Cenomanian Succession Research Articles

The El Mizab formation (Talerhza Basin, north-west Morocco): Albian–early Cenomanian faunal diversity and paleoenvironment

The Talerhza Basin is a small basin in north-west Morocco, in which the Albian–lower Cenomanian succession consists of three formations; in ascending order, the El Heifouf, Bab Lkarma and El Mizab formations. The first two units, of early–middle Albian age, comprise sandy marlstones and sandy limestones, respectively, and yield rare gastropods. The El Mizab Formation consists of an alternation of marlstones and argillaceous limestones and is richest in macrofauna, being divided into five informal members. The first member (silty marly limestone) is rich in small-sized debris of oyster shells and also yields gastropods and irregular echinoids; the second (lower shelly marly limestone) and the fourth (upper shelly marly limestone) members are rich in bivalves and contain, mainly the second member, gastropods, irregular echinoids and ammonites of late Albian age, representing the Mortoniceras pricei, Mortoniceras inflatum and Mortoniceras fallax zones; the third member (platy chalky limestone) is barren of macrofauna; the fifth one (marly limestone with Rhynchostreon), of early Cenomanian age, is rich in a monospecific bivalve, Rhynchostreon suborbiculatum. Twenty-eight species of bivalves, three irregular echinoids, ten gastropods and nine ammonites have been identified. The spatial distribution of bivalve faunas through the Cretaceous basin shows that some of these taxa were extremely abundant; mainly Lopha syphax in the upper Albian and Rhynchostreon suborbiculatum in the lower Cenomanian deposits. Most of the studied groups of macrofauna are common to several Cretaceous epicontinental basins of northern Gondwana, western and eastern margins of the Atlantic Ocean and the Cretaceous trans-Saharan marine corridor.

Lithofacies and Clay Mineral Analysis of the Upper Cenomanian Ms'ad Formation, Rutbah Area, Western Iraq

The Cenomanian succession in Rutbah City, western Iraq, is composed of siliciclastic carbonate with multicolored paleosoil layers that refer to unconformity surfaces within the Ms'ad Formation. The current study will examine the clay mineralogy and facies to determine the source of these clay minerals and depositional settings. Fifteen carbonate facies have been identified as three distinct facies associations (FA1–FA3). These FAs are supratidal to intertidal (FA1), semi-restricted lagoon (FA2), and shallow open subtidal ramp with patches of a rudist-bivalve reef (FA3). The reported Multispirina Iranica-Nezzat simplex-Chrysalidina gradata assemblage Zone within the Ms'ad Formation indicated the Cenomanian age. Clay mineral analysis displays three distinctive clay mineral assemblages; kaolinite-dominated with illite (assemblage A), R0-dominated (smectite-rich illite/smectite mixed layers) with kaolinite and illite (assemblage B), and illite-dominated (illite and illite-rich illite/smectite mixed layers) with kaolinite and R0 (assemblage C). Most of these clays are detrital, generated by weathering source rocks (igneous, metamorphic, and sedimentary) under various paleoclimatic circumstances. The Kaolinite-dominated assemblage A represents intense chemical weathering from hot, humid circumstances. Smectite-dominated R0 assemblages were created by weathering alkaline rocks in flat pedogenic soils with seasonal humidity. The source of clay minerals in the studied region was subject to a dry climate towards the end of the Cenomanian period, which encouraged physical weathering and the production of illite-rich assemblages.

Литофациальная интерпретация сеноманских отложений на севере западно-сибирского нефтегазоносного бассейна

The lithofacies of the Cenomanian succession within a gas field in the north of the West Siberian basin were studied using well log information especially spontaneous potential log to determine the lithostratigraphy, hydrodynamic characteristics, possible reservoir sands and depositional environment of the study area for opportunities that will support the exploration program. Geophysical well logs from six profile wells were used for this study. The lithostratigraphic model and sequence-stratigraphic frame were developed using spontaneous potential log curves to identify lithic units like sand, silt and mud. The depositional environments penetrated by the wells interpreted from log signatures gave four main types of lithofacies: Foreshore, Regressive Shoreface; Transgressive Shoreface; Discontinuous Currents were recognized from the stacking patterns of the spontaneous potential curves by modified electro facies classification. The stratigraphic column of the wells was subdivided into parasequences composing four sequences within the regional stratigraphic trend.

