Age Assignment Research Articles

New mammals from the Naskal intertrappean site and the age of India’s earliest eutherians

The first Cretaceous mammals described from India were recovered from the Naskal locality, on the southeastern edge of the Deccan Traps Volcanic Province (DTVP), where it is preserved between two basalt flows. Because the DTVP eruptions spanned the Cretaceous-Paleogene boundary (KPB), it is often unknown whether trap-associated fossil sites are latest Cretaceous (Maastrichtian) or early Paleocene in age. The Naskal locality accounts for nearly half of published mammal records from DTVP-associated sediments as well as a host of other vertebrate microfossils. Its age takes on singular importance in the context of mammalian evolution in India and the effects of the end-Cretaceous mass extinction and subsequent evolutionary radiation of placentals. Here we describe two new mammal species, Indoclemensia naskalensis gen. et sp. nov. and I. magnus sp. nov., from Naskal and present evidence from 40 Ar/ 39 Ar geochronology, magnetostratigraphy, and chemostratigraphy of the over- and underlying basalt flows to refine the age of the Naskal locality and nearby Rangapur locality. In conjunction with palynostratigraphy and vertebrate biostratigraphy, these sites can be confidently restricted to a <100 kyr interval spanning the KPB. The most probable 40 Ar/ 39 Ar age is latest Cretaceous (66.136–66.056 Ma), but an earliest Paleogene age cannot be ruled out. We explore the implications of this age assignment for Deccan chemostratigraphy and Deccan volcanism, Cretaceous-Paleogene (K/Pg) mass extinction, Indian mammalian faunal evolution, and the timing of the origin of placental mammals. • New 40 Ar/ 39 Ar geochronology, magnetostratigraphy, chemostratigraphy, and palynofloras from the Naskal and Rangapur sites. • Age of Naskal and Rangapur are likely Maastrichtian, constrained to within 100 kyr of the Cretaceous-Paleogene boundary. • Two new eutherian mammal species from the Naskal site of India are described. • These sites are ‘transitional’ distinctive in biotic composition from older and younger infra - and intertrappean localities.

Enhancing the reliability of the magnetostratigraphic age assignment of azimuthally nonoriented drill cores by the integrated application of palaeomagnetic analysis, field tests, anisotropy of magnetic susceptibility, and the evolution of the endemic fauna as documented on the upper Miocene limnic deposits of the Turiec Basin (Western Carpathians)

Enhancing the reliability of the magnetostratigraphic age assignment of azimuthally nonoriented drill cores by the integrated application of palaeomagnetic analysis, field tests, anisotropy of magnetic susceptibility, and the evolution of the endemic fauna as documented on the upper Miocene limnic deposits of the Turiec Basin (Western Carpathians)

Abstract P080: Health-related Quality Of Life Predictors Of Exercise Intervention Dropout

Introduction: Though many individuals know the health benefits of participating in exercise, few report sufficient activity to meet the US 2018 Physical Activity Guidelines. Current research assessing predictors of exercise adherence and dropout has primarily focused on cognitive factors, physiological factors, and demographic characteristics. The purpose of this analysis was to determine if baseline self-rated HrQoL measures are predictive of dropout from an exercise intervention across two STRRIDE trials. Methods: A total of 444 adults with dyslipidemia (STRRIDE AT/RT) or prediabetes (STRRIDE-PD) were randomized to one of seven exercise interventions, ranging from doses of 10-16 kcal/kg/week (KKW); intensities of 50-75% V̇O 2peak ; and durations of 6-9 months. Six groups included aerobic exercise, two groups included resistance training, and one group included dietary intervention (weight loss goal of 7%). Dropout was defined as a participant who did not complete the exercise intervention due to one or more of several reported reasons (e.g., time, motivation, re-occurring injury). Backwards stepwise logistic regression determined significant baseline HrQoL predictors of exercise intervention dropout, while controlling for age, sex, race, and intervention group assignment. Results: A total of 117 individuals were classified as being exercise intervention dropouts (STRRIDE AT/RT: n=55; STRRIDE-PD: n=62). In STRRIDE AT/RT, the logistic regression identified baseline sleep quality, sleep latency, sleep efficiency, sleep disturbance, bodily pain, and social functioning scores as predictors of dropout (R 2 =0.39). In STRRIDE-PD, the logistic regression identified baseline role-emotional, satisfaction with appearance, and physical component scores as predictors of dropout (R 2 =0.08). Conclusion: Among individuals with dyslipidemia, baseline HrQoL measures were able to explain about 39% of the variance in dropout from an exercise intervention, with primarily sleep measures, bodily pain, and social functioning being identified as important predictors of dropout. In contrast, among individuals farther along the disease spectrum, with prediabetes, baseline HrQoL measures only explained about 8% of the variance in dropout, with emotional well-being, perceived appearance, and physical function being important predictors of dropout. Future research should investigate molecular and biological predictors of dropout in combination with HrQoL, physiological, cognitive, and demographic factors to improve predictive power.

