Clastic Research Articles

Silurian–Devonian boundary in Northern Xinjiang, NW China

During the Silurian–Devonian Boundary (SDB) interval, in contrast to the predominantly carbonate facies observed in Europe and North America, China was composed of several plates/terranes dominated by clastic and pyroclastic rocks. Continuous sections across the SDB have been only sporadically reported from the orogenic belts and southwestern margin of South China. In many regions or sections in China, the identification of the SDB is based solely on fossil assemblages or non-index fossils, which results in only a rough approximation of the position of the boundary. This study focuses on the Junggar area in the Central Asian Orogenic Belt, characterized by pyroclastic rocks and scarcity of fossils compared to regions with carbonate dominated successions. This paper summarizes previous research findings and discusses the SDB in northern Xinjiang, China, integrating new data on Devonian conodont Caudicriodus hesperius, the presence of benthic organisms represented by encrinurid trilobites and crinoids, and the occurrence of late Silurian graptolites, along with the first organic carbon isotope curve around the SDB for the Central Asian Orogenic Belt, and provided crucial evidence for the recognition of the SDB in the orogenic belt area of China, consindering the SDB in Northern Xinjiang is located within the Utubulag Formation in the western Junggar and the presence of the SDB in the Kaokesaiergai Formation of the eastern Junggar has also been confirmed. The age of the corresponding strata: Utubulag, Manger, Kaokesaiergai formations are revised, and a more detailed description of the classic sections of the SDB in northern Xinjiang is provided. The new fossil and geochemical data serve as basis for recognition of the Silurian–Devonian boundary in northern Xinjiang, and also contribute to a more comprehensive understanding of paleoenvironmental events at the Silurian–Devonian transition in the northern hemisphere and the orogenic belt areas.

Petrophysical evaluation of clastic sediments of the Matulla Formation, October oil Field, Gulf of Suez province, Egypt

Petrophysical evaluation of clastic sediments of the Matulla Formation, October oil Field, Gulf of Suez province, Egypt

Sedimentary provenance and paleogeographic environment of a Mississippian coal-bearing unit in South China: Constraints from detrital zircon U-Pb ages and sedimentologic and geochemical evidence

The Mississippian Xiangbai Formation in South China is one of the oldest coal-bearing sedimentary units in China. However, the sedimentary provenance, paleogeography, and coal formation patterns of the coal-bearing strata are not well constrained. We address this key issue by using a combination of detrital zircon U-Pb data, geochemical analyses of mudstone and shale, drilling data, and geologic field observations. With the exception of the early Paleozoic orogenic events (ca. 440–420 Ma) in the eastern part of the study area, the samples from the Xiangbai Formation exhibit similar detrital zircon U-Pb age distribution with major age peaks at ca. 980–960 Ma and several subordinate age peaks at ca. 800–780 and 600–500 Ma. These detrital zircon grains mainly originated from recycled sedimentary units. Field and drilling data reveal that the Xiangbai Formation was formed in a tidal flat environment with water depth gradually increasing from the bottom to the top, indicating an overall trend of transgression. The Mississippian Xiangbai Formation was deposited in an interglacial period. The Lower Xiangbai Formation was deposited in a relatively cold paleoclimate, gradually transitioning upwards to a warm and humid climate, creating favorable conditions for coal formation. The alternation of warming and cooling climates triggered high-frequency eustatic fluctuations, which led to multiple sedimentary cycles and resulted in thin, unstable coal seams within the Xiangbai Formation. Mississippian sedimentary paleogeography, palaeoclimate, and sedimentary provenance together dominate the coal-bearing clastic sediments in southwestern South China.