Palynostratigraphy and palaeoenvironmental evolution of the Aptian to lower Cenomanian succession in the Serranía de Cuenca (Eastern Spain)

The Aptian to lower Cenomanian succession from the Serranía de Cuenca region (Eastern Iberia, Spain) comprises a time-span largely understudied regarding palynology and biostratigraphy. This research studies the deposits of three stratigraphic units that crop out in this region (the Contreras Formation, the El Burgal Member and the Utrillas Group), allowing identification, study and sampling of the palynofloras from the Aptian–?early Cenomanian time-interval. The studied sections are grouped into three sectors based on the palynostratigraphic ages obtained: the MPB, TU, and CT sectors, respectively. The palynoflora is dominated by gymnosperm pollen grains and diversified spores of ferns and allies. The palynofloral evidence and regional geology indicate that the sampled levels in the MPB sector are Aptian in age, whereas those levels sampled at the TU and CT sectors are dated as middle Albian–?early Cenomanian. The Aptian palynofloras of this sector differ from other contemporaneous sites of Europe and North America in the possible occurrence of tricolpate angiosperm pollen. In general, angiosperm pollen does not present high percentages; however, it becomes more diversified from the middle Albian in the TU and CT sectors, where more than 20 taxa were recorded on average. The studied pollen assemblages conform with the characteristics of the early Cenophytic palynofloras. Likewise, an increase in dinocysts towards the upper levels of the sedimentary succession in the TU and CT sectors is consistent with the transgressive nature of the deposits, documenting the progressive landward expansion of Western Tethys in Iberia during Albian to ?early Cenomanian times.

Brittle stars from the upper Cenomanian of the Preafrican platform: First ophiuroid remains for the Cretaceous of Algeria

While Late Cretaceous ophiuroids are relatively well known in Europe, these faunas have been much less studied in North Africa. With the exception of some Tunisian assemblages preliminary described at the turn of the 21st century, nothing is known about the Cretaceous brittle stars of the southwestern Tethyan margin. The present paper seeks to bring the first data about hitherto unknown ophiuroids recently found in the early upper Cenomanian succession of the eastern side of the Preafrican trough (Menaguir section, Algeria). This “community” of brittle stars comprises at least eight species. Most of them are probably new, but have not been formally named here. These are representatives of the families Hemieuryalidae, Amphiuridae, Ophiodermatidae, Ophiacanthidae, Ophiopezidae and probably also Ophiomyxidae and Ophiobyrsidae. Almost all vertebrae are zygospondylous; no streptospondylous vertebrae indicate the absence of the order Euryalida here. Most of the ophiuroids belong to the orders Amphilepidida and Ophiacanthida. Ophiotitanos serrata, Ophiomyxa? aff. jekerica, Ophiojagtus? sp. and some other taxa resembling ophiuroid assemblages from the Late Cretaceous of central, western and northern Europe. With respect to the late Cenomanian age, the depth of the sea and the taxonomic composition, there are some similarities with ophiuroids of the Bohemian Cretaceous Basin. The mid-ramp subtidal facies suggests that brittle stars lived here in a warm, euphotic and probably shallow sea.

