Foraminifera from jurassic sediments of Keera Dome, Kutch

A foraminiferal assemblage comprising 30 species dominated by the family Vaginulinidae is recovered from the Chari Formation exposed at Keera Dome, Kutch. The paper presents a systematic account of eight species, reported for the first time form the Indian region. Preliminary interpretations regarding age and palaeoenvironment are drawn on the basis of the recovered foraminiferal assemblage. The assemblage supports a Callovian to Oxfordian age for the studied sequence. A near shore, open marine environment ranging from mid to outer shelf is interpreted on the basis of the foraminiferal assemblage.     

Jurassic foraminifera from Jajiya Member,Jaisalmer Formation,Western Rajasthan

The Jajiya Member of Jaisalmer Formation yielded a foraminiferal assemblage comprising twenty-three species dominated by the family Vaginulinidae. An Oxfordian age is assigned to the foraminiferal assemblage based on the record of some characteristic Oxfordian species reported from different parts of the world. The foraminiferal assemblage suggests an open marine shelf environment of deposition.     

Paleoenvironmental and biostratigraphic significance of uvigerinids and other foraminifera from the Bhuban Formation,Assam-Arakan Basin,Mizoram

Planktic and benthic foraminifera including uvigerinids are documented from the Upper Bhuban Formation, exposed at Thingdawl village, Kolasib district, Mizoram. The foraminiferal assemblage is poorly preserved and consists of index fossils useful for precise biochronology and interpretation of the depositional environment. A total of ten benthic and six planktic foraminiferal species are described. Six species belong to the genus Uvigerina, four to Ammonia, one species each of Globorotalia, Globigerinoides, Clavatorella, Praeorbulina and two species of the genus Orbulina. Based on lithological and foraminiferal assemblage, middle neritic to upper part of outer neritic paleobathymetry is inferred for the deposition of this part of the Upper Bhuban Formation. The foraminiferal assemblage suggests late Early Miocene to early Middle Miocene, (∼16 Ma) equivalent to planktic foraminiferal zones N8-N9 for the Upper Bhuban Formation.     

Stratigraphy and paleobathymetric interpretation of the Cretaceous Karai shale formation of Uttatur Group, TamilNadu, India

The Karai shale Formation of the Uttatur Group is exposed in a bad land area at the western margin of the Cauvery Basin. This shale has been investigated based on foraminiferal fauna and clay minerals. The foraminiferal assemblages obtained contain predominantly calcareous benthic foraminifera, rare planktic and arenaceous foraminifera. The planktic foraminiferal index taxa Planomalina buxtorfi, Rotalipora reicheli, Praeglobotruncana stephani, and Hedbergella portsdownensis suggest the late Albian to middle Turonian age. The benthic assemblage dominated by Lenticulina, Gavelinella, Osangularia and Quadrimorphina, suggests an outer neritic (100–200 m) environment. The clay mineral content dominated by kaolinite-illite-montmorillonite indicates that the Karai shale was formed from weathering of igneous rocks.     

Glauconites from the Late Palaeocene — Early Eocene Naredi Formation,western Kutch and their genetic implications

Glauconitic minerals are considered as one of the valuable input parameters in sequence stratigraphic analysis of a basin. In the present study glauconitic minerals are reported from subtidal green shale facies in the lower part of the Late Paleocene-Early Eocene Naredi Formation of western Kutch. On the basis of the foraminiferal assemblage the glauconite bearing beds are interpreted to have formed in a mid shelf depositional settings of an unstable marine conditions. XRD studies confirm the glauconite mineralogy of the green pellets and provide an estimation of glauconite maturity. Textural attributes of the glauconites confirm their derivation by different degrees of alteration of precursor feldspar grains. Because of the authigenic origin and autochthonous nature, these glauconites hold promise for understanding sequence stratigraphy of the Palaeogene succession of the western Kutch.     

Upper Campanian-lower Maastrichtian planktonic foraminifers from Govorov Guyot (Magellan Seamounts,Pacific Ocean)

The planktonic foraminiferal assemblage from foraminiferal limestone (ooze) dredged from the summit of one of guyots in the Magellan Seamount system of the Pacific is dominated by one-keeled species belonging to the genus Globotruncanita. The taxonomic composition of the assemblage correlates host rocks with the upper Campanian-lower Maastrichtian. One species and one subspecies are described as new taxa.     