Abstract P100: Changes In Adiponectin But Not Tnfα Predict Changes In Insulin Sensitivity Following Health Behavior Intervention Among Latino Youth

Background: Pediatric obesity is characterized by an imbalance in pro- and anti-inflammatory markers that are associated with cardiometabolic diseases. Adiponectin (Adpn), an anti-inflammatory marker, is associated with insulin sensitivity, while tumor necrosis factor-alpha (TNFα) has been associated with insulin resistance among youth with obesity. However, it is unknown whether longitudinal changes in Adpn or TNFα predict changes in insulin sensitivity among high-risk youth. Methods: A total of 73 Latino youth with obesity (age 13.3±1.4 y, Female 40.3%, BMIz 2.2±0.3) were enrolled in either a lifestyle intervention or usual care. Given that there were no between-group differences in changes in insulin sensitivity at 6-months, groups were combined for the present analysis. Fasting serum samples were used to measure high-molecular weight Adpn and TNFα before and after intervention. Insulin sensitivity was estimated by the whole-body insulin sensitivity index (WBISI) using insulin and glucose concentrations from a 75-g, 2-h oral glucose tolerance test. Baseline associations were analyzed using Pearson correlations. Linear regression was used to analyze whether changes in Adpn or TNFα predict changes in WBISI, adjusting for age, sex, and intervention assignment. Data from linear regressions are presented as betas (β) and standard errors (SE). Results: At baseline, WBISI was positively and significantly associated with Adpn (r=0.296, p=0.015) but not with TNFα (r=-0.171, p=0.168), adjusting for age and sex. Increases in Adpn were associated with increases in WBISI, whereby for every 1 μg/dL increase in Adpn, there was a 0.7 unit increase in WBISI (SE=0.3, p=0.027). Changes in TNFα did not significantly predict changes in WBISI (β=0.1, SE=0.5, p=0.915). Conclusion: Changes in Adpn but not TNFα were associated with changes in insulin sensitivity following intervention among Latino youth with obesity. Whether Adpn is the mechanism by which health behavior changes increase insulin sensitivity warrants further investigation among high-risk youth populations.

DEVELOPING BEST PRACTICE IN MICROPALAEONTOLOGY: EXAMPLES FROM THE MID-CRETACEOUS OF THE ZAGROS MOUNTAINS

Micropalaeontological studies can provide important information on how strata correlate, age calibration, palaeoenvironmental determination, palaeobiology, evolutionary relationships of the taxa being studied, palaeogeography, and the recognition of global or regional geological events in a local succession. However, the value of micropalaeontological studies is constrained by the accuracy with which taxa are identified, the accuracy of their age interpretation, and the use of up-to-date taxonomic concepts, supported by modern research literature. Best practice implies attention to these and other details, which we illustrate with reference to published research on larger benthic foraminifera (especially orbitolinids) from the mid-Cretaceous succession of the Zagros Mountains in the Middle East. It is demonstrated that whilst there are many excellent studies, a significant number could offer more value if they were to use precise, modern taxonomic concepts applied to well-illustrated and documented unequivocal material. Poorly founded age assignments and misidentifications can lead to confusion on assessment of true stratigraphic ranges and evolutionary patterns. Moreover, they can lead to miscorrelation and erroneous modelling of the subsurface in a hydrocarbon-rich region. Integrated studies of larger benthic foraminifera with other age-diagnostic fossil groups or chemostratigraphic methods would further enhance their utility. These recommendations are applicable to micropalaeontological studies on microfossils of any type and age, from any part of the world, but we hope will promote additional rigour in studies on the micropalaeontology of the Mesozoic and Cenozoic succession of the Zagros that still have much to impart.

