Hasil untuk "Stratigraphy"

P. Sharland, R. Archer, D. Casey et al.

C. Payton

P. Vail

Enrique Garcia-Franco, María-Pilar Martínez-Hernando, Roberto Paredes et al.

Lithium is an essential material for lightweight batteries. Traditional mining of soluble salts expanded to include the extraction of hard rocks, which requires their solubilization through roasting. Among hard lithium rocks, spodumene has recently received attention from the scientific community. Its metallurgical processing can be classified according to the type of reagents, as well as the operating temperature and pressure. The use of calcium carbonate as a natural alkali avoids aggressive chemicals such as sulfuric acid or caustic soda. In this article, 0.5 g of jewelry-grade spodumene was loaded into a ceramic crucible with 2.5 g of reducing agent in a tandem of roasting at 1050 °C-1 bar-30 min and leaching with neutral water at 90 °C-1 bar-20 min at a water/clinker mass ratio of 25. Measurements by XRD, ICP-OES, and SEM-EDX suggest a pathway of spodumene cracking because of poor contact with the reductant. Potassium present in the crucible acts as a flux and encapsulates spodumene crystals, causing lithium to end up bound to silica. While lithium metasilicate is barely soluble in water, leaching potassium aluminate hoards in the liquid. The empirical observations were supported with thermodynamic spontaneity studies, which required compiling the mineral properties based on open reference tabulations.

Sergio Moreno, Mohamed Amine Doukani, Ana Hipólito et al.

During the last two decades, the Macaronesian archipelagos have been the focus of multiple studies targeting the abundant and diversified fossil record from late Neogene and Quaternary deposits. This record of past biota, ecosystems and climates is crucial for understanding the impact of glacial–interglacial cycles on Atlantic littoral marine organisms. Coupled with ongoing studies on the factors responsible for global climate change and associated sea-level variations, they contributed decisively towards the development of the modern marine island biogeography theory. Our current knowledge of the evolutionary and biogeographic history of the past and extant, shallow-water marine organisms from the Macaronesian geographic region relies on detailed analysis of many individual fossiliferous outcrops by means of quantitative and qualitative methodologies. Here, we focus on the fossil record of a newly studied MIS 5e outcrop at Pedra-que-pica (PQP), on Santa Maria Island (Azores Archipelago, Portugal). This multidisciplinary work integrates geology, paleontology and biology, providing the first detailed description of the sedimentary facies and stratigraphic framework of the PQP MIS 5e sequence that, coupled with the documentation of the biodiversity and ecological composition of PQP molluscan assemblages, allows us to produce a paleoecological reconstruction and to compare PQP with other last interglacial outcrops from Santa Maria Island. Our results increase the number of the Azorean MIS 5e marine molluscs to 140 taxa (116 Gastropoda and 24 Bivalvia). <i>Ervilia castanea</i> (Montagu, 1803) is the most abundant bivalve, while <i>Bittium nanum</i> (Mayer, 1864) and <i>Melarhaphe neritoides</i> (Linnaeus, 1758) are the most abundant gastropod species. In addition, this work emphasizes the crucial importance of complementing quantitative collecting with qualitative surveys of the fossiliferous outcrops, because nearly 42% of the bivalve species and 28% of the gastropod taxa would be missed if only quantitative samples were used. Derivation of Hill numbers and rarefaction curves both indicate that the sampling effort should be increased at PQP. Thus, although Santa Maria Island is recognized by the scientific community as one of the best-studied islands regarding the last interglacial fossil record, this study emphasizes the need to continue with similar efforts in less known outcrops on the island.

Xingyu CHEN, Zhijie ZHANG, Li WAN et al.

Significane The analysis of source-to-sink system is a comprehensive study of tectonic geology, sedimentology, and sequence stratigraphy. Because of its integral, dynamic, and semiquantitative-quantitative characteristics, it has attracted widespread attention. Progress This review first introduces the key issues of the deep-time source-to-sink systems (pre-Quaternary systems), which include the quantitative characterization of sediment mass balance and the control of the transport process on the sediment. Due to the lack of stratigraphic records and the difficulty in obtaining parameters, the research is still challenging.Second, it reviews the quantitation methods of deep-time source-to-sink systems that can be classified into three categories, namely, geochronology, uniformitarianism, and sedimentology. By obtaining information such as geomorphological parameters, hydraulic parameters, erosion rates, and sediment flux, various methods establish the quantitative relationships between "sources" and "sinks" and then rebuild the sedimentary basin infilling history. This article introduces the principles and related parameters of different methods and then compares the advantages and limitations to provide a reference for future research. It is believed that geochronology is widely used, and the core lies in provenance analysis. The key to uniformitarianism is the analogy of geological background and the selection of geological parameters. The sedimentology is controlled by multiple variables, and the tectonic-climate background and research scale need to be considered comprehensively. Conclusions and Prospects Finally, this review states the development of quantitative analysis of deep-time source-to-sink systems. Under the guidance of the important idea of "the present is the key to the past", the research needs to focus on the provenance systems, sediment routing systems, sediment dispersal, and redistributive process, and coupling relationship between various parameters. Research also needs to pay attention to quantitative analysis at multiple timescales and multidisciplinary dynamic analysis. Compared with continental margin source-to-sink systems, continental lacustrine source-to-sink system patterns and prediction models need to be further improved.

