Older Strata Research Articles

Stratigraphic distribution and importance of some imperforate benthic foraminifera from the upper Campanian–Maastrichtian of the Tauride Carbonate Platform, Türkiye

Many parts of the Tauride Carbonate Platform were exposed to subaerial exposure from the Turonian to the Santonian. However, the record of the upper Campanian–Maastrichtian in shallow-marine facies is relatively continuous, except for short-term platform emergences. The present study focuses on the stratigraphic distribution and importance of some selected benthic foraminifera from the upper Campanian–Maastrichtian of the Tauride Carbonate Platform. Mainly Accordiella conica, Moncharmontia apenninica, Fleuryana adriatica, Murciella cuvillieri, Pseudocyclammina sphaeroidea, Rhapydionina liburnica and Pachycolumella acuta recorded from different parts of the TCP were studied. On a local and/or regional scale, some of these benthic foraminifera can be regarded as chronostratigraphically significant. Murciella cuvillieri, whose first occurrence is in the upper Campanian, and Rhapydionina liburnica, which has a narrow stratigraphic range (upper Maastrichtian), are two examples. Their occurrences and abundance vary throughout the upper Campanian–Maastrichtian. The presence of Accordiella conica, which is represented by a small number of specimens, and Moncharmontia apenninica, of which numerous characteristic specimens have been found, characterizes the upper Campanian strata. The upper Maastrichtian is marked by Rhapydionina liburnica, which co-exists with Pachycolumella acuta, known from the upper Maastrichtian–Paleocene interval. Murciella cuvillieri, Fleuryana adriatica, and Pseudocyclammina sphaeroidea occur throughout the upper Campanian–Maastrichtian strata. Fleuryana adriatica is represented by larger, typical specimens in the upper Maastrichtian but by smaller, atypical ones in the older strata. The stratigraphical importance of these species for the Campanian–Maastrichtian intervals in the Tauride Carbonate Platform is discussed.

A marine microvertebrate fauna from a temporary exposure of the Atherfield Clay Formation, Reigate, Surrey

A temporary exposure of the nearshore marine Atherfield Clay (Lower Greensand Formation, Aptian, Early Cretaceous) in the Reigate area (Wonham Mill) of Surrey was sampled for microvertebrate remains in Autumn 2013. Samples amounting to 858 kg of sediment were washed, dried, and sieved to 0.325 mm and the residue searched for all fossil content. This is the first definitive study of the Atherfield Clay chondrichthyan fauna of Surrey. The samples yielded teeth of hybodont sharks (Planohybodus ensis, Lonchidion breve), neoselachian sharks (Heterodontus sulcatus, Cretascyllium hassei, Protospinax sp., Protolamna sokolovi, Lamnid indet., Scyliorhinus muelleri, Scyliorhinus gen. et sp. indet., Protoscyliorhinus sp.) and batoids (Belemnobatis picteti, Squatirhina sp.). The neoselachian sharks and rays all constitute the first confident records for the various genera in the Atherfield Clay of the United Kingdom. Dermal denticles and bony fish teeth are also present in the samples, which also yielded small numbers of invertebrates (ammonite and crustacean), microcoprolites (Tomaculopsis tomaculopsis) and plant remains (fern indusia). The state of preservation of the chondrichthyan material suggests that none of the specimens are derived from older strata; the fauna is indigenous. The Surrey Atherfield Clay fauna is distinct from that recorded from the Atherfield Bone Bed on the Isle of Wight and the roughly coeval boreal fauna of the Speeton Clay.

