Sedimentary Succession Research Articles

The Psematismenos-Maroni Basin (South Cyprus): Cenozoic tectonic and sedimentary evolution

The Tertiary regressive sedimentary succession, which forms the sedimentary cover of the Troodos Ophiolitic Massif, was studied in the Psematismenos-Maroni Basin in Southern Cyprus. A series of unconformity surfaces were identified based on key surfaces, morphologies, and sedimentary facies. These observations are reinforced by numerous new biostratigraphic datings mainly based on calcareous nannofossil analysis. Unsuspected biostratigraphic hiatuses ranging from million to dozens of millions of years are illustrated. Some unconformity surfaces are tectonically enhanced leading to the emersion of this basin. In addition, our work highlights the importance of the Messinian Salinity Crisis in the shaping of an onshore erosion surface in Cyprus as it is the case in the Sorbas basin in the western Mediterranean. Constrained by new datings, this work finally proposes a tectono-stratigraphic calendar for the Psematismenos-Maroni Basin, starting from the Paleogene Lefkara Formation up to the first alluvial deposits at the end of the Neogene.

Sediment flux variation as a record of climate change in the Late Quaternary deep‐water active Corinth Rift, Greece

AbstractThe value of deep‐water sedimentary successions as reliable records of environmental change has been questioned due to their long response times and sediment pathways leading to complex responses to climatic change and tectonic signals over differing timescales. We studied the Gulf of Corinth, Greece, to test the value of deep‐water stratigraphic successions as records of external controls on sediment flux in a setting with short response times and transport distances. The confinement of the rift basin allows for a near‐complete accounting of clastic sediment volumes. The recent acquisition of high‐resolution seismic reflection data, utilisation of International Ocean Discovery Programme Expedition 381 cores and a robust chronological framework, enable evaluation of the stratigraphy at a high temporal resolution. Combining borehole and high‐resolution seismic reflection data, distinct seismic units can be correlated to multiple paleoenvironmental proxies, permitting quantification of sediment flux variation across successive glacial–interglacial cycles at ca. 10 kyr temporal resolution. Trends in average sediment flux since ca. 242 ka show ca. 2–9 times greater sediment flux in cooler glacials compared to warmer interglacial conditions. The Holocene is an exception to low sediment flux for the interglacials, with ca. 5 times higher rates than previous interglacials. The short and steep configuration of the Sythas canyon and its fan at the base of an active submarine normal fault results in deep‐sea deposition at all sea‐level stands. In contrast, adjacent canyon systems shut down during warm intervals. When combined with palynology, results show that periods of distinct vegetation re‐organisation correlate to sediment flux changes. The temporal correlation of sediment flux to palynology in the Gulf of Corinth over the last ca. 242 kyr is evidence that variability of sediment supply is largely governed by climate‐related changes in hinterland catchments, with sea‐level and tectonics being second‐order controls on sediment flux variability.

Cambrian (Fortunian to Jiangshanian) depositional environments of northwestern Mexico: Distribution and facies patterns along the western margin of Laurentia

The Cambrian sedimentary successions from Sonora, Mexico provides information about the sedimentary and geological evolution that occurred on the western margin of Laurentia. The sedimentary rocks from the Fortunian to Jiangshanian stages denote eustatic changes. Initially (Fortunian to Stage 3), shallow water marine clastic-carbonate deposits are found in northwest Sonora. These deposits comprise tidal flats and lagoons with storm deposits and reefs dominated by archaeocyaths. The Stage 4 to Wuliuan sedimentary succession represents the most documented Cambrian transition in Mexico, which includes deposits from the shoreline - beach conditions, lagoon and restricted inner platform with low diversity of polymerid trilobites, to an outer platform - deep shelf margin with abundant agnostids. On the other hand, the sedimentary environments during the Drumian to Guzhangian changed from an outer shelf marine environment to a shallow water marine platform. And finally, rocks from the Paibian to Jiangshanian denote an outer shelf transition to a middle to outer shelf margin.

