Swedish Museum of Natural History
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Late Holocene peat paleodust deposition in south-western Sweden - exploring geochemical properties, local mineral sources and regional aeolian activity
No full textAtmospheric mineral dust not only interacts with the climate system by scattering incoming solar radiation and affecting atmospheric photochemistry, but also contributes critical nutrients to marine and terrestrial ecosystems. In a high-resolution analysis of paleodust deposition, peat development and soil dust sources, we assess the interplay between dust deposition and bog development of the Davidsmosse bog in south-western Sweden. Analyses of the 5400-year record (458 cm) included radiocarbon dating, bulk density, ash content, chemical and mineralogical composition and carbon stable isotopes, subsequently explored using principal component analysis. Fourteen dust events (DEs) were recorded (cal BP) in the peat sequence: 3580–3490; 3280; 3140; 3010–2840; 2740; 2610; 2480; 2340; 2240–2130; 1690; 1240; 960, 890–760, and 620–360. The majority of the DEs were coupled to increases in peat accumulation rates and increased nutrient content (N, P and K) suggesting that the DEs contributed with nutrients to the bog ecosystem, promoting increased accumulation. We also analyzed the chemical and mineral composition of potential mineral source deposits (separated into 6 grain-size fractions) from sites within a 4 km radius as well as aeolian dunes closer to the coast (25 km). The composition deposited on the present-day bog surface indicates that the bulk of the contemporary minerals have a local origin (<1.5 km), but the DEs may be of a more distant origin. The results also indicate that quartz and plagioclase feldspar content consistently increase with increasing grain-size, both in the source samples as well as in the peat sequence, and that the Si/Al ratio can be used to infer grain size changes in the peat. Two longer phases saw numerous DEs, between 2800 and 2130 cal BP and a stepwise increase from 960 towards 360 cal BP. The episodic character of the events, together with the inferred coarse grain size, suggest that the particles were deposited by (winter) storms. Future studies should include grain size analysis as well as a more in-depth comparison with regional paleo dust and storm records to increase knowledge on both transport processes (creep, saltation, suspension) and the climate processes driving late Holocene dust and storm events in Scandinavia
Uvite, CaMg3(Al5Mg)(Si6O18)(BO3)3(OH)3(OH), a new, but long-anticipated mineral species of the tourmaline supergroup from San Piero in Campo, Elba Island, Italy
No full textGlobal record of “ghost” nannofossils reveals plankton resilience to high CO2 and warming
No full textPredictions of how marine calcifying organisms will respond to climate change rely heavily on the fossilrecord of nannoplankton. Declines in calcium carbonate (CaCO3) and nannofossil abundance throughseveral past global warming events have been interpreted as biocalcification crises caused by oceanacidification and related factors. We present a global record of imprint—or“ghost”—nannofossils thatcontradicts this view, revealing exquisitely preserved nannoplankton throughout an inferred Jurassicbiocalcification crisis. Imprints from two further Cretaceous warming events confirm that the fossilrecords of these intervals have been strongly distorted by CaCO3dissolution. Although the rapidity ofpresent-day climate change exceeds the temporal resolution of most fossil records, complicatingdirect comparison with past warming events, our findings demonstrate that nannoplankton were moreresilient to past events than traditional fossil evidence suggests.This work was supported by Wenner-Gren Foundation grant UPD2018-0114 (S.M.S. and V.V.); Swedish Research Council grants VR 2019-04524 (S.M.S.) and VR 2019-4061 (V.V.); Carl Tryggers Foundation grant 19:380 (V.V.); Knut and Alice Wallenberg Foundationgrant KAW 2020.0145 (V.V.); Natural Environment Research Council grant NE/I005641/1 (R.J.T.); Lund University Carbon Cycle Centre(V.V.); Bolin Centre for Climate Research (S.M.S.); and The Great Britain Sasakawa Foundation 4390 (S.D.).</p
Environmental change in the late Permian of Queensland, NE Australia: The warmup to the end-Permian Extinction
