359.2 – 318 MILLION: MISSISSIPPIAN

• • • • Epoch opens in slow mass extinction, life soon recovers, the age of  amphibians;
      • Euramerica & Gondwana continue to merge; much mountain building; other continent fragments drift closer;
      • Vast forests and swamps form as sea levels fluctuate;
      • Climate hot & humid but glaciated at the poles
      • Oxygen level 40% above today – abundant wildfires
      • amphibious tetrapods multiply wildly; many grow enormous in the high humidity and oxygen;
      • Sea life dominated by sharks, corals, bryozoa,brachiopods, ammonoids, crinoids and foraminifera;
      • much of the world’s coal formed in the Carboniferous
      • Carboniferous Period lasted from about 359.2 to 299 million years ago.

Name	Diameter (km)	Age (megayears)	Dating method	Morphological type	Notes
Crooked Creek, Missouri	~7	~348 – 323	Geological dating	CONFIRMED Complex	Serial impact event?
Charlevoix, Quebec	54	342 ± 15	K-Ar	CONFIRMED Peak ring	Elevated Earthquake Zone
Weaubleau, Missouri	19	320 – 340	Geological dating	PROBABLE Complex	Ring-like drainages