The Cretaceous–Paleogene transition in spiny-rayed fishes: surveying “Patterson’s Gap” in the acanthomorph skeletal record

In contrast to the rich collections of articulated spiny-rayed fishes from early Late Cretaceous and Eocene Lagerstätten, similar skeletal remains are sparse in Maastrichtian–Paleocene strata. Here we coin this poorly understood span “Patterson’s Gap” and review known articulated skeletons from it, summarizing available information on their phylogenetic affinities, age, and environmental context. Roughly fifty percent of taxa in both the Maastrichtian and Paleocene come from Europe and North America, with percomorphs representing around 60% of the skeletal acanthomorph taxa in each interval. This is higher than the only pre-Maastrichtian assemblage with a reasonable sample of percomorphs, but lower than most Eocene and younger sites. Fossils from Patterson’s Gap show a steady accumulation of the principal lineages of spiny-rayed fishes. Material from Paleocene or older strata provides evidence for most of the roughly 20 major acanthomorph divisions recovered by molecular studies. Many fossils from Patterson’s Gap remain undescribed and unnamed, and almost none have been included within formal phylogenetic analyses. Revision of existing material, combined with additional fieldwork, should be a priority for future efforts seeking to clarify this murky but significant interval in the evolutionary history of a major vertebrate radiation.

Generation Time and Accumulation of Lower Paleozoic Petroleum in Sichuan and Tarim Basins Determined by Re–Os Isotopic Dating

With the targets of petroleum exploration transferred to the deep and ancient strata, abundant oil and gas resources have been found in Lower Paleozoic and older strata in central and western China. Due to complex evolutionary processes including multiple episodes of hydrocarbon accumulation and ubiquitously accompanied by secondary alterations, significant uncertainties remain concerning the generation time and accumulation processes of these revealed petroleum sources. In this paper, relative pure Re and Os elements existing in the asphaltene fractions of Lower Cambrian solid bitumen collected from the Guangyuan area, western Sichuan Basin, SW China and Middle–Lower Ordovician heavy oils in the Aiding area of the Tahe oilfield in the Tarim Basin, NW China were successfully obtained by sample pretreatments, and Re–Os isotopic analysis was subsequently carried out for the dating of these. The Re–Os isotopic composition indicates a generation time of Guangyuan bitumen to between 572 Ma and 559 Ma, corresponding to the late Sinian period of the Neoproterozoic era. By the means of Re–Os isochron aging, initial 187Os/188Os ratios, and carbon isotopic compositions, the Lower Cambrian bitumen is supposed to originate from source rocks of the Doushantuo Formation in the Sinian strata and subsequently migrated into the reservoirs of the Dengying Formation. This previously reserved petroleum was transformed into its present bitumen state by the destruction of reservoirs caused by tectonic uplift. The Re–Os dating results of Middle–Lower Ordovician heavy oil of Tarim Basin suggest that it was formed between 450 Ma to 436 Ma, corresponding to the Late Ordovician–Early Silurian system, and the generated petroleum likely migrate into the Middle–Lower Ordovician karst reservoirs to form early oil reservoirs. With tectonic uplift, these oil reservoirs were degraded and reformed to the heavy-oil reservoirs of today.

Diversity patterns of plant functional types in the Holocene of Central India: A case study on the Lonar Crater Lake pollen record

Diversity of Plant Functional Types (PFTs) along a sediment core drilled in Lonar Crater Lake, Central India, is analysed, based on previously published pollen data for a total of 115 depth levels and covering the past 9.2 kyr. Our results support concepts of a dominantly humid period persisting until ca. 5 ka, succeeded by a significantly drier phase with weaker monsoon, including various prominent drying pulses. Throughout the Holocene, plant diversity at Lonar was composed of a variable proportion of herbaceous PFTs (ca. 40–60%) and mainly angiosperm woody PFTs. Changes in herbaceous diversity account for a considerable part of the observed PFT data variability. PCA analysis reveals a total of four partly alternating diversity associations (DAs) interpretable in terms of vegetation spanning from drier Savanna and dry deciduous forest to (semi-) evergreen woody vegetation, mainly recorded in older strata. It is shown that the succession of the DAs is largely triggered by climate change inferred from other proxies. Correlation analysis with geochemical data testifies that the diversity signal obtained is largely unaffected by sedimentary processes and detrital inflow, highlighting the potential of this archive to reflect ‘true’ diversity signals, rather than artefacts of sedimentary processes. While warm and humid conditions promoted diversity, drying and weak monsoon tended to cause diversity loss. In contrast, the relative diversity of dry herbs increased during drier periods. Short-term variability in our data is evident in varying diversity percentages of single PFTs and their ratios. Changing ratios of dry on mesic herbs, the relation of shrub and tree diversity, tropical on temperate PFTs, and total plant diversity are likely related to solar cycles. Evidence for recurrent cooling episodes through solar forcing comes from the observed coincidence of Grand Solar Minima and minima in the tropical/temperate PFT ratio.

