Interval Zone Research Articles

Dinoflagellate cyst biostratigraphy of initial Neotethys transgression deposits from the Cenomanian and Turonian in the Tarim Basin, western China

Under the great transgressions of the Late Cretaceous, the Neotethys Sea firstly invaded the western Tarim Basin, center Asian and this continued until the Paleogene. This study presents successive dinoflagellate cyst (dinocyst) records from the Kukebai Formaion deposited during initial transgressive periods. A total of 45 samples from the Core ZK 5-2 drilled in the southern part of the western Tarim Basin yield 78 taxa including 74 taxa of dinocysts, two genera of chlorophyte algae, and two acritarch species. Upwardly, three dinoflagellate zones are distinguished in the Kukebai Formation: Subtilisphaera perlucida (interval Zone), Cyclonephelium brevispinatum (interval zone), and Heterosphaeridium difficile (interval zone) respectively. Successive dinocyst records in this study calibrate the chronostratigraphy of the Kukebai Formation from the lower Cenomanian to the lowermost Turonian. A high abundance of Subtilisphaera perlucida and sporadic Litosphaeridium siphoniphorum can be observed in the lowest Kukebai Formation, probably indicating initial sea transgression in the Tarim Basin that took place in early Cenomanian. The distribution events of key dinocyst taxa such as the first occurrence of the H. difficile and the last occurrence of consistent occurrence of Litosphaeridium siphoniphorum, indicate that the C/T boundary interval should be approximately 183 m deep in Core ZK 5–2, at the uppermost Middle Kukebai Formation.

Pseudoreticulate-Subreticulate-Reticulate Nummulites and their possible evolution in the middle Eocene-lower Oligocene succession of Surat-Bharuch, Gujarat India

A biostratigraphically well constrained middle Eocene to lower Oligocene shelf succession (ca. 33 m) of the Amravati Formation in the Vagalkhod-Dinod area of Surat-Bharuch Districts, Gujarat, India contains Nummulites having varied septal filaments, among which complicated filaments show progressive changes in the succession. Complications by the intersection of filaments with spiral laminae/ridge, bifurcation of filaments at low angle and joining by transverse trabeculae, and bifurcation and re-joining of filaments at high and varied angles, and consecutive bifurcation and trifurcation of filaments allowed their categorization in different species. Successive appearances of pseudoreticulate filaments (Nummulites acutus, Nummulites broachensis and Nummulites longilocula), subreticulate filaments (Nummulites hormoensis and Nummulites ptukhiani) and reticulate filaments (Nummulites fabianii, Nummulites retiatus and Nummulites fichteli) reflect gradual complication with time, producing a bioseries that is also manifested by changes in canals and equatorial chambers. The eight species of Nummulites are differentiated and described within the pseudoreticulate subreticulate- reticulate group and based on their stratigraphic distribution, seven zones in ascending order namely, the Nummulites acutus Assemblage Zone, Nummulites broachensis Range Zone, SRG Barren zone, Nummulites hormoensis-Nummulites fabianii Interval Zone, Nummulites fabianii Range Zone, Nummulites fabianii-Nummulites retiatus Interval Zone and Nummulites fichteli Range Zone are recognized and described. The zones are tentatively correlated with the SB zones and their ages are assigned by planktonic foraminiferal zones. Complexity of septal filaments within the Nummulites of the succession began with the development of pseudoreticulation (by the intersection of radial filaments with spiral laminae) during the late Lutetian; afterward during the early Bartonian Stage bifurcation develops in a septal filament along with occasional joining by transverse trabeculae; subreticulation remained restricted to the late Bartonian,while reticulation appeared at the beginning of the Priabonian to flourish during the Priabonian to mid Rupelian.The bioseries by septal filaments shows three evolutionary trends in these species: 1) evolution of N. acutus to N. fichteli through N. broachensis-N. hormoensis-N. ptukhiani-N. fabianii; besides acquiring complication of septal filaments this trend shows a general increase in the size of the proloculus, an increase of the size of the B-form, increasing complication in canals, and lowering the height of equatorial chambers concomitant with the increase of length; 2) evolution of N. acutus to N. broachensis to N. longilocula; this trend is restricted to the pseudoreticulate group; discerning changes involve connecting adjacent septal filaments by transverse trabeculae and spiral laminae, and development of rudimentary mesh of septal filaments, complication in canals and slit-like long equatorial chambers; 3). evolution of N. hormoensis to N. retiatus; changes involve in the development of reticulation from subreticulate septal filaments, decrease in the height of chambers, complication in canals, and development of laminae and mesh as grooves. Nummulites acutus is ancestral to all the discussed species. The evolution of Nummulites leading to complicated septal filaments is known during the corresponding span in the Mediterranean region, East African region, and a few locations in western European and southeast Asian regions, but the trends of evolution as studied in the Amravati Formation differs in the distinct developments of pseudoreticulate lineage, N. ptukhiani as an intermediate evolutionary form between N. hormoensis and N. fabianii, and in the development of complex subreticulation from a simple one. The studied succession is the only one of its kind in the Indian region to have successive development of pseudoreticulate-subreticulate-reticulate Nummulites across the Lutetian/Bartonian, Bartonian/Priabonian and Priabonian/Rupelian boundaries.

