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 an occasional schedule with diverse topics, and the Facebook Page showcases photos on Mineral Monday and Fossil Friday. Thanks for your interest!

Saturday, August 23, 2014

August 23. Permian Basin, West Texas

First, just a moment to thank you for listening to the podcast or reading the blog. I appreciate your interest and support very much. As short as these things are, it takes quite a bit of work to put them out on a daily basis, so I’m grateful to have you as an interested audience.   

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We’ll be spending the next four days in West Texas and New Mexico, where the thickest sections of Permian rocks in the world are found. They occupy a complex basin called, appropriately enough, the Permian Basin. It extends over a broad area, but the human history is focused on oil exploration, which was and is centered in Midland and Odessa, Texas. One of Odessa’s high schools is Permian High.

For much of Paleozoic time, until the Pennsylvanian Period, West Texas and New Mexico were part of the broad realm of shallow seas that covered much of western and central North America. Lots of limestones and occasional sands and shales were laid down. As we discussed last month, with the beginning of the collision of the South American corner of Gondwana, things began to get more complicated. The Marathon Fold Belt developed. In addition to the Ouachita-Marathon Mountains, some areas were also subsiding, creating large troughs for deposition. And some old lines of weakness were broken again when the Ancestral Rockies were uplifted to the northwest, in Colorado, but there may have been some impacts in West Texas too, somewhat segmenting the developing basin.

By Permian time the basin was both segmented and restricted on its margins – it was essentially two wide, relatively deep oceanic bays called the Delaware and Midland Basins. They were partially isolated from the open ocean by the rising Marathon Mountains to the south and separated from each other by a high-standing fault-bounded uplift called the Central Basin Platform, a feature with an ancient heritage that was reactivated by the compression during the Pennsylvanian continental collision. To the north and northeast of the basins was a broad shallow shelf.

The boundary between the deep basins and the shallow shelf was fairly sharp, and along parts of it, especially in the southeastern corner of what is now New Mexico and adjacent parts of Texas, a huge reef developed. We’ll talk more about that tomorrow.

The multiple phases of collision with Gondwana, to the south of the Permian Basin, resulted in at least three significant pulses of sediment distribution and subsidence in the basin. This subsidence was partly the result of the mass of sediment dumped into the basin, and partly the tectonic uplift of the margins of the basin as well as the Central Basin Platform. Taken together, they allowed for deposition of a pile of Permian rocks more than 12,000 feet thick in places.

The basin pretty much began to fill up, and parts of it became isolated from the circulation patterns of the ocean and bays, so that evaporation on a large scale took place. And we'll talk about the results of that evaporation in a few days. 

The diversity of environments in these basins also provided for the right circumstances for the preservation of organic matter that make the Permian Basin one of the most prolific producers of oil and natural gas in the world. Oil was first produced in the Permian Basin in 1921, and since then something like 30 billion barrels of oil and 80 trillion cubic feet of natural gas have been produced – and it’s not over. There has been a recent surge in production in the basin, taking total basin oil production from about 850,000 barrels per day in 2007 to about 1,400,000 barrels per day in 2014. That’s about 7% of the total U.S. oil consumption of about 20,000,000 barrels per day, and 17% of the U.S. crude oil production total, which was 8,400,000 barrels per day in May 2014.

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Georges Cuvier was born August 23, 1769, at Montbéliard, France. As a pioneering geologist, he established many of the tenets of stratigraphy, but he is probably best known for studies of comparative anatomy that laid the groundwork for the field of vertebrate paleontology. He was among the first scientists to suggest that reptiles had once dominated the earth, and he also brought the concept of extinction into the realm of scientific acceptance.
—Richard I. Gibson

References and Links
Permian Basin tectonics 

Tectonics of Central Basin Platform

Colored map from US Department of Energy (public domain)

Permian Basin province

Surge in oil production (2014) 

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