Glauconitic Beds Research Articles

Stratigraphy, palaeogeography and evolution of the lower Nanaimo Group (Cretaceous), Georgia Basin, Canada

AbstractThe Cretaceous lower Nanaimo Group in the Georgia Basin, Canada comprises multiple depositional phases with distinct depocentres that accumulated in a tectonically active forearc basin setting. Basal coarse‐clastic strata are preserved in paleotopographic depressions and grade upwards into coal‐bearing coastal plains and shallow‐marine deposits. Coal‐bearing and shallow‐marine strata grade laterally into and are overlain by, regionally extensive mudstones and turbidites deposited in deep water. A glauconitic sandstone bed within the deep‐water strata is interpreted as a condensed section and underlies a major disconformity that developed during a pause in the deposition of the lower Nanaimo Group. A second major coarse‐clastic succession occurs hundreds of metres above the glauconite bed in the central Georgia Basin and comprises conglomerate, sandstone, mudstone and coal deposited in continental depositional environments. The shift in sedimentation from the northern Georgia Basin to the central Georgia Basin is interpreted to record the emergence of an island (Nanoose Uplift) in the central Georgia Basin that acted as a major sediment source to the adjacent depocentres. The stratigraphic break between the coal‐bearing coarse‐clastic strata in the northern Georgia Basin and the significantly younger coal‐bearing coarse‐clastic strata in the central Georgia Basin indicates that the lower Nanaimo Group was deposited in distinct depocentres. Between the older, coarse‐clastic strata in the north and younger, coarse‐clastic strata in the central Georgia Basin, we hypothesize that a major deepwater canyon system (Qualicum Canyon) existed and transferred sediment from the semi‐restricted Georgia Basin to the Pacific Ocean to the west. Development of the Qualicum Canyon and exposure of the Nanoose Uplift during deposition of the younger, central coarse‐clastic strata suggests that syntectonic activity drove basin uplift and erosion and this occurred throughout the deposition of the lower Nanaimo Group.

New insights on the stratigraphy of Tobruq-Burdi area- Marmarica, NE Libya

The stratigraphy of the Marmarica region in the eastern region of Libya (called Tobruq-Burdi), the nomenclature contradiction in stratigraphy has been reviewed. Three surface exposures, Wadi al Hash, Wadi al Shaigh at Tobruq area and Wadi al Rahibat Burdi area have been measured, sampled and analyzed using both the lithology and the fossil assemblages. Previous works in the area have been revised to sort out the contradiction on the stratigraphy. A disconformity surface with different time interval have been documented at two localities. The first location is a well-known transgressive event (i.e. glauconitic bed) which was recognized at the basal part of the Oligo-Miocene Al Faidiyah Formation delineating the disconformity surface separating the Oligo-Miocene Al Faidiyah Formation from the underlying Middle Eocene Darnah Formation at Wadi al Hash and Wadi Al Shaigh sections. However, the second location exhibits an angular unconformity surface separating the Lower Oligocene algal limestone of Al Bayda Formation from the underneath Campanian Al Majahir Formation at Wadi al Rahib section in Burdi area.
 Meanwhile, the upper two formations the Oligo-Miocene Al Faidiyah Formation and the overlying Middle Miocene Al Gaghbub Formation in the study area are separated from each other by disconformity of short interval time. The area was tectonically stable with extensive spatial distribution with some thickness variation in response to the paleorelief of the area of study. On the basis of foraminiferal assemblages, the Darnah Formation is Middle Eocene, Al Faidiyah Formation is Late Oligocene, Al Gaghbub Formation is Middle Miocene at Tobruq and Burdi area. The term Al Khowaymat Formation is replaced by Darnah Formation for (the Lower Member of the so-called Al Kowaymat) and Al Faidiyah Formation for (the Upper Member of the so-called Al Kowaymat) at the studied sections in Tobruq area. Similarly, the term Lower Member of Al Khowaymat Formation is replaced by Al Majahir Formation at Wadi al Rahib section in the Burdi area.

