نتایج جستجو برای: cambrian
تعداد نتایج: 2615 فیلتر نتایج به سال:
Bioturbation long has been ‘blamed’ for eliminating late Proterozoic-style sedimentary structures and fabrics. While the presence of diverse and complex burrows in lowermost Cambrian strata is indisputable, analysis of Precambrian– Cambrian successions in southeast Newfoundland demonstrate that this burrowing style did not produce typical Phanerozoic-style ichnofabrics. Three hundred meters of ...
BACKGROUND Extant cubozoans are voracious predators characterized by their square shape, four evenly spaced outstretched tentacles and well-developed eyes. A few cubozoan fossils are known from the Middle Cambrian Marjum Formation of Utah and the well-known Carboniferous Mazon Creek Formation of Illinois. Undisputed cubozoan fossils were previously unknown from the early Cambrian; by that time ...
—One of the enduring puzzles to Stephen Jay Gould about life on Earth was the cause or causes of the fantastic diversity of animals that exploded in the fossil record starting around 530 Ma—the Cambrian explosion. In this contribution, we first review recent phylogenetic and molecular clock studies that estimate dates for high-level metazoan diversifications, in particular the origin of the maj...
بررسیهای ژئوشیمی و رادیوایزوتوپی برای تعیین خاستگاه آپاتیت در ذخایر آهن و آپاتیت منطقهی معدنی بافق
The iron-apatite deposits of the Bafq mining district contain elevated REE content and occur together with vast alterations in country-rock which were formed due to widespread hydrothermal processes in Early Cambrian. Apatite and rare earth element geochemistry as well as radioactive isotope studies of Sm-Nd show that apatite formation might be due to hydrothermal activities and remobilization ...
A diverse fauna of organophosphatic brachiopods is described from the late early Cambrian (Series 2, Stage 3-4) Forteau Formation of southern Labrador and western Newfoundland. The total fauna includes 11 species representing a wide selection of Cambrian brachiopod groups. Three distinct assemblages are recognized: Assemblages 1 and 2 are found in shallow water carbonates in association with ar...
Morphology-based phylogenetic analyses support the monophyly of the Scalidophora (Kinorhyncha, Loricifera, Priapulida) and Nematoida (Nematoda, Nematomorpha), together constituting the monophyletic Cycloneuralia that is the sister group of the Panarthropoda. Kinorhynchs are unique among living cycloneuralians in having a segmented body with repeated cuticular plates, longitudinal muscles, dorso...
نمودار تعداد نتایج جستجو در هر سال
با کلیک روی نمودار نتایج را به سال انتشار فیلتر کنید