Stratigraphic Data Research Articles

Paleoenvironmental reconstruction of the Permian coal beds in the Paraná Basin (Brazil): evidence from organic geochemical and sedimentological analyses

The Rio Bonito Formation (Paraná Basin) contains the thickest coal beds in Brazil, that are related to peat-swamp developed in coastal depositional systems during the early Permian. This study aims to understand the source of the coal organic matter and to distinguish depositional sub-environments along the coal-bearing interval from the southern border of the basin. The analysis was performed on sedimentological and stratigraphic data from 10 wells combined with organic petrology and geochemistry of the three coal beds. Samples were collected in different key beds from the SG-14 well, in different and strategic depths at the base (218.0 m), at the intermediate (209.0 m), and at the top (181.0 m) of the coal-bearing interval. The vitrinite reflectance measurements of the selected samples, Tmax values, C29 ααα 20 S/(20 S + 20 R) ratio, and the absence of peak Ts (and presence of peak Tm) revealed the organic matter in the coal-bearing interval is thermally immature, suggesting low burial depth for the Rio Bonito Formation in the study region. Maceral composition showed predominance of vitrinite and inertinite in the three coal samples. Rock-Eval pyrolysis data indicate that the coal beds are composed of type III kerogen in the three samples, while the biomarkers indicate type II-III kerogen mixtures. The n-alkane distribution profiles suggest dominance of terrestrial organic matter in the samples, with a possible marine contribution at the top of the coal-bearing interval. The pristane/phytane (Pr/Ph) and C27/C29 ααα20 R ratios (regular steranes) revealed sub-anoxic condition and land plants as major organic matter source for basal and intermediate parts of the coal-bearing interval. They also indicate an increased anoxic conditions and possible marine algal contribution toward the uppermost coal level. The presence of cone-in-cone-shaped structures (SG-07 well, depth 157.5 m) and Orbiculoidea fossils (SG-14 well, depth 192.5 m) are indicative of brackish water and support river-marine source mixtures at the top of the coal-bearing interval. The evolutive sedimentation model comprises four paleoenvironments for the Rio Bonito Formation along geological time, in which the basal part of the coal interval is interpreted as overbank deposits in a fluvial depositional system. On the other hand, the intermediate part of the coal-bearing interval was formed in bay-head delta, and the upper part was deposited in the central estuary, both in a tide- and wave-influenced estuarine context.

Can the intraspecific laws of variation be used as a predictive model for understanding species with insufficient data? The example of the early Heteroceratidae in their evolutionary context (heteromorph ammonites, Tethys upper Barremian)

The generalized ‘laws’ of intraspecific variability in ammonites are used as a predictive tool to define the limits of poorly known species of the early Heteroceratidae (Lazariniceras, heteromorph ammonites), based on the construction of the Heteroceras theoretical model of variation. The methodology is described and the model is confronted with the palaeontological data. The discussion of the results shows that the variability observed for Lazariniceras takes up most of the continuous variation of the theoretical model. To minimize bias, particular attention was paid to the strict stratigraphic control of the raw data (8 sections studied). Thus, and for the good application of the theoretical model, the stratigraphic canvas and the systematics of the groups studied were refined and discussed: (1) the abandonment of the Gerhardtia sartousiana Zone is proposed in favor of the new Camereiceras limentinum Zone; (2) Heteroceras astierianum, Heteroceras tardieui and Martelites bifurcatus are rehabilitated; and (3) Lazariniceras heterostylia sp. nov. and Lazariniceras lhaumeti sp. nov. are introduced while Lazariniceras astierianum is redefined. Once the theoretical model of the variation has been obtained, it was then possible to propose phylogenetic reconstruction hypotheses using the cladistic tool crossed with the stratigraphic data, used to study the evolutionary patterns and processes of the group. The results show that: (1) Lazariniceras is unambiguously a Heteroceratidae despite the absence of the early helical coiling; (2) Lazariniceras originates within the Toxancyloceras; (3) Ancyloceratidae is a paraphyletic taxon; (4) evolution of the studied group is expressed by changes in adult size, heterochronies and innovations.