Petrography and Lithogeochemistry of the Uppermost Middle Jurassic–Lowermost Lower Cretaceous Strata in the Lower Reaches of the Anabar River (East Siberia, Arctic)

Abstract —Based on the analysis of the petrographic and lithogeochemical features of the Middle Jurassic–Lower Cretaceous strata in the lower reaches of the Anabar River, we have studied the regularities of changes in the composition of the upper parts of the Yuryung-Tumus and Sodiemykha formations and the lower part of the Buolkalakh Formation. It has been established that the silt–sandy rocks of the first and basal beds of the second formation are graywacke arkoses and essentially feldspathic varieties, and most of the Sodiemykha Formation is composed of quartz–feldspathic and scarcer feldspar–quartz graywackes. A chemical classification of the rocks was made; most of them were assigned to normosiallites. The rocks of the marker beds, namely, the Fe-containing deposits of the Sodiemykha Formation, the basal glauconite bed of the Buolkalakh Formation, and the overlying clay bed, were classified as hypohydrolysates. All the studied deposits are of low sedimentary maturity, with essentially petrogenic clastic material. These are predominantly igneous rocks of intermediate and, less, felsic composition. The provenances were characterized by moderate chemical weathering. In the periods of the formation of the marker beds, chemical weathering intensified, and the amount of mafic and, partly, ultramafic rocks increased. The established changes in the composition of the parental strata are observed in the Middle Jurassic–Lower Cretaceous deposits of the entire considered petromineralogical province, which permits them to be used for correlation.

Triassic fish faunas from Miedary (Upper Silesia, Poland) and their implications for understanding paleosalinity

We describe two new fish-dominated faunas from the Middle Triassic (Ladinian) Miedary site, Upper Silesia, Poland, and present a comparative analysis of Middle-to-Late Triassic vertebrate assemblages from the Germanic Basin, in order to explore the influence of salinity on faunal composition. The composition of the assemblage from dolomite beds at Miedary is similar to those from the Muschalkalk facies, whereas the assemblage from glauconite beds appears to be the first brackish vertebrate assemblage of the Serrolepis lake-type recognized from the eastern Germanic Basin. Comparative analysis of all sites, using hierarchical clustering, nonmetric multidimensional scaling, and principal component approaches, revealed the existence of vertebrate taxa associated withfreshwater, brackish and marine conditions, as well as euryhaline taxa with wide salinity preferences. Moreover, it confirms the brackish nature of Serrolepis -bearing assemblages, and suggests that Serrolepis suevicus is a brackish specialist, indicative of oligohaline to miohaline paleosalinities. The Middle-Late Triassic vertebrate faunas appear dominated by stenohaline taxa, with a conspicuous separation of species living in the freshwater and marine conditions. The euryhaline taxa are rare, and comprise Acrodus lateralis , Eusauropterygia, Lissodus nodosus , and Saurichthyiformes. • Two new fish assemblages from the Middle Triassic of Europe are described. • Paleoenvironmental signature of Serrolepis-lake assemblages is confirmed. • There is noticeable relationship between aquatic assemblage composition and paleosalinity. • Preferred salinity ranges for various Mid-Late Triassic vertebrates are proposed. • Sufficient sampling and quantitative data are crucial for comparative studies on paleosalinity.

Petrographical and geochemical constraints on carbonate diagenesis in an epeiric platform deposit: Late Cretaceous Bagh Group in central India

A combined facies, petrography and isotope geochemistry reveal an extensive pedogenic alteration of platform carbonate deposits of the Upper Cretaceous Bagh Group in the western Narmada basin in central India. The highly fossiliferous carbonate sequence of the Bagh Group consists of two formations, the Nodular Limestone at the base, and the Bryozoan Limestone Formation at top. The Nodular Limestone Formation comprises primarily of mudstone and wackestone, with relics of bioclasts such as gastropods, echinoderms, molluscs, forams and calcispheres, reflecting a low-energy supratidal to upper intertidal environment of deposition. Prolonged pedogenesis leads to pervasive micritization, brecciation, desiccation and recrystallization. The overlying Bryozoan Limestone, dominated by packstone and planar laminated rudstone with bryozoans, gastropods, echinoderms/echinoid spines, and molluscs, indicates deposition within the lower intertidal environment with moderately high-energy conditions. Abundant meniscus cement and biomolds suggest meteoric vadose diagenetic modification, whereas, intense secondary micritization of sediments indicates prolonged calichification. The δ13C and δ18O ratios of both Nodular Limestone and Bryozoan Limestone formations are depleted than the normal marine values, indicating an extensive diagenetic resetting of the carbonates. While the meteoric cement is depleted in both δ13C and δ18O ratio, the burial cement shows a decrease of δ18O at constant δ13C. The pedogenetic horizons within the Bagh carbonates bear subtle evidence of subaerial exposures within the overall transgressive Bagh Group. A glauconite bed at the upper part of the Bryozoan Limestone Formation marks the top part of the transgressive deposit.

