Sequence Architecture Research Articles

Correlation and sequence stratigraphic interpretation of the lithostratigraphic Snake Cave Interval: Implications for hydrocarbon reservoir prospectivity between the southeast Blantyre and northwestern Neckarboo Sub-basins, Darling Basin, southeastern Australia

Correlation and sequence stratigraphic interpretation was conducted on the upper Lower through upper Middle Devonian sandstones of the Snake Cave Interval succession between the southeast Blantyre and northwestern Neckarboo sub-basins across the central Darling Basin. This article necessitated the definition and use of many sedimentary lithotypes related to different facies associations and depositional environment criteria for the purpose of establishing the sequence stratigraphy to aid hydrocarbon exploration of the studied areas. The data set used a combination of wireline logs, core/cutting data and analysis of the paleo-environments of sedimentary facies from three wells. The sedimentological analysis showed that the Snake Cave Interval section presents three different facies associations, which are visible in both vertical and lateral successions, and are characterised as: meandering and braided fluvial facies associations with minor fluvio-shallow lacustrine complex facies associations. The Snake Cave Interval section in the studied areas is consistently defined by six third-order depositional sequences informally named SCS1, SCS2, SCS3, SCS4, SCS5 and SCS6 in the Nyngynderry-1 and Mount Emu-1 exploration wells, and the Kewell East-1 stratigraphic well. All the stratal patterns in the internal sequence stratigraphic units are asymmetric and marked by lowstand, transgressive and highstand systems tracts separated by sequence boundaries, maximum flooding surfaces and transgression surfaces with unique gamma-ray log response characteristics calibrated by particular lithologic aspects. These are all incorporated within the sequence stratigraphic approach to hydrocarbon reservoir prediction. The stratigraphic architecture of the third-order depositional sequences presented here in our study has implications for the hydrocarbon potential of sandstone reservoirs in the southeastern Darling Basin including the Snake Cave Interval succession targets.

The character and origin of sequence architecture in the arid climate zone: A case of the Lower Submember of the Fourth Member of Shahejie Formation in the Bonan Sub-Sag

The early Paleogene experiences a prolonged global hyperthermal period. The Lower Submember of the Fourth Member of Shahejie Formation (Es4x) of early Paleogene deposits a set of unique red sequence with influences of global hyperthermal events. Many researches focus on paleoclimate reconstruction of global hyperthermal period. However, few researches concern sequence architecture and sedimentary response in this extreme climate background. As the sequence architecture and sedimentary response record the paleoclimate, the character and origin of them can provide signals to reconstruct paleoclimate. Thus, this research investigates paleoclimate, character and origin of sequence architecture to reveal inter relationships and provide basis for paleoclimate reconstruction. The climate evolution and its sediment supply responses controlled the development of sequence architecture and reconstructed the different sedimentary responses. The periodic evolution of climate and sediment supply response results in the T-R cycle and sand body enrichment in the TST stage. The sand bodies of the TST stage concentrate in the LTST stage as frequency and amplitude of fluctuations are higher. The LTST stage developed large scale sand bodies with longest distance transportation in. Subsequently, the drier and stable climate continues to decreases sediment supply during the RST stage. Sand bodies shrunk to the edge of Sub-sag.

NORAD-induced Pumilio phase separation is required for genome stability.

Liquid-liquid phase separation is a major mechanism of subcellular compartmentalization1,2. Although the segregation of RNA into phase-separated condensates broadly affects RNA metabolism3,4, whether and how specific RNAs use phase separation to regulate interacting factors such as RNA-binding proteins (RBPs), and the phenotypic consequences of such regulatory interactions, are poorly understood. Here we show that RNA-driven phase separation is a key mechanism through which a long noncoding RNA (lncRNA) controls the activity of RBPs and maintains genomic stability in mammalian cells. The lncRNA NORAD prevents aberrant mitosis by inhibiting Pumilio (PUM) proteins5-8. We show that NORAD can out-compete thousands of other PUM-binding transcripts to inhibit PUM by nucleating the formation of phase-separated PUM condensates, termed NP bodies. Dual mechanisms of PUM recruitment, involving multivalent PUM-NORAD and PUM-PUM interactions, enable NORAD to competitively sequester a super-stoichiometric amount of PUM in NP bodies. Disruption of NORAD-driven PUM phase separation leads to PUM hyperactivity and genome instability that is rescued by synthetic RNAs that induce the formation of PUM condensates. These results reveal a mechanism by which RNA-driven phase separation can regulate RBP activity and identify an essential role for this process in genome maintenance. The repetitive sequence architecture of NORAD and other lncRNAs9-11 suggests that phase separation may be a widely used mechanism of lncRNA-mediated regulation.

