The Geologic History of Texas

The Geologic History of Texas - TheGeologicHistoryofTexas...

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The Geologic History of Texas   I. Introduction   Texas has rocks of every geologic age   II.  Precambrian Geologic History of Texas                Although at least two-thirds of Texas is underlain by igneous and metamorphic  rock of Precambrian age (more than 570 million years old), they are exposed in only three  relatively small locations. All are approximately the same age (1 to 1.3 billion or Grenville  age).              1) Central  Mineral  Region  (Llano   area):   Largest   exposures,  half   granite  e.g.  Enchanted Rock             2) El Paso: In the Franklin Mts.             3) Near Van Horn               These are the exposed part of the old GrenvilleMountain belt that extends from  eastern Canada to Mexico and formed at the edge of North America over 1 billion years  ago. Older rocks are expected further inland and oil wells show 1.4 billion year old rock  underlies the Texas Panhandle. 1.8 billion year old rock may also exist at depth under  Texas.   Precambrian Summary: Plate collision rocks of the Grenville belt                                     Intrusion of granites about 1 billion years ago                                     500 million years of erosion
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The Geologic History of Texas - TheGeologicHistoryofTexas...

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