Major Geological Events Research Articles

Marine biofilms: cyanobacteria factories for the global oceans.

Cyanobacteria, highly diverse microbial organisms, play a crucial role in Earth's oxygenation and biogeochemical cycling. However, their connection to these processes remains unclear, partly due to incomplete surveys of oceanic niches. Our study uncovered significant cyanobacterial diversity in marine biofilms, showing distinct niche differentiation compared to seawater counterparts. These patterns reflect three key stages of marine cyanobacterial diversification, coinciding with major geological events in the Earth's history.

The Mundeck Salt Unit: A Review of Aptian Depositional Context and Hydrocarbon Potential in the Kribi-Campo Sub-Basin (South Cameroon Atlantic Basin)

The Kribi-Campo sub-basin, located in the Gulf of Guinea, constitutes the southeastern segment of the Cameroon Atlantic Margin. Drilling in the Aptian salt unit revealed a sparse hydrocarbon presence, contrasting with modest finds in its counterparts like the Ezanga Salt in Gabon and the Rio Muni Salt in Equatorial Guinea. This discrepancy prompted a reassessment of the depositional context and hydrocarbon potential of the Mundeck salt unit. By integrating 2D seismic reflection and borehole data analysis, this study established the structural and stratigraphic framework of the area, emphasizing the salt unit’s significance. Borehole data indicate a localized salt unit offshore Kribi, with seismic reflection data revealing distinct forms of diapir and pillow. This salt unit displays a substantial lateral extent with thicknesses ranging from 4000 m to 6000 m. The depositional context is linked to the following two major geological events: a significant sea-level drop due to margin uplift during the Aptian and thermodynamic processes driven by transfer faults related to mid-oceanic ridge formation. These events were crucial in forming and evolving the Mundeck Salt. Regarding hydrocarbon prospects, this study identifies the unit as being associated with potential petroleum plays, supported by direct hydrocarbon indicators and fault-related structures. The findings suggest that untapped hydrocarbon resources may still exist, underscoring the need for further exploration and analysis.

Impact of Tethyan domain evolution on the formation of petroleum systems in the Sichuan super basin, SW China

Based on the “unidirectional break-up and convergence” geodynamic model, this study investigates the impact of the evolution of the Tethyan domain on the formation of petroleum systems in the Sichuan super basin and explores the enrichment pattern of natural gas. The results show that, firstly, the Sichuan Basin and its surrounding areas have experienced two unidirectional rifting-aggregation cycles triggered by the Proto-Tethys Ocean and the Paleo-Tethys Ocean during the Neoproterozoic to Triassic. During Jurassic–Cenozoic, the Sichuan Basin is incorporated in the circum-Tibetan plateau basin-mountain coupled tectonic domain system. The episodic tectonic movements within the plate control the sedimentary infill styles. Second, the evolution of the Tethyan domain, paleoclimatic environment and major geological events controlled the formation and distribution of high-quality source rocks within the basin. The rift valley and intracratonic rift, passive continental margin slope, and intracratonic sags are favorable areas for the development of source rocks. Third, the evolution of the Tethyan domain, supercontinent cycles, global sea level changes, and tectono-climatic events controlled the distribution of carbonate platform and reservoir-caprock combinations. The cratonic platform margins and sub-platform internal high terrains are key areas for finding carbonate high-energy facies belts. Syndepositional paleo-uplifts and surrounding slopes, regional unconformities, and later faults zone are areas where large-scale carbonate reservoirs are distributed. The regional evaporite or shale caprock are beneficial for the large-scale preservation of oil and gas in the basin. Fourth, the spatio-temporal matching relationship of reservoir forming factors influenced by the early tectonic-sedimentary evolution pattern and the degree of later tectonic modification is the key to oil and gas enrichment. Future oil and gas exploration should focus on potential gas systems during the Sinian rift period, Cambrian pre-salt gas systems in the eastern and southern Sichuan, as well as whole oil and gas systems of Permian and Triassic.