Palaeoecological and palaeoenvironmental analyses of Cenomanian–early Turonian macrobenthic faunas from the northern Eastern Desert of Egypt

The palaeoecology and palaeoenvironments of the Cenomanian–lower Turonian succession in the northern Eastern Desert of Egypt are interpreted, based on a detailed study of macrofaunal assemblages and sedimentary facies. The abundant molluscs and echinoids of the mixed carbonate-siliciclastic Galala and Abu Qada formations have been studied in three sections with ammonites that provide a well-correlated stratigraphical framework. Three unconformities (two Cenomanian sequence boundaries and a first Turonian one) bound two third-order depositional sequences. Facies development shows a strong relationship to the sequence architecture recognised. In addition, the facies characteristics indicate depositional palaeoenvironments ranging from lagoonal to deep subtidal settings on a homoclinal carbonate ramp that was proximally influenced by clastic input. The macrobenthic taxa identified in 51 samples, collected from the sections studied, are grouped into seven assemblages (A–G) that are described and interpreted as remnants of communities. The faunal distribution and trophic structure of most of the assemblages recorded confirm fully oxygenated and euhaline shallow-marine environments with mesotrophic productivity level, i.e., relatively stable and low-stress conditions. The trophic structure of some other assemblages, in contrast, reflects the influence of particular environmental parameters, dissolution of aragonitic shells and/or sample size effects. Environmental parameters controlling the faunal distribution include substrate consistency, bathymetry, water energy, surface-water productivity, rate of sedimentation and oxygen availability. The integrated litho- and biofacies results certify that the sequences were deposited during an interval dominated by different perturbations that resulted in a wide spectrum of depositional features and significant palaeoecological variations.

Microbial carbonate sequence architecture and depositional environments of Member IV of the Late Ediacaran Dengying Formation, Gaoshiti–Moxi area, Sichuan Basin, Southwest China

The recent discovery of the Anyue gas field, with huge reserves, has great potential for ultradeep gas production in carbonate reservoirs. Previous exploration and exploitation of Member IV of the Dengying Formation in the Gaoshiti–Moxi area deposited during the Late Ediacaran have provided useful insight into palaeo‐gas reservoirs, and geological significance of the Precambrian microbial carbonate strata. In this study, the depositional sequence architecture has been established and typical environments from Member IV of the Dengying Formation in the Gaoshiti–Moxi area have been reconstructed through detailed sedimentological analysis of cores, petrophysical data, well‐logging data and seismic interpretation. One third‐order sequence was identified, which is subdivided into seven fourth‐order sequences and 18–19 fifth‐order sequences. The third‐order sequence is bounded by denudation surfaces or onlap surfaces, and composed of transgressive system tracts and highstand system tracts. The fourth‐order sequences are bounded by instantaneously exposed punctuated surfaces or lithology and lithofacies transition surfaces, featured by specific lithological cycles, such as ‘lower microcrystalline dolomite, middle intraclastic dolomite and sparry thrombolite, and upper intraclastic dolomite’, ‘middle–lower sparry thrombolite and upper microcrystalline dolomite and sparry thrombolite’, ‘lower micritic thrombolite, middle micritic dolomite, and upper sparry thrombolite and laminites’, and ‘lower microcrystalline dolomite, middle intraclastic dolomite and argillaceous or micritic dolomite, and upper intraclastic dolomite’. The sequence characteristics reveal that periodic high‐frequency sea‐level change and palaeogeomorphology are controlling factors affecting sequence development, which lay a significant foundation for reservoir development. During the depositional period, a tidal flat on a restricted carbonate platform is well‐developed, allowing the identification of 16 microfacies, 13 microfacies associations, and 6 seismic facies. Inter‐lower tidal flats are widely developed with band‐shaped mound–bank complex, microbial mound, and shoal on the platform margin. On the inner platform, patchy microbial mounds, mound–flat combinations, and inter‐shoal/microbial mounds are developed in the Gaoshiti area, whereas patchy shoals and shoal–flat combinations are developed in the Moxi area. During the early depositional period of Member IV of the Dengying Formation, the microbial mounds and shoals were developed on the platform margin. The dolomitic flat and inter‐shoal/microbial mounds are mainly developed on the inner platform with little microbial mound and shoal deposition. During the late depositional period of Member IV of the Dengying Formation, large‐scale microbial mounds and shoals are sustainably and stably developed on the platform margin; enlarged dolomitic flat, patchy microbial mounds, and patchy shoals are predominantly developed in the platform interior with inter‐shoal/microbial mounds dying out.

