• BUREAU OF ECONOl\UC GEOLOGY THE UNIVERSITY OF TEXAS AT AUSTIN AUSTIN, TEXAS 78712 W. L. Fuaza, Director

. fl) GEOLOGIC QUADRANGLE MAP NO. 51 • '1l U'.l >< • Q) t::J 8 Geology of the Hammetts Crossing Quadrangle, Blanco, Hays, and Travis Counties, Texas

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November 1982

BUREAU OF ECONO~nc CEO!"OCY THE UNIVERSITY OF TEXAS AT AUSTIN TO ACCOMPANY MAP-GEOLOGIC BUREAU OF ECONOMIC GEOLOGY QUADRANGLE MAP NO. 51

GEOLOGY OF THE HAMMETTS CROSSING QUADRANGLE,

BLANCO, HAYS, AND TRAVIS COUNTIES, TEXAS

Virgil E. Barnes 1982

CONTENTS

General setting ...... 2 Cenozoic rocks ...... 4 Geologic formations ...... 2 Quaternary System ...... 4 Paleozoic rocks ...... 2 Pleistocene Series ...... 4 Pennsylvanian System ...... 2 Terrace deposit ...... 4 Marble Falls Limestone ...... 2 Recent Series · · · ...... 4 Smithwick Formation(?) ...... 2 Alluvium ...... 4 Mesozoic rocks ...... 3 Subsurface geology ...... 4 Cretaceous System (Lower Cretaceous) . . 3 Mineral resources ...... 6 Trinity Group ...... \ ...... 3 Construction materials ...... 6 Travis Peak Formation ...... 3 Building stone ...... 6 Sycamore Sand ...... 3 Road material ...... 6 Cow Creek Beds ...... 3 Sand and gravel ...... 6 Shingle Hills Formation ...... 3 Water ...... 6 Hensen Sand Member ...... 3 References ...... 7 Glen Rose Limestone Member . . 4 Appendix ...... 8 Bureau of Economic Geology, The University of Texas at Austin 2

GENERAL SETTING

The geology of the Hammetts Crossing quad­ occupy the remainder of the quadrangle. The rangle is shown on a U. S. Geological Survey relatively flat-lying Cretaceous rocks dip eastward 7 .5-minute topographic quadrangle map and is the about 17 feet per mile. seventeenth geologic map in the Llano region to Hammetts Crossing quadrangle is mostly within appear on a modem 1:24,000 scale, 20-foot the Pedemales River basin. The river, in incised contour interval base. The relief in the quadrangle meanders, crosses the northern part of the quad­ is about 670 feet, elevations range from 681 feet, rangle from west to east. Tributaries draining into pool level of Lake Travis, to about 1,350 feet at a Pedernales River and the Lake Travis portion of point on the divide between Pedemales River basin the river, incised in their lower reaches, include and the Barton Creek drainage area. Flat Creek and its tributaries Calahan and Hammetts Crossing quadrangle, in the Hill Sycamore Creeks, Dead Mans Hole Creek, Roy Country southeast of the Llano region, is at the Creek, Hamilton Creek, Cypress Creek, and juncture of the Llano uplift and the Ouachita numerous unnamed drainages. A small area in the structural belt. Cretaceous rocks occupy the bulk southeastern part of the quadrangle is drained by of the quadrangle. Some alluvium, one terrace Barton Creek which enters Colorado River at deposit, and a very small area of Paleozoic rocks Austin.

GEOLOGIC FORMATIONS

PALEOZOIC ROCKS Feet Inches 22. Limestone, dark gray, massively bedded, nonfossiliferous; PENNSYLVANIAN SYSTEM thin chert layers on its upper surface 6 6 Marble Falls Limestone 21. Limestone, thin bedded, black, shaly, beds 1 /a to Plummer (1950, pp. 49-50) described 410 feet 3 inches thick. In some horizons the rock resembles of Marble Falls Limestone along Battle Branch and a tough, black shale more Pedemales River mostly in the Pedernales Falls than a limestone. The quadrangle (Barnes, in press). The upper few tens thicker limestone slabs of feet of this section are in the Hammetts Crossing have a tendency to break quadrangle. The upper three intervals of Plummer's into long, rectangular blocks having "fence section, reproduced as follows, will cover all of the post" shapes, resembling Marble Falls Limestone within the Hammetts some of the layers at the Crossing quadrangle and perhaps more. top of the section in the Cherokee Valley 20 6 Feet Inches Lower Cretaceous- Smithwick Formation(?) Travis Peak Formation- 24. Conglomerate, large, well-rounded Just downstream from the foot of Pedernales cobbles in a matrix of Falls, two exposures of weathered greenish-gray coarse, red sand partially cemented with calcium shale in seepy areas were present at the time the carbonate Pedemales Falls and Hammetts Crossing quad­ Pennsylvanian- rangles were mapped. These outcrops were covered Marble Falls Group- by a gravel bar the last time I was there (May 1, 23. Limestone, dark gray, mas· 1971), but the next great flood will probably sively bedded; layers 1 to 3 feet thick with prom· expose them again. One of these outcrops is on the inent partings, mostly Hammetts Crossing quadrangle and the other is on covered by talus 21 6 the Pedemales Falls quadrangle. Geology of the Hammetts Crossing Quadrangle, Blanco, Hays, and Travis Counties, Texas 3