Planktonic foraminiferal biostratigraphy and determination of the Santonian-Campanian boundary in the Zagros sedimentary basin, SW Iran

The carbonate-dominated Upper Cretaceous Ilam Formation is representative of an important reservoir in the Zagros Basin. In this study, planktonic foraminiferal biostratigraphy of the Ilam Formation was investigated in the Kuh-e-Surgah section in western Iran. In the studied section, the 170 m thick Ilam Formation is mainly composed of imestones with shale intercalations. The formation conformably overlies and underlies the Surgah and Gurpi formations, respectively. Twelve genera and 24 species of planktonic foraminifera were identified. The following planktonic foraminiferal biozones were identified: the Dicarinella asymetrica Total Range Zone (latest Coniacian- late Santonian), the Globotruncanita elevata Partial Range Zone (Santonian to early Campanian), the Globotruncana ventricosa Interval Zone (middle to late Campanian.), the Radotruncana calcarata Total Range Zone (late Campanian.), the Globotruncanella havanensis Partial Range Zone (late Campanian) and the Globotruncana aegyptiaca Interval Zone (late to latest Campanian). In general, the biozones show that the Ilam Formation in the studied section is latest Coniacian-late Campanian in age. The Santonian-Campanian boundary in the Kuh-e-Surgah section correlates with the Globotruncanita elevata Partial Range Zone. The recognized biozones in the Ilam Formation are comparable with those recorded in other parts of the Tethyan Realm. The crinoid species Marsupites testudinarius is absent in the studied section. Generally, the last occurrence of this cosmopolitan species indicates the base of the Campanian stage. The Santonian/Campanian boundary was placed in the lower part of the Globotruncanita elevata Partial Range Zone at the base of the Ilam Formation in the studied section.

The Cenomanian-Turonian oceanic anoxic event (OAE-2) and continuous drowning up to the Santonian of the Western Valles-San Luis Potosi Platform, Central to Eastern Mexico: Biostratigraphy, chemostratigraphy and paleoenvironments

The Upper Cretaceous stratigraphic succession in the western part of the Valles-San Luis Potosi Platform (central to eastern Mexico) reflect the interaction between various paleo-oceanographic factors including sea-level change, tectonic factors, and the type and supply of sediments. The El Abra Formation is a shallow-water carbonate deposit that is overlain by the hemipelagic-pelagic Soyatal Formation, which represents the transition to a deeper, eutrophic, open marine environment in the latest Cenomanian-earliest Turonian (Whiteinella archaeocretacea Partial Range Zone). This unit is linked to a sea-level rise that occurred on a global scale and flooded the platform, coinciding with the Oceanic Anoxic Event 2 (OAE 2). This change is well–marked by faunal assemblages with a low diversity, and environmental stress–resistant species as well as values of delta 13C excursion, total organic carbon (TOC) and trace element signatures. These data suggest that in this time the ocean was oxygen deficient. During the early Turonian the platform was completely drowned, which led to re-establishment of the oligotrophic environment. These conditions favored for development of the planktonic foraminifera of the Helvetoglobotruncana helvetica Total Range Zone with the occurrence of keeled forms (k/strategists) even continuing as far as the late Santonian thus in the Soyatal interval two biostratigraphic zones are also recognized: the Dicarinella concavata Interval Zone (late Turonian-late Coniacian) and Dicarinella asymetrica Total Range Zone (early-late Santonian). This indicates that the studied part of the Valles-San Luis Potosi Platform remained flooded during this time, in contrast with Mediterranean Tethys regions where recovery of the shallow-water carbonate platforms occurred in the latest Turonian to mid-Coniacian. The planktonic foraminiferal assemblages of this interval are diverse, composed of large and complex keeled morphotypes, which indicate an open deep–sea environment.

