern deposit indicate a REE source from oxic-suboxic seawater, whereas those from the Kef Essenoun deposit exhibit slight middle REE enriched patterns with weak negative Ce anomaly suggesting a different environment of deposition (i.e. a tendency to reduced conditions). These geochemical results along with previous petrographic studies confirm the allochthonous character of the main phosphorite sub-layer in Kef Essenoun, where winnowing, transport and re-deposition of previously deposited phosphorites resulted in high accumulation and formation of glauconite grains. The glauconitization process of fecal pellets happened in two stages and was controlled by semi-confined micro-environments. This can explain the abundance of glauconite grains in the phosphorites from Kef Essenoun deposit and their restricted occurrence in the basal levels of the Djebel El Kouif outcrop.

Benthonic foraminiferal biostratigraphy and faunal turnover events during the Late Paleocene-Early Eocene at Darb Gaga, Western Desert, Egypt: Paleoenvironmental and sequence stratigraphic interpretations

The present study depends on qualitative and quantitative analyses for the Late Paleocene-Early Eocene benthonic foraminifera at Darb Gaga area, Baris Oasis, Western Desert, Egypt. The study Late Paleocene-Early Eocene succession consists of two rock units; Esna Formation at base and Thebes Formation (lowermost part) at top. Esna Formation is subdivided into four members stratigraphically arranged as follow: El Hanadi, Dababiya Quarry, Darb Gaga and Abu Had. Dababiya Quarry Member (marker of the P/E boundary) is characterized by the occurrence of glauconitic grains at the base confirming a minor hiatus at the P/E boundary. This hiatus led to the missing of the beds no. 1 & 2 of the five beds (lowermost part) of Dababiya Quarry Member. Four benthonic foraminiferal events are defined during the Late Paleocene-Early Eocene interval. The first one is global event at the Paleocene/Eocene (P/E) boundary, and the remainder events are local and define during the Ypresian (Early Eocene). The first event is characterized by a rapid extinction and abrupt faunal changes for the benthonic foraminiferal assemblages. This event led to the extinction of about 80% of the Paleocene foraminiferal taxa. About 72% of these taxa are temporarily extinct and reappeared soon. This event is characterized by carbonate dissolution which suggesting oxygen deficiency of oceanic bottom waters and food supply changes. Afterwards, a recovery phase of the benthonic foraminifers is directly recorded above this event and probably due to improved depositional environmental conditions. Quantitative analyses of benthonic foraminiferal assemblages at Darb Gaga section, suggest an outer shelf paleoenvironmental setting during the deposition of El Hanadi, Dababiya Quarry and Darb Gaga sediments that changes to inner-middle shelf during the deposition of Abu Had Member and inner shelf of Thebes Formation. This succession is subdivided into four depositional sequences which are bracketed by unconformities and their correlative conformities depending on integrated field investigations, lithofacies and biofacies data. These sequences are controlled by sea-level changes and/or tectonic activities that prevailed during the deposition.

Mineralogical Evolution of the Paleogene Formations in the Kyzyltokoy Basin, Kyrgyzstan: Implications for the Formation of Glauconite

AbstractAlthough several hypotheses for the formation of glauconite have been proposed, the sedimentary environment and mechanism of glauconitization are still poorly understood. In this contribution, the mineralogy and chemical compositions of sediments from Paleogene formations (Fms) in the Kyzyltokoy basin (Kyrgyzstan) were examined to better understand glauconitization processes. The samples were analyzed using microscopic petrography, X-ray diffraction (XRD), electron probe microanalysis (EPMA), and X-ray fluorescence (XRF). Interlayered diatomite-argillaceous rocks were newly identified within the diatomites of the Isfara Fm. Glauconite from the Kyzyltokoy basin displayed two stages of maturity: 1) early stage (nascent) glauconite grains composed of ∼3.5% K2O and ~8% FeOT; 2) late-stage (highly evolved) glauconite grains composed of 7–9% K2O and ~27% FeOT. The early stage glauconite grains in the Hanabad Fm green clay (green clay is clay with a greenish color) indicate interruptions in glauconitization processes, whereas the (highly) evolved glauconite grains show a completed glauconitization process along the contact between the Hanabad and Sumsar Fms. Hematite was detected in the red clay (clay with reddish color) of the Sumsar Fm and probably formed by glauconite disintegration. Accordingly, the Paleogene Fms depositional conditions were of three types: 1) beginning of glauconitization with interruptions, 2) completion of glauconitization, and 3) glauconite disintegration. Glauconitization in the Kyzyltokoy basin, thus, likely occurred via a combination of dissolution, precipitation, and recrystallization processes.