Although these outcrops were not positively The Cow Creek Limestone is characteristically a identified as Smithwick, they are thought to be light-colored coquinite in which many of the shells Smithwick because of the presence of a normal have been dissolved to produce a honeycombed thickness of Marble Falls Limestone and because appearance. Pebbles, common in the Cow Creek to the shale is in the position that the Smithwick the west, are scarce to the east. The Cow Creek normally occupies. However, the exposures were so Limestone grades downward to the Hammett poor that one cannot be sure that the shale has not Shale; oysters are common in the zone of transi­ slumped from the upper valley wall where tion. The upper contact with the Hensell Sand is Hammett Shale crops out. sharp. The Hammett Shale and underlying Sycamore MESOZOIC ROCKS Sand are recessive because of weathering, causing the massive Cow Creek Limestone to form cliffs CRETACEOUS SYSTEM (LOWER CRETACEOUS) 1ining Pedemales River and its tributaries. Hamilton Creek plunges over a cliff of Cow Creek Trinity Group Limestone a distance of 50 feet or more to form Hamilton Pool, a popular swimming hole. The falls Travis Peak Formation has undercut the Cow Creek at least 100 feet. Another falls at Dead Mans Hole has a 30-foot or Sycamore Sand.-The Sycamore Sand consists of so drop. a basal conglomerate overlain in most places by strata composed of various proportions of sand, Shingle Hills Formation (Barnes, 1948) silt, clay, and pebbles. In the vicinity of Pedernales Falls, the Sycamore is limited to well-cemented Hensell Sand Member.-The Hensell Sand Mem­ conglomerate and its upper surface has been bored ber in the Hammetts Crossing quadrangle forms a by marine molluscs. To the east this bored surface bench above the Cow Creek Limestone; the bench is represented by sparsely distributed bored steepens near the Glen Rose contact. The Hensell is pebbles and cobbles mostly of Ellenburger car­ composed of conglomerate in places at its base bonate rocks. These pebbles mark the boundary followed by silty and argillaceous sand grading up between the reddish-colored sediments at the top to silt and clay, in part calcareous, in the upper of the Sycamore and the overlying grayish-green­ part. However, tongues of coarser grained material weathering Hammett Shale. The conglomerate is commonly occur at various levels. One indurated composed of rocks from almost the entire pre­ conglomerate bed about 25 feet above the base of Cretaceous stratigraphic column of Central Texas, the Hensen forms a bench in the western part of and some boulders, especially those of Hickory the quadrangle and, eastward along Flat Creek, Sandstone, are more than a foot in size. grades into massive limestone. Channel deposits of Cuyler (1939, fig. 1) shows about 97 feet of coarse sand and granules are present here and Sycamore Sand at Hammetts Crossing. At the same there; one is exposed along Ranch Road No. 962 point I measured 40 feet of Sycamore from river near the entrance to Hamilton Pool. level to the bored-pebble zone. This indicates that The lower part of the Hensen is mostly red, Cuyler included 57 feet of Hammett Shale with the other colors are common, and upward the reds give Sycamore Sand. way to various shades of gray, yellowish gray, and Cow Creek Beds.-Lozo and Stricklin (1956) greenish gray. Very little Hensell is cultivated subdivided the Cow Creek Beds into Cow Creek within the quadrangle; mostly it is used for Limestone above and Hammett Shale below. They rangeland. cored about 44 feet ' of Cow Creek Limestone and Hazzard and others (1949, pl. 2) measured 45 62 feet of Hammett Shale at Hamilton Pool near feet of Hensen Sand in the vicinity of Hamilton the eastern edge of the quadrangle. Pool. This measurement is somewhat thinner than The Hammett Shale is a sandy, silty, light the roughly 60 to 80 feet shown on the geologic grayish-green-weathering clay which is medium map of the Hammetts Crossing quadrangle. The gray when fresh. Westward in a shoreward direc­ boundaries of the Hensen were traced stereo­ tion, sand is more abundant and some conglom­ scopically on aerial photographs then transferred erate is present. Oysters were collected at locality by pantograph to the Hammetts Crossing 2-19A. quadrangle scribe sheet. The Hensell thickens 4 Bureau of Economic Geology, The University of Texas at Austin

