Hasil untuk "Stratigraphy"

F. Gradstein, J. Ogg, Frits Hilgen

This report summarizes the international divisions and ages in the Geologic Time Scale, published in 2012 (GTS2012). Since 2004, when GTS2004 was detailed, major developments have taken place that directly bear and have considerable impact on the intricate science of geologic time scaling. Precam brian now has a detailed proposal for chronostratigraphic subdivision instead of an outdated and abstract chronometric one. Of 100 chronostratigraphic units in the Phanerozoic 63 now have formal definitions, but stable chronostratigraphy in part of upper Paleozoic, Triassic and Middle Jurassic/Lower Cretaceous is still wanting. Detailed age calibration now exist between radiometric methods and orbital tuning, making 40Ar-39Ar dates 0.64% older and more accurate. In general, numeric uncertainty in the time scale, although complex and not entirely amenable to objective analysis, is improved and reduced. Bases of Paleozoic, Mesozoic and Cenozoic are bracketed by analytically precise ages, respectively 541 0.63, 252.16 0.5, and 65.95 0.05 Ma. High-resolution, direct age-dates now exist for base-Carboniferous, base-Permian, base-Jurassic, base-Cenomanian and base-Eocene. Relative to GTS2004, 26 of 100 time scale boundaries have changed age, of which 14 have changed more than 4 Ma, and 4 (in Middle to Late Triassic) between 6 and 12 Ma. There is much higher stratigraphic resolution in Late Carboniferous, Jurassic, Cretaceous and Paleogene, and improved integration with stable isotopes stratigraphy. Cenozoic and Cretaceous have a refined magneto-biochronology. The spectacular outcrop sections for the Rosello Composite in Sicily, Italy and at Zumaia, Basque Province, Spain encompass the Global Boundary Stratotype Sections and Points for two Pliocene and two Paleocene stages. Since the cycle record indicates, to the best of our knowledge that the stages sediment fill is stratigraphically complete, these sections also may fulfill the important role of stage unit stratotypes for three of these stages, Piacenzian, Zanclean and Danian

M. Blum, T. Törnqvist

Francesco Salese, Francesco Salese, Eric Hiatt et al.

The thickness and volume of the stratigraphic sequence in Mars’ northern lowlands remain poorly constrained, despite their key role in recording the planet’s geological and paleoclimatic evolution. Reliable thickness estimates are essential because they directly control calculations of volcanic effusion, surface flooding, and associated climate forcing. Here we present a revised volumetric assessment of the lowland stratigraphy - dominated by volcanic infill - based on integrated geological mapping and crater-statistical modeling. Our approach combines crater size–frequency distributions with volumetric reconstructions of buried craters and intercrater plains across both lowland and Noachian highland reference terrains. The results indicate that the minimum cumulative stratigraphic volume is at least three times greater than previous estimates, implying a proportional increase in volcanic outgassing of CO2, H2O, and SO2. These new quantitative conservative bounds provide improved constraints on early Martian volatile budgets and on mid- to late-Noachian atmospheric evolution, with implications for transient climate warming and late-stage lowland flooding.

K. Behnen, M. Hertrich, H. Maurer et al.

<p>The hypothesis of stress-induced seismic anisotropy was tested in the Bedretto Lab, a deep underground rock laboratory in the Swiss Alps. Several comprehensive cross-hole seismic surveys were acquired to analyze the directional dependency of seismic-wave velocities in the undisturbed host rock. This requires precise knowledge on the source and receiver positions as well as good data quality that allows the determination of travel times for different wave types. A tilted transverse isotropic (TTI) model that explains the measured data to a first-order approximation can be established. All relevant model parameters are well constrained using P- and S-wave arrival times. However, a systematic misfit distribution indicates that a more complex anisotropy model might be required to fully explain the measurements. This is consistent with our hypothesis that seismic anisotropy has a significant stress-induced component. More controlled laboratory experiments on the centimeter to decimeter scale were performed to validate our field measurements. These measurements show a comparable order of P- and S-wave anisotropy in the rock volume. The knowledge on the driving mechanism for anisotropy in igneous rocks can potentially help to enhance the monitoring of stress field variations during geothermal operations, thereby improving hazard assessment protocols.</p>