New insights into Coniacian-Santonian palynology in the Neo-Tethys (Egypt), with special emphasis on the ecological and depositional significance of the freshwater alga Pediastrum

Integrated palynological and palynofacies investigation based on hundreds of samples recovered from surface and subsurface successions in Sinai and the Gulf of Suez, Egypt, offer reliable data on the depositional framework of the Coniacian-Santonian Matulla Formation. The results reveal that the palynofacies contents of the three members of the Matulla Formation differ in that the lower Matulla-3 Member is Pediastrum-dominated, Matulla-2 Member is phytoclast-dominated, and the upper Mautalla-1 Member is AOM-dominated. However, some gradational mixing is observed. The assumed subdivision is very important as the Matulla Formation is a significant hydrocarbon reservoir in the Gulf of Suez, especially since this subdivision is strongly correlated with previous informal lithostratigraphic units.Furthermore, the peak occurrence of Pediastrum and its allied colonial algae that dominate the palynological assemblage, especially in the lower member of the Matulla Formation (Matulla-3), which is marginal marine, clearly implies freshwater incursions. Hence, these fossil algae are useful tracers of river runoffs as well as suspended load, enabling reconstruction of paleo-river discharge and sediment source area determination, especially if they have a promising reservoir potential, as in this case. This noteworthy record may specify an important ecozone at this time, not only in Egypt but also regionally, based on similar records from neighboring North African regions. Ultimately, the presence of Pediastrum demonstrates a sea level fall and its good preservation argues for a deposition in lowstand system tracts, which greatly conforms to sequence stratigraphic data.

Reconstruction of the proto-type basin and tectono-paleogeography of Tarim Block in the Mesozoic

The reconstruction of the proto-type basin and tectono-paleogeography of the Tarim Basin during the Mesozoic is crucial for hydrocarbon exploration, particularly for identifying hydrocarbon source rocks. This study reconstructs the position, thickness, and distribution of the original stratigraphy, the shortening amount by structural deformation, and the distribution of sedimentary facies in each Mesozoic period using paleomagnetic data, residual stratigraphy data, seismic profiles, and lithofacies distribution. During the Triassic period, a syn-collision thrust fault structure formed in the southern Tarim Block due to the successive collision of the Tianshuihai-Bayankara terrane, North Qiangtang terrane, and South Qiangtang terrane with the Tarim Block. The sedimentary strata mainly distributed in the Northern Depression and Kuqa Depression, and their sedimentary centers continuously moved northward. In the Early-Middle Jurassic, faulted basins representing post-collision extensional structures developed on the margins of the Tarim Block. In the Late Jurassic, the Tarim Block was compressed, and the faulted basin transformed into a depressional downwarped basin with red coarse clastic sediments due to the collision of the Amdo-Dongkacuo microcontinent with the Tarim Block. In the late Early Cretaceous, the collision between the Lhasa Block and the Tarim Block caused the entire uplift of the Tarim Block, which stopped accepting deposition except for the deposition of marine facies in the southwestern Tarim Basin influenced by a large-scale transgression event. The complex evolution of the Paleo-Tethys and Neo-Tethys Oceans during the Mesozoic significantly influenced the sediment distribution and structural features of the Tarim Basin.

INTEGRATED ANALYSIS FOR ASSESSMENT OF DEEPER HYDROCARBON PLAY POTENTIAL IN REBAB-1, CENTRAL LUCONIA PROVINCE, SARAWAK

The basin history, thermal maturity, and hydrocarbon entrapments of Rebab-1 Well in Central Luconia have been relooked through the study of seismic, well log, and geochemical data to find new hydrocarbon potential in the deeper section of the well. The quality of source rocks in this area was based on assumptions, and hydrocarbon exploitation only occurs on shallow hydrocarbon plays making the potential for deeper plays difficult to ascertain. This study was conducted based on two 2D seismic lines, integrated with well lithological and stratigraphy data and geochemical data such as total organic carbon, pyrolysis, and vitrinite reflectance. Integration of these data was used to determine the deeper hydrocarbon play of Rebab-1 in Central Luconia Province. The seismic data were interpreted using Petrel software with validation from the report. Cross-plots from bulk geochemical analysis data were interpreted for the source rock's organic richness, kerogen quality, hydrocarbon-generating potentials, and thermal maturation levels. The results of seismic interpretations showed that extensional and compressional tectonics shaped the field of Rebab-1, with structures mainly trending to the NW-SE and NE-SW directions. Geochemical analysis showed that the total organic carbon content (TOC) of the samples analysed ranges between 0.06 and 2.98 wt.% indicating fair to very good source rocks producing mainly type II and mixed type II-III kerogen as the dominant kerogen. These types can generate mainly gas and mixed oil and gas accumulations upon attaining thermal maturation level. Also, Rebab-1 shows fair to very good hydrocarbon-generating potentials. The vitrinite reflectance (Ro) and Tmax results showed that the analysed samples are generally plotted in the immature, mature, and post-mature stages of oil generation but still within the gas generation window. Overall, source rocks from Rebab-1 can be said to have attained maturity at the youngest during depositions of Cycle III to older than that, and faulting and folding serves as hydrocarbon trap systems, indicative of potential in having deeper hydrocarbon plays in Rebab-1 well.

