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1,959 result(s) for "lithostratigraphy"
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Late Miocene sedimentary record of the Danube/Kisalföld Basin: interregional correlation of depositional systems, stratigraphy and structural evolution
The Danube / Kisalföld Basin is the north-western sub-basin of the Pannonian Basin System. The lithostratigraphic subdivision of the several-km-thick Upper Miocene to Pliocene sedimentary succession related to Lake Pannon has been developed independently in Slovakia and Hungary. A study of the sedimentary formations across the entire basin led us to claim that these formations are identical or similar between the two basin parts to such an extent that their correlation is indeed a matter of nomenclature only. Nemčiňany corresponds to the Kálla Formation, representing locally derived coarse clastics along the basin margins (11- 9.5 Ma). The deep lacustrine sediments are collectively designated the Ivanka Formation in Slovakia, while in Hungary they are subdivided into Szák (fine-grained transgressive deposits above basement highs, 10.5 - 8.9 Ma), Endrőd (deep lacustrine marls, 11.6 -10 Ma), Szolnok (turbidites, 10.5 - 9.2 Ma) and Algyő Formations (fine-grained slope deposits, 10 - 9 Ma). The Beladice Formation represents shallow lacustrine deltaic deposits, fully corresponding to Újfalu (10.5 - 8.7 Ma). The overlying fluvial deposits are the Volkovce and Zagyva Formations (10 - 6 Ma). The synoptic description and characterization of these sediments offer a basin-wide insight into the development of the basin during the Late Miocene. The turbidite systems, the slope, the overlying deltaic and fluvial systems are all genetically related and are coeval at any time slice after the regression of Lake Pannon initiated about 10 Ma ago. All these formations get younger towards the S, SE as the progradation of the shelf-slope went on. The basin got filled up to lake level by 8.7 Ma, since then fluvial deposition dominated.
Triassic integrative stratigraphy and timescale of China
The Triassic rocks are widespread in China, and both marine and terrestrial strata are well developed. The Triassic stratigraphic architecture of China is very complex in both spatial variation of the so-called “South Marine and North Continental”, i.e. the southern areas of China occupied mostly by marine facies while the northern China by terrestrial facies during the Triassic Period, and temporal transition of the “Lower Marine and Upper Continental”, i.e. the lower part of the Triassic System composed mainly of marine facies and the upper part of terrestrial strata especially in South China. Although the Global Stratotype Section and Point (GSSP) of the Permian-Triassic boundary is located in South China, the Triassic of China except for some marine Lower-Middle Triassic depositions shows significantly local characteristics and is hardly correlated with the global chronostratigraphic chart. Consequently, the Triassic of China contains not only the international research hotspots but also difficult points in stratigraphic study. This paper aims to present a brief review of the Triassic in China, including chronostratigraphy, biostratigraphy, magnetostratigraphy and chemostratigraphy, and summarize an integrated Triassic stratigraphic framework of China. Accordingly, a stratigraphic correlation is proposed for the lithostratigraphic sequences among the three tectono-paleogeographic stratigraphic regions. The comprehensive study indicates that ammonoids are the classic index fossils in Triassic biostratigraphy but conodonts are more advantageous in the study and definition of the Triassic chronostratigraphic boundaries. China still has the potential to optimize the GSSPs of the Induan-Olenekian boundary and Olenekian-Anisian boundary. The correlation of the Permian-Triassic boundary between marine and terrestrial facies might be achieved with the help of the Permian-Triassic “transitional bed” and its related biotic and environmental events in association with the biostratigraphic study of conchostracan, vertebrate and plant fossils. In addition, the carbon isotopes have been proved to be one of the powerful methods in marine Triassic stratigraphic study, whereas the oxygen and strontium isotopes may be additional important bridges to establish the correlation between the marine and terrestrial strata, but as yet lacking of relevant studies in terrestrial strata. Considering the most stratigraphic intervals of the Triassic and the terrestrial Triassic in China are difficult to be correlated to the global chart, the proposed Chinese (regional) Triassic chronostratigraphic chart of marine and terrestrial stages would be of importance to the study of Chinese Triassic stratigraphy and related aspects, but the stages must be conceptually in line with international standards and studied as soon as possible in order to finalize the definition.