High annual survival suggested by size structure of Kemp’s ridley sea turtles captured by coastal research trawling in the Northwest Atlantic Ocean since 1990

Abundance of Kemp’s ridley sea turtle Lepidochelys kempii Garman, 1880 in the Northwest Atlantic Ocean (NWA) is far less than in the Gulf of Mexico (GOM), but encounters of this species in the NWA have increased in recent decades. Consequently, improved opportunity exists to evaluate population structure, which is of particular interest given suggestions of renewed decline in annual survival rates in the GOM. Here we use size structure for Kemp’s ridley sea turtles captured (n = 617) by research trawling in the South Atlantic Bight (SAB) to assess survival since 1990 following age assignment using recently published size-at-age keys. With limited exception, the ratio of older (≥age 10) to younger (ages 1 to 9) sea turtles captured randomly was overwhelmingly stable and best aligned with high (≥0.9) annual neritic survival in theoretical models with fixed annual hatchling (H) recruitment. When annual H recruitment reflected exponential increase in H production since 1985, following low and generally stable production between 1966 and 1984, reduced H emigration proportion from the GOM to NWA and further increase in annual neritic survival were required to achieve the size/age structure reported for in-water data. Stepwise regression using monthly values for 5 climate indices simulated (adj. r2 = 0.77) proportionate annual H decline, which better explained observed survey size/age structure than climate-based prediction (adj. r2 = 1.00) of published particle emigration rates. Temporal decline in proportionate H recruitment to the NWA should increase retention of juveniles in the GOM to further enhance multi-generational population rebuilding.

Middle–Late Ordovician chitinozoans from Songliang of Qiaojia, western South China, and their biostratigraphic implications

Ordovician chitinozoans are as yet inadequately documented from the western Yangtze Platform, South China. Here we present a systematic study on chitinozoans from a Middle–Upper Ordovician succession at Songliang of Qiaojia, northestern Yunnan, southwestern China. Altogether 34 species of 12 genera are identified from the upper Hungshihyen and the Huadan formations. The top of the Hungshihyen Formation yields typical Early and Middle Ordovician forms, for instance, Lagenochitina obeligis and Belonechitina chenjiawuensis, with the latter only known from the lower Darriwilian in South China, thus suggesting an early Darriwilian age for this interval. The chitinozoans recovered from the Huadan Formation include Lagenochitina prussica and Spinachitina fossensis, both are mainly confined in Katian and sometimes ranging into younger strata. This indicates an age younger than the middle to late Darriwilian previously determined for the Huadan Formation. However, conflicts exist in age assignment of the Huadan Formation based on chitinozoan and other evidence, and further work is required.

Palynological and sedimentological implications of the sauropterygian Upper Triassic site of El Atance (Central Iberian Peninsula)

This study presents new palynological and sedimentological data concerning the Upper Triassic outcrop El Atance (Guadalajara province, Spain). This fossil site has provided a unique and unprecedented concentration of reptile skeletons from the Late Triassic in the Iberian Peninsula, which are almost complete, articulated and preserved in three dimensions. It is the type locality of the simosaurid nothosauroid Paludidraco multidentatus and the henodontid placodont Parahenodus atancensis, being the only species of these clades represented with some certainty in the Iberian record.Although these reptiles are often linked to shallow marine environments, little is known about the sedimentary environment where they became fossilized. Furthermore, to compare these remains with those from other areas of Europe, greater precision in their age assignment is necessary.The new palynological data provided in this study allows us to assign a precise age, in addition to other data such as a probable plant community, palaeoecology, and palaeoclimatic conditions. This information together with the geological and sedimentological data and the new isolated sauropterygian remains studied, allow a better understanding of the local palaeogeography and the evolutionary history of the vertebrates found in the El Atance fossil site.

The K-Pg boundary section at Nasiłów, Poland: stratigraphic reassessment based on foraminifers, dinoflagellate cysts and palaeomagnetism

The Nasiłów section represents the uppermost part of the Middle Vistula River section, a classical Polish extra-Carpathian Cretaceous section, and gives access to the Cretaceous–Paleogene (K-Pg) boundary interval. Despite many papers that have been published so far, our newly collected data shed new light on the completeness of biostratigraphic and sedimentary records of the K-Pg at that site. The Nasiłów section encompasses the upper Maastrichtian regional XII and XIII foraminiferal assemblage zones and the lower Danian P0?-Pα standard planktonic foraminiferal zones. The K-Pg boundary is placed at the top of a phosphatic layer. The grey marly chalk unit, never before subjected to examination of biostratigraphically important taxa, displays blooms of guembelitrids pointing to the uppermost Maastrichtian (XIII foraminiferal assemblage Zone) as well as of planktonic and benthic foraminifers of a reduced test size. Such foraminiferal dwarfism is commonly observed near the end of the Cretaceous and interpreted as a response to the Deccan volcanism (possible 2nd phase) that caused climate changes and ocean acidification. The terminal Maastrichtian age of the marly chalk unit is additionally supported by an acme of the dinoflagellate cyst Palinodinium grallator , together with Tallasiphora pelagica and Disphaerogena carposphaeropsis . The “Greensand”, a distinct glauconite-quartz sand unit, contains exclusively terminal Maastrichtian planktonic foraminifers and dinoflagellate cyst assemblages. Individual specimens of Danian age are interpreted to be either an effect of contamination or were translocated down by burrowers into the Greensand. The lowermost portion of the Siwak (informal lithostratigraphic unit) demonstrates an early Danian age based on the co-occurrence of the common planktonic foraminifers Globoconusa daubjergensis, Guembelitria cretacea, Muricohedbergella monmouthensis, M. planispira, Planoheterohelix globulosa, Parvularuglobigerina extensa and P. alabamensis . The last occurrence of Palynodinium grallator and the first occurrences of Carptella cornuta and Senoniasphaera inornata , recorded directly above the phosphatic layer, support the same age assignment. The new palaeomagnetic data cannot prove remagnetization at the boundary interval, in contrast to previous research which gave support to a hiatus in the critical interval