Parvamussium fallax (KOROBKOV) a Csabrendek - Gyepükaján környéki Padragi Márgában

A Parvamussium fallax (KOROBKOV) faj Csabrendek-Gyepükaján környékén (Déli-Bakony, Magyarország) mélyült fúrások által harántolt Padragi Márga Formáció alsó, glaukonitos márga és mészmárga rétegekből felépülő Csabrendeki Márga Tagozatában fordul elő. Az irodalmi adatok szerint felső eocénben és alsó oligocénben egyaránt megtalálható faj e területen a középső eocén felső részét (bartoni emelet) képviselő rétegekben található. Rétegtani elterjedése tehát nagyobb az eddig ismerteknél, ezért kevésbé alkalmas szűk rétegtani intervallum kijelölésére, viszont környezetjelző szerepet játszik. A rétegsorban elfoglalt helye, azaz sekély- és közép-szublitorális molluszka féléket tartalmazó, glaukonitban gazdag rétegek felett és plankton-foraminiferákban gazdag pelagikus rétegek alatt, glaukonitban szegényebb márgákban, mészmárgákban való előfordulása, a faj életterét a mélyszublitorális övben, a self és a medence lejtő határán jelöli ki. A dolgozat feltárja az alak magyar vonatkozásait. A fajt elsőként HOFMANN (1873) ábrázolta Pecten bronni MAYER név alatt, első leírását LŐRENTHEY (1911) készítette el, azonban egyikük sem ismerte fel a Budai hegységi példányoknak a Pecten bronni MAYER alaktól eltérő jellegét. Azt KOROBKOV(1937) vonta be az általa felállított Variamussium fallax KOROBKOV új fajba. Az alak e néven vált ismertté a rétegtani irodalomban, de a taxonomusok szerint a Variamussium nemzetségnév a Parvamussium junior szinonímája, ezért a faj helyes megnevezése: Parvamussium fallax (KOROBKOV).

Unusual seawater composition of the Late Cretaceous Tethys imprinted in glauconite of Narmada basin, central India

AbstractA detailed investigation of a glauconite bed within the Late Cretaceous Bryozoan Limestone Formation of the Bagh Group in central India, as well as the study of existing records, reveals the existence of a ‘glauconitic sea’ along the margins of the Palaeo-Tethys Ocean during the Late Cretaceous Epoch. The authigenic green mineral formed abundantly on shallow seafloors unlike in its modern, deep-sea counterpart. We present an integrated petrographical, geochemical and mineralogical investigation of the glauconite within Late Cretaceous transgressive deposits to highlight its unique geochemistry with moderate Fe2O3 and high Al2O3, SiO2, MgO as well as K2O contents. X-ray diffractional parameters identify the ‘evolved to high evolved’ nature of the glauconite while Mössbauer spectroscopic study reveals the dominance of Fe3+ compared to Fe2+ in the atomic structure. The rare earth elements (REE) pattern of glauconite reveals moderate light-REE/heavy-REE (LREE/HREE) fractionation and weak negative Eu anomaly. The Ce anomaly of the glauconite indicates a sub-oxic diagenetic condition. We propose that Late Cretaceous glauconites formed within a shallow marine depositional setting across the Tethyan belt because of enhanced supply of K, Si, Al, Fe, Mg cations through continental weathering under the extant greenhouse climate.

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.