First multi-proxy chronostratigraphy of the lower Cambrian Byrd Group, Transantarctic Mountains and correlation within East Gondwana

Antarctica and Australia were sutured together at the equator during the major pulse of animal biodiversification associated with the Cambrian radiation. However, the lack of detailed systematic chemostratigraphic and biostratigraphic sampling of lower Cambrian sedimentary successions from Antarctica has significantly impeded precise age determination and correlation with Cambrian strata on other palaeocontinents. This study is the first to present integrated, simultaneously sampled biostratigraphic and chemostratigraphic (δ13C isotopes) data from the same measured stratigraphic sections through the lower Cambrian Byrd Group in the Transantarctic Mountains. Shelly fossil assemblages (brachiopods, tommotiids, molluscs, bradoriids, trilobites) from the Holyoake Range and Churchill Mountains facilitate direct correlation with the Dailyatia odyssei Zone of South Australia (Cambrian Stages 3–4), and trilobites provide strong correlation between the Starshot Formation and the Cymbric Vale Formation in western New South Wales. A new ID-TIMS radiometric date of 514.96 ± 0.16 Ma from a tuff in the lower Cymbric Vale Formation is similar to dates from tuff beds in the Third Plain Creek Member of the Mernmerna Formation in the Flinders Ranges, providing an important absolute-age tie point between these lower Cambrian successions. Chemostratigraphic data from the upper Shackleton Limestone in the Holyoake Range capture a negative δ13C excursion that can be correlated to negative values within the multi-peaked MICE (cycles V–VIII in Siberia). Integrated faunal and chemostratigraphic data indicate a Cambrian Stages 3–4 age, giving robust chronostratigraphic context for the upper Shackleton Limestone–Holyoake Formation–Starshot Formation succession for the first time, permitting reconstruction of the depositional history of the lower Cambrian of Antarctica and global correlation of Byrd Group strata.

The Campanian-Maastrichtian benthic foraminiferal assemblages at the Elles section (Tunisia): A perspective for paleoenvironmental, paleobathymetric and sea-level fluctuation reconstruction

The Late Cretaceous Period experienced prevailing hothouse conditions that were characterized by relatively elevated atmospheric pCO2 concentrations, high global mean sea level and mostly lacking ice sheets. These conditions were interrupted by an overall global decreasing trend in temperature during the Campanian-Maastrichtian interval (83.65 to 66.04 Ma). The Upper Cretaceous sedimentary successions in Tunisia (southwestern Tethyan Ocean) like at the Elles section are regarded as unique archives for investigating paleoenvironmental and paleoclimatic changes, as well as constrain oscillations of sea-level. Here, we perform high resolution quantitative analysis of the benthic foraminiferal assemblages in the Campanian-Maastrichtian interval at the Elles section in order to infer palaeoenvironmental and paleobathymetric changes in relative sea-level. The Campanian succession (Abiod Fm.) is inferred to be deposited at upper to middle bathyal (i.e., 540–675 m) and is characterized by prevailing well‑oxygenated conditions and low organic matter flux to the seafloor. The Campanian/Maastrichtian transition-coincides with the lowermost part of the El Haria Fm. deposited in outer neritic to upper bathyal settings under oligotrophic, well‑oxygenated and reduced productivity conditions. Shallower depositional setting (i.e., 436–515 m) is inferred for the Maastrichtian succession (El Haria Fm.) that is also characterized by a lowering in oxygen availability at the seafloor associated with an increase of organic matter. Eight main sea-level regressions (four in the Campanian, one at the Campanian-Maastrichtian transition and three in the Maastrichtian) have been identified and biostratigraphically constrained. These sea-level regression events are mostly accompanied by a negative excursion carbon isotope (δ13C) and their stratigraphical positions appear to be quite consistent with those previously recognized at the nearby El Kef section.

Long-term stability of sediment routing on an active continental margin: Insights from detrital zircon U-Pb ages and measured stratigraphy of Carboniferous to Miocene strata, Sierra de Narváez, NW Argentina