Implementing the Dubowitz assessment of gestational age in India and Malawi: a cross-sectional study of participants in a training workshop

Background Accurate assignment of the gestational age of newborns is important for the identification of prematurity. The Dubowitz assessment is the gold standard among postnatal examinations used to assign gestational age, but implementation has been limited because of examination complexity and training requirements. The objective of this study was to explore factors related to teaching and implementing the Dubowitz examination that may influence its uptake in India and Malawi. Methods This cross-sectional study was conducted in India and Malawi during the preparation for a low-birthweight infant feeding exploratory study. Twenty trainees participated in a Dubowitz examination training workshop that occurred over two half-day sessions. Trainees completed pretraining and posttraining surveys related to their perceptions of the Dubowitz training, the examination, and factors affecting the administration of the examination in their setting. Results All survey respondents expressed confidence in their ability to perform the Dubowitz examination after the training. Less than a third expressed concerns about the time required to learn (30%) or perform the examination (25%). Eighty-five percent of trainees identified concerns related to parental perception of the examination that may inhibit implementation. Trainees averaged 14 minutes (standard deviation: 4.5 minutes) to complete the examination. More than 80% of trainee answers were within one point of the trainer for 16 of the 22 Dubowitz signs. Trainee composite scores were within ±3 weeks of the trainer for 95% of assessments based on Bland-Altman analysis. Conclusions The Dubowitz examination at birth is a method to improve identification of premature infants in the absence of prenatal dating. We found widespread acceptance for the Dubowitz assessment among participants in training workshops in India and Malawi, despite the complexity and length of the examination. The high level of trainee-trainer concordance on individual examination signs suggests that an acceptable level of competence is feasible after a short, concentrated workshop. Further investigation into barriers that hinder implementation such as negative parental perceptions is warranted. Registration details Clinical Trials Registration: NCT04002908 (www.clinicaltrials.gov) and CTRI/2019/02/017475 (Clinical Trial Registry of India - http://ctri.nic.in).

Palynology of a short sequence of the Lower Devonian Beartooth Butte Formation at Cottonwood Canyon (Wyoming): age, depositional environments and plant diversity

AbstractThe Beartooth Butte Formation hosts the most extensive Early Devonian macroflora of western North America. The age of the flora at Cottonwood Canyon (Wyoming) has been constrained to the Lochkovian–Pragian interval, based on fish biostratigraphy and unpublished palynological data. We present a detailed palynological analysis of the plant‐bearing layers at Cottonwood Canyon. The palynomorphs consist of 32 spore, five cryptospore, two prasinophycean algae and an acritarch species. The stratigraphic ranges of these palynomorphs indicate a late Lochkovian or Pragian age, confirming previous age assignments. Analysis of samples from three different depositional environments of the plant‐bearing sequence (layers with in situ lycophyte populations, flood layers that buried those populations and an organic matter accumulation zone within a flood layer) demonstrate distinct palynofacies. Comparisons between palynomorph and plant macrofossil diversity reveal some discrepancies. Whereas zosterophylls and lycophytes, most diverse and abundant among the macrofossils, have only one known corresponding spore type (assignable to zosterophylls) in the palynomorph assemblage, the trimerophytes, rare in the macrofossil assemblage, are represented by three spore types. Some of these discrepancies reflect taphonomic differences between the macrofossils and palynomorphs, while others could be due to the fact that the parent plants of most palynomorph types in the Cottonwood Canyon assemblage are unknown. These observations emphasize the need for concerted efforts to bring together the knowledge of macro‐ and microfloras within Early Devonian localities. Nevertheless, given the palaeophytogeographic significance of the Beartooth Butte Formation flora, its palynofossil and macrofossil assemblages, taken together, provide new data relevant to future discussions of Early Devonian biogeography.