Mineralogy and Geochemistry of the Main Glauconite Bed in the Middle Eocene of Texas: Paleoenvironmental Implications for the Verdine Facies

The Main Glauconite Bed (MGB) is a pelleted greensand located at Stone City Bluff on the south bank of the Brazos River in Burleson County, Texas. It was deposited during the Middle Eocene regional transgression on the Texas Gulf Coastal Plain. Stratigraphically it lies in the upper Stone City Member, Crockett Formation, Claiborne Group. Its mineralogy and geochemistry were examined in detail, and verdine facies minerals, predominantly odinite, were identified. Few glauconitic minerals were found in the green pelleted sediments of the MGB. Without detailed mineralogical work, glaucony facies minerals and verdine facies minerals are easily mistaken for one another. Their distinction has value in assessing paleoenvironments. In this study, several analytical techniques were employed to assess the mineralogy. X-ray diffraction of oriented and un-oriented clay samples indicated a clay mixture dominated by 7 and 14Å diffraction peaks. Unit cell calculations from XRD data for MGB pellets match the odinite-1M data base. Electron microprobe analyses (EMPA) from the average of 31 data points from clay pellets accompanied with Mössbauer analyses were used to calculate the structural formula which is that of odinite: Fe3+ 0.89 Mg0.45 Al0.67 Fe2+ 0.30 Ti0.01 Mn0.01) Σ = 2.33 (Si1.77 Al0.23) O5.00 (OH)4.00. QEMSCAN (Quantitative Evaluation of Minerals by Scanning Electron Microscopy) data provided mineral maps of quantitative proportions of the constituent clays. The verdine facies is a clay mineral facies associated with shallow marine shelf and lagoonal environments at tropical latitudes with iron influx from nearby runoff. Its depositional environment is well documented in modern nearshore locations. Recognition of verdine facies clays as the dominant constituent of the MGB clay pellets, rather than glaucony facies clays, allows for a more precise assessment of paleoenvironmental conditions.

In search of the Latest Danian Event in a paleobathymetric transect off Kasserine Island, north-central Tunisia

Danian (lower Paleocene) sequences in north-central Tunisia are dominantly composed of marls and shales but a conspicuous, indurated glauconite-bearing marker bed is associated with the P3a–P3b transition. This glauconite bed is considered to correlate with the Latest Danian Event (LDE) described from the Nile Basin in Egypt, with the ‘top Chron C27n event’ (Atlantic and Pacific Oceans) and with the ‘CIE-DS1’ (Zumaia, Spain). The LDE is thought to reflect a short period of global warming, similar to the Paleocene Eocene Thermal Maximum, but of lesser magnitude. The presence of a glauconitic bed at the P3a/P3b transition in Tunisia suggests that the sequence is condensed, which is confirmed by planktic foraminifer and nannofossil biostratigraphy, and by the absence of the typical LDE beds found in most Egyptian sections. Benthic foraminiferal assemblages were quantitatively analyzed in three sections in north-central Tunisia (Sidi Nasseur, Garn Halfaya, Elles) in order to characterize the paleoenvironmental evolution during the late Danian and compare this with sections in Egypt. The benthic foraminiferal assemblages indicate that the Tunisian sections were located along a depth- and a paleoenvironmental gradient on the shelf north of Kasserine Island. The reconstructed depth range is comparable with sections in Egypt, and encompasses middle neritic (Sidi Nasseur section) to shallow upper bathyal depths (Elles section, with up to 16% Gavelinella beccariiformis below the P3a/P3b). Like in Egypt, assemblage shifts across the P3a/P3b subzonal transition indicate shallowing and a transition to a more eutrophic paleoenvironment, characterized by relatively high abundances of buliminids and Stainforthia sp. The δ13C and δ18O records generated on well-preserved specimens of the ostracode species Bairdia failed to demonstrate the presence of the carbon isotope excursion (CIE) associated with the LDE at the base of Subzone P3b. A condensed section or a hiatus associated with the glauconite bed would explain why the CIE is not recorded in the Tunisian sections.

