The geology of the MCQ includes the description of the geologic characteristics and how they are distributed over the area encompassed. The geologic map complements the description – stratigraphy, structural geology, etc. – by depicting how these characteristics are expressed within the quadrangle. As noted elsewhere, the Mountain City topographic quadrangle serves as the base map on which the geological information is superimposed.
For more complete coverage of the geology of the area, the mapping is extended some distance into some of the surrounding quads where needed to complete the geologic picture at the edges of the area.
Notes on Geologic Mapping in the MCQ and SMNQ
[In preparation]
Previous Map from the 1976 Dissertation
[In preparation]
Using LIDAR to Aid Geologic Mapping
[In preparation]
Work-in-Progress Geologic Map Segments
The geologic mapping of the MCQ for this website is intended to represent the “next generation“ of detailed mapping at a scale of 1:24,000. Portions of the area have been mapped previously by Grimshaw, 1976 (dissertation map); Smith, [TBD] (thesis map) and The UT Bureau of Economic Geology (Report of Investigation #[TBD]). This next generation is based on better aerial photographs (taken in 1958 at a scale of [TBD]) than were used previously and on enhanced understanding of fault patterns of the Balcones Fault Zone.
The geologic mapping has been done on nine segments of the quadrangle base map. The segments are 2-1/2 minute areas of the 7-1/2 minute quadrangle, which conveniently fit on 8-1/2 x 11 paper at full scale. As noted above, the geologic mapping also extends into adjacent quadrangles by varying amounts, so these adjacent segments are also included. The map segments are presented on this webpage according to the diagram shown below. The MCQ segments are shaded.
Each Tier consists of five segments that are numbered 1 to 5 from west to east. Tier 1 includes the lower 1/3 of the Signal Hill Quad above (north of) the MCQ. Tiers 2, 3 and 4 each include the three MCQ segments and a segment on the west (Dripping Springs Quad) and on the east (Buda Quad). Tier 5 covers the upper 1/3 of the San Marcos North Quad and segments of adjoining quads (Hunter and Uhland). This geologic mapping coverage is included in the companion SMNQ website.
The geology of each Segment is described below, and a link to the map and geologic description on a subsidiary webpage.
Tier 1, Segment 1 (Not Used)
[In preparation]
Tier 1, Segment 2. Signal Hill Southwest.
[In preparation. Link to child webpage. Introductory text here, with expanded narrative on webpage.]
Tier 1, Segment 3. Signal Hill South Central.
[In preparation]
Tier 1, Segment 4. Signal Hill Southeast.
[In preparation]
Tier 1, Segment 5. Oak Hill Southwest.
[In preparation]
Tier 2, Segment 1. Driftwood Northeast.
[In preparation]
Tier 2, Segment 2. Mountain City Northwest.
[In preparation]
Tier 2, Segment 3 . Mountain City North Central.
[In preparation]
Tier 2, Segment 4. Mountain City Northeast.
[Description in preparation]
Tier 2, Segment 5. Buda Northwest.
[In preparation]
Tier 3, Segment 1. Driftwood East Central.
[In preparation]
Tier 3, Segment 2. Mountain City West Central
[In preparation]
Tier 3, Segment 3. Mountain City Central
[In preparation]
Tier 3, Segment 4. Mountain City East Central.
[In preparation]
Tier 3 Segment 5. Buda West Central.
[In preparation]
Tier 4, Segment 1. Driftwood Southeast.
[In preparation]
Tier 4, Segment 2. Mountain City Southwest.
[In preparation]
Tier 4, Segment 3. Mountain City South Central.
[In preparation]
Tier 4, Segment 4. Mountain City Southeast.
[In preparation]
Tier 4, Segment 5. Buda Southwest.
[In preparation]
Tier 5 , Segments 1 to 5.
Segments 1 to 5 are in the San Marcos North quadrangle as well as the Wimberley quad to the west and the Uhland quad to the east. Click here for the geologic map segments of the San Marcos North quadrangle.