Petrogenesis of the > 2.90 Ga komatiite in the Sujiagou region of the North China Craton: Implications for Archean mantle source and geodynamic setting

Komatiite, characterized by high MgO content and low H2O concentration, is crucial to understanding the Archean magma processes and crust–mantle differentiation. Although well preserved in most cratons, Archean komatiites are scarce in the North China Craton (NCC). The Sujiagou komatiites, as the most typical Archean komatiites in China, were exposed in the Luxi terrane, but their geochronology and petrogenesis types remain controversial. In this study, our new Re–Os data indicate the Sujiagou komatiites originated before 2.90 Ga. The felsic zircons discovered in the komatiites, coupled with Nb–Th–La simulation, suggest ∼ 2 % crustal contamination of the komatiites. Thus, the least-altered, spinifex- and massive-texture samples that underwent unconspicuous crustal contamination were selected as proximate proxies for the primary magma composition. The Al/Ti ratios of the Sujiagou komatiites are comparable to or slightly exceed those of chondrite, suggesting they were aluminium-undepleted komatiites and formed at ∼ 8 GPa. The primitive mantle-normalized rare earth element (REE) patterns show depleted light REE and flat heavy REE, suggesting approximately 50 % partial melting based on REE simulation. Additionally, the komatiites exhibit slightly depleted Os isotope ratios, with an average γOs(t) value of -0.3, indicating the magma source is comparable to or slightly depleted to chondrite. Simulation of the relevant Nb/Zr and La/SmPM ratios further suggests the mantle source became slightly depleted due to ca. 1 % melt extraction. Furthermore, the Mg isotopic composition of the Sujiagou komatiites (δ26Mg = -0.23 ± 0.03 ‰) is consistent with that of the primitive mantle, indicating the absence of recycled carbonate material in the mantle source. Both Re–Os and Mg isotopes reveal limited involvement of crustal or carbonate material in the mantle source, implying the absence of oceanic slab subduction in the Luxi terrane during this time. The formation of the Sujiagou komatiites can be attributed to a hot mantle plume, resulting from high potential and eruption temperature. The identification of felsic zircons in the Sujiagou komatiites indicates the presence of an ancient continental nucleus in the Luxi terrane. Combined with the spatially adjacent terrigenous clastic sedimentary rocks, we suggest that the Sujiagou komatiites erupted most likely in a continental margin of the old terrane.

Multiple episodes of late Neoproterozoic rifting in the Tarim Craton during its separation from the supercontinent Rodinia

In this paper, we review and evaluate the magmatic history, regional stratigraphy, structural patterns and sedimentary provenance features of the Late Neoproterozoic Tarim Craton to elucidate the nature and different modes of extensional tectonics during the Latest Neoproterozoic, a critical time coinciding with the disintegration of the supercontinent Rodinia. New detrital zircon U–Pb ages and geochemical data acquired from quartz schists and spatially associated granites in the Tugerming anticline along the northern margin of the Tarim Craton have revealed Cryogenian ages, as opposed to Early Neoproterozoic and older ages as reported in previous studies. Granitic intrusions are dated at 656–637 Ma, which involved remelting of the ancient crust following the decline of the initial (Cryogenian) rift stage. They are unconformably overlain by terrestrial clastic deposits. Based on the available detrital zircons from the Late Neoproterozoic sedimentary rock assemblages, we identify a major change in the provenance of the basinal strata at the end of the Cryogenian period. This inferred provenance change, associated with basement exhumation, overlaps in time with resumed magmatic activities, basin inversion and uplift along the northern margin of the craton. The initial, Cryogenian rifting stage was facilitated by pure shear deformation that produced rift basins in and across the Tarim Craton. The subsequent rifting stage was facilitated by simple shear deformation, confined to the northern edge of the craton as the break-up of the supercontinent Rodinia further progressed. Episodic rifting of the Tarim Craton and its separation from Rodinia were aided by thermal weakening of its lithosphere owing to the periodic impingement of mantle upwelling beneath it throughout the Cryogenian and Ediacaran periods.