Evolution of a complex early Permian coarse-grained shoreline along a rift basin margin

ABSTRACT Tectonic activity in extensional basins has a profound control on accommodation and sediment supply through the interplay between footwall uplift and hanging-wall subsidence, and thus largely influences the three-dimensional architecture of syn-rift sequences. This is emphasized in areas close to major rift-border faults, where steep coastal reliefs and fluvial gradients produce compound facies zonation and stratigraphic styles with strong lateral variability. The lower Permian High Cliff Sandstone was deposited in an array of shallow marine environments along the margin of the northern Perth Basin during a protracted late Paleozoic rifting episode in Western Australian basins. The formation is composed of fluvio-deltaic and nearshore strata sharply overlying a thick succession of offshore mudstone that was deposited during a phase of tectonic quiescence. This basal contact likely reflects submarine erosion and is, therefore, interpreted as a regressive surface of marine erosion generated in response to forced regression. The facies arrangement consisting of interbedded sandstone, conglomerate, and heterolithic facies chiefly records the evolution of a low- to high-gradient paleoshoreline punctuated by coastal streams, steep sea cliffs, and back-barrier lagoons. Extraformational outsized clasts were probably emplaced by the erosion of exhumed basement and older sedimentary rocks through fluvial incision, wave sapping, or landsliding. The along-strike variability between low- and high-gradient shoreline deposits indicates a dynamic depositional setting with a complex tectonic influence. The basal regressive surface of marine erosion is attributed to footwall uplift during the early reactivation stage of basin-bounding normal faults and, therefore, records the initiation of a new syn-rift phase in the northern Perth Basin.

Mixing Models as Integer Factorization: A Key to Sample Preparation With Microfluidic Biochips

Microfluidic biochips have recently emerged with significant promise and versatility in automating a variety of biochemical protocols on a tiny chip. Sample preparation, which involves the mixing of fluids with a specified target ratio in the minuscule scale, is an essential component of these protocols. Algorithms that optimize on-chip sample-preparation cost and time are closely intertwined with the underlying mixing model, mixing sequence, and fluidic architecture. Although numerous mixing models have been studied in the literature, their impact on the dynamics of mixing steps is hitherto not fully understood. In this article, we show that various mixing models can be envisaged in the light of prime factorization of integers thus establishing a connection among mixing algorithms, chip architectures, and performance. This insight has led to the development of the proposed factorization-based dilution algorithm ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FacDA</i> ) considering a generalized mixing model suitable for micro-electrode-dot-array (MEDA) biochips. It further leads to target volume oriented dilution algorithm ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TVODA</i> ) to cater to user’s demand for an output with a given volume. We formulate the optimization problem on the fabric of the satisfiability modulo theory (SMT) while determining mixing sequences. Simulation results on a large number of test-cases reveal that <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FacDA</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TVODA</i> outperform the state-of-the-art dilution algorithms for MEDA biochips with respect to reactant cost, mixing time, and waste production.

Comprehensive analysis of coding sequence architecture features and gene expression in Arachis duranensis.