B. Mecozzi, F. Bona, J. Conti et al.

Since the beginning of the XIX century, Grotta Romanelli gained recognition in European stratigraphy as an important site for the Late Pleistocene, due to the attribution of its basal sediments to the Last Interglacial (MIS 5e). Its abundant archaeological and paleontological findings made the cave a key reference point for the study of human evolution and faunal dynamics in the larger Mediterranean area over approximately the last 130,000 years. After a century, a new chronostratigraphic reassessment of Grotta Romanelli revised the timeframe of its lower levels, predating them to the late Middle Pleistocene.In this study, we re-evaluate selected historical museum collections from the so-called “lower complex” of Grotta Romanelli and examine the new fossils excavated between 2015 and 2022. We identify three main mammal assemblages associated with three different interglacial periods spanning the last 350,000 years. Our findings offer new insights into terrestrial ecosystems in Mediterranean Europe from the late Middle Pleistocene to early Late Pleistocene. Additionally, they provide valuable information to the biochronological framework of the European large mammal faunas.

Wenzheng Li, Wenzheng Li, Jianyong Zhang et al.

The characteristics of elements, isotopes, and small shelly fossils were investigated for Late Ediacaran to Early Cambrian stratigraphy division and to discuss their geological implications in the northwestern Sichuan Basin. The results reveal that small shelly fossils can be detected in the high-phosphorous section, with the concentration of phosphorus mainly ranging from 2% to 8%, suggesting that this interval belongs to the Early Cambrian, which is also consistent with the carbon isotopic composition results. In addition, the Early Cambrian is denudated in the Sichuan Basin due to tectonic movement, and the characteristics of some isotopes and small shell fossils are different from those in other basins. It can be proposed that P content can support the recognition of lithological boundaries, and the high phosphorus content can be used as a reference to identify the top and bottom boundaries of the Maidiping Formation in the study area. According to the elemental compositions in the Ediacaran Dengying Formation, the variations in Si, Al, Fe, and K contents are similar in the platform area and rift area, suggesting that the third and fourth member of the Dengying Formation are also developed in the Deyang–Anyue Rift. The results suggest that both the Deng-4 member and Maidiping Formation feature contemporaneous deposition of different facies in the northwestern Sichuan Basin. The strata consist of shale intercalated with thin carbonate rock deposits in the Deyang–Anyue Rift, while carbonate rock deposits in the platform. The Deyang–Anyue Rift expanded gradually in the Late Ediacaran and eventually filled in the Early Cambrian. The data in this study illustrate that elemental compositions, isotopes, and small shelly fossils can be combined to correlate the Late Ediacaran to Early Cambrian strata and provide new evidence for Deyang–Anyue Rift evolution. The results offer some new insights for deep oil and gas exploration in the Sichuan Basin and for the tectonic–depositional–environmental–biological synergistic evolution in the Late Ediacaran to Early Cambrian transition.

J. Miró, O. Ferrer, J. A. Muñoz et al.

<p>The reactivation of former rift systems and passive margins during tectonic inversion and their incorporation into fold-and-thrust belts result in significant structural differences not only between internal and external domains, but also along-strike. The Basque–Cantabrian and Asturian systems are among the best examples to address the role of along-strike changes in rift inheritance since they show a transition from salt to basement-inherited structures divided by a transition zone separating thick- from thin-skinned structural domains. While both domains have been widely described in the literature, the transfer system separating the two has not been sufficiently investigated due to poor seismic imaging and the lack of large-scale outcrops. This contribution aims to address the linkage between basement-controlled (i.e. thick-skinned) and salt-decoupled (i.e. thin-skinned) domains and to describe how deformation is accommodated in the transitional zone between these domains. An experimental programme based on analogue models has been designed that was inspired by the transition from the thin-skinned Basque–Cantabrian Pyrenees to the east to the thick-skinned Asturian Massif to the west. As observed in nature, experimental results show that oblique structures (at low angle with the shortening direction) form in the transitional domain, and their location depends on the linkage of the active structures occurring in both surrounding thick- and thin-skinned domains at different positions. Nevertheless, their orientation and evolution are controlled by the underlying decoupling horizon (i.e. salt). The deformation in the thick-skinned domain produces significant topography over a narrow deformation area due to the lack of effective decoupling levels. On the contrary, deformation in the thin-skinned domain is more distributed due to decoupling, resulting in a wider deformation area of less topography. As a result, syn-contractional sedimentation occurs mainly in the foreland basin in front of the thick-skinned domain, whereas it is observed in the foreland but also in piggyback basins in the thin-skinned domain.</p>