Palynostratigraphy and palaeoclimate of the Valanginian–Cenomanian subsurface succession in Hamza-1X well, Matruh Basin, Egypt

Diverse palynomorph assemblages of spores, pollen grains and dinoflagellate cysts have been yielded from the palynological analyses of 115 ditch cutting samples covering the Valanginian– Cenomanian succession encountered in Hamza-1X well, Matruh Basin, north Egypt. The complex sit- uations in the north Western Desert requires more revisited palynozones for better understanding of the subsurface successions therein. Consequently, the first downhole palyno-events will be very helpful in solving some issues concerning the age determination and correlation. Seventy palynomorph species (47 spores and pollen grains; 23 dinoflagellate cyst species) were identified from all the productive samples which used to divide the studied succession into numerous sporomorph and dinoflagellate biozones based on the last occurrence datum for the recovered marker taxa. Four sporomorph inter- val biozones and six dinoflagellate cyst interval biozones were differentiated from the same studied stratigraphic succession. The four sporomorph biozones are presented, in ascending order as follows: Aequitriradites spinulosus and Impardecispora apiverrucata Interval Zone (late Valanginian– early Barremian), Pilosisporites trichopapillosus I. Z. (late Barremian), Murospora florida I. Z. (early Aptian–late Aptian), and Elaterosporites klaszii I. Z. (early Albian– early Cenomanian). The seven dinoflagellate cysts biozones are Muderongia simplex I. Z. (late Valanginian–early Barremian), Pseudoceratium anaphrissum I. Z. (late Barremian– early Aptian), Cribroperidinium edwardsii I. Z. (early Aptian), Subtilisphaera perlucida I. Z. (late Aptian), Oligosphaerdium complex I. Z. (early– late Albian), Dinopterygium cladoides and Coronifera oceanica Assemblage Zone (early Cenomanian). From the palaeoclimatic point of view, the studied interval could be differentiated into two climatic intervals; the lower arid interval that comprises the Alam El Bueib Formation and dominated by the arid xerophyte elements like Sphaeripollenites and Classopollis. The upper humid interval represents the Alamein, Dahab, Kharita and Bahariya formations that is dominated by the humid hygrophyte elements, such as Murospora, Crybeolsporites, Elaterosporites, Afropollis and Deltoidospora.

Syn-depositional continental rifting of the Southeastern Neo-Tethys margin during the Albian–Cenomanian: evidence from stratigraphic correlation

ABSTRACT Albian–Cenomanian successions (Kazhdumi and Sarvak formations) represent remarkable variations in thickness, facies, fauna, and environments throughout the Zagros area. In the Coastal Fars (Charmu section), sedimentological and paleontological data evidence an intrashelf, with depths of 10s–100s m, surrounded by a shallow carbonate platform. Due to its depth, deposition of sequences in this setting has been controlled by eustatic sea-level changes rather than eurybathic changes, and several condensation episodes occurred related to marine transgressions. These observations are different from those in the adjacent sections in the Coastal Fars which recorded subaerial exposures instead. Combined with previous studies, this study denotes several intrashelf basins enclosed by a shallow carbonate platform on the southeastern margin of the Neo-Tethys during the Albian–Cenomanian. Development of intrashelf basins corresponds to basement faults in the Fars Salient. Likely, an extensional tectonic regime associated with a rifting event created horst–graben architecture by exerting extension along the basement faults and reactivating salt structures. Deposition on these troughs and highs led to the facies and thickness variations of the concomitant sequences. Development of several intrashelf basins on the southeastern margin of the Neo-Tethys indicates that syn-depositional continental rifting event could occur during the Albian–Cenomanian, prior to the tectonic inversion around the earliest Turonian.