Depositional environment of Paleogen amber-bearing quartz-glauconite sands from Zdolbuniv (Rivne region, NW Ukraine): mineralogical and petrological evidences

Abstract Amber-bearing sands from Zdolbuniv mine are Paleogene fine-grained (0.6-0.12 mm) clastic rocks. The material is poorly rounded and moderately sorted out. It mainly consists of quartz, glauconite, and subordinately, feldspars (K-feldspars and plagioclases), mica, carbonates, zircon, epidote,fossil resins (Baltic amber) and ore minerals such as hematite, rutile, anatase, ilmenite. The presence of glauconite in the sands proves that sedimentation basin had to be marine reservoir. The variable composition of individual glauconite grains suggests the environmental conditions had to change during the sedimentation of clastic rocks. The occurrence of minerals, assembly such as zircon, epidote, ilmenite, rutile, anatase in the sands as well as the brown CL color of quartz grains, may suggest that majority of clastic material originated from metamorphic rocks, most probably coming from the Ukrainian Shield. Together with metamorphic material the fragment of fossil resins, i.e. Baltic amber, from the Paleogene off-shore forests could be transported to the sedimentation basin. Nowadays the bottom part of the analyzed profile is the most promising for the recovery of glauconite, whereas the exploration of Baltic amber may be initiated from the top of the profile.

Economic potential of glauconitic rocks in Bakchar deposit (S-E Western Siberia) for alternate potash fertilizer

This paper explores suitability of glauconitic rocks in the Upper Cretaceous Bakchar deposit in Western Siberia as alternate potash fertilizer. The K2O content of these glauconitic rocks varies from 2.5 to 4.1wt.%, indicating their good potential as K-fertilizer for agronomic uses. According to the different compositional and textural characteristics, glauconitic rocks can be divided into three types, i.e., glauconitolite, glauconitic sandstone and glauconite-chamosite ooidal ironstone, with glauconite concentrations 58.5wt.%, 25.7wt.% and 24.6wt.%, respectively. The intermediate size fraction of glauconitolite concentrates up to 90.4wt.% of glauconite grains by using wet sieving. Magnetic separation further increases the concentration of glauconite grains for each type of rock samples, especially of glauconitic sandstone. Mixing of glauconitic products with soil increases the germination rate of oat seeds by up to 5.2%, the seedling height records an increase from 0.8% to 18.8%. Both untreated glauconitolite and its granulometric fraction result same rate of growth of oat seedlings. The results of this study suggest that the Bakchar glauconitic deposit can be used as a substitute potash fertilizer, with or without sieving and magnetic separation.

Heat-induced alteration of glauconitic minerals in the Middle Stone Age levels of Blombos Cave, South Africa: Implications for evaluating site structure and burning events

In this paper we conduct geochemical and colourimetric measurements of glauconite grains in micromorphological thin sections from the Middle Stone Age site of Blombos Cave, South Africa, to investigate the formation, internal structure and reworking of heat-exposed cave deposits that are related to prehistoric burning events. Controlled heating experiments were first carried out on glauconite-rich loose sediments and block samples, both of which were collected from the Blombos Cave bedrock. The control samples were then subjected to Fourier transform infrared spectrometry (FTIR), microscopic Fourier transform infrared spectrometry (micro-FTIR) and petrographic-colourimetric analyses. The control experiment shows that glauconitic minerals undergo a gradual and systematic colour change when temperatures reach higher than c. 300–400 °C, primarily due to dehydration and iron oxidation. They also undergo clear structural changes when temperatures reach higher than c. 550 °C due to dehydroxylation and mineral transformation. By assessing the nature and degree of heat-induced optical and molecular alteration in glauconitic minerals, we demonstrate how glauconite grains in thin sections can be classified by the temperature to which they were exposed (20–400 °C, >400 °C, >600 °C and >800 °C). To assess the archaeological relevance of our controlled heating experiment, we applied this glauconite classification scheme to >200 grains found in three micromorphological thin sections of a Middle Stone Age (MSA) combustion feature. These grains were individually geo-referenced within the local coordinate system of Blombos Cave, through a thin-section-based GIS mapping procedure. With improved spatial control, we were able to study both the general distribution of non-altered and heat-altered glauconite grains in their original sedimentary context, as well as to calculate heat distribution models that cover the entire sampled section. This combined geo-chemical, optical and spatio-contextual approach provides insights into more elusive aspects of MSA site structure and burning events, such as heat intensity, burning frequency, temperature distribution, internal hearth structure and post-depositional reworking. The workflow we propose may easily be implemented and adapted to other archaeological contexts and to analogous sedimentary materials that show comparable heat-induced alteration patterns.

