Results 191 to 200 of about 29,816 (231)

Anomalous geomagnetic field during the late Ordovician

Nature, 1976
MEASUREMENTS of the Lower Palaeozoic magnetic field in the British Isles1 show that it changed from around D=355°, I=−50° to D=20°, I=−54° (corresponding to an apparent shift of the south palaeomagnetic pole from 0° W to 35 °W along the present Equator) between Ordovician and Devonian times. Following unpublished work by W. E. Tremlett and J. C. Briden,
C. THOMAS, J. C. BRIDEN
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Late Ordovician global warming—The Boda event

Geology, 2005
There is substantial evidence for mid-Ashgillian global warming before the latest Ordovician Hirnantian glaciation, as shown by the movement of previously lower latitude benthic faunas such as trilobites and brachiopods to progressively higher latitudes and by an increase in endemic faunas at low latitudes.
Richard A. Fortey, L. Robin M. Cocks
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The Late Ordovician glacial record

2008
An outline of the North Gondwanan, Late Ordovician glacial record is proposed. The related palaeogeographic domain extended from southern high palaeo-latitudes (southeastern Mauritania, Niger) to northern lower palaeo-latitudes (Morocco, Turkey, Sardinia) and covered a more than 4000 km-wide section perpendicular to ice-flow lines. Glacial advances are
Ghienne, Jean-François, Loi, Alfredo, Paris, Florentin, Rubino, Jean-Loup   +3 more
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Aplacophoran traits in the late Ordovician septemchitonid polyplacophorans

Journal of Morphology
Abstract A sample of phosphatized, originally calcareous, mollusk shells from the Katian age uppermost Mójcza Limestone at its type locality yielded a few hundred polyplacophoran plates. The chelodids are very rare among them. Three septemchitonid species dominate.
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The Late Ordovician Biogeochemical Carbon Cycle

2014
The isotopic composition of the carbonate carbon (δ13Ccarb) is one of the best tools for understanding the biogeochemical carbon cycle through Earth history. δ13Ccarb is also used to chemostratigraphically correlate coeval strata. This dissertation has three main foci that all utilize δ13Ccarb as the common data type.
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"Rules of Assembly" for Two Late Ordovician Communities

PALAIOS, 1986
The logic that organic communities are little more than collections of species thrown together as accidents of space and time somehow seems less convincing when viewed over long spans of geologic time. We suggest that the apparent chaos of individualism results more from the intrinsic design of short-term ecological surveys, and that weak competitive ...
Peter W. Bretsky, Susan M. Klofak
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The Late Ordovician Wufengian Sediments and the Ordovician‐Silurian Boundary in Western Zhejiang Province

Acta Geologica Sinica-English, 1987
Abstract The Late Ordovician Wufengian sediments in western Zhejiang include three facies: 1) graptolite shale facies, composed of two parts— the upper part the Yankou Formation, with the Diplograptus bohemicus (graptolite) zone and Dalmanitina sp. (trilobite), and the lower part the yuqian Formation with four graptolite zones: (4) the Paraorthograptus
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Ordovician-Late Silurian geodynamics of north Queensland

2016
Palaeozoic continental growth and accretionary tectonism along the eastern margin of Gondwana is characterised by the inversion of back-arc basins and accretion of the magmatic arc terranes and micro-continental ribbons.
Armit, Robin, Betts, Peter, STEWART, JOHN   +2 more
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Morphometry of Late Ordovician Microbial Borings: ABSTRACT

AAPG Bulletin, 1980
Microborings within Late Ordovician shells of the brachiopod Raphinesquina alternata from the Tanner Creek Formation, Richmond Group, of southeastern Indiana, were studied by scanning electron microscopy of their resin casts. The shells have been exposed to microbial boring in quiet and illuminated waters below the wave base and then buried with ...
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Possible Late Ordovician Glaciation of Nova Scotia

Canadian Journal of Earth Sciences, 1972
A thin, poorly stratified, polymictic diamictite at the the base of the White Rock Formation (perhaps Caradocian or younger) contains unsorted, clustered, faceted, and grooved clasts apparently dropped into a shaly or sandy lithotope. Ice probably transported these stones from a distant source.
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