Age-Related Differences in the Role of Risk Factors for Ischemic Stroke.

Reports assessing the association of stroke risk factors with incident stroke have generally assumed a uniform magnitude of associations across the age spectrum, an assumption we assess in this report. Participants enrolled 2003-2007 in the REasons for Geographic And Racial Differences in Stroke (REGARDS) cohort study who were stroke free at baseline were followed for incident stroke. Associations of traditional stroke risk factors with incident stroke were assessed using (1) proportional hazards analysis based on the baseline age of the participant and (2) Poisson regression analysis assessing associations based on the changing age of the participant during their follow-up (age at exposure). In each analysis, age strata were selected to have a similar number of strokes in each stratum, specifically 45-64, 65-73, and 74+ years for the proportional hazards analysis and 45-69, 70-79, and 80+ years for Poisson regression. A total of 1,405 ischemic stroke events occurred among 28,235 participants over a median follow-up of 11.3 years, with a total of 276,074 person-years exposure. For both analytic approaches, the magnitude of the association with stroke was significantly less at older ages for diabetes (hazard or relative risk decreasing from ≈2.0 in younger strata to ≈1.3 in older strata), heart disease (from ≈2.0 to ≈1.3), and hypertension defined at a threshold of 140/90 mm Hg (from ≈1.80 to ≈1.50); however, there was no age-related difference in the magnitude of the association for smoking, atrial fibrillation, or left ventricular hypertrophy. Hypertension and diabetes are 2 of the more important risk factors for stroke; however, their association with stroke risk appears substantially less at older ages. That the magnitude of the association for smoking, atrial fibrillation, and left ventricular hypertrophy does not decrease with age suggests their relative importance in determining stroke risk likely increases with age.

Mud redeposition during river incision as a factor affecting authigenic 10Be/9Be dating: Early Pleistocene large mammal fossil‐bearing site Nová Vieska, eastern Danube Basin

ABSTRACTThis study examines the suitability of the authigenic 10Be/9Be dating method to the dating of the deposits of an incising river, taking as an example the Nová Vieska river terrace, which accumulated during the neotectonic inversion of the Danube Basin (western Slovakia). The succession was formed by a wandering river with minor preservation of proximal floodplain muds. The frequent occurrence of mud intraclasts reflects significant input of eroded material from underlying, older successions. The ages of 13 authigenic 10Be/9Be dating samples formed three groups: (1) samples from below the base of the river terrace yielded dates of ~4.13–3.70 Ma (including uncertainties); (2) muddy intraclasts from the river terrace gave an age range of ~2.79–1.96 Ma; and (3) in situ muddy layers had ages in the range of ~1.91–1.39 Ma. The large mammal fossil assemblage from channel thalweg deposits yielded a biostratigraphic age of ~3.6–2.2 Ma, matching the age of intraclasts, and thus emphasising the redeposited origin of those fossils. The relatively wide range of authigenic 10Be/9Be dating ages is interpreted as a result of the redeposition of mud from older strata on three scales: decimetre‐scale intraclasts, millimetre‐scale rip‐up clasts mixed into the newly formed beds, and formation of two authigenic rims with different age and 10Be/9Be records around individual particles. Considering these observations, an age range of in situ layers of ~1.91–1.39 Ma is proposed as the depositional age of the river terrace, with the most probable age falling within the most recent part of this interval. The effect of redeposition is thus shown to be potentially limiting to the application of authigenic 10Be/9Be dating to incising rivers, and stands in marked contrast to aggrading river settings, where redeposition of older sediments is limited and the degree of 10Be/9Be variability is low.

