Dispersed microfossils (spores and phytodebris) provide the earliest evidence for land plants. They are first reported from the Llanvirn (Mid-Ordovician). More or less identical assemblages occur from the Llanvirn (Mid-Ordovician) to the late Llandovery (Early Silurian), suggesting a period of relative stasis some 40 Myr in duration. Various lines of evidence suggest that these early dispersed ...

misson on Ordovician Stratigraphy and in 2002 ratified by the International Commission on Stratigraphy as the GSSP of the Second (Upper) Stage of the Lower Ordovician, is located on the Hunneberg Mountain in southwestern Sweden. The stratigraphic succession represents an outer shelf environment near the Baltic Shield margin. The shale-dominated, biostratigraphically complete, richly fossilifero...

Establishing the timescale of early land plant evolution is essential for testing hypotheses on the coevolution of land plants and Earth's System. The sparseness of early land plant megafossils and stratigraphic controls on their distribution make the fossil record an unreliable guide, leaving only the molecular clock. However, the application of molecular clock methodology is challenged by the...

This report of a severely injured trilobite from the Middle Ordovician (~465 Ma) accords with a number of similar observations of healed lesions observed in trilobites. The uniqueness of the specimen described here is that the character of the repair-mechanisms is reflected by the secondarily built structures, which form the new surface of the ruptured compound eye. Smooth, repaired areas insid...

Beecher's Trilobite Bed in the Frankfort Shale of New York State preserves an exceptional record of the benthic macrofauna of a Late Ordovician deepwater marine environment. It has long been famous for specimens of the trilobites Triarthrus eatoni (Hall), Cryptolithus bellulus (Ulrich), Primaspis crosotus (Locke), and Cornuproetus beecheri (Ruedemann), new combination, which preserve the ventra...

Gamma-ray bursts (hereafter GRB) produce a flux of radiation detectable across the observable Universe. A GRB within our own galaxy could do considerable damage to the Earth's biosphere; rate estimates suggest that a dangerously near GRB should occur on average two or more times per billion years. At least five times in the history of life, the Earth experienced mass extinctions that eliminated...

By comparison with the relatively diverse Early Ordovician cephalopod faunas that lived in association with the low latitude carbonate platforms (e.g. Laurentia [Flower 1964]; Siberia [Balashov 1961]; China [Chen 1976]), those of the high latitude margins of Gondwana are of relatively low diversity, generally poorly known, and where known, often in need of revision. Of those high latitudinal as...

Strike-slip deformation belts are interesting structures in the crust and of significance petroleum exploration. The Shunbei 5 fault belt (SB5), a long strike-slip Tarim Basin, played an important role formation recently discovered major oilfield known as oilfield. In this study, models plan view vertical profile were established to interpret SB5 with multi-cycled tectonic activities. To end, i...

Abstract The Ordovician of North and West Africa comprises three main transgressive–regressive sequences understood as ‘second-order’ cycles 10–15 myr duration. Tide- to wave-dominated shallow-marine clastic successions, preserving incidental bryozoan carbonates the north, include fluvial deposits over most proximal southern stretches platform. boundary with Cambrian strata remains unclear but ...

New palaeogeographical reconstructions for the earlier Ordovician (480 Ma), and later (450 Ma) integrate revised longitude-calibrated palaeomagnetic inclusion of synthetic plate margins within now-vanished oceanic areas. There are substantial published differences from previous placing some continents terranes in Asia; example, Siberia Gondwana have previously been placed at varied distances re...