Coding sequence (CDS) architecture affects gene expression levels in organisms. Codon optimization can increase the gene expression level. Therefore, understanding codon usage patterns has important implications for research on genetic engineering and exogenous gene expression. To date, the codon usage patterns of many model plants have been analyzed. However, the relationship between CDS architecture and gene expression in Arachis duranensis remains poorly understood. According to the results of genome sequencing, A. duranensis has many resistant genes that can be used to improve the cultivated peanut. In this study, bioinformatic approaches were used to estimate A. duranensis CDS architectures, including frequency of the optimal codon (Fop), polypeptide length and GC contents at the first (GC1), second (GC2) and third (GC3) codon positions. In addition, Arachis RNA-seq datasets were downloaded from PeanutBase. The relationships between gene expression and CDS architecture were assessed both under normal growth as well as nematode and drought stress conditions. A total of 26 codons with high frequency were identified, which preferentially ended with A or T in A. duranensis CDSs under the above-mentioned three conditions. A similar CDS architecture was found in differentially expressed genes (DEGs) under nematode and drought stresses. The GC1 content differed between DEGs and non-differentially expressed genes (NDEGs) under both drought and nematode stresses. The expression levels of DEGs were affected by different CDS architectures compared with NDEGs under drought stress. In addition, no correlation was found between differential gene expression and CDS architecture neither under nematode nor under drought stress. These results aid the understanding of gene expression in A. duranensis.

Underthrusting of the Tarim Lithosphere Beneath the Western Kunlun Range, Insights From Seismic Profiling Evidence

AbstractUplift of the western Kunlun range results from the Indian indentation into Eurasia and induced underthrusting of the Tarim lithosphere. This underthrusting keeps pace with migration of the western Kunlun foreland basin. The basin‐scale sequences provide a decipherable record of the migration. To quantify the underthrusting, we analyzed a ∼323.2‐km‐long seismic profile crossing the middle segment of the western Kunlun foreland. We traced seismic reflectors to investigate the architecture of the foreland sequences and assigned ages of reflectors by correlating them with the dated outcropping sections. The foreland sequences consist of four layers. The lowermost Layer 1 starts to lap on the preforeland unit at ∼40 Ma, indicating that the Cenozoic western Kunlun initiated slightly prior to ∼40 Ma. Layer 2 shows a large sharp step northward to exceed the forebulge at ∼25 Ma, suggesting that the modern geomorphology of the Tarim Basin took shape. The southwestern boundary of Layer 4 migrates northeastwards by a fold row relative to that of Layer 3. The gradual retreat of reflector terminations from ∼40 to ∼30 Ma suggests that the Tarim lithosphere is viscoelastic. The linear fitting of the forelandward envelop of reflector termination sites since ∼30 Ma indicates that the Tarim lithosphere underthrusted at an average rate of ∼8.18 mm/yr. This rate comprises the shortening rate of ∼3.8–5.7 mm/yr and the western Kunlun latitudinal propagation rate of ∼4.4–2.5 mm/yr. The abrupt increase in sedimentation rate since ∼11 Ma suggests that western Kunlun had reached its current elevation.

The Sequence, Structure and Function of the Plant Stress Protein LEA3

LEA3 proteins, a family of abiotic stress proteins, are defined by the presence of a tryptophan-containing motif, which we name the W-motif. We used bioinformatic, biochemical and biophysical techniques in order to better understand this poorly characterized protein group. A comprehensive analysis of these sequences revealed four N-terminal motifs, as well as two previously undiscovered C-terminal motifs that contain conserved acidic and hydrophobic residues. The general architecture of the LEA3 sequences consisted of an N-terminal motif with a potential mitochondrial transport signal and the twin-arginine motif cut-site, followed by a W-motif and often a C-terminal motif.

Impact of chirality on the amorphous state of conglomerate forming systems: a case study of N-acetyl-α-methylbenzylamine.