Prevalence of Staphylococcus aureus and mec-A Cassette in the Throat of Non-Hospitalized Individuals Randomly Selected in Central Italy.

Methicillin-resistant Staphylococcus aureus (MRSA) is a cause of life-threatening infections that are difficult to treat because of resistance to several antibiotics. Most documented MRSA infections are acquired nosocomially or among community with frequent contact with health facilities. However, an increasing attention to community acquired MRSA strains appears justified. A population of Central Italy was investigated for the presence of S. aureus and for the methicillin-resistance determinant mec-A gene. Exclusion was due to systemic diseases, pathologies or therapies inducing systemic immunosuppression, facial trauma or poor oral hygiene. Throat swabs obtained from 861 randomly selected participants were tested for the presence of DNA sequences of S. aureus and the mec-A gene by real-time PCR. The DNA of S. aureus was detected in 199 specimens (23.1%), while the mec-A gene was detected in 27 samples (3.1%). The prevalence of patients carrying methicillin-resistant strains was higher in younger and older strata. The prevalence of mec-A among S. aureus positive samples was 7.5%. Our data confirm that S. aureus and methicillin-resistant strains are common in the throat of the general population of Central Italy. Although the PCR methods used in this study are different from traditional culture-based approaches, the observed prevalence was consistent to those observed in Italians and other populations. Considering that carriers have a higher risk to develop post surgically life-threatening infections, it is worth evaluating a preventive approach based on rapid PCR screening of incoming patients to reduce the risk of developing health-care-associated infections.

Scleractinian corals from the Lower Cretaceous of the Alpstein area (Anthozoa; Vitznau Marl; lower Valanginian) and a preliminary comparison with contemporaneous coral assemblages

From the Vitznau Marl (lower Valanginian) at the locality Wart in northeastern Switzerland (Alpstein area), 18 species from 17 genera and 13 families are described, including the genera Actinaraea, Actinastrea, Adelocoenia, Aplosmilia, Axosmilia, Complexastrea, Cyathophora, Dermosmilia, Fungiastraea, Heterocoenia, Latiastrea, Montlivaltia, Placophyllia, Pleurophyllia, Stylophyllopsis, Thamnoseris, and specimens showing affinities to solitary stylophyllids. The corals from the Vitznau Marl were derived from a limestone–marl alternation that is fossiliferous and clay-rich at the base (Vitznau Marl), containing crinoids, bryozoans, and sparse reworked corals and sponges. The coral fauna is distinctly dominated by forms belonging to the category of lowest to no polyp integration (50%), followed by species of the cerioid-plocoid group (33%) and forms having the highest polyp integration (thamnasterioid; 17%). With regard to polypar size, the Wart fauna is dominated by corals having large-size (> 9 mm) polyps (= 39%), followed by corals having medium- (> 2.5‒9 mm; 33%) and small-size polyps (up to 2.5 mm; 28%). Based on morphological features, the fauna from the Vitznau Marl closely corresponds to coral assemblages that are subjected to near-chronic, moderate sediment-turbidity stress that is punctuated by high-stress events, and that are largely or entirely heterotrophic. No coral fabric was observed that would suggest a biohermal development. But in a very small number of places, structures are present which might be fragments of crusts of microbialites, pointing to the hypothesis that at least a few of the corals might have been a part of some kind of bioconstruction. At the species-level, the fauna of the Vitznau Marl shows either no or very little affinities to other Valanginian assemblages such as to the fauna of Hungary (4.3%), followed by the associations of Ukraine, Switzerland (non-Vitznau), Spain (SpII), and Bulgaria. At the genus-level, the Wart fauna shows low correspondence to the fauna of Spain (SpII) (14.5%), followed by the assemblages of Hungary, Bulgaria, and Ukraine. In addition to the Vitznau Marl corals, an account of all Valanginian coral faunas published before early 2021 is given, including their paleogeographic distribution, as well as their taxonomic and morphological characterization. For this preliminary study, a total of 206 coral species belonging to 97 genera found in the coral assemblages of the Valanginian were included. At both the genus- and the species-levels, colonial taxa are most abundant (colonial genera: 89%; colonial species 90%). The vast majority of the Valanginian genera already occurred in older strata. Only 11 genera (out of 97 = 11%) are newly recorded. The Valanginian faunas having the largest number of solitary taxa lived in both (sub-) paratropical to warm-temperate areas, and in arid regions. The coral faunas of the Valanginian are distinctly dominated by corals of well-established microstructural groups. Only 13% of the species from 24% of the genera belong to “modern” groups. Compared to the situation in the Berriasian which showed that 9% of the species and 17% of the genera belonged to modern microstructural groups, the occurrence of “modern” groups significantly increased during the Valanginian.