南海北部近6 Ma以来中层水体演化的底栖有孔虫证据

本文对南海北部陆坡SH7B孔底栖有孔虫群落结构组成及壳体氧碳同位素值变化特征进行研究,旨在了解该区晚中新世以来的中层水体演化历史。利用因子和聚类分析对该钻孔128个样品中的35个底栖有孔虫优势属种的相对百分含量数据进行统计分析,识别出4个组合:Globocassidulina subglobosa-Stilostomella spp.（Gs-St）,Chilostomella mediterranensis-Globobulimina spp. (Cm-Gl),Hoglundina elegans-Pyrgo spp. (He-Py),Melonis affinis-Pyrgo spp. (Ma-Py)。晚中新世晚期至上新世早期（5.8~2.8 Ma）相对高海平面温暖期,SH7B孔底栖有孔虫为相对稳定的Gs-St组合,反映了低到中等营养物质供给的低氧水体环境。其中5.8~3.79 Ma底栖有孔虫壳体碳同位素偏负和强烈的碳酸盐溶解现象在全球其他海区均有发现,指示当时南海北部陆坡底层水体低氧环境可能受到因全球大洋环流格局变化影响的太平洋偏腐蚀性的缺氧中层水体影响。3.79~2.8 Ma底栖有孔虫丰度和喜氧类表生种含量逐渐增加,指示水体流通性趋于增强,水体氧含量稍有增加。晚上新世2.4 Ma以来,底栖有孔虫组合与氧碳同位素值波动变化频繁,反映了中等到高表层输出生产力的富氧到缺氧中层水体环境,南海北部陆坡底栖有孔虫的分布主要受陆源有机质输入量的多寡和南海中深层水体的循环状况共同控制。     

Agglutinated foraminifera from the Campanian-Maastrichtian Kiseiba Formation in the Kurkur area,Egypt

The upper Campanian to upper Maastrichtian sedimentary sequence of the Kiseiba Formation in south Western Desert is sampled and described in two surface sections (Sinn El Kaddab and Wadi Abu Siyal). Forty-four agglutinated foraminiferal species are identified from 42 samples in the studied succession. The benthic foraminiferal assemblages are dominated by agglutinated foraminifera which comprise more than 90% of the assemblage. The agglutinated foraminifera are subdivided into five morphogroups (A, B, C, D, E) according to shell architecture, integrated with the supposed microhabitat and feeding strategy. The foraminiferal assemblage is assigned to mixohaline shallow water environments. These assemblages with Ammoastuta megacribrostomoides and Ammotium bartheli suggest lagoonal environments with considerably reduced salinity in warm climates and high runoff for the late Campanian-Maastrichtian interval.     

What have natural and human changes wrought on the foraminifera of San Francisco Bay late Quaternary estuaries?

In this study we compare the foraminifera of modern South San Francisco Bay with fossils from sediments of a previous estuary at 125 ka to provide a basis for interpreting the impact of natural and human change on the benthic ecosystem. All the species found in the Pleistocene sediments of this study are estuarine and/or shallow-water species occurring commonly in San Francisco Bay today, except for the introduced foraminifer Trochammina hadai, a native of Japan that was not found in samples taken in San Francisco Bay before 1983. The biodiversity and species composition of the fossil and modern assemblages before the introduction of T. hadai are nearly identical, suggesting that the environmental and physical changes in the 125,000-year-old and modern estuaries have not had a significant effect on the meiofauna of the Bay. In contrast, modern anthropogenic change in the form of species introductions has impacted the modern foraminiferal assemblage: T. hadai began to dominate the modern assemblage a decade after its introduction. Similar to the recorded impacts of introductions of marine metazoan invertebrate species, the dominance of T. hadai changed species proportions in the post-1980s foraminiferal assemblage, however no known extinctions in the native foraminiferal fauna occurred.     

Early Bartonian orthophragminids (Foraminiferida) from Reineche Limestone,north African platform,Tunisia: taxonomy and paleobiogeographic implications

