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Geology is a fascinating science subject

24 December 2014

At www.smithsonianmag.com/travel/when-texas-was-bottom-sea/ … is one of those imponderables. Guadelupe Peak, the highest mountain in Texas, looks across the jagged spine of El Capitan, which looks almost like the prow of a great ship rising out of the ground. The road to El Paso is in the plain below and Guadelupe Peak, and indeed, the Guadelupe Mountain range, are full of fossils. They go way back to when they were under the sea, forming part of a reef system that was some 400 miles in length.

You can argue about marine fossils of fish and nautilus in rocks representing, or not representing a prehistoric sea situation, or a great rushing burst of ocean water washing over the land – but you can't really argue about a reef. They belong beneath the waters – but not too far from land. They are definitely not the result of a tidal wave. The Guadelupes are mountains built by very small animals. In the modern world these are the corals. Whilst all limestones are not fossil reef systems – a surprising number of them are.

Modern reefs, such as surround Pacific atolls, or the Great Barrier Reef which runs along the eastern side of Australia, are communities of small animals living under the surface of the sea. However, you can't really appreciate the magnitude of these reefs – but you can get a fair idea by going to places like the Guadelupes. They rise up from a flat plain, the source of much of Texas oil wealth. The plain has been assigned a purely geological name – the Permian Plain. . This is because it goes all the way back to the Permian Period which terminated in a massive catastrophic event when many organisms died out. The Guadelupes is a coral reef that originated in the Permian.

In the modern world reefs are built largely by corals but in the Permian reefs were mostly built by sponges (or what look like sponges). These include a giant sponge that was 8 feet across. Reefs also had an association with foraminifera. Nowadays these are microscopic single celled animals covered in a shell. In the Permian they could be as much as 4 inches across – an enormous size for a single cell. Clearly things were quite different in the Permian.

In the Permian Period Texas was nearer the equator – and the sea on which the reef flourished is thought to have been an inland sea. This is forced on geologists as at this time there was a single land mass, Pangaea – surrounded by a great ocean. Hence, it is theorised the inland sea had an inlet into the great ocean – why would ocean life be represented in an inland sea, otherwise. Shortly, we are told, the inland sea actually evaporated – and the reef was covered in sediments. Most of the original reef is still buried in the ground – and the nature of the catastrophic event is passed by.

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