Latest Jurassic–Early Cretaceous synrift evolution of the Torrelapaja Subbasin (Cameros Basin): implications for Northeast Iberia palaeogeography

The reconstruction of the latest Jurassic–Early Cretaceous evolution of the Torrelapaja Subbasin (Cameros Basin, Spain) resulted in the characterization of three synrift sequences (SS-1, SS-2 and SS-3) bounded by major unconformities. Three major NW–SE normal faults combined with smaller scale faults of variable direction (around NE–SW) controlled the sedimentation. The complex geometry of the Torrelapaja Subbasin indicates a main extension direction of NE–SW, and a secondary NW–SE extension. Sedimentation of the Tithonian–middle Berriasian SS-1 occurred in alluvial fan systems, grading upwards to carbonate palustrine-lacustrine environments. A new vertebrate site with large size sauropod bones has been found in the middle part of SS-1. The lower boundary of the uppermost Hauterivian–lower Barremian SS-2 is locally a palaeokarst, with sedimentary infill including three new fossil sites with remains of ornithopod, sauropod and theropod dinosaurs. Sedimentation of SS-2 encompasses distal alluvial terrigenous facies with local palaeosoils and palustrine-lacustrine limestones grading upwards to middle-distal alluvial facies. After a late Barremian–early Albian stratigraphic gap, sedimentation resumed in coastal flat environments represented by the mudstones with intercalated skeletal (oyster-rich) sandy limestones with carbonaceous plant remains of the SS-3. A middle–late Albian age assignment of SS-3 based on regional correlation is supported by strontium isotopic data. This unit marks the first Early Cretaceous marine incursion in the area from the northern Atlantic realm. This is a notable change of the previous palaeogeographical reconstructions which established that the first marine encroachment occurred in the early Aptian and was sourced from Tethysian domains.

Petrogenesis and geodynamics of Eocene alkaline intrusions in the pre-salt sedimentary sequence of Santos Basin, Brazil

Lamprophyres and phonolite intrusions were sampled in the so-called Pre-Salt sequence of well 1-BRSA-905-RJS in northern Santos Basin nearby the Cabo Frio Structural High in SE Brazil. These alkaline rocks indicate the existence of a strongly silica-undersaturated trend. However, fractional crystallization modeling as well as Sr-Nd-Pb-Hf isotope data shows that the alkaline lamprophyres are not suitable parental compositions to the evolved felsic phonolitic magmas. The Sr-Nd-Pb-Hf isotope compositions of the lamprophyric magmas represent mixing of EM1 and Trindade plume mantle components. The EM1 is possibly related with the melt- and/or fluid-induced metasomatic processes on the subcontinental lithospheric mantle (SCLM) that occurred beneath the South American Platform during the Neo-Proterozoic-Cambrian subduction processes associated with the final stages of the Gondwana amalgamation, as recorded by the TDM ages (601-499 Ma) of the studied intrusions in Santos. 40Ar/39Ar analysis presented integrated age of 41.06±0.02Ma and 38.62±0.02Ma for phonolite and lamprophyre samples, respectively. A “plateau” age assignment for the true crystallization age of the sample could not be obtained due to the discordance in the ages of individual steps. This discordance was attributed to loss of radiogenic 40Ar that can happen in nature due to reheating events or metasomatism. An interaction between the Trindade plume head and SCLM is proposed for the geodynamics of Santos Basin at 40 Ma. The presence of an anomalously hot mantle represented by the deflected Trindade plume head beneath Santos at the Eocene is supported by the petrological and geochronological data. Therefore, it may be relevant to consider high geothemal flow regimes in basin evolution models proposed for Santos during the Eocene.

COMMENTS ON “STRATIGRAPHIC DISTRIBUTION OF SHALLOW-WATER BENTHIC FORAMINIFERA FROM THE LOWER CRETACEOUS TAFT FORMATION, CENTRAL IRAN (YAZD BLOCK), WITH EVIDENCE FOR THE IMPORTANCE OF HIATUSES” BY GHEIASVAND, M. ET AL. [ANNALES DE PALÉONTOLOGIE, 2020, 154 (3), 102399] AND RELATED PAPERS

Gheiasvand et al. (2020) use the two larger benthic foraminifera species Simplorbitolina manasi Ciry &amp; Rat and Mesorbitolina parva (Douglass) (Orbitolinidae) as upper Aptian “potential index fossils” for parts of the Taft Formation in Central Iran. This age assignment is accompanied by changes to well-established orbitolinid biozona-tions (e.g. occurrence of Praeorbitolina in the late Aptian) with far-reaching implications. These data were also used in a later “multidisciplinary study” (Gheiasvand et al., 2021) for isotopic correlations (e.g., location of OAE`s), delimitation of palaeobiogeographic faunal provinces and related migration patterns. It is shown herein that the taxa identified as S. manasi and M. parva belong to Iraqia simplex Henson and Palorbitolina lenticularis (Blumenbach) respectively documenting a lower and not an upper Aptian age. This revised age and the different taxononomic inventory do not question all results obtained by Gheiasvand et al. (2020, 2021), but provide a revised basis interpretation.