Seismic geomorphology and reservoir conditions of a Middle Miocene submarine channel system in the Taranaki basin, New Zealand

Deepwater channels function as vital deep-sea hydrocarbon reservoirs and as major routes for moving terrestrial clastic sediment to deepwater environments. A high-resolution sequence stratigraphic framework was built for the deepwater area of the Taranaki Basin using high-resolution three-dimensional (3D) seismic data, and various seismic interpretation techniques, including seismic attribute analysis, were applied. The principal controlling factors and petroleum development potential of the Middle-Miocene channel system were investigated with sequence stratigraphy and seismic geomorphology. Four understandings were primarily attained in this study: (1) depending on the different levels of the channel surfaces, the channel system can be divided into five sedimentary units (SU1-SU5), which correspond to the five stages of channel system evolution. These surfaces include one primary draping surface (PDS), five secondary channel erosion surfaces (SCES), and several tertiary channel erosion surfaces (TCES). (2) with the use of seismic facies analysis, six sedimentary elements were identified in the channel system: pelagic deposits (PDs), mass transport deposits (MTDs), outer levee complex (OLC), inner levee and terrace complex (ILTC), and turbidite channel complexes (TCCs). (3) The sedimentary evolution of the channel system was jointly influenced by multiple factors. The sediment supply and submarine geomorphology can directly affect the internal stacking and migration patterns of the channel. In contrast, tectonic activity and relative sea level fluctuations can indirectly affect the sedimentary characteristics of the channel by regulating the components and scale of clastic sediment. (4) SU1, SU2, and SU3 are primarily filled with coarse-grained sediments, which can serve as high-quality hydrocarbon reservoirs. In contrast, SU4 and SU5 can serve as regional cap rocks because they are filled with fine-grained sediments, and the overall channel system can represent a potential hydrocarbon reservoir-cap combination, which can be viewed as a significant research target for upcoming deepwater exploration. Clarifying the sedimentary properties and primary controlling factors at the various evolutionary stages of deepwater channels is vital for predicting the hydrocarbon development potential of the basin and reducing the drilling risk. This also helps with the development of deepwater basins with similar sedimentary environments in New Zealand and elsewhere in the world.

Discovery of the Hailin impact crater in northeast China

A uniquely shaped impact structure, the Hailin impact crater, has been discovered in northeast China. The crater was formed on a granodiorite hillside and is an oval depression with asymmetric rim height and a maximum diameter of 1360 m. The bottom of the crater is filled by Quaternary sediments with large amounts of rock fragments underneath. The discovery of quartz planar deformation features in rock clasts on the crater floor provides diagnostic evidence for the impact origin of the structure. The shape of the crater is largely due to the impact having occurred on a ridge terrain. The impact event probably occurred in the late Cenozoic Era. The Hailin impact crater is the fourth confirmed Chinese impact crater.

Late Cretaceous glaciations in a hyper-arid plateau desert of the South China Coastal Mountains

Increasing evidence indicates the existence of a cryosphere during the Cretaceous supergreenhouse. However, current understanding of a potential link between lithosphere dynamics and cryospheric processes in the Cretaceous plateau desert successions of China remains limited. We report the occurrence of ice-rafted dropstones and diamictites from the Upper Cretaceous Chishan Formation of the Subei Basin at the East Asian continental margin. Our provenance results indicate that fluvial deposits of the Lower Chishan Formation were mainly derived from the Sulu Orogen to the north and the Zhangbaling Uplift to the west, whereas aeolian deposits of the Upper Chishan Formation were largely recycled from the two sources with an additionally notable contribution from the post-Cretaceous basement of the Yangtze Block. Combined with previous evidence, provenance analysis indicates that Late Cretaceous collision between the Okhotomorsk Block and the East Asian continent led to the growth of the South China Coastal Mountains via crustal thickening, which generated an arid, high-altitude basin region that experienced desertification and paleohydrological variability, and that was supplied with additional clastic sediment sources from the basement of the South China Block. Our results provide evidence of Late Cretaceous cryospheric processes in a continental mid-latitude plateau desert linked to the northwestward subduction and collision of the paleo-Pacific realm. Global cooling from the late Turonian to Maastrichtian drove the establishment of glaciers in high-altitude mountains leading to the development of ice-related deposits in the plateau deserts, as recorded in the Subei desert basin of the South China Coastal Mountains. The record of ice-rafted debris and the provenance signature reveal an active Cretaceous plateau cryosphere linked to lithosphere dynamics.