Calcareous nannoplankton proxies for palaeoenvironmental reconstruction of the Albian–Cenomanian succession in North-western Israel (Mount Carmel Region)

Abstract We present data on the calcareous nannofossil distribution in the Albian–Cenomanian borehole CT8 obtained from the Carmel area, NW Israel. The nannofloral assemblage consists of 113 species, with Watznaueria spp. dominating the entire succession. The detailed calcareous nannofossil biostratigraphy of this section is established, and seven nannofossil (sub)zones are recognised. For the first time the age of the Tavasim Tuff (V2) is biostratigraphically identified as Late Albian. The quantitative analysis of the calcareous nannofossils suggests warm, open marine or coastal, mainly oligotrophic conditions throughout the entire succession of borehole CT8, with evident fluctuations of temperatures and fertility and a general trend towards cooling in the uppermost part of the sequence (Middle–Late Cenomanian). Temperature and nutrient variations correspond to those in the western Tethys, thus suggesting at least a supra-regional extent of processes detected in the Carmel Region. The biostratigraphy shows no evidence of hiatuses in the studied section, but the absence of positive carbon isotope anomalies associated with the Oceanic Anoxic Event (OAE) 1d and Mid-Cenomanian Event elsewhere suggests that the OAE 1d is possibly missing in the studied section due to a hiatus around the Isfiye Fm./Arqan Fm. boundary.

The Chalk Group (Upper Cretaceous) of the Northern Province, eastern England – a review

A review of the Chalk of the Northern Province recognizes six formations, five of which (Hunstanton, Ferriby, Welton, Burnham and Flamborough formations) crop out in northern Norfolk, Lincolnshire and Yorkshire, and a sixth (Rowe Formation) is buried beneath the drift of Holderness. The Hunstanton, Ferriby and Flamborough formations are largely devoid of flints, whereas the Welton (other than its two basal members) and Burnham formations have nodular and tabular flints, respectively. Previous work on the lithostratigraphy and marker beds is presented, and an overview of the distribution of the more important macrofossils is provided. Especial attention is given to the succession at Speeton through the Hunstanton, Ferriby and lower Welton formations with details of the oxygen and carbon isotope signatures. The Speeton section is internationally important because of its expanded Albian-Mid Cenomanian succession. Small sections of the Burnham Formation in Speeton–Buckton cliffs are also presented for the first time. The appendix reviews the relevant Cretaceous stage boundaries with reference to the Chalk of the Northern Province together with details of the fossil zones that are used in this paper.

Impacts of the petrophysical and diagenetic aspects on the geomechanical properties of the dolomitic sequence of Gebel El-Halal, Sinai, Egypt

The aim of this paper is to demonstrate the controlling effect of the mineral composition, the diagenetic history and the petrophysical properties on the geomechanical properties and durability of the dolomitic El-Halal Formation in its type section in North Sinai as well as its economic potential for construction purposes. The petrographic studies include descriptions of both the mineral composition and diagenetic processes, while the petrophysical studies measure the density, porosity, permeability and true formation resistivity factor. In addition, some geomechanical laboratory tests were conducted, including the petrographic description of the mineral composition and diagenetic processes, as well as the Schmidt Hammer number (SHV), point load index (IS50), uniaxial compressive strength (UCS), and ultrasonic longitudinal wave velocity measurements. Scanning electron microscopy was used to help in pore-type description (intergranular, vuggy, etc.). Based on lithologic changes and mineral composition, the El-Halal Formation can be subdivided into three informal members: (1) lower dolomitic limestone, (2) middle sandy dolostone and (3) upper dolostone member. Petrographically, the sequence consists of three dominant microfacies: (1) dolomitic mudstone microfacies (dolomitic micrite to dolomicrite), (2) dolowackestone (clayey to sandy dolomicrite), and (3) dolomudstone microfacies (dolosparite). The most diagnostic diagenetic processes are dolomitization, cementation by calcite, aggrading neomorphism and the creation of authigenic illite. In the study area, dolomitization has affected almost all the Cenomanian succession. The SHV, IS50, and UCS values of the samples indicate high-strength rocks. The present study indicates the dependence of the geomechanical properties on the petrophysical properties and the mineral composition of the studied rocks. Modeling the properties indicates a reliable correlation between the different parameters which can be applied for predicting and characterizing the dolomitic El-Halal Formation elsewhere. The results of the present investigation are useful for studying the geomechanical and petrophysical properties of similar dolomitic sequences and in ranking its potential as construction materials.

