Sequence Stratigraphy Research Articles

The missing sedimentological section linking the Neogene and quaternary of the Tandilia system and the Salado basin, Buenos Aires province, Argentina

The Tandilia system and the Salado basin are two adjacent morphostructural units located within the Argentine Pampean plain, each exhibiting distinct and independent geological histories. The Tandilia system preserves outcrops of Argentina's oldest Proterozoic rocks, while the sedimentary record of the Salado basin began during the Jurassic period. However, starting in the Cenozoic era, both units began to display common continental sedimentary fill characteristics. Despite this connection between the Tandilia system and the Salado basin, there is no unified lithostratigraphic framework for the Cenozoic that varies according to the studied localities. This study aims to define the stratigraphy of a sedimentary section that demonstrates the link between these morphostructural units from the Neogene onwards and to correlate it with the formal lithostratigraphic frameworks proposed in the literature. The analysis of well records led to the description of lithofacies and the establishment of facies associations, which were integrated to generate three correlation transects between the wells. Four facies associations were identified, three of which were fluvial and one aeolian. The analysis of these facies associations revealed that the sedimentary fill could be divided into two sedimentary sequences, lower sedimentary sequence and upper sedimentary sequence, separated by a sequence boundary marked by conglomeratic deposits. The definition of a stratigraphic framework for the middle section of the Del Azul creek basin and its correlation with the formal lithostratigraphic frameworks of the region indicate that from the Neogene onwards, both morphostructural units, the Tandilia system and the Salado basin, share sedimentological and tectonic characteristics. This study highlights the significance of subsurface information in understanding the geology of plain areas and its influence on regional geological evolution.

Sedimentary differentiation caused by glaciation and orogeny during the Ordovician–Silurian transition in the southern Sichuan Basin, China

The Wufeng–Longmaxi shales, which were deposited during the Ordovician–Silurian transition in the southern Sichuan Basin, exhibit distinct lithofacies transitions. The shift from organic-rich siliceous shale to organic-poor mixed shale and argillaceous shale is attributed to the influences of the Hirnantian glaciation and the Kwangsian Orogeny. Nevertheless, debates persist regarding the mechanisms underlying these significant lithofacies transformations. This study employs sequence stratigraphy, petrology, and geochemical analysis of key wells to unveil crucial insights. The findings indicate: 1) the Wufeng Formation to the Long-1 Member could be divided into two third-order sequences; 2) the waterbody underwent a transition from anoxic and strongly restricted conditions to oxic and moderately restricted conditions; and 3) the trend in formation thickness changed from an E–W orientation to a NE–SW orientation. The results suggest that considerable sediment condensation and anoxia resulting from glacier melting in the early Rhuddanian played a pivotal role in the formation of organic-rich siliceous shale. During the Middle Rhuddanian–Aeronian, the accelerated uplift caused by the Kwangsian Orogeny offset the transgression induced by glacier melting, leading to shallow water conditions and increased terrigenous influx. This diluted the organic matter content in the sediment, and subsequent turbidity currents altered sediment composition, driving the lithofacies transformation into organic-poor mixed shale and argillaceous shale. The study posits that the sedimentary differentiation in the southern Sichuan Basin during the Ordovician–Silurian transition is linked to the initiation and progression of the far-field effects of the Kwangsian Orogeny.

Facies associations and stratigraphic sequence of the Dhruma Formation (Middle Jurassic) at its type locality, Khashm adh Dhibi, Saudi Arabia

Facies associations and stratigraphic sequence of the Dhruma Formation (Middle Jurassic) at its type locality, Khashm adh Dhibi, Saudi Arabia

The tectonic setting of the late Ediacaran eastern Arabian basement (ca. 550 Ma): New geochronological and geochemical constraints from the basements of Oman and the United Arab Emirates