Non-pelletal glauconite from the Campanian Qusseir Formation, Egypt: Implication for glauconitization

Glauconitization processes proposed in the literatures include the “layer lattice” theory in which glauconite formed through K uptake by a detrital smectite precursor and the “neoformation theory” that does not require a smectite-like precursor.The non pelletal glauconite bed in the uppermost part of the Campanian Qusseir Formation at the Abu Tartur area and the underlying smectite-rich beds provided a potential example for the glauconitization process. The glauconite occurs as fine (clayey), moderately hard, and homogeneous bed ranges in thickness from 2 to 3m. Under the optical microscope, glauconite occurs in a unique morphology as very fine green clayey matrix, which differs from the typical pelletal shape of many glauconites. Under the scanning electron microscope, it appears as dense, uniform, and very fine flakes that are composed of Si, Al, Fe, and K. X-ray diffraction analysis of both bulk samples and clay fractions indicates that the glauconite bed is composed entirely of glauconite. Geochemical analysis suggested that the investigated glauconites belong to the 2nd stage of the maturity scale (i.e. moderate maturity); or they can be alternatively ranked as evolved. Chondrite-normalized REE patterns exhibit LREE enrichment relative to HREE ((La/Yb)N ratios vary from 5 to 8) and slightly negative Eu anomalies (Eu/Eu* from 0.7 to 0.8).Clay beds that underlie the glauconite bed are composed of two types of smectites; smectite of low K2O and Fe2O3 contents and smectite of high K2O and Fe2O3 contents. Smectite of low K2O and Fe2O3 contents is considered in this study as the initial precursor of glauconite, while smectite of high K2O and Fe2O3 represents the transitional phase between smectite and glauconite. This, in turns, supports the “layer lattice” theory in which glauconite formed by K diffusion to a detrital smectite precursor from the sea-water due to transgression. Absence of mixed-layer minerals suggests that the diffusion process was active and continuous until reaction completion was reached, i.e. formation of glauconite. Maturity and REE patterns suggest the possible formation of the studied glauconite probably at shelf environment at approximately 100m water depth. The occurrence of glauconite indicates a marine invasion of the upper part of the Qusseir Formation, which was considered previously as non-marine sediments.

Sedimentology and sequence stratigraphy of a pronounced Early Ordovician sea-level fall on Baltica — The Bjørkåsholmen Formation in Norway and Sweden

The Bjørkåsholmen Formation consists of interbedded carbonates, shales, and glauconitic beds and is characterized by heavy bioturbation and few preserved sedimentary structures. The unit shows five facies shale, glauconitic packstone, and three predominantly mud-dominated carbonate facies. Carbonates and shales are arranged in small-scale deepening-upward cycles. A minimum of fourteen of these small-scale cycles are recognized in the Bjørkåsholmen Formation. They are arranged in stacks of 3 to 5, forming a total of four medium-scale cycles separated by decimeter-thick shale units. Based on the predominance of mud-rich facies the succession is interpreted to have been deposited in an overall tranquil setting during one mayor sea-level fall and subsequent initial rise of third order. Time-estimates suggest that the 14 small-scale cycles fall into the Milankovitch band of precessional forcing, and the overriding medium-scale cycles likely represent short eccentricity. The sequence stratigraphic interpretation shows that the Bjørkåsholmen Formation is characterized by falling stage, lowstand and initial transgressive systems tracts. Consequently, the contact between the Bjørkåsholmen and the underlying Alum Shale Formation represents the basal surface of forced regression. The maximum regressive surface is defined by a hiatus in the Öland sections and by shallow-marine packstones within mud-rich distal ramp carbonates in Norway. The top of the Bjørkåsholmen Formation represents a flooding surface at the base of the transgressive systems tract. A comparison of time-equivalent successions worldwide suggests that the Bjørkåsholmen Formation represents a tectonically-enhanced lowstand with two overriding short-term Milankovitch eustatic signals. Although deposition of the Bjørkåsholmen Formation coincides with the initiation of a foreland basin in the Caledonides of Norway it remains unclear how these tectonic movements may have lead to the widespread Bjørkåsholmen lowstand during the Early Ordovician. It is suggested in this study that a combination of compressional forces from Avalonia and the Caledonian margin may have acted in concert to produce an uplift of larger parts of the Baltica plate for a time-span of approximately 0.5 Myr.

Preliminary assessment of spent glauconite bed usage possibilities as a material to lightweight aggregate production.