Pannonian (late Miocene) ostracod fauna from Pécs-Danitzpuszta in Southern Hungary

The large outcrop at Pécs-Danitzpuszta, southern Hungary, exposes a 65-meter-thick succession of calcareous marls, clay marls and calcareous sands that were deposited during the early history of Lake Pannon, a vast, Caspian-type lake in Central Europe in the late Miocene. Within the framework of the complex stratigraphic investigation of this succession, well preserved, relatively diverse benthic ostracod assemblages containing 39 taxa were recovered from 29 samples (16 samples were barren). Palaeoecological interpretation of the ostracod genera suggests that deposition took place in a low-energy environment, in the shallow sublittoral zone of Lake Pannon, in pliohaline (9–16‰ salinity) water. The entire succession was divided into four interval zones based on the first occurrences of assumedly useful marker fossils: Hemicytheria lorentheyi Zone (from sample D29), Hemicytheria tenuistriata Zone (from sample D17), Propontoniella candeo Zone (from sample D115) and Amplocypris abscissa Zone (from sample D209). Based on comparison to the Beočin section 150 km to the SE, where a lithologically and stratigraphically similar section was dated magnetostratigraphically by an international team, we tentatively assume that the Pannonian marl succession of the Pécs-Danitzpuszta outcrop represents the time interval of 11.6 to ca. 10 Ma.

Integrated Radiolarian and Conodont Biostratigraphy of the Middle to Late Permian Linghao Formation in Northwestern Guangxi, South China

AbstractThe Permian radiolarian zones and their correlations with conodont zones or other chronostratigraphic schemes are still under debate. In this study, four genera, 21 species and two subspecies of radiolarians together with one genus and six species of conodonts were recovered from the Linghao Formation cropping out at the Longwangpo (LWP) section, northwestern Guangxi, South China. Six radiolarian interval zones and one abundance zone are recognized in the section, namely in ascending order, the Follicucullus scholasticus, Albaillella cavitata, A. protolevis, A. levis, A. excelsa, A. triangularis Interval zones and A. yaoi Abundance Zone. They are correlated with the Clarkina dukouensis, C. guangyuanensis and C. orientalis conodont zones recognized at the same section. Based on our data, the F. scholasticus Interval Zone and the lowermost part of A. cavitata Interval Zone are recognized to be upper Capitanian age, whereas the four Albaillella Interval zones are of Lopingian age (Wuchiapingian to the late Changhsingian). Two previously known Changhsingian radiolarian zones, namely the A. triangularis and A. yaoi Interval zones, should be extended down to the uppermost Wuchiapingian in this studied section.

Taxonomic revision of Ediacaran tubular fossils: Cloudina, Sinotubulites and Conotubus

AbstractThe Ediacaran tubular fossils Cloudina, Sinotubulites, and Conotubus are taxonomically revised with type materials. It is proposed that Aulophycus lucianoi Beurlen and Sommer, 1957, is not a senior synonym of Cloudina hartmannae Germs, 1972. Instead, most of its syntypes may be assigned to Sinotubulites or other taxa. Lectotypes of Sinotubulites baimatuoensis Chen et al., 1981, and Conotubus hemiannulatus Zhang and Lin in Lin et al., 1986, are designated from rediscovered syntypes. Sinotubulites baimatuoensis Chen et al., 1981, is reported from the Mooifontein Member of Nama Group at Aar Farm, Namibia. Cloudina waldei Hahn and Pflug, 1985, is assigned to Sinotubulites baimatuoensis, and thus its occurrence range is extended to Brazil. The lectotype of Conotubus hemiannulatus shows corrugations and annulations on the surface distinguishing it from Cloudina and other collared Ediacaran tubular fossils. Based on the taxonomic revision, we propose a Cloudina hartmannae Interval Zone for the terminal Ediacaran with the upper boundary defined by the first appearance datum of Protohertzina anabarica (i.e., the index fossil of the early Cambrian Anabarites trisulcatus-Protohertzina anabarica Assemblage Zone).