Cyclostratigraphy of late Cambrian marine sedimentary records and reconstruction of Earth-Moon system parameters

The Cambrian period is an important era in geological history, marked by numerous major geological and biological events. To better understand these events, it is important to establish a high-precision chronostratigraphic framework. An astronomical time scale can be created by the identified Milankovitch cycles in well-preserved stratigraphic successions. Duibian B section in Jiangshan (Zhejiang Province, China) is the global stratotype section and point (GSSP) for the Jiangshanian Stage, and this section provides well-preserved records covering the upper Paibian to lower Jiangshanian stages. In this study, we use high-resolution magnetic susceptibility record to conduct cyclostratigraphic analysis of the Duibian B section. Our results indicate that the 2.44 m, 0.84–0.73 m, 0.20–0.19 m, and 0.12–0.09 m sedimentary cycles may represent long-eccentricity, short-eccentricity, obliquity, and precession cycles, respectively. Using the stable 405-kyr eccentricity cycles, we constructed an ∼5.96 Myr floating astronomical time scale to calibrate agnostoid trilobite zones. In addition, we reconstructed the precession rate k from geological records, and our result provides an insight into the Earth-Moon distance and length of day in the late Cambrian (Paibian–Jiangshanian, ∼494.2 Ma). It enriches our understanding of the Earth-Moon evolutionary history in deep time.

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The Zagros Mountain range in western Iran is an area of species endemism within the Irano-Anatolian biodiversity hotspot. A couple of relict and morphologically isolated species have been reported for the Zagros Mountains, yet their distribution patterns in relation to the geological and climatic history of the region are not fully understood. Clinopodium kallaricum (Jamzad) Bordbar, 2019 (Lamiaceae), Hypericum dogonbadanicum Assadi, 1984 (Hypericaceae), and Iranoaster bachtiaricus (Mozaff.) Kaz. Osaloo, Farhani & Mozaff. 2018 (Asteraceae) are local endemic species restricted to Zagros with no clear affinities to the Irano-Turanian or other Northern Hemisphere temperate species. Previous studies suggested some afromontane relations for these species, beyond the Saharo-Sindian lowlands. Here, we provide dated phylogenies for these three species, to assess the most probable drivers behind this pattern of distribution. Our results represent that the split between these taxa and their relatives is not contemporaneous, implying different biogeographical histories. I. bachtiaricus originated in the Middle Miocene, while C. kallaricum and H. dogonbadanicum are relatively younger (late Miocene early Pliocene). The divergence of these taxa coincided with the major geological and climatic events of the Miocene, mainly the collision of the Afro-Arabia and Eurasia plates in 18-16 Mya and the aridification of the Sahara (started in 11-7 Mya), followed by a shift in the vegetation of the Sahara from subtropical/steppe to arid desert. The possible relict nature of these species is discussed, and the role of the Saharo-Sindian Region as a vicariant agent is highlighted, which could have subdivided formerly uniform populations and subsequently accelerated the allopatric speciation.

Trichinella: Becoming a parasite

Phylogenetic evidence indicates that free-living nematodes gave rise to parasitic nematodes where parasitism evolved independently at least 15 times. The high level of genetic and biological diversity among parasites dictates an equally high level of diversity in the transition to parasitism. We previously hypothesized that horizontal gene transfer (HGT) played an important role in the evolution of parasitism among early ancestors of Trichinella, mediated by an interplay of ecological and evolutionary pathways that contributed to persistence and diversification. We propose that host selection may have been associated with the metabolism of ammonia and engender a new paradigm whereby the reprogrammed nurse cell is capable of generating cyanate thereby enabling the importance of the Trichinella cyanase in the longevity of the cell. Parasites and parasitism have revealed considerable resilience against a backdrop of climate change and environmental perturbation. Here we provide a putative link between key periods in the evolution of Trichinella and major geological and climatological events dating back 500 million years. A useful lens for exploring such ideas, the Stockholm Paradigm, integrates Ecological Fitting (a foundation for host colonization and diversification), the Oscillation Hypothesis (recurring shifts between trends in generalization and specialization relative to host range), the Geographic Mosaic Theory of Coevolution (microevolutionary co-adaptive processes), and the Taxon Pulse Hypothesis (alternating events of biotic expansion i.e., exploitation in evolutionary and ecological time). Here we examine how one or more of these interactive theories, in a phylogenetic-historical context and in conjunction with HGT, may help explain the scope and depth of diversity among Trichinella genotypes.