The complex Phanerozoic tectonic evolution of the western margin of South America, including extensional, neutral, and contractional deformation regimes, provides an opportunity to test how sedimentary systems were affected by variable tectonics on a long-lived active margin. Here, we report new geologic mapping, measured stratigraphic sections, paleocurrent measurements, and detrital zircon U-Pb ages from the Fiambalá area, NW Argentina, that together constrain the evolution of sediment routing and basin systems of the northern Sierras Pampeanas during Carboniferous to Miocene time. Carboniferous to Triassic strata of the Paganzo Group include fluvial, lacustrine, and eolian intervals deposited in an extensional setting with SSW-directed paleocurrent orientations. The Mesozoic El Pedernal Formation consists of a lower, basalt interval and an upper, conglomerate and sandstone interval, which has a new detrital zircon maximum depositional age of ca. 88 Ma. Observed strata of the Miocene Tambería Formation include fluvial to eolian sandstones of the lower member of the formation and alluvial conglomerates of the middle member. Whereas lower member Tambería fluvial strata have SSW-oriented paleocurrents, middle member conglomerates indicate broadly E-directed paleoflow.Detrital zircon age distributions of the Paganzo Group, El Pedernal Formation, and Tambería Formation are remarkably consistent, with dominant age peaks ca. 1.3–0.9 Ga and ca. 660-450 Ma. The ages and relative magnitudes of these peaks are consistent with derivation from igneous sources associated with Choiyoi magmatism (330-215 Ma), the Famatinian (490-450 Ma) and Pampean (540-510 Ma) orogens, basement of the MARA block (ca. 1.3–0.9 Ga), and recycling of Neoproterozoic to Cambrian sedimentary successions derived from central Gondwana (ca. 1.3–0.9 Ga, 650-590 Ma, 540-510 Ma).The consistent paleocurrent orientations and detrital zircon U-Pb ages of the Carboniferous Paganzo Group to the Miocene lower member of the Tambería Formation suggest that a S-directed axial drainage network with a consistent sediment source area persisted in the region for ∼300 Myr. This axial drainage network was succeeded by an E-directed transverse drainage network initiated between 15 Ma and 8 Ma due to growth of the Andean thrust wedge, coeval with tectonic compartmentalization and drainage modification of nearby foreland depocenters. These findings highlight the potential for long-term persistence of drainage networks on continental margins under changing tectonic regimes.

Quaternary environment and climate change reconstruction from geochemical and geoarchaeological evidences of paleosols in east-central Barind, NW Bangladesh

This research focuses on analyzing paleosols, major and trace element geochemistry, organic carbon levels, and geo-archaeological aspects of Quaternary deposits investigated in two sedimentary successions located in the east-central Barind region of NW Bangladesh. Several factors that influence the paleosol development can be used to decipher the paleoenvironment and paleoclimatic conditions of the study area. Sedimentary succession of the studied sections have been grouped into two broad categories i.e., Gray unit/Newer Alluvium (NA) of Late Holocene and Red unit/Older Alluvium (OA) of Early Pleistocene age. Some geoarchaeological evidences have been found at the bottom of the gray unit and the top of the red unit in Durgadaha (DD) section indicating the existence of paleo-settlement at about ∼1300 years BP. The age is determined by the relative dating of several artifacts found at the paleo-settlement surface. Interpretation of several field characteristics and geochemical parameters i.e., clayeyness, salinization, base loss, calcification, leaching (Ba/Sr), aeolian input (Zr/Al), CIA, CIW, CIA-K, etc. revealed that the paleosols in gray unit are weakly developed; whereas, paleosols in red unit are relatively moderate, strong to very strongly developed. In the red unit, the MAP and MAT range from 1000 ± 181 mm to 1478 ± 181 mm and 9° ± 4.4°–14° ± 4.4 °C respectively. On the other hand, MAT ranges from 23.1° ± 0.6 °C to 28.3° ± 0.6 °C in gray unit paleosols. Depending on the depositional pattern and estimated MAT, five short-term climatic cycles (i.e., alternating phases of dry and wet) have been recognized in gray/newer alluvium units during the last 1300 years. The demise of paleo settlement (1300 years BP) due to the abrupt climatic change towards a dry and cooler phase where the MAT was estimated as 23.1° ± 0.6° which is at least 3 °C lower than the present. This study also revealed that the estimated MAP and MAT are more analogous to paleoclimatic records of the Asian regions.