Lithological Controls on Soil Aggregates and Minerals Regulate Microbial Carbon Use Efficiency and Necromass Stability.

Microbial carbon (C) use efficiency (CUE) drives soil C formation, while physical-chemical protection stabilizes subsequent microbial necromass, both shaped by soil aggregates and minerals. Soils inherit many properties from the parent material, yet the influence of lithology and associated soil geochemistry on microbial CUE and necromass stabilization remains unknow. Here, we quantified microbial CUE in well-aggregated bulk soils and crushed aggregates, as well as microbial necromass in bulk soils and the mineral-associated organic matter fraction, originating from carbonate-containing (karst) and carbonate-free (clastic rock, nonkarst) parent materials along a broad climatic gradient. We found that aggregate crushing significantly increased microbial CUE in both karst and nonkarst soils. Additionally, compared to nonkarst soils, calcium-rich karst soils increased macroaggregate stability and decreased the ratio of oligotrophic to copiotrophic microbial taxa, leading to a reduction in microbial CUE. Moreover, microbial CUE was negatively associated with iron (hydr)oxides in karst soils, attributed to the greater abundance of iron (hydr)oxides and higher soil pH. Despite the negative effects of soil aggregation and minerals on microbial CUE, particularly in karst soils, these soils concurrently showed greater microbial necromass stability through organo-mineral associations compared to nonkarst soils. Consequently, (i) bedrock lithology mediates the effects of aggregates and minerals on microbial CUE and necromass stability; and (ii) balancing minerals' dual roles in diminishing microbial CUE and enhancing microbial necromass stability is vital for optimizing soil C preservation.

Microbial mats writing the fossil record of true substrates in clastic rock successions

True substrates are bedding surfaces that represent the original environmental surfaces that existed at the time of burial. In the clastic depositional regime, there are abiotic and biotic causes that may contribute to the formation of such true substrates. This paper focuses on how sediment-stabilizing microbial mats may increase the preservation potential of true substrates. Baffling and trapping enrich fine-grained particles and heavy minerals in mat textures inducing a layer of heterogeneity in the otherwise homogenous deposits. Together with in situ mineral precipitation during the life time of the microbial mat and post-depositional diagenesis, baffling and trapping contributes to processes leading to bedding plane preservation. Microbial mats interact with the hydrological system of a coastal environment causing typical microbially induced sedimentary structures (MISS). The morphologies of MISS can indicate climate seasonality and zone of the respective true substrate. The interaction of animals and plants with microbial mats allow reconstructing events that took place during the exposure of the original environmental surface. Finally, true substrates displaying MISS are well-defined indicators for life exploration of Earth's oldest sedimentary rock successions and equivalent lithologies on other planets.

Holocene history of Fiskesø, Prinsesse Ingeborg Halvø, eastern North Greenland

Sediment cores up to 92 cm in length were recovered with gravity and Russian peat corers from Fiskesø, Prinsesse Ingeborg Halvø, eastern North Greenland, during the summer 2014. The correlated sediment succession consists of clastic sediments that are interspersed in the upper part with layers of organic material and likely record the environmental history of the lake since deglaciation. The paucity of macrofossil remains hampered radiocarbon dating of the sediments from Fiskesø. According to published data, the deglaciation of the region took place c. 10 cal. ka BP. Relative sea-level reconstructions from the region suggest that the Fiskesø basin, which is today located at 33 m above sea level, was characterised by marine conditions until c. 8.1 cal. ka BP. Marine fossils in the lower part of the sediment succession support the prevalence of marine conditions. A reliable radiocarbon age from 5 cm above the isolation horizon in Fiskesø sediments indicates an age of 6.1 cal. ka BP and supports the isolation of the basin prior to this time. Cooling is indicated in the upper part of the sediment succession and is reported to have taken place in the region stepwise shortly after 6.1 cal. ka BP and at c. 4.5–4.0 cal. ka BP. Despite the poor chronology the data from Fiskesø support existing terrestrial and marine reconstructions from the region.