Carboniferous marine deposits of the Tontal section suggest that no Protoprecordillera existed along the Western Gondwana margin

We present new palaeontological and stratigraphic data from a poorly known section located in the Tontal Range, Argentina, whose importance is key to defining the character of a hypothetical Carboniferous mountain chain, the Protoprecordillera. The Tontal Range composed the core of the hypothetical Protoprecordillera, also called the Tontal arch. The section described here comprises Mississippian and Pennsylvanian marine and mixed marine–terrestrial units that were deposited within a proglacial (non-fjord) environment. A new correlating scheme of Tontal section units is brought based on new biostratigraphic data plus the recent development of a stratigraphic order of Carboniferous units cropping out only 15 km away. The lowermost unit in the Tontal section is Del Ratón Formation conglomerate, which passes upwards into glaciomarine shales correlated with the El Planchón Formation that bears marine bivalves and palynomorphs suggesting a Serpukhovian (Upper Mississippian) age. El Planchón is overlain by the barren Churupatí Formation, with lower units of shallow marine, fan-deltaic conglomerate, passing to fluvial redbeds. The overlying Del Salto Formation has intense intraformational folding due to slumping at its base, and consists of sandstone, organic-rich shale, and shelf carbonate, the latter containing marine invertebrates and palynomorphs that suggest a Bashkirian (Lower Pennsylvanian) age. The Tontal section represents a marginal position within a previously defined strike-slip basin (Milana and Di Pasquo, 2019) that was active during most of the Carboniferous. It was deposited in a shallow marine shelf beside a hummocky coastal landscape, the erosion of which provided rounded gravels deposited in Gilbert-type deltas with associated slumps. We found no indication this area hosted any kind of glaciers, and most of the time it was below sea level. These observations, along with the lack of any mountain-side complex or any alpine-valley glacio-related depositional features remain at this, or any neighbouring sections; suggest that there was no Protoprecordillera mountain chain. Correlation with nearby sections also suggests this margin was not influenced by any prominent topographic highs during the depositional time of the Tontal section (upper Mississipian to Pennsylvanian), but rather that this area was located near sea level, potentially with emergent and positive areas along both margins of the strike-slip basin that allowed preservation of the oldest Carboniferous units of this region. On the other hand, the tendency for generalised subsidence during the Upper Carboniferous over most of the Precordillera, may respond to the development of a volcanic arc westwards over the present Cordillera, associated with the activation of a subduction zone in the present-day Chile, turning most of the area into retroarc basins.

Бабиш-мола — столичный город эпохи античности в низовьях Сырдарьи: стратиграфия, периодизация, хронология

The article publishes the results of several years of excavations at the Babish-Mola settlement, on the territory of the ancient delta of the Syr Darya, where the agricultural Chirikrabat archaeological culture was widespread in the second half of the I millennium BC. During the three seasons of field research, the premises and a section of the bypass corridor in the north-western part of the building of the palace and temple complex — the “Big House” on the citadel of the settlement were partially opened. As a result of the work carried out on stratigraphic data, it was possible to identify three relatively different periods in the life of this site: the early one — the construction and short-term functioning of the building as a palace and two periods of habitation when the site was abandoned by the first inhabitants and fallen into disrepair. In the course of the research, a few, but quite expressive archaeological complexes were discovered, mainly fragments of ceramics, on the basis of which the lifetime of the site can be tentatively dated within the 4 th—2 nd centuries BC.

