19 Detrital-zircon analysis of sandstones interbedded with ca 464 Ma ignimbrites in 20 the lower Mweelrea Formation of the South Mayo Trough, western Ireland, 21 suggests Ordovician source-rock provenance that corresponds to two distinct 22 volcanic-arc phases on the Laurentian margin. East-derived sandstones contain a 23 suite of zircons with a mean age of ca 487 Ma that suggests derivation fr...

The Late Ordovician mass extinction (LOME) coincided with dramatic climate changes, but there are numerous ways in which these changes could have driven marine extinctions. We use a palaeobiogeographic database of rhynchonelliform brachiopods to examine the selectivity of Late Ordovician-Early Silurian genus extinctions and evaluate which extinction drivers are best supported by the data. The f...

Complete, articulated crinoids from the Ordovician peri-Gondwanan margin are rare. Here, we describe a new species, Iocrinus africanus sp. nov., from the Darriwilian-age Taddrist Formation of Morocco. The anatomy of this species was studied using a combination of traditional palaeontological methods and non-destructive X-ray micro-tomography (micro-CT). This revealed critical features of the co...

The past two decades have seen extensive analyses of the taxonomic severity of major biodiversity crises in geologic time. In contrast, we propose here an alternative analysis of the ecological severity of biodiversity crises. It is clear that the ecological impacts of the five Phanerozoic biodiversity crises were not all the same. Ranking the five Phanerozoic biodiversity crises by ecological ...

Taphonomic information is examined to evaluate the early history of connective tissues in the Crinoidea. The pattern of stalk segmentation of Middle and Late Ordovician crinoids is consistent with the two-ligament (intercolumnal and through-going ligaments) pattern present in living isocrinid crinoids and interpreted for fossil isocrinids, holocrinids, and Lower Mississippian crinoids. A single...

Following accretion of southern Siberian microcontinents to the compositions reveal up to one order of magnitude variation of some trace elements and ratios between suites, and show a progressive Siberian craton in the Early Paleozoic, five cycles of K-rich silicic magmatism, progressively decaying in volume, occurred on batholithic change in trace element concentration with decreasing age. Pla...

Introduction: More than 80 fossil meteorites have been found in a ~4 m quarry layer of mid-Ordovician limestone in Sweden [1, 2]. Their cosmic-ray exposure (CRE) ages correlate inversely with sediment deposi-tion age and indicate very rapid (<1.2 Myrs) transport from the asteroid belt [3]. The same layer contains up to 3 sediment-dispersed, extraterrestrial chromite (SEC) grains (>63 µm) per kg...