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New Palaeoscolecid plates from the Cambrian Stage 3 of northern Mongolia
No full textNew material of disarticulated paleoscolecid remains have been found in “Small Shelly/Skeletal Fossils” assemblages from Cambrian Stage 3 extracted from a section in the Khubsugul Lake region of northern Mongolia. The current material is composed of isolated phosphatic plates, rendering the whole-body reconstruction and comparisons difficult. However, the morphology of the plates is unique enough to warrant description of a new genus and species Floraconformis egiinensis. The new taxon is characterised by a stellate depression network spreading from the middle that separates numerous elevations. Floraconformis egiinensis gen. et sp. nov. represents one of the oldest records of isolated palaeoscolecid plates
Jurassic system stratigraphy at the Kamianka village. Part 1. The Kozhulinska formation
No full textDespite the active research of Jurassic system deposits of Donbas during the last two centuries theissue of their stratigraphy principles is still debatable. Theauthors` analysis of the available scientific material revealedaconflict between the normatively established requirement to rely on lithostratigraphy duringthe sediment research, andthe fact that the existing common system relies on biostratigraphy. This contradiction could be solved by the study oflithostratigraphic units of the Donetsk Jurassic deposits. Therefore, the purpose of the article was to research the Kozhu-linska formation, establish its composition and describe its main features. The Lower Jurassic deposits from the outcropsnear the village of Kamyanka (Izyum district) were studied, since the studyable stratotypes of most of the Jurassic strata,which are well exposed in the studied area, are available in this area.Material and methods. The scientific search was based on the analysis of literature, results of previous drilling andmapping works, as well as own field, laboratory and analyticalstudies. Clay samples were taken from different strati-graphic levels of the formation and from different lithologicalvarieties. Laboratory research was carried out in two direc-tions: using an electron microscope and a spectrometer to detect the material composition of clays. A palynological anal-ysis of these deposits was also carried out, namely, stratifieddeposits with the help of microphytofossils, including, forthe first time, according to the orthostratigraphic group – dinocysts.Results and discussion. The results showed that the Kozhulinska formation was mainlyrepresented by shaly clays(gray, dark gray, sometimes blue-gray) that contained relatively thin layers of sandstones. The main mass of clays con-sisted of hydromicas, with an insignificant content of montmorillonite, and an even smaller amount of kaolin. The layersof quartz sandstones cemented withclay material were separately traced along the strike.Paleontological remains in the clays of Kozhulinska formation were rare. Palynological groups are mainly repre-sented by pollen and spores, as well as remains of dinophytes,green algae and acritarchs. According to paleoalgologicalanalysis, the sediments of the Kozhulinska formation are datedfor the first time.Stratigraphy. Kozhulinska formation is represented by a fairly uniform layer of montmorillonite clays of hydromicacomposition. The clays are mainly siltstone, but there are, especially in the lower part, washed clean varieties. It is im-possible to divide the formation into sub formation based on lithological features. According to biostratigraphic data,deposits are divided into Plinsbachian, Toarian and Aalenian.Paleogeography. At the end of the Early Jurassic and the beginning of the Middle Jurassic era, the territory of theKamianska area was a low-lying part of the seabed that was drained during low tides. The land that surrounded it wasalso low-lying and almost did not supply detrital material, however, there is a regular removal of plant detritus. The sourceof the terrigenous material was the sedimentary complexes of the Donetsk Ridge. Features of the chemical compositionof the world are a significant amount of iron (siderite, ocher,chamosite) and the absence of calcium and magnesiumcarbonates. At the end of the early Aalene, this unstable basinfinally regresses, which leads to the accumulation of apowerful subaerial pack of sandstones, which weigh and border the cores of anticlines - elevated areas of the bottom orsmall islands
A brief comment on Hawthorne (2023): “On the definition of distinct mineral species: A critique of current IMA-CNMNC procedures”
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The late Cenozoic evolution of the Humboldt Current System in coastal Peru: Insights from neodymium isotopes
No full textThe Humboldt Current System along the Pacific coast of South America creates one of the most productive ecosystems on Earth. To trace the origin of the water masses in this area, we measured neodymium isotope compositions (ԑNd) in tooth enameloid of two genera of coastal sharks from latest Oligocene to early Pleistocene strata in the Pisco and Sacaco basins in southern Peru. Most ԑNd values range from −4 to −1, with a strong negative excursion in the late Miocene (∼8–7 million years ago [Ma]) with values as low as −9.2. The overall trend of the ԑNd values resembles that of equatorial Pacific deep waters, though with an offset of about +2 ԑNd units until about 6 Ma. With a major input of hinterland weathering considered unlikely, we interpret this pattern as reflecting a modern-type upwelling regime, though with a lower contribution of Antarctic waters than today. Starting about 6 Ma, the contribution of Antarctic waters to the upwelling waters increased approximately to present-day levels, coincident with, and possibly driven by, increased Antarctic glaciation and the Andes reaching their present-day elevation, both of which likely enhanced the counter-clockwise circulation in the South Pacific Ocean. The negative excursion of ԑNd values in the Pisco/Sacaco basins ∼8–7 Ma coincides with a late Miocene biogenic bloom in the Pacific Ocean and elsewhere, and with a strongly increased northward bottom current observed on the Nazca Drift System just offshore our sampling area. Thus, the negative excursion of ԑNd values in the Pisco/Sacaco basins likely resulted from a southern sourced input of nutrient-rich, unradiogenic water, which could have been an important contributor to the biogenic bloom.Financial support was provided by the Bolin Centre for Climate Research (Stockholm, Sweden) to SK, and by Prociencia/Concytec research grants (E38-2019-02-Fondecyt-BM, 104-2018-Fondecyt, and 149-2018-Fondecyt-BM-IADT-AV) to RS-G.</p
