Lower Member Research Articles

Late Neoproterozoic tectonic evolution of the northern Tarim block: New insights from integrated detrital zircon and rutile geochronology and trace element geochemistry

In the Neoproterozoic era, the breakup of the Rodinia supercontinent had a profound impact on different aspects of Earth; yet, the precise driving mechanism behind this event has been a source of ongoing controversy. The Tarim block, as a crucial component, presents an opportunity to gain valuable insights into the breakup process through its tectonic-sedimentary evolution history and dynamic background. However, the comprehension of basin evolution is limited due to the presence of an ambiguous prototype basin during the late Neoproterozoic and its intricate interconnections with surrounding blocks. In this contribution, we integrate detailed field observations, U-Pb dating of detrital zircon and rutile, and trace element analysis of detrital rutile to elucidate the source-to-sink relationships and the tectonic setting of Ediacaran sedimentary strata in the Aksu area (northern Tarim block, China). Detrital zircon age spectra exhibit consistent distributions with ages between ∼850 and ∼600 Ma and between ∼2100 and ∼1800 Ma. Rutile age groups however exhibit an abrupt transition between the lower member of the Sugatbrak Formation and the succeeding upper member to the Qigebrak Formation in the basin, with ages between ∼1800 and ∼900 Ma and nearly identical to those between ∼2100 and ∼1800 Ma. Calculated Zr-in-rutile temperatures and Cr-Nb compositions imply that the majority of the detrital rutiles were sourced from amphibolite facies metapelites, with an abrupt transition from amphibolitic schist to amphibolite-granulite facies for the ∼1800 Ma group grains. Provenance tracing shows that the detrital sediments of the lower Sugatbrak Formation are sourced from both the Central Tianshan and the Tarim blocks, and that the overlying strata have a single source in the Tarim block. A corresponding change from syn-rift detrital facies to a shallow-marine environment in on a passive continental margin is suggested in terms of depositional setting. In light of prior published evidence from petrology, geochronology and paleomagnetism, we propose that the Neoproterozoic northern Tarim margin was affected by a protracted subduction zone retreat. Associated back-arc spreading eventually was responsible for the opening of the southern Tianshan Ocean and rifting of the Central Tianshan block from the Tarim block in the late Ediacaran. This development ultimately prevented detrital material from the Central Tianshan block from reaching the northern Tarim depocenters as the latter evolved into a passive continental margin.

A new early-diverging probainognathian cynodont and a revision of the occurrence of cf. Aleodon from the Chañares Formation, northwestern Argentina: New clues on the faunistic composition of the latest Middle-?earliest Late Triassic Tarjadia Assemblage Zone.

The Chañares Formation (Ischigualasto-Villa Unión Basin) is worldwide known by its exquisitely preserved fossil record of latest Middle-to-early Late Triassic tetrapods, including erpetosuchids, "rauisuchians," proterochampsids, gracilisuchids, dinosauromorphs, pterosauromorphs, kannemeyeriiform dicynodonts, and traversodontid, chiniquodontid and probainognathid cynodonts, coming from the Tarjadia (bottom) and Massetognathus-Chanaresuchus (top) Assemblage Zones of its lower member. Regarding cynodonts, most of its profuse knowledge comes from the traditional layers discovered by Alfred Romer and his team in the 1960s that are now enclosed in the Massetognathus-Chanaresuchus Assemblage Zone (AZ). In this contribution we focus our study on the probainognathian cynodonts discovered in levels of the Tarjadia Assemblage Zone. We describe a new chiniquodontid cynodont with transversely broad postcanine teeth (Riojanodon nenoi gen. et sp. nov.) which is related to the genus Aleodon. In addition, the specimen CRILAR-Pv 567 previously referred to cf. Aleodon is here described, compared, and included in a phylogenetic analysis. It is considered as an indeterminate Aleodontinae nov., a clade here proposed to included chiniquodontids with transversely broad upper and lower postcanines, by having a cuspidated sectorial labial margin and a lingual platform that is twice broader than a lingual cingulum. Cromptodon mamiferoides, from the Cerro de Las Cabras Formation (Cuyo Basin), was also included in the phylogenetic analysis and recovered as an Aleodontinae. The new cynodont and the record of Aleodontinae indet. reinforce the faunal differentiation between the Tarjadia and Massetognathus-Chanaresuchus Assemblage Zones, in the lower member of the Chañares Formation, and inform on the diverse chiniquodontid clade with both sectorial and transversely broad postcanine teeth.

