Geochemical distinctions of late Proterozoic and Paleozoic volcanism in the Avalon zone of New England
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Geochemistry permits distinction of two broad groups of volcanic rocks distinguished from the Avalon zone of southeastern New England. An alkalic suite is relatively enriched in K, Rb, Y, Zr, Nb, Zn, La, Ce, but lower in Al, Sr, and Ba compared to a calc-alkaline suite. The alkalic suite is compositionally similar to plutonic rocks that range in age from Late Ordovician to Devonian, whereas the calc-alkaline suite is similar to late Proterozoic plutonic rocks. Geochemical discriminant criteria developed in this chapter indicate that a number of the volcanic units previously have been incorrectly grouped and misinterpreted.Devonian
Late Devonian extinction
Margin (machine learning)
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This paper contains 50 maps which have been designed for use by the geologic community in preparing paleogeographic, biogeographic, climatologic, and tectonic reconstructions of the Paleozoic periods. Seven maps for each of seven Paleozoic intervals are included, plus a suture map showing the outlines of the Paleozoic continents in their present positions. The intervals chosen are the Late Cambrian (Franconian), Middle Ordovician (Llandeilian-earliest Caradocian), Middle Silurian (Wenlockian), Early Devonian (Emsian), Early Carboniferous (Visean), Late Carboniferous (Westphalian CD), and Late Permian (Kazanian). The paleomagnetic information used to orient the continents is given. For each interval, three types of maps are included, one locality map with place names labelled, four paleogeographic maps with our interpretation of the distribution of mountains, lowlands, shallow seas, and deep oceans, and two outline maps for those who prefer to make their own paleogeographic interpretations. Several projections are used-Mercator, Mollweide, and stereographic polar-to suit the various requirements of paleogeographic work.
Devonian
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Large igneous province
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Currently available Palaeozoic palaeomagnetic data from Gondwanan continents can be interpreted in terms of either (a) a migration of the pole from northern Africa to southern Africa between Ordovician and late Palaeozoic times, or (b) a rapid excursion of the pole from northern Africa to southwest of South Africa during late Ordovician to early Silurian times, followed by a return to central Africa in late Devonian times, thereafter continuing southward again. With respect to this uncertainty, pertinent stratigraphical evidence from western Gondwana includes the distribution of glacial deposits and cold-water and warm-water faunas. This record, although meagre and to some extent contradictory, appears to favour a drift history consistent with the second (b) of the APW alternatives that involves a rapid southerly excursion of the pole by early Silurian times.
Devonian
Excursion
Late Devonian extinction
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Volcanic geology is a rapidly growing research field within earth sciences. It is a research field that provides the fundamental basic data to be able to reconstruct volcanism that generated eruptive products and the sedimentary processes acted upon to redeposit and rework volcanic pyroclasts. Due to the broad time and spatial scales over which volcanism takes place, it is difficult to determine the correct link between the preserved rocks and the type of volcanism responsible for their formation. Volcanic rocks represent geological processes that occur in a distinct and rapid pattern compared to other geological processes. This book provides insight into the problem of determining the scale of volcanism and linking it to the volcanic rock record. It includes comprehensive reviews and case studies representative of volcanism in diverse geological environments. This book provides a broad overview of the problems, complexity, and usefulness of the active volcanism-based volcanic geology approach to interpreting volcanic rocks in the geological record.
Volcanology
Geologic record
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Abstract Volcanic geoheritage relates to the geological features of a region that are associated with the formation of a volcanic terrain in diverse geoenvironmental conditions. These features include the volcanic processes, volcanic landforms and/or the eruptive products of volcanism that form the geological architecture of that region. Volcanic geoheritage is expressed through the landscape and how it forms and evolves through volcanic processes on various spatio-temporal scales. In this sense it is directly linked to the processes of how magma released, transported to the surface and fragmented, the styles of eruption and accumulation of the eruptive products. Volcanic geoheritage is directly linked to the natural processes that generated them. Geocultural aspects are treated separately through volcanic geosite identification and their valorization stages. Identification of volcanic geosites, based on various valorization techniques, have been applied successfully in the past decades to many geological heritage elements. Volcanism directly impacts societal, cultural, and traditional development of communities, hence the “ living with volcanoes ” concept and indigenous aspects and knowledge about volcanism can and should play important roles in these valorization methods through co-development, transdisciplinary approaches by including interconnected scientists in discussions with local communities. Elements of volcanism and volcanic geoheritage benefit of the geoculture of society so volcanic geoheritage sites are ideal locations for community geoeducation where resilience toward volcanic hazard could be explored and applied more effectively than it is done today. Geoparks within volcanic terrains or volcanism-influenced regions should be the flagship conservation, education and tourism sites for this message. Volcanism can be an integral part of processes operating in sedimentary basins. Here volcanic eruptive products and volcanic processes contribute to the sediment fill and geological features that characterize the geoheritage of that region.
Volcanic plateau
Volcanic hazards
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Volcanology
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Synopsis Movement on the NNE-trending Coigach fault in NW Scotland can be dated by reference to the late Proterozoic Stoer and Torridon Groups which it cuts. It behaved as a normal fault in late Stoer Group time, with downthrow to the east. The fault was reactivated after the Cambrian as a listric fault with a downthrow to the west, displacing Torridon Group sediments about 5 km. Roll-over near the fault suggests that it soles out at around 8 km below present sea level. Most of the post-Cambrian movement was probably Devonian or Carboniferous. Mesozoic and later movement was negligible. Other NNE-trending faults on the mainland resemble the Coigach fault in showing large pre-Triassic displacements of the Torridon Group.
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Acritarch
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Stratigraphic and geographic distribution, systematic description, S. flexuosa, Arinskian (lower Permian), Western Australia
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