Calymmian, Ectasian & Stenian Periods

 

Calymmian Period

There are 3 periods in the Mesoproterozoic Era. However, the article on the first of these periods, the Calymmian Period, was less than 100 words long. The Calymmian Period lasted from 1600 to 1400 million years ago. During this time, the continents expanded by adding sedimentary flatlands. Right in the middle of the period, the supercontinent Columbia started to break up.

 

Ectasian Period

The 2nd period is the Ectasian Period, which in Greek means “extension”. It lasted from 1400 to 1200 million years ago. The name refers to the continued expansion of sedimentary flatlands.

Fossils have been found dating from this period that provide the first evidence of sexual reproduction. This allowed and was necessary for complex multicellularity, in which certain cells of the organism are specialized to perform different functions.

 

Stenian Period

The Stenian Period is the final segment of the Mesoproterozoic Era, lasting from 1200 to 1000 million years ago. The supercontinent Rodinia assembled during the Stenian.

And the Keweenawan Rift formed at about 1100 million years. This rift (tear) occurred in the middle of the North American continent. I had never heard of this rift before. One wonders if North American was much skinnier before the rift occurred and the rift has been filled in since then. If that were the case, the rift could have been as small as the Mississippi River valley, or it could have stretched from the Rocky Mountain foothills to the Appalachian foothills, if those existed at that time. What would have happened if the rift had grown and deepened. Would we have 2 continents where we only have 1?

A closer look at the map provided showed it to be a lop-sided horse-shoe-shaped rift. The 2 ‘arms’ meet at Lake Superior, which defines the northern arc of the rift. The eastern arm trends south into lower Michigan, and possibly as far south as Alabama. The western arm runs southwest into Kansas and possibly as far as Oklahoma. A northern arm, which was not shown on the map, ran up into Ontario and formed another lake, but didn’t go any further.

So, let’s see, if that 3-armed rift had actually grown and spread, we might have had 3 continents where we now only have 1. That would certainly change things up. Now I have alternate histories running rampant through my mind. What do you think about that? Eastern North America, Western North America and a Mexico that reaches Lake Superior.

 

https://en.wikipedia.org/wiki/Calymmian

https://en.wikipedia.org/wiki/Ectasian

https://en.wikipedia.org/wiki/Stenian

https://en.wikipedia.org/wiki/Midcontinent_Rift_System