The thick Phanerozoic sedimentary cover lying above the Arabian Platform conceals extensive basement between the western Neoproterozoic domains of the Arabian Nubian Shield (ANS) and of the eastern Omani basement. The Neoproterozoic rocks entrained within salt domes that crop out within the United Arab Emirates (UAE) and Qatar are the only direct samples that allow us to investigate the tectonic history of the concealed Arabian basement domains before c. 550 Ma. This study focuses on the U-Pb geochronological and REE geochemical analysis of detrital zircon, apatite, titanite and rutile grains from the Zirku turbidites brought to the surface by halokinetic movements offshore UAE. These data are compared with new U-Pb and REE data from detrital heavy minerals of three metasedimentary members of the Omani Neoproterozoic Hatat Formation collected in the Saih Hatat window. The Omani metasedimentary units yield detrital titanite, zircon and apatite U–Pb ages that span from c. 2500 to 690 Ma, with an age maxima at c. 850 Ma, while the UAE unit yield ages from c. 2550 to 550 Ma with major age peaks at c. 1000, 820, 650 Ma. The analysis of the Omani stratigraphic sequence in the Saih Hatat window revealed that the rocks of the Neoproterozoic Hatat Formation yield similar age distributions of the Abu Mahara Group (lower Huqf Supergroup, exposed in central and southern Oman), and that the REE geochemical composition of the Hatat detrital apatite grains shares akin REE signature with the c. 550 detrital apatite of the Zirku Formation, with both being sourced from volcanic-arcs. These new geochronological and geochemical data, together with recent geophysical evidences, suggest that the basement of the UAE is originally part of the Oman tectonic domain and evolved as part of a volcanic-arc in an active margin at c. 550 Ma, which we interpret as part of the retro-arc of the Cadomian collision in between the Arabian and the Cadomian Taurides, Iran and Afghanistan terranes.

Zanclean to gelasian high-frequency sequences of the crotone basin (southern Italy): Architectural variability and forcing mechanisms

The Zanclean Belvedere Formation and the Gelasian Strongoli Sandstone, cropping out in the Neogene to Quaternary Crotone Basin, southern Italy, exhibit a high-frequency cyclicity consisting of 10°–101 m sequences, which stack in an aggradational to progradational pattern. These high-frequency sequences are bounded by ravinement surfaces and are usually composed of transgressive and regressive deposits of similar thickness. In particular, the high-frequency sequences of the Belvedere Formation are composed of a transgressive systems tract and of a highstand systems tract, whereas those of the Strongoli Sandstone likely record also forced regression in their upper part. Due to the vertical repetition of the studied high-frequency sequences and their similar architecture despite the different tectonic settings in which the two formations accumulated, a climatic/glacio-eustatic control associated with earth-orbital parameters is very likely, as also documented in coeval successions worldwide. This contribution refines the correlation between shallow-marine sequences and their deep-water counterparts, which preserve a better record of the Milankovitch cyclicity.

Applied sequence stratigraphy and heterogeneity assessment of the Eocene clastics in the Niger Delta Basin, Nigeria

Applied sequence stratigraphy and heterogeneity assessment of the Eocene clastics in the Niger Delta Basin, Nigeria

Magnetostratigraphy of the Punta Grohmann section (Dolomites, Italy): improving the chronology of the Ladinian/Carnian boundary

We provide the magnetostratigraphy of the Ladinian/Carnian Punta Grohmann stratigraphic section (Dolomites, Italy), calibrated with UPb ages from the literature (237.58 ± 0.04 Ma; 237.68 ± 0.05 Ma). The FO of ammonoid Zestoceras lorigae, the base of the vigens-densus palynomorphs Zone, and sequence stratigraphy suggest a Carnian age for the upper part of the section, which has been confirmed by the magnetostratigraphic correlation between Punta Grohmann and Prati di Stuores (Carnian GSSP). Additional magnetostratigraphic correlation between Punta Grohmann and key time-calibrated Ladinian–Carnian sections from the literature (e.g., Mayerling, Seceda, Rio Nigra) lead to a more precise age of the Carnian base (∼236.5 Ma) and to a better definition of the Middle–Late Triassic Geomagnetic Polarity Time Scale.

Rapid loading and deformation of soft sediments during emplacement of a lava delta in the Vøring Basin, Mid-Norwegian Margin

