Absolute dating of the pennsylvanian period
Both the start and end of the period are marked by major extinction events.The Triassic was named in 1834 by Friedrich von Alberti, after the three distinct rock layers (tri meaning "three") that are found throughout Germany and northwestern Europe—red beds, capped by marine limestone, followed by a series of terrestrial mud- and sandstones—called the "Trias".Radiometric dating is a way of measuring the age of a piece of rock.Igneous rocks contain tiny amounts of radioactive chemicals.
When sea level rose, which it periodically did, it covered the coastal peats and created large inland muddy seas.
The world still that time was in an ice age also known as a generally cold global climate phase as a result the Pennsylvanian period was climatically zoned just like today!
It had ice on high altitudes , the equator stayed wet, and tropical, and mid altitudes stayed seasonally dry. The oceans at this time were melting from the ice age, and as they melted the water levels in oceans and rivers began to rise.
In argon-argon dating, the amounts of two forms of the element argon in a rock sample are measured using a device called a mass spectrometer.
One form only is produced by radioactive decay as the rock ages, so comparing how much there is of this in relation to the other form of argon reveals the age of the rock.