Sedimentary Paleoenvironment and Organic Matter Enrichment Characteristics of Lacustrine Shahezi Shale in Songliao Basin: Insights from the Continental Scientific Drilling.

The lacustrine shale of the Shahezi Formation in the Songliao Basin has obvious organic matter enrichment characteristics and great potential for oil and gas resources. At present, the understanding of the sedimentary paleoenvironment and organic matter enrichment characteristics of the lacustrine shale of the Shahezi Formation is relatively weak. Therefore, taking the international continental scientific drilling Program (ICDP) borehole Songke-2 (SK-2) with continuous and whole Shahezi cores as the research object, combined with organic geochemistry, elemental geochemistry, and logging data, the sedimentary paleoenvironment and organic matter enrichment mechanism were studied. The results show that the organic matter of Shahezi shale is generally in the high to over mature stage. The kerogen type of organic matter is mainly II2-III. The organic matter is mainly derived from the lake basin's own algae and terrestrial higher plants. The total organic carbon (TOC) content of Shahezi shale is relatively high, and the TOC is mainly distributed between 1% and 2%. The Shahezi Formation is dominated by clay shale and siliceous shale, and experienced moderate chemical weathering during deposition. According to the analysis of organic geochemistry and elemental geochemistry data, the paleoenvironment of organic matter deposition in Shahezi shale was dominated by warm and humid climate in the early stage, and then experienced multiple cooling and arid periods. The climate type turned to semihumid-semiarid, with stable terrigenous debris input, low deposition rate, brackish water salinity and oxygen-rich-oxygen-poor water environment. The sedimentary period of Shahezi Formation is in the Cretaceous oceanic anoxic Aptian-Albian stage. During the oceanic anoxic event, the anoxic sedimentary environment and the frequent volcanic activity have an important impact on the organic matter enrichment. The oceanic anoxic event and volcanic activity are the main causes of water body hypoxia in the lake basin. The nutrients brought by volcanic activity are also one of the reasons for promoting the growth of lake basin organisms, creating good conditions for organic matter enrichment. The enrichment of organic matter in Shahezi Formation is the result of the interaction and coupling of various factors such as paleoclimate, paleoenvironment, paleoproductivity, water environment, terrestrial input, and major geological events. And, the organic matter enrichment model of Shahezi Formation shale is established.

Geochemical Characteristics of Trace Elements and Mineralization Model of the Ediacaran-Early Cambrian Phosphorites, South China.

As a nonrenewable resource, phosphate rock is an important support for the development and survival of the national economy. The regional distribution and output of phosphate rock in China are extremely uneven, and the amount of high-quality ore resources is relatively poor, which seriously restricts the development and utilization of phosphate rock resources in China. This paper briefly summarizes the distribution characteristics of phosphate rock resources and summarizes the characteristics and research progress of Ediacaran-early Cambrian phosphorus mineralization types, geological characteristics, and deposit genesis of the Yangtze platform in South China. The Ediacaran-early Cambrian sedimentary phosphorite deposits in China are mainly distributed in Yunnan, Guizhou, Hubei, Sichuan and Hunan provinces of the Yangtze platform, in which the early Cambrian phosphate deposits are also rich in rare earth elements, associated with uranium, nickel, molybdenum, vanadium, and other beneficial metal elements. The increase of atmospheric oxygen content at the Ediacaran-Cambrian boundary may have promoted the extensive oxygenation of the late Neoproterozoic oceans, so the Ediacaran-early Cambrian oceans generally showed a reductive environment, and there may be dynamic chemical stratification of the oxidation zone-sulfide zone-iron zone. Up to the early Cambrian, the redox stratified structure of Precambrian seawater may still be inherited, showing that the surface water is an oxidizing environment, changing to a reduction environment, and even wedge-shaped sulfide water is developed at the bottom of the deep basin. The main phosphorus sources are deep phosphorus-rich seawater, continental weathering, and deep hydrothermal activity of Ediacaran-early Cambrian marine sedimentary phosphorite deposits in South China. The genetic mechanisms of phosphorite deposits in the Yangtze platform in South China are mainly biogenic, upwelling phosphorus-forming theory, mechanical mineralization, and syn-sedimentary hot water mixed genesis. In the future, it is still necessary to further explore the internal relationship between phosphorus deposits and major geological events, the in situ analysis of microstructure of phosphate rock ores, and the genetic mechanism of phosphate deposits and the reconstruction of paleo-marine environment.

