The Permian and Cretaceous Aquifer Systems of Far West Texas

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The Permian and Cretaceous Aquifer Systems of Far
West Texas

• Matthew M. Uliana, Ph.D., P.G.
• Geology Program and Aquatic Resources (Dept. of
  Biology)

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Talk Outline

• Introduction
• Paleozoic depositional setting
• Aquifers in Paleozoic rocks
• Marathon, Capitan, Rustler, Bone Springs
• Cretaceous depositional setting
• Aquifers in Cretaceous rocks
• Edwards-Trinity (Plateau) aquifer
• Regional flow systems
• Structural controls on groundwater flow

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Aquifers of West Texas
Bone Springs-Victorio Peak
Rustler
Capitan
Edwards-Trinity (Plateau)
Marathon
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Paleozoic Depositional Settings

• Permian
• Area was on the edge of a major super-continent
  called Pangea
• Basin surrounded by a large reef system
• Aquifers include
• Marathon
• Capitan
• Rustler
• Bone Springs-Victorio Peak Aquifers

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Marathon Aquifer

• Located in Brewster County north of Big Bend
• Ordovician to Pennsylvanian age (500 300
  million years ago)
• Located in the Marathon Uplift
• Water found in fractures and cavities in
  subsurface
• Not particularly productive

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Capitan Aquifer

• Occurs in the Capitan Reef Complex
• Ancient reef which formed around the margins of
  the Delaware Basin in the Permian Period (250
  million years ago)
• algae, sponges, and tiny colonial animals called
  bryozoans
• Excellent exposure of the reef in Guadalupe
  Mountains National Park
• El Capitan

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Flow under Apache Mts.

• Flow through the Apache Mts. Area is not in the
  reef complex rocks
• Flow is in the basin sediments
• Probably controlled by fractures

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Rustler Aquifer

• Permian also associated with the Delaware Basin
• Evaporites (gypsum and anhydrite)
• Formed when the basin closed and dried up

Great Salt Lake
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Rustler Water Quality

• Well yields are generally low
• Controlled by fractures
• Quite variable
• Usually high in sulfates
• Rarely good enough for regular human consumption

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Bone Springs-Victorio Peak

• Located in the Dell City area
• Limestone deposited between the reef and the
  continent
• Controlled by fractures
• Recharge comes from New Mexico
• Primarily from the Sacramento River

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Cretaceous Depositional Settings

• Much of North America was covered by shallow
  tropical sea for millions of years
• Lots of limestone deposited throughout Texas
• Most of the Cretaceous aquifers in Texas are in
  limestone

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Edwards-Trinity Plateau

• Cretaceous limestones
• Only westernmost part is in the Trans-Pecos
• Hydraulically-connected to the Cenozoic Pecos
  Alluvial Aquifer

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Regional Flow Systems

• Connections between different aquifers
• Some can cover dozens to hundreds of miles
• Controlled by several factors

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Structural Controls

• The tectonic events of the past billion years
  created structural grains in the regional bedrock
• Creates patterns of fractures that control
  groundwater flow paths
• Examples include
• Permian carbonates in Apache Mts.
• Otero Mesa in New Mexico/ Hudspeth County

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Conclusions

• Paleozoic aquifers in far west Texas are
  considered minor aquifers
• Aquifer properties
• Location, flow paths, permeability, water quality
• are generally controlled by the depositional
  setting and the regional structural trends