A Search for Sources of the Detritus of Ordovician Sandstones from the Sol-Iletsk Block (Ordovician-2 Borehole) Based on the First Data of the Geochemical and Lu/Hf Isotopic Systematics of Zircons
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This outlines the Ordovician system in Asia and comprises the following chapterrs.I. Introductory note.II. The Ordovician formations from Siberia to the Himalaya.III. The Ordovician formations in Eastern and Southeastern Asia.IV. The Ordovician formations from the Taymir peninsula to the Ural mountains through Northland and Novaya Zemlya.V. The Ordovician Biota of Asia.VI. The major classification of the Ordovician system.Figures 1 and 2 show respectively the distribution of the system in the continent and the variation of its thickness in Eastern Asia.
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The present study integrates detrital zircon U–Pb–Hf isotopic analysis from 13 sandstone samples from an Upper Cretaceous–Miocene sedimentary sequence in Nepal Himalaya to determine their provenance. These sequences constrain a shifting of provenance from south to north. The U–Pb ages from Upper Cretaceous–Palaeocene strata (Amile Formation) mainly cluster between ~1,860 and 1,400 Ma with a peak at ~1,630 Ma and an absence of grains younger than the Palaeoproterozoic (1,400 Ma) age. The detritus yielded positive detrital zircon Ɛ Hf (t) values (as high as +10). However, the detrital zircon U–Pb ages from Eocene–Miocene sequence cluster at ~500–650, ~700–900, ~1,600–1,850, and ~2,500 Ma, and in addition, they have both positive and negative Ɛ Hf (t) values (+11 to −25). This finding further elucidates that the detritus in the Amile Formation was entirely sourced from India, which changed following the time of the Bhainskati Formation deposition, to a mixture of both Asian and Indian affinities (the Himalayan region). This change in source region marks the possible time of the India–Asia collision during this transition phase, that is, Late Palaeocene–Earliest Eocene.
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ABSTRACT Ordovician chitinozoans recovered from a grayish black shale are described for the first time for subsurface North-Central Florida. The bottom-most sample of the Sun Oil Company, Earl Odom No. 1 well, Suwannee County, Fla. was bracketed as Late Arenigian to Early Caradocian. The Ordovician is immediately overlain by Silurian sediments. A new chitinozoan species is described.
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Abstract The Ordovician was a key period in the biological and geological history of the Earth. ‘A Global Synthesis of the Ordovician System’ is presented in two volumes of The Geological Society, Special Publications series. The first volume (SP532) covers general aspects of the Ordovician and also includes the syntheses of the Ordovician successions of Europe. To provide a comprehensive global overview, this second volume (SP533) represents a journey through the Ordovician System around the world. Reviews of the Ordovician of North America include syntheses of Alaska, Greenland, Canada, the USA and Mexico, whereas the South American Ordovician is summarized in a specific chapter related to Argentina and neighbouring countries. The Ordovician System of Africa is presented in chapters covering the north and the south of the continent where significant Ordovician successions occur. Australia and New Zealand, as well as Antarctica, are visited in separate chapters. Asia provides the most complex Ordovician successions that are reviewed in chapters covering Turkey and the Levant region, the Middle East, Central Asia, Kazakhstan, India, SE Asia, China, Korea, and Japan. Our journey covers a great number of locations but, with many successions still to be fully described, our knowledge of the Ordovician of the world remains incomplete.
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Eight species of silicified strophomenid brachiopods from Ordovician rocks of Kentucky are described in this report. Seven species are strophomenaceans, including six from the Middle Ordovician and one, Leptaena kentuckiana n. sp., from the Upper Ordovician. Pionomena recens Neuman from the Middle Ordovician is referred to the Davidsoniacea. Three of these species also occur in the Middle Ordovician of the northern Mississippi Valley region. Rafinesquina is abundant at many localities throughout the Middle Ordovician section of Kentucky. Other silicified strophomenaceans are rare and have been recovered only from the lower part of the Middle Ordovician section of the area. Oepikinia minnesotensis has a high degree of polymorphism of outline shape, profile, and ornament. Some Middle Ordovician species heretofore placed in Strophomena are reassigned to Tetraphalerella. Furcitella and Holtedahlina are differentiated only by the presence of a prominent fold in adult valves of Holtedaklina because a bifid dorsal medial ridge occurs in species of both genera and because the transmuscle ridges of both genera are similar. The possession by Pionomena recens of a perideltidium, dentifers, dorsal medial node, and impunctate shell indicates relationship of this genus to the Davidsoniacea.
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Phyllite
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The Ordovician is one of the longest and geologically most active periods in Phanerozoic history. The unique Ordovician biodiversifications established modern marine ecosystems, whereas the first plants originated on land. The two volumes cover all key topics on Ordovician research and provide a review of Ordovician successions across the globe.
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The Ordovician is one of the longest and geologically most active periods in Phanerozoic history. The unique Ordovician biodiversifications established modern marine ecosystems, whereas the first plants originated on land. The two volumes cover all key topics on Ordovician research and provide a review of Ordovician successions across the globe.
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