Upper Ordovician

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Upper Ordovician

[′əp·ər ‚ȯr·də′vish·ən]
(geology)
The latest epoch of the Ordovician period of geologic time, beginning approximately 440 million years ago.
References in periodicals archive ?
The encrustation of both Middle Ordovician and Late Ordovician trilobites took place post mortem, because during the life the inner surface of the pygidium and cranidium was not exposed to encrustation and was in contact with soft tissues of the trilobite.
1) a study titled "A volcanic trigger for the Late Ordovician mass extinction?
This paper focuses on a relatively quiet interval from Late Ordovician (Ashgill) to Late Silurian times when an enormous volume of sediment eroded from post-Middle Ordovician highlands was deposited in extensive basins on the Ganderian composite plate.
The Sr isotopic evolution curve in the Late Ordovician Lianglitage Formation sedimentary period was established by combining the Sr isotope data of Bachu reported by Zhao, 2013 and that of Central Tarim reported by Liu et al.
The convergence of Baltica with the Avalonia microcontinent started in the Late Ordovician and might have affected the water exchange of the Baltic Basin with the ocean.
Although it has long been agreed that the so-called Late Ordovician mass extinction-which occurred about 450 million years ago-was related to climate change, exactly how the climate change produced the extinction has not been known.
The limestone layers in which you found your specimen were formed in shallow water during the Late Ordovician Period, about 450 million years ago.
The paper by Alvaro and Van Vliet-Lanoe focuses on the crucial Late Ordovician interval, when evidence of Hirnantian glaciation is widespread in northern Gondwana.
Many papers discus the controlling mechanisms that may have forced major climate change, such as geographical and oceanographic changes during the Late Ordovician or changing ocean gateways in the Cenozoic, while others discuss biological and chemical proxies that can be used to track ancient climate change, such as the use of Ca/Mg ratio of foraminifer tests or alkenones from surface- dwelling marine-algae.
The Kardla crater on Hiiumaa Island, NW Estonia, is a well-preserved 4 km wide and 500 m deep Late Ordovician (455 Ma) complex impact structure (Puura & Suuroja 1992; Ainsaar et al.
Tracing the Origin of the Late Ordovician Deicke, Millbrig and Kinnekulle K-Bentonites
Middle Ordovician 464-449 Late Ordovician 449-439 Early Silurian 439-424 Late Silurian 424-409