High-resolution cyclic framework for the Songliao Basin in northeastern China, and its implications for sedimentation and organic matter enrichment

The study of fine-grained sedimentation has consistently concentrated on investigating the mechanisms and principles governing the enrichment of organic matter. However, the lack of unified stratigraphic framework has always existed as fine-grained sedimentation covers two distinct grain-size grades, namely, mud and silt, which has impeded the progress of subsequent production research. This study exemplified this issue by analyzing the first member of the Qingshankou Formation in the southern Songliao Basin. We established reconstructed gamma and density curves that mitigated filter noise interference, integrated high-resolution sequence results with astronomical cycle divisions, and created a high-frequency isochronous stratigraphic framework for clastic fine-grained sedimentation by leveraging the weak sensitivity of sandstone density curves and the robust stability in eccentricity cycle extraction. This approach addresses the inconsistencies in stratigraphic division methodologies and mismatched outcomes stemming from the use varying techniques to delineate mud and silt components within clastic fine-grained sedimentary sequences. Furthermore, it elucidates how tectonic-scale variations in sediment supply coupled with potential accommodation changes dictate macroscopic stacking patterns within strata, whereas climate fluctuations on orbital time scales govern sand-mud progradation degrees within these layers, culminating in periodic rhythmic characteristics characterized by vertical sand-mud interbedding. A model for stratigraphic development pertaining to lake delta systems constrained by a “synchronous heterotopy” paradigm is proposed for the southern Songliao Basin. The organic matter enrichment pattern aligns with its filling dynamics, indicating an “overfilling” type developmental pattern at lower strata levels where organic material predominantly originates from terrestrial plant debris external to the basin; this material accumulates primarily within silty zones along layers—with areas exhibiting heightened enrichment values slightly lagging behind short-eccentric maxima positions. In contrast, under an upper “balanced filling” type developmental framework, sources of organic matter are derived both internally and externally relative to the basin—exhibiting substantial heterogeneity—and regions marked by elevated organic matter concentrations are directly associated with locations identified as short-eccentric maxima.

Lithogeochemistry of Upper Precambrian terrigenous rocks of Belarus. Communication 2. Provenance, paleogeodynamics, paleogeography, paleoclimate

This publication completes the consideration of the lithogeochemical features study of a pilot collection of the Riphean and the Vendian sandstones, siltstones and mudstones (last one identified based on the interpretation results) of the Belarus. Data on the age of detrital zircon published in recent years suggest that the source rocks for the Upper Precambrian deposits of this region were the Osnitsk-Mikashevichi and the Trans-Scandinavian igneous belts, the Volyn-Brest large igneous province, rapakivi granites, as well as various associations of rocks of Sarmatia, the Danopolonian orogen and Svecofennides. The distribution of clastic rocks data points of our collection on provenance, paleogeodynamic, paleogeographic and paleoclimatic discriminant diagrams, which based mainly on the lithogeochemical composition, allows us to draw a number of conclusions. We are considering that the Riphean and the Vendian strata of the Belarus are composed mainly of intraplate granitoids erosion products, as well as various felsic igneous rocks of island-arc and syncollisional genesis. The part of mafic rocks erosion products among them generally does not exceed 30%. It`s noticeable mainly in rocks of the Volyn series (products of the Volyn-Brest large igneous province erosion), as well as in some samples of the Nizov, Selyavy and Kotlin formations (fragments of mafic rocks from other sources?). Source to sink transporting was carried out mainly by large rivers. Paleogeodynamic settings varied from quite active to quite passive. The paleoclimate in the Riphean was most likely arid/semiarid, and in the Vendian it was humid, from subtropical in the early (except for the Glussk Formation) to tropical in the Late Vendian. The research results also make it possible to show some work features for known paleoclimate reconstruction methods and techniques.