New Oligocene to Early Miocene Palynomorph Zonation of GZ-1 Well, Onshore Western Niger Delta, Nigeria

Palynological studies was carried out on GZ-1 well from the onshore western Niger Delta in order to recognized a new detected developments in the varieties of key pollen and spore taxa that have shorter and more distinguished interval zones to advance stratigraphical delineation. Palynological analysis was carried out using the conventional maceration technique for recovering acid insoluble organic-walled microfossils from sediments. The result yielded rich and diversified palynomorphs. The main assemblage were dominated by angiosperm pollen grain (dominant global flora from Late Cretaceous onwards) followed by pteridophytes/bryophyte spore. Dinoflagellate cysts, on the contrast, were less diverse while the Gymnosperm pollen were scarce. The identified palynomorph were used to establish seven main zones - AF1 Psilatricolporites crassus zone, AF2 Verrucatosporites usmensis zone, AF3 Triplochiton scleroxylon zone, AF4 Crassoretitriletes vanraadshooveni zone, AF5 Acrostichum aureum zone, AF6 Gemmatriporites ogwashiensis zone and AF7 Retitricolporites irregularis zone in this study. Established on quantitative events, the zones were also divided into seven subzones with some having finer subdivisions into (a) and (b) ranging in age from Early Oligocene to Early Miocene. Previous unfiled event trends of important indicator taxa of spores and pollen accredited to Pelliceria, Caesalapinoideae, Stenochlaena palustris, Polypodiaceae, Lygodium microphyllum, Polypodiaceae, Adiantaceae and Amanoa (Euphorbiaceae) have assisted improvement of formerly used palynological zonation schemes in the Niger Delta. It is anticipated that this quantitative zonation scheme erected, will help with imminent palynostratigraphical studies in the onshore Niger delta area.

Magnetostratigraphy of lower Paleocene strata in the Ferris Formation, Hanna Basin, Wyoming, with refined resolution of the Pu1–Pu2 interval-zone boundary of the Puercan North American Land Mammal Age

ABSTRACT Recent studies of early Paleocene stratigraphic sections across the U.S. Western Interior are refining our understanding of the biotic recovery in the aftermath of the Cretaceous–Paleogene (K–Pg) mass extinction event. Herein we present magnetostratigraphic data from an approximately 600-m-thick section of strata of the Ferris Formation in the Hanna Basin, south-central Wyoming, that spans the K–Pg boundary and includes in conformable superposition the three subdivisions of the earliest Paleocene Puercan North American Land Mammal Age: interval zones Pu1, Pu2, and Pu3. Prior studies on early Paleocene stratigraphic sections in Montana to the north of Hanna Basin and in Colorado and New Mexico to the south have been only marginally successful in defining the temporal boundaries of these divisions. This earlier work typically restricted Pu1 entirely within reversed magnetochron C29r, Pu2 entirely within normal magnetochron C29n, and at least the early part of Pu3 in C29n, as well. Results of the present study confirm what has been only tentatively suggested previously: that interval zone Pu2 begins in the youngest part of C29r, with later Pu2 fauna extending into C29n. Although Pu3 is known to begin in C29n, its younger limit remains unknown in our Hanna Basin section, because the top of the local Puercan is well above the stratigraphic level of our sampling for this project. We estimate a date for the Pu1–Pu2 boundary in the Hanna Basin section of approximately 65.82 Ma—nearly 70 k.y. earlier than prior estimates. This boundary marks the transition from the Pu1 survival fauna to later phases of the mammalian recovery characterized by a significant increase in diversity, appearance of considerably larger-bodied mammals, and greater dental and dietary specializations.

