Frasnian Stage

Frasnian Stage

 

the lower stage of the Upper Devonian. The Frasnian stage was identified by the Belgian geologist J. Omalius d’Halloy in 1862. At the type locality, the stage is represented by coral-reef and other limestones and by clay shales. The stage is distinguished on the basis of brachiopods, ammo-noids, and other fossils. It is divided into three (in some places, two) substages and from two to five zones. In the USSR, limestones and shales—including bituminous shales containing ammonoids and tentaculites (domanic sediments)—predominate in the Frasnian stage. In addition, brightly colored continental deposits and volcanic rocks are widespread. In many basins, the rock sequence corresponds to a marine transgression. (SeeDEVONIAN SYSTEM [PERIOD].)

References in periodicals archive ?
The die-off climaxed at the end of the period's Frasnian stage, which lasted from around 385 million to 375 million years ago.
All of the rediscovered bones originally came from a Scottish site dating back to the Frasnian stage of the late Devonian period, about 370 million years ago.