Timing of India-Asia suturing: Evidence from a remnant peripheral foreland basin in Xigaze, South Tibet

The absence of a fully preserved foreland basin system in the central-eastern Yarlung-Zangpo Suture Zone (YZSZ) of Tibet has hindered the understanding of the initial timing of the India-Asia collision along strike. To address this issue, remnant foredeep and wedge-top deposits of the foreland basin system are described from the Tethyan Himalaya sequence and the YZSZ in the Xigaze area. The foredeep is defined by the olistostrome of the Zongzhuo Formation, which consists of matrix and blocks, including chert, limestone, sandstone and volcanic rocks. Based on the matrix properties, the Zongzhuo Formation is divided into two units: a lower member (Zhilong unit) with a matrix composed of black shale and thin layers of siltstone and an upper member (Yongla unit) with a matrix composed of distinctly red shale or yellow-green siliceous mudstone with interbedded siltstone and limestone. The Zongzhuo Formation is dated to 65–57 Ma by detrital zircon U - Pb chronology and radiolarian assemblages. In the YZSZ, the Puxia and Jiabi units are interpreted as wedge-top deposits consisting of mudstone matrix and exotic blocks, such as sandstone, chert and limestone. The maximum depositional ages (MDAs) of the sandstone blocks from both units are ca. 65–59 Ma. Detrital zircon provenance analysis and trace element data exclude an intraoceanic arc origin and point to a source from the Gangdese arc and recycled accretionary wedge in the suture zone. Therefore, we propose that the initial collision between India and Asia occurred at 65 Ma in the central-eastern YZSZ.

The Middle Miocene Microfacies, Cyclicity, and Depositional History: Implications on the Marmarica Formation at the Siwa Oasis, Western Desert (Egypt)

Microfacies studies were carried out on the Middle Miocene Marmarica Formation exposed at the Gabal Western Bahi El-Din and Gabal El-Najdeen, the Siwa Oasis, northwestern Desert (Egypt). It was distinguished into the lower, middle, and upper members. Eleven microfacies types were recognized, which include skeletal lime-mudstone, dolomitic lime-mudstone, intraclastic wackestone, bryozoan wackestone, foraminiferal wackestone, foraminiferal bryozoan packstone, glauconitic molluscan packstone, molluscan intraclastic packstone, pelletal peloidal skeletal packstone, dolostones, and claystone microfacies. This formation includes several types of emergence- meter-scale cycles (shallowing-upward). Field observations and petrographic analyses revealed that these cycles consist of pure carbonates and mixed siliciclastic carbonates. These cycles consist of four types of gradual cycles and six types of non-gradual cycles. The gradual emergence cycles indicate a balance between the rate of subsidence, sea level oscillations, and sedimentation rate. The non-gradual cycles indicate an irregular balance between sedimentation rate and subsidence rate. The non-gradual cycles denote high-frequency sea level variation and/or short-term sea level oscillations, which are associated with high carbonate formation. The depositional environments of the Marmarica Formation are restricted to lagoonal at the base, followed upward to open marine conditions. Both environments most probably characterize the platform setting.

Characteristics and origin of crystalline dolomite: A case from Paleogene lacustrine fine-grained rocks in Jiyang depression, Bohai Bay Basin, China

Crystalline dolomite is a common carbonate mineral in lacustrine fine-grained rocks, but it has a confusing origin that has been a focus of much debate in recent years. In our research, the fine-grained rocks rich in crystalline dolomite were sampled from the upper fourth member (UMbr 4) and lower third member (LMbr 3) of the Shahejie Formation in the Jiyang Depression, and analyzed by a variety of analytical techniques, including field emission scanning electron microscopy (FESEM), cathodoluminescence (CL), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), micro-area carbon, oxygen, strontium isotopes and electron probe analyses. The results show: ①The crystalline dolomites in the lacustrine fine-grained rocks are primarily composed of ferroan-poor dolomite (FeO < 1%), type I ferroan dolomite (FeO ≈ 5%) and type II ferroan dolomite (FeO ≈ 16%); ②The δ18O of ferroan-poor dolomites in mudstone is between −0.89 and 0.32‰, the precipitation temperature is less than 60 °C, and their formation is related to the microbial action during the early diagenetic stage A, while the ferroan-poor dolomites in dolostone are primarily formed by the recrystallization of micritic dolomite; ③The δ18O of type I ferroan dolomites ranges from −3.74 to −3.89‰, the precipitation temperature ranges from 68.4 to 69.4 °C, and they are primarily formed by the microbial action and clay mineral transformation during the early diagenetic stage B; ④The δ18O of type II ferroan dolomites is between −7.78 and −8.33‰, the precipitation temperature is more than 90 °C, and their formation is related to the dissolution of early carbonate and clay mineral transformation during the middle diagenetic stage; ⑤The origin mechanism of crystalline dolomite indicates the diagenetic evolution of fine-grained rocks and the migration path and storage of shale oil.