Biostratigraphy, Microfacies and Depositional Environment of the Sarvak Formation at the Pyun Anticline (Zagros Basin, Southwest of Iran)

AbstractThe Sarvak Formation is a carbonate sequence of Late Albian–Early Turonian age in Zagros Basin in Iran. In this investigation, the Sarvak Formation at the Pyun Anticline section (Izeh Zone) has been studied. It consists of 797 m thick limestone which overlies the Kazhdumi Formation conformably and underlies the Gurpi Formation unconformably at the Pyun Anticline. A very rich fossil association (85 genera and 132 species) characterizes the Pyun section. Based on the stratigraphic distribution of diagnosed foraminifera, five biozones are established: 1, Muricohedbergella‐Globigerinelloides sp. assemblage zone (Late Albian); 2, Praealveolina iberica‐Chrysalidina gradata interval zone (Early Cenomanian); 3, Chrysalidina gradata‐Cisalveolina fraasi (fallax) and C. lehneri interval zone (Middle Cenomanian); 4, C. fraasi (fallax) and C. lehneri‐Praetaberina bingistani assemblage zone (Late Cenomanian); 5, Nezzazatinella picardi‐Mangashtia‐Dicyclina assemblage zone (Early Turonian). Based on the petrographic and sedimentological analyses, some 13 carbonate microfacies were identified. The investigated microfacies confirm a ramp‐type paleoenvironment. These microfacies, from distal to proximal environments, consist of: MF1: planktonic foraminifera wackestone‐packstone; MF2: Oligostegina planktonic foraminifera wackestone to packstone; MF3: planktonic‐benthic foraminifers sponge spicules wackestone‐packstone; MF4: rudist floatstone; MF5: rudist rudstone; MF6: bioclast intraclast grainstone; MF7: peloid intraclast grainstone; MF8: benthic foraminifers rudist grainstone‐packstone; MF9: peloid bioclast grainstone‐packstone; MF10: bioclast (benthic foraminifers) wackestone‐packstone; MF11: peloid bioclast packstone; MF12: dacycladacea benthic foraminifera packstone‐wackestone; MF13: miliolids wackestone‐packstone.

Foraminiferal Biostratigraphy of the Uppermost Cretaceous Period, Duhok Area, Kurdistan Region, North of Iraq

A relatively complete Late Maastrichtian succession of the upper part of the Shiranish Formation (Upper Cretaceous) in the Duhok area is investigated for the planktic foraminiferal assemblages. This studied interval consists mainly of bluish shale, marl, and thin beds of hard marly limestone all with grey-blue color. The upper contact of the Shiranish Formation is conformable with the overlies Danian Aaliji Formation. Based on the recorded planktic foraminifera and their ranges, the studied succession is subdivided into three main biozones of the latest Maastrichtian age, these zones are Pseudoguembelina hariaensis (CF3) Interval Zone, Pseudoguembelina palpebra (CF2) Interval Zone, and Plummerita hantkeninoides (CF1) Total Range Zone. These zones show continuous and complete Upper Cretaceous sediments, which are preserved in the Bade section of the Duhok area

Prediction and Forecasting of Air Quality Index in Chennai using Regression and ARIMA time series models

Air is one of the most fundamental constituents for the sustenance of life on earth. The meteorological, traffic factors, consumption of non-renewable energy sources, and industrial parameters are steadily increasing air pollution. These factors affect the welfare and prosperity of life on earth; therefore, the nature of air quality in our environment needs to be monitored continuously. The Air Quality Index (AQI), which indicates air quality, is influenced by several individual factors such as the accumulation of NO2, CO, O3, PM2.5, SO2, and PM10. This research paper aims to predict and forecast the AQI with Machine Learning (ML) techniques, namely linear regression and time series analysis. Primarily,Multi Linear Regression (MLR) model, supervised machine learning, is developed to predict AQI. NO2, Ozone(O3), PM 2.5, and SO2 sensor output collected from Central Pollution Control Board (CPCB) – Chennai region, India feed as input features and optimized AQI calculated from sensor's output set as a target to train the regression model. The obtained model parameters are validated with new and unseen sensor output. The Key Performance Indices(KPI) like co-efficient of determination, root mean square error and mean absolute error were calculated to validate the model accuracy. The K-cross-fold validation for testing data of MLR was obtained as around 92%. Secondly, the Auto-Regressive Integrated Moving Average (ARIMA) time series model is applied to forecast the AQI. The obtained model parameters were validated with unseen data with a timestamp. The forecasted AQI value of the next 15 days lies in a 95 % confidence interval zone. The model accuracy of test data was obtained as more than 80%.

