Hasil untuk "Stratigraphy"

K. Cohen, S. Finney, P. Gibbard et al.

The International Commission on Stratigraphy (ICS) has a long tradition of producing international charts that communicate higher-order divisions of geological time and actual knowledge on the absolute numerical ages of their boundaries. The primary objective of ICS is to define precisely a global standard set of time-correlative units (Systems, Series, and Stages) for stratigraphic successions worldwide. These units are, in turn, the basis for the Periods, Epochs and Ages of the Geological Time Scale. Setting an international global standard is fundamental for expressing geological knowledge. It is also of considerable pragmatic importance as it provides the framework through which regional-scale higher-resolution divisions can be linked, equated and collated. This is a status update on the International Chronostratigraphic Chart and the ICS website www.stratigraphy.org.

F. Gradstein, J. Ogg, M. Schmitz et al.

D. Martinson, N. Pisias, J. D. Hays et al.

P. Vail, R. Mitchum, S. Thompson et al.

N. Shackleton, N. Opdyke

B. Geel, G. Coope, T. Hammen

Ismail Chaaou, Lahcen Kabiri, Badre Essafraoui

Six lithostratigraphic sections distributed in different parts of the Errachidia-Boudenib-Erfoud basin (SE Morocco) were surveyed bed by bed and sampled in order to study stratigraphy, analyzed the facies, and characterized the depositional environment of the Senonian series. This study shows that this series is mainly constituted of three lithostratigraphic units: the first one is mixed, attesting to an alluvial plain environment disturbed by marine incursions at the base. The second is dominated by "kerkoub" sandstone bars intercalated by silt-clay intervals, reflecting a floodplain environment. The third is dominated by gypsum versicolored facies, marking an evaporitic playa environment. The correlation of the studied sections shows that the Senonian sedimentary prism opens progressively to the East. The series ends with Tertiary deposition: western marine carbonates and eastern continental conglomerates. The non-deposition of these faces in the center of the basin could be the result of the presence of a paleorelief at the Tinejdad-Goulmima transition.

CHIARA BENIGNI, POMPEO CASATI, CAMILLA PIRINI RADRIZZANI

The Middle and Upper Jurassic sequence near Foza (Asiago plateau; Venetian Alps) is characterized by important hiatuses. The relevant deposits are furthermore often found as sedimentary dikes, filling up fractures in the underlying carbonatic platform of the Calcari Grigi, Middle Liassic in age in the uppermost levels. The normal Middle and Upper Jurassic sequence includes, aver the Calcari Grigi the following formations: Lower Rosso Ammonitico Veronese and "Lumachella a Posidonia alpina", both Middle Ju­rassic in age; "Scisti ad Aptici", Upper Rosso Ammonitico Veronese and the basal part of the "Biancone", Upper Jurassic in age. In the Foza area the stratigraphic sequence changes quite rapidly in very short distances, with hiatuses involving one or more of the above mentioned formations. The presence of these hiatuses and of sedimentary dikes is in agreement with the location of the studied area near the edge of the "Trento plateau" during the Jurassic. A fossil assemblage was collected from a sedimentary dike near Lazzaretti of Foza. It consists of Brachiopods, Belemnites, Bivalves and Crinoid remains. Brachiopods are prevailing both in specimens and species number; among them 6 species, even if generally poorly preserved have been determined and described.

T. Wrona, T. Wrona, T. Wrona et al.

<p>Understanding where normal faults are located is critical for an accurate assessment of seismic hazard; the successful exploration for, and production of, natural (including low-carbon) resources; and the safe subsurface storage of CO<span class="inline-formula">₂</span>. Our current knowledge of normal fault systems is largely derived from seismic reflection data imaging, intracontinental rifts and continental margins. However, exploitation of these data sets is limited by interpretation biases, data coverage and resolution, restricting our understanding of fault systems. Applying supervised deep learning to one of the largest offshore 3-D seismic reflection data sets from the northern North Sea allows us to image the complexity of the rift-related fault system. The derived fault score volume allows us to extract almost 8000 individual normal faults of different geometries, which together form an intricate network characterised by a multitude of splays, junctions and intersections. Combining tools from deep learning, computer vision and network analysis allows us to map and analyse the fault system in great detail and in a fraction of the time required by conventional seismic interpretation methods. As such, this study shows how we can efficiently identify and analyse fault systems in increasingly large 3-D seismic data sets.</p>

H. K. Chang, R. Kowsmann, A. Figueiredo et al.

Marc Leu, Hugo Bucher, Torsten Vennemann et al.