Lake sediments on the Adamawa Plateau (Central Cameroon) as archives of climate change and the Bantu impact during the last 4000 years BP

AbstractThis study investigates Late Holocene environmental changes in Central Cameroon induced by the combined effects of climate and human impact. For this purpose, sediments from lakes Dang, Massote, Fonjak and Ngaoundaba were studied through lithologic analysis including mineralogical composition and organic geochemistry combined with radiocarbon dates. From these analyses, the sediments at the base of lakes Massote and Dang cores are respectively dated to 4680–3530 and 4220–3580 cal yr BP, whereas the sediments of lakes Fonjak and Ngaoundaba seem to be younger, respectively dated to 3210–3000 and 1870–1740 cal yr BP. Lake sedimentation is dominated by organic matter (OM) poor deposits (OM < 3%) in the lower sections and OM-rich deposits (OM: 5–54%) in the upper sections. This shift from OM-poor to OM-rich sedimentation induced by climate variations occurred at $$\sim $$ ∼ 2800–2400 cal yr BP. The mineral assemblage is predominantly composed of kaolinite with minor contributions from chlorite, smectite, chlorite/smectite, illite/smectite, quartz, K-feldspar, gibbsite, plagioclase, siderite, hematite and goethite. These sediments are clastic, except for Lake Fonjak core sediments which correspond to peat intercalated with carbonate clay and clastic deposits. Age-depth models suggest that the sedimentation rate was 0.2 mm yr-1 for lakes Dang and Massote before $$\sim $$ ∼ 690–560 cal yr BP and $$\sim $$ ∼ 660–470 cal yr BP, respectively. Thereafter, it increased to 0.8 mm yr-1 in Lake Dang and 0.7 mm yr-1 in Lake Massote. Finally, Late Holocene environment changes in Central Cameroon consisted of the shift of open water lakes to marshy fringes with abundant vegetation induced by human activities and facilitated by increasing seasonality.

Sediment load with metallurgical slag admixture under diverse morphological conditions along submerging karst stream

This study investigates the clastic fluvial sediments of the Jedovnický submerging stream in the section between the Jedovnice village and Křtinský stream (Moravian Karst, Czechia). A total of 28 samples were collected to analyze clast composition, slag content, grain size, and roundness. The sediment primarily consists of allochthonous Lower Carboniferous material (greywackes, clayey shales) with varying amounts of metallurgical slag, occasionally mixed with autochthonous deposits such as rockfall accumulations and tailings from the excavation of connecting adits. The slag content fluctuates, peaking downstream of the erosive section of the Rudické propadání cave, near the Stará řeka passage connection. Grain size distribution is influenced by both surface and cave morphology, as well as hydraulic conditions. The alternation between erosive and depositional zones, along with the unique karstic and speleorelief features, plays a crucial role in clast mobilization. These features include ponors, erosive and paragenetic corridors, sumps, and rockfalls. Fine particle accumulations are particularly noticeable in front of sumps or dams. Throughout the studied section, the proportion of coarse particles (>10 mm and 5–10 mm) gradually decreases, while finer particle content increases toward the resurgence. The roundness of Carboniferous sediments remains relatively constant, although it is significantly influenced by the presence of well-rounded, weak and ductile slag clasts. Overall, both the slag content and the proportion of well-rounded and rounded clasts in the coarser fractions (>10 mm and 5–10 mm) show a decreasing trend toward the resurgence.