Emphasizing Lithostratigraphic Rules In Distinction Of Formal Units: Sinjar Vs Khurmala Formations, Case Study

Recognition, identification, and correlation of formal lithostratigraphic units should always follow the rules of the definition of lithostratigraphic units established in the Stratigraphic Code of Nomenclature, set by the International Stratigraphic Commission. This case study is attempting at elaborating on this argument by discussing the identification and differentiation between the Sinjar and Khurmala formations in outcrop and well sections. Stratigraphic data for this study were compiled basin-wide, with nearly fifty localities of both formations from the Zagros foreland basin of Kurdistan in NE Iraq. Examinations include a review of microfacies documentation, Facies reinterpretation as well as sequence analysis. The Sinjar and Khurmala formations are carbonate units developed during the final filling stage of the Zagros foreland basin of northeast Iraq. The Sinjar Formation is characterized by shallow marine coralgal-foraminiferal limestone of reefal, lagoonal, shoal, and overall ramp setting. Other lithologies such as dolomitic limestone or marly limestone are minor and secondary. The Khurmala Formation, on the other hand, is dominated by thick beds of dolostone with secondary lithologies including recrystallized limestone and dolomitic limestone and marly limestone. Microfacies analysis of the Khurmala Formation reveals that it represents a lagoonal lithofacies equivalent to the lagoonal facies of the Sinjar Formation but intensively dolomitized at specific areas of the basin. This close relationship between the two formations, leading in some cases to mixing between both lithologies or rather confusion and misidentification. The best way of differentiating between the two units is by adhering to the lithostratigraphic rules and principles of the formal stratigraphic description, which emphasize the formal lithostratigraphic description of each formation.

Mechanism of late diagenetic alteration of glauconite and implications for geochronology

Glauconites – the most common authigenic minerals of sedimentary rocks suitable for radiometric stratigraphic dating – are known to give sometimes strongly rejuvenated ages (i.e. younger than stratigraphic ages of their host sediments). The glauconites separated from the Ediacaran/Cambrian sediments of the western part of the East European Craton (Baltica) were used to investigate the mechanism of age rejuvenation. All pure samples gave strongly rejuvenated (Paleozoic) ages, using both K-Ar and Rb-Sr dating, older than ages of Proterozoic illite-smectites from the same area. Their diverse characteristics were compared to younger glauconite samples of the same radiometric age as the stratigraphic age of their host sediment, and to younger glauconite samples with rejuvenated ages. It was established that the rejuvenated samples differ from the primary samples in their X-ray diffraction characteristics. Their 060 reflections are broader and displaced towards higher angles, an indication of chemical heterogeneity (layers with lower, variable Fe contents). This finding was confirmed by electron probe micro-analysis (less Fe and Mg, more Al in rejuvenated glauconites), and by Fourier transform infrared spectroscopy in the OH stretching region. Average boron contents are lower in the rejuvenated glauconites, and the boron isotope composition is quite variable, with no systematic trends observed. Modeling indicates that ancient seawater δ11B was not much different from the present-day value, and that input of organic-derived boron to glauconite began at the sedimentary stage. All data combined are indicative of the mechanism of burial diagenetic alteration of glauconite: the growth of glauconitic 10 Å layers with lower iron contents at the expense of Fe-smectite layers present in the original glauconitic mineral crystallized during sedimentation, while the primary high-Fe glauconitic 10 Å layers are preserved during burial diagenesis. This mechanism is responsible for the observed chemical heterogeneity of many glauconitic samples, and for their mixed isotopic ages, intermediate between the ages of primary and diagenetic growth of 10 Å layers.

Anthropogenic problems threatening major cities: Largest surface deformations observed in Hatay, Turkey based on SBAS-InSAR

The surface deformation caused by tectonic activities and anthropogenic factors poses a great threat to cities worldwide. The investigation and monitoring of these deformations are crucial in order to create risk analysis for the future. The problem in this case is to investigate the surface deformations and their negative effects caused by groundwater use and to identify possible landslide areas. In this study, the surface deformations in Hatay province were analyzed using SBAS-InSAR. The results from these analyses were evaluated by field observations. Sentinel-1 descending (183 datasets) and ascending (147 datasets) track geometries were selected to determine the surface deformation and its temporal evolution. Both east-west and vertical surface deformations were calculated, and the surface deformation profiles, surface 3D models and time series were created. These time series were associated with monthly precipitation data. The deformation area was interpreted with regard to available well-log data and geological setting of the study area. As a result of the study, a surface deformation resembling a bowl like structure was observed in the industrial zone located in the city center of Hatay-Güzelburç. The deformation rates are approximately 22.3 cm/year in the form of subsidence, 3.6 cm/year in the form of eastern movement and 10.1 cm/year in the form of western movement. The deformation of this bowl-like structure decelerated in the winter and accelerated in the summer due to excessive water use. The average monthly precipitation dataset supports these results. The stratigraphic data from water wells and the presence of limestone outside the eastern boundary of the deformation area show a thick clay layer in the eastern block of the bowl-shaped deformation structure. The difference between these two units, which causes a sharp anomaly at the eastern border of the deformation area, is interpreted as a probable normal fault. The second study area where surface deformations are observed is the landslide zone. The deformation was found to be 7.5 cm/year in a westward direction and 1.5 cm/year as subsidence.