Two pulsed activities of the Emeishan large igneous province in southwestern China inferred from dolomite U-Pb geochronology and significance

Abstract The Emeishan large igneous province (ELIP) was a major geological event that took place around the Middle–Late Permian boundary. The major episode of the ELIP is generally considered to have occurred at 260–259 Ma, although an increasing number of geological data have suggested that multiple episodes of magmatic activity might have occurred. Here we report a study of a Lower Permian dolomite whose formation was influenced by the ELIP in the Sichuan Basin of southwestern China. Results show two new pulsed activities at 273.2 ± 9.7 Ma to 269.1 ± 12.0 Ma (ELIP-I) and 263.2 ± 10.3 Ma to 258.7 ± 8.1 Ma (ELIP-II). The two stages of the ELIP magmatism and thermal activity controlled the regional tectonic, sedimentary, and diagenetic evolution and exerted a profound influence on the oil and gas reservoirs, source rocks, and lithofacies paleogeography. This study is the first to interpret the timing of the ELIP from analysis of hydrothermal dolomite and provides new clues and data for improving our understanding of the dynamic formation mechanism and Earth system of the ELIP.

Structure and elasticity of CaC2O5 suggests carbonate contribution to the seismic anomalies of Earth’s mantle

Knowledge of carbonate compounds under high pressure inside Earth is key to understanding the internal structure of the Earth, the deep carbon cycle and major geological events. Here we use first-principles simulations to calculate the structure and elasticity of CaC2O5-minerals with different symmetries under high pressure. Our calculations show that CaC2O5-minerals represent a group of low-density low-seismic-wave velocity mantle minerals. Changes in seismic wave velocity caused by the phase transformation of CaC2O5-Cc to CaC2O5-I4¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\bar{4}$$\\end{document}2d (CaC2O5-C2-l) agree with wave velocity discontinuity at a depth of 660 km in the mantle transition zone. Moreover, when CaC2O5-Fdd2 transforms into CaC2O5-C2 under 70 GPa, its shear wave velocity decreases by 7.4%, and its density increases by 5.8%, which is consistent with the characteristics of large low-shear-velocity provinces (LLSVPs). Furthermore, the shear wave velocity of CaC2O5-I4¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\bar{4}$$\\end{document}2d is very similar to that of cubic Ca-perovskite, which is one of the main constituents of the previously detected LLSVPs. Therefore, we propose that CaC2O5 and its high-pressure polymorphs may be a main component of LLSVPs.

Cretaceous stratigraphic framework and sedimentary architecture, Pakistan: signatures of rift–drift tectonics and submarine volcanism along the western continental margin of the Indian Plate

Abstract The lithostratigraphy, biostratigraphy and depositional environments of the Cretaceous successions in Pakistan were investigated to reveal the major geological events, including local, regional and global-scale tectonics, phases of volcanism, basin condensation, emergence of structural highs and episodes of non-deposition. The succession is entirely missing at Salt Range but is excellently exposed in the Kirthar–Sulaiman Fold-Thrust belts. Such deviating nature (e.g. Hazara, Kala Chitta, Surghar and Kohat), suggesting episodical tectonic activities, is associated with inter–intra rifting and drifting of the India–Madagascar–Seychelles and Antarctica–Australian plates during the Cretaceous. Correspondingly, several unconformities within the Cretaceous succession at numerous stratigraphic intervals consistently attest to the effect of tectonics throughout the period. The recognized unconformities over Kawagarh, Lumshiwal, Parh and Fort Munro formations testify to episodic uplifts on local and/or regional scales during the Coniacian–Santonian, Coniacian–Maastrichtian, Campanian and Maastrichtian in response to the separation of Madagascar from the India–Seychelles Plate. In contrast, there was continuous sedimentation of carbonate, clastic and/or submarine volcanics in the Kirthar and Indian–Eurasian suture zone. Significant geological events in the restricted regions, e.g. local-scale submarine volcanism (Bibai Formation), ironstone deposition (Dilband Formation) and basin condensation (Khuzdar), were also associated with such rifting–drifting phases along the WNW margin of the Indian Plate.