Zagros orogeny: a subduction-dominated process
This paper presents a synthetic view of the geodynamic evolution of the Zagros orogen within the frame of the Arabia–Eurasia collision. The Zagros orogen and the Iranian plateau preserve a record of the long-standing convergence history between Eurasia and Arabia across the Neo-Tethys, from subduction/obduction processes to present-day collision (from ~ 150 to 0 Ma). We herein combine the results obtained on several geodynamic issues, namely the location of the oceanic suture zone, the age of oceanic closure and collision, the magmatic and geochemical evolution of the Eurasian upper plate during convergence (as testified by the successive Sanandaj–Sirjan, Kermanshah and Urumieh–Dokhtar magmatic arcs), the P–T–t history of the few Zagros blueschists, the convergence characteristics across the Neo-Tethys (kinematic velocities, tomographic constraints, subduction zones and obduction processes), together with a survey of recent results gathered by others. We provide lithospheric-scale reconstructions of the Zagros orogen from ~ 150 to 0 Ma across two SW–NE transects. The evolution of the Zagros orogen is also compared to those of the nearby Turkish and Himalayan orogens. In our geotectonic scenario for the Zagros convergence, we outline three main periods/regimes: (1) the Mid to Late Cretaceous (115–85 Ma) corresponds to a distinctive period of perturbation of subduction processes and interplate mechanical coupling marked by blueschist exhumation and upper-plate fragmentation, (2) the Paleocene–Eocene (60–40 Ma) witnesses slab break-off, major shifts in arc magmatism and distributed extension within the upper plate, and (3) from the Oligocene onwards (~ 30–0 Ma), collision develops with a progressive SW migration of deformation and topographic build-up (Sanandaj–Sirjan Zone: 20–15 Ma, High Zagros: ~12–8 Ma; Simply Folded Belt: 5–0 Ma) and with partial slab tear at depths (~10 Ma to present). Our reconstructions underline the key role played by subduction throughout the whole convergence history. We finally stress that such a long-lasting subduction system with changing boundary conditions also makes the Zagros orogen an ideal natural laboratory for subduction processes.
Miocene lithostratigraphy of the northern and central Vienna Basin (Austria)
For the first time, a concise lithostratigraphic scheme for the lower and middle Miocene (Ottnangian – Badenian) of the northern and central Vienna Basin is proposed, which is based on the integration of core-material, well-log data and seismic information from OMV. For all formations and members type sections are proposed, geographic distribution and thickness are provided, typical depositional environments and fossils are described and age constraints are discussed. This time frame allows for a more reliable calculation of sedimentation rates. This in turn might be important for the reconstruction of the tectonic history of the Vienna Basin as we do not see fundamental differences between the piggy-back stage and the subsequent pull-apart regime. Following lithostratigraphic units are formalized herein and/or are newly introduced: Bockfließ Formation (Ottnangian), Aderklaa Formation, Gänserndorf Member and Schönkirchen Member (Karpatian), Baden Group, Rothneusiedl Formation and Mannsdorf Formation (lower Badenian), Auersthal Formation, Matzen Formation, Baden Formation, Leitha Formation (middle Badenian) and Rabensburg Formation (upper Badenian).
An updated correlation of the Silurian strata in Estonia
The correlation of the Silurian succession of Estonia with the global standard has long been considered reliable. However, new information, particularly on the distribution of microfossils, has changed our understanding of the Silurian stratigraphy in the region. Recent palaeontological and geochemical data suggest that: the lower part of the Juuru Regional Stage (RS) is of Hirnantian age; the age of the base of the Raikküla RS in terms of global chronostratigraphy remains problematic; the Aeronian–Telychian boundary correlates with a level in the middle of the Rumba Formation (Fm); the base of the Adavere RS is of latest Aeronian age; the former Riksu Fm is considered to be the proximal, older part of the Sõrve Fm; the traditional lower boundary of the Jaagarahu RS is diachronous, and the closest biostratigraphic horizon that could be used is the first appearance datum of Jeppssonia sagitta rhenana; the Wenlock–Ludlow boundary correlates with a level in the upper Rootsiküla RS; the base of the Paadla RS corresponds to a level in the upper Gorstian, in the lower(?) Phlebolepis ornata Vertebrate Biozone; the Sauvere and Himmiste beds of the Paadla Fm are of late Gorstian age, and the Uduvere Beds are of early Ludfordian age, corresponding to part of the Ancoradella ploeckensis Conodont Biozone; identifying the Ludlow–Přídolí boundary in the Estonian succession is problematic, lacking reliable criteria at present. With these amendments, we present an updated regional correlation scheme drawn on a regular time scale for the first time. A problem that needs to be addressed in the future is providing better biostratigraphic definitions for the bases of regional stages.
