Swedish Museum of Natural History
Not a member yet
1516 research outputs found
Sort by
The marine δ18O record overestimates continental ice volume during Marine Isotope Stage 3
No full textThere is disagreement in the Quaternary research community in how much of the marine δ18O signal is driven by change in ice volume. Here, we examine this topic by bringing together empirical and modelling work for Marine Isotope Stage 3 (MIS 3; 57 ka to 29 ka), a time when the marine δ18O record indicates moderate continental glaciation and a global mean sea level between −60 m and −90 m. We compile and interpret geological data dating to MIS 3 to constrain the extent of major Northern Hemisphere ice sheets (Eurasian, Laurentide, Cordilleran). Many key data, especially published in the past ~15 years, argue for an ice-free core of the formerly glaciated regions that is inconsistent with inferences from the marine δ18O record. We compile results from prior studies of glacial isostatic adjustment to show the volume of ice inferred from the marine δ18O record is unable to fit within the plausible footprint of Northern Hemisphere ice sheets during MIS 3. Instead, a global mean sea level between −30 m and − 50 m is inferred from geological constraints and glacial isostatic modelling. Furthermore, limited North American ice volumes during MIS 3 are consistent with most sea-level bounds through that interval. We can find no concrete evidence of large-scale glaciation during MIS 3 that could account for the missing ~30 m of sea-level equivalent during that time, which suggests that changes in the marine δ18O record are driven by other variables, including water temperature. This work urges caution regarding the reliance of the marine δ18O record as a de facto indicator of continental ice when few geological constraints are available, which underpins many Quaternary studies.T.P. acknowledges funding from an NSF-EAR Postdoctoral Fellowship and UC President's Postdoc Program Fellowship. Field work innorthern Hudson Bay (Nunavut) is a contribution to Natural Resources Canada Geomapping for Energy and Minerals (GEM) Program (NRCancomribution number 20210064). E.J .G. was funded by Impuls- und Vernetzungsfonds, Helmholtz-Exzellenznetzwerke (grant no. ExNetOOOl-Phase 2-3) ''The Polar System and its Effects on the Ocean Floor(POSY)", Heimholtz Climate Ini tiative REKLIM (Regional Climate Change), a joint research project at the Heimholtz Association ofGerman research centers (HGF), the PACES-II program at the Alfred Wegener Institute and the Bundesministerium für Bildung und Forschungfunded project, PalMod, and a Japan Society for the Promotionof Science International Postdoctoral Research Fellowship. K.F.H. acknowledgesfunding from the Swedish Nuclear Fuel and Waste ManagementCompany (SKB). The authors acknowledge PALSEA, a working group of the International Union for Quaternary Sciences (INQUA) and Past Global Changes (PAGES), which in turn received support from theSwiss Academy of Sciences and the Chinese Academy of Sciences. Wethank Martin Roy and Pierre-Marc Godbout for constructive feedback, as weil as three anonymous reviewers. Finally, we thank the INQUA Dublin 2019 scientific committee for allowing us to present some aspects of ourwork in a session entitled: Estimates of Global Ice Volumes During MIS 3in Need of Re-Evaluation: A Multi-Disciplinary Approach.</p
Abnormal (Hydroxy)proline Deuterium Content Redefines Hydrogen Chemical Mass
No full textAnalyzing the δ2H values in individual amino acids of proteins extracted from vertebrates, we unexpectedly found insome samples, notably bone collagen from seals, more than twice as much deuterium in proline and hydroxyproline residues than inseawater. This corresponds to at least 4 times higher δ2H than in any previously reported biogenic sample. We ruled out diet as aplausible mechanism for such anomalous enrichment. This finding puts into question the old adage that “you are what you eat”
Structural and spectroscopic study of well-developed crystals of parahibbingite, β-Fe2(OH)3Cl, formed from terrestrial weathering of the Muonionalusta iron meteorite
No full textParahibbingite [β-Fe2(OH)3Cl], a new mineral recently described from ultramafic rocks in the Bushveld Complex (South Africa), has been found to form millimetric well-developed crystals as a terrestrial weathering product of the Muonionalusta iron meteorite. The mineral, initially identified by means of Raman spectroscopy, was found in a small cavity within a crust of rust on a granitic rock fragment that was in direct contact with the alteration crust of a meteorite specimen, collected in the Kitkiöjärvi area (Sweden). Its crystal structure [a = 6.9362(4), c = 14.673(1) Å, V = 611.35(7) Å3 for Z = 6] was refined from single-crystal X-ray diffraction data (R1 = 0.0331) in the space group R-3m, thus confirming the structural model of synthetic β-Fe2(OH)3Cl. It consists of a network of octahedrally coordinated Fe2+ atoms alternatively arranged in triangular and Kagomé layers, stacked along the c axis. The H position was determined, showing O-H···Cl bonds which provide a further link between layers. Parahibbingite is found to be not only an important constituent of the corrosion system of archaeological iron artefacts but can also play an important role as an alteration product of iron meteorites
Mineral and isotopic (Nd, Sr) signature of fine-grained deglacial and Holocene sediments from the Mackenzie Trough, Arctic Canada