DETAILED ANALYTICAL STUDIES OF CUTTINGS FROM OIL AND GAS WELLS AS A MEANS OF IMPROVING THE QUALITY OF GEOLOGICAL EXPLORATION AND DRILLING OPERATIONS

For date we can observe nearly full exhaustion of the largest deposits of hydrocarbons that are easy constructed in geological way, that’s why today’s exploration work is oriented on searching of small deposits and non-traditional reservoirs. For searching and development of such deposits it is necessary to apply the high-technological methods of geologic and geophysical research, previously provided mainly by foreign companies. In this regard, there is an acute need for the emergence of new costeffective approaches for the providing of geological exploration works. In such conditions the exploration of cuttings material by the modern analytical methods may become one of the main drivers of new direction of geological works because it lets to process the results directly while drilling and receive the information in real time. The main advantages of cuttings are: the possibility to study the section of well with equal discretization distance; minimal terms of sample preparation and partial conduction of analytical studies directly during the drilling process, sampling of cuttings does not affect on the technology of well construction and does not require the conduction of supplementary tripping operations, detail study of cuttings may replace highcost methods of geophysical logging and allows to conduct the correct interwell lithological and stratigraphic correlation while cluster drilling online. However, the complex and profound study of cuttings material allows to characterize and estimate the quality of reservoirs and caprocks; study the rock sources of oil and gas and their properties; built the detailed lithological, facial and mineralogical models; detect and localize zones of latent faults and tectonic tensions, achieve the reliable stratigraphic dating; to provide the most effective tracing of horizontal production wellbore. The exploration of cuttings is actual as for old oil and gas regions, as for new oilfields with difficult construction, because it allows to achieve the qualitative geological information all over the section. Within the conditions of sanction pressure (including the import of equipment for searching and production of hydrocarbon) from the west countries, the complex exploration of cuttings material may not only complete the leakage of geological information, but also provide its growth.

Emplacement and accumulation of magmatic products in contractional structures: How does it occur? Insights from Central Andes of northern Chile

Structural and stratigraphic data demonstrate that the magmatism in northern Chile was accompanied by shortening related to the development of fold and thrust belts. However, how magmatic products were emplaced and accumulated in the contractional structures is an unresolved question. We, therefore, integrated field and seismic data from the regions of the Pampa del Tamarugal, Salar de Punta Negra Basin, and the Hornitos Fold and Thrust Belt to determine the main structures that facilitated the magma accumulation. The syn-kinematic granitic intrusions in the Hornitos Fold and Thrust Belt were preferably emplaced along fold-related thrusts. In this region, magma migrated along thrust ramps and finally accumulated into the core of the anticlines and broken synclines. Subsidiary and vertical tensional fractures controlled the magma accumulation in the hinge zone and at the axis of the folds. The seismic data from the Pampa del Tamarugal and Salar de Punta Negra Basin present evidence of buried volcanoes on inversion anticlines. During the tectonic inversion of the pre-existing Late Paleozoic to Mesozoic half-graben structures in the regions, magma migrated along the master faults and finally accumulated into the core of the inversion anticlines as sills or was expulsed to the surface as volcanoes, as evidenced by the Punta Negra Monogenetic Volcano.