Abstract The Smithian–Spathian boundary (SSB) crisis played a prominent role in resetting the evolution and diversity of the nekton (ammonoids and conodonts) during the Early Triassic recovery. The late Smithian nektonic crisis culminated at the SSB, ca. 2.7 Myr after the Permian–Triassic boundary mass extinction. An accurate and high-resolution biochronological frame is needed for establishing patterns of extinction and re-diversification of this crisis. Here, we propose a new biochronological frame for conodonts that is based on the Unitary Associations Method (UAM). In this new time frame, the SSB can thus be placed between the climax of the extinction and the onset of the re-diversification. Based on the study of new and rich conodont collections obtained from five sections (of which four are newly described here) in the Nanpanjiang Basin, South China, we have performed a thorough taxonomical revision and described one new genus and 21 new species. Additionally, we have critically reassessed the published conodont data from 16 other sections from South China, and we have used this new, standardized dataset to construct the most accurate, highly resolved, and laterally reproducible biozonation of the Smithian to early Spathian interval for South China. The resulting 11 Unitary Association Zones (UAZ) are intercalibrated with lithological and chemostratigraphical (δ13Ccarb) markers, as well as with ammonoid zones, thus providing a firm basis for an evolutionary meaningful and laterally consistent definition of the SSB. Our UAZ8, which is characterized by the occurrence of Icriospathodus ex gr. crassatus, Triassospathodus symmetricus and Novispathodus brevissimus, is marked by a new evolutionary radiation of both conodonts and ammonoids and is within a positive peak in the carbon isotope record. Consequently, we propose to place the SSB within the separation interval intercalated between UAZ7 and UAZ8 thus leaving some flexibility for future refinement and updating. ZooBank LSID: urn:lsid:zoobank.org:pub:12326FE6-79DD-43A8-9421-26C3883FBE2E

Emily Tilby, Preston Miracle, Graeme Barker

Shanidar Cave, Iraqi Kurdistan, is one of the most important Palaeolithic sites in Southwest Asia. This is due to the long sequence of hominin occupation of the cave and the discovery of multiple Neanderthal individuals from the original Solecki excavations (1951–1960) and recent excavations (2014 to present). Preliminary taphonomic analyses of the microvertebrate assemblage were undertaken to understand the factors affecting assemblage formation and accumulation, and this paper presents the first results of these analyses. All contexts display a high proportion of fragmentation, with a slight decrease in breakage towards the base of the sequence. Black staining and root etching were observed in a similar pattern, present in most contexts but with an increase in the lower levels. A significant proportion of the microvertebrate remains examined displayed light traces of digestion, indicating some contribution to the assemblage by predators. The results are consistent with wider palaeoecological records that indicate relatively warm, wet conditions at the base of the sequence and cooler, drier conditions at the top.

Fabrizio Banfi, Raffaella Brumana, Angelo Giuseppe Landi et al.

This paper describes the case study of the damaged church of St. Francesco in the hamlet of Arquata del Tronto (Italy) that was struck by the earthquake in 2016. The municipality commissioned the research to support the preliminary design of the preservation plan. The first digitisation level has been started from the richness of surveying data acquired from static and dynamic terrestrial laser scanning (TLS), and photogrammetry, overcoming challenging constraints due to the scaffolding covering the surfaces. The geometric survey allowed authors to acquire massively geometric and material information supporting the three-dimensional (3D) volume stratigraphic and the creation of the Heritage Building Information Modelling (HBIM). The paper proposes a shift from the Geographic Information System (GIS)-based analysis of the materials toward spatial HBIM management. Building Archaeology is turned into HBIM 3D volume stratigraphy, overcoming the bidimensional (2D) surface mapping, in favour of a 3D understanding of direct and indirect sources. Material mapping is added to HBIM 3D volume stratigraphy, and each stratigraphic unit (SU) has its proprieties. The 3D volume stratigraphic database has been designed to collect the data on the unit detection at three levels (direct sources data collection, indirect data documentation, the relation among the BIM object elements). A common data environment (CDE) has been set up to share the 3D volume informative models that can be accessed, and all the information gathered. The knowledge transfer using the eXtended reality (XR) has been devoted to the citizen and tourist fruition, enhancing the comprehension of difficult concepts like the SUs to support a better critical 3D reconstruction. It includes the phases of construction across time-lapse documentation that validates related information within the building archaeology informative models leaving spaces to the uncertainty and documenting the relationship established so far thanks to the direct and indirect sources. The result obtained is a live digital twin that can be continuously updated, which justifies the costs and time demanding of HBIM despite 2D drawings. Highlights: • 3D survey and scan-to-HBIM process for the creation of a digital twin were oriented to the preliminary design of the preservation plan of the church of St. Francesco in Arquata del Tronto (Italy). • Stratigraphy is investigated and oriented towards a digitisation process to share different levels of knowledge through new forms of digital-sharing such as Common Data Environment (CDE) and cloud-based BIM platform. • eXtended reality (XR) is the final tool to reach new levels of communication and a wider audience characterised by experts in the construction sector and virtual and non-expert tourists.