The presented work has shown an application of spent glauconite bed after purifi cation of wastewater for production of lightweight expanded clay aggregates. Sewage, from which it was removed Zn ions, came from technological line (zinc-works) of Communication Equipment Factory „PZL” Świdnik. Spent glauconite bed was used as an additive in lightweight aggregate production which was obtained using plastic method by sintering, at temperature 1140ºC and 1200 ºC, of spent glauconite amouts 10, 15, 20 and 25% wt. with clays from open-cast mine „Budy Mszczonowskie”. The presence of the mineral improves sinter texture, increases porosity and contributes to formation of glassy layer on the surface of the aggregates. Tests of zinc elution from lightweight aggregate samples has shown very low mobility of zinc ions. Content of zinc in water extracts obtained from lightweight aggregate is defi nitely lower than zinc concentration permitted for sewage discharge to water or soil, means that spent material is not offensive for the environment as it can be used as a high quality building product.

Biostratigraphy of the Danian/Selandian transition in the southern Tethys. Special reference to the Lowest Occurrence of planktic foraminifera Igorina albeari

The P3a/P3b subzonal boundary is delineated by the lowest occurrence of Igorina albeari. Using literature, identification of the first representatives of I. albeari appeared to be very confusing. In this study descriptions of I. albeari are compared and a consistent definition is proposed. Igorinid specimens with an incipient keel are considered to be I. albeari. Flattening of the last chambers and the fusion of muricae on the peripheral margin may indicate such a slight keel. This keel enables an unambiguous distinction between I. pusilla and the first form of I. albeari and is in keeping with the original descriptions without introducing an intermediate species. In the southern Tethys, the lowest occurrence of I. albeari occurs just prior to the pinkish-brown marl bed in Egypt and immediately overlies the glauconitic bed in Tunisia. Furthermore, the NTp7A/NTp7B subzonal boundary, delineated by the lowest occurrence of Chiasmolithus edentulus, is in close correlation with these marker beds. In Egypt C. edentulus appears 1 m below the entry of I. albeari, whereas in Tunisia they coappear. This implies significant erosion at the glauconitic bed in the studied parts of the Tunisian Trough and a more complete succession at the dark-brown marl bed in the Nile Valley. These marker beds can also be correlated to a level of minor lithologic change in the upper part of the Danian Limestone Formation in the Zumaia section through the lowest occurrence of Chiasmolithus edentulus. The distinct lithologic change in Zumaia, from the Danian Limestone to the Itzurun Formation, however, appears to be ~600 kyr younger than what we now call upper Danian event beds, in Tunisia and Egypt.

Sedimentology and architecture of sharp-based tidal sandstones in the upper Marambio Group, Maastrichtian of Antarctica

At Snow Hill and Seymour islands, northeastern Antarctic Peninsula, the early Maastrichtian part of the Marambio Group consists in ascending stratigraphic order of a) fossiliferous mudstone and sandstone of the Snow Hill Island Formation (> 140 m thick), b) glauconitic beds of the Haslum Crag Sandstone (ca. 200 m thick), and c) the mudstone-rich basal López de Bertodano Formation (ca. 400 m thick). The study of fourteen sedimentary sections located along the depositional strike reveals complex arrangements of facies associations and stratal architecture for these units. The Snow Hill Island Formation consists of coarsening and thickening upward successions, 3–7 m thick, of interbedded mudstone and sandstone recording prograding deltaic lobes. Above a marked unconformity, the Haslum Crag Sandstone, bioturbated glauconitic sandstone and mudstone with inclined heterolithic stratification, records the incision, migration, and filling of relatively large and deep subtidal channels. Deeply incised into the Haslum Crag Sandstone, the López de Bertodano Formation includes transgressive estuarine and shallow marine deposits that fill a previous fluvially and/or tidally scoured depression. The Haslum Crag Sandstone consists of forced regressive deposits formed during relative sea-level falls, and documents a rare case of sharp-based, tide-influenced sandstone encased in marine and estuarine mudstone. The main differences between the Haslum Crag Sandstone and other forced regressive, wave-influenced sharp-based sandstones are twofold: a) it records basal erosion by tidal processes — an erosional feature not as yet fully documented in forced regressions, and b) it records a rare case of tide-influenced deposits originating during overall regressive conditions. The great thicknesses of tide-influenced forced regressive deposits (Haslum Crag Sandstone) and the transgressive, estuarine deposits (López de Bertodano Formation) suggest the occurrence of several high-frequency sea-level changes, probably driven by tectonic processes.