Abstract Soft sediment deformation structures may form when denser sediments or fluids are deposited on or flow over unlithified and less dense sediments. This study presents a seismic geomorphological study of the basal contact between an extrusive volcanic sequence and underlying sediments, defining the ‘Base Basalt’ surface, on the Mid-Norwegian Margin. This contribution focuses in particular on the development of geomorphological features related to the rapid loading of a several 100 m-thick lava delta package of hyaloclastite onto poorly consolidated sediments of the pre-volcanic sedimentary basin fill. Seismic horizons, sequence boundaries, volcanic facies units and attribute maps are used to characterize the seismic geomorphological features imaged within a high-quality 3D seismic cube. The ‘Base Basalt’ horizon and attribute maps reveal incised channels and a network of polygonal to irregular depressions and ridges described here as an ‘egg-box network’. More than 150 depressions, with a typical diameter of 1 km and a depth of 100 m, have been mapped. The deformation features, which are restricted to the base of the Lava Delta seismic facies unit, are interpreted to be the result of rapid loading of the Lava Delta onto poorly consolidated unlithified pre-volcanic sediments. This study presents new evidence for the dynamic nature of the transition between sedimentary basins and large-scale volcanism found along volcanic margins and basins associated with rapid volcanic deposition.

Seismic 3D full-horizon tracking based on a knowledge graph to represent the stratigraphic sequence relationship

Seismic 3D full-horizon tracking is a fundamental and crucial step in sequence analysis and reservoir modeling. Existing automatic full-horizon tracking approaches lack effective methods for representing the stratigraphic sequence relationships in seismic data. However, the inability to represent the stratigraphic sequence relationships fully and accurately makes it challenging to address discontinuous areas affected by faults and unconformities. To address this issue, we develop a knowledge graph representing the stratigraphic sequence relationship, which enables the simultaneous extraction of all horizon surfaces once the stratigraphic distribution of the seismic data is obtained. This method first generates horizon patches and calculates the fault attributes, followed by the construction of an initial knowledge graph that characterizes the overall distribution of horizon patches and faults. The initial knowledge graph comprises nodes and edges. The nodes represent horizon patches, and their attributes cover the geographical location information of the patches and faults. Simultaneously, the edges represent the relationship between the horizon patches, including the stratigraphic sequence relationship, and their attributes illustrate the potential for connecting these patches. Furthermore, we introduce a multilayer knowledge graph based on the point-set topology to fuse the nodes. This allows for the continuous merging of the horizon patches to obtain horizon surfaces across discontinuities with the constraints of fault attributes and stratigraphic sequence relationships in 3D space. Synthetic and field examples demonstrate that our approach can effectively represent stratigraphic sequence relationships and accurately track horizons located in discontinuous areas with faults and unconformities.

Stratigraphical and sedimentological controls on the distribution of Cloudina bioclastic accumulations in the terminal Ediacaran Tamengo Formation (Corumbá Group), Brazil

The appearance of the early biomineralized skeletons during the latest Ediacaran was one of the most important evolutionary gains for the ancient animals' lineage. This evolutionary innovation likely represents a pivotal shift in ecology and the interactions between the geosphere and biosphere. Among these fossils, Cloudina stands out as the oldest macroscopic biomineralized metazoan that achieved widespread distribution. However, the complex interplay between sedimentation, preservation, and the vertical distribution of bioclastic accumulations in the Ediacaran strata remains unexplored. The Ediacaran Tamengo Formation (Western Brazil) records thick shallow water deposits and preserves several stratigraphic intervals that contain bioclastic-rich beds formed by Cloudina remains. This unit represents a window for investigating the role of the earliest truly and their impact on Ediacaran marine environments. Our investigation aims to examine the sedimentology and taphonomy of Cloudina within the Tamengo Formation in Brazil to test the hypothesis that the emergence of skeletal hard parts influenced sedimentary depositional processes. To achieve this goal, we combine bioclastic remains and facies/microfacies analysis, taphonomy, and sequence stratigraphy. Our approach involves analyzing the distribution of bioclasts in correlation with stratigraphy and microfacies. By doing so, we aim to forecast the presence of bioclastic accumulations across a mixed siliciclastic–carbonate ramp section. Our findings reveal variability in bioclast sizes among different sites, suggesting a correlation with environmental factors. Furthermore, our study underscores the significance of comparing bioclast accumulations between Precambrian and Phanerozoic deposits, emphasizing their broad utility in understanding evolutionary and environmental shifts over time.

Complete chloroplast genome of the Malus baccata var. gracilis provides insights into the evolution and phylogeny of Malus species.