407-P: Long-Term Effect of Intensive Lifestyle Intervention on Incidence of Nephropathy in Adult Patients with Diabetes: A Post-hoc Analysis of a 10-Year Longitudinal Study

We previously reported that, in patients with diabetes, intensive lifestyle intervention (ILI) in real-world clinical practice could lead to significant weight loss that was attainable for up to 10 yrs and had favorable impact on glycemic control and lipid profile. These improvements were predicted by achieving ≥7% weight loss at 1 yr. In this secondary analysis, we investigated whether initial weight loss at 1 yr is associated with incidence of nephropathy over 10 yrs. This analysis included 128 patients with diabetes enrolled in a 12-wk ILI (age 53.7±10.1 yrs; 66.4% females; duration of diabetes 9.6±9.4 yrs; body mass index [BMI] 38.3±5.3 kg/m2; and 9.3% had type 1 diabetes). At 1 yr, we divided participants into 2 groups: group A (n=61, 47.7%) maintained &amp;lt;7% weight loss and group B (n=67, 52.3%) maintained ≥7% weight loss. Data on incidence of nephropathy were collected from electronic health records over 10 yrs of follow-up. Cox proportional hazard models were used to calculate hazard ratios after dichotomizing the incidence of nephropathy. After a median of 10 yrs of follow-up, the incidence rate of nephropathy in group A was 3.58 cases per 100 person-years vs. 1.42 cases per 100 person-years in group B (difference 2.16 cases per 100 person-years, sex-adjusted hazard ratio for group B: 0.33, 95% CI: 0.12, 0.94, p=0.039). Moreover, in a multivariable model fitted with terms for age, diabetes type, diabetes duration, BMI, plus group assignment and sex, the group-effect retained independent significance (fully adjusted hazard ratio for group B: 0.32, 95% CI: 0.11, 0.9, p= 0.007). We conclude that adult patients with diabetes who maintained ≥7% weight loss at 1yr after the initial ILI had a 68% lower risk of nephropathy for up to 10 yrs. These data support the essential role of weight reduction in preventing or delaying the progression of chronic kidney disease in patients with diabetes and overweight or obesity. Disclosure S. Tomah: Stock/Shareholder; Self; Amarin Corporation plc. H. Zhang: None. H. Gardner: None. M. Al-badri: None. O. Hamdy: Advisory Panel; Self; Nestlé, Consultant; Self; Abbott, AstraZeneca, Sanofi, Research Support; Self; Eli Lilly and Company, Gilead Sciences, Inc., National Dairy Council, Novo Nordisk, Stock/Shareholder; Self; Healthimation, LLC.

A Continuous Seismostratigraphic Framework for the Western Svalbard-Barents Sea Margin Over the Last 2.7 Ma: Implications for the Late Cenozoic Glacial History of the Svalbard-Barents Sea Ice Sheet

Here we present a high-resolution, continuous seismostratigraphic framework that for the first time, connects the over 1,000 km long western Svalbard-Barents Sea margin and covers the last ∼2.7 million years (Ma). By exploiting recent improvements in chronology, we establish a set of reliable age fix-points from available boreholes along the margin. We then use a large 2-D seismic database to extend this consistent chronology from the Yermak Plateau and offshore western Svalbard, southwards to the Bear Island Trough-Mouth Fan. Based on this new stratigraphic framework we divide the seismic stratigraphy along the continental margin into three seismic units, and 12 regionally correlated seismic reflections, each with an estimated age assignment. We demonstrate one potential application of this framework by reconstructing the Svalbard-Barents Sea Ice Sheet evolution from the intensification of the northern hemisphere glaciation at ∼2.7 Ma to the Weichselian glaciations. Through seismic facies distribution and sedimentation rate fluctuations along the margin we distinguish three phases of glacial development. The higher temporal resolution provided by this new framework, allows us to document a clear two-step onset to glacial intensification in the region during phase 1, between ∼2.7 and 1.5 Ma. The initial step, between ∼2.7 and 2.58 Ma shows glacial expansion across Svalbard. The first indication of shelf-edge glaciation is on the Sjubrebanken Trough-Mouth Fan, northwestern Barents Sea after ∼2.58 Ma; whilst the second step, between ∼1.95 and 1.78 Ma shows glacial advances beyond Svalbard to the northwestern Barents Sea. Phase 2 is characterized by variations in sedimentation rates and the seismic facies are indicative for a regional glacial intensification for the whole Barents Sea-Svalbard region with widespread shelf-edge glaciations recorded at around ∼1.5 Ma. During Phase 3, the western Barents Sea margin is characterized by a dramatic increase in sedimentation rates, inferring once again a regional glacial intensification. Our new stratigraphic framework allows for the first time differentiation of the sediments deposited on the slope during Early Saalian (∼0.4 and 0.2 Ma), Late Saalian (∼0.2 and 0.13 Ma), and Weichselian (&amp;lt;∼0.123 Ma) periods, providing new insights into the Barents Sea glaciations over the last ∼0.42 Ma.