Danian/Selandian boundary stratigraphy, paleoenvironment and Ostracoda from Sidi Nasseur, Tunisia

Two detailed records (NSF and 05NSC, Sidi Nasseur, Tunisia) across the Danian/Selandian (D/S) boundary were investigated for their micropaleontological content. Calcareous nannofossils and planktic foraminifera provided a biostratigraphic framework. The interval spans part of planktic foraminiferal Zone P2, Subzone P3a and part of Subzone P3b. This corresponds to calcareous nannoplankton Zone NP4. Using a more detailed nannofossil zonation the studied section spans part of Zone NTp6, Zone NTp7a and part of NTp7b. Quantitative ostracod and qualitative benthic foraminiferal data were used to characterize environmental changes across the D/S boundary. The two subsections have yielded a total of 50 ostracod taxa. The ostracod assemblage of the entire section belongs to the Southern Tethyan Type showing subtle but distinct changes up section. Based on statistical analysis of the quantitative ostracod data, faunal changes at a glauconitic maker bed (P3a/P3b boundary) were demonstrated. The local Reticulina proteros assemblage, with the typical species R. proteros, Oertliella vesiculosa and Cytheroptheron lekefense, is gradually replaced by the Protobuntonia nakkadii assemblage, with the typical species Cristaeleberis arabii, Xestoleberis tunisiensis, Cytheropteron sp. and P. nakkadii, across the glauconitic bed. The benthic foraminifera also demonstrated distinct changes at this marker bed. The changes in ostracods and foraminifera are related to changes in paleoproductivity and an overall relative sea-level fall. The lithological and faunal changes at the P3a/P3b zone boundary within the Sidi Nasseur sections seem to correspond to the D/S boundary in the type region in Danmark and are characterized by a significant hiatus, yielding this section not suitable as a GSSP candidate for this boundary.

勇払油・ガス田における上部中新統〜鮮新統の珪藻化石層序

Diatom biostratigraphy was examined for the upper Miocene to Pliocene sequence distributed in the Yufutsu oil and gas field located in southern central Hokkaido, Japan.The Denticulopsis praedimorpha and Denticulopsis dimorpha Zones were recognized in thin volcanic reworked sediment with glauconite, which overlies just above the Takinoue volcanics oil reservoir. The result indicates that the condensed glauconite bed had been formed for a long time, from the end of Takinoue volcanic activity through the D. dimorpha Zone.Siliceous sediments overlaying the glauconite bed are correlated to the upper part of the Thalassionema schraderi and Rouxia californica Zones. The siliceous sediment is unconformably covered by sandy sediment. Its basal part is correlated to the Neodenticula koizumii-Neodenticula kamtschatica Zone. The N. kamtschatica Zone is completely missing in the field whereas it is thickly developed at the Yufutsu-oki wells located about 20km offshore.Based on the diatom biostratigraphy and interpretation of seismic profiles, the condensed glauconite bed is correlated to the middle to upper Miocene Fureoi and Karumai Formations. The interval of "the Biratori and Karumai Formations" by several authors in the field is correlative to the upper Miocene Nina Formation typically distributed along the Sarugawa river near the Biratori city. "The Nina Formation and Quaternary System" in the field is correlated to upper Pliocene and Quaternary.

