W***n
发帖数: 11530 | | W***n
发帖数: 11530 | 2
But the mountains are still there
hahaha
【在 W***n 的大作中提到】
: Oh, boy............
| W***n
发帖数: 11530 | 3
【在 W***n 的大作中提到】
:
: But the mountains are still there
: hahaha
| W***n
发帖数: 11530 | 4 8th highest peak (8064ft) in TX | W***n
发帖数: 11530 | 5 80 millions yr ago, it was still part of a sea reef | W***n
发帖数: 11530 | 6 Through millions of years, the elements of wind and rain have eroded
sediments leaving the resistant limestone of ancient reef exposed..
Geologic History
The Permian period of geologic time occurred from 251 to 299 million years
ago. The earth had already seen life diversify from simple, primitive forms
such as algae and fungi to amphibians, fishes, and insects. The earth's
surface had also been evolving and shifting. Thin plates of crust moved
constantly over the softer material below, steadily changing the position of
the continents. Through much of the early and middle Permian all of the
continents were joined together, forming the supercontinent of Pangea. Much
of modern-day New Mexico and Texas occupied the western edge of this
enormous landmass near the equator. A vast ocean surrounded Pangea, but a
narrow inlet, the Hovey Channel, connected the ocean with the Permian Basin,
an inland sea which covered parts of what is now northern Mexico and the
southwestern United States. The Permian Basin had three arms: the Marfa,
Delaware, and Midland Basins. The middle arm (the Delaware Basin) contained
the Delaware Sea which covered and area 150 miles long and 75 miles wide
over what is now Western Texas and Southeastern New Mexico.
Map of the Capitan Reef
Click on the above map for a downloadable pdf file.
During the middle part of the Permian Period a reef developed along the
margin of the Delaware Sea. This was the Capitan Reef, now recognized as one
of the most well-preserved fossil reefs in the world. For several million
years the Capitan Reef expanded and thrived along the rim of the Delaware
Basin until events altered the environment critical to its growth
approximately 260 million years ago. The outlet connecting the Permian Basin
to the ocean became restricted and the Delaware Sea began to evaporate
faster than it could be replenished. Minerals began to precipitate out of
the vanishing waters and drift to the sea floor, forming thin, alternating
bands of mineral salts and mud. Gradually, over hundreds of thousands of
years these thin bands completely filled the basin and covered the reef.
About 80 million years ago tectonic compression along the western margin of
North America caused the region encompassing west Texas and southern New
Mexico to be slowly uplifted. A transition in tectonic events 20-30 million
years ago initiated the formation of steep faults along the western side of
the Delaware Basin. Movement on these faults over the last 20 million years
caused a long-buried portion of the Capitan Reef to rise several thousand
feet above its original position. This uplifted block was then exposed to
wind and rain causing the softer overlying sediments to erode, uncovering
the more resistant fossil reef and forming the modern Guadalupe Mountains.
Today the reef towers above the desert floor as it once loomed over the
floor of the Delaware Sea 260 to 265 million years ago |
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