Unravelling metamorphic ages of suture zone rocks from the Sabzevar and Makran areas (Iran): Robust age constraints for the larger Arabia–Eurasian collision zone

AbstractIn this study we establish a time frame for metamorphic processes affecting Neotethyan suture zones at the northern (Sabzevar) and southern (Makran) margin of the Central Iranian Microcontinent. For this purpose, we have applied Rb–Sr and U–Pb geochronology to blueschist‐ and amphibolite facies rocks from these occurrences. So far, no isotopic ages are available for high‐P/low‐T rocks from the Sabzevar area which are exposed in the Govain and Chili mountains near Soltanabad. Three newly dated blueschists from the Govain mountain yielded Rb–Sr ages of 56.52 ± 0.32, 57.20 ± 0.32, and 55.12 ± 0.33 Ma respectively. These ages provide the first unambiguous evidence for late Palaeocene to early Eocene high‐P metamorphism in the Sabzevar zone and confirm the accuracy of earlier age assignments that were derived indirectly. The clearly confirmed age difference between late Palaeocene–early Eocene blueschists of the Govain mountain and kilometre‐scale dismembered HP granulites with Early Cretaceous (Albian) metamorphic ages from outcrops c. 60 km to the west of Soltanabad further corroborates interpretations that these rocks are not related to the same subduction zone complex. The blueschists record closure of an Albian to Late Cretaceous back‐arc basin, whereas the granulites formed due to subduction of older oceanic lithosphere. Uranium–Pb zircon dating of an amphibolite from the Iranshahr region in the Makran Zone yielded an intercept age of 87.8 ± 1.8 Ma and weighted mean age of 88.1 ± 1.7 Ma. Rb–Sr mineral isochrons for seven blueschist‐ and amphibolite facies samples from the same area generated very consistent ages of c. 84 Ma (± &lt;1–3 Ma), regardless of metamorphic grade. The apparent contradiction that rocks recording different P–T conditions have identical metamorphic ages either indicates tectonic mixing of rocks during exhumation that originally had formed at the same time at different depths of the subduction system, or very rapid exhumation so that differences in closure temperatures became indistinguishable. The new data are similar, but much more precise, than previously reported K–Ar ages and suggest that most of the existing data had not been significantly compromised by contamination with extraneous Ar. Potassium–Ar indications for older blueschist‐ and/or amphibolite facies metamorphism (&gt;85 Ma) have not yet been confirmed but can be reconciled with the larger geological frame implying that northward subduction of the Arabian plate beneath the Bajgan–Durkan continental block started shortly after c. 120 Ma.

The Upper Cretaceous Mamonia Mélange (Petra tou Romiou, southwestern Cyprus): composition and age

Spectacular exposures of the Mamonia Mélange are studied in the Petra tou Romiou area, in southwestern Cyprus, with aim to distinguish the nature and age assignment of this chaotic complex. It is a typical tectonic mélange made up of clayey/silty matrix and blocks, which are mainly derived from the sedimentary and volcano-sedimentary rocks of the Ayios Photios and Dhiarizos groups respectively, as well as subordinate blocks derived from the Troodos Ophiolite Complex. The youngest blocks within the Mamonia Mélange are comprised by cherts that exhibit a well-preserved lower Turonian radiolarian assemblage. In the studied area, the tectonic mélange is overlain with clear unconformity by the upper Campanian–lower Maastrichtian bentonitic clays of the Kannaviou Formation. This indicate that the Mamonia Mélange was formed between the Turonian to Campanian period, as a result of the collision and juxtaposition of the Mamonia Complex with the Troodos Ophiolite Complex.