The orthophragminids in lower Bartonian Reineche Limestone member, a fossiliferous shallow-marine unit exposed in Cap Bon peninsula in Tunisia, are represented by 17 species assigned to Discocyclinidae Galloway 1928 and Orbitoclypeidae Brönnimann 1946. These taxa, associated with nummulitids and alveolinids, belong to the lineages of Discocyclina Gümbel 1870, Nemkovella, 1987, Orbitoclypeus Silvestri 1907, and Asterocyclina Gümbel 1870, described for the first time from north Africa lying at the southern margin of Tethyan ocean during Paleogene. We identified Nemkovella evae, previously not recorded in upper Lutetian/lower Bartonian and younger Eocene deposits of northern Tethyan platforms, and erected a new subspecies, N. evae reinechensis n. ssp. A comparison of Reineche orthophraminids, assigned to orthophragmines zone (OZ) 12 and shallow benthic zone (SBZ 17), to the well-described coeval assemblages at northern Tethyan platforms in Italy, Hungary, Turkey, and to those in Kutch Basin in the Indian subcontinent suggests that some species are confined to certain paleogeographic domains. Orbitoclypeus haynesi, the only orbitoclypeid and the most abundant orthophragminid in lower Bartonian deposits in Kutch, appears to be the most common orbitoclypeid in Reineche Limestone. In Europe, this species is not known and is replaced by Orbitoclypeus varians, the most common orbitoclypeid in middle Eocene of central Europe. Both species occur in varying proportions in marine successions in Turkey. Asterocyclina sireli, identified so far only in Turkey, occurs in Reineche Limestone and in lower Bartonian deposits in Kutch. This species is recorded for the first time in the Indian subcontinent. Relying on present study, as well as our recent studies in Kutch Basin, we conclude that the generic and specific diversity of orthophragminids decreases eastward from the peri-Mediterranean region to Indian subcontinent and to the western Pacific.     

河南鹤壁地区太原组有孔虫动物群及石炭-二叠系界限的探讨

通过对华北地台河南鹤壁地区太原组有孔虫动物群的系统研究,共鉴定出有孔虫化石18属33种,建立了一个区域性有孔虫动物组合带：Bradyina—Palaeotextularia组合带,根据有孔虫化石的属种类型、数量,应用数理统计方法得出组合带有孔虫化石在地层中的比例变化情况,并根据化石组合带与国内其它地区的有孔虫动物群进行对比研究,认为鹤壁剖面有孔虫动物群Bradyina—Palaeotextularia组合带归于晚石炭世晚期的早期（C2^2-）,进而对研究区石炭-二叠系界线的划分进行探讨,界限应该放在第16层（泥岩）和第15层（灰岩）之间。     

Recent benthic foraminifera in the southern Kattegat, Scandinavia: distributional pattern and controlling parameters

The southern Kattegat is characterized by a strong halocline at a water depth of 10–20 m. Samples were collected within and below the halocline at 12–58 m. A Q-mode factor analysis identified three major and three minor foraminiferal assemblages, each characterized by one diagnostic species. Linear regression analyses showed that the distribution of assemblages and their diagnostic species is associated with substrate and hydrography. The Bulimina marginata assemblage is connected with fine-grained, organic-rich sediments below the halocline. The Elphidium excavalum and the Eggerelloides scabrus assemblages show weak correlations with substrate and are presumably connected with the halocline. Minor assemblages of Cibicides lobatulus and Textularia bocki are associated with coarse-grained sediments. The Stainforthia fusiformis assemblage has only weak correlation with substrate and hydrography.     

Shallow water agglutinated foraminiferal response to Late Cretaceous–Early Paleocene sea-level changes in the Dakhla Oasis,Western Desert,Egypt

The Late Cretaceous (Maastrichtian) to early Paleocene (Thanetian) shallow water (<100 m) agglutinated foraminifera from a section at Dakhla Oasis (Western Desert, Egypt) were analyzed for their assemblage, species and genera distribution, diversity, depositional environment, community structure and palaeobathymetry with respect to regional tectonics, climate and global eustasy. Data suggest an equitable benthic environment with low species dominance deposited in a brackish littoral and/or marsh setting. Sea level curves using characteristic benthic foraminiferal species, genera and assemblages corroborate quantitatively generated estimate and statistical analysis. Data suggests that in the absence of or of an impoverished benthic foraminiferal fauna, a high resolution agglutinated foraminiferal dataset can be as good a predictor of the benthic community structure and environment, as its calcareous counterpart, at least for shallow settings (<100 m). Present data also provides a good window in better understanding the distribution and interrelationship between the three dominant genera, Haplophragmoides, Trochammina and Ammobaculites. Faunal changes at boundaries (Cretaceous/Paleogene, Danian/Selandian and Selandian/Thanetian) are also evaluated.     

http://www.sciencedirect.com/science/article/pii/S1674987111001356

A total of 103 surface sediment samples collected from the water depth range of 15—3300 m along Vijaydurg-Karwar stretch of central west coast of India were analyzed for foraminiferal content. Relict benthic foraminiferal assemblage was noted within 50—135 m water depth.The relict benthic foraminiferal assemblage that includes Amphistegina,Operculum and Alveolinetta in sediment samples within the water depth of 85—135 m indicates presence of coral reef at this depth during Early Holocene. The presence of barnacle fouling on Relict foraminifera at 60—90 m confirms the paleo-shoreline. The shallow depth zone is characterized by presence of agglutinated relict foraminifera.The agglutinated forms indicate freshwater influx,which eventually increased the sea level and subsequently deteriorated the paleo-coral reef.     