Orbital forcing and paleoenvironmental changes across the upper Ordovician glaciation-lower Silurian hot shale in the Risha gas field, northeast Jordan

This paper presents a comprehensive analysis of sedimentary successions and paleoenvironmental indicators in two wells, Rh3 and Rh46, located in NE Jordan, within the context of the Ordovician-Silurian boundary transition. By integrating spectral analysis, cyclostratigraphy and sedimentary architecture, significant shifts and cyclical patterns are identified, shedding light on paleoenvironmental changes and orbital forcing dynamics. The study reveals distinct lithological and geochemical signatures at the Risha/Mudawwara (Hirnantian/Rhuddanian) boundary, indicative of major shifts in depositional environments. Analysis of Milankovitch cycles suggests orbital forcing as a driver of sedimentary cyclicity, with implications for understanding climatic variations during the Ordovician-Silurian transition. Spectral analysis revealed significant cycles with different periodicities. Testing the sediment accumulation rates (SAR) revealed an optimum SAR at 5.9 and 4.6 cm/kyr in Rh3 and Rh46 wells, respectively. A new refined astronomical time scale (ATS) is created based on the 100 kyr eccentricity cycle. The new ATS assigns the Risha Formation to the Hirnantian age and revealed a probable time gap at the base of Risha Formation of about 0.3 myr in Rh46 well; deposition of the Risha Formation commenced at 444.88 myr and 444.58 myr in Rh3 and Rh46 wells, respectively, with sedimentation continuing up to the Ordovician/Silurian boundary at 443.07 myr. The Ordovician/Silurian transition experienced shortening in the obliquity and precession cycles. The tuned data show that the 41, 36 and 31 kyr obliquity cycles, in addition the 21, 19 and 16 kyr precession cycles, were recognised. Furthermore, 740, 425, 250, 147 and 100 kyr eccentricity cycles were also recognised. Notably, the study identifies the glacial/fluvioglacial Risha Formation is bounded by g4-g3 eccentricity nodes coinciding with Hirnantian stage boundaries that correspond to significant geological events, such as the Late Ordovician Mass Extinction and the Hirnantian glaciation events. The g4-g3 eccentricity cycle is estimated to be 1.8 myr. Surprisingly, the lower Silurian OAE coincided with the g4-g3 eccentricity node at the Ordovician/Silurian transition. Additionally, the application of DYNOT modelling has elucidated sea-level fluctuations and their relationship with sedimentary sequences, highlighting the role of tectonic and climatic factors in shaping the sedimentary architecture. Furthermore, the investigation of Th/U and Th/K ratios provides insights into marine and terrestrial depositional settings.

Multiple short-lived marine incursions into the interior of Southwest Gondwana during the Aptian

The Lower Cretaceous sediments of the Sanfranciscana Basin, southeast Brazil, are considered to have been deposited under a Gondwanan continental context. However, different authors have occasionally observed marine elements in these same deposits. This study analyzes samples from five sections of the Sanfranciscana Basin, Quiricó and Três Barras formations, to characterize the paleoenvironment around these marine incursions. We recovered continental (non-marine ostracods and palynomorphs) and marine microfossils (e.g., foraminifera, radiolarians, and ascidian spicules). The alternance of quartz-rich biogenic chert and claystone might be indicative of the occurrence of radiolarites in the studied sessions. The presence of the radiolarian genus Turbocapsula sp., the radiolarian species Holocryptocapsa fallax, and the palynomorph Tucanopollis crisopolensis enabled us to date the interval as early Aptian. Based on the lithologies and microfossils recovered, we interpreted the studied interval as a continental setting that was episodically subjected to marine incursions. We propose three successive paleoenvironmental scenarios: (1) an initial lacustrine depositional setting with a non-marine biota; (2) a second stage, characterized by the presence of episodic marine influence in the sedimentary succession (as evidenced by radiolarians, foraminifera and ascidians), and (3) the return to continental settings dominated by aeolian dune fields. These environmental scenarios characterize the initial development of the Central Segment of the South Atlantic Ocean.