somewhat westward as bench-forming beds at the quadrangle and about 330 feet is present in the base of the Glen Rose die out westward. southeastern part. Cuyler ( 1939, p. 637) mentions finding The Glen Rose is mostly suited to ranching. In Orbitolina texana Roemer in the Hensell along general, vegetation on the Glen Rose is sparser than Pedemales River a few miles northeast of Hamilton on other units, indicating the relative sterility of its Pool. Orbitolina also occurs in the transitional zone soil. from Hensell to Glen Rose in the Spicewood The Salenia texana zone also contains abundant quadrangle (Barnes, in press). casts and molds of pelecypods and gastropods; Glen Rose Limestone Member.-The Glen Rose Porocystis and Orbitolina are common. Fossils, Limestone crops out in a broad area south of although common in several others zones within Pedernales River and in a smaller area north of the the Glen Rose Limestone, were not collected. Pedemales. The Glen Rose consists of alternating Typical Glen Rose fossils for this part of the Llano beds of limestone, dolomite, clay, silt, and sand, or region are listed in the text of the Hye quadrangle more precisely, beds composed of various propor­ (Barnes, 1965). tions and combinations of these materials. The beds vary in their resistance to erosion, producing a stairstep topography. The less easily eroded beds of CENOZOIC ROCKS limestone and dolomite form the tread of the steps and the softer less resistant beds between form the QUATERNARY SYSTEM risers. A thin fossiliferous zone near the middle of the Pleistocene Series Glen Rose has been called the Salenia texana zone by George (1947, p. 17) and Whitney (1952, Terrace deposit.- One high terrace deposit p. 66 ). The top of this zone is characterized by a resting on Cow Creek Limestone was mapped just bed containing Corbula. Where the Glen Rose is southwest of the mouth of Flat Creek. fully developed, the Corbula Bed is found near the middle of the formation. Within the northern part of the Hammetts Crossing quadrangle, approxi­ Recent Series mately 90 feet of beds crops out beneath the Corbula Bed and in the southern part approxi­ Alluvium.- Alluvium resting on Sycamore Sand mately 160 feet of Glen Rose beds is present is present along most of Pedernales River. Between beneath the Corbula Bed. alluvium and valley wall colluvium, the Sycamore Southeastward from the Llano region, the por­ Sand is poorly exposed. To better show the tion of the Glen Rose below the Corbula Bed is distribution of the Sycamore, the colluvium and composed of massive limestone which contrasts much of the alluvium are not shown. The alluvium with the thinner bedded upper part. The massive is poorly sorted ranging to boulders in size. character of the lower part of the Glen Rose is well Alluvium is present along Flat Creek and Dead displayed along Miller Creek to the southwest in Mans Hole Creek; narrow belts and patches of the Yeager Creek quadrangle (Barnes, 1967). alluvium follow many of the lesser drainages in the Up to 125 feet of Glen Rose crops out above the quadrangle but are insignificant and have not been Corbula Bed in the northwestern part of the mapped.

SUBSURFACE GEOLOGY

Gently eastward-dipping Cretaceous rocks rest quadrangle is underlain by rocks belonging to the on truncated Paleozoic rocks. Beneath the Creta­ foreland facies of the Ouachita structural belt ceous, Marble Falls Limestone dipping about 10 (Flawn and others, 1961). The boundary of fore­ degrees southeastward occupies the northwestern land facies rocks with Ouachita facies rocks in the part of the quadrangle north to northeast of subsurface grazes the southeast comer of the Pedernales Falls. The rest of the Cretaceous in the Hammetts Crossing quadrangle. Geology of the Hammetts Crossing Quadrangle, Blanco, Hays, and Travis Counties, Texas 5