Study on the Differential Distribution Patterns of Fine-Grained Sedimentary Rocks in the Lower Third Member of the Shahejie Formation in Zhanhua Sag, Bohai Bay Basin

Due to the diverse types of sedimentary source supply systems, the research on the distribution patterns of fine-grained sedimentary rocks in rifted lake basins is relatively underdeveloped. The authors of this article selected the lower third member of the Shahejie Formation (Es3L) in Zhanhua Sag as a research object. Using rock core, thin section, and other data, we analyzed rock types and genesis mechanisms, identified the spatiotemporal distribution patterns of facies within the sag, and established a fine-grained depositional model for the rifted lake basin. Five lithofacies were identified, revealing the differential distribution patterns of fine-grained sedimentary rocks in the region. The northern steep slope zone and the deep depression zone are characterized by the deposition of gravity flow-formed terrestrial layered-pebbly mudstone and gravity flow-formed mixed-source pebbly mudstone, respectively. In the central lake basin zone, mixed-source laminated mudstone with vertical rhythmic interlayers has developed. In the southern gentle slope zone, biologically cemented endogenic irregularly bedded algal limestone and chemically precipitated endogenic laminated limestone have developed. The characteristics of strong northern and weak southern terrestrial inputs in the study area control the differential distribution of lithofacies, and based on this, a fine-grained rock depositional model for the rifted lake basin was established.

The type-section of the Gutenstein Formation at Gutenstein revisited (Anisian, Northern Calcareous Alps, Lower Austria): Lithostratigraphy, biostratigraphy and regional overview

Abstract New biostratigraphic data derived from the stratotype of the Gutenstein Formation at the village Gutenstein (Lower Austria) help to solve some long-standing problems about the stratigraphy of the Anisian stage within the eastern part of the Northern Calcareous Alps. At Gutenstein, the lower lithostratigraphic boundary of the Anisian Gutenstein Formation to the underlying lower Anisian Reichenhall Formation is defined, assuming a normal stratigraphic contact of the Reichenhall Formation to the underlying Werfen Formation and to the overlying Gutenstein Formation. Microfacial data confirm the sedimentary origin of the rauwackes of the Reichenhall Formation. A detailed lithostratigraphic and facies-oriented definition of the Gutenstein Formation includes prevailing thin and planar-bedded, black colored, sometimes fine-bedded limestone (rarely dolostone) and radiolarian (calcispheres) bearing, black colored mud- to wackestone, mostly containing some fine crinoid debris. Upsection, a quick change to an upper (Pelsonian) member of the Gutenstein Formation with nodular bedding planes and brachiopod-, crinoid-, conodont- and ammonite accumulations is presented. The general depositional environment of the Gutenstein Formation is interpreted as a dysoxic outer carbonate ramp deposit, with a shallowing upward trend to rather thick-bedded mid- and inner carbonate ramp settings of the Annaberg- and Steinalm formations. The approximate interval of the Anisian/Ladinian boundary within the type-section of Gutenstein is determined with help of new fossil findings such as dasycladalean green-algae. Based on distinct lithological differences on a regional scale, which occur in thick basinal stratigraphic successions within the Gutenstein Formation like at Großreifling (Styria, Bajuvaric Nappe System), at Innerfahrafeld (elevation Fuchsriegel, Lower Austria) and on mount Kasberg at Grünau (Upper Austria, Tirolic Nappe System), a subdivision of the Gutenstein Formation into a lower Gutenstein Member, and an upper Kasberg Member (= Upper Gutenstein Formation), is proposed herein. The lower member corresponds to the black, thin- and planar-bedded interval, whereas the Kasberg Member is characterized by nodular bedding planes, greater bed thicknesses and higher fossil content.

Facies characterisation and stratigraphy of the upper Maastrichtian to lower Danian Maastricht Formation, South Limburg, the Netherlands

Abstract The Maastricht Formation is a mostly calcarenitic unit that belongs to the Chalk Group but is unlike the typical North Sea chalk in that it is much coarser and at times contains a significant terrigenous component. The formation was deposited between the late Maastrichtian and the early Danian in a proximal zone of the Chalk Sea immediately north of the Anglo-Brabant and Rhenish massifs. The formation crops out in South Limburg, the Netherlands, in the German state of North Rhine–Westphalia, near Aix-la-Chapelle (Aachen), and in the Belgian provinces of Liège and Limburg, and it is present in the subsurface in the Campine Basin and in the Roer Valley Graben, in Belgium and the Netherlands. The often spectacular fossil content of the Maastricht Formation has been extensively studied but its sedimentological aspects remain understudied. Indeed, the lithostratigraphy of the formation is largely informal and based on the abundance and morphology of flint and on the quantification of fossil content. The paucity of facies studies and the lack of a lithostratigraphic framework based on modern facies studies hampers stratigraphic correlation between outcrops and, more importantly, boreholes. A facies characterisation and facies-based lithostratigraphic framework of the Maastricht Formation in South Limburg is particularly urgent because groundwater is abstracted from aquifers in the formation and geological models currently in place fail to predict facies heterogeneity and, consequently, aquifer properties. We studied eight outcrops of the Maastricht Formation across South Limburg and carried out a (micro)facies analysis of the outcrops. We show that the Maastricht Formation can be subdivided into three lithofacies and five microfacies. The lithofacies reflect the traditional subdivision of the formation into Maastricht and Kunrade limestones. Our results suggest that the current subdivision of the Maastricht Formation into six members is untenable. The formation is best subdivided into lower and upper members. The Kunrade limestone should be afforded the status of formation. We interpret the Maastricht Formation as having been deposited in an epeiric ramp, in which facies distribution was controlled by water temperature, nutrient levels and storminess. The (micro)facies of the Maastricht Formation can be organised into two depositional stages: stage 1, representing the lower part of the formation, is characterised by heterozoan carbonates deposited under cooler, mesotrophic conditions in a nutrient-rich, more proximal region of the epeiric sea; stage 2 is characterised by heterozoan-photozoan carbonates deposited in a warmer and stormier environment with slightly lower nutrient levels.