Fine-grained carbonate formation and organic matter enrichment in an Eocene saline rift lake (Qianjiang Depression): Constraints from depositional environment and material source

Carbonate-rich fine-grained rocks in saline lakes have become potential targets for shale oil and gas exploration. However, few studies have investigated the processes of carbonate formation and organic matter enrichment in hypersaline environments. The Qianjiang Depression is a hypersaline rift lake basin that contains carbonate-rich fine-grained rocks in the inter-salt strata of the Qianjiang Formation. In this study, sedimentological observations and multiple geochemical analyses were conducted on the inter-salt strata in the sixth and eighteenth rhythmites of the Qianjiang 4 Member. The results showed that the middle inter-salt stratum in the sixth rhythmite is rich in dolomite, calcite, and organic matter, whereas the inter-salt stratum in the eighteenth rhythmite is rich in dolomite and sulfate minerals and low in organic matter. Comparisons among multiple redox parameters revealed that the middle inter-salt stratum in the sixth rhythmite was formed in a deep saline lake, while the inter-salt stratum in the eighteenth rhythmite was formed in a shallow saline lake. Further, sedimentary observations and analyses of δ34S and trace and rare-earth elements revealed that the inter-salt stratum in the sixth rhythmite contained a significant amount of volcanic ash, whereas that in the eighteenth rhythmite was influenced by hot brine derived from older strata. Therefore, the differing environments and material inputs notably affected the carbonate crystallization and organic matter enrichment in these strata. This study suggests that the input of volcanic materials is conducive to improving biological productivity in saline lakes, and anoxic conditions with moderate salinity are conducive to the preservation of organic matter. These findings provide theoretical guidance for future self-sourced inter-salt shale oil reservoir explorations.

Structural Reservoir Characterization of Akkas Gas Field, Western Iraq: Implications for Hydrocarbon Recovery

Akkas Field is a structural trap with a sandstone reservoir that contains proven gas condensate. The field is a faulted anticline that consists of the Ordovician Khabour Formation. The objective of this research is to use structural reservoir characterization for hydrocarbon recovery. The stratigraphic sequence of the Silurian and older strata was subjected to an uplift that developed a gentle NW-SE trending anticline. The uplifting and folding events developed micro-fractures represented by tension cracks. These microfractures, whether they are outer arc or release fractures, are parallel to the hinge line of the anticline and perpendicular to the bedding planes. The brittle sandstone layers of the reservoir are interbedded with ductile units of shale. The sandstone layers accommodate the formation of micro fractures that play a major role to increase the secondary porosity. The gas and condensate have been stored mainly through the micro fractures. Two types of drilling have been used for experimental gas production, vertical and horizontal. Horizontal drilling was parallel to both hinge line of the anticline and micro fracture surfaces that was conducted and doubled the gas production of the vertical well multiple times. However, if used the third type of drilling, directional, that is perpendicular to the hinge line and parallel to the beddings of both flanks of the anticline gas production will increase more than the horizontal drilling. The directional drilling will become perpendicular to the fracture surfaces and allow the gas and the condensate to flow into the well from all directions. Additionally, it will reduce the effect of both semi – liquid hydrocarbon condensate and vertical sediment barriers.

Cerebrovascular Risk Profiles in a Saudi Arabian Cohort of Young Stroke Patients.