Rifting Basins at the Accretion-Collision Stage of Fold Belt Development: Eastern Slope of the Southern and Middle Urals in the Carboniferous

Research subject. Sedimentary basins within the Mississippian and Early Pennsylvanian (Middle Carboniferous of Russia) rift (sensu lato) structures on the eastern slope of the Southern and Middle Urals. Methods. An analysis of lithological characteristics of sedimentary rocks and relationships with volcanic complexes in order to clarify the evolution of rifting basins. Results. During the Mississippian and Early Pennsylvanian, several large rifting basins were common in this area. The Early Carboniferous rifting basins (Magnitogorsk-Bogdanovskoe graben and Alapaevsk-Kamensk rift) of accretionary margin of the East European craton were characterized by relatively shallow-water (in some places up to coastal-marine and continental) environments, caused by intensive (compensatory) filling of depressions with sedimentary material. In this case, volcanic rocks – those of fissure-type and stratovolcanoes lava flows – also played a significant role. In the Late Visean, the rifting process paused; a relatively shallow shelf basin regime was established throughout the entire area, which persisted until the end of the Early Carboniferous. In the Early Pennsylvanian, due to a hard oblique collision, the rifting process resumed. However, the rifting basins were already smaller in terms of area and most often deeper, whereas the occurring volcanic processes were less intensive. The characteristic feature of these basins was the presence of flysch complexes. The elongated shape of the rifting basins, large thicknesses of sedimentary strata, lateral facies variability, and the abundance of coarse clastic rocks, consisting largely of fragments of directly underlying sediments (Visean, Serpukhovian, Bashkirian), suggest that the Mississippian and Early Pennsylvanian rifts of the Southern and Middle Urals eastern slope had a strike-slip nature, i.e., the rifting basins were pull-apart type depressions.

Deeply buried clastic rock diagenesis evolution mechanism of Dongdaohaizi sag in the center of Junggar fault basin, Northwest China

Abstract To reveal the diagenetic sequence of reservoir rocks in the central part of the deep depression basin, the Wuerhe Formation in Junggar Basin was taken as an example to conduct the detailed studies on its sedimentary facies, diagenetic sequence, and the micropore structure evolution rules based on the comprehensive data from a super deep exploration well C-6 (approximately 7,000 m in depth). First, an arid environment fan delta sedimentary model of the Wuerhe Formation was established, and its sedimentary evolution law was clarified as a gradual transition from a fan delta front to a fan delta plain during the water-regression process until the lake dried up. Then, the diagenesis types and evolution sequence of the Wuerhe Formation, and the influence degrees of the compaction, cementation, and dissolution on the rock formation process were clarified. Finally, the diagenesis and pore evolution model was established, and the greatest impact factors of the late reservoir densification were clarified. Based on this research, the diagenesis and pore evolution processes of the deep rocks in the studied deep central sag were ultimately revealed to provide useful guidance for the deeply buried oil and gas reservoir exploration.

Comparison of neotectonic intermontane basins of Northern Armenia and Eastern Türkiye

The results of comparative analysis of the structure and history of the Neogene-Quaternary development of 18 inrermontane basins in Northern Armenia and Eastern Türkiye are presented. The research is based on expeditionary work carried out by the authors in 2012–2023, and supplemented by published materials from other researchers. Palaeontological, magnetostratigraphic and radioisotope data on the stratigraphy of the basins are analyzed. The comparison made it possible to identify four stages of basin development, expressed by the nature of sedimentation: (i) marine sedimentation; (ii) predominantly lacustrine accumulation of fine-grained clastic material transported from low uplifts; (iii) lacustrine-alluvial sedimentation with a significant proportion of coarse material carried down from neighboring uplifts: (iv) involvement of the basins in the total rise of the region, which in most depressions is expressed by increased incision of watercourses into previously emerged landforms, and in the Sevan depression is combined with ongoing lacustrine-alluvial sedimentation. A consistent rejuvenation of stages (i)–(iii) of the basin development in the northern direction is revealed. It is caused with the growth and expansion to the north of the uplift of the Taurus Ridge in the process of its thrusting onto the Arabian Plate. At the same time, the development of the basins revealed the impact of tectonic events in the Middle and South Caspian. It was expressed in the Early Pliocene by the unconformity and the appearance of coarse clastic rocks, reflecting the increasing contrast of vertical movements between the Caucasian and Caspian regions, and at the end of the Late Pliocene by the penetration of waters of the Akchagylian transgression of the Caspian Sea into some basins. These features of the development of the basins did not depend on differences in their origin, which was determined by the influence of several factors. Among them, the main ones were movements on faults as a result of the interaction of lithospheric blocks and subsidence, caused by movements of sublithospheric masses, expressed by volcanism. Secondary roles were played by the behavior of the ophiolitic substrate and the tectono-volcanic damming of river valleys.