Elena A. Hensel, Martin Kehl, Luisa Wöstehoff et al.

The Sodicho Rockshelter in the southwestern Ethiopian Highlands presents a unique site that contains sediments of Upper Pleistocene and Holocene occupation phases of hunter-gatherer communities. Excavations and previous geoarchaeological research provided a first ¹⁴C chronostratigraphic framework for the last 27 ka cal BP, which supports the hypothesis of a potential environmental refugium during the Late Glacial Maximum (LGM, ~21 ± 2 ka). Nonetheless, it is necessary to extend the preliminary interpretation of stone tool assemblages, and the geoarchaeological analyses carried out so far to provide in-depth information on prehistoric human behavior at the site under changing climatic and environmental conditions. In this study, we reinvestigate the complex stratigraphy and the paleoclimatic context of Sodicho in order to expand the knowledge about site formation, post-depositional disturbances, weathering influences, and the anthropogenic impact on the sediment deposits. Micromorphological observations and the determination of active pedogenic oxides offered a more detailed look at the microstratigraphic record in relation to shifting moisture conditions during the African Humid Period (AHP, ~15 − 5 ka). Sediment alteration and reworking are connected to the influence of sheet flow, biological activity, and human impacts such as dumping activity and site maintenance. A comparison with black carbon (BC) analyses and a qualitative phytolith ratio (quantification of dark and light phytoliths) provided evidence for variations in human fire intensity. Our collaborative and multidisciplinary approach demonstrates how the complex formation of a rockshelter site in a tropical setting with changing climatic and anthropogenic impacts can be tackled.

W. Berggren, F. Hilgen, C. Langereis et al.

Katherine Power, Jamie Barnett, Travis Dickinson et al.

Irregular climate events frequently occur in Southeast Asia due to the numerous climate patterns combining. Thailand sits at the confluence of these interactions, and consequently experiences major hydrological events, such as droughts. Proxy data, speleothem records, lake sediment sequences and tree ring chronologies were used to reconstruct paleo drought conditions. These trends were compared with modelled and historic El Niño Southern Oscillation (ENSO) data to assess if the ENSO climate phenomena is causing droughts in Thailand. Drought periods were found to occur both during El Niño events and ENSO neutral conditions. This indicates droughts are not a product of one climate pattern, but likely the result of numerous patterns interacting. There is uncertainty regarding how climate patterns will evolve under climate change, but changes in amplitude and variability could potentially lead to more frequent and wider reaching hydrological disasters. It is vital that policies are implemented to cope with the resulting social and economic repercussions, including diversification of crops and reorganisation of water consumption behaviour in Thailand.

