نتایج جستجو برای: microfossil
تعداد نتایج: 309 فیلتر نتایج به سال:
Massive stars ([Formula: see text]), which terminate their evolution as core-collapse supernovae, are theoretically predicted to eject [Formula: see text] of the radioisotope (60)Fe (half-life 2.61 Ma). If such an event occurs sufficiently close to our solar system, traces of the supernova debris could be deposited on Earth. Herein, we report a time-resolved (60)Fe signal residing, at least par...
Four laboratory experiments on fresh, modern diatoms collected from lakes in the Northern Great Plains of North America were carried out to assess the effects of dissolution on diatom abundance and composition. Marked differences in mean dissolution susceptibility exist between species, despite sometimes significant intra-specific variation between heterovalves. Twenty-four taxa were ranked acc...
Our understanding of the origin, evolution, and biogeography of seafloor fauna is limited because we have insufficient spatial and temporal data to resolve underlying processes. The abundance and wide distribution of modern and disarticulated fossil Ophiuroidea, including brittle stars and basket stars, make them an ideal model system for global marine biogeography if we have the phylogenetic f...
Food processing facilities and grinding stone implements are common in many Late Pleistocene and Early Holocene settlement sites, especially dating from the time plants were domesticated (Wright 1994; Dubreuil 2004; Piperno et al. 2004; Eitam 2009; Kuijt and Finlayson 2009; Willcox and Stordeur 2012). Functional and technological analyses of grinding stone tools have long played a major role in...
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The Lower and Middle Cambrian age acritarch assemblages are reported from a continuous succession of the siliciclastic-carbonate Ribota, Huermeda Daroca Formations in Iberian Chains, northeastern Spain. One new genus four species described, one them open nomenclature. microfossil allow to recognize Heliosphaeridium dissimilare - Skiagia ciliosa Volkovia dentifera ­Liepaina plana zones, disc...
Abstract The Nile Delta in Egypt represents a valuable location to study the history of human societal development and agricultural advancement. However, livelihood patterns earliest settlers – whether they were farmers or herders remains poorly understood. Here we use non-pollen palynomorphs pollen grains from sediment core taken at Sais, one archaeological sites west-central Delta, investigat...
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