Diagenetic History and Biosignature Preservation Potential of Fine‐Grained Rocks at Hogwallow Flats, Jezero Crater, Mars

AbstractThe Mars 2020 Perseverance rover discovered fine‐grained clastic sedimentary rocks in the “Hogwallow Flats” member of the “Shenandoah” formation at Jezero crater, Mars. The Hogwallow Flats member shows evidence of multiple phases of diagenesis including Fe/Mg‐sulfate‐rich (20–30 wt. %) outcrop transitioning downward into red‐purple‐gray mottled outcrop, Fe/Mg clay minerals and oxides, putative concretions, occasional Ca sulfate‐filled fractures, and variable redox state over small (cm) spatial scales. This work uses Mastcam‐Z and SuperCam instrument data to characterize and interpret the sedimentary facies, mineralogy and diagenetic features of the Hogwallow Flats member. The lateral continuity of bedrock similar in tone and morphology to Hogwallow Flats that occurs over several km within the western Jezero sedimentary fan suggests widespread deposition in a lacustrine or alluvial floodplain setting. Following deposition, sediments interacted with multiple fluids of variable redox state and salinity under habitable conditions. Three drilled sample cores were collected from this interval of the Shenandoah formation as part of the Mars Sample Return campaign. These samples have very high potential to preserve organic compounds and biosignatures. Drill cores may partially include dark‐toned mottled outcrop that lies directly below light‐toned, sulfate‐cemented outcrop. This facies may represent some of the least oxidized material observed at this interval of the Shenandoah formation. This work reconstructs the diagenetic history of the Hogwallow Flats member and discusses implications for biosignature preservation in rock samples for possible return to Earth.

The influence of syn‐depositional compaction on clastic sediment distribution in river‐dominated deltas: A modelling study

AbstractSyn‐sedimentary compaction or consolidation is an important process in deltaic environments because it affects both the local morphodynamics and hydrodynamics as well as the delta‐scale accommodation space. However, the impact of syn‐depositional compaction on the sediment distribution and the interdependency between different delta areas related to the sediment budget are not fully understood. This paper simulates syn‐depositional compaction using improved 1D grain‐size compaction formulations, integrated into hydrodynamic and morphodynamic modelling software Delft3D. The updated code is used to model sedimentation in mud‐rich deltas under various compaction rate scenarios, which represents the maximum compaction rate potential of sediment that experiences the highest overburden stress in the delta. The simulated deltas are analysed by first classifying their plan‐view area development into depositional elements: distributary channel, underfilled channel, delta plain, mouth bar, delta front and pro delta depositional elements. Then, sedimentation by mass, accommodation space and depositional segment metrics are calculated using the interpreted depositional elements. The results for zero compaction rate scenarios (0 mm year−1) show that limited space‐varying and temporal‐varying accommodation is available to deposit sediment in the delta plain depositional element. Therefore, the sedimentation mainly occurs in the mouth bar depositional element. For low‐mid compaction rate scenarios (0.01–1 mm year−1), the additional syn‐depositional accommodation space in the delta plain depositional element increases sedimentation in this area, limiting sedimentation in the mouth bar depositional element. For high compaction rate scenarios (>1 mm year−1), a further increase in the accommodation space in the delta plain depositional element leads to lateral sedimentation attributed to channel relocation, where the sedimentation mainly occurs in the mouth bar depositional element. This study shows that, although considered a gradual process, syn‐sedimentary compaction does impact long‐term delta evolution by influencing the distribution of sedimentation in the delta.