No full textDolomites in Arctic Ocean sediments are widely attributed to erosion and transport of sediments from northern Canada and Greenland. Coarse-grained dolomite-rich ice-rafted debris is often linked to iceberg transport, but the origin of fine-grained dolomite is less well constrained. A presumed source is the Mackenzie River. In this article, we fingerprint the minerogenic and isotopic (Nd and Sr) composition of deglacial and Holocene fine-grained sediments (<38 μm) from the shallow Mackenzie Trough. Sediments from an 81.5-m borehole (MTW01) were analyzed. The borehole is composed of a progradational (deltaic), transitional (transgressive), and marine unit (<9.4 cal. ka BP). The average dolomite content (~7 percent) and ɛNd signals (−13.3) are surprisingly constant in the progradational and marine units. The isotopic signature is inherited from the Interior Platform, the major underlying bedrock region of the Mackenzie River mainstream. The transitional unit contains fluctuations in ɛNd (−11.0 and −14.6), reflecting enhanced input from the North American Cordillera and Canadian Shield that are not associated with elevated amounts of dolomite. Additional studies combining minerogenic and detrital ɛNd analyses from sites proximal to the paleo-icestreams draining the Canadian Arctic are required to ascertain the origin of dolomite enrichment in central Arctic Ocean sediments
Ett fynd av leucistisk snok : En mycket ovanlig genvariant
No full textAn observation of a female leucistic Grass snake (Natrix natrix (L.)), found in Kungsängen, Uppland, Sweden on August 26, 2022, is discussed. The observation is the first for Sweden and possibly the first for the species
History of palynological research of Mesozoic deposits in Ukraine
No full textSince the establishment of spore-pollen analysis as a method for biostratigraphic subdivision of Mesozoic rocks in Ukraine, several schools have undertaken palynological research since the middle of the 20th century. Palynologists M.I. Ustynovska, T.B. Hubkyna, N.N. Zhuhan, S.Y. Yehorova, H.Y. Ivankevych, O.Z. Isahulova, Y.V. Semenova, R.O. Rotman, and N.S. Kyrvel worked at the Kyiv school (central Ukraine); L.A. Portnyahina, H.A. Orlova-Turchyna, N.Y. Teslya, M.I. Burova, M.E. Ohorodnik, and A.S. Andreeva-Grigorovich carried out research in the Lviv school (western Ukraine); and A.K. Kruzina, A.A. Mikhelis among others worked in the Artemivsk school (eastern Ukraine). The scientific works of M.A. Voronova are basic analyses of the spores-pollen assemblages of the Lower Cretaceous. From 1963 to 2002, M.A. Voronova established the basic methodological principles of palynological research on Lower Cretaceous strata of Ukraine and elucidated important issues concerning the emergence of angiosperms, migration and evolution of the Late Jurassic and Early Cretaceous flora of ferns, developed criteria for palaeolandscape reconstructions and palaeo-weathering. G.G. Janowska focused on the palynostratigraphy of the Jurassic deposits of Crimea and Preddobrudzha. In 1952–1953, for the first time, G.V. Shramkova and A.M. Laptyeva carried out a detailed biostratigraphic division of the Jurassic–Lower Cretaceous deposits of the Dnieper-Donetsk Basin and the north-western Donbass with the help of spore-pollen analysis. E.V. Semenova characterized the Triassic and Lower Jurassic deposits of the Donbas and the Dnieper-Donetsk Basin.Despite the significant contributions of Ukrainian palynologists to the study of Mesozoic sediments, many problems remain that need to be addressed. Today, at the Institute of Geological Sciences of the National Academy of Sciences of Ukraine biostratigraphic subdivision and correlation of Mesozoic strata using palynological analysis is carried out by O.A. Shevchuk and student D.O. Pustovoitova. A comprehensive approach to the study of microresidues from Jurassic and Cretaceous samples are covered in the dissertation of O.A. Shevchuk “Stratigraphy of the Middle Jurassic–Cretaceous of Ukraine on microfossils” 2021 and in other publications. The main groups that we have studied and that are important for stratigraphy are spores and pollen, megaspores and dinocysts, along with dispersed cuticles, tracheids, remnants of structured wood, green algae (prasinophytes and Botryococcus), fungi, insects, animal body parts, acritarchs, microforaminifera, microsclerites, scolecodonts, bacteria, sclerenchyma and pseudomicrofossils. We apply a comprehensive approach to the study of microfossils, which provides a broader understanding of the palaeogeographical conditions of the region of Ukraine in the Mesozoic. The effectiveness of complex palynological studies of marine and continental Mesozoic deposits of Ukraine for stratigraphic purposes is substantiated by their application to hydrogeology and hydrocarbon exploration
Evolutionary consequences of genomic deletions and insertions in the woolly mammoth genome
No full textSpeaking of anniversaries: Who was the first modern mineralogist?
No full textMineralogy is among the oldest sciences and a core discipline of geology. Already in the Neolithic period, the recognition and use of various minerals was important knowledge for humans. Writers of the Antiquity on the subject, Theophrastus and Pliny the Elder, treated rocks and minerals from a natural-philosophical point of view. Polymaths like Avicenna (Persia) and Shen Kuo (China) in the 11th century AD also documented the minerals known to exist then. European authors of the Renaissance, with Georgius Agricola as the foremost, used the intrinsic physical properties of minerals to describe and classify them in systematic way, an approach that essentially established mineralogy as a science. In Sweden, there was little development in the field before the 18th century (a notable exception is the contributions of Urban Hjärne). During the Age of Liberty*, works relating to various aspects of minerals, by natural scientists like Johan Gottschalk Wallerius, Henrik Teofil Scheffer, Carl Linnaeus and Torbern Bergman, came to have a wide influence, far beyond Sweden’s borders. Among the mineralogists active in this dynamic period, Axel Fredrik Cronstedt stands out as an exeptionally innovative and forsighted character