Background: The constantly increasing incidence of stroke in younger individuals substantiates an urgent need for research to elucidate underlying risk factors and etiologies. Heretofore, the vast majority of studies on stroke in the young have been carried out in European and North American regions. We aimed to characterize cerebrovascular risk profiles in a Saudi Arabic cohort of consecutive young stroke patients.Methods: We retrospectively analyzed data from consecutive ischemic stroke patients aged 15 to 49 years who underwent detailed cardiocerebrovascular evaluation at a tertiary stroke care center in Makkah, Saudi Arabia. Distributions of risk factors and stroke etiologies were assessed in the entire cohort and in two strata of very young (15–40 years) and young to middle-aged patients (41–49) to account for variability in suggested age cutoffs.Results: In the entire cohort [n = 63, ages 44 (34–47) median, interquartile range], dyslipidemia (71.4%) and small vessel occlusion (31.7%) displayed highest prevalence followed by diabetes (52.4%) and cardioembolism (19%). In very young patients, cardioembolism was the most prevalent etiology (27.3%). Risk profiles were similar between both age strata except for a higher prevalence of diabetes among the older cohort (31.8 vs. 63.4%, p = 0.01). Logistic regression identified diabetes as strongest predictor for association to the older strata (odds ratio = 4.2, 95% confidence interval = 1.2–14.1, p = 0.02).Conclusion: Cerebrovascular risk profiles and stroke etiologies in our cohort of young stroke patients differ from those of previous cohorts, suggesting the need for tailored prevention strategies that take into account local epidemiological data on cerebrovascular health.

Geometric morphometrics and anatomical network analyses reveal ecospace partitioning among geoemydid turtles from the Uinta Formation, Utah.

We present new fossil records of the geoemydid turtle Bridgeremys pusilla from the Uinta Formation of Utah. Turtles are abundant throughout the unit, and known taxa are similar to those from the older strata in the Upper Green River Basin in Wyoming from the Bridger and Washakie Formations. B. pusilla is known from Bridgerian deposits but was not previously known from after the Turtle Bluff Member of the Bridger Formation. The taxon was coveal with two species of the geoemydid Echmatemys (E. callopyge and E. wyomingensis), a common genus of extinct pond turtles known primarily from lacustrine and fluvial deposits in western North America, including the Uinta Basin. In addition to previously documented morphological differences, our geometric morphometric analyses revealed significant differences in epiplastral morphology between B. pusilla and the two coeval Echmatemys species. Bridgeremys pusilla shared several morphological characters with Testudinidae. However, our anatomical network analysis suggests that the carapace of B. pusilla distributed stress forces in a manner more similar to emydids (basal and derived) than to derived testudinoids (Testudinidae and Emydidae), including Echmatemys species. This finding changes our understanding of the ecology of the species and sheds light onto how geoemydid turtles of the Uinta Formation may have partitioned the available ecospace. These new Uintan records extend the geographic range of B. pusilla into the Uinta Basin and stratigraphically through the top of the Uinta Formation, extending the temporal range of the taxon by more than 4 million years through the Uintan North American Land Mammal Age to the base of the Duchesne River Formation.

Phylogeny and sex chromosome evolution of Palaeognathae

Many paleognaths (ratites and tinamous) have a pair of homomorphic ZW sex chromosomes in contrast to the highly differentiated sex chromosomes of most other birds. To understand the evolutionary causes for the different tempos of sex chromosome evolution, we produced female genomes of 12 paleognathous species and reconstructed the phylogeny and the evolutionary history of paleognathous sex chromosomes. We uncovered that Palaeognathae sex chromosomes had undergone stepwise recombination suppression and formed a pattern of “evolutionary strata”. Nine of the 15 studied species' sex chromosomes have maintained homologous recombination in their long pseudoautosomal regions extending more than half of the entire chromosome length. We found that in the older strata, the W chromosome suffered more serious functional gene loss. Their homologous Z-linked regions, compared with other genomic regions, have produced an excess of species-specific autosomal duplicated genes that evolved female-specific expression, in contrast to their broadly expressed progenitors. We speculate such “defeminization” of Z chromosome with underrepresentation of female-biased genes and slow divergence of sex chromosomes of paleognaths might be related to their distinctive mode of sexual selection targeting females rather than males, which evolved in their common ancestors.