Micropaleontology of the lower Mesoproterozoic Roper Group, Australia, and implications for early eukaryotic evolution
Well-preserved microfossils occur in abundance through more than 1000 m of lower Mesoproterozoic siliciclastic rocks composing the Roper Group, Northern Territory, Australia. The Roper assemblage includes 34 taxa, five interpreted unambiguously as eukaryotes, nine as possible eukaryotes (including Blastanosphaira kokkoda new genus and new species, a budding spheromorph with thin chagrinate walls), eight as possible or probable cyanobacteria, and 12 incertae sedis. Taxonomic richness is highest in inshore facies, and populations interpreted as unambiguous or probable eukaryotes occur most abundantly in coastal and proximal shelf shales. Phylogenetic placement within the Eukarya is difficult, and molecular clock estimates suggest that preserved microfossils may belong, in part or in toto, to stem group eukaryotes (forms that diverged before the last common ancestor of extant eukaryotes, or LECA) or stem lineages within major clades of the eukaryotic crown group (after LECA). Despite this, Roper fossils provide direct or inferential evidence for many basic features of eukaryotic biology, including a dynamic cytoskeleton and membrane system that enabled cells to change shape, life cycles that include resting cysts coated by decay-resistant biopolymers, reproduction by budding and binary division, osmotrophy, and simple multicellularity. The diversity, environmental range, and ecological importance of eukaryotes, however, were lower than in later Neoproterozoic and Phanerozoic ecosystems.
Sedimentology and chemostratigraphy of the terminal Ediacaran Dengying Formation at the Gaojiashan section, south China
The terminal Ediacaran Dengying Formation (c. 551.1-538.8 Ma) in South China is one of two successions where Ediacara-type macrofossils are preserved in carbonate facies along with skeletal fossils and bilaterian animal traces. Given the remarkable thickness of carbonate-bearing strata deposited in less than 12.3 million years, the Dengying Formation holds the potential for construction of a relatively continuous chemostratigraphic profile for the terminal Ediacaran Period. In this study, a detailed sedimentological and chemostratigraphic (δ13Ccarb, δ18Ocarb, δ13Corg, δ34Spyrite, and 87Sr/86Sr) investigation was conducted on the Dengying Formation at the Gaojiashan section, Ningqiang County of southern Shaanxi Province, South China. Sedimentological results reveal an overall shallow-marine depositional environment. Carbonate breccia, void-filling botryoidal precipitates and aragonite crystal fans are common in the Algal Dolomite Member of the Dengying Formation, suggesting that peritidal facies were repeatedly karstified. The timing of karstification was likely early, probably soon after the deposition of the dolomite sediments. The presence of authigenic aragonite cements suggests high alkalinity in the terminal Ediacaran ocean. Geochemical analysis of micro-drilled samples shows that distinct compositions are registered in different carbonate phases, which should be considered when constructing chemostratigraphic profiles representative of true temporal variations in seawater chemistry. Integrated chemostratigraphic data suggest enhanced burial of organic carbon and pyrite, and the occurrence of extensive marine anoxia (at least in the Gaojiashan Member). Rapid basinal subsidence and carbonate accumulation during a time of elevated seawater alkalinity and increased rates of pyrite burial may have facilitated the evolutionary innovation of early biomineralizing metazoans.
Geology of Piemonte region (NW Italy, Alps-Apennines interference zone)
The geological map of Piemonte Region (Italy) is a graphic representation of the geology of the region, grounded on a large geodatabase, that can be also browsed as an interactive scalable map (GeoPiemonte Map) using a WebGIS application. The Map, produced at 1:250,000 scale, is the first original release of the 'GeoPiemonte Map' project. The geological data represented on the map derive from a thorough revision of available geological maps and literature, integrated with unpublished original data. The revision and harmonisation of existing and new data have been based on explicit criteria used for the classification of geologic units and their representation on the Map. These criteria firstly aimed at providing a lithostratigraphic, hierarchic subdivision of Piemonte geologic units and describing them using shared concepts and vocabularies, consistent with IUGS Descriptive Standards for the Geosciences.