Sequence Stratigraphy and Rudist Facies Development of the Upper Barremian‐Lower Cenomanian Platform, Northern Sinai, Egypt

AbstractThe Lower Cretaceous sections in northern Sinai are composed of the Risan Aneiza (upper Barremian‐middle Albian) and the Halal (middle Albian‐lower Cenomanian) formations. The facies reflect subtle paleobathymetry from inner to outer ramp facies. The inner ramp facies are peritidal, protected to open marine lagoons, shoals and rudist biostrome facies. The inner ramp facies grade northward into outer ramp deposits. The upper Barremian‐lower Cenomanian succession is subdivided into nine depositional sequences correlated with those recognized in the neighbouring Tethyan areas. These sequences are subdivided into 19 medium‐scale sequences based on the facies evolution, the recorded hardgrounds and flooding surfaces, interpreted as the result of eustatic sea level changes and local tectonic activities of the early Syrian Arc rifting stage. Each sequence contains a lower retrogradational parasequence set that constituted the transgressive systems tracts and an upper progradational parasequence set that formed the highstand systems tracts. Nine rudist levels are recorded in the upper Barremian through lower Cenomanian succession at Gabal Raghawi. At Gabal Yelleg two rudist levels are found in the Albian. The rudist levels are associated with the highstand systems tract deposits because of the suitability of the trophic conditions in the rudist‐dominated ramp.

Aptian–early Cenomanian ammonites from north Sinai, Egypt: Systematic paleontology and biostratigraphy

The Aptian–lower Cenomanian succession exposed in north Sinai is subdivided into two formations; the Risan Aneiza Formation (Aptian–lower Albian) and the Halal Formation (middle Albian–lower Cenomanian). These deposits are rich in fossils, especially ammonites. Thirty-one ammonite species have been identified and systematically described from the Aptian–lower Cenomanian successions exposed at Gebel El Tourkumanyia, Gebel El Mistan, and Wadi El Karm. The studied ammonites belong to 22 genera, 13 families, and 4 suborders. The genus Acompsoceras along with three species Eogaudryceras (Eotetragonites) raspaili Breistroffer, Mortoniceras (Subschloenbachia) rostratum (J. Sowerby) and Mariella (M.) essenensis (Geinitz) are recorded herein for the first time from Egypt. The identified ammonites enabled the recognition of five biozones in Gebel El Tourkumanyia, four biozones in Gebel El Mistan, and two biozones in Wadi El Karm. The five recognized biozones in Gebel El Tourkumanyia are Aconeceras (A.) nisus, Knemiceras gracile, Dipoloceras (D.) cristatum, Mortoniceras (M.) inflatum, and Mortoniceras (Subschloenbachia) rostratum zones. The recognized biozones in Gebel El Mistan are Cheloniceras (Epicheloniceras) tschernyschewi, Knemiceras gracile, Dipoloceras (D.) cristatum, and Mortoniceras (M.) inflatum zones. The two biozones of Wadi El Karm are Mortoniceras (Subschloenbachia) rostratum and Mantelliceras saxbii zones.

アルビアン上部〜セノマニアン下部の生層序 : 北海道シューパロ地域の場合

アルビアン上部〜セノマニアン下部の生層序 : 北海道シューパロ地域の場合

New Albian to Cenomanian (Cretaceous) dinoflagellate cyst taxa of ovoidinioid affinities from East Greenland, the Barents Sea and England