Isimila Prehistoric Site, Tanzania: Comparative Faunal Datings and ESR, with a Reassessment

More than sixty years ago, 1957-58 University of Chicago excavations at the Isimila Prehistoric Site in the Southern Highlands of Tanzania exposed a sequence of Pleistocene deposits that included Earlier Stone Age aggregates. Now, the available correlations with extinct fauna from other dated East African localities and preliminary electron spin resonance (ESR) estimates indicate that the Isimila Formation was deposited over a much longer time range than originally proposed. As originally noted, Earlier Stone Age ‘large cutting tools' or LCT's found in the upper Lisalamagasi Member are more refined than are those found in the Sands units of the lower Lukingi Member. This suggests a correlation with Kalambo Falls Prehistoric Site for the upper member, with new OSL dating at ca. 400–500 ka. The new faunal correlations and ESR estimates indicate that the lower member was deposited between 500 and 900 ka, during the later Early Pleistocene to the early Middle Pleistocene. A reassessment of Isimila including unpublished excavation data raises questions about the Pleistocene human occupations and their palaeoenvironments on the Highlands Plateau.

Paleoenvironmental evolution and organic matter accumulation of the lower Cambrian Maidiping marine black shales in the intracratonic basin, western margin of Sichuan Basin, South China

ABSTRACT The Late Ediacaran to Early Cambrian marked a pivotal phase in paleoenvironmental and tectonic shifts. The Sichuan Basin, on the Yangtze platform’s western edge, developed the Mianyang-Changning intracratonic sag due to Xingkai taphrogenesis. The Maidiping Formation’s black shales, the initial fine-grained clastic deposits from the Early Cambrian, span the Sichuan Basin’s western margin. The influence of the intracratonic sag on organic matter accumulation and paleo-marine environment evolution remains unclear. Comprehensive petrological and geochemical analyses on the Qingping section revealed three distinct members within the Maidiping Formation: black shales and silicified dolomite with shales in a restricted basin (lower member), deep-water black shales (middle member), and phosphoritic turbidite sandstone with siliceous phosphorites (upper member). The lower member’s organic accumulation arose from restricted ocean circulation, leading to stratified waters and reduced oxygen at depth. The middle member’s organic build-up was influenced by enhanced intracratonic sag connectivity with the open ocean, sea-level rise, and increased productivity. The submarine hydrothermal activity might have induced anoxic conditions. The upper member saw a decline in organic matter due to phosphoritic debris and oxygenation. The Maidiping Formation augments the Lower Cambrian source rock, vital for oil and gas exploration in the Sichuan Basin’s western margin.

Diagenetic evolution of tight sandstone and the formation of an effective reservoir in the lower member 3 of the Shahejie Formation, Bohai Bay Basin, East China