Scientific justification of spatial distribution of hydrogen anomalies in the nearsurface layer of traditional and untraditional oil and gas-bearing structures and implementation of hydrogen search technology
No full textLong-term results of research on mapping of oil and gas-bearing areas on traditional and non-traditional objects (mine fields, shelf areas, astroblems) made it possible to create a database of system criteria for search technology of structural-thermo-atmospheric-hydrologic geochemical research (STAHGR). It is an integral part of methodological solutions complex.There hydrogen was used as the main constituent element of explosives for the first time insearch practice. There are of hydrogen concentrations obtained in the process of research into the mapping features of the oil and gas capacity of traditional and non-traditional HC (hydrocarbons). Their spectrum of research includes H2-hydrogen. Analysis of data results made it possible to single out anomalous single values in areas and in productive areas (in the absence of background) and to conduct detailed, multi-scale studies for the purpose of planar mapping on prospecting works and environmental impacts of gas dynamic phenomena (GDF) during the development of coal massifs.Багаторічні результати досліджень з карту-вання нафтогазоносних ділянок на традицій-них та нетрадиційних об'єктах (шахтні поля,шельфові зони, астроблеми) дозволили створи-ти базу даних системних критеріїв пошуковоїтехнології структурно-термо-атмо-гідролого-геохімічнихдосліджень (СТАГГД), де складо-вою частиною комплексу методичних рішеньвперше в пошуковій практиці використовував-ся водень як головний складовий елемент ВВ.Аналіз результатів даних розподілу водневихконцентрацій, отриманих в процесі дослі-джень картувальних ознак нафтогазоносностітрадиційних і нетрадиційних ВВ, до спектрудосліджень яких входить Н2-водень, дав можли-вість виділити аномальні поодинокі значенняяк по площах, так і в продуктивних св. (за від-сутності фонових) і провести детальні різно-масштабні дослідження з метою площинногокартування на пошукові роботи та екологічнівпливи газодинамічних явищ (ГДЯ) при розроб-ці вуглепородних масивів.Funded by the Institute of Geological Sciences of the National Academy of Sciences of Ukraine. O. Shevchuk was also funded by a grant from the Swedish Strategic Research Fund.</p
Megafaunal extinctions, not climate change, may explain Holocene genetic diversity declines in Numenius shorebirds
No full textA linked evolution for granite-greenstone terranes of the Pilbara Craton from Nd and Hf isotopes, with implications for Archean continental growth
No full textIn felsic igneous rocks, the parent and daughter elements in the widely used Sm–Nd and Lu–Hf isotope tracer systems are mainly hosted in accessory phases. Recrystallisation and/or breakdown of these minerals during metamorphism, deformation and weathering potentially compromises the chemical and isotopic composition of the respective whole rocks, impeding the utility of such information for deducing the timing, rates and processes of crust-mantle differentiation in the early Earth. The different abilities of zircon and REE-rich minerals to withstand metamorphism have been suggested as a reason for the decoupling of the Lu–Hf and Sm–Nd isotope systems observed in a number of ancient gneiss terranes. The controls on element mobility and subsequent isotopic disturbance during recrystallisation and breakdown of LREE-rich accessory minerals are, however incompletely understood. Here, we use petrography, element mapping, and microanalysis of accessory minerals, in tandem with whole rock Sm–Nd data, to assess the reliability of the Sm–Nd system in the 3.59–3.58 Ga Mount Webber Gabbros, the oldest rocks in the Pilbara Craton (Western Australia). We show that despite multiple thermal events, which reset the mineral Sm–Nd systematics, and decomposition of the REE-rich mineral allanite, the Mount Webber rocks retained the Sm–Nd isotope signatures of their magmatic protoliths at the whole-rock scale. We show that the allanite breakdown occurred during modern, near-surface weathering processes at low temperature, such that the REE were sequestered into secondary minerals rather than escaping in higher temperature metamorphic fluids. The whole rock Sm–Nd, and zircon O–Hf signatures, together with new 142Nd isotope data, suggest derivation of the Mount Webber rocks from undifferentiated mantle sources that preserve no evidence for Hadean silicate Earth differentiation. This study highlights the benefits of a combined analytical approach using both in-situ and whole-rock isotope analyses to obtain a more complete record of the source and thermal evolution of ancient, highly metamorphosed igneous rocks
Repeatedly Northwards and Upwards: Southern African Grasslands Fuel the Colonization of the African Sky Islands in Helichrysum (Compositae)
No full textThe Afromontane and Afroalpine areas constitute some of the main biodiversity hotspots of Africa. They are particularly rich in plant endemics, but the biogeographic origins and evolutionary processes leading to this outstanding diversity are poorly understood. We performed phylogenomic and biogeographic analyses of one of the most species-rich plant genera in these mountains, Helichrysum (Compositae-Gnaphalieae). Most previous studies have focused on Afroalpine elements of Eurasian origin, and the southern African origin of Helichrysum provides an interesting counterexample. We obtained a comprehensive nuclear dataset from 304 species ( 50% of the genus) using target-enrichment with the Compositae1061 probe set. Summary-coalescent and concatenation approaches combined with paralog recovery yielded congruent, well-resolved phylogenies. Ancestral range estimations revealed that Helichrysum originated in arid southern Africa, whereas the southern African grasslands were the source of most lineages that dispersed within and outside Africa. Colonization of the tropical Afromontane and Afroalpine areas occurred repeatedly throughout the Miocene–Pliocene. This timing coincides with mountain uplift and the onset of glacial cycles, which together may have facilitated both speciation and intermountain gene flow, contributing to the evolution of the Afroalpine flora