The foreland facies rocks may be entirely dicate that they are within the margin of the Smithwick shale or may include other units that do structural belt. These beds may be either Stanley or not crop out in this part of the Llano region. Wells Atoka; on the basis of the X-ray determinations they that enter the foreland facies include the E. D. are tentatively identified as Atoka(?). Summerow No. 1 Reimers, the Cypress Creek X-ray data.-Mixed layer illite-montmorillonite Drilling Association No. 1 Romberg, and just east shale of foreland type. of the Hammetts Crossing quadrangle the C. R. The C. R. Franklin No. 1 B. J. Reimers well is Franklin No. 1 B. J. Reimers. Samples available east of the Hammetts Crossing quadrangle and is from these wells are in the Well Sample Library of included to give a better idea of the character of the Bureau of Economic Geology and are described the Paleozoic rocks beneath the Cretaceous in this in the appendix. area. The well is in the George Burrows Survey, The position of the Cypress Creek Drilling 1.1 miles east-southeast of Hamilton Pool, 2,000 Association No. 1 Romberg is not shown on the feet northeast of U.S. G. S. B. M. 913.8, and a few Hammetts Crossing quadrangle but according to feet southeast of a draw. The original location, 200 Sellards (1931) it is in the "Miner Survey, on feet to the south, was abandoned at about 500 Cypress Creek near Travis County line." Flawn and feet. The well spudded in Glen Rose Limestone 10 others (1961, p. 313) state that the well is also feet above the Corbula Bed and is shown on the known as .Jones No. 1 Romberg and is in the J.M. U. S. Geological Survey Shingle Hills topographic Miller Survey; it has an estimated (from topo­ map. The elevation of the derrick floor, given on graphic map) elevation of approximately 800 feet, one of the sample envelopes, is 1,008 feet. Flawn total depth of 1,560 feet, was completed in 1927, and others state that the well is in the: and entered Paleozoic rocks at a depth of 300± .. . J. C. Little Survey. Sample descriptions in the feet. They state: "Sellards (1931) reported black files of the Bureau of Economic Geology report gray shale at 834 feet. Thin section examination shows dense metamorphosed shale, dark hard gray siltstone, angular, tightly packed, fairly well-sorted, quartz and gray hard dense quartzitic sandstone. siltstone and micaceous silty shale. The rocks show The sequence is composed of very fine-grained, no metamorphism; probably they are Atoka. This angular to subround, very poorly to poorly sorted, well probably penetrated foreland rocks within the argillaceous silty quartz sandstone, locally calcareous, dark silty shale, and angular, micaceous and chloritic frontal boundary of the Ouachita Belt (Pl. 2)." The siltstone. Quartz and calcite veins are common and well is shown a little over a mile east of the Travis bituminous material is present. These rocks cannot be County comer. positively identified. Contortion, microfolding, and The position of the E. D. Summerow No. 1 incipient to very weak metamorphism indicate that Reimers likewise is not shown, but from the the sequence is within the Ouachita belt. The rocks "elevation of 800 feet (from topographic map)" are tentatively labeled Atoka(?) (See Summerow mentioned by Flawn and others (1961) it should No. 1 Reimers). be on the Hammetts Crossing quadrangle. Flawn From my description of the samples from this and others state that the well is in the J.C. Little well, my interpretation of the stratigraphy is as Survey, has total depth of 1,274 feet, was com­ follows : pleted in 1926 and 1932, and entered Paleozoic rocks at 266 feet. They state: Depth Notes in the Bureau of Economic Geology files in feet describe the sequence as dark gray shale and quartz­ Cretaceous System- ite. Sellards (1931) reported black shale. Goldstein Shingle Hills Formation- Glen Rose Limestone above Corbula Bed 0-10 (1955) reported that the first sample at 650 feet is in Glen Rose Limestone below Corbula Bed 10-115 Pennsylvanian and the last sample, 1,243 feet, is also Hensell Sand ...... 115-1 50 in Pennsylvanian; he tentatively identified the se­ Travis Peak Formation- quence as foreland fades. Cow Creek Limestone ...... 150-200 The two samples available for study are fine­ Hammett Shale ...... 200-265 grained chloritic micaceous feldspathic quartz sand­ Sycamore Sand ...... 265-467 stone and silty micaceous metashale. Identification of Pennsylvanian System ...... 467-837 this sequence is uncertain both in this well and in Franklin No. 1 Reimers immediately to the south; the Estimated thickness of Paleozoic rock units deformation noted in Franklin No. 1 Reimers and the within the Hammetts Crossing quadrangle, mostly incipient metamorphism observed in both wells in- from Barnes and Bell (1977) and Barnes (1959) 6 Bureau of Economic Geology, The University of Texas at Austin

and from the Pedemales Falls quadrangle (Barnes, gravity decreases southeastward, influenced by the in press) is tabulated as follows: presence of the Ouachita structural belt (Barnes Thickness and others, 1955 ). in feet Pennsylvanian System- Foreland facies of Ouachita structural belt including Smithwick Formation ...... 1,260± Marble Falls Limestone ...... 410± Mississippian and Devonian Systems- Barnett Formation, Chappel Limestone, Houy Formation, and Stribling Formation ...... 50± Ordovician System- Honeycut Formation ...... 650-760 Gorman Formation ...... 490-500 Tanyard Formation ...... 650-730 Cambrian System- Wilberns Formation ...... 600-650 San Saba Member ...... 440-550 Point Peak Member ...... 0-20 Morgan Creek Limestone Member ...... 130-145 Welge Sandstone Member ...... 5 Riley Formation ...... 730-770 Lion Mountain Sandstone Member ...... 40-50 Cap Mountain Limestone Member ...... 520-550 Hickory Sandstone Member ...... 160-220 Figure 1. Gravity data, Hammetts Crossing No information is available concerning the Pre­ quadrangle, Texas. Gravitational force in cambrian rocks on which the Paleozoic rocks rest; milligals (relative); dots-points of gravity gravity data are of little help (fig. 1). The value for observation.