Heterogeneity in the physical properties of tight sandstones is mainly caused by complex diagenetic interactions in various combinations during the burial process. The tight sandstone oil in the Linnan Sag of Bohai Bay Basin has great development potential but it is unclear how effective reservoirs were formed, and this is a significant reason why exploration in the deep reservoir is so difficult. Here we studied the diagenetic evolution of the tight sandstone of Lower Member 3 of the Shahejie Formation, Linnan Sag, Bohai Bay Basin, by using cores, thin sections, XRD, SEM, grain-size analysis, high-pressure mercury intrusion porosimetry, fluid inclusions, and carbon and oxygen stable isotopes. Compaction, replacement, cementation and dissolution diagenesis are identified; all four processes mainly occur in the A phase of mesodiagenesis. The interaction of formation burial, thermal evolution of organic matter and dehydration of gypsum leads to the alternating presence of three stages of alkaline fluids and two stages of acidic fluids. The average dissolution porosity of the dissolution sandstone facies is greater than the lower limit of the porosity for the effective reservoir in the study area, which is key to the formation of effective reservoirs. By determining differential diagenetic evolution sequences of tight sandstone reservoirs under the constraints of different lithologies where sandstone is interbedded with mudstone, we are able to elucidate the formation of the effective reservoir as follows: (1) In the eodiagenetic stage, a large amount of early carbonate cement developed in the sandstone adjacent to the mudstone, filling the primary pores and forming a cementation sandstone facies. Smaller amounts of early carbonate cement developed in the interior of the sandstone, which “fixed” the primary pores, and has a positive effect on the formation of a large number of secondary pores in the dissolution stage. (2) In the early stage of mesodiagenesis (A1), due to the filling of primary pores, it is difficult for acidic fluids to enter the cementation sandstone facies adjacent to mudstone, and the dissolution is weak. But dissolution within the sand body was strong, producing a large number of dissolution pores and forming a dissolution sandstone facies that clearly enhanced the physical properties. (3) In a second early stage of mesodiagenesis (A2), dissolution still played a dominant role in the dissolution sandstone facies, due to the development of dissolution pores in the previous stage (it is easy for acidic fluids to enter the dissolution sandstone facies). The physical properties of the dissolution sandstone facies were once again enhanced and an effective reservoir gradually began to form. (4) At the end of mesodiagenesis stages A1 and A2 (26.2–24.6 Ma; 7.5–2.8 Ma), the reservoir experienced two phases of petroleum charging. The charging of the cementation sandstone facies developed at the margins of the sandstones was difficult due to the filling of primary pores. The dissolution sandstone facies are oil-bearing, with higher porosity, which indicates an effective reservoir. By coupling the thermal evolution of organic matter and the dehydration of gypsum with differential diagenetic evolution and the porosity evolution of reservoir, we are able to establish a reservoir genetic model that involves alternating seepage of organic acids and alkaline brines.

Organic petrology and geochemistry of the Devonian-Mississippian bakken formation, Williston Basin, North Dakota

The Devonian–Mississippian (D–M) black shales of the Bakken Formation are of interest as a hydrocarbon source due to their high total organic carbon (TOC; 2.2–17.4%) content. The Upper and Lower Members of the Bakken Fm. are shallow marine (100–150 m) sequences. Thirty samples were selected for maceral identification, kerogen typing, and solid bitumen reflectance (SBRo) based on TOC content and down-core spacing. The shales contain alginite, bituminite, abundant solid bitumen (SB), and minor amounts of inertinite. Solid bitumen increases in quantity with increasing thermal maturity. Pyrolysis (85 samples) provided S1 (avg. 8.0 mg HC/g rock), S2 (avg. 24.3 mg HC/g rock), hydrogen index (HI; avg. 201 mg HC/g TOC), oxygen index (OI; avg. 7 mg CO2/g TOC), and Ro (0.60–1.03%) calculated from Tmax. Plots of HI vs. OI and HI vs. Tmax (°C) were used to assess kerogen type but are not consistently in agreement with the petrographic assessment. Some samples from more thermally mature cores plot as Type III (vitrinite) kerogen instead of Type II (alginite and bituminite) kerogen, the latter confirmed through petrographic observations of lower maturation samples. This is largely due to increased SB in more thermally mature samples (Ro = 0.83–1.03%), as SB is known to have a lower HI content than Type II kerogen. Petrographic data show more alginite and bituminite (19–55%) in the thermally less mature samples (Ro = 0.60–0.83%) compared to more dispersed SB (67–86%) and less alginite and bituminite (<1%) in the more thermally mature samples (Ro = 0.89–1.01%).Early research on the Bakken Fm. reported lower than expected vitrinite reflectance values and attributed them to vitrinite “suppression”. The scarcity of vitrinite and abundance of SB suggest that early work likely reported reflectance on SB. Recent attempts to assess the thermal maturity of the Bakken black shales have converted SBRo to vitrinite reflectance equivalence (VRE). However, there are multiple SB populations present in these shales and it is not always clear which SB populations were included, possibly contributing to error. In the current study, only smooth, homogenous SB was measured (0.68–1.14% SBRo) and VRE values calculated (0.54–1.49%) to assess thermal maturity from the basin margin to the depocenter; inclusion of measurements on granular, heterogeneous SB (14–21 vol%), which are ~53% lower than those for smooth, homogenous SB (3–12 vol%), results in lower mean reflectances, especially in more mature samples. Vitrinite reflectance equivalent data calculated using the D–M New Albany Shale equation of Liu et al. (2019) agrees with liptinite fluorescence and Rock-Eval Ro, whereas VRE based on the D–M Woodford Shale equation of Cardott and Comer (2021) does not. This suggests the importance of applying VRE equations from similar formations both in terms of thermal history, as well as kerogen type and age. Results from SBRo, Rock-Eval Ro, VRE, and observations of alginite fluorescence indicate that samples from the current study range from the early oil window into the condensate, wet gas zone.