T. Sutikna, Matthew W. Tocheri, M. Morwood et al.

Великанов Петр Геннадьевич, Артюхин Юрий Павлович

Определение собственных и вынужденных колебаний рамных конструкций, моделируемых стержнями с распределенными массами (бесконечное число степеней свободы), довольно затруднительно. Поэтому в статье модель рамы наделяют конечным числом степеней свободы: массу помещают в некоторое число узлов, которые упруго взаимодействуют со стержнями, не имеющими массы. Стержни работают только на изгиб. Продольные перемещения не учитываются, так как частота продольных колебаний на два порядка выше частоты изгибных колебаний. Такая модель позволяет составить выражения кинетической и потенциальной энергии и затем с помощью уравнений Лагранжа 2-го рода получить систему дифференциальных уравнений колебаний многоэтажных зданий. В статье с использованием функций Грина, матриц жесткости, масс, податливости и др. была решена задача о свободных колебаниях Г-образной рамы. Полученные приближенные результаты при сравнении с малоизвестными точными результатами показали хорошую сходимость, особенно при увеличении числа степеней свободы (количества сосредоточенных масс, моделирующих распределенную массу стержней Г-образной рамы).

N. A. Orlova, M. V. Orlov

Background. Changes in the composition of clastic material reflect changes in both the paleogeographic environment and clast transport paths. In turn, this indicates changes in the conditions of regional development. The research relevance is determined by multidirectionality of Earth sciences, such as paleogeography, neotectonics, stratigraphy, hydrology, relief formation, etc.Aim. To establish the genesis of river valleys and bench complexes in the northern areas of the Irkutsk Oblast.Materials and methods. The clastic material of the Upper Paleozoic-Mesozoic sedimentary deposits in the northern areas of the Irkutsk Oblast was studied. The work is aimed at reconstructing the contours of sedimentary paleobasins of the Carboniferous, Permian, and Jurassic ages and the conditions of sedimentary strata formation. The results of site investigation and drilling works carried out in the 1960s and 1970s were interpreted from the standpoint of modern information.Results. The nature of river network formation and clast transport processes was determined. The direction and sources of clast transport were identified, along with the conditions of re-deposition of clastic material at different stages of the geological development of the area under study.Conclusions. The modern river network in the northern areas of the Irkutsk Oblast is based on the valleys formed under the action of catastrophic glacial water discharge flows.

Dangpeng Xi, X. Wan, Guo‐Biao Li et al.

D. Ferrill, A. Morris, R. McGinnis et al.

A. J. Mason, A. Vaks, A. Vaks et al.

<p>We describe a new method for the measurement of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">U</mi><mo>/</mo><mi mathvariant="normal">Pb</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="e043b0a717ed7605fa31d32304cccc94"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-4-33-2022-ie00001.svg" width="30pt" height="14pt" src="gchron-4-33-2022-ie00001.png"/></svg:svg></span></span> ratios by isotope dilution multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for the dating of geologically young clean carbonates, particularly speleothems. The method is intended for materials containing little or no initial <span class="inline-formula">²³²</span>Th. We illustrate and validate the method with four examples ranging from 0.57 to 20 Ma. The new method is capable of applying the <span class="inline-formula">²³⁵</span>U–<span class="inline-formula">²⁰⁷</span>Pb and <span class="inline-formula">²³⁸</span>U–<span class="inline-formula">²³⁴</span>U–<span class="inline-formula">²⁰⁶</span>Pb chronometers, common Pb and quantifiable residual <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi/><mn mathvariant="normal">234</mn></msup><mi mathvariant="normal">U</mi><msup><mo>/</mo><mn mathvariant="normal">238</mn></msup><mi mathvariant="normal">U</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="52pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="a9cbbcfe4acccbf09a9fda48c3a2a269"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-4-33-2022-ie00002.svg" width="52pt" height="15pt" src="gchron-4-33-2022-ie00002.png"/></svg:svg></span></span> disequilibrium permitting. These provide an alternative to the more widely used <span class="inline-formula">²³⁸</span>U–<span class="inline-formula">²⁰⁶</span>Pb chronometer, which can be highly inaccurate for samples that are <span class="inline-formula">&lt;</span> ca. 20 million years old, owing to uncertainties in the excess initial <span class="inline-formula">²³⁴</span>U (hence, excess radiogenic <span class="inline-formula">²⁰⁶</span>Pb) commonly observed in speleothems.</p>

Gengyun Niu, Mahir Budak, Ertan Mahir Korkmaz et al.

The systematic status of the genus <i>Athalia</i> and related genera is a perennial controversy in sawfly taxonomy. Several authors have hypothesized that the placement of <i>Athalia</i> within the Tenthredinidae is artificial, but no studies have focused on this topic. If the hypothesis that <i>Athalia</i> does not belong to Tenthredinidae can be supported, the taxonomic framework of Tenthredinoidea needs revision. We present a comprehensive phylogenomic study of Tenthredinoidae, focusing on the positions of <i>Athalia</i> and related genera by sampling 80 representatives mainly of the Tenthredinoidea, including Heptamelinae and Blasticotomidae. Our phylogenetic reconstructions based on nuclear genes and mitochondrial (mt) sequences support <i>Athalia</i> and related genera as a distinct clade sister to Tenthredinidae + (Cimbicidae + Diprionidae). A comparison of symphytan mitochondrial genomes reveals an innovative gene rearrangement pattern in Athaliidae, in which <i>Dentathalia</i> demonstrates a more ancestral pattern than <i>Athalia</i> and <i>Hypsathalia</i>. The lineage specificity of mt rRNA secondary structures also provides sufficient support to consider Athaliidae as a separate family. In summary, the phylogeny and genomic structural changes unanimously support the taxonomic treatment of Athaliidae as a family and the re-establishment of <i>Dentathalia</i> as a valid genus.