- Usage in publication:
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- Zesch formation*
- Modifications:
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- Named
- Dominant lithology:
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- Limestone
- AAPG geologic province:
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- Llano uplift
Summary:
Pg. 128 (fig. 2), 137 (fig. 7), 138-139. Zesch formation. [Name proposed for the uppermost of four known formations of Devonian rocks in central Texas.] Is a thin, highly siliceous limestone and leached silica rock containing a few species of brachiopods; brownish to yellowish and contains angular fragments of chert. About 18 to 24 inches thick; thins to feather edge. Rests on older Devonian strata (Bear Spring formation, new) and is collapsed into middle Ellenburger strata (Gorman formation); appears to grade upward into chert breccia here assigned to Ives breccia. [Occurs along the southwestern margin of an ancient collapse structure on the Roy Zesch Ranch (also = type locality of Bear Spring formation). Age range of Zesch uncertain. Shown on correlation chart separated from underlying Bear Spring formation by a "hiatus" representing perhaps all of the Givetian (late Middle Devonian) and earliest Frasnian (early Late Devonian) time. Separated from overlying rocks by a hiatus that includes the late Frasnian and all of Fammenian (Late Devonian) time.] Age is Late(?) Devonian. [Report includes geologic maps, correlation chart. Fossils (brachiopods, echinoids) listed.]
Type locality and derivation of name: Roy Zesch Ranch, Mason Co., TX.
Source: US geologic names lexicon (USGS Bull. 1200, p. 4337-4338); supplemental information (in brackets) from GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
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- Zesch formationâ€
- Modifications:
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- Abandoned
Summary:
Pg. 811. Term abandoned. [Zesch formation of Barnes and others (1947, p. 137-139) is] partial synonym for the Ives breccia member of Houy formation (new).
Source: US geologic names lexicon (USGS Bull. 1200, p. 4337-4338).
- Usage in publication:
-
- Zesch Formation
- Modifications:
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- Reinstated
- AAPG geologic province:
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- Llano uplift
Summary:
Reinstated and assigned to the Middle Devonian Tioughniogo Stage. Was formerly suppressed in favor of the Ives Breccia Member of the Houy Formation by Cloud, Barnes, and Hass (1957). Is excluded from the Houy Formation in this report. Overlies Bear Spring Formation; underlies unnamed limestone. Conodonts listed. Geologic map. Found in central TX on the Llano uplift.
Source: GNU records (USGS DDS-6; Denver GNULEX).
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
Asterisk (*) indicates published by U.S. Geological Survey authors.
"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).
Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).