Timeframe of eastern Paleo-Tethys closure: Constraint on the Songpan-Ganzi Complex by big data-based multiproxy provenance analysis

The Songpan-Ganzi Complex (SGC) is one of the largest turbidite complexes on Earth. The source-to-sink processes of the SGC are closely linked to the closure of the Paleo-Jinsha Ocean in the eastern Paleo-Tethys realm, so the spatiotemporal transitions in SGC provenance provide the potential to constrain the closure time. A comprehensive multiproxy provenance investigation, integrating detrital zircon UPb geochronology, whole-rock SmNd isotope data, and paleocurrent analysis, shed light on the origin of the Triassic SGC turbidites. In this study, it was determined that a significant proportion (exceeding 70%) of the detrital material comprising the SGC turbidites was sourced from the northwestern margin of the Yangtze Craton and the Qinling Orogen. A comprehensive and quantitative provenance study revealed that the Songpan-Ganzi turbidites primarily originated from collisional orogenic belts at convergent continental plate margins and secondarily from magmatic arcs and other tectonic units surrounding the basin. In this study, it was demonstrated that the SGC contains important information on the convergence of Eurasia and the tectonic evolution of surrounding terranes. (1) The South Qinling Orogen experienced significant rapid exhumation during the Ladinian to early Carnian. (2) The closure of the Paleo-Jinsha Ocean most likely occurred during the transition period between the upper and lower members of the Zhuwo Formation (ca. 231 Ma, middle Carnian). (3) During the Late Triassic, the crust of the Yidun Terrane underwent significant vertical accretion, resulting in a topography exceeding that of the Jomda-Weixi arc by the late Norian.

A new method for finding the proper initial conditions in passive locomotion of bipedal robotic systems

In this paper, the walking motion of a biped robot consisting of upper and lower body members (arms, legs, upper trunk and neck) on an inclined surface is analyzed kinematically and dynamically. Some of the challenges faced by this research include the dual-phase dynamics that govern the periodic gait of this robotic system and the consideration of all the body parts that are involved in the walking motion; which make it extremely difficult to derive the kinetic equations of such robotic systems. To deal with these challenges, the Gibbs-Appell formulation and the Newton's impact laws are employed to derive the most general form of the system's dynamic equations in the swing and transient phases of motion. Subsequently, by using the obtained motion equations and implementing a systematic procedure, we achieve an eigenvalue problem. By solving this problem, the suitable initial conditions that are necessary for the passive gait of this biped robot on a sloping surface are determined. By considering the obtained initial conditions as well as the dynamic response of the system to the Earth's gravity, we describe a general method for designing a biped robot's walking trajectory on an inclined surface. The most important feature of the designed trajectory is its close agreement with the trajectory followed by a biped robot walking passively down a sloping ramp. This close match between the said trajectories enables us to guide the robot in tracking a desired path by applying very small control torques to the robot joints at the start of each step. This claim is corroborated by the simulations carried out for a biped walking robot composed of 6 rigid links, in which the control torques that are applied to the actuated robot joints are obtained by employing a feedback linearization method and via a designed LQR controller.

Kasimovian (late Pennsylvanian) cornute rugose corals from Egypt: taxonomy, facies and palaeogeography of a cool-water fauna from northern Gondwana

A strongly endemic Upper Pennsylvanian (Kasimovian) rugose coral association consisting of small, mostly non-dissepimented, simple structured and poorly diversified species is studied from the lower member of the Aheimer Formation (Western side of the Gulf of Suez, Egypt). The unit is composed of grey, silty mudstone intercalated with thin, ferruginous, silty dolostone–limestone and calcareous siltstone beds. Ten taxa from four families were identified. Four species of the Antiphyllinae are new; Actinophrentiscrassithecata n. sp., Lytvolasmaaheimerensis n. sp., L.paraaucta n. sp. and Monophyllumgalalaensis n. sp. Besides, Rotiphyllumexile de Groot, 1963 and Bothrophyllumokense Kossovaya, 2001 were identified; four taxa remain in open nomenclature (Lytvolasma cf. canadense, Zaphrentites cf. parallela, Zaphrentites sp. and Ufimia sp.). Rejuvenation, encrustation and bioerosion phenomena are rare. Attachment structures during mature stages are not evident; attachment scars in the apical parts are also rare. Growth patterns and embedding in the muddy deposits indicates that the corals lived as mudstickers in soft substrate. Recrystallization, dolomitization and ferrugination of open pore spaces inside the corals are the most common diagenetic features. The corals from the lower Aheimer Formation represent a typical cyathaxonid fauna that was adapted to high clastic input and turbid waters in a restricted, sheltered, episodically storm-swept inner ramp environment in an embayment of the southern shelf of the Palaeotethys. A time-averaged ramp model shows a regressive development from a mixed carbonate–siliciclastic open inner ramp setting during the Moscovian to the restricted inner ramp of the lower Aheimer Formation (Kasimovian) and following peritidal to fluvial environments of the Gzhelian. General and local palaeoclimatic considerations indicate cooling. Besides relations to northern Spain that root Egypt in the western Palaeotethys, connections existed via the Donets Basin (and the southern Urals) to the Cordilleran–Arctic–Uralian realm which is a cool water province during the Lower and Middle Permian. The Egyptian fauna appears to be a precursor of the anti-tropical cyathaxonid fauna of the latter time slice and also of the Lower Permian cool-water faunas of the east Cimmerian peri-Gondwana terranes.