The present work aims at addressing the issue of molecular handedness in glassy and liquid states and its impact on heterogeneous equilibrium. For this purpose, we evaluated the glass forming ability (GFA), crystallization propensity, molecular mobility and hydrogen bonding structure of a chiral conglomerate forming system, N-acetyl-α-methylbenzylamine (Nac-MBA), at various enantiomeric excesses (ees) using experimental and computational techniques. We revealed that the rich relaxational landscape (Debye (D), α, βJG and ϒ) and the temperature dependence of the time scale of each process were insensitive to chirality. The most remarkable impact of chirality was expressed on the GFA and the recrystallization of heterochiral arrangements. In fact the GFA increases with decreasing ee, while the crystallization propensity increases with increasing ee. The counter enantiomer acted as a disruptor of crystallization and favored the glass formation upon cooling. The molecular dynamics simulation (MDS) results on the architecture of chiral sequences showed that homochiral sequences were more favorable when compared to heterochiral ones in the liquid state. However, this predisposition to form homochiral sequences in the liquid state was not the precursor of the future crystalline structure, since the liquid or the glassy system recrystallizes as heterochiral sequences. As per our understanding the crystallization was mostly controlled by the mean free migration path of an enantiomer to build homochiral or heterochiral sequences. In the present case, it seems that the mean free migration path achieved by an enantiomer for heterochiral sequences is shorter compared to homochiral arrangements in such a way that the crystallization of the metastable racemic compound is kinetically more favorable.

The Mosaic Architecture of NRPS-PKS in the Arbuscular Mycorrhizal Fungus Gigaspora margarita Shows a Domain With Bacterial Signature

As obligate biotrophic symbionts, arbuscular mycorrhizal fungi (AMF) live in association with most land plants. Among them, Gigaspora margarita has been deeply investigated because of its peculiar features, i.e., the presence of an intracellular microbiota with endobacteria and viruses. The genome sequencing of this fungus revealed the presence of some hybrid non-ribosomal peptide synthases-polyketide synthases (NRPS-PKS) that have been rarely identified in AMF. The aim of this study is to describe the architecture of these NRPS-PKS sequences and to understand whether they are present in other fungal taxa related to G. margarita. A phylogenetic analysis shows that the ketoacyl synthase (KS) domain of one G. margarita NRPS-PKS clusters with prokaryotic sequences. Since horizontal gene transfer (HGT) has often been advocated as a relevant evolutionary mechanism for the spread of secondary metabolite genes, we hypothesized that a similar event could have interested the KS domain of the PKS module. The bacterial endosymbiont of G. margarita, Candidatus Glomeribacter gigasporarum (CaGg), was the first candidate as a donor, since it possesses a large biosynthetic cluster involving an NRPS-PKS. However, bioinformatics analyses do not confirm the hypothesis of a direct HGT from the endobacterium to the fungal host: indeed, endobacterial and fungal sequences show a different evolution and potentially different donors. Lastly, by amplifying a NRPS-PKS conserved fragment and mining the sequenced AMF genomes, we demonstrate that, irrespective of the presence of CaGg, G. margarita, and some other related Gigasporaceae possess such a sequence.

Learning and interpreting the gene regulatory grammar in a deep learning framework.

Deep neural networks (DNNs) have achieved state-of-the-art performance in identifying gene regulatory sequences, but they have provided limited insight into the biology of regulatory elements due to the difficulty of interpreting the complex features they learn. Several models of how combinatorial binding of transcription factors, i.e. the regulatory grammar, drives enhancer activity have been proposed, ranging from the flexible TF billboard model to the stringent enhanceosome model. However, there is limited knowledge of the prevalence of these (or other) sequence architectures across enhancers. Here we perform several hypothesis-driven analyses to explore the ability of DNNs to learn the regulatory grammar of enhancers. We created synthetic datasets based on existing hypotheses about combinatorial transcription factor binding site (TFBS) patterns, including homotypic clusters, heterotypic clusters, and enhanceosomes, from real TF binding motifs from diverse TF families. We then trained deep residual neural networks (ResNets) to model the sequences under a range of scenarios that reflect real-world multi-label regulatory sequence prediction tasks. We developed a gradient-based unsupervised clustering method to extract the patterns learned by the ResNet models. We demonstrated that simulated regulatory grammars are best learned in the penultimate layer of the ResNets, and the proposed method can accurately retrieve the regulatory grammar even when there is heterogeneity in the enhancer categories and a large fraction of TFBS outside of the regulatory grammar. However, we also identify common scenarios where ResNets fail to learn simulated regulatory grammars. Finally, we applied the proposed method to mouse developmental enhancers and were able to identify the components of a known heterotypic TF cluster. Our results provide a framework for interpreting the regulatory rules learned by ResNets, and they demonstrate that the ability and efficiency of ResNets in learning the regulatory grammar depends on the nature of the prediction task.