Upper Aptian ammonite biostratigraphy of the Agua Salada and Mural formations, Sonora State, northwest Mexico

In this work we study the ammonoid biostratigraphy of five stratigraphic sections of the upper Aptian in the Lampazos area, and one in the Tuape area, based on 147 specimens systematically collected bed by bed. Most of the fauna is endemic to the Central Atlantic province. A new genus and species was erected: Sonoraceras tepachensis gen. nov. sp. nov. Taxonomic and systematic analyses were carried out in order to frame this new taxon. Another taxonomic contribution presented in this work is the comparison between the endemic genus Kazanskyella and its European counterpart, the genus Parahoplites. These taxonomic contributions were complemented with fourteen 3-D models of some key specimens. We also propose a local zonation for the upper Aptian, which consists of two ammonite interval zones, Kazanskyella minima and Immunitoceras immunitum, and one horizon Sonoraceras tepachensis. Since the ammonite biostratigraphy for the upper Aptian is poorly elaborated in the Central Atlantic, this newly proposed zonation constitutes a step forward in the development of a standard Central Atlantic province ammonite zonation and its correlation to the standard Mediterranean zonal scheme.

Late middle Eocene to early Oligocene radiolarian biostratigraphy in the Southern Ocean (Agulhas Ridge, ODP Leg 117, Site 1090)

The analyses of abundant and well-preserved late middle Eocene to early Oligocene radiolarian assemblages were carried out on ODP Site 1090 (Leg 177) sediments in the Atlantic Sector of the Southern Ocean. A total of 83 radiolarian events are identified and correlated with the geochronologic time scale and paleomagnetic polarity data. The high latitude Eucyrtidium spinosum and Eucyrtidium antiquum Interval Zones are recognized in the studied interval at Hole 1090B, and three new subzones are proposed herein for the Eucyrtidium spinosum Zone: Eucyrtidium nishimurae Interval Subzone (Subchrons C17n.2r to C16r), Dendrospyris stabilis Interval Subzone (Subchrons C16n.2n to C13r), and Dicolocapsa microcephala Interval Subzone (Subchron C13r). The bases of these subzones are defined by the first occurrences of Eucyrtidium spinosum, Dendrospyris stabilis and Dicolocapsa microcephala, respectively. The proposal of these subzones could significantly improve the biostratigraphic resolution of the middle to late Eocene interval from high latitude regions. The FOs of Axoprunum irregularis and Eucyrtidium antiquum are nearly synchronous in the Southern Ocean, and could be used to estimate the Eocene/Oligocene boundary. Other radiolarian events such as the FOs of Dendrospyris stabilis, Dicolocapsa microcephala, and Zygocircus bütschli, and the LO of Eucyrtidium nishimurae are synchronous or approximately synchronous in the Southern Ocean. In contrast, the LOs of Axoprunum pierinae, Periphaena decora, and Siphocampe quadrata, and the FO of Artostrobus annulatus are commonly diachronous among different sites in the Southern Ocean.

Burdigalian-Langhian foraminifera of the northwest High Zagros Thrust Belt, southwest Iran

Abstract The foraminiferal contents of the lower–middle Miocene succession exposed in three sections in north Nur Abad on the northwestern side of the High Zagros Thrust Belt were studied. Assemblages of larger foraminifera from these sections can be referred to Zone SBZ 25 (and the Miogypsina globulus and Miogypsina intermedia subzones), which correlates with the Burdigalian Stage. For the first time, planktonic foraminifera documented from the Nur Abad area document Lang-hian deposits in the High Zagros, the upper 20 metres of the upper Sayl Cheshmeh section being characterised by the occurrence of planktonic foraminifera such as Globigerina concinna (Reuss), Globigerina diplostoma (Reuss), Globigerinoides obliquus (Bolli), Orbulina bilobata (d’Orbigny) and O.universa (d’Orbigny). This association characterises the Orbulina suturalis Interval Zone.

