Ostracod crustaceans are the most abundant fossil arthropods and are characterized by a long stratigraphic range. However, their soft parts are very rarely preserved, and the presence of ostracods in rocks older than the Silurian period [1-5] was hitherto based on the occurrence of their supposed shells. Pyritized ostracods that preserve limbs and in situ embryos, including an egg within an ova...

As a test of the utility of magnetic susceptibility (MS) measurements for correlation among lithified marine sequences, samples were collected from well-studied shale and limestone outcrops of the Upper Ordovician Kope Formation, northern Kentucky. The bulk (initial) low-field MS of these samples is compared among two lithoand biostratigraphically correlated sections containing the same beds. T...

BACKGROUND Sphaerexochinae is a speciose and widely distributed group of cheirurid trilobites. Their temporal range extends from the earliest Ordovician through the Silurian, and they survived the end Ordovician mass extinction event (the second largest mass extinction in Earth history). Prior to this study, the individual evolutionary relationships within the group had yet to be determined uti...

Ordovician trilobites are reviewed based on a new species-level relational database. The stratigraphical ranges of all 56 families with occurrences in the Ordovician are documented and the content, phylogenetic status, diversity and Ordovician distribution by major palaeocontinent/terrane are discussed. Aspects of higher classification are also dealt with. Global sampling is heavily biased towa...

The Gucheng region is oil and gas accumulation area of Tarim Basin，dominated by beach controlled lithologic reservoirs，which has superior conditions broad exploration prospects. lower Paleozoic strata in the are Carboniferous, Ordovician, Cambrian systems from top to bottom. Silurian, Devonian, Permian missing. Ordovician – main target layers area. There four reservoirs: group, Yingshan Penglai...

The catastrophic disruption of the L chondrite parent body in the asteroid belt c. 470 Ma initiated a prolonged meteorite bombardment of Earth that started in the Ordovician and continues today. Abundant L chondrite meteorites in Middle Ordovician strata have been interpreted to be the consequence of the asteroid breakup event. Here we report a zircon U-Pb date of 467.50±0.28 Ma from a distinct...

Calcareous skeletons evolved as part of the greater Ediacaran/Cambrian diversification of marine animals; however, skeletons did not become permanent, globally important sources of carbonate sediment until the Ordovician radiation. Representative carbonate facies in a Series 3 Cambrian to Tremadocian succession from western Newfoundland and Ordovician successions from the Ibex area, Utah, show ...