Evolution of the Lunar Tectonic Framework and Structures

The evolution of the Moon is driven by both endogenic (e.g., magmatism) and exogenic processes (e.g., impact). The lunar surface can be divided into 3 first-order tectonic units based on differences in geochemistry, crustal thickness, topography, and distribution of structures. However, the interpreted boundaries demarcated by different features varied widely. As research progresses, the understanding of the lunar structure is continuously improving, and new types of structures are constantly being discovered. The previous structural classification system needs to be updated. According to the major geological events and dynamic evolution, the evolutionary history of the Moon can be divided into 3 stages and 1 pivotal event. The first stage (4.52 to 4.3 Ga) is the evolution of the magmatic ocean, and it was dominated by endogenic processes. The formation of South Pole-Aitken (SPA) basin (~4.3 Ga) is the pivotal event of crustal evolution and indicates that the lunar crust had cooled and consolidated to sufficient rigidity to preserve structures. Both endogenic and exogenic processes were active in the second stage (4.3 to 3.0 Ga), which results in numerous impact basins, mare basalt flooding, and different types of associated structures. The last stage (3.0 Ga to the present) is late neotectonic activity, which has weak modification of the tectonic framework. Response of tectonic framework and structure to lunar major geological events had been organized and discussed in this paper, and key scientific issues are summarized. This study can provide reference and support for implementation of subsequent lunar exploration projects.

The phylogenetic reconstruction of the Neotropical cycad genus Ceratozamia (Zamiaceae) reveals disparate patterns of niche evolution

The cycad genus Ceratozamia comprises 40 species from Mexico, Guatemala, Belize, and Honduras, where cycads occur throughout climatically varied montane habitats. Ceratozamia has the potential to reveal the history and processes of species diversification across diverse Neotropical habitats in this region. However, the species relationships within Ceratozamia and the ecological trends during its evolution remain unclear. Here, we aimed to clarify the phylogenetic relationships, the timing of clade and species divergences, and the niche evolution throughout the phylogenetic history of Ceratozamia. Genome-wide DNA sequences were obtained with MIG-seq, and multiple data-filtering steps were used to optimize the dataset used to construct an ultrametric species tree. Divergence times among branches and ancestral niches were estimated. The niche variation among species was evaluated, summarized into two principal components, and their ancestral states were reconstructed to test whether niche shifts among branches can be explained by random processes, under a Brownian Motion model. Ceratozamia comprises three main clades, and most species relationships within the clades were resolved. Ceratozamia has diversified since the Oligocene, with major branching events occurring during the Miocene. This timing is consistent with fossil evidence, the timing estimated for other Neotropical plant groups, and the major geological events that shaped the topographic and climatic variation in Mexico. Patterns of niche evolution in the genus do not accord with the Brownian Motion model. Rather, non-random evolution with shifts towards more seasonal environments at high latitudes, or shifts towards humid or dry environments at low latitudes explain the diversification of Ceratozamia. We present a comprehensive phylogenetic reconstruction for Ceratozamia and identify for the first time the environmental factors involved in clade and species diversification within the genus. This study alleviates the controversies regarding the species relationships in the genus and provides the first evidence that latitude-associated environmental factors may influence processes of niche evolution in cycads.