Smithian (Olenekian, Early Triassic) Conodonts from Ammonoid-Bearing Limestone Blocks at Crittenden Springs, Elko County, Nevada, USA

The ammonoid-bearing limestone blocks at the classic Crittenden Springs ammonoid site belong to the lower part of the Lower Triassic Thaynes Group. These 0.5–1.2 m thick blocks, consisting mainly of bioclastic floatstone and rudstone, contain abundant macro- and micro-fossils such as ammonoids, gastropods, bivalves and scaphopod shells, as well as conodont elements, fish and echinoid remains. Ammonoid and conodont assemblages obtained from three blocks are utilized for biostratigraphical analysis. Twelve informal Smithian ammonoid biostratigraphic intervals from a previous study are condensed into four ammonoid beds, based on the range of age-diagnostic taxa, in ascending order: Meekoceras millardense-M. aff. olivieri beds, Owenites koeneni beds, Anasibirites multiformis bed, and Condensoceras youngi bed. Conodonts recovered from the three blocks consist of 30 species distributed among 15 genera, including one newly described taxon, i.e., Guangxidella minuta Maekawa and Jenks sp. nov. The blocks are divided into two conodont interval zones, i.e., the Novispathodus ex gr. waageni Interval Zone and Nv. pingdingshanensis Interval Zone, based on the first occurrences of their eponymous taxa. Additionally, four conodont range zones, i.e., the Paullella meeki Range Zone, Guangxidella bransoni Range Zone, Scythogondolella milleri Range Zone, and Borinella buurensis Range Zone are recognized, based on the ranges of these four index species. Conodonts within these interval and range zones vary in age from middle Smithian to latest Smithian. The presence of key ammonoid and conodont taxa regarding the Smithian-Spathian boundary (SSB) such as the AW (Anasibirites and Wasatchites) and GXP (Glyptophiceras, Xenoceltites and Pseudosageceras) ammonoid assemblages and the conodonts B. buurensis, Nv. pingdingshanensis and S. milleri demonstrate that the study area is an important reference site for the SSB in the eastern Panthalassa area.

Calcareous nannobiostratigraphy of the Hartha Formation, East Baghdad well No.6, Central Iraq

Fifteen samples of Limestone from the Hartha Formation were obtained from East Baghdad well No.6, Central Iraq, from the depth (2247-2261 meter) about 14 meters thickness. Detail investigation was carried out, from which fifteen species of calcareous nannofossils identified; eleven were descried from other regions and four were left under an open name because of lack of material or rare of samples. The recorded calcareous nannofossil assemblages recognized two biozones these from the lower to the upper part of the section: 1 - Eiffellithus eximius Interval Zone (CC19) part 2- Ceratolithoides aculeus Interval Zone (CC20) part These biozones are correlated with other calcareous nannofossils biozones from both local and regional sections that lead to conclude the age of the Middle Campanian.

Planktic foraminifera of the upper Barremian–Aptian black shale intervals from the Chaqiela section (Gamba, southern Tibet): Biostratigraphic and palaeoenvironmental implications

