The present paper is the second article in a series of publications dedicated to the upper Mesozoic stratigraphy of Sikhote-Alin (Russian Far East) and northeastern China. The Barremian–Albian ...stratigraphy of Sikhote-Alin and northeastern China is reviewed and a correlation scheme between these regions is proposed. Barremian–Albian rocks in Sikhote-Alin are mainly represented by marine deposits. Non-marine deposits occur in the south of Sikhote-Alin in the Partizansk and Razdolny basins. In northeastern China, in contrast, the Barremian–Albian rocks are mainly non-marine often intercalated with volcanic rocks. Non-marine deposits alternating with marine ones occur in northeastern Heilongjiang near the border with Russia. They fill a system of sedimentary basins restricted to the Dunhua-Mishan Fault Zone and linked in the east with the Alchan Basin of Sikhote-Alin. The deposits of these basins, represented by the Jixi, Longzhaogou, Dajiashan and Huashan groups, and the Assikaevka and Alchan formations, are of high importance for non-marine and marine correlation because they contain non-marine fauna and flora assemblages together with marine molluscs. The range of the Jixi and Longzhaogou groups is clarified based on the correlation with the Assikaevka Formation containing marine index fossils and is considered here as Barremian (possibly extending to Hauterivian)–middle Albian. The Jixi Group yielding elements of the Jehol Biota corresponds to the Jehol Group, and, therefore, the range of the Jehol Group is also considered as Barremian–middle Albian.
•Reviewed Barremian–Albian stratigraphy of Sikhote-Alin and northeastern China.•Correlation scheme for the Barremian–Albian of Sikhote-Alin and northeastern China.•The time of Early Cretaceous transgressions in northeastern China is clarified.
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This book provides a comprehensive, self-contained introduction to one of the most exciting frontiers in astrophysics today: the quest to understand how the oldest and most distant galaxies in our ...universe first formed. Until now, most research on this question has been theoretical, but the next few years will bring about a new generation of large telescopes that promise to supply a flood of data about the infant universe during its first billion years after the big bang. This book bridges the gap between theory and observation. It is an invaluable reference for students and researchers on early galaxies.
The First Galaxies in the Universestarts from basic physical principles before moving on to more advanced material. Topics include the gravitational growth of structure, the intergalactic medium, the formation and evolution of the first stars and black holes, feedback and galaxy evolution, reionization, 21-cm cosmology, and more.
Provides a comprehensive introduction to this exciting frontier in astrophysicsBegins from first principlesCovers advanced topics such as the first stars and 21-cm cosmologyPrepares students for research using the next generation of large telescopesDiscusses many open questions to be explored in the coming decade
Late Paleozoic to early Mesozoic floras are well represented in Chile by several continental fossiliferous outcrops across the country. The oldest floras are Late Devonian in age, and they are mostly ...located in northern Chile (e.g., El Toco, Arrayán, Las Placetas formations) and are dominated by herbaceous lycopsids. In turn, Middle to Late Triassic floras are widely distributed throughout Chile (e.g., Mamiña, La Ternera, San Felix, Las Breas, El Puquén, Santa Juana, and Panguipulli formations), and are characterized by typical Triassic Gondwanan taxa, such as the ferns Asterotheca, Cladophlebis and Dictyophyllum; the sphenophyte Neocalamites; the corystosperm Dicroidium; the cycadophytes Pterophyllum, and Pseudoctenis; the ginkgophytes Baiera, Sphenobaiera and Ginkgoites; the conifer Heidiphyllum, and gymnosperms of uncertain affinities (i.e., Linguifolium and Taeniopteris). Lycophytes are hitherto unknown in the Chilean Triassic macrofloras. A single fossil locality has been regarded tentatively as Early Triassic in age based on palynomorphs. Most of the Devonian to Triassic plants found in Chile are preserved as impressions, lacking organic matter. However, some adpression plant fossils and palynomorphs have also been found. Fossil woods have been reported from several Triassic sediments of Chile, especially in the northern part of the country. The plant fossil record from Chile is relevant for understanding the dynamics and evolution of the late Paleozoic to early Mesozoic vegetation in the southwestern edge of Gondwana. This contribution provides a general framework that will support future and more detailed paleobotanical studies in Chile. Lastly, this work intents to motivate new generations of paleobotanists in Chile.