Effector prediction and characterization in the oomycete pathogen Bremia lactucae reveal host-recognized WY domain proteins that lack the canonical RXLR motif.

Pathogens that infect plants and animals use a diverse arsenal of effector proteins to suppress the host immune system and promote infection. Identification of effectors in pathogen genomes is foundational to understanding mechanisms of pathogenesis, for monitoring field pathogen populations, and for breeding disease resistance. We identified candidate effectors from the lettuce downy mildew pathogen Bremia lactucae by searching the predicted proteome for the WY domain, a structural fold found in effectors that has been implicated in immune suppression as well as effector recognition by host resistance proteins. We predicted 55 WY domain containing proteins in the genome of B. lactucae and found substantial variation in both sequence and domain architecture. These candidate effectors exhibit several characteristics of pathogen effectors, including an N-terminal signal peptide, lineage specificity, and expression during infection. Unexpectedly, only a minority of B. lactucae WY effectors contain the canonical N-terminal RXLR motif, which is a conserved feature in the majority of cytoplasmic effectors reported in Phytophthora spp. Functional analysis of 21 effectors containing WY domains revealed 11 that elicited cell death on wild accessions and domesticated lettuce lines containing resistance genes, indicative of recognition of these effectors by the host immune system. Only two of the 11 recognized effectors contained the canonical RXLR motif, suggesting that there has been an evolutionary divergence in sequence motifs between genera; this has major consequences for robust effector prediction in oomycete pathogens.

Sequence biostratigraphic framework for the Oligocene to Pliocene of Malaysia: High-frequency depositional cycles driven by polar glaciation

This paper reviews quantitative biostratigraphic data from 101 petroleum exploration wells from the Malay, Sarawak and Sabah basins, and places the stratigraphy of each area into a precise chronostratigraphic framework comprising 41 transgressive-regressive depositional packages which are fully defined here. Each package is ‘fingerprinted’ by foraminiferal, nannofossil and palynological index fossils, and then tied to the global pattern of glacio-eustatic sea level and climate changes based on the global δ18O and δ13C datasets used to calibrate the geological timescale. The result is a tightly constrained chronostratigraphic framework that is applicable from deep to shallow water and is of high accuracy. It is concluded that there is a sedimentation ‘pulsebeat’ across Southeast Asia, independent of local and regional tectonics, driven by patterns of global climate change. For the Oligocene and Miocene, Antarctic glaciation is the key driver, whereas the Pliocene cycles are mainly driven by the expansion and contraction of Northern Hemisphere glaciers. The new chronostratigraphic framework allows unconformities across Malaysia to be better characterised, and the different classification schemes of seismic “Groups” in Malay and Penyu basins, “Cycles” in offshore Sarawak and “Stages” in offshore western Sabah to be correlated. Also, with a clear understanding of the effect of fluctuating sea levels on the stratigraphy of the region, it is easier to make firm judgments regarding the effect of tectonics. The study also characterises systems tracts from shelf to basin floor using biostatigraphic assemblages, which should help in ground-truthing the architecture of depositional sequences in the region based on seismic. The new framework is proposed as an alternative to the outdated TB scheme of Haq et al. (1988), widely used to interpret depositional cycles across Sarawak and Sabah.