Marine sedimentary intervals of the upper Barremian–upper Aptian record the profound changes in global plate configurations and the ocean-climate system. Black shale lithofacies of the Lower Cretaceous crop out extensively in the Tethyan Himalaya region of southern Tibet, and in the Gamba area they are assigned to the Gambadongshan Formation. By using 3–5% hydrofluoric acid, well-preserved planktic foraminiferal tests have been recovered for the first time from black shales in the Chaqiela section of the Gambadongshan Formation. The detailed foraminiferal biostratigraphic work allowed recognition of four upper Barremian to upper Aptian planktic biozones: Hedbergella excelsa Interval Zone, Globigerinelloides ferreolensis Taxon-Range Zone, Hedbergella infracretacea Partial-Range Zone, and the Paraticinella rohri Taxon-Range Zone. Total organic carbon (TOC) and organic carbon isotope (δ13Corg) records were generated for the Chaqiela section. The C-isotope profile and the planktic foraminiferal data enable the identification of Oceanic Anoxic Event 1a (OAE 1a) at the lower part of the Globigerinelloides ferreolensis Taxon-Range Zone. Diagenetic processes, lower sea surface temperature, and the regional hydrologic cycle were probably the main factors for the development of OAE 1a in the Chaqiela section. The relatively higher δ13Corg values and smaller size of carbon isotopic fluctuations in the Chaqiela section may represent the local expression of OAE 1a in the Gamba area. A long-term negative δ13Corg excursion and a decreased trend of planktic foraminiferal abundance relative to benthic foraminifera, in the upper part of the Gambadongshan Formation may suggest a lower sea-level during the late Aptian.

Upper Cretaceous (Coniacian -Campanian) siliciclastic/carbonate ramp depositional sequences and relative sea-level changes in Sinai, Egypt: Implications from facies analysis

Through the analysis of biostratigraphy, facies types and distribution, lithofacies associations, and bounding surfaces, we derived high-resolution sequence stratigraphy of the mixed siliciclastic–carbonate rocks for four sections in the Coniacian–Campanian succession in Sinai (Egypt). These stratigraphic sections provide a framework for studying the sedimentary-facies evolution, the paleogeography, and the role of eustatic and tectonic processes in Egypt and surrounding countries. Twenty-six foraminiferal species and four foraminiferal zones (the Dicarinella concavata Interval Zone in the upper Coniacian, Dicarinella asymetrica Total Zone in the Santonian, Globotruncanita elevata Partial Range Zone in the lower–middle Campanian, and Globotruncanita ventricosa Partial Range Zone in the middle Campanian) are noted. Twenty-three lithofacies and microfacies types into six facies associations ranging from progradational shoreface to outer ramp are detected and categorized. These facies associations exhibit lateral variation and deepening toward the north from siliciclastic–carbonate (Matulla Formation) to dominant carbonate (Themed Formation). Three sequences separated by four sequence boundaries have been determined in the field and/or from strong vertical facies changes associated with short time gaps representing the Turonian–Coniacian; the lower–middle and upper Coniacian; the upper Coniacian–Santonian; and the Santonian–Campanian stage boundaries. Comparisons of the examined sequence boundaries in Egypt and in some parts of Europe, within the Arabian Plate, and in global charts suggest that eustatic and tectonic effects were simultaneous.

BIOSTRATIGRAPHY ANALYSIS OF BARBATOS-1 EXPLORATION WELL IN TOMORI BLOCK, BANGGAI BASIN, EAST ARM OF SULAWESI

A biostratigraphic analysis was carried out on 60 samples taken from the Barbatos-1 Well, located within the Tomori Block, Banggai Tertiary Basin, East Arm of Sulawesi. The Barbatos-1 well was selected for this study because it is composed of rock sequences which are the main reservoir in the Tomori Block. Biostratigraphic analysis was conducted to determine the relative age and depositional environment of the sample. The age of the sample is determined based on the interval zone. The depositional environment is estimated based on the ratio of plankton (P/B ratio) and fossil facies. The results revealed that the rock formations studied were deposited in the Miocene to Holocene age. The lowest layer is the Orbulina bilobata-Zone which was deposited at N10 – N12 (lower Middle Miocene) in the bathyal environment. The layer above is a biozonation of Globorotalia menardii, deposited at N12 – N14 (upper Middle Miocene) in a neritic environment. The next layer is the biozonation of Sphaeroidinella subdehiscens – Globigerina praebulloides which was deposited at N14 – N17 (Middle Miocene – Late Miocene) in the bathyal environment. The topmost layer is the biozonation of Orbulina universa – Globigerinoides immaturus which was deposited at N17 – N23 or Pliocene – Holocene in the bathyal environment. In the top two layers, there are fossil fragments that come from older rock layers (Early Tertiary).