No full textThe upper part of the upper Permian succession in the Bowen Basin of Queensland, NE Australia, was investigated to ascertain the timeline and character of environmental changes in this high southern palaeolatitudinal setting leading up to the End-Permian Extinction (EPE). The study focused on (in ascending order) the Peawaddy Formation, Black Alley Shale, and Bandanna Formation, and laterally correlative units. In the western Bowen Basin, the base of the Peawaddy Formation (257 Ma) records the onset of thrust loading and volcanic activity associated with the Hunter-Bowen contractional orogeny. The Peawaddy Formation comprises a series of coarsening-upward, terrigenous clastic intervals interpreted as the product of repeated progradation of deltas into shallow, open marine environments. The overlying Black Alley Shale also comprises multiple deltaic coarsening-upward cycles, which accumulated in stressed, restricted marine environments. The uppermost Bandanna Formation and equivalents formed in extensive coastal plain to estuarine environments. All three formations accumulated under the influence of explosive volcanic activity from the emerging continental volcanicarc to the east of the foreland basin. Volcanism peaked during deposition of the Black Alley Shale around the Wuchiapingian–Changhsingian transition. Abundant dispersed gravel and glendonites (calcite pseudomorphs after ikaite) indicate that the Peawaddy Formation formed under the influence of cold conditions and possible glacial ice (P4 Glaciation; Wuchiapingian Stage). Direct evidence of cold conditions ends at the top of the Peawaddy Formation (254.5 Ma); however, Chemical Index of Alteration (CIA) data suggest that surface conditions remained cold through the accumulation of the Black Alley Shale, and the lower Bandanna until c. 253 Ma, before gradually rising through the upper Bandanna Formation. The end of P4 glaciation is also characterized by a major spike in the abundance of marine acritarchs (Micrhystridium evansii Acme Zone), reflecting the development of a regional restricted basin of elevated nutrient concentrations but reduced salinity. In contrast to this short interval of stressed marine conditions, the fossil floras indicate remarkably consistent terrestrial ecosystems throughout the late Lopingian until the EPE. The terrestrial EPE is recorded by adistinctive, laminated mudrock bed (‘Marker Mudstone’) that records a palynological ‘dead zone’ above the uppermost coal seam or equivalent root-penetrated horizon followed by spikes in non-marine algal abundance. Overall, the time interval 257–252 Ma represented by the studied succession does not record a simple monotonic change in palaeoenvironmental conditions, but rather a series of intermittent stepwise changes towards warmer, and more environmentally stressed conditions leading up to the EPE in eastern Australia.The research was funded by a collaborative research grant from the US National Science Foundation (EAR-1636625 to C.F.and T.F.). Funding was also received from the Swedish Research Council (VR grant 2019-04061 to V.V., and VR grant 2018-04527 to S.M.).</p
New progress in exploring the mechanisms underlying extraordinarily high biodiversity in global hotspots and their implications for conservation
No full textCorrelating the continental end-Permian biome collapse (Lopingian) across eastern Australia
No full textThe end-Permian extinction event (EPE; 252 million years ago) was the most extreme mass extinction in Earth’s history (Stanley, 2016) and has been linked to rapid, planet-scale warming (Frank et al., 2021). The Australian stratigraphic record offers a globally unique opportunity to explore the severity and pace of terrestrial carbon sinks in response to this hyperthermal event across a broad latitudinal range. The Bowen, Sydney and Tasmania basins of eastern Australia collectively represent a ~2500 km north-south transect (Fig. 1) of contemporaneous continental depositional environments and floras during the Late Permian and Early Triassic (palaeolatitudes:~45–75°S). From the Sydney Basin, our team has built a robust chronostratigraphic framework (Fig.2), with which we have reconstructed the timeline of continental environmental and floral changes in the region (Fielding etal., 2019, 2021; Mays et al., 2020, 2021b; Vajda et al., 2020; McLoughlin et al., 2021). More recently, we have successfully applied our chronostratigraphic scheme to the Bowen Basin to constrain the ages of the climatic and floristic changes (Frank et al., 2021). The poorly studied Tasmania Basin is the highest palaeolatitude Permian–Triassic basin of Australia, and can provide chronostratigraphic and biogeographic links between Antarctica and the other basins of eastern Australia
On the dissolution of sponge silica: Assessing variability and biogeochemical implications