Analysis of reworked sediments as a basis of the Palaeogene-Neogene palaeogeography reinterpretation: Case study of the Roztocze region (SE Poland)

Radiometric K/Ar dating of glauconite and nanno- and micropaleontologic analyses of calcareous nannoplankton, foraminifers and dinoflagellates isolated from the Miocene rocks in the Polish part of the Roztocze region, a northeastern part of the fore-bulge of the Carpathian Foreland Basin System - CFBS), SE Poland, reveal that these strata contain numerous microfossils and glauconite grains of the Upper Eocene and Lower Oligocene age. Such occurrences clearly indicate that these materials were redeposited from the Upper Eocene and Lower Oligocene marine rocks that must have originally covered most of the Roztocze and the surrounding area. It is therefore proposed herein that the geographical extent of the boreal, epi-continental basin during the Eocene–Oligocene was much greater than previously considered. Moreover, it appears that this basin was connected with the back-bulge zone of the warm Carpathian Basin (originally a northern part of the Tethys Basin which since Eocene/Oligocene boundary remained isolated as the Paratethys Basin). Hence, it is unlikely that the Roztocze region was uplifted during the Palaeogene as part of the Meta-Carpathian Swell, as it was earlied hypothesized. Instead, the Roztocze Swell formed during the Sarmatian, in the last stage of the development of the fore-bulge structure in the foreland of the up-thrust Carpathian orogenic belt. Multiple redeposition of sediments is the reason that the absolute dating (K/Ar) of glauconite, as well as incomprehensive palaeontological analysis could result in erroneous stratigraphic and palaeogeographic interpretations.

Late Pliocene-Pleistocene environments and glacial history of the northern North Sea

Based on new geochronological (amino acids and Sr-isotopes) and lithological data combined with analyses of 3D seismic data, the Pliocene-Pleistocene development of the central northern North Sea has been investigated. At the start of the Plio-Pleistocene Transition the study area was dominated by a deltaic, shallow marine or tidal depositional environment with sediments mainly sourced from the west. These sand-rich sediments include green glauconitic grains that belong to the Utsira Sand with a local provenance. Directly above the base Quaternary (R2) a 60 m thick layer of mud-rich sediments of glacimarine origin were deposited at a rate of ∼12 cm/ka between ∼2–1.5 Ma and up to 80 cm/ka between 1.5 and 1.2 Ma possibly reflecting glacial ice advancing to the Norwegian coastline. The high rate of deposition in the Early Pleistocene occurred immediately before the initiation of the Norwegian Channel Ice Stream at ∼1.1 Ma. Following this, a large part of the sediment input from Fennoscandia seems to have been directed away from the study area to the shelf break. At the start of the Mid Pleistocene Transition (MPT), subaerial conditions allowed the formation of a >50 km long fluvial channel across the study area draining water from the east to the south west. The earliest evidence of grounded ice in the investigated area comes from mega scale glacial lineations formed during the MPT, at or just after ∼1.2 Ma. Following this, a regional unconformity (R4) was formed by one or more grounded ice advances across the study area possibly during or directly after the MPT and likely marks the boundary between the Early and Mid Pleistocene glacimarine sediments. The Mid to Late Pleistocene stratigraphy is dominated by glacimarine sediments and tills and is associated with multiple generations of tunnel valleys observed within the seismic data. A high shear strength till containing chalk clasts transported from the west and/or south of the study area was likely deposited during MIS6 and may have been more conducive to tunnel valley formation in comparison to lower shear strength tills deposited by later ice advances. A thick till unit overlain by a sand layer in the study area was deposited by grounded ice during the Last Glacial Maximum and subsequent drainage of an ice dammed lake in the southern North Sea during the last deglaciation (MIS2) of the study area. This study shows that much of the Quaternary age sediments within the northern North Sea were deposited relatively rapidly during short periods of time probably leaving significant hiatuses within the stratigraphic record. This finding has implications for previous studies that use a chronological framework assuming a relatively continuous sedimentation rate and record for the Early Pleistocene within the North Sea.

Evolution of a Miocene carbonate shelf (northern Apennines, Italy) revealed through a quantitative compositional study

The evolution of the Miocene San Marino carbonate shelf (Torriana outcrop), developed on the accretionary prism of the northern Apennines, has been interpreted through a stratigraphic and compositional study. Modal analysis allowed to quantify the framework components and to identify four microfacies through which the main steps of the carbonate ecosystem were traced. The healthy phase of the carbonate shelf, dominated by bryozoans and echinoids, originated in a high-energy transgressive setting and evolved during a warm period characterized by a progressive increase of nutrients. The transitional stage is marked by a reduction of carbonate productivity and by terrigenous intermittent pulses associated with bioclast fragmentation. The drowning succession corresponds to deepening upward facies formed by fine-grained hybrid arenites to sandy marls with abundant planktonic foraminifera, glauconitic grains and clay matrix. The demise of the carbonate shelf might have resulted from a combination of regional and global factors that interplayed controlling the detrital input, the nutrient budget and the deepening of the basin. Synsedimentary tectonics triggered subsidence of the basin and enhanced terrigenous discharge. Moreover, the superposition of paleoclimatic and paleoceanographic events (Monterey and Middle Miocene Climate Optimum) could have contributed with the intense weathering and remarkable detrital and nutrients supply.