Late Cretaceous calcareous nannofossil and planktonic foraminiferal bioevents of the shallow-marine carbonate platform in the Mitla Pass, west central Sinai, Egypt

The first detailed biostratigraphic analyses of the Coniacian-middle Campanian shallow-marine carbonate successions exposed in the Mitla Pass, west central Sinai, Egypt have revealed the stratigraphic distribution of diverse calcareous nannofossil and planktonic foraminiferal species. Thirty-six calcareous nannofossils and thirty-two planktonic foraminifera are identified, indicating a Coniacian to middle Campanian age and four Tethyan planktonic foraminiferal and five calcareous nannofossil zones. A comparison of these bioevents from different palaeolatitudes shows considerable variation in age.Three sequence boundaries coincident with the Turonian/Coniacian, Coniacian/Santonian and Santonian/Campanian stage boundaries are recognized. A fourth sequence boundary is marked by a major upper Campanian to early Ypresian (early Eocene) unconformity. These sequence boundaries are primarily related to regional tectonism associated with the Syrian Arc Fold System and secondarily to eustatic sea-level fluctuations.     

Foraminiferal stratigraphy, palaeoenvironments and sedimentation of the glacigenic sequence southwest of Bjørrnøya

Based on four shallow drillings in the outer part of the Bjørnøya trough, palaeoenvironments of foraminifera in glacigenic sediments are discussed. Different methods were used; detailed foraminiferal analysis, oxygen and carbon stable isotope analysis and transfer functions. Six different foraminiferal assemblage zones were found. One zone, AA, appears to be pre-Pleistocene in age and contains an abundance of reworked early Tertiary foraminifera. Four of the assemblage zones have a dominant arctic foraminiferal content; however, a marked boreal input is evident, particularly in zone B where B. marginata dominates. We suggest that B. marginata has been resedimented from pre-Eemian 'warm' deposits. Its occurrence in these older warm intervals possibly reflects a lower input of the Norwegian Current into the area and possibly an increase in the relative nutrient content of the water masses. The six zones have also differing numbers of foram./gram sediment. An assemblage zone where a boreal component of foraminifera ( E. nipponica, P. bulloides ) dominates was found, zone C. We define this particular assemblage zone to be of Eemian age (isotope substage 5e). The foraminiferal assemblage composition and the oxygen and carbon isotopes from zone C indicate that oceanographic conditions in the Barents Sea during the Eemian were slightly different from those of the present and that, possibly, Atlantic waters were more prevalent.     

Foraminiferal sequence biostratigraphy of the Oligo‐Miocene Janjukian strata from Torquay,southeastern Australia

The foraminiferal fauna from two holes near the coastal section of marls and limestones at Torquay is dominated by inner to mid‐shelf benthic forms, especially the cibicidids, discorbids and miliolids. Planktonic species are rare and rarely age‐diagnostic. A cluster analysis of the species occurrences and relative abundances identified four assemblages, A to D up‐section. These assemblages also closely correspond to lithological changes characterising lithostratigraphic units: Angahook Formation (assemblage A), lower and upper Jan Juc Formation (B, C) and Puebla Clay (D). Biofacies trends based on the relative abundances of inner and outer neritic taxa led to the recognition of third‐order sequences and boundaries equivalent to TB1.1 to TB1.4, confirming a previous identification on sedimentological grounds. They demonstrate that foraminiferal assemblages were directly influenced by third‐order sea‐level fluctuations and can be used to predict third‐order sequences. The long‐uncertain regional Oligocene‐Miocene boundary is placed at the Jan Juc Formation—Puebla Clay contact, across which there was a major faunal change. Several benthic forms disappeared, at least temporarily: Cibicidoides perforatus, Amphistegina lessonii and Pararotalia mackayi. The typical Miocene planktonic taxa Globoquadrina dehiscens and Globoturborotalita brazieri made their first appearance. These events were associated with an increase in inner neritic benthos signalling a low sea‐level, consistent with the contemporaneous global pattern.     

