Formation of HD molecules in merging dark matter haloes

HD molecules can be an important cooling agent of the primordial gas behind the shock waves originated through merging of the dark matter haloes at epochs when the first luminous objects formed. We study the necessary conditions for the HD cooling to switch on in the low-temperature range   T < 200 K  . We show that these conditions are fulfilled in merging haloes with total (dark matter and baryon) mass in excess of   M _cr∼ 10⁷[(1 + z )/20]⁻² M_⊙  . Haloes with masses   M > M _cr  may be the sites of low-mass star formation.     

Mio-Pliocene magnetostratigraphy in the southern Carpathian foredeep and Mediterranean–Paratethys correlations

A full understanding of the Mio-Pliocene palaeogeographical and palaeoenvironmental changes in the circum-Mediterranean region during the Messinian Salinity Crisis (MSC) is at present hampered by the lack of reliable chronostratigraphic correlations between the Mediterranean and Paratethys regions. Here, we present magnetostratigraphic ages for the Upper Miocene to Pliocene deposits of the southern Carpathian foredeep in Romania. These ages are in good agreement with those recently obtained from the eastern Carpathian foredeep and define a new chronology for the eastern Paratethys. The Meotian/Pontian boundary is not biostratigraphically constrained in our sections, but according to the geological map of the region arrives at ∼5.8 Ma. The Pontian/Dacian boundary is dated at c. 4.8 Ma and the Dacian/Romanian boundary at c. 4.1 Ma. The main part of the MSC (5.96–5.33 Ma) is thus represented by the Pontian Stage, but the observed palaeoenvironmental and biostratigraphic changes in our sections of the eastern Paratethys do not indicate any relation with the dramatic desiccation and reflooding events of the Mediterranean.     

Provenance analysis as a key to orogenic exhumation: a case study from the East Carpathians (Romania)

Provenance analysis of the sediments from foredeep basins is crucial in understanding the contemporaneous orogenic exhumation processes. We report in this paper complex sediment provenance analysis using sandstone petrography and mudstone geochemistry, combined with magnetic susceptibility of the Upper Miocene to Pliocene deposits from Focşani foredeep basin (Romania). Data show a change of source area between 5 and 6 Ma, from an active volcanic arc towards a recycled orogenic belt, concurrent with an important increase of accumulation rate. This change was triggered by exhumation and erosion of the outer nappes from East Carpathians.     

Arsenic pollution in Patos Lagoon estuarine sediments, Brazil

Arsenic distribution in sediments of the Mirim-Patos lagoonal system is investigated. Deposits of fresh water Mirim Lagoon and those of the fresh water part of the Patos Lagoon contain 2.5 and 7.7 mg kg(-1), respectively, on average of total arsenic. In contrast, estuarine sediments of the Patos Lagoon are evidently contaminated by arsenic in high concentrations (up to 50 mg kg(-1)), and about 80% of the arsenic there is found in a bioavailable form. Analytical data coupled with direct, visual observations of estuarine water contamination by raw phosphorites and fertilizers suggest that the major source of arsenic in the estuarine sediments originated from the fertilizer industry.     

Mercury pollution sources in sediments of Patos Lagoon Estuary,Southern Brazil

Present study has continued the investigation on distribution of mercury in estuarine sediments of Patos Lagoon which began whilst assessing the after-effect of enormous accidental discharge of sulfuric acid into the estuary. An attempt to evaluate the contribution of anthropogenic effluents on mercury pollution in sediments was undertaken. The effluents from Rio Grande City sewages were categorized into four groups based on their sources. Comparison of mercury concentrations from those, indicated that domestic effluent was prevalent. Apparent geographic controls of effluent locations enriched in mercury on zones of polluted estuarine sediments were also revealed. Insufficient control on waste collecting and absence of sewage treatment are considered the principal causes of mercury pollution in estuarine sediments.     