No full textThe dissolution of the biogenic silica that constitutes the skeletons of silicifying organisms is an important mechanism for regenerating dissolved silicon in the ocean. The silica skeletons deposited to the seafloor after the organisms die keep dissolving until becoming definitively buried. The low dissolution rate of sponge skeletons compared to that of diatom skeletons favors their burial and makes sponges (Phylum Porifera) to function as important silicon sinks in the oceans. However, it remains poorly understood whether the large variety of siliceous skeletons existing in the Porifera involves similar variability in their dissolution rates, which would affect the general conceptualization of these organisms as silicon sinks. Herein we investigated kinetics of silica dissolution for major types of skeletons in the three siliceous lineages of Porifera, following standardized digestion conditions in 1% sodium carbonate with orbital agitation at 85°C. The results are compared with those of a previous study conducted under identical conditions, which considered diatom silica, sponge silica, and lithogenic silica. Unexpectedly, the silica of homoscleromorph sponges dissolved only a bit slower than that of freshly cultured diatoms and as fast as diatom earth. However, the rest of sponge skeletons were far more resistant, although with some differences: the isolated spicules of hexactinellid sponges dissolved slightly faster than when forming frameworks of fused spicules, being hexactinellid frameworks as resistant to dissolution as the silica of demosponges, irrespective of occurring in the form of isolated spicules or frameworks. The experiments also indicated that the complexation of sponge silica with aluminum and with chitin does not increase its resistance to dissolution. Because the rapidly-dissolving homoscleromorph sponges represent less than 1% of extant sponges, the sponge skeletons are still conceptualized as important silicon sinks due to their comparative resistance to dissolution. Yet, the turnover of silica into dissolved silicon will always be faster in environments dominated by hexactinellids with isolated spicules than in environments dominated by other hexactinellids and/or demosponges. We discuss whether the time required for a given silica type to completely dissolve in 1% sodium carbonate could be a predictor of its preservation ratio in marine sediments
Iron isotopes constrain sub-seafloor hydrothermal processes at the Trans-Atlantic Geotraverse (TAG) active sulfide mound
No full textSub-seafloor hydrothermal processes along volcanically active plate boundaries are integral to the formation of seafloor massive sulfide deposits and to oceanic iron cycling, yet the nature of their relationship is poorly understood. Here we apply iron isotope analysis to sulfide minerals from the Trans-Atlantic Geotraverse (TAG) mound and underlying stockwork, 26°N Mid-Atlantic Ridge, to trace hydrothermal processes inside an actively-forming sulfide deposit in a sediment-free mid-ocean ridge setting. We show that data for recently formed chalcopyrite imply hydrothermal fluid–mound interactions cause small negative shifts (<−0.1‰) to the δ56Fe signature of dissolved iron released from TAG into the North Atlantic Ocean. Texturally distinct types of pyrite, in turn, preserve a δ56Fe range from −1.27 to +0.56‰ that reflects contrasting precipitation mechanisms (hydrothermal fluid–seawater mixing vs. conductive cooling) and variable degrees of progressive hydrothermal maturation during the >20 kyr evolution of the TAG complex. The identified processes may explain iron isotope variations found in fossil onshore sulfide deposits
Larval morphology of the Madagascan endemic diving beetle genus Hovahydrus Biström, 1982 (Coleoptera: Dytiscidae) and phylogenetic comparison with other known Hyphydrini
No full textWe describe for the first time the instar III larva of the diving beetle genus Hovahydrus Biström, 1982, based on H. praetextus (Guignot, 1951) and a new species yet to be described (identified here as Hovahydrus sp. near H. minutissimus (Régimbart, 1903)). We include detailed morphometric and chaetotaxic analyses of the cephalic capsule, head appendages, legs, last abdominal segment and urogomphi in order to discover useful characters for distinguishing Hovahydrus larvae from those of other known Hyphydrini (Coleoptera: Dytiscidae, Hydroporinae). A provisional parsimony analysis based on larval characteristics of 11 Hyphydrini species in eight genera was conducted using the program TNT. Larval morphology supports a close relationship between Hovahydrus, Hyphydrus Illiger, 1802, and the endemic South Africa genera Andex Sharp, 1882, Coelhydrus Sharp, 1882, Darwinhydrus Sharp, 1882 and Primospes Sharp, 1882.