Target-based sedimentary diagenesis simulation and three-dimensional diagenesis evolution modeling

Deposition and diagenesis are important factors affecting the quality of oil and gas reservoirs. Previously reported diagenesis studies mainly involve qualitative analysis, such as the determination of diagenetic events and diagenetic evolution sequences and modeling of two-dimensional diagenetic evolution, with less effort devoted to quantitative numerical simulation and three-dimensional diagenetic evolution models. This study proposes a new method for target-based diagenesis simulation by integrating the discrete element method, the quartet structure generation set method, and morphological algorithms. This new hybrid method can quantitatively simulate the effects of mineral grain deposition, compaction, cementation, dissolution, and replacement. Since specific minerals can undergo specific diagenetic alterations through mineral labeling, the sequence and path of diagenesis can be predefined in this method. Taking the sandstone reservoir of Lower Member 3 of the Shahejie Formation in Linnan Sag, Huimin Depression, Bohai Bay Basin, East China as an example, the new simulation method used the constructed diagenetic evolution sequence based on thin section identification and geochemical analysis to systematically simulate deposition and diagenesis in the study area and to construct a three-dimensional diagenetic evolution model. The predicted porosity, permeability, and pore size distribution of the simulated digital rocks are in good agreement with the experimental values, which validates the high accuracy of the simulation method. Based on these three-dimensional multi-mineral evolution models, the evolution trends of porosity and permeability during the sedimentation and diagenesis process were elucidated, revealing the variation in reservoir quality in the studied area and indicating reservoir sweet spots. The constructed 3D diagenesis evolution models are widely applicable and can be used not only for permeability simulation but also for the study of electrical, acoustic, and mechanical properties of reservoirs.

Dynamic deep-water oxygenation of marginal seas in the aftermath of the Sturtian Snowball Earth: Insights from redox-hydrological reconstructions of the Nanhua basin (South China)

The Cryogenian interglacial period, separated by the Sturtian and Marinoan icehouses, witnessed early radiations of eukaryotic algae and the first emergence of putative metazoans. To date, the detailed oceanic redox state in the aftermath of the Sturtian glaciation remains obscure, limiting our understanding of the causal linkage, if any, between environmental changes and biological evolution during this critical interval. In order to gain further insights into the marine redox framework following the Sturtian Snowball glaciation, here we present high-resolution geochemical results of an integrated study on the basal Datangpo Formation from the Daotuo area (South China), and also provide a systematically compiled dataset of counterparts in other profiles from the Nanhua Basin. The basal Datangpo Formation is characterized by black shales intercalated with Mn carbonate ore layers in the lower (Member I), and only black shales in the upper (Member II). The Member I black shales have relatively high abundances of Mo and Re, and display a MoEF-UEF pattern typical of Mn-oxide shuttle, indicating that the Nanhua basin was redox-stratified with the oxic-euxinic chemocline fluctuating above the deep-basin floor. Multiple lines of evidence, including positive PAAS-normalized Ce anomalies, negative δ13Ccarb values, and marked authigenic enrichments of manganophile elements (Co, Ni, Cu), imply that the Mn carbonate ore beds were generated through the diagenetic transformation of Mn oxides originally deposited under oxic bottom waters. Therefore, these Mn ore layers hosted by the Member I black shales reflect episodic benthic oxygenation. By contrast, the Nanhua basin was more stagnant during deposition of Member II black shales, as supported by their rather low Mo/TOC ratios, as well as the relatively lower abundances of Mo and Re compared to Member I black shales. Moreover, the Mo isotope data of the basal Datangpo Formation indicate that the global ocean remained pervasively anoxic. Taken together, this study reveals a more holistic redox landscape in the wake of the Sturtian Snowball Earth—that is, extensive anoxia in the global ocean with episodic deep-water oxygenation in the marginal seas such as the Nanhua Basin. These epicratonic seas with dynamic redox variations might promote the ecological revolution during the interglacial period immediately after the Sturtian glaciation.