Malus baccata (L.) var. gracilis (Rehd.) has high ornamental value and breeding significance, andcomparative chloroplast genome analysis was applied to facilitate genetic breeding for desired traits andresistance and provide insight into the phylogeny of this genus. Using data from whole-genomesequencing, a tetrameric chloroplast genome with a length of 159,992 bp and a total GC content of36.56% was constructed. The M. baccata var. gracilis chloroplast genome consists of a large single-copy sequence (88,100 bp), a short single-copy region (19,186 bp), and two inverted repeat regions, IRa(26,353 bp) and IRb (26,353 bp). This chloroplast genome contains 112 annotated genes, including 79protein-coding genes (nine multicopy), 29 tRNA genes (eight multicopy), and four rRNA genes (allmulticopy). Calculating the relative synonymous codon usage revealed a total of 32 high-frequencycodons, and the codons exhibited a biased usage pattern towards A/U as the ending nucleotide.Interspecific sequence comparison and boundary analysis revealed significant sequence variation in thevast single-copy region, as well as generally similar expansion and contraction of the SSC and IRregions for 10 analyzed Malus species. M. baccata var. gracilis and Malus hupehensis were groupedtogether into one branch based on phylogenetic analysis of chloroplast genome sequences. Thechloroplast genome of Malus species provides an important foundation for species identification, geneticdiversity analysis, and Malus chloroplast genetic engineering. Additionally, the results can facilitate theuse of pendant traits to improve apple tree shape.

Sequence stratigraphy of the foraminiferal zones F9700 and F9800 in the Niger Delta: A comprehensive litho-sequence approach

Understanding how variations in relative sea level affect reservoir structure requires a thorough understanding of sequence stratigraphy. A detailed sequence stratigraphic investigation was performed on the OML X field to uncover and establish links between concurrently originating hydrocarbon reservoir deposits. The analysis of major stratigraphic surfaces, such as maximum flooding surfaces and sequence borders, was made possible by the integration of well log and biostratigraphic data. The research region includes two palynological subzones, P850 and P860, discovered in the foraminifera zones F9700 (Haplophragmoides 24) and F9800 (Bolivina 46). The study discovered two distinct chronological limitations, which occurred approximately 6.7 million years ago (Ma) and 5.6 Ma, respectively. Furthermore, two maximum flooding surface events were discovered, estimated to have happened at 6.0 Ma and 5.0 Ma. When well log and biostratigraphic data were combined, it was simpler to identify sequences 1, 2, and 3, which correspond to the LST, TST, and HST. The implementation of this detailed methodology facilitated the identification and linking of hydrocarbon sources inside the high- and low-stand system tracts. The findings of the study demonstrated a good link between well-logged log data and biostratigraphy utilizing well-accepted primary stratigraphic surfaces and depositional histories. Furthermore, using fault interpretation and correlation approaches has enhanced our understanding of reservoir geometry and continuity in the field, making it easier to discover potential reservoirs.

Stratigraphic-sedimentary evolution of a mixed siliciclastic-carbonate system in the Huizhou Sag of the Pearl River Mouth Basin, Northern South China Sea

Mixed siliciclastic-carbonate systems are regulated interactively by factors such as siliciclastic sediment supply, carbonate production, sea-level change, tectonism, and climate conditions. These systems record vital information that aids in understanding ancient environments. This study used a merged 3D seismic volume, in conjunction with over 100 industrial wells, to systematically investigate the stratigraphic-sedimentary evolution of such a system within the Huizhou Sag of the Pearl River Mouth Basin, located on the northern continental shelf of the South China Sea. In total, six major sequence boundaries were identified for the Zhujiang Formation within the area, thus subdividing the interval into five typical third-order depositional sequences. Each of these sequences can be divided into a transgressive and a highstand systems tract. Lowstand or falling stage systems tracts were also recognized, the deposition of which was potentially in response to the uplifting process of the Dongsha Rise. During the deposition of the Zhujiang Formation, the Huizhou Sag may have undergone a sequential evolutionary history from delta-shore, to delta-shore-tidal-lagoon, to delta-shore-carbonate, and finally to delta-shore-shallow marine systems. This evolution responded to a varying degree of mixing processes, which was mainly regulated by siliciclastic sediment supply, confined paleomorphology, and local oceanic currents. Furthermore, the deposition of the Zhujiang Formation in the Huizhou Area was time-equivalent with the spreading process after the ridge jump of the South China Sea (23–16.5 Ma), providing valuable insights into sea-level fluctuations, provenance changes, and tectonic evolution. Our results may also shed light on the evaluation of lithologic traps and hydrocarbon sweet spots within mixed siliciclastic-carbonate systems.