Palynology of the Jurassic–Cretaceous transition, Surat Basin, Australia

This paper presents, for the Queensland portion of the Rhaetian – Early Cretaceous Surat Basin, the results of a taxonomic-descriptive study of 89 palynological samples collected from three boreholes that intersected the succession containing the Gubberamunda Sandstone and the succeeding Orallo Formation, as well as the upper Westbourne Formation and the lower Mooga Sandstone, which respectively underlie and overlie this succession. This upper Westbourne Formation – lower Mooga Sandstone interval represents the most complete Late Jurassic – Early Cretaceous sedimentary succession in Queensland. It was sampled from: GSQ DRD 26, GSQ Roma 2 and GSQ Dalby 1, respectively located in the western, central, and eastern parts of the basin. The samples yielded a diverse palynoflora in which 212 taxa were identified, embracing both in-situ and reworked (latest Carboniferous – Early Jurassic) spores and pollen, as well as palynomorphs of algal, fungal, acritarch and unknown affinities. Formally included in this work is the previously unpublished taxonomy of McKellar, largely from the immediately preceding part of the Surat Basin succession, as its taxonomic nomenclature is critical to the current compilation. Herewith proposed (from both the current work and that of McKellar) are 27 new species, two new genera, 22 new combinations, ten emendations, the elevation of one subgenus to generic status, and the renaming of one species. From a biostratigraphic perspective, palynofloras from the upper Westbourne Formation and the lower Gubberamunda Sandstone are assigned to the informally defined ‘Retitriletes watherooensis association zone’, and palynofloras from the upper Gubberamunda Sandstone, Orallo Formation and lower Mooga Sandstone, to the Ruffordiaspora australiensis Interval Zone. The upper Westbourne Formation – lower Mooga Sandstone interval was deposited in lacustrine, floodplain and backswamp facies, with a flora that remained relatively stable, there being no major floristic turnover; it consisted of diverse ferns, conifers, lycopods, bryophytes, seed ferns, and a variety of ginkgoes, cycads, and/or gnetales. Humid, warm-temperate conditions are indicated by the flora’s climatic signature.

Controls on the genesis of a giant sand injection complex; insights into the Paleogene evolution of the stress of northern and central California

Giant sand injection complexes and localized swarms of sandstone intrusions are common in Upper Cretaceous to Miocene sedimentary successions of central and northern California within a distance of less than 100 km from the Pacific margin of the North America plate. One of the best preserved and extensively exposed injection complexes is the late Eocene Tumey Giant Injection Complex. The emplacement of sand injectites was driven by overpressure generated by thermal diagenesis of biosiliceous and smectite-rich mudstone host-rocks. The orientation and size distribution of sandstone intrusions was controlled by stress in which σ 1 and σ 3 were horizontal and, respectively, parallel and perpendicular to the present trace of the San Andreas Fault, and σ 2 was vertical. A strike-slip tectonic regime is inferred. Our analysis documents margin-orthogonal extension and provides support for a late Eocene phase of increase of strain, and possibly active slip, along a syn-subduction strike-slip fault zone. Comparison with other injection complexes in the region indicates that the near-field maximum principal stress rotated through time, from normal to parallel with respect to the plate margin, probably in relation to variations of the relative motion vector of the converging plates.

Investigating the hydrocarbon potential of the Paleogene coal seams in Kapuni field, Taranaki basin, New Zealand: Implications for coal-oil correlation

Hydrocarbon generation in Taranaki Basin, New Zealand, has been proven in several source rocks within the syn- and post-rift basin-fill sedimentary successions. These source rocks are mainly hosted in the marginal and deep marine Upper Cretaceous shales, which generate marine and terrigenous oils. Some of the terrigenous oils could have been linked to the Paleogene coals; however, the capability of these coals to generate and expel liquid hydrocarbons is poorly-investigated. In this study, we present organic geochemistry, kerogen petrography, wireline logging, and basin modelling to evaluate the hydrocarbon generation potential of the Paleogene coals and coal-rich facies of the Kapuni Group sediments in Kapuni Field, Taranaki Basin. A compositional correlation between oil in the Kapuni Group reservoirs and coal extracts was performed to decipher the oil origin and define its parent source rock. Kapuni oils display high pristane/phytane (Pr/Ph) > 5, low dibenzothiophene (DBT)/phenanthrene <0.1 and high relative abundance of C29 regular steranes >60%, typifying their generation from a terrigenous source rock deposited in an oxic, fluvio-deltaic environment. Similar values were also observed in the muddy coal extracts of Farewell Formation, thereby reflecting a positive coal-oil correlation. The maturity-relevant biomarkers (Ts/Tm trisnorhopanes; C29 steranes isomers, and 22S-, 22R C32 homohopanes) are similar in both oils and Farewell coal extracts confirming oil expulsion from Farewell coals during the peak oil window maturity. These results demonstrate the generation and expulsion of coal-oil, thereby shedding light on the prospectively of the Paleogene plays in the Taranaki Basin.

