Geomorphic Provinces and Regions of Texas - 2023

Hydrogeology, Geology, & Environmental Issues / Field Methods & Procedures

Ewing reported in early 2023 that Texas is a state and region with varied landforms, but they have received only limited attention. Reanalysis of geomorphic regions in Texas indicates three major provinces:

1. The Coastal Plains include plains to gentle hilly uplands constructed on poorly consolidated sediments of Late Cretaceous and Cenozoic age that dip gently toward the Gulf of Mexico, containing an important set of escarpments of Oligocene to Late Miocene resistant strata, and bounded (in North Texas) on the west by the White Rock Escarpment.
   
   
2. The Interior Plains and Plateaus include three major subgroups: those underlain mainly by limestone and dolomite, mainly of Cretaceous age (the Edwards Plateau, Stockton Dissected Plateau, Balcones Canyonlands dissected plateau, Lampasas 'Cutplain' dissected plateau, and the Grand Prairie and adjoining sandy timbered belts, with the Llano Country an anomalous inlier); those underlain by mainly elastic deposits (with evaporites and carbonates) mainly of Paleozoic and Triassic ages (Palo Pinto cuesta plain, Red Plains, Caprock Escarpment Breaks, Pecos Valley); and two high plateaus under­lain by Neogene alluvial and eolian sediment and caliche (Southern High Plains, Cimarron High Plains).
   
   
3. The Mountains and Valleys province includes some 20 mountain ranges (of volcanic, tilted fault-block, and complex character), a few plateaus, and a series of broad valleys, either bolsons or drained bolsons, mainly created by Neogene and Quaternary extension. 

UNRESOLVED QUESTIONS

As shown by the length of this brief survey, Texas has a wide diversity of geomorphic regions. Within the area are significant unresolved questions, mainly dealing with the geomorphic history of the area. Particularly significant are the following:

• What is the history of the integration of the Rio Grande and Rio Conchas? How extensive was the Neogene drainage disruption?
  
  
• The Southern High Plains plateau margin has been extensively eroded since Pliocene time; can we document ages and landscape response to this erosion? What is the role of salt dissolution in forming these sharp plateau margins?
  
  
• A broad part of the carbonate subprovince shows major streams with deeply incised meander bends; especially from the Rio Grande northeast to the Brazos River. The meanders must have formed on a much flatter surface. Neogene uplift has entrenched them and fossilized the meander patterns. Can we date this more exactly?
  
  
• The dating and correlation of the various terraces and gravels around the fringe of the Balcones escarpment and the rivers draining it is still not well understood. Uvalde gravels have been correlated nearly to the Coastal Prairie, is this a reliable correlation?
  
  
• The nearly continuous Bordas - Oakville - Catahoula escarpment is remarkable and needs further study. Parts of it are related to uplift and tilting history of the Inner Coastal Plain.

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