ABSTRACTPalyno-biostratigraphical studies of upper Albian-Lower Cenomanian successions from East Greenland, the south-western Barents Sea and south-eastern England have revealed new dinoflagellate cyst taxa of clear or questioned ovoidinioid affinities. This paper describes the new genus Sindridinium, four new species – Ovoidinium epelidosphaeroides sp. nov., Epelidosphaeridia manifesta sp. nov., Sindridinium borealis gen. et sp. nov. and Sindridinium anaanae gen. et sp. nov. – and proposes a new combination, Sindridinium? torulosa comb. nov. (formerly Canningia torulosa). The genus Epelidosphaeridia is emended based on features seen in E. manifesta sp. nov., which demonstrate peridiniacean affinities and support inclusion in the Ovoidinioideae. Morphological gradations between Epelidosphaeridia spinosa, E. manifesta sp. nov. and Ovoidinium epelidosphaeroides sp. nov., suggest close phylogenetic relationships, also postulated between Sindridinium? torulosa comb. nov., S. borealis gen. et sp. nov. and S. anaanae gen. et sp. nov. The stratigraphic ranges of the taxa described are calibrated to known dinoflagellate markers and mid-Cretaceous ammonites.

Source rock evaluation of Kharita and Bahariya formations in some wells, North Western Desert, Egypt: Visual palynofacies and organic geochemical approaches

Palynofacies analyses were applied on ninety-one samples from the subsurface Albian – Cenomanian succession represented by Kharita and Bahariya formations, encountered in El-Noor, and South Sallum wells, located in the North Western Desert, Egypt, to visually characterize the content of dispersed organic matter, as well as, organic geochemical characterization to reveal the depositional paleoenvironments and source rock potentiality. The result recognized of five palynofacies associations in the studied interval. The deposition of Kharita Formation took place mainly in a steady and a relatively stable deltaic to marginal environment continued as well in the lower part of Bahariya Formation with minor changes. The marine influence became more common in the upper part of Bahariya Formation showing the exceptional high hydrocarbon potential recorded in the studied interval. This indicates marine transgression by the end of the early Cenomanian (Upper Bahariya) age. Samples from the Kharita Formation contain abundant brown phytoclasts which suggest gas-prone kerogen type III and IV. While Bahariya Formation includes translucent, brown cuticles and woody tracheid phytoclasts pointing to more promising gas-prone kerogen type III. The organic geochemical analysis shows poor to fair gas-prone source rock potential within the study section., Thermally, the color of the spore grains in Kharita and Bahariya formations show that dark yellow to orange, indicates immature besides their general little poor hydrocarbon generation potentiality.

Biostratigraphy and facies analysis of the Upper Cretaceous–Danian? platform carbonate succession in the Kuyucak area, western Central Taurides, S Turkey

The Upper Cretaceous succession outcropping in the Anamas–Akseki Autochton, consists of approximately 500 m thick purely platform carbonate sediments. It begins with Cenomanian limestones intercalated with limestone breccias (Unit-1) containing mainly Pseudorhapydionina dubia, Pseudonummoloculina heimi, Spiroloculina cretacea (Assemblage I) and unconformably overlies the Lower Cretaceous (Barremian–Aptian) limestones with Vercorsella laurentii, Praechrysalidina infracretacea and Salpingoporella hasi. The Cenomanian limestones include foraminiferal packstone–wackestone, peloidal packstone–wackestone and mudstone microfacies deposited in restricted platform conditions. The Cenomanian succession is truncated by an unconformity characterised by locale bauxite deposits. Immediately above the unconformable surface, dolomitic limestones and rudistid limestones (Unit-2) are assigned to the upper Campanian based on the benthic foraminiferal assemblage (Assemblage II) comprising mainly Murciella gr. cuvillieri, Pseudocyclammina sphaeroidea, Accordiella conica, Scandonea samnitica and Fleuryana adriatica (smaller-sized populations). The upper Campanian limestones composed of dominantly foraminiferal-microbial packstone–wackestone microfacies deposited in shallow water environment with low energy, restricted circulation. The following limestones of the Unit-2 is characterised by sporadic intercalation of “open shelf” Orbitoides, Omphalocyclus, Siderolites assemblage (Assemblage III), assigned to the Maastrichtian, in addition to pre-existing “restricted platform” species. In the upper part of this biozone, the Rhapydionina liburnica/Fleuryana adriatica concurrent range subzone (Assemblage IIIb) is distinguished by the presence of Valvulina aff. triangularis, Loftusia minor as well as the nominal species. The Maastrichtian limestones with sporadically open marine influence consist of bioclastic (rudist-bearing) packstone–floatstone, foraminiferal packstone–wackestone with rudist fragments and peloidal/intraclastic packstone–wackestone microfacies deposited in shallow subtidal–subtidal (lagoonal) environments. The Upper Cretaceous succession passes upwardly into 70 m thick limestones and clayey limestones (Unit-3) which do not contain rudists and pre-existing foraminiferal assemblage with one exception Valvulina aff. triangularis. Variable amounts of ostracoda, discorbids, miliolids, dasycladacean algae and Stomatorbina sp. (Assemblage IV) occur into mud-rich microfacies suggesting restricted conditions with low water energy. A probable Danian age is proposed for the Unit-3 based on the occurrence of Valvulina aff. triangularis and Stomatorbina sp. which were previously recorded from Danian of peri-Tethyan platforms.