MINERAL RESOURCES

The mineral resources of the quadrangle are sorted material up to the size of boulders and is of limited to construction materials and water. Most little value for the production of sand and gravel. of the soils, except locally on the Hensen, are not suited to agriculture. Most of the quadrangle is ranch land. WATER

CONSTRUCTION MATERIALS A ground-water survey of Blanco County was made by B. A. Barnes and Cumley (1942), one of Building stone .-It is likely that ledge stone Travis County by George and others (1941), and suitable for building is present in the Glen Rose. one of Hays County by B. A. Barnes (1938). However, such beds should be carefully checked Fourteen wells, one spring, and one oil test (1,134 for their weathering characteristics before use in feet deep) were inventoried within the Hammetts building. Crossing quadrangle. Road material.-A few of the secondary roads The wells range from 50 to 450 feet in depth within the quadrangle have been surfaced -7ith and the water at the time of the inventory stood calcareous material from the Glen Rose Limestone between 24 and 121 feet below the surface. Total and from calichified colluvial deposits. Two gravel dissolved solids ranged between 224 and 1,636 pits at the Glen Rose - Hensell contact 0.8 mile parts per million with only two wells having more northwest of Hammetts Crossing furnished than 514 parts per million. material for construction of Ranch Road 962. Data are insufficient to judge accurately where Sand and gravel.-Although alluvium is present these wells obtain water, but it is likely that eight along Pedernales River, it is composed of poorly obtain water from the Sycamore Sand, four from Geology of the Hammetts Crossing Quadrangle, Blanco, Hays, and Travis Counties, Texas 7

the Cow Creek Limestone, and two from the The Sycamore Sand is probably the best aquifer Hensen Sand. within the quadrangle, the Cow Creek Limestone will contain water in places, channels in the Hensell Follett (1973) reexamined the ground-water Sand should be water bearing, and some water is resources of Blanco County and inventoried an probably present beneath the Corbula Bed in the additional three wells within the Blanco County Glen Rose. In the Yeager Creek quadrangle portion of the Hammetts Crossing quadrangle. Of (Barnes, 1967) to the southwest, water present these, two produce from the Hensell Sand or from the Corbula Bed to 80 feet below is of good Cretaceous rocks beneath the Hensell and the other quality. Water present in the Glen Rose below this produces from the Pennsylvanian-Devonian inter­ level is mostly of poor quality. Water is likely to be val. Depths of these wells range from 120 to 400 scarce and of poor quality in foreland facies rocks feet. beneath the Cretaceous.

REFERENCES

Barnes, B. A., 1938, Records of wells and springs, drillers' Cuyler, R. H., 1939, Travis Peak Formation of Central logs, and water analyses in Hays County, Texas: Texas Texas: Am. Assoc. Petroleum Geologists Bull., v. 23, State Board of Water Engineers, 30 p. p. 625-642. ___ , and Cumley, J.C., 1942, Records of wells and Flawn, P. T., Goldstein, August, Jr., King, P. B., and springs, drillers' logs, and water analyses in Blanco Weaver, C. E., 1961, The Ouachita System: Univ. Texas County, Texas: Texas State Board of Water Engineers, Pub. 6120, 401 p. 55 p. Follett, C.R., 1973, Ground-water resources of Blanco Barnes, V. E., 1948, Ouachita facies in Central Texas: Univ. County, Texas: Texas Water Development Board, Texas, Bur. Econ. Geology Rept. Inv. No. 2, 12 p. Rept. 174, 94 p. ___ , 1959, Part 1: General discussion, in Barnes, George, W. 0., 1947, Geology and ground-water resources V. E., Cloud, P. E., Jr., Dixon, L. P., Folk, R. L., Jonas, of Comal County, Texas: Texas State Board of Water E. C., Palmer, A. R., and Tynan, E. J., Stratigraphy of Engineers, 142 p. the pre-Simpson Paleozoic subsurface rocks of Texas and ___ , Cumley, J. C., and Follett, C. R., 1941, Records southeast New Mexico: Univ. Texas, Pub. 5824, of wells and springs, drillers' logs, and water analysis in p. 11-72. Travis County, Texas: Texas State Board of Water ___ , 1965, Geology of the Hye quadrangle, Blanco, Engineers, 101 p. Gillespie, and Kendall Counties, Texas: Univ. Texas, Bur. Goldstein, August, Jr., 1955, Ouachita facies of Texas Econ. Geology Geol. Quad. Map No. 27. and Oklahoma: Tulsa Geol. Soc. Digest, v. 23, ___ , 1967, Geology of the Yeager Creek quadrangle, p. 107-115. Blanco and Hays Counties, Texas: Univ. Texas, Austin, Hazzard, R. T., Nunnally, J. D., and Feray, D. E., 1949, Bur. Econ. Geology Geol. Quad. Map No. 34. Cretaceous of Austin, Texas area: Shreveport Geo!. Soc., ___ , in press, Geology of the Pedernales Falls quad­ 17th Ann. Field Trip, Guidebook, Sept. 2-4. rangle, Blanco County, Texas: Univ. Texas, Austin, Bur. Lozo, F. E., and Stricklin, F. L., Jr., 1956, Stratigraphic Econ. Geology Geol. Quad. Map. No. 49. notes on the outcrop basal Cretaceous, Central Texas: ___ , in press, Geology of the Spicewood quadrangle, Gulf Coast Assoc. Geol. Socs. Trans., v. 6, p. 67-78. Blanco, Burnet, and Travis Counties, Texas: Univ. Texas, Plummer, F. B., 1950, The Carboniferous rocks of the Austin, Bur. Econ. Geology Geol. Quad. Map No. 50. Llano region of Central Texas: Univ. Texas Pub. 4329 ___ , and Bell, W. C., 1977, The Moore Hollow Group (Aug. 1, 1943), 170 p. of Central Texas: Univ. Texas, Austin, Bur. Econ. Sellards, E. H., 1931, Rocks underlying Cretaceous in Geology Rept. Inv. No. 88, 169 p. Balcones fault zone of Central Texas: Am. Assoc. ___ ,Romberg, F. E., and Anderson, W. A., 1955, Map Petroleum Geologists Bull., v. 15, p. 819-827. showing correlation of geologic, gravity, and magnetic Whitney, M. I., 1952, Some zone marker fossils of the Glen observations, Blanco and Gillespie Counties, Texas: Univ. Rose Formation of Central Texas: Jour. Paleontology, Texas, Bur. Econ. Geology Misc. Map No. 7. v. 26, p. 65-73. 8 Bureau of Economic Geology, The University of Texas at Austin