Cretaceous stratigraphic framework and sedimentary architecture, Pakistan: signatures of rift-drift tectonics and submarine volcanism along the western continental margin of the Indian Plate

Abstract Abstract The lithostratigraphy, biostratigraphy and depositional environments of the Cretaceous successions Pakistan were investigated to reveal the major geological events, including local, regional and global scale tectonics, phases of volcanism, basin condensation, emergence of structural highs and episodes of non-deposition. The succession is entirely missing at Salt Range, but were excellently exposed in Kirthar-Sulaiman Fold-Thrust belts. Such deviating nature (e.g., Hazara, Kalla Chitta, Surghar & Kohat) suggesting episodical tectonic activities were associated with inter-intra rifting and drifting of the India-Madagascar-Seychelles and Antarctica-Australian Plates during Cretaceous time. Correspondingly, several unconformities within the Cretaceous succession at numerous stratigraphic intervals consistently attest the effect of tectonics throughout the period. The recognized unconformities over Kawagarh, Lumshiwal, Parh and Fort Munro formations testify episodic uplifts on local and/or regional scales during the Coniacian-Santonian, Coniacian-Maastrichtian, Campanian and Maastrichtian in response to the separation of Madagascar from the India-Seychelles plate. In contrast, there was continuous sedimentation of carbonate, clastic and/or submarine volcanics in the Kirthar and Indian-Eurasian suture zone. Significant geological events in the restricted regions e.g., local scale submarine volcanism (Bibai Formation), ironstone deposition (Dilband Formation) and basin condensation (Khuzdar) were also associated with such rifting-drifting phases along the WNW margin of the Indian Plate.

Semantic Mapping of the Geologic Time Scale: A temporal reference

The Geologic Time Scale is an ordered hierarchical set of terms representing specific time intervals in Earth's history. The hierarchical structure is correlated to the geologic record and major geologic events in Earth’s history (Gradstein et al. 2020). In the absence of quantitative numeric age values from absolute dating methods, the relative time intervals in the geologic time scale provide us with the vocabulary needed for deciphering Earth’s history and chronological reconstruction. This temporal frame of reference is critical to establishing correlations between specimens and how they fit within the Earth’s 4.567 Ga (giga annum) history. Due to spatial and temporal variations in the stratigraphic record, the terminology used in conjunction with geologic time scales is largely inconsistent. For a detailed discussion regarding term use in geologic timescales, see Cohen et al. (2013). As a result, published values for geologic timescale terms are often ambiguous and highly variable, limiting interoperability and hindering temporal correlations among specimens. A solution is to map verbatim geologic timescale values to a controlled vocabulary, constructing a single temporal frame of reference. The harmonization process is governed by an established set of business rules that can ultimately become fully or partially automated. In this study, we examined the Global Biodiversity Information Facility’s (GBIF) published distinct verbatim values for Darwin Core terms in the GeologicalContext Class of Darwin Core to assess the the use of chronostratiphic terms, a process highlighted in Sahdev et al. (2017). Preservation of these verbatim values, the initial unmapped set of published values, is important. Many are derived directly from primary source material and possess special historical and regional significance. These include land mammal ages (e.g., Lindsay (2003)), biostratigraphic zones, regional terms, and terms with higher granularity than the International Commission of Stratigraphy’s (ICS) timescale allows (e.g., subages/substages). For the purposes of this study, we selected the 2023/6 version of the ICS chronostratigraphic timescale as the controlled vocabulary (Cohen et al. 2023). The ICS is the most widely adopted timescale, comprising the most generalized and universally applicable intervals of geologic time. After semantic analysis of the verbatim values (see Table 1 for comparative statistics), we established a comprehensive set of business rules to map to the ICS timescale controlled vocabulary. This process yielded a collection of documented procedures to transform the heterogeneous collection of published terms into a semantically consistent dataset. The end result is a single temporal frame of reference for published geologic and paleontological specimens through semantic mapping to improve the temporal correlations between geologic specimens globally through data interoperability. This talk will highlight the process of harmonizing a heterogeneous collection of published verbatim Geologic Time Scale values with an established controlled vocabulary through semantic mapping.