Late Ordovician climate and sea-level record in a mixed carbonate-siliciclastic-evaporite lithofacies, Williston Basin, USA

The Late Ordovician late Katian was a period of generally warm, transitional greenhouse to icehouse climate with sea-level oscillations dominated by moderate-amplitude eustasy. This study aims to improve the understanding of the climatic and sea-level fluctuations prior to the end-Ordovician glaciation, using a comprehensive core, wireline log, and thin-section dataset spanning the topmost Red River-Stony Mountain Formation within the subsurface of North Dakota, Williston Basin, North America. Eleven facies are identified, interpreted, and grouped into four facies associations, including salina to peritidal evaporative, restricted-marine subtidal, open-marine subtidal, and open-marine deeper water. Stratigraphic trends, basin-wide facies variations, and correlation of individual surfaces for ~380 km across the study area, suggest that the facies were deposited under different climatic and sea-level regimes as part of the long-term Stony Mountain sequence. The sequence (37–52 m) is bounded by anhydrites (basin center) and their correlative thin exposure-related breccias (updip proximal basin), and contains a set of high-frequency sequences (HFS; 2–26 m) that can be traced across the study area. The lowstand systems tract (LST) anhydrites formed in a shallow and well‑oxygenated setting under an arid climate during relatively short periods of the basin restriction. The sea-level rise during the early transgressive system tract (TST) resulted in a higher evapotranspiration rate and an increasingly humid climate that peaked during the late TST with the input of siliciclastics off the Transcontinental Arch. The increased precipitation and runoff resulted in quasiestuarine circulation. Return to semi-arid conditions characterizes the highstand systems tract (HST), with increasingly more restricted, shallow-marine and oxygenated setting with antiestuarine circulation. The work provides insight into the interaction of siliciclastic input, climate, and sea-level changes on depositional dynamics and sequence architecture of a mixed carbonate-siliciclastic-evaporite succession that formed in a tropical epicontinental basin setting prior to the end-Ordovician glaciation.

Along-strike Quaternary morphological variation of the Baiyun Sag, South China Sea: The interplay between deltas, pre-existing morphology, and oceanographic processes

Continental margins usually display along-strike morphological variation, with diverse underlying controls around the world. Based on 3D seismic data from the Baiyun Sag, northern South China Sea, this work provides a new case study to understand the combined controls on along-strike morphological variation over short strike distances. The northern slope of the Baiyun sag was characterized by a gently dipping ramp at the beginning of the Quaternary, and the Quaternary along-strike morphological variation in this area is mainly displayed in the deltas, submarine canyons and contourite depositional system. The deltas were featured by lobate form and mainly distributed at the western area, with shoreline parallel and oblique to the ramp strike in the west and east, respectively. The scales of the deltas and the associated submarine canyons decreased towards the east. The eastern plastered contourite drifts have a greater areal extent than those in the west, and the former are terraced. The Quaternary slope evolution took place in three stages (stage 1–3), of which the time intervals are ca. 2.6 - ca. 1.6 Ma, ca. 1.6 - ca. 0.14 Ma and ca. 0.14–0 Ma, respectively. The slope was characterized by a gentle ramp, deltas and contourites from stage 1–3 respectively.The along-strike morphological variation of the northern slope of the Baiyun Sag was predominantly influenced by the interplays between the deltas, pre-existing morphology, and oceanographic regimes. The localization of the lobate-form deltas with respect to the pre-existing submarine canyons on the ramp exerted a great influence on the along-strike variation of these canyons within stage 2. The interplay between the delta morphology (i.e., delta position and delta-front gradients) and the oceanographic regimes (i.e. contour currents and internal waves) controlled the along-strike variation in contourite processes during the stage 3. This study provides a new insight into the combination of controls responsible for along-strike morphological variation of post-rift continental margins evolving from a ramp. The underlying depositional processes revealed by this study would be helpful for understanding the lateral variability of sequence architectures and the deep-water sands deposition, which are important basis for guiding future deep-water hydrocarbon exploration on such continental margins elsewhere.