APPENDIX

SAMPLE DESCRIPTIONS

E. D. Summerow No. 1 Reimers Depth in Shale~lightly micaceous and silty, medium Depth in Feet gray (three samples, 1,205, 1,217, and Feet Shale-medium gray, micaceous ...... 650 1,243 feet) ...... 1,205-1,243 Shale, quartz, and quartzite?~hale , medium gray, micaceous; quartz, white; quartzite?, very fine grained, light Cypress Creek Drilling Association No. 1 Romberg to medium gray ...... 992 Shale-medium gray, micaceous ...... 1,020 Shale- dark gray and noncalcareous, very Shale, quartz, and novaculite?~hale, little clear quartz (sample not in very silty, harsh to touch, somewhat Bureau's Well Sample Library; descrip­ sandy, medium dark gray, sand up to tion from Bureau county note file) ... . . 400 1 mm, very well rounded to angular; Shale and sandstone-shale, slightly quartz, common; novaculite?, or chert? micaceous, medium gray; sandstone, very light bluish gray ...... 1,042 fine grained, highly argillaceous, Shale-very silty, harsh, medium dark gray; somewhat micaceous, medium to medium quartz and chert, scarce ...... 1,110 & 1,130 light gray ...... 680 Shale~imilar to above, some quartz veins . . 1,138 Shale-micaceous, medium gray; one frag- Shale and sandstone~hale similar to above; ment quartzite, light gray ...... 834 sandstone, very fine grained, very Sand and sandstone- both fine grained, argillaceous and silty, medium light slightly argillaceous, light olive gray gray ...... 1,140 to very light gray, sand poorly sorted, Shale, quartzite, sandstone, and chert­ angular, mostly quartz; some shale and shale similar to above, slightly sandy; sandstone similar to above ...... 912 quartzite gradational to argillaceous Sandstone, shale, and sand~andstone, very sandstone, light gray to greenish gray; fine to fine grained, slightly argilla- chert grading to novaculite, transparent ceous, very light olive gray; shale, to opaque, light bluish gray, greenish micaceous, medium to medium dark gray; gray, light olive brown, very light sand, fine to medium, mostly angular, a gray, may be conglomerate; some quartz 1,150 few coarse, well rounded grains ...... 1,075 Shale- micaceous, medium gray ...... 1,160 Sandstone, sand, and shale- sandstone, fine Shale-in part very silty, in part sandy, grained, argillaceous, very light olive medium light gray; olive chert and gray; sand, poorly sorted, very angular white quartz, common ...... 1,175 (may be mostly crushed sandstone), some Shale and sandstone~hale, micaceous medium, well rounded grains; shale, to silty to very silty and sandy ranging medium gray, scarce ...... 1,330 to argillaceous sandstone, sand very Shale- finely micaceous, medium dark gray . 1,340 angular to very well rounded, medium gray; some chips of greenish to grayish chert, some quartz ...... 1,180 C. R. Franklin No. 1 B. J. Reimers Shale- mostly silty, in part micaceous, in part sandy, medium gray ...... 1,180-1,190 Limestone and dolomite- limestone, Shale, sand, sandstone, and quartzite­ medium dark gray ooids in very fine shale and sandstone similar to above; grained, yellowish gray matrix; dolo­ quartzite, light gray; sand, very well mite, microgranular, yellowish gray, rounded to highly angular; a few chips less dolomite and some oyster shell of green and gray chert ...... 1,185 in lower sample (two samples) ...... 50-58 Shale~lightly micaceous and silty, Limestone- in part microgranular, medium gray ...... 1,190 yellowish gray, in part similar to Shale and sandstone~hale similar to above; above, in part oolitic, yellowish sandstone, in part quartzitic, very gray, in bottom sample ooids light argillaceous and silty, medium light gray; becomes dolomitic downward gray ...... 1,198 (five samples) ...... 58-85 Geology of the Hammetts Crossing Quadrangle, Blanco, Hays, and Travis Counties, Texas 9