Earliest Arikareean (later early Oligocene) Iniyoo local Fauna from Chilapa Formation of Santiago Yolomécatl area in northwestern Oaxaca, southern Mexico

Strata containing the Iniyoo Local Fauna (LF) crop out in the outskirts of Santiago Yolomécatl in the Yolomécatl Subbasin of the southeastern Tlaxiaco Basin in northwestern Oaxaca, southern Mexico. The assemblage is from a 325-m-thick fluviolacustrine unit previously assigned to the Yanhuitlán Formation and then the Yolomécatl Formation, which was restricted to the Yolomécatl Subbasin and its immediate vicinity. However, recent field investigations and laboratory analyses indicate the unit is, instead, a marginal facies of the dominantly lacustrine Chilapa Formation, which unconformably overlies the Yanhuitlán Formation where intervening volcanic units are absent. Consequently, Yolomécatl Formation is abandoned in favor of Chilapa Formation on the bases of synonymy and priority. Similarly, San Marcos Andesite and Nicananduta “Group” were applied to the same exposures of an andesitic unit interfingering with the Chilapa Formation. Accordingly, Nicananduta “Group” is abandoned and replaced by San Marcos Andesite for the same reasons.The Iniyoo LF is earliest Arikareean (Ar1) (i.e., later early Oligocene) in age, not latest Uintan to late Chadronian (i.e., later early middle to latest Eocene), based on the first appearance datum for the amphicyonid Mammacyon and the last appearance datums of the tayassuid Perchoerus probus and the rhinocerotid Subhyracodon. That age assignment is supported by (1) corrected potassium-argon (K–Ar) dates of 28.939 ± 0.6 and 30.376 ± 0.6 Ma for the Yucudaac Andesite's lowermost flow or lower tongue, which underlies the Chilapa Formation north of the Yolomécatl Subbasin, (2) a corrected 40argon/39argon (Ar/Ar) date of 27.829 ± 0.716 Ma for the correlative Nicananduta “Group” (= San Marcos Andesite), which overlies the Chilapa Formation in the Yolomécatl Subbasin, and (3) uranium-lead (U–Pb) maximum depositional ages of 30.6 ± 0.77 and 30.62 ± 0.67 Ma for detrital zircon grains from sandstone beds occurring above the bottom and top, respectively, of the nearly 88.4-m-thick vertebrate fossil-bearing interval. The K–Ar and Ar/Ar dates further constrain the age of the Iniyoo LF to an interval spanning about 27.83–28.94 Ma ago.A corrected Ar/Ar date of 40.561 ± 1.009 Ma for potassium-feldspar crystals in a bed originally identified as a silicified tuff sheet and later determined during the current investigation to be a sandstone bed was bracketed by the two sandstone beds subjected to U–Pb dating analyses. However, the last Ar/Ar age is much too old when compared with the two U–Pb dates for the Chilapa Formation and the three K–Ar and Ar/Ar for volcanic units bracketing the formation. Presumably, the dated material represented volcanic debris reworked from a substantially older unit. Consequently, the Ar/Ar date and any land mammal age assignment based on it are considered highly unreliable.

Calcareous nannofossil biostratigraphy of Miocene-Pliocene sequence in the Monaga-1 Well, Nile Delta, Egypt

The Miocene-Pliocene sequence at the Monaga-1 Well, eastern of the Nile Delta, has been examined using sixty-six ditch cutting subsurface samples, to subdivide this interval litho- and biostratigraphically based on calcareous nannofossils. Four lithostratigraphic formations and their age assignment have been recognized, organized from the highest to the lowest as follows: Kafr El-Sheikh, Abu Madi, Sidi Salem, and Qantara formations. Eight calcareous nannofossil biozones have been documented, arranged from the top to the base as follows: NN15, NN14, NN13, NN11, NN9, NN5, NN4, and NN3. The recognized biozones were compared with their respective biozones in and outside Egypt, and used to shed some light on the boundaries of the Neogene stage. Three hiatuses have been noted in the Abu Madi Formation owing to structure control as that of the depositional conditions of this formation which were tectonically unstable. Pliocene lies unconformably above the Miocene, and a small hiatus was determined where NN12 zone is missing. The Tortonian/Messinian boundary cannot be exactly determined because there is a small hiatus that is suggested by the absence of the upper NN9 zone in addition to the whole of NN10 biozones. Late Miocene overlies unconformably the Middle Miocene. This unconformity was detected by the misplaced NN6, NN7, and NN8 zones and probably the basal part of NN9 zone. At the lower boundary of the zone (NN5), the Burdigalian/Langhian boundary was drawn.