Sedimentary Environment and Organic Accumulation of the Ordovician–Silurian Black Shale in Weiyuan, Sichuan Basin, China

The sedimentary environment and organic matter enrichment relationship of the Upper Ordovician Wufeng Formation black shale, Guanyinqiao mudstone, and Lower Silurian Longmaxi Formation black shale in the Sichuan Basin of Weiyuan are analyzed using geochemical methods such as organic carbon, sulfur, major elements, and trace elements. The experimental results illustrate that the upper section of the Wufeng Formation and the lower section of the Longmaxi Formation are organic matter enrichment layers. The presence of P indicates a high productivity level in the Sichuan Basin from the Late Ordovician to the Early Silurian. In addition, indicators such as V/Cr, Ni/Co, and S/C suggest that the Wufeng Formation was deposited under anoxic reductive conditions, that the ice age Guanyinqiao segment was in an oxygen-rich to oxygen-poor environment, and that the Longmaxi Formation was in a sulfidic environment. Mo/TOC indicates that the Wufeng Formation shale was controlled by a restricted basin and that the Guanyinqiao segment and the Longmaxi Formation were in a medium-to-weak retention environment. The weak correlation of TOC with P/Al and Al indicates that the level of primary productivity and terrigenous detritus had a minor effect on the organic matter enrichment of the Wufeng and Longmaxi Formation black shale. Conversely, the positive correlation of TOC with V/Cr and Ni/Co illustrates that the anoxic reductive sedimentary environment is the main factor affecting the organic matter enrichment of the Wufeng and Longmaxi Formation black shale. Based on these studies, the development model of organic-rich shales of the Ordovician–Silurian in Weiyuan, Sichuan Basin is proposed. This paper may provide a reference for shale gas exploration in the Wufeng–Longmaxi Formation and a sedimentary response to the major geological events of Ordovician–Silurian.

Benthic foraminiferal survival through the early Paleocene (Danian) greenhouse climate interval based on analysis of IODP Site U1457 (Laxmi Basin, Northern Indian Ocean)

The early Paleocene (Danian) period included three major events: the Cretaceous-Paleogene (K-Pg) extinction at 66.0 ​Ma, the Dan-C2 hyperthermal at 65.2 ​Ma, and the latest Danian hyperthermal at ∼62.2 ​Ma. In this paper, we investigate benthic foraminiferal diversity patterns, morphotypes, and oxygen conditions along with the carbonates and magnetic susceptibility records at IODP Site U1457 (Laxmi Basin, Northern Indian Ocean) to understand the effects of these Danian events on the marine community in the Indian Ocean. Findings suggest that foraminifera persisted across these major events. Species belonging to Bolivina, Glandulina, Hoeglundina, Parrelloides and Quadrimorphina genus were dominant above the K-Pg boundary whereas Bolivina, Bulimina, Cassidulina, Cornuspira, Gyroidinoides, Melonis, Oolina, Pullenia, Reussoolina and Rutherfordoides dominated across subsequent hyperthermal events. We calculated the average oxygen content at 0.16 ​ml/L in accordance with oxyphilic species abundance, which shows that the Laxmi Basin comprised, mostly, a suboxic to dysoxic environment. The benthic foraminiferal diversity patterns, primary anomalies of calcium carbonates, and magnetic susceptibility, integrated with previously-published global datasets of carbon and oxygen isotopes, help to define the major geologic events at the study site and show how biotas responded to global change during the early Paleocene greenhouse mode.

Co-existing two distinct formation mechanisms of micro-scale ooid-like manganese carbonates hosted in Cryogenian organic-rich black shales in South China