Depth in Depth in Feet Feet

Limestone-microgranular, dolomitic, Limestone-one-third similar to above; slightly argillaceous, yellowish rest, fine grained, dolomitic, sandy, gray ...... 85-90 sand very fine, porous, light olive Limestone-similar to above except for some gray; oyster shell in bottom two very fine sand; from 95-100 feet, some samples (four samples) ...... 225-245 ooids and oyster shells; from 100-105 Limestone-very fine grained, sandy, feet, some oyster shells and consider- medium light gray to yellowish gray, able celestite ...... 90-105 abundant oyster shell (four samples) . . . . 245-265 Limestone-mostly light gray ooids in very Clay-very calcareous and dolomitic, fine grained matrix, yellowish gray, light gray with a greenish cast except some microgranular, very dolomitic, from 290 to 295 feet, yellowish gray slightly argillaceous, sandy; to light olive gray (eight samples) ...... 265-305 Orbitolina common ...... 105-110 Clay-in part similar to above; in part Limestone-microgranular, very fine sand, sandy, dolomitic, calcareous, pale slightly argillaceous, yellowish gray red ...... 305-310 to light gray ; sample mostly Siltstone-very argillaceous, sandy, some- Orbitolina ...... 110-115 what calcareous, pale red mottled Limestone- microgranular, slightly sandy greenish gray ...... 310-315 and dolomitic, some oyster shell, a Siltstone-similar to above except few Orbitolina ...... 115-120 greenish gray mottled pale red ...... 315-320 Limestone- microgranular, very dolomitic, Siltstone-sandy, sand a little coarser some very fine sand in upper sample, than above, pale red ...... 320-325 some fossil fragments and fine sand Limestone and siltstone-siltstone, very in lower sample, porous, yellowish gray . . 120-130 calcareous and sandy, mottled pale Dolomite- microgranular, some fine sand, red and greenish gray; limestone, some calcite crystals in upper sample, upper sample pale red, lower sample light olive gray (three samples) ...... 130-145 slight pinkish cast, may occur as Clay- very dolomitic, slightly sandy, light nodules in siltstone ...... 325-335 greenish gray ...... 145-150 Clay-slightly calcareous, light gray with Limestone-microgranular, slightly sandy, greenish cast ...... 337-339 vuggy, possibly originally fossil debris, Limestone-in part sandy, silty, and argilla- yellowish gray; some white limestone tn ceous, porous, white, yellowish gray , bottom sample (three samples) ...... 150-165 pale red; some siltstone ...... 339-340 Limestone-varies in grain size, appears to Siltstone, limestone, and clay-siltstone be recrystallized, vuggy, some fossil and limestone, intergradational, sandy, debris recognizable, white ...... 165-175 pale red to yellowish gray; clay, cal­ Limestone- similar to above, except careous, silty, light gray; some oyster yellowish gray (two samples) ...... 175-185 shell in middle sample (three samples) . . . 340-355 Limestone-very fine grained, Sandstone- fine grained, grains angular, very slightly dolomitic, yellowish argillaceous, silty, calcareous, gray ...... 185-190 chloritic, fossiliferous, light gray ...... 355-360 Limestone-microgranular, slightly Clay and sandstone- clay, calcareous, dolomitic, sandy, some grains pale yellowish brown; sandstone coarse, white to light gray ...... 190-195 similar to above ...... 360-365 Limestone-microgranular to very fine Limestone, siltstone, clay, and sandstone­ grained, slightly sandy and dolomitic, limestone and siltstone, intergrada- porous, very light gray ...... 195-200 tional, pale red to yellowish gray; Limestone- microgranular, sandy, sand clay, calcareous, light gray ; sand- mostly fine, angular, in part very stone similar to above ...... 365-370 well rounded, white ...... 200-205 Siltstone-very calcareous, somewhat sandy, Limestone- medium grained, sandy, sand pale red mottled yellowish gray ...... 370-375 mostly medium, coarse from 215 to 220 Clay-calcareous, silty, pale red (four feet, very porous, white (four samples) ...... 375-387 samples) ...... 205-225 10 Bureau of Economic Geology, The University of Texas at Austin