•Late Paleozoic to early Mesozoic floras are well represented in Chile.•Devonian floras are dominated by herbaceous lycopsids.•Typical elements of the Dicroidium-flora dominated the Triassic plant communities.•There is a great potential for future paleobotanical studies in Chile.
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4.
Fold formation in Kurdish Zagros (N Iraq) Csontos, L.; Szabó, M. Forián-; Pocsai, T. ...
Marine and petroleum geology,
December 2022, 2022-12-00, Volume:
146
Journal Article
Peer reviewed
Analysis of seismic sections and wells near the frontal folds of Iraqi Kurdistan (Low- and Highly folded zone) document the interplay of folds, faults and possible mechanisms of their generation.
...Serial sections from 3D seismic volume in the Low folded zone are interpreted based on calibration wells. Sections display fold evolution from low amplitude kinked monocline to high amplitude ramp folding. The fold continues towards the exposed Safeen anticline with a subvertical limb. These lowland sections can also be considered as the lateral growth segment of Safeen anticline.
Three geoseismic sections through frontal folds were constructed with variable quality seismic and dips, formation tops from surface and from mountains wells. These sections show tight anticlines with thrust faults cutting to near surface on both limbs; remnant normal faults; a subvertical southern limb crossed by flat thrusts; and a Triassic ductile core.
Sections suggest that this part of Zagros is built of two ‘rigid’ units: an upper, Mesozoic-Neogene and a lower, Paleozoic one, separated by a ductile detachment along the lower Triassic. The upper unit is prone to folding and faulting, the lower one to faulting. The detachment in-between comprises the Kurrachine C, lower Triassic Beduh and Mirga Mir formations, and potentially the top members of Permian Chia Zairi formation. Detachment is possibly dominated by evaporites. Our detachment is thicker than only Beduh-Mirga Mir detachment proposed by recent reconstructions of others.
Folds are initiated as detachment folds above thickened parts of the Lower Triassic, then evolve into ramp folds. Ramp is formed by the merger of flat thrusts with pre-existing steep earlier normal faults that affect the Mesozoic section. Shear and drag beneath these ramps lead to steepening of the southern limb and to fault propagation. A basal flat thrust is the final element of this fault propagation stage. Underlying rigid Paleozoic can form imbricates that push the Triassic detachment upwards, creating passive folds. These Paleozoic imbricates dip to the south and not to the north, as suggested by reconstructions of others. Finally, strike slip shear documented at outcrops also contributes to the final fold form.
Own and others' surface geological observations, indications from seismic and radiometric data suggest that fold generation started in Late Cretaceous, continued in the Paleogene in internal Highly folded zone. In our study area only Late Neogene fold growth can be documented, which is in harmony with 5–8 Ma uplift dates of others. Others’ geomorphologic work suggests fold lateral growth is a quick process. We propose that regional folds, such as Safeen anticline grow in distinct short periods separated by longer quiet intervals.
•Seismic sections across the Low folded zone and three geoseismic sections across the frontal Highly folded Zagros display different fold styles.•Fold forms range from kink-like, though box-fold, rounded ramp-fold to tight fold forms with overturned southern limb with flat thrusts.•Faults results from the merger of flat thrusts in a lower Triassic detachment and high angle former normal faults in their Mesozoic cover.•Folds evolve from detachment fold, through ramp fold, then fault-propagation fold to produce the fold style observed in the mountains.•The different structural styles can be also viewed as a sequence of lateral fold propagation during the main Late Neogene shortening period.
