Abstract Anticosti Island, eastern Canada, records an exceptionally thick and well-exposed Ordovician/Silurian boundary section that hosts a series of diverse marine invertebrate faunas across the Late Ordovician mass extinction. However, base terminal stage, Hirnantian, has been difficult to identify on due lack traditional Hirnantia fauna within Upper Ellis Bay Formation. Previously, eponymou...

An anomalocaridid from the Ordovician exposes a second set of body flaps and reopens the question of how the two branches of arthropod legs evolved.

Seventeen species of marine invertebrates collected from the Upper Ordovician Waynesville Formation of southwestern Ohio were found encrusted by Cornulites, a presumed tubicolous annelid worm. Encrustation was interpreted as symbiotic in cases where the cornulitid tubes exhibited preferred orientation upon the exoskeleton of the host. This situation may reflect cornulitid utilization of feeding...

The Upper Ordovician Trenton Group of New York State is one of a number of Appalachian limestones which yields paleomagnetic poles suggesting disturbance in the late Paleozoic. Calcite fractions dissolved from samples of a 238U 206pb a e of 454+8 Ma the Trenton Limestone define g (MSWD = 12.8) in excellent agreement with 40Ar-39Ar and U-Pb ages for the deposition of the underlying Diecke Benton...

The 495 to 450 Ma Famatinian orogen, exposed throughout central and northwestern Argentina, formed from east-directed subduction under the Gondwanan margin. Sierra de Narváez Las Planchadas preserve a rare upper-crustal section of arc. New mapping, structural analysis, detrital U–Pb zircon geochronology, as well major trace element geochemistry in – are presented give comprehensive geodynamic p...

The Geirud Formation consists mainly of clastic sediments which are interbedded with limestone stringers. This rock unit is well-exposed along the Central Alborz Range in northern Iran. The Geirud Formation rests unconformably on the Mila Formation (Upper Cambrian) and is conformably overlain by the Mobarak Formation (Lower Carboniferous). This study was undertaken to determine the geologi...