Karst Features

Shelf Margin Karst
West Texas Permian

Linear karst collapse structures occur along the Permian San Andres shelf margin in Waddell Field, West Texas.
G3 and G4 are high frequency sequences in the Lower San Andres. The top of G4 is a regional unconformity and bypass surface between the Lower San Andres and Upper San Andres on the Central Basin Platform.




Hydrologic Model


When fresh water is mixed with sea water, the ability of the mixture to dissolve CaCO3 is enhanced (Plummer 1975).
The mixing zone is related to the position of the meteoric water table and the paleo shoreline. Caves are concentrated at the fresh water/sea water mixing zone interface.
Caves tend to be elongated along principal directions of water flow, including joints and fractures.
In the Bahamas, large dissolution voids, called flank margin caves, form preferentially along the margin of the discharging freshwater lens as a result of freshwater/saltwater mixing (Mylroie and Carew, 1990).

Mylroie J. E., and J. L. Carew, 1990, The flank margin model for dissolution cave development in carbonate platforms: Earth Surface Processes and Landforms, v. 15, p. 413-424.
Plummer L. N., 1975, Mixing of sea water with calcium carbonate ground water, In: Whitten, E. H. T. (Ed.), Quantitative studies in geological sciences, Geological Society of America Memoir 142, p. 219-236.


Last Modified November 2006