Age constraints and tectonic settings of metallogenic and magmatic events in the Verkhoyansk-Kolyma folded area

The paper presents new isotope geochronological data for several mineral deposits, ore occurrences, and related igneous bodies (plutons and dikes) in the Verkhoyansk-Kolyma folded area, eastern Yakutia. Twenty-one ⁴⁰Ar/³⁹Ar mica and four U-Pb zircon dates provide the first age constraints on key metallogenic units in the area. The dating results allow correlation between tectonic, magmatic, and metallogenic events. The sampled mineral deposits within the Adycha-Taryn fault zone in the southeastern Verkhoyansk-Chersky orogen apparently formed at the Jurassic-Cretaceous boundary during the final phase of the collision between the Siberian (North Asian) craton and the Kolyma-Omolon microcontinent (Kupol’noe deposit and the early metallogenic pulse of the Malotarynskoe deposit, ~ 143-144 Ma) and in the latest Early Cretaceous, in the beginning of the orogen collapse (Tallalakh and Dora-Pil’ deposits and the Malotarynskoe late metallogenic pulse, ~ 126 Ma). According to the suggested new classification of metallogenic units, these deposits belong to the Late Jurassic-Early Cretaceous Yana-Kolyma metallogenic belt. The Kyuchus deposit (~ 106 Ma), the Deputatsky ore cluster (~ 106-113 Ma), and the Khotoidokh deposit (~ 116 Ma) in the northern Verkhoyansk-Kolyma folded area belong to the North Verkhoyansk metallogenic belt. Their origin was associated with accretional and collisional processes that produced the Novosibirsk-Chukotka orogen in the middle Cretaceous. The Mangazeya ore cluster (~ 100 Ma, Early-Late Cretaceous boundary) in the southwestern end of the North Tirekhtyakh magmatic transverse belt belongs to the West Verkhoyansk metallogenic belt. The Nezhdaninskoe, Zaderzhnoe, Kurum, and Kuta deposits of the South Verkhoyansk area (~ 125-120 and ~ 100-95 Ma) can be joined into a single Verkhoyansk-Okhotsk metallogenic belt. The belt resulted from accretion and collision along the East Asian active continental margin and the related formation of the South Verkhoyansk orogen in the Early Cretaceous.     

Forecast of the Diamond Potential of Taimyr

Doklady Earth Sciences - Although irrefutable evidence for the presence of signs of diamondiferous kimberlite on the Taimyr Peninsula were obtained in the 1930s, it was only in 2020 that a...     

Tidal and Planetary Waves in the Lower Thermosphere and Ionosphere Simulated with the EAGLE Model for the January 2009 Sudden Stratospheric Warming Conditions

Izvestiya, Atmospheric and Oceanic Physics - The results of analyzing the planetary and tidal variabilities in the mesosphere, thermosphere, and ionosphere acquired in calculations for January 2009...     

Fluxes of CO2 and CH4 in high latitude wetlands: measuring, modelling and predicting response to climate change

This review covers selected aspects of recent international efforts to measure and model greenhouse gas emission from northern wetlands, to identify the environmental factors that control gas emission, and to investigate wetlands'responses (particularly with respect to gas emission) to global change. Both bottom-up and top-to-bottom approaches, based respectively on local observations plus inventory of gas fluxes and inverse modelling of global circulation, agree on the size of the high latitude (>60_°N) contribution to global methane, which should be about 13% or 70 Tg/year. It has been shown that winter and spring fluxes are an essential part in the annual budget of CH₄ and especially CO₂ exchange (varying from 5 to 50%). Soil micro-organisms were shown to be able to respire during winter even at-16_°C. In comparison to aerobically respiring organisms, anaerobic methanogenic bacteria were less active in frozen soil, although they are subjected to significant stimulation by soil freeze-thaw cycles. The absence of immediate coupling of methanogenesis with plant photosynthesis implies that substrates for methane formation are derived from peat decomposition rather than from root exudation.