Larger foraminifera distribution and strontium isotope stratigraphy of the La Cova limestones (Coniacian–Santonian, “Serra del Montsec”, Pyrenees, NE Spain)

The Upper Cretaceous La Cova limestones (southern Pyrenees, Spain) host a rich and diverse larger foraminiferal fauna, which represents the first diversification of K-strategists after the mass extinction at the Cenomanian–Turonian boundary.The stratigraphic distribution of the main taxa of larger foraminifera defines two assemblages. The first assemblage is characterised by the first appearance of lacazinids (Pseudolacazina loeblichi) and meandropsinids (Eofallotia simplex), by the large agglutinated Montsechiana montsechiensis, and by several species of complex rotalids (Rotorbinella campaniola, Iberorotalia reicheli, Orbitokhatina wondersmitti and Calcarinella schaubi). The second assemblage is defined by the appearance of Lacazina pyrenaica, Palandrosina taxyae and Martiguesia cyclamminiformis.A late Coniacian-early Santonian age was so far accepted for the La Cova limestones, based on indirect correlation with deep-water facies bearing planktic foraminifers of the Dicarinella concavata zone. Strontium isotope stratigraphy, based on many samples of pristine biotic calcite of rudists and ostreids, indicates that the La Cova limestones span from the early Coniacian to the early-middle Santonian boundary. The first assemblage of larger foraminifera appears very close to the early-middle Coniacian boundary and reaches its full diversity by the middle Coniacian. The originations defining the second assemblage are dated as earliest Santonian: they represent important bioevents to define the Coniacian-Santonian boundary in the shallow-water facies of the South Pyrenean province.By means of the calibration of strontium isotope stratigraphy to the Geological Time Scale, the larger foraminiferal assemblages of the La Cova limestones can be correlated to the standard biozonal scheme of ammonites, planktonic foraminifers and calcareous nannoplankton. This correlation is a first step toward a larger foraminifera standard biozonation for Upper Cretaceous carbonate platform facies.     

Palynofloral study of the intertrappean bed exposed at a new locality in Kutch district,Gujarat and its implications on palaeoenvironment and age

A palynofloral assemblage has been recorded from the intertrappean bed exposed at a new locality, near Naredi, on Naliya-Narayan Sarovar Road in western Kutch, Gujarat. This intertrappean bed (ca. 0.6 m thick) of grey laminated clay is underlain and overlain by the volcanic traps. The assemblage recovered from this bed includes algal and fungal remains, pteridophytic spores, angiospermous pollen as well as cuticles of terrestrial plants. Important palynotaxa recovered are Azolla sp., Lygodiumsporites lakiensis, Polypodiaceaesporites intrapunctatus, Compositoipollenites argutus, C. conicus, Graminidites media, Ladakhipollenites minutus, Lakiapollis ovatus, Matanomadhiasulcites sp., etc. Besides, a variety of fungal remains belonging to the genera Dictyosporites, Frasnacritetrus (Tetraploa), Kutchiathyrites, Palaeomycites (VAM fungi), Papulosporonites, Parmathyrites, Phragmothyrites, Polycellaesporonites (Alternaria), etc have been recorded. It has been deduced that this intertrappean bed was deposited in a shallow depression over the trap during short interval of quiescence in a tropical-subtropical climate. The age of the intertrappean bed is suggested as Early Palaeocene.     

Palynology, palaeoecology and palaeodepositional environment of Eocene lignites and associated sediments from Matanomadh mine, Kutch Basin, western India

Extensive Cenozoic lignite-bearing sediments in the western part of Kutch, western India provide a unique opportunity to study the floral diversity at a crucial time of early Eocene Climatic Optimum (EECO). Rock samples representing a lignite-bearing sequence from the open cast mine at Matanomadh, Gujarat, western India were collected to study the palynofloral composition and to interpret the palaeoclimate and environment of deposition. The sequence mainly composed of lignites, shales and calcareous mudstones yielded rich assemblage consists of pteridophytic spores (7 genera, 10 species), angiosperm pollens (20 genera, 26 species), fungal remains (14 genera, 16 species) and dinoflagellate cysts. The palynofloral assemblage is marked with dominance of angiospermic pollen, particularly those having affinity with the family Arecaceae. Occurrence of fungal remains in high abundance is also noticed. Based on palynomorph contents, the studied sequence is divisible into two palynozones. It is inferred that lower part of the sequences was deposited in a near-shore environment with intermittent marine incursions whereas the depositional regime of upper part was shallow marine. The climate is found to be tropical-subtropical, humid with heavy precipitation during the deposition of Matanomadh lignite-bearing sequence.