Manganese-rich deposits in the lower member of the Datangpo Formation (DTP) (ca. 663–654 Ma) in South China formed in the aftermath of the Cryogenian Sturtian glaciation. The Mn in the DTP occurs dominantly as rhodochrosite and Ca-rhodochrosite. A hydrothermal origin of the Mn2+ is shown by the rare earth element distribution and significantly high Mn/Fe ratios (3–19, average = 10.1). Previous studies suggested a microbially-mediated process for controlling the DTP black-shale hosted Mn carbonate deposits. However, detailed reports on the formation mechanisms of micro-scale (<2–5 μm) ooid-like Mn carbonates in the DTP have rarely been published. Systematic petrography and geochemical analyses in this study demonstrate the coexistence of two types of micro-scale ooidal-like Mn carbonates formed through two distinct mechanisms, either dominated by microbially-mediated or physiochemically-forced pathways. The Type I Mn carbonate has relatively larger grain size of 2–5 μm and exhibits a radial-concentric microfabric that shows signs of growth banding in the form of alternating light and dark laminae, which mainly express variation in Ca and Mn concentrations. The initial precipitation phase of the Type I Mn carbonate is interpreted to be Mn oxide/hydroxide, based on positive Ce anomalies and selective enrichments of particular trace elements. Novel evidence indicates that the capture of Mn as a carbonate phase directly from the water column by primarily precipitated calcite, which is referred to as the Type II Mn carbonate, has also contributed to the DTP Mn-rich deposits. Multiple roles of organic matter in Mn carbonate formation have been established: (1) catalysed Mn-redox cycling; (2) trapping and transportation of initial mineral precipitates to sediments; (3) serving as a carbon source; (4) regulating the morphology of the Mn carbonate. As a key link for understanding Cryogenian carbon and Mn cycling, specific formation pathways for the DTP Mn-carbonates are likely to have been controlled by given atmospheric-oceanic compositions (including oxygen level, pCO2, and redox conditions) in response to major geological and biological events during the interglacial period. In turn, massive storage of inorganic carbon and phosphorous in Mn carbonate phases would have had a substantial influence on biogeochemical carbon cycling during the Cryogenian.

Origin of Banded Iron Formations: Links with Paleoclimate, Paleoenvironment, and Major Geological Processes

Banded iron-formations (BIFs) are marine chemical sedimentary rocks composed of siliceous and ferric materials, usually with typical thin layers or sheet structures. BIFs not only record a wealth of information about the state and evolution of the lithosphere, atmosphere, hydrosphere, and biosphere but also host the majority of the economic iron resources in the world. Here, we summarize the types, mineralogical, and geochemical characteristics of BIFs; analyze their formation conditions, their oxidative mechanism, and the absence causes of BIFs; and elucidate the associations between BIFs and major atmospheric oxidation events (Paleoproterozoic great oxidation event (2.4~2.1 Ga) and Neoproterozoic oxidation event (0.8~0.55 Ga)). BIFs are intimately associated with enhanced submarine magmatic–hydrothermal activities. Finally, it is concluded that the deposition and demise of BIFs are closely related to major geological events, and these major geological events interact with each other, jointly constraining the evolution of the atmospheric and marine environment and of geo-biological and geodynamic processes.

Integrated approach using petrophysical, gravity, and magnetic data to evaluate the geothermal resources at the Rahat Volcanic Field, Saudi Arabia

It is necessary to develop and explore geothermal resources to achieve sustainable development and clean renewable energy around the Globe. Geothermal energy is crucial to the future energy supply to meet the environmentally friendly energy demand of the World. The Rahat Volcanic Field (Kingdom of Saudi Arabia) is the oldest and lengthiest Cenozoic Volcanic Field in the World. It is a dominantly a mature mafic Volcanic Field that holds three major geological events; the historic eruption (1256 C.E.), the five fingers (∼4500–1500 BP), and the seismic swarm (1999 C.E.). These incidents were studied by utilizing geological information and geophysical data sets. Geophysical and geostatistical research includes gravity and magnetic survey data, including different log curves and major elements, obtained from water samples as well as of volcanic rocks obtained by X-ray fluorescence (XRF). To gain an understanding of the subsurface thermal structure, these datasets were analyzed. The primary goal of this study is to identify the prominent potential geothermal resources with the help of an available data set. Findings suggest that beneath the historic eruption site along with the fissure eruption, on the western side, there is a geothermal anomaly with a surface footprint of about 35 km2. Analyzing gravity and magnetic data as well as density and magnetic susceptibility variations in rock samples led to the mapping of this anomaly. It has been inferred through integrated study that statistical analysis of major elements will be helpful to validate the results of the outcome.