Variations of sedimentary environment under cyclical aridification and impacts on eodiagenesis of tight sandstones from the late Middle Jurassic Shaximiao Formation in Central Sichuan Basin

Understanding eodiagenesis is essential to decoding the diagenetic pathways of tight sandstones that act as excellent unconventional oil & gas reservoirs. Great paleoclimate change is capable of influencing eodiagenetic processes of tight sandstones through variations of sedimentary environment. However, it is less noted how climate gradients between the greenhouse and the hothouse conditions impact the eodiagenesis of tight sandstones. We examined eodiagenetic processes that has been operated in the Shaximiao Formation sandstones using petrographic observation, scanning electron microscopy, geochemistry, and XRD analysis to reveal impacts of the transitional climate changes on the differential eodiagenesis and implications for the diagenesis-porosity evolution. Based on sequence stratigraphy, the Shaximiao Formation is divided into four sub-members SXM1, SXM2, SXM3, and SXM4, respectively. Dark sandstones and mudstones mainly occurred in the SXM1 and the SXM2. Grey-green clastic rocks are dominant in the SXM3, whereas red mudstones frequently appear in the SXM4. Paleoclimate indices denote that a cyclical aridification from the warm-humid to hot-semiarid conditions took place from the SXM1 to the SXM4. It could have been caused by the megamonsoon effect and the paleogeographic shift along with the breakup of the Pangaea supercontinent. Combined with the migration of depocenters, the paleoclimate change resulted in transformation of sediment provenances from mafic igneous rocks to quartzose sedimentary rock along with the decreasing textural maturity. Therefore, sedimentary environments varied from the high-saline to low-saline and from low-oxygen to high-oxygen conditions respectively, which had a crucial impact on eodiagenetic cements which were formed in the Shaximiao Formation. Chlorite and laumontite cement precipitation was promoted by high-saline alkaline fluids. Chlorite proportions show an arched trend from the SXM1 to the SXM4, compatible with those of primary and secondary porosities. In contrast, laumontite proportions exhibit a decreasing variation from the SXM1 to the SXM4. High percentages of early cements are favorable to improving resistance to the compaction and preservation of primary pores. However, high chlorite (>5%) and laumontite (>10%) proportions are destructive for the reservoir quality. Large quantities of laumontite cements occupy primary pores and impede diagenetic fluids flowing and are not favorable to the dissolution. By contrast, an excess of chlorite cements can be dissolved to produce secondary pores during the organic acid release. Thus, the SXM2 is potential as a reservoir for oil & gas. Therefore, those eodiagenetic cements can control the late diagenetic evolution and the reservoir quality. Observations made here have implications for understanding tight sandstone reservoirs elsewhere in the world.

Sequence lithofacies paleogeography evolution of the Middle Permian Maokou Formation in the northwest margin of the Sichuan Basin

Due to the present tectonic and stratigraphic distribution characteristics in the northwest margin of the Sichuan Basin are complex, which restricts the understanding of sequence lithofacies paleogeography of the Middle Permian Maokou Formation. To investigate the process of tectonic–sedimentary evolution, basin-margin outcrop and intra-basin well and seismic data were used. The results show two structural sequences, namely, SSQ1 and SSQ2, and five third-order sequences, namely, SQ1–SQ5, in the Middle Permian Maokou Formation. SSQ1, with stable formation thickness, shows a slow transgression–fast regression sequence structure. SSQ2 shows a fast transgression–slow regression sequence structure in the area with large thickness and a sustained transgression–fast regression sequence structure in the area with small thickness owing to thickness differentiation caused by tectonic subsidence. Sedimentological analysis shows that sequences SQ1–SQ2 mainly consist of carbonate-ramp sediments, the sedimentary facies of which change from intermediate ramp to outer ramp as the area depressed topographically from south to north. Sequences SQ3–SQ5 mainly consist of rimmed carbonate platform sediments; the platform margin turned up along Shuangyushi–Jian’ge–Yuanba, and the region to the north subsided rapidly to form slope-basin facies. Lithofacies paleogeography in the Middle Permian epoch shows that the northwest margin of the Sichuan Basin was dominated by extensional stresses in northeast and northwest directions. Tectonic activities have a dominant control on the distribution of two structural sequences and the evolution of carbonate platform types in the Maokou Formation, and the sea-level change has a dominant control on third-order sequence boundaries and sedimentary facies migration. Thus, the Middle Permian tectono-sedimentary evolution model of the northwest margin of the Sichuan Basin is established. Research findings may offer new ideas and theoretical support to promising facies exploration in the Maokou Formation in the northwest margin of the Sichuan Basin.