Petrophysical Parameters and Electrofacies Models of the Itararé Group Applying Multi-Resolution Graph-Based Clustering Method, Paraná Basin

Volume shale (Vsh) and effective porosity (Φe) were calculated and partially applied as petrophysical input parameters to generate electrofacies models using the Multi-Resolution Graph-Based Clustering method in sedimentary successions of the Itararé Group. The petrophysical parameters and electrofacies models were determined from geophysical data from two wells located in the eastern portion of the Paraná Basin. The stratigraphic intervals in each well (analogues of hydrocarbon reservoirs) allowed petrophysical analysis and the determination of electrofacies models based on gamma ray profiles, apparent density and neutron porosity, together with lithological data. The petrophysical parameters were calculated by different procedures, and the effective porosity results were applied as input parameters for electrofacies modeling. The electrofacies models were correlated to lithological data and patterns of gamma ray profiles and apparent density, as well as different types of porosity. The generated models provide differences related to the type of porosity, the method applied to calculate the effective porosity and present probable relationships with the lithological units of the wells.

Nuskoisporites dulhuntyi from the Cisuralian and Lopingian of the Southern Alps: A morphological comparison between dispersed and in situ prepollen

Nuskoisporites dulhuntyi is considered one of the biostratigraphic marker species for the Lopingian of Europe. A morphological comparison between Kungurian (Cisuralian) and Wuchiapingian (Lopingian) Nuskoisporites dulhuntyi prepollen (dispersed from five outcrops and in situ from one cone) from the Southern Alps has been carried out. Dispersed Nuskoisporites dulhuntyi prepollen grains from the Kungurian (Cisuralian) of the Athesian Volcanic District (AVD) and the Wuchiapingian (Lopingian) of Bletterbach have been compared with the in situ prepollen grains isolated from an Ortiseia cone of the Bletterbach outcrop. Using light microscopy, we measured overall size, central body size, and laesurae length of the prepollen grains revealing significant overlaps in morphological characteristics between the different assemblages. The main difference is the bigger size of the in situ pollen grains in comparison with the dispersed ones, but a significant overlap is still observed. This implies that the prepollen grains from the Kungurian sedimentary successions of the Athesian Volcanic District can be assigned confidentially to the dispersed prepollen species Nuskoisporites dulhuntyi and hence, represent the so far oldest record of this taxon, extending the species range from the Guadalupian back to the late Cisuralian.

Vertebrates from the Late Miocene of Salinas Grandes de Hidalgo (central Argentina). New faunal data: biochronological and paleoenvironmental considerations

ABSTRACT Salinas Grandes de Hidalgo (La Pampa Province) is a relevant locality of the Cerro Azul Formation in central Argentina because of its abundant and diverse vertebrate remains, including representatives of Reptilia, Aves and mostly Mammalia. Concerning previous records, the present faunal list adds one Argyrolagidae marsupial, one Ctenomyidae and two Caviidae rodents, as well as the first detailed analysis and description of glyptodonts from the Cerro Azul Formation in La Pampa Province. New geological information is added about the two fossiliferous outcrops included in Salinas Grandes de Hidalgo area. The classically studied outcrop located in the saline lake and the nearby one in the so-called ex-Autódromo, both herein correlated based on lithostratigraphy, particularly by the presence of paleosols in the intermediate section of the sedimentary succession. These sandy silts deposits in the base of the outcrops indicate the development of poorly confined flows and intervals of surface stabilisation by paedogenesis. We offer a biochronological interpretation based on a recently published U-Pb detrital zircons dating (5.9 ± 0.4 Ma) and the presence of significant taxa such as octodontoid rodents recovered from the dated levels and below it. From a paleoenvironmental viewpoint, we infer variations from woodlands to open environments.