Cenomanian Turrilitidae (Cretaceous heteromorph ammonites) from the Koppeh Dagh, northeast Iran: Taxonomy and stratigraphic implications

Early and early middle Cenomanian turrilitid ammonoids from the upper part of the Albian–Cenomanian Aitamir Formation of the Koppeh Dagh (northeast Iran) are described, illustrated and placed in an integrated stratigraphic context. The Aitamir Formation represents a graded siliciclastic shelf system and the turrilitid faunas comprise eight different species. Representatives of Mariella and Hypoturrilites have been recorded from a lower Cenomanian horizon in the Ghorghoreh section, corresponding to the Mantelliceras mantelli ammonite biozone. Mariella bicarinata (Kner, 1852) and H. wiedmanni Collignon, 1964 are recorded for the first time from Iran and the larger palaeobiogeographical area, respectively. The horizons with Turrilites costatus and T. scheuchzerianus at Taherabad can be dated as early middle Cenomanian Acanthoceras rhotomagense Zone, T. costatus Subzone. Concentrations of ammonoids commonly occur above regressive sandstone units, at the transition into overlying deeper marine shale units and in their lower parts, respectively. Such intervals represent the early transgressive systems tract of depositional sequences and may thus be regarded as early transgressive, slightly condensed shell accumulations. The uppermost lower to lower middle Cenomanian succession at Taherabad is of striking bio-, event- and sequence stratigraphic similarity to contemporaneous sections in northwest Europe. It reflects deposition during falling and low sea-level associated with the latest early Cenomanian unconformity SB Ce 3 as well as the pulsating transgressive development during the early middle Cenomanian, including levels correlative to the arlesiensis, primus and Mid-Cenomanian events in northwest Europe.

The Bauxite deposits of Seydişehir region (Mortaş and Doğankuzu deposits); Their geological, mineralogical and geochemical characteristics

Turkey hosts essential bauxite deposits, typically of the karstic-type. The most economically important bauxite deposits of Turkey form in the Seydisehir-Akseki region of the central Taurides Mountains. The Mortas and Dogankuzu deposits are the most important deposits in that region. The bauxite beds contain boehmite, hematite, rutile, smectite, quartz, diaspore, calcite, pyrite, marcasite and goethite. Brown to red-colored bauxite minerals are massive, oolitic – pisolitic textured. The Seydisehir schists could be possible parent rocks of bauxites, and have unearthed acidic source (mostly granite) with hornblende and plagioclase minerals. The schists were compositionally mature with minimal alkali feldspar sediments. The Mortas deposit is 400 m long and up to 40 m thick; it averages 10 m thick. It has about 5 million tons of ore reserves, with ~50 percent Al2O3. The Dogankuzu bauxite deposit is situated 2 km southwest of the Mortas deposit, with 14.9 million metric tons of ore at 61 percent Al2O3. The Dogankuzu ore was deposited on a fault-controlled karst surface of Cenomanian limestone succession, which was overlain by 5- to 10-cm-thick Santonian limestones. The bauxite has been mined by the Seydisehir aluminum factory, which was founded in 1973, and privatized in 2005. The plant is capable to produce 65.000 ton liquid aluminum per year, around 15% of Turkey’s Aluminum demand.