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Surface geology, well data and 2D seismic interpretations reveal the presence of triangle zone structures at the contact of the Subandean Ranges and the Amazonian foreland in Peru. From north to ...south the Santiago, Marañon, Ucayali and Madre de Dios basins have been studied. Interpretations presented in this study show a great variety of structural styles at this contact area. Simple triangle zones with one back thrust, composite ones with several back thrusts, more complex double vergent ones with pop-up structures, best described as fish-tails, tectonic wedges and passive-roof duplexes are present in the study area. The role of pre-Andean tectonics and paleogeography is key to understanding the Andean evolution, due to the control on the location and geometry of the main detachment levels. The Santiago Basin is characterized by the presence of fish-tail structures with a Permian-Triassic evaporitic basal detachment located at the base of the Pucara Gr. At the Ucayali Basin, several detachment levels interact, the basal ones located within the Ordovician, Devonian, and Carboniferous defining triangle zones or tectonic wedges. At the Madre de Dios Basin, two detachment levels define the base of the triangle zone, Permian shales in the northwest at the Inambari Imbricates area, and Lower Devonian (Cabanillas Gr.) in the southeast at the Candamo area. A roof thrust is located within the Paleogene section at both the Madre de Dios and Ucayali basins, defining passive-roof duplex structures.
Several detachment levels are rooted into the Lower Paleozoic; others within the Permian-Triassic section, being locally evaporitic, and finally others are located at the base of the Cretaceous. Paleozoic shales represent the main basal detachment level of the southern Subandean ranges. The role of these detachments and the role of the sedimentation rate are discussed as factors that control the development and geometry of the triangle zones described in the study area.
Except for the San Martin-Sagari area of the Ucayali Basin, the triangle zones of the Santiago and Madre de Dios basins remain unexplored even though active petroleum systems are present. Sub-thrust structures at the Azulmayo area of the Madre de Dios Basin remain promising undrilled structures.
•From north to south, the structure of the Subandean Ranges of the Peruvian Andes, that is the Santiago, Marañon, Ucayali and Madre de Dios Basins has been described using surface geological maps and cross-sections, well logs and 2D seismic data.•Triangle zones develop at the contact between the east-vergent Paleozoic-Mesozoic imbricates/duplex of the Andes foothills with the Amazonian foreland basin.•The main detachment varies from Lower Paleozoic, Permian and Cretaceous shale strata, being Permian-Triassic evaporites at the Santiago Basin. Tectonic activity developed from Cretaceous to Quaternary time.•The structural style is very variable from basin to basin and consists of simple (one back thrust) to composite triangle zones (with associated pop-up structures or multiple back thrusts), best described as fish-tails, tectonic wedges or passive-roof duplexes.•The role of detachment levels and sediment loading and rate, specially of syn-orogenic growth strata, will be discussed to explain the development of triangle zones in the study area.
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While most ocean-island volcanism is effusive, recent evidence has demonstrated that intraplate ocean island volcanoes can exhibit protracted explosive histories, with catastrophic eruption styles ...and hazardous behaviour more typically associated with volcanoes in continental and plate-margin settings. Tenerife is the largest explosive ocean-island volcano on Earth, with a prolonged (∼2 Ma) post-erosional history of caldera-forming, plinian and ignimbrite eruptions of evolved composition. The 0.7–1.8 Ma succession with 20 newly defined formations is reported for southern Tenerife, Canary Islands. In the last 2 Myr, the Las Cañadas volcano has produced >42 pumice-fall eruptions, 21 with extensive ignimbrites, and 12 inferred caldera collapse events. Pyroclastic density currents have repeatedly travelled more than15 km from source to the ocean, filling valleys and burying extensive interfluves. A robust whole-rock chemistry dataset, selected mineral chemistry, coupled with new 40Ar/39Ar ages of units through the pyroclastic stratigraphy, allow recognition of magmatic trends within the system on the order of 100 ky. The catastrophic explosive eruptions form three, 0.2–0.5 Myr-duration clusters (the Ucanca, Guajara and Diego-Hernandez) that do not appear to correspond simply with geochemical cycles, or to cycles of increasing eruption size or explosivity as has been previously proposed. During the clusters, large eruption frequencies averaged 1 every 20–45 kyrs. The eruption clusters were separated by hiatuses of ∼240–260 kyr, recorded by soils and unconformities, and may reflect marked changes in geographic dispersals following giant landslide breaches in Las Cañadas caldera wall. Two concurrent evolutionary magmatic trends are distinguished: one producing crystal-rich magmas, the other formed the cooler crystal-poor magmas: both spanned over a million years until 0.66 Ma, when the former ceased.