A Late Devonian refugium for Colpodexylon (Lycopsida) at high latitude

Localities within strata of the Witpoort Formation (Witteberg Group, Cape Supergroup) of South Africa provide diverse new fossil material of Famennian plants from a high palaeolatitude marginal marine setting. Lycopsid axes with sterile leaves include material here diagnosed to two new species of Colpodexylon Banks 1944. C. pullumpedes sp. nov. from Waterloo Farm is a ‘short-tipped’ species, whereas C. mergae sp. nov. from Coombs Hill, is a ‘long-tipped’ species. The latter has leaves similar to those of the type species, C. deatsii Banks, yet differing in proportions. This provides the first definite high latitude records of the genus. Furthermore, these occurrences substantially extend the temporal range of Colpodexylon, formerly only known from lower Frasnian and older strata, indicating that the genus persisted at high-latitudes after its apparent disappearance from the palaeo-sub-tropics.

Lower Cambrian (Series 2) small shelly fossils from along Nares Strait (Nunavut and Greenland; Laurentia)

Three small assemblages of lower Cambrian (Cambrian Series 2, Stage 4) small shelly fossils are described from Laurentian strata astride Nares Strait. The fauna from the Humboldt Formation of Daugaard-Jensen Land, North Greenland, is derived from inner shelf sediments deposited on the stable craton of the Inglefield Land High. Fossils from Judge Daly Promontory, eastern Ellesmere Island, Nunavut, occur in strata of the Cambrian Ellesmere Group (Kane Basin Formation) that have been structurally juxtaposed against older strata; they were originally assigned to the Kennedy Channel Formation, which is now considered to be of Neoproterozoic age. A similar fauna from offshore environments of the Aftenstjernesø Formation in northern Nyeboe Land, North Greenland, reflects the regional structural and sedimentological continuity with the Canadian Cambrian succession. Pojetaia robsonae sp. nov. is described from Judge Daly Promontory.

A large Middle Devonian eubrachythoracid \u2018placoderm\u2019 (Arthrodira) jaw from northern Gondwana

For the understanding of the evolution of jawed vertebrates and jaws and teeth, ‘placoderms’ are crucial as they exhibit an impressive morphological disparity associated with the early stages of this process. The Devonian of Morocco is famous for its rich occurrences of arthrodire ‘placoderms’. While Late Devonian strata are rich in arthrodire remains, they are less common in older strata. Here, we describe a large tooth-bearing jaw element of Leptodontichthys ziregensis gen. et sp. nov., an eubrachythoracid arthrodire from the Middle Devonian of Morocco. This species is based on a large posterior superognathal with a strong dentition. The jawbone displays features considered synapomorphies of Late Devonian eubrachythoracid arthrodires, with one posterior and one lateral row of conical teeth oriented postero-lingually. μCT-images reveal internal structures including pulp cavities and dentinous tissues. The posterior orientation of the teeth and the traces of a putative occlusal contact on the lingual side of the bone imply that these teeth were hardly used for feeding. Similar to Compagopiscis and Plourdosteus, functional teeth were possibly present during an earlier developmental stage and have been worn entirely. The morphological features of the jaw element suggest a close relationship with plourdosteids. Its size implies that the animal was rather large.

Using characteristics of pressure-temperature induced permeability variation of typical carbonate rock to determine its performance as reservoir or cap rock