Eurasian Arctic Rifted Margin Composite Tectono-Sedimentary Element

The Eurasian Arctic Rifted Margin (EARM) spans a poorly studied transition region between the Eurasian continental shelf and the deep-water Nansen Basin. It is a conjugate margin to the Lomonosov Ridge, as both domains were united before the opening of the oceanic Eurasia Basin. The EARM is considered as a Composite Tectono-Sedimentary Element (CTSE) consisting of two individual tectono-sedimentary elements (TSEs): (1) an undefined group of poorly known pre-rift Mesozoic and Paleozoic sedimentary successions; and (2) Late Cretaceous–Paleocene synrift strata. The latter are bounded by a c. 56 Ma break-up unconformity and are overlain by the Eurasia Basin prograded margin TSE, which is not included in EARM. In the absence of drilled wells, we utilize multichannel seismic reflection (MCS) data for seismic stratigraphic correlations with nearby, better-explored, areas. The EARM CTSE is subdivided into three along-strike segments (from west to east): Svalbard–Barents Sea, the North Kara Sea and the Taimyr–Laptev Sea. Across-strike, the EARM CTSE is composed of a proximal zone of stretched crust characterized by normal faulting and a relatively narrow distal transition zone that may contain unroofed serpentinized mantle. The lack of drilled wells makes it challenging to evaluate the petroleum potential of the CTSE, although some indications of a working petroleum system presence exist.

The “underfilled trinity model” of foreland basins revisited: reality or myth?

The “underfilled trinity” model of foreland-basin stratigraphy was proposed based on the observation that the initial sedimentary stages along the western and northern front of the western and central Alps were represented by shallow-water carbonates (Calcaires à Nummulites) overlain by hemipelagic marls (Marnes Bleues) and capped by siliciclastic turbidites (Grès d’Annot). Subsequently, this model has been widely accepted and applied in foreland basins worldwide. We here re-investigated the Eocene-Oligocene sedimentary succession of the Western Alps to check its validity. Major geological features of this region include: i) the existence of a Cretaceous-Eocene unconformity spanning more than 25 Myr in the studied sections; ii) a virtually synchronous age of the Calcaires à Nummulites, Marnes Bleues, and Grès d’Annot formations across the Western Alps; iii) a long-term deepening-upward trend, from inner to outer ramp, documented by the Calcaires à Nummulites, followed by the pelagic Marnes Bleues and by the Grès d’Annot turbidites; iv) the provenance of the Grès d’Annot Formation from the Maures-Estérel Massif and/or Corsica-Sardinia block in the south, rather than from the Alpine orogen in the east. By integrating field observations, sedimentological, biostratigraphic, and provenance analyses, we found the Eocene “underfilled foreland” model too simplistic and inadequate to explain the basin evolution in the western Alpine region. Based on the alternative scenario proposed herein, the Annot and Barrême basins formed in the late Eocene (40-35 Ma) in an extensional/transtensional setting during a period of major change in tectonic stress fields across western Europe on the upper plate of the Apennine subduction.

Weathering, redox proxies and carbon isotope data from the Maokou Formation, Upper Yangtze, South China: Implications for the Guadalupian P3 glaciation of the Late Paleozoic Ice Age

Late Paleozoic Ice Age (LPIA) was a key climate event of the deep-time earth evolution system. Although the sedimentary successions from eastern Australia have well constrained the timeframe of the glacial-nonglacial intervals, the link between these glaciations and coeval geological events is still being explored. The Guadalupian (Middle Permian) P3 glaciation was the prelude to the upcoming end of LPIA, which is a key window to examine the uncertainty of the climatic transition from icehouse to greenhouse and linkages with the geological and biological events. This study focuses on the marine sedimentary succession of the Shangsi outcrop located in the low-latitude Yangtze block, investigating the carbon/strontium isotopes, redox proxy, and chemical index of alteration (CIA). Multiple weathering indices revealed climatic fluctuations during the Guadalupian, corresponding to the onset and demise of the high-latitude P3 glaciation. The high level of CIA following the Kungurian-age Large Igneous Provinces (LIPs) event indicates that the weathering of basic rocks caused the positive 13C drift, which was the main factor for the onset of the P3 glaciation. Then the breakup of Pangea, enhanced ocean oxidation, and a series of volcanic activities including Emeishan LIP could contribute to the accumulation of CO2 and consequently cause the demise of the P3 glaciation in middle Capitanian. Enhanced continental weathering was synchronous with the eruption surge of the volcanic activities, indicating a following global warming event, which may play a crucial role in triggering the Mid-Capitanian extinction event.

