نتایج جستجو برای: upper ordovician

تعداد نتایج: 206538  

2009
Björn Kröger Thomas Servais Yunbai Zhang

BACKGROUND During the Ordovician the global diversity increased dramatically at family, genus and species levels. Partially the diversification is explained by an increased nutrient, and phytoplankton availability in the open water. Cephalopods are among the top predators of today's open oceans. Their Ordovician occurrences, diversity evolution and abundance pattern potentially provides informa...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2016
Luis A Buatois Maria G Mángano Ricardo A Olea Mark A Wilson

Contrasts between the Cambrian Explosion (CE) and the Great Ordovician Biodiversification Event (GOBE) have long been recognized. Whereas the vast majority of body plans were established as a result of the CE, taxonomic increases during the GOBE were manifested at lower taxonomic levels. Assessing changes of ichnodiversity and ichnodisparity as a result of these two evolutionary events may shed...

Journal: :International Journal of Earth Sciences 2022

Abstract Although much is known about the Ordovician tectonics of South European Variscides, aspects their geodynamic evolution and palaeogeographic reconstruction remain uncertain. In Sardinia, Variscan tectonic units include significant vestiges evolution, such as a fold system that affected only Cambrian–Lower successions, are cut by regional angular unconformity. A comparison stratigraphy s...

2007
Dongwoo Suk Rob Van der Voo

. Early to middle Paleozoic arbonates ofeastern North America have been pervasively remagnetized. In order to determine the process of remagnetization, scanning and scanning transmission electron microscopy have been used to characterize magnetite in thin sections and in concentrated separates. Samples included Ordovician Knox carbonates from east Tennessee, Ordovician Trenton limestone and Dev...

Journal: :Australian Journal of Earth Sciences 2021

The provenance of the upper Cambrian to Upper Ordovician sedimentary rocks Tasmania and Waratah Bay in southern Victoria provides information about complex dynamic tectonic environment present during their deposition. This paper uses U–Pb detrital zircon data constrain stratigraphic comparisons reconstructions these rock sequences. Multivariate statistics are used investigate similarity between...

2004
DAIDU FAN CONGXIAN LI PING WANG

Tonglu rhythmites (Upper Ordovician) in Zhejiang Province, east-central China, display three orders of cyclicity in sandstone and mudstone layer thickness. Millimeter-thick alternations of sandstone and mudstone laminae are ascribed to single tidal cycles. Centimeter-thick alternations of sand-dominated layers (SDLs) and muddominated layers (MDLs) are interpreted to be related to alternation of...

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