Genesis, maturity and weathering of some Upper Cretaceous Egyptian glauconites: Mineralogical and geochemical implications

Mineralogical and geochemical studies were carried out on Upper Cretaceous (Cenomanian – Maastrichtian) glauconites from Egypt by means of polarizing microscope, XRD, SEM, microprobe and XRF techniques. Most of the investigated glauconite grains display zoning-like appearance. X-ray diffraction analyses reveal the presence of glauconite, quartz, dolomite, jarosite, goethite and glauconite (illite)-smectite mixed layer minerals. SEM and microprobe investigations revealed that jarosite is present as a weathering product of pyrite especially in Abu Tartur and Wadi Feiran areas. However, goethite was encountered as oxidation product of both pyrite and glauconite. The microprobe analyses of the glauconite grains reflect clearly their low Alumina (<10%) content at the different localities; suggesting therefore their development at depths from 50 m downwards. The Cenomanian glauconites of Wadi Feiran, Saint Paul and Gabal Dist show slight enrichment in K2O content relative to the Campanian – Maastrichtian glauconite of Abu Tartur, indicating more mineralogical maturity.The microprobe analyses also reflect the loss of K and Fe from the glauconite grains. Fe and K can be contributed to aqueous solution media during weathering, leaving aluminous clay minerals in the soil. As result, argillaceous glauconite (illite)-smectite mixed layer, in some cases, is found associating the green pellets of glauconite in many of the investigated samples; most probably produced by weathering of the glauconite grains.Regarding glauconites, Wadi Feiran bulk samples are enriched in TiO2, Al2O3, MgO, Zr, Ce and La, whereas those of Saint Paul exhibit richness in Y and Rb. Gabal Dist samples display appreciable content of Fe2O3(t), K2O, Pb, Zn, Ni, Co, Sc and V whereas the P2O5 and SO3 show their abundance patterns at Abu Tartur locality. These fluctuations could be attributed to their differences in the mineralogical content (pyrite, goethite, and jarosite).The strong correlation between TiO2/Al2O3 and Zr/Al2O3 ratios may reflects mixed origin or reworking of sedimentary rocks from the continental hinterland in all the studied areas.The values of trace elements indices, such as Ni/Co, V/Cr and V/(V + Ni), suggest oxic to suboxic environments. However, some of the chalcophile elements (Pb, Zn, Ni, Co, Cu, Fe and Ga), which are correlated with pyrite and its alteration product (goethite), occur with relatively high concentrations in some studied glauconite beds reflecting reducing and/or suboxic conditions during the precipitation of these beds.

Ancient upwelling record in a phosphate hardground (Tortonian of Menorca, Balearic Islands, Spain)

The Tortonian sedimentary succession of Menorca Island (Balears, Spain) includes two stratigraphic sequences: the lower Tortonian distally-steepened carbonate ramp and the coral reef complex of late Tortonian-early Messinian age. The boundary between the two sequences corresponds to Heterostegina-rich sediments in the western part of Menorca, and to a phosphatic hardground in the eastern part of the island. In the field, the hardground is represented by a dark-brown layer and a rough surface on top of the Tortonian Ramp deposits. Dark phosphate precipitates infill cracks and borings in the underlying limestone to a depth of up to 50 cm. The phosphatic hardground is overlain by planktonic rich wackestone to packstone, which penetrates downward into the fissures, borings, and vugs. This deposit is characterized also by grains of reworked phosphate, glauconite grains, small benthic foraminifers and is followed by tabular beds of bioclastic packstone to wackestone with abundant thin crusts of coralline algae.Based on the Amphistegina tests shapes and red algal assemblage of sediments below and above the hardground, and the lateral correlation with Heterostegina deposits, the bathymetry for the development of the phosphatization is estimated less than 100 m. The limited localization of the phosphatic hardground at the eastern side of the ramp indicates that a dynamic upwelling of deeper and nutrient-enriched waters favored development of a phosphatic hardground. This upwelling episode is representative of the paleoceanographic settings induced by the climate conditions of the Mediterranean area during the Tortonian.