Early Ediacaran Positive C-Isotope Anomaly in Limestones of the Chernaya Rechka Formation of the Igarka Uplift (Northwestern Siberian Platform)

The Precambrian Chernaya Rechka Formation (Igarka Uplift) hosts a high-amplitude positive carbonate carbon isotope anomaly (up to 12.4‰) spanning through 500 m of the section and occurring simultaneously with a rise of δ13Сorg values. The similar trends of carbon isotope variations in the carbonate fraction and organic matter are not caused by local sedimentary environments since the studied anomaly-bearing carbonates accumulated in different zones of the carbonate ramp and shallow shelf. Oxygen isotope composition of these carbonates and some other geochemical criteria indicate minimal (if any) impact of post-sedimentary processes on preservation of the isotope systems. Concentrations of trace elements in the carbonate fraction indicate alternating anoxic and oxic environments that did not affected the carbon isotope composition during accumulation of the Chernaya Rechka Formation. The profound positive δ13С anomaly was putatively caused by a global deficiency of 12С in the paleo-ocean related to accumulation of methane hydrates and burial of non-oxidized organic matter. Together with geochronological and stratigraphic data, minimal 87Sr/86Sr values (0.7074) in the Chernaya Rechka Formation reveal the lower Ediacaran (lower Vendian) age of the unit (635–580 Ma). Among the closest stratigraphic analogues of the Chernaya Rechka Formation are the Dal’nyaya Taiga Group (Patom Basin) and coeval stratigraphic sequences in the southern Siberian Platform. Global nature of the positive δ13С anomaly provide its correlation with other coeval C-isotope events worldwide.

ON THE SELECTION AND CHRONOLOGY OF ULYANIVKA TYPE KNIVES

In the collection of metal artifacts of the Late Bronze Age of the Northern Pontic region a series of bronze knives (7 objects) is distinguished, which are characterized by a notable morphological and technological feature: they have double-edged blade and a forged waist with thickening and )(-like layering of the metal at the point of transition of the blade to the handle. Among these finds, four items come from the barrow burials of Berezhnivka-Mayivka Zrubna Culture (BMZC): Basan’, Babakova Moghila 3/5 (kurgan/burial), Ivanivka 1/1, Mynkivka 6/1, Novomykolaivka, Smolovs’ka Mohyla 1/5. One knife was part of the Ulyanivka hoard of bronze objects, Mykolaiv region. Two more knives are the accidental finds from the Sumy region and Glukhiv of the same region.
 All mentioned burials with knives according to their burial features and grave goods, as well as according to the data of stratigraphy, represent the late period of the BMZC. Researchers attribute the Ulyanivka treasure either to the early period of the Sabatynivka culture, or to the late stage of the Babyne culture. Contrary to this, it seems to be more reasonable that the Ulyanivka hoard belongs to the early Sabatynivka culture and probably may be synchronized with the late BMZC. This conclusion is confirmed by the materials of the Loboykivka hoard (Dnipropetrovsk region), which includes several knives with smoothed (leveled) traces of end forging. The Loboykivka hoard belongs to the BMZC and is traditionally synchronized with the Ulyanivka hoard.
 The territorial distribution of knives with forged waist and )(-like layering of the metal shows that almost all of them within the Zrubna Culture (BMZC) area were found. This fact is decisive for the cultural attribution of such knives. Only the Ulyanivka hoard was found in the area of the Sabatynivka culture, which hints at its corresponding affiliation. However, the composition of the objects of the Ulyanivka hoard itself (sickles, adze and knife) mostly corresponds to the Zrubna culture.
 The discussed evidence allows us to distinguish the knives with forged waist and )(-like layering of the metal into a separate classification taxon and we can name them the Ulyanivka type knives.

Sequential restoration of Paradox Basin salt anticlines: Reconstruction of younger, eroded datums

Structural restoration is often accomplished by taking a folded, faulted stratigraphic horizon and transforming it back to its original, horizontal geometry. 2D sequential restoration uses a range of older to younger stratigraphic datums to reconstruct the geometric evolution of structural features through a history of multiple deformation events. For surface geology exposures, erosion may have eliminated some portions of younger horizons; these eroded gaps in stratigraphy can be mended using thickness trends to bridge the gaps. If a horizon has been fully exhumed, reconstruction of the missing stratigraphy can be inferred from burial history indicators in older, preserved units and from regional bridging from surrounding, less uplifted areas. In the Paradox Basin, late Cenozoic uplift of the Colorado Plateau has removed 1–2 km of Upper Cretaceous and Lower Tertiary stratigraphic units. Previous structural restorations have followed the structural evolution of the salt anticlines contained in the Paradox Basin from the late Paleozoic deposition of the salt-bearing Paradox Formation to end Jurassic deposition of the Morrison Formation. Yet, significant faulting and folding events continued through the Cretaceous and Tertiary. In order to capture the development of these structural features, this study reconstructs an inferred picture of the missing Upper Cretaceous and Lower Tertiary stratigraphy for Paleocene and mid-Eocene datums. Three Paradox Basin sections give an interpreted structural deformation of the salt anticlines for the Laramide event that affected much of the nearby Colorado Plateau and central Rocky Mountains. Restoration of unfaulted fold shapes show an early and very modest contractional shortening; interpreted Laramide fold amplification of the salt anticlines (∼100–150 m shortening per anticline) is followed by a later and more significant normal faulted extension (∼500 m extension per anticline). Both contraction and extension are detached from subjacent basement (= sub-Paradox) involvement. Location of basement shortening/stretching is beyond the extent of the interpreted sections and may lie within the structural features at the margins of the Paradox Basin.