P. Vermeesch, Y. Tian, Y. Tian et al.

<p>In situ U–Th–He geochronology is a potentially disruptive technique that combines laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) with laser microprobe noble gas mass spectrometry. Despite its potential to revolutionize (detrital) thermochronology, in situ U–Th–He dating is not widely used due to persistent analytical challenges. A major issue is that current in situ U–Th–He dating approaches require that the U, Th, and He measurements are expressed in units of molar concentration, in contrast with conventional methods, which use units of molar abundance. Whereas molar abundances can be reliably determined by isotope dilution, accurate concentration measurements are not so easy to obtain. In the absence of matrix-matched U–Th concentration standards and accurate He ablation pit measurements, the required molar concentration calculations introduce an uncertainty that is higher than the conventional method, an uncertainty that is itself difficult to accurately quantify. We present a solution to this problem by using proton-induced <span class="inline-formula">³</span>He as a proxy for ablation pit volume and by pairing samples with a standard of known U–Th–He age. Thus, the U–Th–He age equation can be solved using relative rather than absolute concentration measurements. Pilot experiments show that the new method produces accurate results. However, it is prone to overdispersion, which is attributed to gradients in the proton fluence. These gradients can be measured, and their effect can be removed by fixing the geometry of the sample and the standard during the proton irradiation.</p>

Pavlichenko, N.A. , Chistov, D.E.

In the course of excavations in 2016 in the north-eastern part of the Berezan settlement, sector “O-Western”, graffiti on two Ionian cups were found. One of them belongs to the “rosette bowl” type of the 2nd quarter of the 6th century BCE; the incompletely preserved inscription contains a dedication to Hermes, and the name of the owner, Deinon. The storage pit in which this vessel was discovered is dated to the 2nd quarter — mid. 6th century BCE on the basis of stratigraphy and pottery finds. The second graffito is inscribed on a large Ionian kylix with a bent rim (“Knickrandschale”). This long inscription bears the name of the owner, Pythes the son of Pericles. Despite the chronological proximity, these vessels belong to different periods of the Berezan settlement. The Deinon’s bowl is synchronous with the dugouts of the early settlement on Berezan, being one of the evidences that Greek population predominated. The Pytheas’ kylix seems to reveal the name of the owner of a large multi-chamber stone-and mudbrick house, built in the beginning of the 3rd quarter of the 6th century BCE.

Valentina Risdonne, Charlotte Hubbard, Johanna Puisto et al.

Abstract A multi-analytical study was designed to characterise historical coated plaster surfaces. The method was applied to investigate the surface coatings of the nineteenth-century plaster cast of the tombstone of the Presbyter Bruno that belongs to the Victoria and Albert Museum collection. At first, selected samples of the object were examined with Visible Light Reflectance and Ultra-Violet Fluorescence Optical Microscopy (VLR- and UVf-OM respectively) and Scanning Electron Microscopy (SEM) demonstrating a consistent stratigraphy featuring a bulk, an interface and an uppermost layer. The latter layer appeared to consist of an aged coating and dirt. Overpainted and repaired areas of the object generated samples that had additional layers on top of the aforementioned stratigraphy. A layer that seemed to be an additional surface varnish or a coating that had not been absorbed to the bulk has been observed in a couple of samples. Elemental characterization was carried out with energy dispersive X-ray spectroscopy (EDS) and further analyses were performed with X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy with focal plane array (FPA) imaging which confirmed that the bulk of the object is made of gypsum plaster containing mostly silicate and carbonate inclusions. Gas chromatography/mass spectrometry (GC/MS) and pyrolysis-GC/MS with extraction methods based on n-propanol followed by pentafluoropropionic anhydride (PFPA), tetramethylammonium hydroxide (TMAH) and 3-trifluoromethylphenyltrimethylammonium hydroxide (m-TFPTAH) were performed to detect organic media. The results suggest that the organic medium used for the surface coating is a diterpenic resin that contained silicon, aluminium and traces of other inorganic elements. The organic medium of overpainted areas was based on alkyd resins and the in-paints were characterised as a blend of silicon and barium at varied concentrations. This multi-analytical approach can generate a better understanding of manufacturing, component materials and conservation issues of coated plaster objects.