H. C. Yu, K. F. Qiu, M. Li et al.

Abstract The late Paleozoic ice age was one of the three major glaciations in the Phanerozoic. However, the influence and characteristics of this glaciation and deglaciation remain unclear. In this study, we present lithostratigraphy, biostratigraphy, and chemostratigraphy during the Late Mississippian to the Early Permian in Tarim, Northwestern China. Tarim records two Gondwana glacial events in the Serpukhovian‐Moscovian (Glacial II) and the Asselian‐Sakmarian (Glacial III). Together with the global evidence of isotopes and sea level changes, multipulsed growth and decay of Glacial II and III are confirmed. The Serpukhovian isotopic pattern in Tarim exhibits a negative δ13C excursion of −6.6‰, which is comparable to those recorded in other continents. This negative excursion and contemporaneous sea level fall are triggered by the expansion of the ice sheets of Glacial II. The glaciation maximum is marked by the global sea level fall during the Bashkirian. A two‐stage transgression and positive shifts of δ13C from the Tarim and Laurussia represent evidence of stepwise deglaciation of Glacial II during the Moscovian. Positive δ18O excursions in Tarim and other two global sections from Laurussia and the regression during early Asselian to early Sakmarian are linked to the Glacial III, confirming this event is of global origin. The eustatic rise and the negative δ18O shifts indicate the retreat of this Gondwana glacier in late Sakmarian. These continuous data sets in Tarim coupled with time equivalent stratigraphy and geochemical records provide insights into the multistage evolution of the discrete Glacial II and III events.

Miró Jordi, Muñoz Josep A., Manatschal Gianreto et al.

This contribution presents the analysis of a data set that was put together in the PhD thesis of Jordi Miró which is part of the OROGEN Project. The Basque – Cantabrian Pyrenees, that are the focus of this report, have been extensively studied over the last years. Several open debates in the Earth Science community aroused from this realm regarding the formation and reactivation of rift domains and formation of fold and thrust belts. This report summarizes the main tectonic models proposed to explain both the extension and reactivation history over this area and compile a series of data to consider for further discussions and interpretations. This report includes a thematic map of the Basque – Cantabrian Pyrenees showing an analysis of the tectono-stratigraphic evolution of the area. The map covers an area of more than 33 000 km2 and is a graphic representation of the geology of the region based on a large geodatabase including previous published maps and field observations. A composite reflection seismic line crossing the entire Basque – Cantabrian Pyrenees from the Ebro foreland basin to the offshore Landes High is also presented. This section enables to present a continuous dataset along the entire area with the projection of few drill holes, which are presented with the stratigraphic logs following the same tectono-stratigraphic legend obtained from the previous analysis. The main goal of this data report is to provide a coherent and complete dataset to the community, which enables to propose, discuss and test some of the new concepts related to the formation and reactivation of rifted margins. This data report is complementary to the contributions of Lescoutre and Manatschal (2020) and Cadenas et al. (in prep) that are part of the same special volume.

J. Smit

J. Andrés, J. Andrés, D. Draganov et al.

<p>The Spanish Central System is an intraplate mountain range that divides the Iberian Inner Plateau in two sectors – the northern Duero Basin and the Tajo Basin to the south. The topography of the area is highly variable with the Tajo Basin having an average altitude of 450–500&thinsp;m and the Duero Basin having a higher average altitude of 750–800&thinsp;m. The Spanish Central System is characterized by a thick-skin pop-up and pop-down configuration formed by the reactivation of Variscan structures during the Alpine orogeny. The high topography is, most probably, the response of a tectonically thickened crust that should be the response to (1) the geometry of the Moho discontinuity, (2) an imbricated crustal architecture, and/or (3) the rheological properties of the lithosphere. Shedding some light on these features is the main target of the current investigation. In this work, we present the lithospheric-scale model across this part of the Iberian Massif. We have used data from the Central Iberian Massif Deformation (CIMDEF) project, which consists of recordings of an almost-linear array of 69 short-period seismic stations, which define a 320 km long transect. We have applied the so-called global-phase seismic interferometry. The technique uses continuous recordings of global earthquakes (<span class="inline-formula">&gt;120</span><span class="inline-formula">^∘</span> epicentral distance) to extract global phases and their reverberations within the lithosphere. The processing provides an approximation of the zero-offset reflection response of a single station to a vertical source, sending (near)-vertical seismic energy. Results indeed reveal a clear thickening of the crust below the Central System, resulting, most probably, from an imbrication of the lower crust. Accordingly, the crust–mantle boundary is mapped as a relatively flat interface at approximately 10&thinsp;s two-way travel time except in the Central System, where this feature deepens towards the NW reaching more than 12&thinsp;s. The boundary between the upper and lower crust is well defined and is found at 5&thinsp;s two-way travel time. The upper crust has a very distinctive signature depending on the region. Reflectivity at upper-mantle depths is scattered throughout the profile, located between 13 and 18&thinsp;s, and probably related to the Hales discontinuity.</p>