Trying to understand Alpine sediments—before 1950

Most Alpine geologists, before and after the 1893–1902 breakthrough of the nappe theory, paid surprisingly little attention to sedimentological phenomena. They were preoccupied with stratigraphic and especially tectonic problems. The Alpine concept of “geosyncline” differed in several ways from the original one. In 1894, Marcel Bertrand suggested a fourfold division of “complexes” (informal lithostratigraphic assemblages) among the sediments of the Alps and of older mountain chains. For the Alps, his classification may be expanded to comprise: I, Late Variscan detritals; II, pre-rift platform sediments; III, syn-rift deposits; IV, post-rift platform and basin sediments; V, starved deep-sea formations on oceanic or thinned continental crust; VI, Bündnerschiefer or Schistes lustrés; VII, Flysch; and VIII, Molasse. The last named is not discussed here. On the European (Helvetic) margin, the processes giving rise to shallowing-upward sequences of condensed glauconite beds, shales and limestones (complex IV) were discussed for a long time. The work of Arnold Heim is particularly instructive. Gustav Steinmann was one of the first to recognize the deep-sea origin of certain rocks, especially radiolarian cherts. The controversy on the bathymetry of the Alpine seas during the oceanic and post-oceanic stages (complexes V–VII) went on until about 1950. Since 1916, the seas and islands around eastern Indonesia were proposed as analogues to the Late Mesozoic paleogeographic pattern of the Alps. Two 18th century scientists deserve a special mention: Moritz Anton Kappeler (M.A. Cappellerius, 1767) provided an actualistic interpretation of ripple marks on steep-standing sandstones, and Johann Jacob Scheuchzer (1718) understood the importance of graded bedding, which he attributed to the action of the Deluge.

Paleocommunity Reconstruction from Shell Beds: A Case Study from the Main Glauconite Bed, Eocene, Texas

Abstract The Main Glauconite Bed (MGB), near the top of the Eocene Stone City Member (Crocket Formation), Texas, has been considered to contain a typical local paleocommunity (parautochthonous assemblage formed within a stable habitat). Microstratigraphic analysis, however, reveals a complex sedimentologic and taphonomic history for the MGB, a unit that is 1.7–1.9 m thick and consists of three intercalated small-scale facies interpreted to represent differing modes of deposition. The primary autochthonous inner-shelf sediments are dark glauconitic clay-silts with a matrix-supported polytaxic fossil assemblage. Recurrent storms produced thin (few mm to cm) layers of mostly simple, bioclast-supported, polytaxic shell concentrations. These distal tempestites occur mainly as small-scale lenses and as a few beds and pods, associated with glauconite-pellets, terrigenous sands, and scarce sedimentary structures. Subsequent burrowing destroyed most skeletal concentrations and formed patches of fossils, glauconite...

Abstract: Integrated Paleoecology and Marine Vertebrate Fauna of the Stone City Formation (Middle Eocene), Brazos River Section, Texas&amp;nbsp;

ABSTRACT Abundant marine vertebrate faunas, including sharks, rays, teleosts, and reptiles, have been collected from two horizons in the Middle Eocene (Claiborne) Stone City Formation of southeast Texas. Extensive collecting, both surface and bulk, and recent advances, especially in the study of otoliths and foraminifera, provide for additional evaluation of paleoecological parameters. Otolith-based teleosts are dominated by neritic taxa such as sciaenids and ophidiids, while skeletal-based teleosts include catfish, barracuda, mackerel, and gar. Selachians include sand, tiger, and catsharks as well as rays and sawfish. Least common are reptiles, represented by crocodiles and turtles. Vertebrate diversity is 50 taxa, the richest marine fauna yet recorded from the Gulf Coast Middle Eocene. Vertebrates were collected from the top of the Main Glauconite bed and a thin lag zone three m below. The lower fauna (Assemblage A) is rich in tiger and sand sharks, eagle rays, plus estuarine elements, such as catfish, sawfish, and softshell turtle. The mixture of estuarine vertebrates with abundant marine mollusks suggests a possible tidal channel emptying into nearshore marine. The upper fauna (Assemblage B) is dominated by a rich, moderately diverse fish fauna with scarce rays and sharks. An assemblage with sciaenids, ophidiids, and myripristids with abundant, diverse mollusks, especially infaunal pelecypods, suggests a fully marine but nearshore setting of 25 m or less. Microfauna includes 33 benthic foraminifera and 15 ostracode species. The shallow nature of this assemblage, plus the lack of planktonic foraminifera, indicatesan absence of open ocean currents. Macrofaunal and microfaunal paleoecology supports the shallow neritic to estuarine conditions indicated by vertebrate parameters. The Main Glauconite bed was deposited in an open marine bay or lagoon which was separated from ocean currents by some barrier, possibly an offshore marine sandbar complex.