Combining multi-source data to identify the paleochannel system in the saltwater intrusion area

The paleochannels in coastal areas may be the priority channels for saltwater intrusion, and identifying paleochannels is important for revealing the pollution mechanisms of coastal zone aquifers and protecting groundwater resources. The use of electrical methods to identify paleochannels has become common. Still, the highly dynamic hydrological characteristics of saltwater intrusion area and the differences in the conductive properties of saltwater and freshwater increase the uncertainty of the interpretation process. This study combined groundwater numerical simulation data, hydrochemical data and stratigraphic data to construct an electrical model of the paleochannel, which provides a reference for the interpretation of paleochannel using ERT data. The paleochannel electrical model constructed by combining multiple sources of data reflects the spatial heterogeneity of resistivity values of paleochannel in different seasons and at varying levels of saltwater intrusion, making the identification of paleochannel in saltwater intrusion areas more accurate. The results show that the paleochannel shows high resistivity anomalies relative to the background stratigraphy in brackish water areas, and low resistivity anomalies relative to the background stratigraphy in freshwater areas. Combining the paleochannel forward model with ERT data can effectively identify the paleochannel in saltwater intrusion areas.

Gli ammonoidi della Formazione di Besano pubblicati da Airaghi nel 1912 conservati al Museo Kosmos di Pavia

Ammonoids from the Besano Formation published by Airaghi in 1912 kept at the Museo Kosmos in Pavia. The ammonoids from the Besano Formation described by Airaghi in two works in 1912, belonging to the collections of the Museo di Storia Naturale di Milano, as well as many other historical collections stored in this museum, have been lost during World War II. However, some plaster casts of these specimens were recently found among the material stored in the new Museo Kosmos in Pavia during a reorganization of the deposits. The plaster casts, probably made by Airaghi, were obtained from the original specimens corresponding to some species erected by Airaghi and coming from the mine of Tre Fontane (Mt. San Giorgio, Switzerland). Lacking original specimens and related stratigraphic data, the present material is herein reclassified and considered as complementary for the corresponding neotypes, previously stated by Rieber in 1973. Among the taxa not revised in literature, two new combinations are here proposed: Serpianites marianii (Airaghi 1912) and ?Nevadites bassanii (Airaghi 1912). With these plaster casts we also uncovered some original specimens never described. The majority of the material is paired with the original labels by Airaghi. These ammonoids are characteristic of the lower and upper Secedensis Zone (Upper Anisian, Middle Triassic) of the Besano Formation. It is very likely the herein described specimens were collected in the beds belonging to the Secedensis Zone of the mine Tre Fontane which have been completely removed in the first years of excavation activity. [Article in Italian]

Coastal sedimentation and topographic changes in the Mataram Plain, Lombok (Indonesia) following the 1257 CE eruption of Samalas volcano

AbstractThe 1257 CE eruption of Samalas volcano, Indonesia, buried the entire island of Lombok beneath various thicknesses of pyroclastic material during this Volcanic Explosivity Index (VEI) 7 event. This study aims to reconstruct the paleo‐topography of western Lombok before the Samalas eruption in 1257 CE and analyse the sedimentation processes that led to its landscape evolution over the last 700 years. Stratigraphic data were collected from various surveys, such as outcrops, coring, drilling, hand auger and wells observation. Electrical resistivity tomography (ERT) measurements were performed to complement the stratigraphic data. A combination of stratigraphy, ERT and topographic data from various sources (topographic map, Digital Elevation Model Nasional [DEMNAS] and Real Time Kinematic [RTK] measurement) is employed to determine the depth of the paleo‐surface. Topographic modelling was performed by subtracting the delta‐DEM (DDEM) from the current‐DEM (CDEM). The result of this operation is a paleo‐DEM, which is used to reconstruct the paleo‐hydrographic features such as shoreline positions and river channels. Modelling results demonstrate that the relief has not been significantly modified, except in lowland areas, which is the sediment accumulation zone. River channels have experienced minor changes, except for the location of the river mouth and the degree of meandering. Significant changes occurred at the shoreline that has prograded by approximately 1.6 km during the last 700 years. A schematic model is built to illustrate the evolution processes of the study area, consisting of the pre‐eruption condition, the immediate post‐eruption condition and development of the current condition. This model further develops the previously proposed model with a higher resolution and simultaneously revises the estimated boundary of the pyroclastic density current (PDC) deposit from previous work.