Band Ratios Matrix Transformation (BRMT): A Sedimentary Lithology Mapping Approach Using ASTER Satellite Sensor
Remote sensing imagery has become an operative and applicable tool for the preparation of geological maps by reducing the costs and increasing the precision. In this study, ASTER satellite remote sensing data were used to extract lithological information of Deh-Molla sedimentary succession, which is located in the southwest of Shahrood city, Semnan Province, North Iran. A robust and effective approach named Band Ratio Matrix Transformation (BRMT) was developed to characterize and discriminate the boundary of sedimentary rock formations in Deh-Molla region. The analysis was based on the forward and continuous division of the visible-near infrared (VNIR) and the shortwave infrared (SWIR) spectral bands of ASTER with subsequent application of principal component analysis (PCA) for producing new transform datasets. The approach was implemented to ASTER spectral band ratios for mapping dominated mineral assemblages in the study area. Quartz, carbonate, and Al, Fe, Mg –OH bearing-altered minerals such as kaolinite, alunite, chlorite and mica were appropriately mapped using the BRMT approach. The results match well with geology map of the study area, fieldwork data and laboratory analysis. Accuracy assessment of the mapping result represents a reasonable kappa coefficient (0.70%) and appropriate overall accuracy (74.64%), which verified the robustness of the BRMT approach. This approach has great potential and capability for mapping sedimentary succession with diverse local–geological–physical characteristics around the world.
Triassic integrative stratigraphy, biotas, and paleogeographical evolution of the Qinghai-Tibetan Plateau and its surrounding areas
Rocks of the Qinghai-Tibetan Plateau (QTP) host abundant Triassic fossils. So far, the well established marine fossil sequences based on ammonoids, conodonts, bivalves, brachiopods, radiolarians, and terrestrial spora-pollen sequence have become standard for biostratigraphic correlation of the QTP. For much of Triassic time, the QTP occupied a marine setting as suggested by the dominance of marine deposits. The main sedimentary types represented in the Triassic successions include littoral to shallow marine clastic rocks, shallow marine carbonate platform carbonates, bathyal to abyssal slope carbonates intercalated with clastic and siliceous deposits, coal-bearing clastic strata contained within paralic facies deposits, and littoral and terrestrial volcaniclastic rocks. These deposits are organized into four stages in ascending order: (1) Early Triassic deposits that record marine transgression, including extensive shallow marine carbonate platform strata. (2) Middle Triassic Ladinian to Late Triassic Carnian deposits, including thin-bedded limestone, fine clastics, and siliceous rocks, that accumulated at greater depths than underlying Early Triassic strata and reflect the peak of the transgression. Magmatic activity appears to have occurred in some areas during this stage. (3) Late Triassic Norian deposits that record the onset of marine regression as suggested by the widespread occurrence of platform carbonates. It is noteworthy that stage 3 deposits of the Qin-Qi-Kun area in the northernmost region of the QPT is dominated by terrestrial strata and displays evidence of local erosion. (4) Late Triassic Rhaetian littoral and shallow marine clastic and coal-bearing deposits that preserve the record of continued marine regression continued. The Indus-Yarlungzangbo Suture Zone (IYSZ) appears to have been the rifting axis during Triassic time as suggested by sedimentary facies trends that reflect deepening to south and north. Thus, the Himalaya Block to the south of the IYSZ was part of the passive margin of Gondwana whereas the north side of the IYSZ, including the Gangdis (or Lhasa) and South Qiangtang blocks, belonged to the passive margin of Eurasia. The similarity of rocks of the Bangongco-Nujiang Suture Zone (BNSZ) to the north of the IYSZ with those of the Gangdis Block to the south and the South Qiangtang Block to the north does not support the contention that the BNSZ was a rift axis during Triassic time. Results of palaeobiological research also suggest that the IYSZ rather than BNSZ was a biogeographic boundary during the Triassic. Early and Middle Triassic break-up of Pangea was accompanied on the QTP by rifting along the IYSZ. The expression of crustal shortening induced by the Indosinian Orogeny on the QTP is largely a change of sedimentary facies induced by Late Triassic uplift. Deposits of the Gangdis to South Qiangtang regions of the QTP record a transition from shallow marine carbonate platform deposits to littoral and paralic coal-bearing strata. Moreover, the stratigraphic succession of the Qin-Qi-Kun area preserves a transition from littoral clastic deposits to terrestrial facies and local erosion.