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•The 0.7–1.8 Ma pyroclastic succession with 20 newly defined formations is reported for southern Tenerife.•Pyroclastic density currents have repeatedly travelled >15 km from source to the ocean.•Numerous pumice-fall deposits have been identified and characterised.•Caldera collapse events occurred possibly in 5 ignimbrite-forming eruptions.•Whole-rock and mineral chemistry dataset, and new 40Ar/39Ar ages, allow recognition of magmatic trends.•Three explosive eruption clusters have been identified, with eruption frequencies averaged 1 every 20–45 kyr.
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Research on the static connectivity of reservoirs is of great significance for predicting the lateral continuity of sandstone bodies and determining the field development strategy. The main impacts ...of static connectivity are geometry, stacking pattern and distribution of fluvial sandstone bodies, which are controlled by changes in base level. This study addresses the static connectivity of fluvial sandstones of the Yangdachegnzy reservoir in the Yushulin oilfield with a dense network of wells. The Yangdachengzy reservoir develops a long-term depositional cycle (a third-level sequence) consisting of 3 mid-term depositional cycles (MDC1-MDC3) and 21 short-term depositional cycles (SDC1-21). Sedimentary facies maps of each stratigraphic intervals in the Yangdachengzy reservoir that are constrained to high well density from the Yushulin Oilfield exhibit: (i) as base-level falls, the planform style of sandstone bodies changes from isolated type to amalgamated type; (ii) how static connectivity evolves through base-level fluctuations and show how static connectivity is sensitive to the net-to-gross ratio and well spacing. The analyses show that the relationship between the net-to-gross ratio and static connectivity exhibits a sigmoid curve. Such a curve is sensitive to the well spacing and the planform style of sandstone bodies. When well spacing increases, the S-curve shifts to the right, with a narrow “cascade zone” and a relatively higher percolation threshold of net-to-gross ratio (e.g., 0.2 at 150 m well spacing). When well spacing decreases, the S-curve tends to be linear, with a large range of “cascade zones” and a relatively lower percolation threshold of the net-to-gross ratio (e.g., 0.43 at 450 m well spacing). At a given net-to-gross ratio, amalgamated-type sandstone bodies that developed at the lowest base-level stage are very prone to reach the fully connected status (reservoir connected over 0.8) with a relatively low well density.
•A four-tier hierarchical scheme of fluvial reservoir was built by using densely drilled subsurface data.•Reveal how base-level variations control the sandbody architecture and static connectivity.•Results can be applied to guide the well emplacement in fluvial reservoirs.
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The Upper Ordovician Cincinnatian Series is a critical upper Katian reference succession. Previously, six 3rd-order depositional sequences (C1 to C6) have been recognized and frequently used as ...regional time slices. Recent research, however, indicates a need for revision and additions, including the recognition of additional 3rd- and 4th-order sequences. We propose amendments based upon high-resolution correlations using a combination of regional disconformities, cycle stacking patterns, bioevents, marker beds, and chemostratigraphy. Several disconformities, including a large regionally angular mid-Richmondian unconformity, are newly recognized or reinterpreted. In addition, distinctive depositional patterns aid in the recognition of systems tracts, with a) thick proximal laminated peritidal facies representing early transgressive systems tracts (TSTs) or lowstands, in part (LSTs), b) shell-rich limestone packages representing later TSTs and overlain by c) more shale-prone highstand systems tracts (HSTs), themselves overlain locally by d) siliciclastic dominated falling stage systems tract (FSST) deposits that are commonly removed beneath substantial unconformities (sequence boundaries). At present, we recognize eight 3rd-order Cincinnatian sequences, designated C1 through C8, and 16 4th-order subdivisions and their component systems tracts. A younger (Hirnantian?) sequence may be present at some localities as the enigmatic Centerville Formation and/or basal Belfast Member of the Brassfield Formation. The implications of these new correlations and sequence interpretations include a new standard for relative sea-level changes and insights into basin dynamics. This framework also permits a more nuanced history of biotic changes that include geologically brief pulses of immigration associated with the transgressions of the C1 (lower Kope Formation), C5C (Clarksville Member of Waynesville Formation), and C7A (basal Whitewater Formation).