Depth in Depth in Feet Fee t

Limestone- very fine grained, light gray Sandstone-very argillaceous ranging from to yellowish gray, very fossiliferous friable to quartzitic, medium gray to including oyster shell ...... 387-390 light gray, sand mostly angular, a few Limestone- very fine grained, slightly grains well rounded ...... 585-590 sandy and dolomitic, light gray, Shale-medium dark gray, lustrous probably yellowish gray, oyster shell abundant, from slickensides ...... 590-595 fragment of shark? tooth (three Sandstone-very fine grained, argillaceous, samples) ...... 390-400 medium gray; some clay, probably Sand and limestone-sand, cavings ...... 595-630 medium-grained quartz and chert; Sandstone and shale-3-inch fragment, limestone similar to above ...... 400-405 quartzitic sandstone, fine grained, Sand, chert, limestone, and shale-mostly light gray; 1.5-inch fragment, inter­ medium to coarse sand; chert fragments crumpled quartzitic sandstone and of many types; limestone similar to lustrous shale, veined by calcite ...... 625 above; shale, greenish gray, scarce . . .. . 405-410 Sandstone and shale- material similar to Limestone, dolomite, chert, and sandstone­ that from 625 feet ...... 625-700* sandstone, fine grained, very argilla- Sandstone-one fragment, very fine grained, ceous, silty, calcareous, chloritic, argillaceous, medium dark gray, calcite light gray ; rest of material varied in veined ...... 630-632 character, probably conglomerate 410-415 Shale- medium gray, lustrous from Limestone-very fine grained to fine slickensides ...... 630-640 grained, slightly sandy to silty, Sandstone and shale-similar to above pinkish gray ...... 415-420 (three samples) ...... 640-675 Chert and limestone-mostly chert of Sandstone and shale-two 2-inch fragments, many types, some limestone, probably in part sandstone, fine grained, medium conglomerate ...... 420-430 gray, in part slickensided shale, con­ Limestone- varies in sand and silt content, torted, intermixed, veined by brilliant pale red, has somewhat the appearance black carbonaceous material and in tum of caliche (two samples) ...... 430-452 by calcite; carbonaceous material has Chert- brownish gray ...... 452-454 brown streak and some pyrite ...... 680 Chert and limestone-many types of both in Sandstone and shale-sandstone, quartzitic, various shades of dark yellow and very fine grained, very argillaceous, brown, probably conglomerate ...... 454-459 medium to light gray; shale, in part Sandstone- very argillaceous, silty, dark gray, in part greenish gray, calcareous, chloritic, some oyster shell . . 459-463 sericitic (two samples) ...... 680-690 Limestone and shale-limestone, many Sandstone, shale, and novaculite?-in inch­ varieties, some shale and oyster shell .. . . 463-465 sized fragments ; sandstone, quartzitic, Dolomite, limestone, and chert-mostly very fine to fine grained, argillaceous, Ellenburger types derived from calcite veined, medium gray to light conglomerate ...... 465-467 gray ; shale in part medium gray, lustrous Clay-silty, sandy, calcareous, pale red from slickensides, in part light gray, mottled greenish gray ...... 467-469 sericitic with a sheen, in part Clay-silty, calcareous, pale yellowish wrapped around sandstone fragments; brown (two samples) ...... 469-510 novaculite? or possibly quartzitic Clay-silty, noncalcareous, light gray 510-525 siltstone from 715 to 730 feet, one Sandstone and shale-sandstone, very fragment, calcite veined, dark fine grained, very argillaceous, in greenish gray ...... 690-730 part quartzitic, medium dark gray; Sandstone- fine grained, argillaceous, shale, dark gray, slickensides scarce calcite veined, medium gray ...... 735 (two samples) ...... 525-575 Shale-micaceous, somewhat slickensided, veined by calcite, medium light gray .... 575-585 *Footage given as labeled on sample container. Geology of the Hammetts Crossing Quadrangle, Blanco, Hays, and Travis Counties, Texas 11

Depth in Depth in Feet Feet

Sandstone and shale-in inch-sized frag­ grained, and medium grained, one piece ments; sandstone, very fine to medium fine grained, calcite veined, light grained, one coarse grained with well­ brownish gray ...... 750 rounded and poorly sorted quartz grains; Shale and sandstone-in fragments; shale, shale, one fragment, slightly sericitic, medium dark to light gray and sericitic; medium light gray ...... 740 sandstone, quartzitic, very fine Shale and sandstone-in fragments; shale, grained, highly contorted, medium gray medium gray; sandstone, mostly very fine to light gray (three samples) ...... 820-837