Palynofacies and palaeoenvironmental significance of the Albian – Cenomanian succession of the Epunsa-1 well, onshore Tano Basin, western Ghana

Palynofacies analysis carried out on thirty-three (33) cutting samples between the intervals 2990–5960 ft from the Epunsa-1 well onshore Tano Basin, identified three palynofacies types (P-1 to P-3). Palynofacies 1 (P-1) reflects deposition in shallow marine environment adjacent to active fluvial sources under a mud-dominated oxic (distal shelf) condition, Palynofacies 2 (P-2) was deposited in a shallow marine to fluvio-deltaic environment under a heterolithic oxic shelf condition and Palynofacies 3 (P-3) was deposited in a fluvio-deltaic environment in proximity to the source of vegetation under a dysoxic shelf condition.Visual kerogen analysis and spore colour for evaluation of hydrocarbon potential and thermal maturation respectively indicate early mature oil/gas prone to immature gas prone source rocks in the studied interval in the Epunsa-1 well.The presence of Afropollis, Classopollis, Ephedripites, and elaterate pollen as well as pteridophytic fern spores suggest a paleoenvironment with parent plants inhabiting moist biotopes or wetlands in a humid and warm coastal plain in a semi-arid/arid climate. Biostratigraphically significant elaterate pollen and associated taxa indicate Albian – Cenomanian age for the sediments.

Sequence stratigraphic architecture of marine to fluvial deposits across a passive margin (Cenomanian, Atlantic margin, Morocco, Agadir transect)

Seven sections, covering the upper Albian to lowermost Turonian, have been correlated from full-marine to continental-dominated deposits across a passive margin, along a transect 425 km long, from the present-day Atlantic coast to the ``Pre-African Trough'' between the Anti-Atlas and the High-Atlas. The thickness of the Cenomanian succession changes from around 500 metres in the fully marine sections to 250 metres in mostly continental facies in the western High-Atlas, about 150 km updip, to a few tens of metres in the Bou Tazoult area. The strata thicken again eastwards into the Pre-African Trough where they can be traced without major facies changes to the Kem Kem embayment and to the Bechar area in Algeria. Over all this eastern area, continental facies are overlain by the fully-marine shallow-water deposits of the Cenomanian-Turonian boundary interval. A first major conclusion is that fluvial aggradation in high-frequency transgressive-regressive sequences is coeval with the seaward-shift of the shoreline, in accordance with the genetic sequence stratigraphic model of GALLOWAY (1989). Both the flatness of the depositional profile and the corresponding very low energy of the marine environment during the transgressions account for the blanket of red continental clays on top of marine facies in updip depositional sequences, which is then preserved under the marine transgressive surface of the next sequence. A second major conclusion is that the high-frequency transgressive-regressive (T-R) sequences do not look like classical parasequences bounded by transgression surfaces. They usually exhibit a surface created by a sea-level fall within the regressive half-cycle. This is interpreted in the following way: regressions did not operate through a regular seaward-shift of the shoreline, but through stepped sea-level falls. The very low slope of the depositional ramp is thought to have enhanced the sequence stratigraphic record of such stepped regressions. Short-term, high-frequency sequences are organized into medium-frequency T-R sequences (seven in the Cenomanian) which show an overall aggrading and slowly retrograding pattern along the whole transect. Comparisons with other basins show that medium-frequency sequences do not fit the third-order depositional sequences described elsewhere, casting doubts about a eustatic mechanism for their deposition.