•Synthesis of Upper Ordovician (Cincinnatian) litho- and biofacies patterns•Revised model of cratonic, mixed siliciclastic‑carbonate sequences presented•Existing sequence stratigraphic framework for the Cincinnatian is strongly revised.•New framework recognizes 8 third-order and more than 16 fourth order sequences.•Provides new insights into temporal patterns of physical and biotic events
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Salars with lithium-rich brines are a characteristic feature of the Central Andes, but knowledge about the main sources of lithium and the mobilization processes of lithium in the salar deposits is ...still incomplete. This work focuses especially on the Salar de Diablillos (southern Puna) as part of a larger area that includes the neighboring Salar Centenario and Salar de Ratones. Building on the ability of Li as a tracer of silicate weathering, we investigate the Li content and isotope composition of samples from the depocenter and catchment of the Diablillos basin (3-D) and conduct a surface reconnaissance in the Centenario and Ratones depocenters to identify the key metallogenic processes. Radiogenic Sr and Nd isotope compositions are also provided to discriminate the main local Li sources. The isotope data in all three depocenters show that most of the Li in the brines and evaporite deposits are derived from Cenozoic volcanic rocks, despite the dominance of the Paleozoic basement in the catchment. In the Centenario and Ratones depocenters, near-surface chemical weathering appears to be the dominant Li mobilization process. In contrast, hydrothermal mobilization of Li also plays a role in the Salar de Diablillos, possibly related to the presence of a fractured basement with pressure zones and artesian conditions in the aquifer at depth. These fluids also show a larger element contribution from the basement.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Paleozoic carbonate buried hills with burial depths of more than 4500 m (14,764 ft) in the Bozhong sag of the Bohai Bay Basin are rich in natural gas resources, categorized as typical ultradeep ...fracture-related reservoirs. Based on the data of (sidewall) cores, thin sections, electrical image logs, three-dimensional seismic observations, and physical properties, we evaluated the fracture characteristics and elucidated the dominant controls on effective (unfilled) fractures. Tectonic fractures are the main components in these reservoirs. The intersecting relationships, widths, and strikes of the fractures as well as the carbon and oxygen isotope ratios of the fill materials indicate that NWW- and NE-trending tectonic fractures developed. The NWW-trending fractures are related to the compressional tectonic stress field of the Indosinian orogeny and account for nearly 80% of the fractures, with widths ranging from 40 to 160 μm; 43% of them are filled with carbonate and quartz. The dissolution of meteoric water mainly occurred with this set of tectonic fractures and formed an upper dissolved zone within 200 m beneath the weathering crust. Related fill materials have −2‰ to 2‰ δ13C and −8‰ to −13‰ δ18O. The group of NE-trending fractures accounted for approximately 20% of all fractures, with widths ranging from 200 to 280 μm, and are related to the faulting during the Himalayan orogeny, which contributed to the formation of subsequent NE-trending fractures and reopened prior NWW-trending fractures. Some fill materials present negative δ13C and δ18O values, distributed from −2‰ to −6‰ and −13‰ to −20‰, respectively. These negative values revealed the influence of Cenozoic hydrothermal fluids and organic acids, which contributed to the development of an internal fracture-related dissolved zone that developed beneath 400–600 m from the top of the basement. The analysis demonstrates that the direction of in situ maximum principal stress is subparallel to the fracture trends, which is the key factor for maintaining the effectiveness of the fractures. The coupling of Cenozoic tectonic reactivation and multiple genetic fluids controls the effectiveness of ultradeep carbonate reservoirs.
•The NWW- and NE-trending fractures are related to the Indosinian and Himalayan orogenies.•The direction of in situ maximum principal stress is subparallel to the fracture trends, which maintains the fracture effectiveness.•Fracture fill materials break the cement seal and are reopened during the Cenozoic faulting events.•Multiple forms of genetic fluid dissolution can increase the porosity of fractured carbonate buried hills by nearly 14%.•New reservoir plays of deeply buried reservoirs are established under the coupling action of tectonic movements and fluids.
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