I hesitate to repeat myself, however, to the best of my knowledge the Fredricksburg is not permeable sandstone, it is LIMESTONE:
The Fredericksburg Stage was named for exposures in the outskirts of Fredericksburg,
STRATIGRAPHIC UNITS OF LOWER ALBIAN CENTRAL TEXAS
Sharon Goehring GEOL 344: Evolutionary Stratigraphy
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Gillespie County, Texas. First described by R. T. Hill in 1887, the Fredericksburg is composed of
limestones with some flints and chalk units. It strikes northeast to southwest and dips toward the
southeast at a gradient of nine to sixteen meters per kilometer (Petta, 1977).
I believe the Anona Zone is a sandstone. It is higher in the litho column. This is facies geology, when the shallow inland seas were full, limestones were produced, as they dried up the muds and shales were produced, as the littoral (beach environment) disappeared you got sandstones and various continental non aqauous based basin deposits. You know some the environments are very dry because you get lots of salt domes in Texas. Oiljob
Then the process can all repeat.
