The 366 daily episodes in 2014 were chronological snapshots of earth history, beginning with the Precambrian in January and on to the Cenozoic in December. You can find them all in the index in the right sidebar. In 2015, the daily episodes for each month were assembled into monthly packages, and a few new episodes were posted. Now, the blog/podcast is on a weekly schedule with diverse topics, and the Facebook Page showcases photos on Mineral Monday and Fossil Friday. Thanks for your interest!

Wednesday, July 2, 2014

July 2. Pennsylvanian time

The Pennsylvanian or Late Carboniferous extends from the end of the Mississippian, about 318 million years ago, to the start of the Permian 299 million years ago. This short length of time, only 19 million years, is one rationale for including the Pennsylvanian and Mississippian together as one period, the Carboniferous. But, there was a lot going on and the rock record is extensive, so we’ll let it go. In any case it’s the nomenclature that is used in the US.  

Subdivisions, or ages, of the Pennsylvanian in the United States are named, from oldest to youngest, Morrowan, Atokan, Desmoinsean, Missourian, and Virgilian, each of which is represented by relatively distinct packages of rocks. Each age spanned about 6 to 8 million years. The international subdivisions of the Late Carboniferous are named for localities in Russia, where rocks of this time are well exposed. The ages are Bashkirian, Moscovian, Kasimovian, and Gzhelian, again from oldest to youngest. There isn’t a one-for-one correlation between the age names in the U.S. and in the Russian terminology, which obviously can confuse things sometimes.
—Richard I. Gibson

Time scale from Wikipedia 

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