Application of geophysical well logs in solving geologic issues: Past, present and future prospect

Geophysical well logs are widely used in geological fields, however, there are considerable incompatibilities existing in solving geological issues using well log data. This review critically fills the gaps between geology and geophysical well logs, as assessed from peer reviewed papers and from the authors’ personal experiences, in the particular goal of solving geological issues using geophysical well logs. The origin and history of geophysical logging are summarized. Next follows a review of the state of knowledge for geophysical well logs in terms of type of specifications, vertical resolution, depth of investigations and demonstrated applications. Then the current status and advances in applications of geophysical well logs in fields of structural geology, sedimentary geology and petroleum geology are discussed. Well logs are used in structural and sedimentary geology in terms of structure detection, in situ stress evaluation, sedimentary characterization, sequence stratigraphy division and fracture prediction. Well logs can also be applied in petroleum geology fields of optimizing sweet spots for hydraulic fracturing in unconventional oil and gas resource. Geophysical well logs are extending their application in other fields of geosciences, and geological issues will be efficiently solved via well logs with the improvements of advanced well log suits. Further work is required in order to improve accuracy and diminish uncertainties by introducing artificial intelligence. This review provides a systematic and clear descriptions of the applications of geophysical well log data along with examples of how the data is displayed and processed for solving geologic problems.

Sequence Stratigraphic Analysis of the Volcanic Rock–Evaporite–Clastic Rock Symbiotic Zone in the Fourth Member of the Shahejie Formation in the South of Laizhou Bay

Laizhou Bay Sag is a typical continental rift lake basin, which is affected by strike–slip activity, salt rock activity, volcanic activity, and paleoclimate change in the Tanlu fault zone, where three major lithologies—volcanic rock, clastic rock, and evaporite—mainly develop. In order to determine the sequence correspondence between the different lithologies in the study area based on drilling, logging data, and seismic data, it is determined that the fourth member of the Shahejie Formation in the southern Laizhou Bay mainly develops three types of sequences: clastic rock type sequences, salt lake type sequences, and volcanic rock/clastic rock type sequences. Two second-order sequence boundaries (SBs3L, SBs4L) and one third-order sequence boundary (SBs4U) were identified, and the principle of three divisions of system tracts (LST, TST, HST) and sedimentary processes in different types of sequences were determined by analyzing the stacking patterns of different sequences. Compared with the previous research results, this study provides a more detailed analysis of the sequence boundary definition of different blocks and different lithologic strata, and it improves the previous general sequence stratigraphic division method. Based on the study of distinct types of sequences, a unified stratigraphic framework is established in the whole zone, and the stratum thickness distribution of the fourth member of Shahejie Formation is smaller in the southwest and larger in the northeast. The study area is generally filled with pyroclastic rocks–evaporite–clastic rocks, changing from fan delta–saline lake filling to braided river delta–freshwater lake–fan delta filling from bottom to top. A sequence stratigraphic model for the comparison of steep slope–gentle slope differences is established to provide guidance for future oil and gas field exploration and development.

First record of Reticulinella? kaeveri in the Laffan and Ilam formations (Zagros fold and thrust belt, SW Iran): new constraints on the chronostratigraphic calibration of the Arabian Plate sequence stratigraphy