ABHYANTAR KRIMI (INTESTINAL WORM INFESTATION - PUREESHAJ KRIMI) AND THEIR MANAGEMENT: A REVIEW

The utility of Ayurveda science is to preserve a healthy individual's health and to treat a patient's ailment. Ayurveda defines health as a balanced condition of dosha, dhatu, agni, mala and a pleasant state of soul, sense organs, and mind. In today's contemporary environment, there is less emphasis placed on health. In the midst of a flurry of labor, lower socioeconomic group members lack basic hygiene, literacy, and the usage of undercooked food or incorrect cleaning of food items, among other things. This is the main reason of Abhyantar Krimi (helminthiasis) in children, which is ignored by both parents and physicians as it is one of the common pediatric problems faced worldwide especially in tropical and subtropical geographical region. Helminthiasis is noticed, when it became severe and cause harm to the children. According to recent worldwide estimates, more than a quarter of the world's population is affected with one or more parasitic illnesses, the most frequent of which is round worm, Ascaris lumbricoides. Ayurveda classics have so many references of helminthiasis named as Krimi roga. Acharyas states 20 type of Krimi classified as Bahya and Abhyantar in which helminthiasis can be correlated with Pureeshaj Krimi. Krimighna (anti helminthic) medicines are available in market, causing side effects like nausea, vomiting, lethargy, etc. Today’s world, Medicinal plants are gaining relevance in the current day due to the different negative effects of modern medication and the less adverse effects of Indian medicinal herbs. Current article presented by the introduction of Pureeshaj Krimi and their management with herbs.

Ammonites and stratigraphic succession of the middle Toarcian – lowermost Aalenian from the Jebel Amergou (Moulay Bouchta area, Internal Prerif Zone, External Rif belt, northern Morocco)

In the Rif Belt, the Toarcian–Aalenian outcrops are rare. The most important of these outcrops are those of the northern side of Jebel Amergou (70 km northwest of Fez). These outcrops, consisting of lumpy marlstones and marly limestones, are rich in ammonites. A section (JAM) located in a small ravine near Douar Amergou have been studied. Its stratigraphic series (20 m-thick), called the Amergou Formation, is divided into two members. The lower member yielded in the levels 3 and 4 a rich ammonite fauna from the middle Toarcian (Bifrons and Gradata zones) and some ammonites from the upper Toarcian (Bonarellii and Speciosum? zones); the upper member, divide into two levels, yielded in the level 2 rare ammonites from the lower Aalenian (Opalinum Zone). 44 species of ammonites have been identified, described and illustrated for the first time from the Toarcian–lower Aalenian succession of the Rif Belt. Most of these species are common to several basins of both, the northern and the southern margins of the Tethys and the NW European province.

Sedimentary environments in the prelude to the lagerstätten conditions of the Tlayúa Formation (Albian) in central Mexico: A microfacies approach

This contribution presents the first detailed microfacies analysis of the Lower Member of the Albian Tlayúa Formation outcropping in southern Mexico. The basis for this study consists of two measured stratigraphic sections named Tlayúa and Barranca Abuelo. The Tlayúa section is a composite section ∼48 m thick that includes the sedimentary record of the Lower Member and the first 12 m of the Middle Member. This carbonate succession directly precedes the fossil Lagerstätten deposits of the Middle Member exposed at Tlayúa Quarry. A second stratigraphic section of ∼23 m outside of Tlayúa Quarry includes the transitional contact between the Lower and Middle members and is documented herein for the first time. A detailed microfacies analysis combined with stratigraphic and sedimentologic data suggests that the Tlayúa deposits are part of a tropical shallow-water carbonate platform similar to the modern Great Bahama Banks.Microfacies analysis of the studied sections reveals the evolution of a protected carbonate setting affected by recurring storm events of different intensities. The succession records shelf lagoon sedimentation for most of the Lower Member and its gradual change to tidal flat deposition in its upper part. Shelf lagoon deposits consist of a diverse set of subtidal microfacies characterized by a carbonate fabric with low taxonomic group diversity that indicates stressed environmental conditions. Tidal flat deposits consist of shallowing upward cycles, each less than 1 m thick. Commonly, the peritidal cycles are incomplete and consist of mud-rich shallow-subtidal intertidal microfacies, which are clearly observed at the top of the Lower Member. Both microfacies are similar to those observed in the complete cycles described below. The complete cycles consist of mud-rich shallow-subtidal microfacies with low diversity of bioclasts that gradually change to intertidal microfacies characterized by the association of microbialites with desiccation features that suggest intermittent subaerial exposure. Intertidal microfacies record an important change in the composition of the carbonate factory because microbial processes generated most of the sediments in these microfacies. Supratidal deposits characterized by the presence of subaerial exposure structures and calcified pedogenic products, complete the peritidal succession and were identified at the base of the Middle Member. Thus, the presence of soil pisoid-like structures, clotted micrite, possible Microcodium structures, and alveolar textures indicate a sufficiently long subaerial exposure for the formation of pedogenic products, and therefore, a break in the marine sedimentation of the Tlayúa Formation.