Integrated Approach Optimizes Underground Gas-Storage Process

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 207941, “Underground Gas-Storage Process Optimization Using Integrated Subsurface Characterization, Dynamic Modeling, and Monitoring: A Case Study,” by Longxin Li, Yuan Zhou, and Limin Li, PetroChina Southwest Oil and Gasfield Company, et al. The paper has not been peer reviewed. _ The operator’s Xiangguosi (XGS) gasfield facility began underground gas storage (UGS) operations in a depleted gas field in southwest China in 2013. Following this initial period, the site was reassessed to increase deliverability safely during the winter months to meet future peak gas demand. The results of that analysis informed the resulting system design, in combination with fit-for-purpose reservoir-surveillance systems; caprock-seal recording pressure, rock deformation, and seismicity data in real time; and regular wellbore inspection. Introduction The XGS UGS facility currently operates in a previously depleted gas reservoir in Sichuan province. Its construction took place during the second half of 2011; cushion gas injection started in June 2013. Located in a high-tectonic-stress region, the geological setting of the XGS field is structurally complex and highly faulted and the targeted carbonate formation is heterogeneous and naturally fractured. When the studies described in the complete paper commenced in November 2019, the field hosted 22.80×108 m3 of working gas along with 19.80×108 m3 of cushion gas. As of May 2020, the reservoir had completed eight injection and six withdrawal cycles and delivered a maximum withdrawal rate of 21.96×106 m3/d. The UGS conversion plans required a revisit to analyze the possibility of increasing the withdrawal rate to 28.55×106 m3/d, thereby positioning better for future peak gas demand. The drilling of five new wells commenced in 2019. Planned Technical Approach The purpose of the study was to optimize the XGS UGS facility’s working gas capacity and improve operational performance throughout asset life. It was proposed to achieve this by 4D geomechanical and 3D dynamic flow-simulation models. The geomechanical model would hinge on an integrated subsurface characterization work flow combined with an advanced monitoring network tightly connected with the surface facility operation to ensure maximum containment and optimal injection and withdrawal rates and volumes. This holistic approach would aid in ascertaining optimal drawdown pressures to minimize rock fatigue and ensure operation of the UGS facility within safe pressure limits. Fully integrated Subsurface Characterization A detailed review of the existing petrophysical interpretation from wells calibrated with core analysis data was undertaken. Petrophysical interpretations from 29 wells were used to construct a reservoir classification and petrophysical property models. This led to the understanding that depositional facies were not the overriding control on reservoir quality in this case because the reservoir is highly affected by karstification, diagenesis, and fracturing. Prestack migrated seismic data was improved with acquisition footprint, noise, and multiple removal and then interpreted to map subsurface structure. The edited well logs were used to build synthetic seismograms. A complex structural model was created that included 22 stratigraphic zones and a detailed fault model within the main field structure, integrating stratigraphic data and log curves from all recently drilled wells.

BIRCHBARK LETTER FROM PEREYASLAVL RYAZANSKY

The corpus of texts on birch bark was replenished with another document found during excavations in the Kremlin of Pereyaslavl Ryazansky (modern Ryazan). The letter comes from the Vvedensky excavation site located in the southeastern part of the Kremlin. The stratigraphic dating of the find is the second half of the 15th century AD. Styluses and fragments of birchbark with drawings have already been found on the site. The letter was a piece of rolled birchbark with the upper and lower edges torn off centuries ago. The three surviving lines of the document produce a legible fragment of a literary text – a record of predictive meaning read under the year 6967 (1459) in ordinary paschal tables of the 15th century AD. The Ryazan birchbark letter is the clearest material evidence of the eschatological expectations that became widespread in Russian society in that period.