Over the past two decades, sequence stratigraphy has proven to be a valuable tool in addressing challenges arising from the inconsistent application of lithostratigraphic nomenclature across diverse geological provinces. It has been particularly successful in achieving regional correlations within the Cretaceous deposits of the Arabian Plate. The key sequence stratigraphic surface in the currently adopted standard sequence stratigraphic scheme is the K150 SB, marking the transition from a passive to an active margin along the eastern edge of the Arabian plate. Despite its importance, the chronostratigraphic age of this surface is poorly constrained. In the Zagros FTB, the uppermost part of the Sarvak Formation, just below the K150 SB, was recently assigned to the upper part of middle Turonian to upper Turonian, based on the presence of Reticulinella? kaeveri. Our research reveals that the range of R.? kaeveri extends above the K150 SB as this species is also present in the Laffan and base of Ilam formations. The Last Occurrence of this taxon provides a new chronostratigraphic marker of the upper Turonian within the Ilam Formation. This finding proves that more Turonian deposit are present in the study area than was previously recognized. We have studied the deposits enclosing the K150 SB in outcrop sections and wells along a transect from basin to platform margin to inner platform setting. Based on planktonic foraminifera and calcareous nannofossils biostratigraphy of basinal sections and sequence stratigraphic correlation to carbonate platform sections, the age of the uppermost part of the Sarvak Formation, immediately below the K150 SB, is firmly constrained within the interval lower Turonian–lower part of middle Turonian. Sequence stratigraphic correlation from basin to platform interior reveals also that the oldest deposits above the K150 SB are not younger than late Turonian. Our new data represents a significant improvement in the chronostratigraphic calibration of sequence stratigraphy in the Cretaceous of the Zagros fold-and-thrust belt.

Extremely high resolution XRF core scanning reveals the Early Triassic depositional history of the Montney Formation in northeastern British Columbia, Canada

The Montney Formation is a laterally extensive, fine-grained sedimentary unit in western Alberta and northeastern British Columbia, and a major target of hydrocarbon exploration. It also retains a complete record of the Early Triassic epoch, a time when the biosphere was recovering from the effects of the end-Permian mass extinction. An industry well provides a full-diameter core of the complete distal Montney Formation in northeastern British Columbia (over 350 m thick), with stratigraphic age control provided by conodont biostratigraphy and regional correlations. For this study, the core was scanned using an ITRAX X-ray fluorescence spectrometer, at centimeter-scale resolution. The resulting dataset (over 37,000 individual measurements) provides an extremely high level of resolution for a deep-time geochemical study. While the data generated by this instrument are semiquantitative, they can be calibrated by correlating them with more conventional ICP-MS and XRF measurements of select samples. Using this method, we assessed the reliability of each of the elemental data series, and where possible converted them to quantitative geochemical measurements. These calibrated measurements serve as the basis for our detailed reconstruction of the Montney Formation's depositional history.The distal Montney depositional basin, including the location of the c-65-F core, was euxinic immediately following the end-Permian mass extinction, and accumulated sediments from the rapidly eroding margin of western North America. Conditions stabilized somewhat in the Dienerian, with oxic bottom water and a trend toward more compositionally mature sediment, but conditions of widespread euxinia and rapid erosion of the North American craton recurred in the early Smithian, earlier than this global crisis has been recognized elsewhere. Above the middle-upper Montney sequence boundary, in the overlying Spathian succession, local effects predominate. Coastal upwelling resumed in the basal Spathian, though the Montney depositional basin was soon cut off from the global ocean by uplift of the Yukon-Tanana arc bounding the basin to the west. Restricted conditions, with euxinic bottom water, were punctuated by oxic intervals, when rising sea level allowed the basin to freely exchange water with the open ocean. Intervals of restriction became progressively less acute in the upper Spathian.

Glacier fluctuation chronology since the latest Pleistocene at Mount Rainier, Washington, USA

Abstract Large stratovolcanoes in the Cascade Range have high equilibrium-line altitudes that support glaciers whose Holocene and latest Pleistocene advances are amenable to dating. Glacier advances produced datable stratigraphic sequences in lateral moraines, which complement dating of end moraines. New mapping of glacial deposits on Mount Rainier using LIDAR and field observations supports a single latest Pleistocene or early Holocene advance. Rainier R tephra overlies deposits from this advance and could be as old as >11.6 ka; the advance could be of Younger Dryas age. Radiocarbon ages on wood interbedded between tills in the lateral moraines of Nisqually, Carbon, and Emmons glaciers and the South Tahoma glacier forefield suggest glacier advances between 200 and 550 CE, correlative with the First Millennium Advance in western Canada, and during the Little Ice Age (LIA) beginning as early as 1300 CE. These results resolve previous contradictory interpretations of Mount Rainier's glacial history and indicate that the original proposal of a single pre-Neoglacial cirque advance is correct, in contrast to a later interpretation of two advances of pre- and post-Younger Dryas age, respectively. Meanwhile, the occurrence of the pre-LIA Burroughs Mountain Advance, interpreted in previous work as occurring 3–2.5 ka, is questionable based on inherently ambiguous interpretations of tephra distribution.