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!

Thursday, August 28, 2014

August 28. Cimmerian continent

I hope you remember Tethys, the huge triangular-shaped bay in the eastern side of Pangaea after Gondwana had collided with North America and Europe. The Tethys coast of Gondwana extended from the connected North Africa, to Arabia, to India, to Australia. But not quite the modern margins of those continents.  

The Cimmerian Continent as it rifted away from the Gondwana portion of Pangaea in Late Permian time, about 250-260 million years ago. See below for source.

There was a long, linear zone along that Tethyan shore that was attached to Gondwana at the start of Permian time, but by sometime in Late Permian time, the zone began to rift away from Gondwana. Technically the ocean was the Paleo-Tethys, the confusing ocean we talked about August 5, and the rifting we are talking about today created a new ocean, Neo-Tethys or just plain Tethys. Visualize this something like East Africa today, where the East African Rift system is breaking a zone away from the core of Africa, and will open up a new ocean in the process. The ocean has already started, in the Red Sea between Africa and Arabia, which were formerly part and parcel with each other. The ocean will eventually split East Africa away from the main part of Africa, with a narrow continent drifting across the Indian Ocean, and a new, narrow ocean forming between it and Africa.

That’s what was happening in Late Permian time in the northeastern part of Gondwana. The narrow strip that rifted away wasn’t necessarily uniformly long and narrow – and for sure it didn’t stay that way. Individual blocks, much like Madagascar today, drifted more or less in tandem, but not necessarily as a continuous, connected continent. Those blocks ultimately became what we know today as Turkey, Iran, Afghanistan, probably several blocks that make up Tibet, and some bits of Indochina and Malaya. Taken together, these blocks are called the Cimmerian Continent, or Cimmeria.

It’s possible that the continental fragments that comprise the Iberian and Italian Peninsulas today originated in a similar manner to Cimmeria, but they did have a different history and were becoming amalgamated to Europe earlier. It is likely, however, that the Carpathian Mountains in Romania and nearby have a heritage related to a Cimmerian block, as do parts of the Caucasus. The Cimmerians were an ancient people living north of the Black Sea and Caucasus Mountains, areas affected by the Cimmerian Orogeny.

After the Cimmerian blocks finished their drift across the Paleo-Tethys Ocean, they collided with the southern margin of Eurasia, creating mountain uplifts and the Cimmerian Orogeny, and closing the Paleo-Tethys Ocean while opening the Neo-Tethys Ocean. Those collisions would not occur for many millions of years after the rifting began during the Permian, so we’ll talk about them later in the year.
—Richard I. Gibson

Cimmeride Orogenic System

Tethys globe view from PhD thesis of Pierre Dèzes (1999; Institut de Mineralogie et Petrographie, Université de Lausanne) from via Wikimedia commons 

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