Sequence stratigraphy of a Middle to Upper Ordovician foreland succession (Ottawa Embayment, central Canada): Evidence for tectonic control on sequence architecture along southern Laurentia

AbstractThe Middle to Upper Ordovician foreland succession of the Ottawa Embayment in central Canada is divided into nine transgressive‐regressive sequences that defines net deepening of a platform succession over ~15 m.y. from peritidal to outer ramp settings, then a return to peritidal conditions over ~3 m.y. related to basin filling by orogen‐derived siliciclastics. With a backdrop of net eustatic rise through the Middle to Late Ordovician, there are several different expressions of structural influence on sequence development in the embayment. During the Middle Ordovician (Darriwilian), foreland‐basin initiation was marked by regional onlap with abundant synsedimentary deformation across a faulted trailing‐margin platform interior; subsequent craton‐interior uplift resulted in voluminous influx of siliciclastics contemporary with local structurally influenced local channelization; then, a formation of a platform‐interior shale basin defines continued intrabasin tectonism. During the Late Ordovician (Sandbian, early Katian), structural influence was superimposed on sea‐level rise as indicated by renewed local development of a platform‐interior shale basin; differential subsidence and thickness variation of platform carbonate successions; abrupt deepening across shallow‐water shoal facies; and, micrograben development coincident with foreland‐platform drowning. These stratigraphic patterns are far‐field expressions of distal orogen development amplified in the platform interior through basement reactivation along an inherited buried Precambrian fault system. Comparison of Upper Ordovician (Sandbian‐lower Katian) sequence stratigraphy in the Ottawa Embayment with eustatic frameworks defined for the Appalachian Basin reveals greater regional variation associated with Sandbian sequences compared to regional commonality in base level through the early Katian.

Forecast network-wide traffic states for multiple steps ahead: A deep learning approach considering dynamic non-local spatial correlation and non-stationary temporal dependency

Obtaining accurate information about future traffic flows of all links in a traffic network is of great importance for traffic management and control applications. This research studies two particular problems in traffic forecasting: (1) capture the dynamic and non-local spatial correlation between traffic links and (2) model the dynamics of temporal dependency for accurate multiple steps ahead predictions. To address these issues, we propose a deep learning framework named Spatial-Temporal Sequence to Sequence model (STSeq2Seq). This model builds on sequence to sequence (seq2seq) architecture to capture temporal feature and relies on graph convolution for aggregating spatial information. Moreover, STSeq2Seq defines and constructs Pattern-aware Adjacency Matrix (PAM) based on pair-wise similarity of the recent traffic patterns on traffic links and integrates it into graph convolution operation. It also deploys a novel seq2sesq architecture which couples a convolutional encoder and a recurrent decoder with attention mechanism for dynamic modeling of long-range dependence between different time steps. We conduct extensive experiments using two publicly-available large-scale traffic datasets and compare STSeq2Seq with other baseline models. The numerical results demonstrate that the proposed model achieves state-of-the-art forecasting performance in terms of various error measures. The ablation study verifies the effectiveness of PAMs in capturing dynamic non-local spatial correlation and the superiority of proposed seq2seq architecture in modeling non-stationary temporal dependency for multiple steps ahead prediction. Furthermore, qualitative analysis is conducted on PAMs as well as the attention weights for model interpretation.

Sequence stratigraphy in post‐rift river‐dominated lacustrine delta deposits: A case study from the Upper Cretaceous Qingshankou Formation, northern Songliao Basin, northeastern China

The Upper Cretaceous Qingshankou Formation in the northern Songliao Basin was deposited in river‐dominated lacustrine delta systems. Three third‐order sequences and two types of sequence architecture were recognized using core observations, logging curve interpretations, and three‐dimensional (3‐D) seismic profiles in Qingshankou Formation. One type of sequence architecture was developed in a syndepositional flexural slope break, and the other was deposited on a gentle slope. The studied sequences were deposited in a high accommodation setting, which was due to the large rate of subsidence of the basin basement, and a tropical to semi‐tropical and a humid to semi‐humid climate. The episodic tectonic/thermal subsidence of the basin controlled the development of the sequence architecture. Turbidite bodies within transgressive systems tracts and early highstand systems tracts were deposited predominantly in the basinward part of the syndepositional flexural slope breaks, and they were favourable exploration targets, particularly for stratigraphic traps.