The Paleozoic sediments of the Chal-i-Sheh area in southwestern Iran comprising of Mila Formation, Ilebek Formation and Faraghan Formation, were studied palynologically. The samples containing well-preserved palynomorphs include acritarchs, chitinozoans, scolecodonts and pollenlspores. A palynological zonation has been established and comparison was made with other parts of the world. Based...

Introduction. Hawkins Impact Cave is the only cave in the world known to have formed inside the central uplift of a complex impact crater. Discovered in 1989 by landowner Michael Hawkins (namesake) and mapped in 2003 [1], HIC lies in the core of the central uplift of the 3.8 km diameter Flynn Creek impact structure (36˚17'N, 85˚40'W) in the Highland Rim physiographic province of north-central T...

Our perception of biodiversity in the geological past is incomplete and biased because most organisms did not have mineralized skeletons and therefore had little chance of fossilization. This especially refers to shallow-water marine environments, rarely represented by localities with exceptional preservation of fossil material (known as taphonomic windows or Konservat-Lagerstätten). Such extra...

The Ellenburger Group of the West Texas Permian Basin is part of a Lower Ordovician carbonate platform sequence that covers a large area of the United States. During the Early Ordovician, the Permian Basin area was located on the southwest edge of the Laurentia plate between 20° and 30° latitude. The equator crossed northern Canada, situating Texas in a tropical to subtropical latitude. The are...

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 (microCT). This revealed critical features of the colu...

The four most recent large mass extinction events in the Phanerozoic – the Cretaceous–Tertiary (KT), the Triassic–Jurassic (TJ), and the Permo-Triassic (PT) and Guadalupian–Tatarian (GT) doublet – are associated with a major flood basalt eruption, with the timing of peak volcanic activity corresponding within measurement uncertainties to the extinction event. Three magnetic superchrons precede ...

Oliverian Magma Series gneisses (442–454 Ma) in the cores of domes in southwestern New Hampshire have an igneous mineralogy that crystallized at pressures (P) of 9–11 kbar and temperatures (T) of 650–775 °C, whereas the cover (Ammonoosuc Volcanics) has the same formation age (453 ± 2 Ma) yet is clearly extrusive. A significant crustal section, ~30 km thick, must have originally separated the tw...

The fossil record of marine animals suggests that diversity-dependent processes exerted strong control on biodiversification: after the Ordovician Radiation, genus richness did not trend for hundreds of millions of years. However, diversity subsequently rose dramatically in the Cretaceous and Cenozoic (145 million years ago-present), indicating that limits on diversification can be overcome by ...

The annulated orthoceridans of the Middle and Late Ordovician of Baltoscandia are described and their systematic frame is revised. The revision of these nautiloids, which are part of the Orthocerida and Pseudorthocerida, is based on the investigation of characters of the septal neck, the siphuncular tube, and the apex. An unequivocal terminology of these characters is suggested and applied. The...

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...