Or M. Bialik, Raymond Zammit, Aaron Micallef

Abstract The Eastern and Western Mediterranean are separated by an elevated plateau that regulates water exchange between these two basins. The Maltese archipelago, situated atop this topographic high, offers a unique window into the evolution of this plateau in the lead up to the Messinian Salinity Crisis. The Upper Coralline Limestone Formation was deposited between the late Tortonian and the early Messinian and was probably terminated by palaeoceanographic events related to the Messinian Salinity Crisis. It represents the youngest Miocene sedimentary deposits outcropping in the Maltese archipelago. This shallow‐water carbonate unit can be used to trace palaeoenvironmental changes atop the sill between the Eastern and Western Mediterranean and to explain the possible water flow restrictions to the Eastern Mediterranean that could have preceded the Messinian Salinity Crisis. Here field surveys, and analysis of the depositional environment within the Upper Coralline Limestone in Malta, are combined with recently acquired multichannel seismic reflection profiles between Malta and Gozo, to reconstruct the depositional sequence in the Malta Plateau during the late Miocene. The Upper Coralline Limestone consists of multiple coralline and larger benthic foraminifera dominated facies, extending from subtidal to intertidal environments. These accumulated in two depositional cycles observed in both outcrop and seismic reflection data. Each cycle exhibits an early aggradation–progradation phase followed by a progradation phase and a final aggradation phase. These manifest themselves in the outcrops as shallowing and deepening upwards phases. These were deposited above a deep water unit and are indicative of a preceding uplift phase followed by filling of the accommodation space through the deposition of the Upper Coralline Limestone Formation in shallow marine depths. The presence of this highly elevated sill during the late Miocene could have restricted circulation to the eastern basin.

Yue Yu, Jinmei Pan, Jiancheng Shi

Natural snow, one of the most important components of the cryosphere, is fundamentally a layered medium. In forward simulation and retrieval, a single-layer effective microstructure parameter is widely used to represent the emission of multiple-layer snowpacks. However, in most cases, this parameter is fitted instead of calculated based on a physical theory. The uncertainty under different frequencies, polarizations, and snow conditions is uncertain. In this study, we explored different methods to reduce the layered snow properties to a set of single-layer values that can reproduce the same brightness temperature (T_B) signal. A validated microwave emission model of layered snowpack (MEMLS) was used as the modelling tool. Multiple-layer snow T_B from the snow’s surface was compared with the bulk T_B of single-layer snow. The methods were tested using snow profile samples from the locally validated and global snow process model simulations, which follow the natural snow’s characteristics. The results showed that there are two factors that play critical roles in the stability of the bulk T_B error, the single-layer effective microstructure parameter, and the reflectivity at the air–snow and snow–soil boundaries. It is important to use the same boundary reflectivity as the multiple-layer snow case calculated using the snow density at the topmost and bottommost layers instead of the average density. Afterwards, a mass-weighted average snow microstructure parameter can be used to calculate the volume scattering coefficient at 10.65 to 23.8 GHz. At 36.5 and 89 GHz, the effective microstructure parameter needs to be retrieved based on the product of the snow layer transmissivity. For thick snow, a cut-off threshold of 1/e is suggested to be used to include only the surface layers within the microwave penetration depth. The optimal method provides a root mean squared error of bulk T_B of less than 5 K at 10.65 to 36.5 GHz and less than 10 K at 89 GHz for snow depths up to 130 cm.

