US EPA

7211364 

Journal Article 

The Devonian Period 

Becker, RT; Gradstein, FM; Hammer, O; , 

2012 

ELSEVIER SCIENCE BV 

AMSTERDAM 

GEOLOGIC TIME SCALE 2012, VOLS 1 & 2 

559-601 

10.1016/B978-0-444-59425-9.00022-6 

WOS:000368986200023 

All seven Devonian stages have been defined by GSSPs, but revisions of the base of the Emsian and of the Devonian-Carboniferous boundary are currently underway. Most of the Devonian Period was a time of exceptionally high sea-level stand and inferred widespread equable climates, but glaciations occurred immediately before its end in the south polar areas of Gondwana (South America, Central and South Africa). There is even evidence for contemporaneous mountain glaciers in tropical latitudes (in the Appalachians of eastern North America). The cold-water Malvinocaffric Province of southern Gondwana existed throughout the Early Devonian but disappeared stepwise in the Middle Devonian. Most present-day continental areas and shelves were grouped in one hemisphere, creating a giant "Proto-Pacific" or Panthalassia Ocean, whose margins are poorly preserved in allochthonous terrains. Following the tectonic events of the Caledonian orogeny of Laurasia, many "Old Red Sandstone" terrestrial deposits formed. After the closure of the narrow Rheic Ocean early in the Devonian, Eovariscan tectonic movements occurred in the Upper Devonian in the western Proto-Tethys of Europe and North Africa. Other active fold belts existed in western North America (early Antler orogeny), Polar Canada, in the Appalachians, in the Urals, along the southern margin of Siberia, in NW China, and in eastern Australia. The Devonian is the time of greatest carbonate production, with a peak of reef growth, and of the greatest diversity of marine fauna in the Paleozoic. Vascular plants became established near the end of the Middle Devonian and early in the Middle Devonian tetrapods appeared, which spread and diversified in the Upper Devonian.[GRAPHICS]. 

Gradstein, FM; Ogg, JG; Schmitz, MD; Ogg, GM;