نتایج جستجو برای: microfossil
تعداد نتایج: 309 فیلتر نتایج به سال:
The present article is a review of a palaeobiogeographic analysis of Jurassic Ostracods from East Africa, India and Madagascar and includes also some general remarks on palaeobiogeography, biodiversity and Ostracod ecology.The palaeobiogeographic study shows the high significance of this microfossil group for the reconstruction of palaeogeographic processes, particularly plate tectonic developm...
Abstract The Hagen-Balve Reef Complex of the northern Rhenish Massif, Germany, is one best examples for globally widespread Givetian to Frasnian reefs. At its eastern end, in Hönne Valley, it reaches up 1000 metres thickness. In general, there limited knowledge concerning faunas and palaeoecology initial reef phases. A unique section at Binolen exposes sharp boundary between underlying, silicic...
BACKGROUND Rhizaria are a major branch of eukaryote evolution with an extensive microfossil record, but only scarce molecular data are available. The rhizarian species Reticulomyxa filosa, belonging to the Foraminifera, is free-living in freshwater environments. In culture, it thrives only as a plasmodium with thousands of haploid nuclei in one cell. The R. filosa genome is the first foraminife...
The sedimentary record, and associated micropalaeontological proxies, is one tool that has been employed to quantify a region's tropical cyclone history. Doing so has largely relied on the identification of allochthonous deposits (sediments and microfossils), sourced from deeper water and entrained by tropical cyclone waves and currents, in a shallow-water or terrestrial setting. In this study,...
Sphaeromorphic algal cysts, most probably of the prasinophyte Tasmanites, and acanthomorphic acritarch vesicles, most probably Solisphaeridium, occur in a single 20 cm thick bed of micritic limestone in the lower part of the Middle Devonian (Givetian) Tully Formation near Lock Haven, Pennsylvania. Specimens are composed of authigenic calcite and pyrite crystals about 5–10 μm in length. Some spe...
The high temporal resolution of the marine microfossil record makes it possible to explore how microbial communities responded to abrupt climate changes in the past. We analysed changes in species richness and total abundance of marine diatoms in sedimentary records from the Mauritanian upwelling system and the Panama Basin spanning the last 100 000 years. The analysis shows instances of commun...
Stromatolitic iron-rich structures have been reported from many ancient environments and are often described as Frutexites, a cryptic microfossil. Although microbial formation of such structures is likely, a clear relation to a microbial precursor is lacking so far. Here we report recent iron oxidizing biofilms which resemble the ancient Frutexites structures. The living Frutexites-like biofilm...
A sedimentary pollen sequence from the coastal plain of Veracruz, Mexico, demonstrates maize cultivation by 5,000 years ago, refining understanding of the geography of early maize cultivation. Methodological issues related to bioturbation involved in dating that record combine with its similarity to a pollen sequence from the coastal plain of Tabasco, Mexico, to suggest that the inception of ma...
چکیده ندارد.
The McMurdo Dry Valleys of Antarctica are a unique environment characterized by extreme lows in temperature and precipitation, which supports a low diversity microbial and multicellular fauna and flora. Terrestrial biomass is largely limited to soil microbes and mosses, while perennially ice-covered lakes host aerobic and anaerobic microbial communities, algae, and a low diversity eukaryotic fa...
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