The current research on carbonate rock often focuses on the storage space for oil and gas, and exploration of carbonate rock in petroliferous basins also mainly searches for high-quality reservoir rock for hydrocarbons. However, the importance of effective carbonate reservoir-cap rock configuration is increasingly highlighted, as hydrocarbon exploration advances towards deeper and older strata. Exploration practice shows that the favorable facies belt of carbonate rock, though deeply buried, still develops highly desirable reservoir rock with high porosity and permeability. Therefore, the presence of an effective carbonate cap rock collaborating with this reservoir rock becomes key to hydrocarbon exploration in deep carbonate rock. This research, for the first time, systematically and thoroughly carries out permeability measurement through the whole triaxial compression process of typical carbonate rock at varied temperatures, and captures the permeability evolution during deformation and failure, affected by temperatures and confining pressures. Test results show that typical dolomite and limestone present varied permeability variation characteristics in a triaxial loading state. Dolomite appears to be more of reservoir rock. It presents higher critical confining pressure for brittle–ductile transition, and is more prone to fracturing. Its permeability grows with temperature elevation. As for limestone, it has better performance as cap rock, which is embodied as the lower critical confining pressure for brittle–ductile transition, high sealing capacity, and permeability reduction with elevated temperatures. To sum up, vertical stacking of dolomite and limestone can form an effective reservoir-cap rock assemblage for hydrocarbon accumulation.

Geologic-geochemical and modelling studies of hydrocarbon migration in the South Caspian basin

Based on pyrolysis data an overview is given on the generative potential and maturity of individual stratigraphic units in the South Caspian sedimentary cover. Furthermore, the pyrolysis analyses indicate that the Lower Pliocene Productive Series being immature itself is likely to have received hydrocarbon charge from the underlying older strata. The present state of the art in studying hydrocarbon migration and the "source-accumulation" type relationship between source sediments and reservoired oils in the South Caspian basin are touched upon. The views of and geochemical arguments by different authors for charging the Lower Pliocene Productive Series reservoirs with hydrocarbons from the underlying Oligocene-Miocene source layers are presented. Quantitative aspects of hydrocarbon generation, fluid dynamics, and formation of anomalous temperature & pressure fields based on the results of basin modelling in Azerbaijan are considered. Based on geochemical data analysis and modelling studies, as well as honouring reports by other workers the importance and necessity of upward migration for hydrocarbon transfer from deep generation centers to reservoirs of the Productive Series are shown.

Genesis of the Heneshk IOCG deposit, Iran: magnetite mineral chemistry and sulfur isotope

The Heneshk Fe ± Cu deposit, a metamorphosed IOCG (Iron Oxide Copper Gold) is situated in Sanandaj-Sirjan Zone, SW Iran. Mineralization occurs as two stratabound ‘U’ shape ore bodies, hosted by a meta-dolomite member of a metamorphic complex. The ore and gangue minerals comprise magnetite, chalcopyrite, hematite, martite, mushketovite, pyrite, barite, calcite, dolomite, and quartz. The successive mineral assemblage formed in the five paragenetic stages (I to V) during an ongoing deformation regime from the plastic to the brittle deformation regime. The mineralization stages comprise stage I, III, and IV. Stage I–III and IV formed in the plastic and the brittle deformation regime by the metamorphic processes in a shear zone, respectively. The concomitant alteration products of these stages comprise sodic, Fe, K, hydrolytic and silicification. The sodic and Fe alterations occur as a pre-mineralization stage and each mineralization stage is accompanied by K and hydrolytic alterations. A late barite-calcite-quartz assemblage (stage V) overprinted on the previous stages (I to IV). Stage I mineralization formed at a depth of ~10 km and temperature of ~300 °C (a high pressure-low temperature environment). The partitioning and substitution of the Mg, Al, Ti, Ni, Cr, Mn, Si, and Zn elements increased in this relatively higher pressure environment cause of the highest concentrations of the Al, Ti, Ni, Cr, and Zn, in comparison with metamorphic magnetite. The mineral chemistry of the Heneshk magnetite (average elemental concentrations) is in accordance with the metamorphic magnetite and can consider as a pure magnetite with the low elemental concentration. Also, the $${{\rm{\delta }}^{34}}{S_{{H_2}S}}$$ Heneshk mineralized fluid ranges between 39.8 to 40.6‰, indicating the contribution of the paleo-evaporates. The pleo-evaporates leached from the older strata during metamorphism, and their precipitation in the form of the sulfide minerals occurs through the TSR (Thermochemical Sulfate Reduction) mechanism.