D. Engstrom, H. E. Wright

E. I. Kulagina, E. Yu. Bashlykova

Research subject. The choice of the marker and the GSSP (Global Boundary Stratotype Section and Point) of the base of the Serpukhovian is currently one of the most urgent tasks of international stratigraphy. The first appearance datum (FAD) of the conodont Lochriea ziegleri in the lineage Lochriea nodosa – Lochriea ziegleri is proposed as a global marker for the lower boundary of the Serpukhovian Stage of the International Stratigraphic Scale. Foraminifers are widely used for the subdivision of the Carboniferous deposits and can serve as auxiliary markers. Materials and methods. In this paper, the stratigraphic distribution of the foraminiferal marker species Janischewskina delicatа, Neoarchaediscus postrugosus, Eolasiodiscus donbassicus, Monotaxinoides gracilis, Monotaxinoides subplanus is discussed. These species are used to define the lower boundary of the Serpukhovian in the Urals and in the East European Platform. Results. Data on the first descriptions of their holotypes are summarized. The distributions of these species in the sections of the western slope of the Urals (Kugarchi, Muradymovo, Ladeinaya), the eastern slope of the South Urals (“Verkhnyaya” Kardailovka, Bolshoi Kizil, Khudolaz), the Serpukhovian type sections of the Moscow Syneclise and the boreholes of the southeast of the East European Platform are compared. The published ranges of the marker species in the sections of Western Europe (Spain, France, and northern England), Morocco, Kazakhstan, and China, including the Naqing section are reviewed. Conclusion. In the shallow-water coral-brachiopod and bioherm facies of the Ural sections, two or three markers can be found simultaneously. In these sections, it is possible to unambiguously determine the lower boundary of the Serpukhovian. However, here, conodonts and ammonoids were not found. Deep-water cephalopod facies containing conodonts are not favorable for foraminifers. In sections where both conodonts and foraminifera are simultaneously encountered, the appearance of foraminiferal marker taxa and conodonts rarely coincide; however, the divergence is small. Regarding the marker taxa under study, their appearance has not been established in sediments older than those dated as the Serpukhovian.

M. Carlini, G. Viola, J. Mattila et al.

<p>Fault and fracture planes (FFPs) affecting multilayer sequences can be significantly refracted at layer–layer interfaces due to the different mechanical properties of the contiguous layers, such as shear strength, friction coefficient and grain size. Detailed studies of different but coexisting and broadly coeval failure modes (tensile, hybrid and shear) within multilayers deformed in extensional settings have led to infer relatively low confinement and differential stress as the boundary stress conditions at which FFP refraction occurs. Although indeed widely recognized and studied in extensional settings, the details of FFP nucleation, propagation and refraction through multilayers remain not completely understood, partly because of the common lack of geological structures documenting the incipient and intermediate stages of deformation. Here, we present a study on strongly refracted strike-slip FFPs within the mechanically layered turbidites of the Marnoso Arenacea Formation (MAF) of the Italian northern Apennines. The MAF is characterized by the alternation of sandstone (strong) and carbonate mudstone (weak) layers. The studied refracted FFPs formed at the front of the regional-scale NE-verging Palazzuolo anticline and post-date almost any other observed structure except for a set of late extensional faults. The studied faults document coexisting shear and hybrid (tensile–shear) failure modes and, at odds with existing models, we suggest that they initially nucleated as shear fractures (mode III) within the weak layers and, only at a later stage, propagated as dilatant fractures (modes I–II) within the strong layers. The tensile fractures within the strong layers invariably contain blocky calcite infills, which are, on the other hand, almost completely absent along the shear fracture planes deforming the weak layers. Paleostress analysis suggests that the refracted FFPs formed in a NNE–SSW compressional stress field and excludes the possibility that their present geometric attitude results from the rotation through time of faults with an initial different orientation. The relative slip and dilation potential of the observed structures was derived by slip and dilation tendency analysis. Mesoscopic analysis of preserved structures from the incipient and intermediate stages of development and evolution of the refracted FFPs allowed us to propose an evolutionary scheme wherein (a) nucleation of refracted FFPs occurs within weak layers; (b) refraction is primarily controlled by grain size and clay mineral content and variations thereof at layer–layer interfaces but also within individual layers; (c) propagation within strong layers occurs primarily by fluid-assisted development ahead of the FFP tip of a “process zone” defined by a network of hybrid and tensile fractures; (d) the process zone causes the progressive weakening and fragmentation of the affected rock volume to eventually allow the FFPs to propagate through the strong layers; (e) enhanced suitable conditions for the development of tensile and hybrid fractures can be also achieved thanks to the important role played by pressured fluids.</p>

Michael Holz, Daniel Bono Vilas-Boas, Edric Brasileiro Troccoli et al.

W. Prell, J. Imbrie, D. Martinson et al.