Tectono‐sedimentary history of the upper Cedar Mountain Formation, Central Utah, USA

ABSTRACTCurrent investigations into the Albian–Cenomanian sedimentary record within the Western Interior have identified multiple complex tectono‐sedimentary process–response systems during the ongoing evolution of North America. One key sedimentary succession, the upper Cedar Mountain Formation (Short Canyon Member and Mussentuchit Member), has historically been linked to various regionally and continentally significant tectonic events, including Sevier fold‐and‐thrust deformation. However, the linkage between the Short Canyon Member and active Sevier tectonism has been unclear due to a lack of high‐precision age constraints. To establish temporal context, this study compares maximum depositional ages from detrital zircons recovered from the Short Canyon Member with that of a modified Bayesian age stratigraphic model (top‐down) to infer that the Short Canyon Member was deposited at ca 100 Ma, penecontemporaneous with rejuvenated thrusting across Utah [Pavant (Pahvant), Iron Springs and Nebo thrusts]. These also indicate a short depositional hiatus with the lowermost portion of the overlying Mussentuchit Member. The Short Canyon Member and Mussentuchit Member preserve markedly different sedimentary successions, with the Short Canyon Member interpreted to be composed of para‐autochthonous orogen–transverse (across the Sevier highlands) clastics deposited within a series of stacked distributive fluvial fans. Meanwhile, the muddy paralic Mussentuchit Member was a mix of orogen–transverse (Sevier highlands and Cordilleran Arc) and orogen–parallel basinal sediments and suspension settling fines within the developing collisional foredeep. However, the informally named last chance sandstone (middle sandstone of the Mussentuchit Member) is identified as an orogen–transverse sandy debris flow originating from the Sevier highlands, similar to the underlying Short Canyon Member. During this phase of landscape evolution, the Short Canyon Member – Mussentuchit Member depocentre was a sedimentary conduit system that would fertilize the Western Interior Seaway with ash‐rich sediments. These volcaniclastic contributions, along with penecontemporaneous deposits across the western coastal margin of the Western Interior Seaway, eventually would have lowered oxygen content and resulted in a contributing antecedent trigger for the Cenomanian–Turonian transition Oceanic Anoxic Event 2.

SEDIMENTOLOGIA, ESTRATIGRAFIA E MINERALOGIA DA FORMAÇÃO SOLIMÕES NO IGARAPÉ DIABINHO AFLUENTE DO RIO ENVIRA FEIJÓ-ACRE

The Igarapé Diabinho, is a tributary on the right bank of the Envira river, which is part of the Juruá river basin in the central region of the State of Acre (municipality of Feijó). It is in a U-type valley, carving out the sediments known as the Solimões Formation, considered as of Late Miocene to Pliocene age. In this stream, as well as in many regions of Acre, these sediments are partly covered by alluvial (fluvial-lacustrine) sediments from the Quaternary. The rocky exposures along the Diabinho stream show a succession of massive silt-clay sediments, green to cream in color, with vertical columnar concretions, scattered irregular calcite concretions, and gypsum venulations. These sediments are in turn covered by other compact sandy silts cemented by friable carbonates or even partially covered by a layer of horizontal discoid concretions of calcitic limestone. It is common in this area to locally occur accumulations of remains of fossil bones of vertebrates and plant trunks, constituting a basal conglomerate. For this study, three vertical stratigraphic profiles were described approximately 15 meters apart and rock samples were collected in addition to fossil bones along the profiles, which were subjected to granulometric analysis and mineralogical identification with the aid of X-rays diffraction (XRD), transmitted light optical microscopy and scanning electron microscopy (SEM/SED) with semiquantitative analysis. The sediments have a silty-sandy grain size with little clay, manganese, and carbonate concretions. The main minerals identified in these sediments by XRD and optical microscopy in thin sections were quartz, smectite, kaolinite, illite, albite, microcline, muscovite, chlorite, and hematite. In fragments of fossil vertebrate bones, scanning electron microscopy and semiquantitative analyses allowed the identification of the presence of apatite as the main constituent in addition to the presence of calcite, rhodochrosite, siderite, goethite, hematite, and gypsum.